1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-1996, 1998-2012 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.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
24 @c readline appendices use @vindex, @findex and @ftable,
25 @c annotate.texi and gdbmi use @findex.
29 @c !!set GDB manual's edition---not the same as GDB version!
30 @c This is updated by GNU Press.
33 @c !!set GDB edit command default editor
36 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
38 @c This is a dir.info fragment to support semi-automated addition of
39 @c manuals to an info tree.
40 @dircategory Software development
42 * Gdb: (gdb). The GNU debugger.
46 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
47 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
48 Free Software Foundation, Inc.
50 Permission is granted to copy, distribute and/or modify this document
51 under the terms of the GNU Free Documentation License, Version 1.3 or
52 any later version published by the Free Software Foundation; with the
53 Invariant Sections being ``Free Software'' and ``Free Software Needs
54 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
55 and with the Back-Cover Texts as in (a) below.
57 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
58 this GNU Manual. Buying copies from GNU Press supports the FSF in
59 developing GNU and promoting software freedom.''
63 This file documents the @sc{gnu} debugger @value{GDBN}.
65 This is the @value{EDITION} Edition, of @cite{Debugging with
66 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
67 @ifset VERSION_PACKAGE
68 @value{VERSION_PACKAGE}
70 Version @value{GDBVN}.
76 @title Debugging with @value{GDBN}
77 @subtitle The @sc{gnu} Source-Level Debugger
79 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
80 @ifset VERSION_PACKAGE
82 @subtitle @value{VERSION_PACKAGE}
84 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
88 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
89 \hfill {\it Debugging with @value{GDBN}}\par
90 \hfill \TeX{}info \texinfoversion\par
94 @vskip 0pt plus 1filll
95 Published by the Free Software Foundation @*
96 51 Franklin Street, Fifth Floor,
97 Boston, MA 02110-1301, USA@*
98 ISBN 978-0-9831592-3-0 @*
105 @node Top, Summary, (dir), (dir)
107 @top Debugging with @value{GDBN}
109 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
111 This is the @value{EDITION} Edition, for @value{GDBN}
112 @ifset VERSION_PACKAGE
113 @value{VERSION_PACKAGE}
115 Version @value{GDBVN}.
117 Copyright (C) 1988-2010 Free Software Foundation, Inc.
119 This edition of the GDB manual is dedicated to the memory of Fred
120 Fish. Fred was a long-standing contributor to GDB and to Free
121 software in general. We will miss him.
124 * Summary:: Summary of @value{GDBN}
125 * Sample Session:: A sample @value{GDBN} session
127 * Invocation:: Getting in and out of @value{GDBN}
128 * Commands:: @value{GDBN} commands
129 * Running:: Running programs under @value{GDBN}
130 * Stopping:: Stopping and continuing
131 * Reverse Execution:: Running programs backward
132 * Process Record and Replay:: Recording inferior's execution and replaying it
133 * Stack:: Examining the stack
134 * Source:: Examining source files
135 * Data:: Examining data
136 * Optimized Code:: Debugging optimized code
137 * Macros:: Preprocessor Macros
138 * Tracepoints:: Debugging remote targets non-intrusively
139 * Overlays:: Debugging programs that use overlays
141 * Languages:: Using @value{GDBN} with different languages
143 * Symbols:: Examining the symbol table
144 * Altering:: Altering execution
145 * GDB Files:: @value{GDBN} files
146 * Targets:: Specifying a debugging target
147 * Remote Debugging:: Debugging remote programs
148 * Configurations:: Configuration-specific information
149 * Controlling GDB:: Controlling @value{GDBN}
150 * Extending GDB:: Extending @value{GDBN}
151 * Interpreters:: Command Interpreters
152 * TUI:: @value{GDBN} Text User Interface
153 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
154 * GDB/MI:: @value{GDBN}'s Machine Interface.
155 * Annotations:: @value{GDBN}'s annotation interface.
156 * JIT Interface:: Using the JIT debugging interface.
158 * GDB Bugs:: Reporting bugs in @value{GDBN}
160 @ifset SYSTEM_READLINE
161 * Command Line Editing: (rluserman). Command Line Editing
162 * Using History Interactively: (history). Using History Interactively
164 @ifclear SYSTEM_READLINE
165 * Command Line Editing:: Command Line Editing
166 * Using History Interactively:: Using History Interactively
168 * In Memoriam:: In Memoriam
169 * Formatting Documentation:: How to format and print @value{GDBN} documentation
170 * Installing GDB:: Installing GDB
171 * Maintenance Commands:: Maintenance Commands
172 * Remote Protocol:: GDB Remote Serial Protocol
173 * Agent Expressions:: The GDB Agent Expression Mechanism
174 * Target Descriptions:: How targets can describe themselves to
176 * Operating System Information:: Getting additional information from
178 * Trace File Format:: GDB trace file format
179 * Index Section Format:: .gdb_index section format
180 * Copying:: GNU General Public License says
181 how you can copy and share GDB
182 * GNU Free Documentation License:: The license for this documentation
191 @unnumbered Summary of @value{GDBN}
193 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
194 going on ``inside'' another program while it executes---or what another
195 program was doing at the moment it crashed.
197 @value{GDBN} can do four main kinds of things (plus other things in support of
198 these) to help you catch bugs in the act:
202 Start your program, specifying anything that might affect its behavior.
205 Make your program stop on specified conditions.
208 Examine what has happened, when your program has stopped.
211 Change things in your program, so you can experiment with correcting the
212 effects of one bug and go on to learn about another.
215 You can use @value{GDBN} to debug programs written in C and C@t{++}.
216 For more information, see @ref{Supported Languages,,Supported Languages}.
217 For more information, see @ref{C,,C and C++}.
219 Support for D is partial. For information on D, see
223 Support for Modula-2 is partial. For information on Modula-2, see
224 @ref{Modula-2,,Modula-2}.
226 Support for OpenCL C is partial. For information on OpenCL C, see
227 @ref{OpenCL C,,OpenCL C}.
230 Debugging Pascal programs which use sets, subranges, file variables, or
231 nested functions does not currently work. @value{GDBN} does not support
232 entering expressions, printing values, or similar features using Pascal
236 @value{GDBN} can be used to debug programs written in Fortran, although
237 it may be necessary to refer to some variables with a trailing
240 @value{GDBN} can be used to debug programs written in Objective-C,
241 using either the Apple/NeXT or the GNU Objective-C runtime.
244 * Free Software:: Freely redistributable software
245 * Contributors:: Contributors to GDB
249 @unnumberedsec Free Software
251 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
252 General Public License
253 (GPL). The GPL gives you the freedom to copy or adapt a licensed
254 program---but every person getting a copy also gets with it the
255 freedom to modify that copy (which means that they must get access to
256 the source code), and the freedom to distribute further copies.
257 Typical software companies use copyrights to limit your freedoms; the
258 Free Software Foundation uses the GPL to preserve these freedoms.
260 Fundamentally, the General Public License is a license which says that
261 you have these freedoms and that you cannot take these freedoms away
264 @unnumberedsec Free Software Needs Free Documentation
266 The biggest deficiency in the free software community today is not in
267 the software---it is the lack of good free documentation that we can
268 include with the free software. Many of our most important
269 programs do not come with free reference manuals and free introductory
270 texts. Documentation is an essential part of any software package;
271 when an important free software package does not come with a free
272 manual and a free tutorial, that is a major gap. We have many such
275 Consider Perl, for instance. The tutorial manuals that people
276 normally use are non-free. How did this come about? Because the
277 authors of those manuals published them with restrictive terms---no
278 copying, no modification, source files not available---which exclude
279 them from the free software world.
281 That wasn't the first time this sort of thing happened, and it was far
282 from the last. Many times we have heard a GNU user eagerly describe a
283 manual that he is writing, his intended contribution to the community,
284 only to learn that he had ruined everything by signing a publication
285 contract to make it non-free.
287 Free documentation, like free software, is a matter of freedom, not
288 price. The problem with the non-free manual is not that publishers
289 charge a price for printed copies---that in itself is fine. (The Free
290 Software Foundation sells printed copies of manuals, too.) The
291 problem is the restrictions on the use of the manual. Free manuals
292 are available in source code form, and give you permission to copy and
293 modify. Non-free manuals do not allow this.
295 The criteria of freedom for a free manual are roughly the same as for
296 free software. Redistribution (including the normal kinds of
297 commercial redistribution) must be permitted, so that the manual can
298 accompany every copy of the program, both on-line and on paper.
300 Permission for modification of the technical content is crucial too.
301 When people modify the software, adding or changing features, if they
302 are conscientious they will change the manual too---so they can
303 provide accurate and clear documentation for the modified program. A
304 manual that leaves you no choice but to write a new manual to document
305 a changed version of the program is not really available to our
308 Some kinds of limits on the way modification is handled are
309 acceptable. For example, requirements to preserve the original
310 author's copyright notice, the distribution terms, or the list of
311 authors, are ok. It is also no problem to require modified versions
312 to include notice that they were modified. Even entire sections that
313 may not be deleted or changed are acceptable, as long as they deal
314 with nontechnical topics (like this one). These kinds of restrictions
315 are acceptable because they don't obstruct the community's normal use
318 However, it must be possible to modify all the @emph{technical}
319 content of the manual, and then distribute the result in all the usual
320 media, through all the usual channels. Otherwise, the restrictions
321 obstruct the use of the manual, it is not free, and we need another
322 manual to replace it.
324 Please spread the word about this issue. Our community continues to
325 lose manuals to proprietary publishing. If we spread the word that
326 free software needs free reference manuals and free tutorials, perhaps
327 the next person who wants to contribute by writing documentation will
328 realize, before it is too late, that only free manuals contribute to
329 the free software community.
331 If you are writing documentation, please insist on publishing it under
332 the GNU Free Documentation License or another free documentation
333 license. Remember that this decision requires your approval---you
334 don't have to let the publisher decide. Some commercial publishers
335 will use a free license if you insist, but they will not propose the
336 option; it is up to you to raise the issue and say firmly that this is
337 what you want. If the publisher you are dealing with refuses, please
338 try other publishers. If you're not sure whether a proposed license
339 is free, write to @email{licensing@@gnu.org}.
341 You can encourage commercial publishers to sell more free, copylefted
342 manuals and tutorials by buying them, and particularly by buying
343 copies from the publishers that paid for their writing or for major
344 improvements. Meanwhile, try to avoid buying non-free documentation
345 at all. Check the distribution terms of a manual before you buy it,
346 and insist that whoever seeks your business must respect your freedom.
347 Check the history of the book, and try to reward the publishers that
348 have paid or pay the authors to work on it.
350 The Free Software Foundation maintains a list of free documentation
351 published by other publishers, at
352 @url{http://www.fsf.org/doc/other-free-books.html}.
355 @unnumberedsec Contributors to @value{GDBN}
357 Richard Stallman was the original author of @value{GDBN}, and of many
358 other @sc{gnu} programs. Many others have contributed to its
359 development. This section attempts to credit major contributors. One
360 of the virtues of free software is that everyone is free to contribute
361 to it; with regret, we cannot actually acknowledge everyone here. The
362 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
363 blow-by-blow account.
365 Changes much prior to version 2.0 are lost in the mists of time.
368 @emph{Plea:} Additions to this section are particularly welcome. If you
369 or your friends (or enemies, to be evenhanded) have been unfairly
370 omitted from this list, we would like to add your names!
373 So that they may not regard their many labors as thankless, we
374 particularly thank those who shepherded @value{GDBN} through major
376 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
377 Jim Blandy (release 4.18);
378 Jason Molenda (release 4.17);
379 Stan Shebs (release 4.14);
380 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
381 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
382 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
383 Jim Kingdon (releases 3.5, 3.4, and 3.3);
384 and Randy Smith (releases 3.2, 3.1, and 3.0).
386 Richard Stallman, assisted at various times by Peter TerMaat, Chris
387 Hanson, and Richard Mlynarik, handled releases through 2.8.
389 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
390 in @value{GDBN}, with significant additional contributions from Per
391 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
392 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
393 much general update work leading to release 3.0).
395 @value{GDBN} uses the BFD subroutine library to examine multiple
396 object-file formats; BFD was a joint project of David V.
397 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
399 David Johnson wrote the original COFF support; Pace Willison did
400 the original support for encapsulated COFF.
402 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
404 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
405 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
407 Jean-Daniel Fekete contributed Sun 386i support.
408 Chris Hanson improved the HP9000 support.
409 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
410 David Johnson contributed Encore Umax support.
411 Jyrki Kuoppala contributed Altos 3068 support.
412 Jeff Law contributed HP PA and SOM support.
413 Keith Packard contributed NS32K support.
414 Doug Rabson contributed Acorn Risc Machine support.
415 Bob Rusk contributed Harris Nighthawk CX-UX support.
416 Chris Smith contributed Convex support (and Fortran debugging).
417 Jonathan Stone contributed Pyramid support.
418 Michael Tiemann contributed SPARC support.
419 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
420 Pace Willison contributed Intel 386 support.
421 Jay Vosburgh contributed Symmetry support.
422 Marko Mlinar contributed OpenRISC 1000 support.
424 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
426 Rich Schaefer and Peter Schauer helped with support of SunOS shared
429 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
430 about several machine instruction sets.
432 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
433 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
434 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
435 and RDI targets, respectively.
437 Brian Fox is the author of the readline libraries providing
438 command-line editing and command history.
440 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
441 Modula-2 support, and contributed the Languages chapter of this manual.
443 Fred Fish wrote most of the support for Unix System Vr4.
444 He also enhanced the command-completion support to cover C@t{++} overloaded
447 Hitachi America (now Renesas America), Ltd. sponsored the support for
448 H8/300, H8/500, and Super-H processors.
450 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
452 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
455 Toshiba sponsored the support for the TX39 Mips processor.
457 Matsushita sponsored the support for the MN10200 and MN10300 processors.
459 Fujitsu sponsored the support for SPARClite and FR30 processors.
461 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
464 Michael Snyder added support for tracepoints.
466 Stu Grossman wrote gdbserver.
468 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
469 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
471 The following people at the Hewlett-Packard Company contributed
472 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
473 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
474 compiler, and the Text User Interface (nee Terminal User Interface):
475 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
476 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
477 provided HP-specific information in this manual.
479 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
480 Robert Hoehne made significant contributions to the DJGPP port.
482 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
483 development since 1991. Cygnus engineers who have worked on @value{GDBN}
484 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
485 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
486 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
487 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
488 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
489 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
490 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
491 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
492 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
493 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
494 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
495 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
496 Zuhn have made contributions both large and small.
498 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
499 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
501 Jim Blandy added support for preprocessor macros, while working for Red
504 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
505 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
506 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
507 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
508 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
509 with the migration of old architectures to this new framework.
511 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
512 unwinder framework, this consisting of a fresh new design featuring
513 frame IDs, independent frame sniffers, and the sentinel frame. Mark
514 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
515 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
516 trad unwinders. The architecture-specific changes, each involving a
517 complete rewrite of the architecture's frame code, were carried out by
518 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
519 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
520 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
521 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
524 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
525 Tensilica, Inc.@: contributed support for Xtensa processors. Others
526 who have worked on the Xtensa port of @value{GDBN} in the past include
527 Steve Tjiang, John Newlin, and Scott Foehner.
529 Michael Eager and staff of Xilinx, Inc., contributed support for the
530 Xilinx MicroBlaze architecture.
533 @chapter A Sample @value{GDBN} Session
535 You can use this manual at your leisure to read all about @value{GDBN}.
536 However, a handful of commands are enough to get started using the
537 debugger. This chapter illustrates those commands.
540 In this sample session, we emphasize user input like this: @b{input},
541 to make it easier to pick out from the surrounding output.
544 @c FIXME: this example may not be appropriate for some configs, where
545 @c FIXME...primary interest is in remote use.
547 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
548 processor) exhibits the following bug: sometimes, when we change its
549 quote strings from the default, the commands used to capture one macro
550 definition within another stop working. In the following short @code{m4}
551 session, we define a macro @code{foo} which expands to @code{0000}; we
552 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
553 same thing. However, when we change the open quote string to
554 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
555 procedure fails to define a new synonym @code{baz}:
564 @b{define(bar,defn(`foo'))}
568 @b{changequote(<QUOTE>,<UNQUOTE>)}
570 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
573 m4: End of input: 0: fatal error: EOF in string
577 Let us use @value{GDBN} to try to see what is going on.
580 $ @b{@value{GDBP} m4}
581 @c FIXME: this falsifies the exact text played out, to permit smallbook
582 @c FIXME... format to come out better.
583 @value{GDBN} is free software and you are welcome to distribute copies
584 of it under certain conditions; type "show copying" to see
586 There is absolutely no warranty for @value{GDBN}; type "show warranty"
589 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
594 @value{GDBN} reads only enough symbol data to know where to find the
595 rest when needed; as a result, the first prompt comes up very quickly.
596 We now tell @value{GDBN} to use a narrower display width than usual, so
597 that examples fit in this manual.
600 (@value{GDBP}) @b{set width 70}
604 We need to see how the @code{m4} built-in @code{changequote} works.
605 Having looked at the source, we know the relevant subroutine is
606 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
607 @code{break} command.
610 (@value{GDBP}) @b{break m4_changequote}
611 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
615 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
616 control; as long as control does not reach the @code{m4_changequote}
617 subroutine, the program runs as usual:
620 (@value{GDBP}) @b{run}
621 Starting program: /work/Editorial/gdb/gnu/m4/m4
629 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
630 suspends execution of @code{m4}, displaying information about the
631 context where it stops.
634 @b{changequote(<QUOTE>,<UNQUOTE>)}
636 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
638 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
642 Now we use the command @code{n} (@code{next}) to advance execution to
643 the next line of the current function.
647 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
652 @code{set_quotes} looks like a promising subroutine. We can go into it
653 by using the command @code{s} (@code{step}) instead of @code{next}.
654 @code{step} goes to the next line to be executed in @emph{any}
655 subroutine, so it steps into @code{set_quotes}.
659 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
661 530 if (lquote != def_lquote)
665 The display that shows the subroutine where @code{m4} is now
666 suspended (and its arguments) is called a stack frame display. It
667 shows a summary of the stack. We can use the @code{backtrace}
668 command (which can also be spelled @code{bt}), to see where we are
669 in the stack as a whole: the @code{backtrace} command displays a
670 stack frame for each active subroutine.
673 (@value{GDBP}) @b{bt}
674 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
676 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
678 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
679 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
681 #4 0x79dc in expand_input () at macro.c:40
682 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
686 We step through a few more lines to see what happens. The first two
687 times, we can use @samp{s}; the next two times we use @code{n} to avoid
688 falling into the @code{xstrdup} subroutine.
692 0x3b5c 532 if (rquote != def_rquote)
694 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
695 def_lquote : xstrdup(lq);
697 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
700 538 len_lquote = strlen(rquote);
704 The last line displayed looks a little odd; we can examine the variables
705 @code{lquote} and @code{rquote} to see if they are in fact the new left
706 and right quotes we specified. We use the command @code{p}
707 (@code{print}) to see their values.
710 (@value{GDBP}) @b{p lquote}
711 $1 = 0x35d40 "<QUOTE>"
712 (@value{GDBP}) @b{p rquote}
713 $2 = 0x35d50 "<UNQUOTE>"
717 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
718 To look at some context, we can display ten lines of source
719 surrounding the current line with the @code{l} (@code{list}) command.
725 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
727 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
730 538 len_lquote = strlen(rquote);
731 539 len_rquote = strlen(lquote);
738 Let us step past the two lines that set @code{len_lquote} and
739 @code{len_rquote}, and then examine the values of those variables.
743 539 len_rquote = strlen(lquote);
746 (@value{GDBP}) @b{p len_lquote}
748 (@value{GDBP}) @b{p len_rquote}
753 That certainly looks wrong, assuming @code{len_lquote} and
754 @code{len_rquote} are meant to be the lengths of @code{lquote} and
755 @code{rquote} respectively. We can set them to better values using
756 the @code{p} command, since it can print the value of
757 any expression---and that expression can include subroutine calls and
761 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
763 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
768 Is that enough to fix the problem of using the new quotes with the
769 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
770 executing with the @code{c} (@code{continue}) command, and then try the
771 example that caused trouble initially:
777 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
784 Success! The new quotes now work just as well as the default ones. The
785 problem seems to have been just the two typos defining the wrong
786 lengths. We allow @code{m4} exit by giving it an EOF as input:
790 Program exited normally.
794 The message @samp{Program exited normally.} is from @value{GDBN}; it
795 indicates @code{m4} has finished executing. We can end our @value{GDBN}
796 session with the @value{GDBN} @code{quit} command.
799 (@value{GDBP}) @b{quit}
803 @chapter Getting In and Out of @value{GDBN}
805 This chapter discusses how to start @value{GDBN}, and how to get out of it.
809 type @samp{@value{GDBP}} to start @value{GDBN}.
811 type @kbd{quit} or @kbd{Ctrl-d} to exit.
815 * Invoking GDB:: How to start @value{GDBN}
816 * Quitting GDB:: How to quit @value{GDBN}
817 * Shell Commands:: How to use shell commands inside @value{GDBN}
818 * Logging Output:: How to log @value{GDBN}'s output to a file
822 @section Invoking @value{GDBN}
824 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
825 @value{GDBN} reads commands from the terminal until you tell it to exit.
827 You can also run @code{@value{GDBP}} with a variety of arguments and options,
828 to specify more of your debugging environment at the outset.
830 The command-line options described here are designed
831 to cover a variety of situations; in some environments, some of these
832 options may effectively be unavailable.
834 The most usual way to start @value{GDBN} is with one argument,
835 specifying an executable program:
838 @value{GDBP} @var{program}
842 You can also start with both an executable program and a core file
846 @value{GDBP} @var{program} @var{core}
849 You can, instead, specify a process ID as a second argument, if you want
850 to debug a running process:
853 @value{GDBP} @var{program} 1234
857 would attach @value{GDBN} to process @code{1234} (unless you also have a file
858 named @file{1234}; @value{GDBN} does check for a core file first).
860 Taking advantage of the second command-line argument requires a fairly
861 complete operating system; when you use @value{GDBN} as a remote
862 debugger attached to a bare board, there may not be any notion of
863 ``process'', and there is often no way to get a core dump. @value{GDBN}
864 will warn you if it is unable to attach or to read core dumps.
866 You can optionally have @code{@value{GDBP}} pass any arguments after the
867 executable file to the inferior using @code{--args}. This option stops
870 @value{GDBP} --args gcc -O2 -c foo.c
872 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
873 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
875 You can run @code{@value{GDBP}} without printing the front material, which describes
876 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
883 You can further control how @value{GDBN} starts up by using command-line
884 options. @value{GDBN} itself can remind you of the options available.
894 to display all available options and briefly describe their use
895 (@samp{@value{GDBP} -h} is a shorter equivalent).
897 All options and command line arguments you give are processed
898 in sequential order. The order makes a difference when the
899 @samp{-x} option is used.
903 * File Options:: Choosing files
904 * Mode Options:: Choosing modes
905 * Startup:: What @value{GDBN} does during startup
909 @subsection Choosing Files
911 When @value{GDBN} starts, it reads any arguments other than options as
912 specifying an executable file and core file (or process ID). This is
913 the same as if the arguments were specified by the @samp{-se} and
914 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
915 first argument that does not have an associated option flag as
916 equivalent to the @samp{-se} option followed by that argument; and the
917 second argument that does not have an associated option flag, if any, as
918 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
919 If the second argument begins with a decimal digit, @value{GDBN} will
920 first attempt to attach to it as a process, and if that fails, attempt
921 to open it as a corefile. If you have a corefile whose name begins with
922 a digit, you can prevent @value{GDBN} from treating it as a pid by
923 prefixing it with @file{./}, e.g.@: @file{./12345}.
925 If @value{GDBN} has not been configured to included core file support,
926 such as for most embedded targets, then it will complain about a second
927 argument and ignore it.
929 Many options have both long and short forms; both are shown in the
930 following list. @value{GDBN} also recognizes the long forms if you truncate
931 them, so long as enough of the option is present to be unambiguous.
932 (If you prefer, you can flag option arguments with @samp{--} rather
933 than @samp{-}, though we illustrate the more usual convention.)
935 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
936 @c way, both those who look for -foo and --foo in the index, will find
940 @item -symbols @var{file}
942 @cindex @code{--symbols}
944 Read symbol table from file @var{file}.
946 @item -exec @var{file}
948 @cindex @code{--exec}
950 Use file @var{file} as the executable file to execute when appropriate,
951 and for examining pure data in conjunction with a core dump.
955 Read symbol table from file @var{file} and use it as the executable
958 @item -core @var{file}
960 @cindex @code{--core}
962 Use file @var{file} as a core dump to examine.
964 @item -pid @var{number}
965 @itemx -p @var{number}
968 Connect to process ID @var{number}, as with the @code{attach} command.
970 @item -command @var{file}
972 @cindex @code{--command}
974 Execute commands from file @var{file}. The contents of this file is
975 evaluated exactly as the @code{source} command would.
976 @xref{Command Files,, Command files}.
978 @item -eval-command @var{command}
979 @itemx -ex @var{command}
980 @cindex @code{--eval-command}
982 Execute a single @value{GDBN} command.
984 This option may be used multiple times to call multiple commands. It may
985 also be interleaved with @samp{-command} as required.
988 @value{GDBP} -ex 'target sim' -ex 'load' \
989 -x setbreakpoints -ex 'run' a.out
992 @item -directory @var{directory}
993 @itemx -d @var{directory}
994 @cindex @code{--directory}
996 Add @var{directory} to the path to search for source and script files.
1000 @cindex @code{--readnow}
1002 Read each symbol file's entire symbol table immediately, rather than
1003 the default, which is to read it incrementally as it is needed.
1004 This makes startup slower, but makes future operations faster.
1009 @subsection Choosing Modes
1011 You can run @value{GDBN} in various alternative modes---for example, in
1012 batch mode or quiet mode.
1019 Do not execute commands found in any initialization files. Normally,
1020 @value{GDBN} executes the commands in these files after all the command
1021 options and arguments have been processed. @xref{Command Files,,Command
1027 @cindex @code{--quiet}
1028 @cindex @code{--silent}
1030 ``Quiet''. Do not print the introductory and copyright messages. These
1031 messages are also suppressed in batch mode.
1034 @cindex @code{--batch}
1035 Run in batch mode. Exit with status @code{0} after processing all the
1036 command files specified with @samp{-x} (and all commands from
1037 initialization files, if not inhibited with @samp{-n}). Exit with
1038 nonzero status if an error occurs in executing the @value{GDBN} commands
1039 in the command files. Batch mode also disables pagination, sets unlimited
1040 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1041 off} were in effect (@pxref{Messages/Warnings}).
1043 Batch mode may be useful for running @value{GDBN} as a filter, for
1044 example to download and run a program on another computer; in order to
1045 make this more useful, the message
1048 Program exited normally.
1052 (which is ordinarily issued whenever a program running under
1053 @value{GDBN} control terminates) is not issued when running in batch
1057 @cindex @code{--batch-silent}
1058 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1059 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1060 unaffected). This is much quieter than @samp{-silent} and would be useless
1061 for an interactive session.
1063 This is particularly useful when using targets that give @samp{Loading section}
1064 messages, for example.
1066 Note that targets that give their output via @value{GDBN}, as opposed to
1067 writing directly to @code{stdout}, will also be made silent.
1069 @item -return-child-result
1070 @cindex @code{--return-child-result}
1071 The return code from @value{GDBN} will be the return code from the child
1072 process (the process being debugged), with the following exceptions:
1076 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1077 internal error. In this case the exit code is the same as it would have been
1078 without @samp{-return-child-result}.
1080 The user quits with an explicit value. E.g., @samp{quit 1}.
1082 The child process never runs, or is not allowed to terminate, in which case
1083 the exit code will be -1.
1086 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1087 when @value{GDBN} is being used as a remote program loader or simulator
1092 @cindex @code{--nowindows}
1094 ``No windows''. If @value{GDBN} comes with a graphical user interface
1095 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1096 interface. If no GUI is available, this option has no effect.
1100 @cindex @code{--windows}
1102 If @value{GDBN} includes a GUI, then this option requires it to be
1105 @item -cd @var{directory}
1107 Run @value{GDBN} using @var{directory} as its working directory,
1108 instead of the current directory.
1110 @item -data-directory @var{directory}
1111 @cindex @code{--data-directory}
1112 Run @value{GDBN} using @var{directory} as its data directory.
1113 The data directory is where @value{GDBN} searches for its
1114 auxiliary files. @xref{Data Files}.
1118 @cindex @code{--fullname}
1120 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1121 subprocess. It tells @value{GDBN} to output the full file name and line
1122 number in a standard, recognizable fashion each time a stack frame is
1123 displayed (which includes each time your program stops). This
1124 recognizable format looks like two @samp{\032} characters, followed by
1125 the file name, line number and character position separated by colons,
1126 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1127 @samp{\032} characters as a signal to display the source code for the
1131 @cindex @code{--epoch}
1132 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1133 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1134 routines so as to allow Epoch to display values of expressions in a
1137 @item -annotate @var{level}
1138 @cindex @code{--annotate}
1139 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1140 effect is identical to using @samp{set annotate @var{level}}
1141 (@pxref{Annotations}). The annotation @var{level} controls how much
1142 information @value{GDBN} prints together with its prompt, values of
1143 expressions, source lines, and other types of output. Level 0 is the
1144 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1145 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1146 that control @value{GDBN}, and level 2 has been deprecated.
1148 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1152 @cindex @code{--args}
1153 Change interpretation of command line so that arguments following the
1154 executable file are passed as command line arguments to the inferior.
1155 This option stops option processing.
1157 @item -baud @var{bps}
1159 @cindex @code{--baud}
1161 Set the line speed (baud rate or bits per second) of any serial
1162 interface used by @value{GDBN} for remote debugging.
1164 @item -l @var{timeout}
1166 Set the timeout (in seconds) of any communication used by @value{GDBN}
1167 for remote debugging.
1169 @item -tty @var{device}
1170 @itemx -t @var{device}
1171 @cindex @code{--tty}
1173 Run using @var{device} for your program's standard input and output.
1174 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1176 @c resolve the situation of these eventually
1178 @cindex @code{--tui}
1179 Activate the @dfn{Text User Interface} when starting. The Text User
1180 Interface manages several text windows on the terminal, showing
1181 source, assembly, registers and @value{GDBN} command outputs
1182 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1183 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1184 Using @value{GDBN} under @sc{gnu} Emacs}).
1187 @c @cindex @code{--xdb}
1188 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1189 @c For information, see the file @file{xdb_trans.html}, which is usually
1190 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1193 @item -interpreter @var{interp}
1194 @cindex @code{--interpreter}
1195 Use the interpreter @var{interp} for interface with the controlling
1196 program or device. This option is meant to be set by programs which
1197 communicate with @value{GDBN} using it as a back end.
1198 @xref{Interpreters, , Command Interpreters}.
1200 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1201 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1202 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1203 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1204 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1205 @sc{gdb/mi} interfaces are no longer supported.
1208 @cindex @code{--write}
1209 Open the executable and core files for both reading and writing. This
1210 is equivalent to the @samp{set write on} command inside @value{GDBN}
1214 @cindex @code{--statistics}
1215 This option causes @value{GDBN} to print statistics about time and
1216 memory usage after it completes each command and returns to the prompt.
1219 @cindex @code{--version}
1220 This option causes @value{GDBN} to print its version number and
1221 no-warranty blurb, and exit.
1226 @subsection What @value{GDBN} Does During Startup
1227 @cindex @value{GDBN} startup
1229 Here's the description of what @value{GDBN} does during session startup:
1233 Sets up the command interpreter as specified by the command line
1234 (@pxref{Mode Options, interpreter}).
1238 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1239 used when building @value{GDBN}; @pxref{System-wide configuration,
1240 ,System-wide configuration and settings}) and executes all the commands in
1244 Reads the init file (if any) in your home directory@footnote{On
1245 DOS/Windows systems, the home directory is the one pointed to by the
1246 @code{HOME} environment variable.} and executes all the commands in
1250 Processes command line options and operands.
1253 Reads and executes the commands from init file (if any) in the current
1254 working directory. This is only done if the current directory is
1255 different from your home directory. Thus, you can have more than one
1256 init file, one generic in your home directory, and another, specific
1257 to the program you are debugging, in the directory where you invoke
1261 If the command line specified a program to debug, or a process to
1262 attach to, or a core file, @value{GDBN} loads any auto-loaded
1263 scripts provided for the program or for its loaded shared libraries.
1264 @xref{Auto-loading}.
1266 If you wish to disable the auto-loading during startup,
1267 you must do something like the following:
1270 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1273 The following does not work because the auto-loading is turned off too late:
1276 $ gdb -ex "set auto-load-scripts off" myprogram
1280 Reads command files specified by the @samp{-x} option. @xref{Command
1281 Files}, for more details about @value{GDBN} command files.
1284 Reads the command history recorded in the @dfn{history file}.
1285 @xref{Command History}, for more details about the command history and the
1286 files where @value{GDBN} records it.
1289 Init files use the same syntax as @dfn{command files} (@pxref{Command
1290 Files}) and are processed by @value{GDBN} in the same way. The init
1291 file in your home directory can set options (such as @samp{set
1292 complaints}) that affect subsequent processing of command line options
1293 and operands. Init files are not executed if you use the @samp{-nx}
1294 option (@pxref{Mode Options, ,Choosing Modes}).
1296 To display the list of init files loaded by gdb at startup, you
1297 can use @kbd{gdb --help}.
1299 @cindex init file name
1300 @cindex @file{.gdbinit}
1301 @cindex @file{gdb.ini}
1302 The @value{GDBN} init files are normally called @file{.gdbinit}.
1303 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1304 the limitations of file names imposed by DOS filesystems. The Windows
1305 ports of @value{GDBN} use the standard name, but if they find a
1306 @file{gdb.ini} file, they warn you about that and suggest to rename
1307 the file to the standard name.
1311 @section Quitting @value{GDBN}
1312 @cindex exiting @value{GDBN}
1313 @cindex leaving @value{GDBN}
1316 @kindex quit @r{[}@var{expression}@r{]}
1317 @kindex q @r{(@code{quit})}
1318 @item quit @r{[}@var{expression}@r{]}
1320 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1321 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1322 do not supply @var{expression}, @value{GDBN} will terminate normally;
1323 otherwise it will terminate using the result of @var{expression} as the
1328 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1329 terminates the action of any @value{GDBN} command that is in progress and
1330 returns to @value{GDBN} command level. It is safe to type the interrupt
1331 character at any time because @value{GDBN} does not allow it to take effect
1332 until a time when it is safe.
1334 If you have been using @value{GDBN} to control an attached process or
1335 device, you can release it with the @code{detach} command
1336 (@pxref{Attach, ,Debugging an Already-running Process}).
1338 @node Shell Commands
1339 @section Shell Commands
1341 If you need to execute occasional shell commands during your
1342 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1343 just use the @code{shell} command.
1348 @cindex shell escape
1349 @item shell @var{command-string}
1350 @itemx !@var{command-string}
1351 Invoke a standard shell to execute @var{command-string}.
1352 Note that no space is needed between @code{!} and @var{command-string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1877 the @sc{gnu} C compiler, provides macro information if you are using
1878 the DWARF debugging format, and specify the option @option{-g3}.
1880 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1881 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1882 information on @value{NGCC} options affecting debug information.
1884 You will have the best debugging experience if you use the latest
1885 version of the DWARF debugging format that your compiler supports.
1886 DWARF is currently the most expressive and best supported debugging
1887 format in @value{GDBN}.
1891 @section Starting your Program
1897 @kindex r @r{(@code{run})}
1900 Use the @code{run} command to start your program under @value{GDBN}.
1901 You must first specify the program name (except on VxWorks) with an
1902 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1903 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1904 (@pxref{Files, ,Commands to Specify Files}).
1908 If you are running your program in an execution environment that
1909 supports processes, @code{run} creates an inferior process and makes
1910 that process run your program. In some environments without processes,
1911 @code{run} jumps to the start of your program. Other targets,
1912 like @samp{remote}, are always running. If you get an error
1913 message like this one:
1916 The "remote" target does not support "run".
1917 Try "help target" or "continue".
1921 then use @code{continue} to run your program. You may need @code{load}
1922 first (@pxref{load}).
1924 The execution of a program is affected by certain information it
1925 receives from its superior. @value{GDBN} provides ways to specify this
1926 information, which you must do @emph{before} starting your program. (You
1927 can change it after starting your program, but such changes only affect
1928 your program the next time you start it.) This information may be
1929 divided into four categories:
1932 @item The @emph{arguments.}
1933 Specify the arguments to give your program as the arguments of the
1934 @code{run} command. If a shell is available on your target, the shell
1935 is used to pass the arguments, so that you may use normal conventions
1936 (such as wildcard expansion or variable substitution) in describing
1938 In Unix systems, you can control which shell is used with the
1939 @code{SHELL} environment variable.
1940 @xref{Arguments, ,Your Program's Arguments}.
1942 @item The @emph{environment.}
1943 Your program normally inherits its environment from @value{GDBN}, but you can
1944 use the @value{GDBN} commands @code{set environment} and @code{unset
1945 environment} to change parts of the environment that affect
1946 your program. @xref{Environment, ,Your Program's Environment}.
1948 @item The @emph{working directory.}
1949 Your program inherits its working directory from @value{GDBN}. You can set
1950 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1951 @xref{Working Directory, ,Your Program's Working Directory}.
1953 @item The @emph{standard input and output.}
1954 Your program normally uses the same device for standard input and
1955 standard output as @value{GDBN} is using. You can redirect input and output
1956 in the @code{run} command line, or you can use the @code{tty} command to
1957 set a different device for your program.
1958 @xref{Input/Output, ,Your Program's Input and Output}.
1961 @emph{Warning:} While input and output redirection work, you cannot use
1962 pipes to pass the output of the program you are debugging to another
1963 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1967 When you issue the @code{run} command, your program begins to execute
1968 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1969 of how to arrange for your program to stop. Once your program has
1970 stopped, you may call functions in your program, using the @code{print}
1971 or @code{call} commands. @xref{Data, ,Examining Data}.
1973 If the modification time of your symbol file has changed since the last
1974 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1975 table, and reads it again. When it does this, @value{GDBN} tries to retain
1976 your current breakpoints.
1981 @cindex run to main procedure
1982 The name of the main procedure can vary from language to language.
1983 With C or C@t{++}, the main procedure name is always @code{main}, but
1984 other languages such as Ada do not require a specific name for their
1985 main procedure. The debugger provides a convenient way to start the
1986 execution of the program and to stop at the beginning of the main
1987 procedure, depending on the language used.
1989 The @samp{start} command does the equivalent of setting a temporary
1990 breakpoint at the beginning of the main procedure and then invoking
1991 the @samp{run} command.
1993 @cindex elaboration phase
1994 Some programs contain an @dfn{elaboration} phase where some startup code is
1995 executed before the main procedure is called. This depends on the
1996 languages used to write your program. In C@t{++}, for instance,
1997 constructors for static and global objects are executed before
1998 @code{main} is called. It is therefore possible that the debugger stops
1999 before reaching the main procedure. However, the temporary breakpoint
2000 will remain to halt execution.
2002 Specify the arguments to give to your program as arguments to the
2003 @samp{start} command. These arguments will be given verbatim to the
2004 underlying @samp{run} command. Note that the same arguments will be
2005 reused if no argument is provided during subsequent calls to
2006 @samp{start} or @samp{run}.
2008 It is sometimes necessary to debug the program during elaboration. In
2009 these cases, using the @code{start} command would stop the execution of
2010 your program too late, as the program would have already completed the
2011 elaboration phase. Under these circumstances, insert breakpoints in your
2012 elaboration code before running your program.
2014 @kindex set exec-wrapper
2015 @item set exec-wrapper @var{wrapper}
2016 @itemx show exec-wrapper
2017 @itemx unset exec-wrapper
2018 When @samp{exec-wrapper} is set, the specified wrapper is used to
2019 launch programs for debugging. @value{GDBN} starts your program
2020 with a shell command of the form @kbd{exec @var{wrapper}
2021 @var{program}}. Quoting is added to @var{program} and its
2022 arguments, but not to @var{wrapper}, so you should add quotes if
2023 appropriate for your shell. The wrapper runs until it executes
2024 your program, and then @value{GDBN} takes control.
2026 You can use any program that eventually calls @code{execve} with
2027 its arguments as a wrapper. Several standard Unix utilities do
2028 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2029 with @code{exec "$@@"} will also work.
2031 For example, you can use @code{env} to pass an environment variable to
2032 the debugged program, without setting the variable in your shell's
2036 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2040 This command is available when debugging locally on most targets, excluding
2041 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2043 @kindex set disable-randomization
2044 @item set disable-randomization
2045 @itemx set disable-randomization on
2046 This option (enabled by default in @value{GDBN}) will turn off the native
2047 randomization of the virtual address space of the started program. This option
2048 is useful for multiple debugging sessions to make the execution better
2049 reproducible and memory addresses reusable across debugging sessions.
2051 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2052 On @sc{gnu}/Linux you can get the same behavior using
2055 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2058 @item set disable-randomization off
2059 Leave the behavior of the started executable unchanged. Some bugs rear their
2060 ugly heads only when the program is loaded at certain addresses. If your bug
2061 disappears when you run the program under @value{GDBN}, that might be because
2062 @value{GDBN} by default disables the address randomization on platforms, such
2063 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2064 disable-randomization off} to try to reproduce such elusive bugs.
2066 On targets where it is available, virtual address space randomization
2067 protects the programs against certain kinds of security attacks. In these
2068 cases the attacker needs to know the exact location of a concrete executable
2069 code. Randomizing its location makes it impossible to inject jumps misusing
2070 a code at its expected addresses.
2072 Prelinking shared libraries provides a startup performance advantage but it
2073 makes addresses in these libraries predictable for privileged processes by
2074 having just unprivileged access at the target system. Reading the shared
2075 library binary gives enough information for assembling the malicious code
2076 misusing it. Still even a prelinked shared library can get loaded at a new
2077 random address just requiring the regular relocation process during the
2078 startup. Shared libraries not already prelinked are always loaded at
2079 a randomly chosen address.
2081 Position independent executables (PIE) contain position independent code
2082 similar to the shared libraries and therefore such executables get loaded at
2083 a randomly chosen address upon startup. PIE executables always load even
2084 already prelinked shared libraries at a random address. You can build such
2085 executable using @command{gcc -fPIE -pie}.
2087 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2088 (as long as the randomization is enabled).
2090 @item show disable-randomization
2091 Show the current setting of the explicit disable of the native randomization of
2092 the virtual address space of the started program.
2097 @section Your Program's Arguments
2099 @cindex arguments (to your program)
2100 The arguments to your program can be specified by the arguments of the
2102 They are passed to a shell, which expands wildcard characters and
2103 performs redirection of I/O, and thence to your program. Your
2104 @code{SHELL} environment variable (if it exists) specifies what shell
2105 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2106 the default shell (@file{/bin/sh} on Unix).
2108 On non-Unix systems, the program is usually invoked directly by
2109 @value{GDBN}, which emulates I/O redirection via the appropriate system
2110 calls, and the wildcard characters are expanded by the startup code of
2111 the program, not by the shell.
2113 @code{run} with no arguments uses the same arguments used by the previous
2114 @code{run}, or those set by the @code{set args} command.
2119 Specify the arguments to be used the next time your program is run. If
2120 @code{set args} has no arguments, @code{run} executes your program
2121 with no arguments. Once you have run your program with arguments,
2122 using @code{set args} before the next @code{run} is the only way to run
2123 it again without arguments.
2127 Show the arguments to give your program when it is started.
2131 @section Your Program's Environment
2133 @cindex environment (of your program)
2134 The @dfn{environment} consists of a set of environment variables and
2135 their values. Environment variables conventionally record such things as
2136 your user name, your home directory, your terminal type, and your search
2137 path for programs to run. Usually you set up environment variables with
2138 the shell and they are inherited by all the other programs you run. When
2139 debugging, it can be useful to try running your program with a modified
2140 environment without having to start @value{GDBN} over again.
2144 @item path @var{directory}
2145 Add @var{directory} to the front of the @code{PATH} environment variable
2146 (the search path for executables) that will be passed to your program.
2147 The value of @code{PATH} used by @value{GDBN} does not change.
2148 You may specify several directory names, separated by whitespace or by a
2149 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2150 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2151 is moved to the front, so it is searched sooner.
2153 You can use the string @samp{$cwd} to refer to whatever is the current
2154 working directory at the time @value{GDBN} searches the path. If you
2155 use @samp{.} instead, it refers to the directory where you executed the
2156 @code{path} command. @value{GDBN} replaces @samp{.} in the
2157 @var{directory} argument (with the current path) before adding
2158 @var{directory} to the search path.
2159 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2160 @c document that, since repeating it would be a no-op.
2164 Display the list of search paths for executables (the @code{PATH}
2165 environment variable).
2167 @kindex show environment
2168 @item show environment @r{[}@var{varname}@r{]}
2169 Print the value of environment variable @var{varname} to be given to
2170 your program when it starts. If you do not supply @var{varname},
2171 print the names and values of all environment variables to be given to
2172 your program. You can abbreviate @code{environment} as @code{env}.
2174 @kindex set environment
2175 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2176 Set environment variable @var{varname} to @var{value}. The value
2177 changes for your program only, not for @value{GDBN} itself. @var{value} may
2178 be any string; the values of environment variables are just strings, and
2179 any interpretation is supplied by your program itself. The @var{value}
2180 parameter is optional; if it is eliminated, the variable is set to a
2182 @c "any string" here does not include leading, trailing
2183 @c blanks. Gnu asks: does anyone care?
2185 For example, this command:
2192 tells the debugged program, when subsequently run, that its user is named
2193 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2194 are not actually required.)
2196 @kindex unset environment
2197 @item unset environment @var{varname}
2198 Remove variable @var{varname} from the environment to be passed to your
2199 program. This is different from @samp{set env @var{varname} =};
2200 @code{unset environment} removes the variable from the environment,
2201 rather than assigning it an empty value.
2204 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2206 by your @code{SHELL} environment variable if it exists (or
2207 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2208 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2209 @file{.bashrc} for BASH---any variables you set in that file affect
2210 your program. You may wish to move setting of environment variables to
2211 files that are only run when you sign on, such as @file{.login} or
2214 @node Working Directory
2215 @section Your Program's Working Directory
2217 @cindex working directory (of your program)
2218 Each time you start your program with @code{run}, it inherits its
2219 working directory from the current working directory of @value{GDBN}.
2220 The @value{GDBN} working directory is initially whatever it inherited
2221 from its parent process (typically the shell), but you can specify a new
2222 working directory in @value{GDBN} with the @code{cd} command.
2224 The @value{GDBN} working directory also serves as a default for the commands
2225 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2230 @cindex change working directory
2231 @item cd @var{directory}
2232 Set the @value{GDBN} working directory to @var{directory}.
2236 Print the @value{GDBN} working directory.
2239 It is generally impossible to find the current working directory of
2240 the process being debugged (since a program can change its directory
2241 during its run). If you work on a system where @value{GDBN} is
2242 configured with the @file{/proc} support, you can use the @code{info
2243 proc} command (@pxref{SVR4 Process Information}) to find out the
2244 current working directory of the debuggee.
2247 @section Your Program's Input and Output
2252 By default, the program you run under @value{GDBN} does input and output to
2253 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2254 to its own terminal modes to interact with you, but it records the terminal
2255 modes your program was using and switches back to them when you continue
2256 running your program.
2259 @kindex info terminal
2261 Displays information recorded by @value{GDBN} about the terminal modes your
2265 You can redirect your program's input and/or output using shell
2266 redirection with the @code{run} command. For example,
2273 starts your program, diverting its output to the file @file{outfile}.
2276 @cindex controlling terminal
2277 Another way to specify where your program should do input and output is
2278 with the @code{tty} command. This command accepts a file name as
2279 argument, and causes this file to be the default for future @code{run}
2280 commands. It also resets the controlling terminal for the child
2281 process, for future @code{run} commands. For example,
2288 directs that processes started with subsequent @code{run} commands
2289 default to do input and output on the terminal @file{/dev/ttyb} and have
2290 that as their controlling terminal.
2292 An explicit redirection in @code{run} overrides the @code{tty} command's
2293 effect on the input/output device, but not its effect on the controlling
2296 When you use the @code{tty} command or redirect input in the @code{run}
2297 command, only the input @emph{for your program} is affected. The input
2298 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2299 for @code{set inferior-tty}.
2301 @cindex inferior tty
2302 @cindex set inferior controlling terminal
2303 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2304 display the name of the terminal that will be used for future runs of your
2308 @item set inferior-tty /dev/ttyb
2309 @kindex set inferior-tty
2310 Set the tty for the program being debugged to /dev/ttyb.
2312 @item show inferior-tty
2313 @kindex show inferior-tty
2314 Show the current tty for the program being debugged.
2318 @section Debugging an Already-running Process
2323 @item attach @var{process-id}
2324 This command attaches to a running process---one that was started
2325 outside @value{GDBN}. (@code{info files} shows your active
2326 targets.) The command takes as argument a process ID. The usual way to
2327 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2328 or with the @samp{jobs -l} shell command.
2330 @code{attach} does not repeat if you press @key{RET} a second time after
2331 executing the command.
2334 To use @code{attach}, your program must be running in an environment
2335 which supports processes; for example, @code{attach} does not work for
2336 programs on bare-board targets that lack an operating system. You must
2337 also have permission to send the process a signal.
2339 When you use @code{attach}, the debugger finds the program running in
2340 the process first by looking in the current working directory, then (if
2341 the program is not found) by using the source file search path
2342 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2343 the @code{file} command to load the program. @xref{Files, ,Commands to
2346 The first thing @value{GDBN} does after arranging to debug the specified
2347 process is to stop it. You can examine and modify an attached process
2348 with all the @value{GDBN} commands that are ordinarily available when
2349 you start processes with @code{run}. You can insert breakpoints; you
2350 can step and continue; you can modify storage. If you would rather the
2351 process continue running, you may use the @code{continue} command after
2352 attaching @value{GDBN} to the process.
2357 When you have finished debugging the attached process, you can use the
2358 @code{detach} command to release it from @value{GDBN} control. Detaching
2359 the process continues its execution. After the @code{detach} command,
2360 that process and @value{GDBN} become completely independent once more, and you
2361 are ready to @code{attach} another process or start one with @code{run}.
2362 @code{detach} does not repeat if you press @key{RET} again after
2363 executing the command.
2366 If you exit @value{GDBN} while you have an attached process, you detach
2367 that process. If you use the @code{run} command, you kill that process.
2368 By default, @value{GDBN} asks for confirmation if you try to do either of these
2369 things; you can control whether or not you need to confirm by using the
2370 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2374 @section Killing the Child Process
2379 Kill the child process in which your program is running under @value{GDBN}.
2382 This command is useful if you wish to debug a core dump instead of a
2383 running process. @value{GDBN} ignores any core dump file while your program
2386 On some operating systems, a program cannot be executed outside @value{GDBN}
2387 while you have breakpoints set on it inside @value{GDBN}. You can use the
2388 @code{kill} command in this situation to permit running your program
2389 outside the debugger.
2391 The @code{kill} command is also useful if you wish to recompile and
2392 relink your program, since on many systems it is impossible to modify an
2393 executable file while it is running in a process. In this case, when you
2394 next type @code{run}, @value{GDBN} notices that the file has changed, and
2395 reads the symbol table again (while trying to preserve your current
2396 breakpoint settings).
2398 @node Inferiors and Programs
2399 @section Debugging Multiple Inferiors and Programs
2401 @value{GDBN} lets you run and debug multiple programs in a single
2402 session. In addition, @value{GDBN} on some systems may let you run
2403 several programs simultaneously (otherwise you have to exit from one
2404 before starting another). In the most general case, you can have
2405 multiple threads of execution in each of multiple processes, launched
2406 from multiple executables.
2409 @value{GDBN} represents the state of each program execution with an
2410 object called an @dfn{inferior}. An inferior typically corresponds to
2411 a process, but is more general and applies also to targets that do not
2412 have processes. Inferiors may be created before a process runs, and
2413 may be retained after a process exits. Inferiors have unique
2414 identifiers that are different from process ids. Usually each
2415 inferior will also have its own distinct address space, although some
2416 embedded targets may have several inferiors running in different parts
2417 of a single address space. Each inferior may in turn have multiple
2418 threads running in it.
2420 To find out what inferiors exist at any moment, use @w{@code{info
2424 @kindex info inferiors
2425 @item info inferiors
2426 Print a list of all inferiors currently being managed by @value{GDBN}.
2428 @value{GDBN} displays for each inferior (in this order):
2432 the inferior number assigned by @value{GDBN}
2435 the target system's inferior identifier
2438 the name of the executable the inferior is running.
2443 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2444 indicates the current inferior.
2448 @c end table here to get a little more width for example
2451 (@value{GDBP}) info inferiors
2452 Num Description Executable
2453 2 process 2307 hello
2454 * 1 process 3401 goodbye
2457 To switch focus between inferiors, use the @code{inferior} command:
2460 @kindex inferior @var{infno}
2461 @item inferior @var{infno}
2462 Make inferior number @var{infno} the current inferior. The argument
2463 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2464 in the first field of the @samp{info inferiors} display.
2468 You can get multiple executables into a debugging session via the
2469 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2470 systems @value{GDBN} can add inferiors to the debug session
2471 automatically by following calls to @code{fork} and @code{exec}. To
2472 remove inferiors from the debugging session use the
2473 @w{@code{remove-inferiors}} command.
2476 @kindex add-inferior
2477 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2478 Adds @var{n} inferiors to be run using @var{executable} as the
2479 executable. @var{n} defaults to 1. If no executable is specified,
2480 the inferiors begins empty, with no program. You can still assign or
2481 change the program assigned to the inferior at any time by using the
2482 @code{file} command with the executable name as its argument.
2484 @kindex clone-inferior
2485 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2486 Adds @var{n} inferiors ready to execute the same program as inferior
2487 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2488 number of the current inferior. This is a convenient command when you
2489 want to run another instance of the inferior you are debugging.
2492 (@value{GDBP}) info inferiors
2493 Num Description Executable
2494 * 1 process 29964 helloworld
2495 (@value{GDBP}) clone-inferior
2498 (@value{GDBP}) info inferiors
2499 Num Description Executable
2501 * 1 process 29964 helloworld
2504 You can now simply switch focus to inferior 2 and run it.
2506 @kindex remove-inferiors
2507 @item remove-inferiors @var{infno}@dots{}
2508 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2509 possible to remove an inferior that is running with this command. For
2510 those, use the @code{kill} or @code{detach} command first.
2514 To quit debugging one of the running inferiors that is not the current
2515 inferior, you can either detach from it by using the @w{@code{detach
2516 inferior}} command (allowing it to run independently), or kill it
2517 using the @w{@code{kill inferiors}} command:
2520 @kindex detach inferiors @var{infno}@dots{}
2521 @item detach inferior @var{infno}@dots{}
2522 Detach from the inferior or inferiors identified by @value{GDBN}
2523 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2524 still stays on the list of inferiors shown by @code{info inferiors},
2525 but its Description will show @samp{<null>}.
2527 @kindex kill inferiors @var{infno}@dots{}
2528 @item kill inferiors @var{infno}@dots{}
2529 Kill the inferior or inferiors identified by @value{GDBN} inferior
2530 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2531 stays on the list of inferiors shown by @code{info inferiors}, but its
2532 Description will show @samp{<null>}.
2535 After the successful completion of a command such as @code{detach},
2536 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2537 a normal process exit, the inferior is still valid and listed with
2538 @code{info inferiors}, ready to be restarted.
2541 To be notified when inferiors are started or exit under @value{GDBN}'s
2542 control use @w{@code{set print inferior-events}}:
2545 @kindex set print inferior-events
2546 @cindex print messages on inferior start and exit
2547 @item set print inferior-events
2548 @itemx set print inferior-events on
2549 @itemx set print inferior-events off
2550 The @code{set print inferior-events} command allows you to enable or
2551 disable printing of messages when @value{GDBN} notices that new
2552 inferiors have started or that inferiors have exited or have been
2553 detached. By default, these messages will not be printed.
2555 @kindex show print inferior-events
2556 @item show print inferior-events
2557 Show whether messages will be printed when @value{GDBN} detects that
2558 inferiors have started, exited or have been detached.
2561 Many commands will work the same with multiple programs as with a
2562 single program: e.g., @code{print myglobal} will simply display the
2563 value of @code{myglobal} in the current inferior.
2566 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2567 get more info about the relationship of inferiors, programs, address
2568 spaces in a debug session. You can do that with the @w{@code{maint
2569 info program-spaces}} command.
2572 @kindex maint info program-spaces
2573 @item maint info program-spaces
2574 Print a list of all program spaces currently being managed by
2577 @value{GDBN} displays for each program space (in this order):
2581 the program space number assigned by @value{GDBN}
2584 the name of the executable loaded into the program space, with e.g.,
2585 the @code{file} command.
2590 An asterisk @samp{*} preceding the @value{GDBN} program space number
2591 indicates the current program space.
2593 In addition, below each program space line, @value{GDBN} prints extra
2594 information that isn't suitable to display in tabular form. For
2595 example, the list of inferiors bound to the program space.
2598 (@value{GDBP}) maint info program-spaces
2601 Bound inferiors: ID 1 (process 21561)
2605 Here we can see that no inferior is running the program @code{hello},
2606 while @code{process 21561} is running the program @code{goodbye}. On
2607 some targets, it is possible that multiple inferiors are bound to the
2608 same program space. The most common example is that of debugging both
2609 the parent and child processes of a @code{vfork} call. For example,
2612 (@value{GDBP}) maint info program-spaces
2615 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2618 Here, both inferior 2 and inferior 1 are running in the same program
2619 space as a result of inferior 1 having executed a @code{vfork} call.
2623 @section Debugging Programs with Multiple Threads
2625 @cindex threads of execution
2626 @cindex multiple threads
2627 @cindex switching threads
2628 In some operating systems, such as HP-UX and Solaris, a single program
2629 may have more than one @dfn{thread} of execution. The precise semantics
2630 of threads differ from one operating system to another, but in general
2631 the threads of a single program are akin to multiple processes---except
2632 that they share one address space (that is, they can all examine and
2633 modify the same variables). On the other hand, each thread has its own
2634 registers and execution stack, and perhaps private memory.
2636 @value{GDBN} provides these facilities for debugging multi-thread
2640 @item automatic notification of new threads
2641 @item @samp{thread @var{threadno}}, a command to switch among threads
2642 @item @samp{info threads}, a command to inquire about existing threads
2643 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2644 a command to apply a command to a list of threads
2645 @item thread-specific breakpoints
2646 @item @samp{set print thread-events}, which controls printing of
2647 messages on thread start and exit.
2648 @item @samp{set libthread-db-search-path @var{path}}, which lets
2649 the user specify which @code{libthread_db} to use if the default choice
2650 isn't compatible with the program.
2654 @emph{Warning:} These facilities are not yet available on every
2655 @value{GDBN} configuration where the operating system supports threads.
2656 If your @value{GDBN} does not support threads, these commands have no
2657 effect. For example, a system without thread support shows no output
2658 from @samp{info threads}, and always rejects the @code{thread} command,
2662 (@value{GDBP}) info threads
2663 (@value{GDBP}) thread 1
2664 Thread ID 1 not known. Use the "info threads" command to
2665 see the IDs of currently known threads.
2667 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2668 @c doesn't support threads"?
2671 @cindex focus of debugging
2672 @cindex current thread
2673 The @value{GDBN} thread debugging facility allows you to observe all
2674 threads while your program runs---but whenever @value{GDBN} takes
2675 control, one thread in particular is always the focus of debugging.
2676 This thread is called the @dfn{current thread}. Debugging commands show
2677 program information from the perspective of the current thread.
2679 @cindex @code{New} @var{systag} message
2680 @cindex thread identifier (system)
2681 @c FIXME-implementors!! It would be more helpful if the [New...] message
2682 @c included GDB's numeric thread handle, so you could just go to that
2683 @c thread without first checking `info threads'.
2684 Whenever @value{GDBN} detects a new thread in your program, it displays
2685 the target system's identification for the thread with a message in the
2686 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2687 whose form varies depending on the particular system. For example, on
2688 @sc{gnu}/Linux, you might see
2691 [New Thread 0x41e02940 (LWP 25582)]
2695 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2696 the @var{systag} is simply something like @samp{process 368}, with no
2699 @c FIXME!! (1) Does the [New...] message appear even for the very first
2700 @c thread of a program, or does it only appear for the
2701 @c second---i.e.@: when it becomes obvious we have a multithread
2703 @c (2) *Is* there necessarily a first thread always? Or do some
2704 @c multithread systems permit starting a program with multiple
2705 @c threads ab initio?
2707 @cindex thread number
2708 @cindex thread identifier (GDB)
2709 For debugging purposes, @value{GDBN} associates its own thread
2710 number---always a single integer---with each thread in your program.
2713 @kindex info threads
2714 @item info threads @r{[}@var{id}@dots{}@r{]}
2715 Display a summary of all threads currently in your program. Optional
2716 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2717 means to print information only about the specified thread or threads.
2718 @value{GDBN} displays for each thread (in this order):
2722 the thread number assigned by @value{GDBN}
2725 the target system's thread identifier (@var{systag})
2728 the thread's name, if one is known. A thread can either be named by
2729 the user (see @code{thread name}, below), or, in some cases, by the
2733 the current stack frame summary for that thread
2737 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2738 indicates the current thread.
2742 @c end table here to get a little more width for example
2745 (@value{GDBP}) info threads
2747 3 process 35 thread 27 0x34e5 in sigpause ()
2748 2 process 35 thread 23 0x34e5 in sigpause ()
2749 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 (@value{GDBP}) thread 2
2774 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2775 #0 some_function (ignore=0x0) at example.c:8
2776 8 printf ("hello\n");
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @vindex $_thread@r{, convenience variable}
2785 The debugger convenience variable @samp{$_thread} contains the number
2786 of the current thread. You may find this useful in writing breakpoint
2787 conditional expressions, command scripts, and so forth. See
2788 @xref{Convenience Vars,, Convenience Variables}, for general
2789 information on convenience variables.
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno} | all] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2803 @cindex name a thread
2804 @item thread name [@var{name}]
2805 This command assigns a name to the current thread. If no argument is
2806 given, any existing user-specified name is removed. The thread name
2807 appears in the @samp{info threads} display.
2809 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2810 determine the name of the thread as given by the OS. On these
2811 systems, a name specified with @samp{thread name} will override the
2812 system-give name, and removing the user-specified name will cause
2813 @value{GDBN} to once again display the system-specified name.
2816 @cindex search for a thread
2817 @item thread find [@var{regexp}]
2818 Search for and display thread ids whose name or @var{systag}
2819 matches the supplied regular expression.
2821 As well as being the complement to the @samp{thread name} command,
2822 this command also allows you to identify a thread by its target
2823 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2827 (@value{GDBN}) thread find 26688
2828 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2829 (@value{GDBN}) info thread 4
2831 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2834 @kindex set print thread-events
2835 @cindex print messages on thread start and exit
2836 @item set print thread-events
2837 @itemx set print thread-events on
2838 @itemx set print thread-events off
2839 The @code{set print thread-events} command allows you to enable or
2840 disable printing of messages when @value{GDBN} notices that new threads have
2841 started or that threads have exited. By default, these messages will
2842 be printed if detection of these events is supported by the target.
2843 Note that these messages cannot be disabled on all targets.
2845 @kindex show print thread-events
2846 @item show print thread-events
2847 Show whether messages will be printed when @value{GDBN} detects that threads
2848 have started and exited.
2851 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2852 more information about how @value{GDBN} behaves when you stop and start
2853 programs with multiple threads.
2855 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2856 watchpoints in programs with multiple threads.
2859 @kindex set libthread-db-search-path
2860 @cindex search path for @code{libthread_db}
2861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2862 If this variable is set, @var{path} is a colon-separated list of
2863 directories @value{GDBN} will use to search for @code{libthread_db}.
2864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2870 @code{libthread_db} library to obtain information about threads in the
2871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2872 to find @code{libthread_db}.
2874 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2875 refers to the default system directories that are
2876 normally searched for loading shared libraries.
2878 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2879 refers to the directory from which @code{libpthread}
2880 was loaded in the inferior process.
2882 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2883 @value{GDBN} attempts to initialize it with the current inferior process.
2884 If this initialization fails (which could happen because of a version
2885 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2886 will unload @code{libthread_db}, and continue with the next directory.
2887 If none of @code{libthread_db} libraries initialize successfully,
2888 @value{GDBN} will issue a warning and thread debugging will be disabled.
2890 Setting @code{libthread-db-search-path} is currently implemented
2891 only on some platforms.
2893 @kindex show libthread-db-search-path
2894 @item show libthread-db-search-path
2895 Display current libthread_db search path.
2897 @kindex set debug libthread-db
2898 @kindex show debug libthread-db
2899 @cindex debugging @code{libthread_db}
2900 @item set debug libthread-db
2901 @itemx show debug libthread-db
2902 Turns on or off display of @code{libthread_db}-related events.
2903 Use @code{1} to enable, @code{0} to disable.
2907 @section Debugging Forks
2909 @cindex fork, debugging programs which call
2910 @cindex multiple processes
2911 @cindex processes, multiple
2912 On most systems, @value{GDBN} has no special support for debugging
2913 programs which create additional processes using the @code{fork}
2914 function. When a program forks, @value{GDBN} will continue to debug the
2915 parent process and the child process will run unimpeded. If you have
2916 set a breakpoint in any code which the child then executes, the child
2917 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2918 will cause it to terminate.
2920 However, if you want to debug the child process there is a workaround
2921 which isn't too painful. Put a call to @code{sleep} in the code which
2922 the child process executes after the fork. It may be useful to sleep
2923 only if a certain environment variable is set, or a certain file exists,
2924 so that the delay need not occur when you don't want to run @value{GDBN}
2925 on the child. While the child is sleeping, use the @code{ps} program to
2926 get its process ID. Then tell @value{GDBN} (a new invocation of
2927 @value{GDBN} if you are also debugging the parent process) to attach to
2928 the child process (@pxref{Attach}). From that point on you can debug
2929 the child process just like any other process which you attached to.
2931 On some systems, @value{GDBN} provides support for debugging programs that
2932 create additional processes using the @code{fork} or @code{vfork} functions.
2933 Currently, the only platforms with this feature are HP-UX (11.x and later
2934 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2936 By default, when a program forks, @value{GDBN} will continue to debug
2937 the parent process and the child process will run unimpeded.
2939 If you want to follow the child process instead of the parent process,
2940 use the command @w{@code{set follow-fork-mode}}.
2943 @kindex set follow-fork-mode
2944 @item set follow-fork-mode @var{mode}
2945 Set the debugger response to a program call of @code{fork} or
2946 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2947 process. The @var{mode} argument can be:
2951 The original process is debugged after a fork. The child process runs
2952 unimpeded. This is the default.
2955 The new process is debugged after a fork. The parent process runs
2960 @kindex show follow-fork-mode
2961 @item show follow-fork-mode
2962 Display the current debugger response to a @code{fork} or @code{vfork} call.
2965 @cindex debugging multiple processes
2966 On Linux, if you want to debug both the parent and child processes, use the
2967 command @w{@code{set detach-on-fork}}.
2970 @kindex set detach-on-fork
2971 @item set detach-on-fork @var{mode}
2972 Tells gdb whether to detach one of the processes after a fork, or
2973 retain debugger control over them both.
2977 The child process (or parent process, depending on the value of
2978 @code{follow-fork-mode}) will be detached and allowed to run
2979 independently. This is the default.
2982 Both processes will be held under the control of @value{GDBN}.
2983 One process (child or parent, depending on the value of
2984 @code{follow-fork-mode}) is debugged as usual, while the other
2989 @kindex show detach-on-fork
2990 @item show detach-on-fork
2991 Show whether detach-on-fork mode is on/off.
2994 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2995 will retain control of all forked processes (including nested forks).
2996 You can list the forked processes under the control of @value{GDBN} by
2997 using the @w{@code{info inferiors}} command, and switch from one fork
2998 to another by using the @code{inferior} command (@pxref{Inferiors and
2999 Programs, ,Debugging Multiple Inferiors and Programs}).
3001 To quit debugging one of the forked processes, you can either detach
3002 from it by using the @w{@code{detach inferiors}} command (allowing it
3003 to run independently), or kill it using the @w{@code{kill inferiors}}
3004 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3007 If you ask to debug a child process and a @code{vfork} is followed by an
3008 @code{exec}, @value{GDBN} executes the new target up to the first
3009 breakpoint in the new target. If you have a breakpoint set on
3010 @code{main} in your original program, the breakpoint will also be set on
3011 the child process's @code{main}.
3013 On some systems, when a child process is spawned by @code{vfork}, you
3014 cannot debug the child or parent until an @code{exec} call completes.
3016 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3017 call executes, the new target restarts. To restart the parent
3018 process, use the @code{file} command with the parent executable name
3019 as its argument. By default, after an @code{exec} call executes,
3020 @value{GDBN} discards the symbols of the previous executable image.
3021 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3025 @kindex set follow-exec-mode
3026 @item set follow-exec-mode @var{mode}
3028 Set debugger response to a program call of @code{exec}. An
3029 @code{exec} call replaces the program image of a process.
3031 @code{follow-exec-mode} can be:
3035 @value{GDBN} creates a new inferior and rebinds the process to this
3036 new inferior. The program the process was running before the
3037 @code{exec} call can be restarted afterwards by restarting the
3043 (@value{GDBP}) info inferiors
3045 Id Description Executable
3048 process 12020 is executing new program: prog2
3049 Program exited normally.
3050 (@value{GDBP}) info inferiors
3051 Id Description Executable
3057 @value{GDBN} keeps the process bound to the same inferior. The new
3058 executable image replaces the previous executable loaded in the
3059 inferior. Restarting the inferior after the @code{exec} call, with
3060 e.g., the @code{run} command, restarts the executable the process was
3061 running after the @code{exec} call. This is the default mode.
3066 (@value{GDBP}) info inferiors
3067 Id Description Executable
3070 process 12020 is executing new program: prog2
3071 Program exited normally.
3072 (@value{GDBP}) info inferiors
3073 Id Description Executable
3080 You can use the @code{catch} command to make @value{GDBN} stop whenever
3081 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3082 Catchpoints, ,Setting Catchpoints}.
3084 @node Checkpoint/Restart
3085 @section Setting a @emph{Bookmark} to Return to Later
3090 @cindex snapshot of a process
3091 @cindex rewind program state
3093 On certain operating systems@footnote{Currently, only
3094 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3095 program's state, called a @dfn{checkpoint}, and come back to it
3098 Returning to a checkpoint effectively undoes everything that has
3099 happened in the program since the @code{checkpoint} was saved. This
3100 includes changes in memory, registers, and even (within some limits)
3101 system state. Effectively, it is like going back in time to the
3102 moment when the checkpoint was saved.
3104 Thus, if you're stepping thru a program and you think you're
3105 getting close to the point where things go wrong, you can save
3106 a checkpoint. Then, if you accidentally go too far and miss
3107 the critical statement, instead of having to restart your program
3108 from the beginning, you can just go back to the checkpoint and
3109 start again from there.
3111 This can be especially useful if it takes a lot of time or
3112 steps to reach the point where you think the bug occurs.
3114 To use the @code{checkpoint}/@code{restart} method of debugging:
3119 Save a snapshot of the debugged program's current execution state.
3120 The @code{checkpoint} command takes no arguments, but each checkpoint
3121 is assigned a small integer id, similar to a breakpoint id.
3123 @kindex info checkpoints
3124 @item info checkpoints
3125 List the checkpoints that have been saved in the current debugging
3126 session. For each checkpoint, the following information will be
3133 @item Source line, or label
3136 @kindex restart @var{checkpoint-id}
3137 @item restart @var{checkpoint-id}
3138 Restore the program state that was saved as checkpoint number
3139 @var{checkpoint-id}. All program variables, registers, stack frames
3140 etc.@: will be returned to the values that they had when the checkpoint
3141 was saved. In essence, gdb will ``wind back the clock'' to the point
3142 in time when the checkpoint was saved.
3144 Note that breakpoints, @value{GDBN} variables, command history etc.
3145 are not affected by restoring a checkpoint. In general, a checkpoint
3146 only restores things that reside in the program being debugged, not in
3149 @kindex delete checkpoint @var{checkpoint-id}
3150 @item delete checkpoint @var{checkpoint-id}
3151 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3155 Returning to a previously saved checkpoint will restore the user state
3156 of the program being debugged, plus a significant subset of the system
3157 (OS) state, including file pointers. It won't ``un-write'' data from
3158 a file, but it will rewind the file pointer to the previous location,
3159 so that the previously written data can be overwritten. For files
3160 opened in read mode, the pointer will also be restored so that the
3161 previously read data can be read again.
3163 Of course, characters that have been sent to a printer (or other
3164 external device) cannot be ``snatched back'', and characters received
3165 from eg.@: a serial device can be removed from internal program buffers,
3166 but they cannot be ``pushed back'' into the serial pipeline, ready to
3167 be received again. Similarly, the actual contents of files that have
3168 been changed cannot be restored (at this time).
3170 However, within those constraints, you actually can ``rewind'' your
3171 program to a previously saved point in time, and begin debugging it
3172 again --- and you can change the course of events so as to debug a
3173 different execution path this time.
3175 @cindex checkpoints and process id
3176 Finally, there is one bit of internal program state that will be
3177 different when you return to a checkpoint --- the program's process
3178 id. Each checkpoint will have a unique process id (or @var{pid}),
3179 and each will be different from the program's original @var{pid}.
3180 If your program has saved a local copy of its process id, this could
3181 potentially pose a problem.
3183 @subsection A Non-obvious Benefit of Using Checkpoints
3185 On some systems such as @sc{gnu}/Linux, address space randomization
3186 is performed on new processes for security reasons. This makes it
3187 difficult or impossible to set a breakpoint, or watchpoint, on an
3188 absolute address if you have to restart the program, since the
3189 absolute location of a symbol will change from one execution to the
3192 A checkpoint, however, is an @emph{identical} copy of a process.
3193 Therefore if you create a checkpoint at (eg.@:) the start of main,
3194 and simply return to that checkpoint instead of restarting the
3195 process, you can avoid the effects of address randomization and
3196 your symbols will all stay in the same place.
3199 @chapter Stopping and Continuing
3201 The principal purposes of using a debugger are so that you can stop your
3202 program before it terminates; or so that, if your program runs into
3203 trouble, you can investigate and find out why.
3205 Inside @value{GDBN}, your program may stop for any of several reasons,
3206 such as a signal, a breakpoint, or reaching a new line after a
3207 @value{GDBN} command such as @code{step}. You may then examine and
3208 change variables, set new breakpoints or remove old ones, and then
3209 continue execution. Usually, the messages shown by @value{GDBN} provide
3210 ample explanation of the status of your program---but you can also
3211 explicitly request this information at any time.
3214 @kindex info program
3216 Display information about the status of your program: whether it is
3217 running or not, what process it is, and why it stopped.
3221 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3222 * Continuing and Stepping:: Resuming execution
3223 * Skipping Over Functions and Files::
3224 Skipping over functions and files
3226 * Thread Stops:: Stopping and starting multi-thread programs
3230 @section Breakpoints, Watchpoints, and Catchpoints
3233 A @dfn{breakpoint} makes your program stop whenever a certain point in
3234 the program is reached. For each breakpoint, you can add conditions to
3235 control in finer detail whether your program stops. You can set
3236 breakpoints with the @code{break} command and its variants (@pxref{Set
3237 Breaks, ,Setting Breakpoints}), to specify the place where your program
3238 should stop by line number, function name or exact address in the
3241 On some systems, you can set breakpoints in shared libraries before
3242 the executable is run. There is a minor limitation on HP-UX systems:
3243 you must wait until the executable is run in order to set breakpoints
3244 in shared library routines that are not called directly by the program
3245 (for example, routines that are arguments in a @code{pthread_create}
3249 @cindex data breakpoints
3250 @cindex memory tracing
3251 @cindex breakpoint on memory address
3252 @cindex breakpoint on variable modification
3253 A @dfn{watchpoint} is a special breakpoint that stops your program
3254 when the value of an expression changes. The expression may be a value
3255 of a variable, or it could involve values of one or more variables
3256 combined by operators, such as @samp{a + b}. This is sometimes called
3257 @dfn{data breakpoints}. You must use a different command to set
3258 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3259 from that, you can manage a watchpoint like any other breakpoint: you
3260 enable, disable, and delete both breakpoints and watchpoints using the
3263 You can arrange to have values from your program displayed automatically
3264 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3268 @cindex breakpoint on events
3269 A @dfn{catchpoint} is another special breakpoint that stops your program
3270 when a certain kind of event occurs, such as the throwing of a C@t{++}
3271 exception or the loading of a library. As with watchpoints, you use a
3272 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3273 Catchpoints}), but aside from that, you can manage a catchpoint like any
3274 other breakpoint. (To stop when your program receives a signal, use the
3275 @code{handle} command; see @ref{Signals, ,Signals}.)
3277 @cindex breakpoint numbers
3278 @cindex numbers for breakpoints
3279 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3280 catchpoint when you create it; these numbers are successive integers
3281 starting with one. In many of the commands for controlling various
3282 features of breakpoints you use the breakpoint number to say which
3283 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3284 @dfn{disabled}; if disabled, it has no effect on your program until you
3287 @cindex breakpoint ranges
3288 @cindex ranges of breakpoints
3289 Some @value{GDBN} commands accept a range of breakpoints on which to
3290 operate. A breakpoint range is either a single breakpoint number, like
3291 @samp{5}, or two such numbers, in increasing order, separated by a
3292 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3293 all breakpoints in that range are operated on.
3296 * Set Breaks:: Setting breakpoints
3297 * Set Watchpoints:: Setting watchpoints
3298 * Set Catchpoints:: Setting catchpoints
3299 * Delete Breaks:: Deleting breakpoints
3300 * Disabling:: Disabling breakpoints
3301 * Conditions:: Break conditions
3302 * Break Commands:: Breakpoint command lists
3303 * Save Breakpoints:: How to save breakpoints in a file
3304 * Error in Breakpoints:: ``Cannot insert breakpoints''
3305 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3309 @subsection Setting Breakpoints
3311 @c FIXME LMB what does GDB do if no code on line of breakpt?
3312 @c consider in particular declaration with/without initialization.
3314 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3317 @kindex b @r{(@code{break})}
3318 @vindex $bpnum@r{, convenience variable}
3319 @cindex latest breakpoint
3320 Breakpoints are set with the @code{break} command (abbreviated
3321 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3322 number of the breakpoint you've set most recently; see @ref{Convenience
3323 Vars,, Convenience Variables}, for a discussion of what you can do with
3324 convenience variables.
3327 @item break @var{location}
3328 Set a breakpoint at the given @var{location}, which can specify a
3329 function name, a line number, or an address of an instruction.
3330 (@xref{Specify Location}, for a list of all the possible ways to
3331 specify a @var{location}.) The breakpoint will stop your program just
3332 before it executes any of the code in the specified @var{location}.
3334 When using source languages that permit overloading of symbols, such as
3335 C@t{++}, a function name may refer to more than one possible place to break.
3336 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3339 It is also possible to insert a breakpoint that will stop the program
3340 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3341 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3344 When called without any arguments, @code{break} sets a breakpoint at
3345 the next instruction to be executed in the selected stack frame
3346 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3347 innermost, this makes your program stop as soon as control
3348 returns to that frame. This is similar to the effect of a
3349 @code{finish} command in the frame inside the selected frame---except
3350 that @code{finish} does not leave an active breakpoint. If you use
3351 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3352 the next time it reaches the current location; this may be useful
3355 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3356 least one instruction has been executed. If it did not do this, you
3357 would be unable to proceed past a breakpoint without first disabling the
3358 breakpoint. This rule applies whether or not the breakpoint already
3359 existed when your program stopped.
3361 @item break @dots{} if @var{cond}
3362 Set a breakpoint with condition @var{cond}; evaluate the expression
3363 @var{cond} each time the breakpoint is reached, and stop only if the
3364 value is nonzero---that is, if @var{cond} evaluates as true.
3365 @samp{@dots{}} stands for one of the possible arguments described
3366 above (or no argument) specifying where to break. @xref{Conditions,
3367 ,Break Conditions}, for more information on breakpoint conditions.
3370 @item tbreak @var{args}
3371 Set a breakpoint enabled only for one stop. @var{args} are the
3372 same as for the @code{break} command, and the breakpoint is set in the same
3373 way, but the breakpoint is automatically deleted after the first time your
3374 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3377 @cindex hardware breakpoints
3378 @item hbreak @var{args}
3379 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3380 @code{break} command and the breakpoint is set in the same way, but the
3381 breakpoint requires hardware support and some target hardware may not
3382 have this support. The main purpose of this is EPROM/ROM code
3383 debugging, so you can set a breakpoint at an instruction without
3384 changing the instruction. This can be used with the new trap-generation
3385 provided by SPARClite DSU and most x86-based targets. These targets
3386 will generate traps when a program accesses some data or instruction
3387 address that is assigned to the debug registers. However the hardware
3388 breakpoint registers can take a limited number of breakpoints. For
3389 example, on the DSU, only two data breakpoints can be set at a time, and
3390 @value{GDBN} will reject this command if more than two are used. Delete
3391 or disable unused hardware breakpoints before setting new ones
3392 (@pxref{Disabling, ,Disabling Breakpoints}).
3393 @xref{Conditions, ,Break Conditions}.
3394 For remote targets, you can restrict the number of hardware
3395 breakpoints @value{GDBN} will use, see @ref{set remote
3396 hardware-breakpoint-limit}.
3399 @item thbreak @var{args}
3400 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3401 are the same as for the @code{hbreak} command and the breakpoint is set in
3402 the same way. However, like the @code{tbreak} command,
3403 the breakpoint is automatically deleted after the
3404 first time your program stops there. Also, like the @code{hbreak}
3405 command, the breakpoint requires hardware support and some target hardware
3406 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3407 See also @ref{Conditions, ,Break Conditions}.
3410 @cindex regular expression
3411 @cindex breakpoints at functions matching a regexp
3412 @cindex set breakpoints in many functions
3413 @item rbreak @var{regex}
3414 Set breakpoints on all functions matching the regular expression
3415 @var{regex}. This command sets an unconditional breakpoint on all
3416 matches, printing a list of all breakpoints it set. Once these
3417 breakpoints are set, they are treated just like the breakpoints set with
3418 the @code{break} command. You can delete them, disable them, or make
3419 them conditional the same way as any other breakpoint.
3421 The syntax of the regular expression is the standard one used with tools
3422 like @file{grep}. Note that this is different from the syntax used by
3423 shells, so for instance @code{foo*} matches all functions that include
3424 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3425 @code{.*} leading and trailing the regular expression you supply, so to
3426 match only functions that begin with @code{foo}, use @code{^foo}.
3428 @cindex non-member C@t{++} functions, set breakpoint in
3429 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3430 breakpoints on overloaded functions that are not members of any special
3433 @cindex set breakpoints on all functions
3434 The @code{rbreak} command can be used to set breakpoints in
3435 @strong{all} the functions in a program, like this:
3438 (@value{GDBP}) rbreak .
3441 @item rbreak @var{file}:@var{regex}
3442 If @code{rbreak} is called with a filename qualification, it limits
3443 the search for functions matching the given regular expression to the
3444 specified @var{file}. This can be used, for example, to set breakpoints on
3445 every function in a given file:
3448 (@value{GDBP}) rbreak file.c:.
3451 The colon separating the filename qualifier from the regex may
3452 optionally be surrounded by spaces.
3454 @kindex info breakpoints
3455 @cindex @code{$_} and @code{info breakpoints}
3456 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3457 @itemx info break @r{[}@var{n}@dots{}@r{]}
3458 Print a table of all breakpoints, watchpoints, and catchpoints set and
3459 not deleted. Optional argument @var{n} means print information only
3460 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3461 For each breakpoint, following columns are printed:
3464 @item Breakpoint Numbers
3466 Breakpoint, watchpoint, or catchpoint.
3468 Whether the breakpoint is marked to be disabled or deleted when hit.
3469 @item Enabled or Disabled
3470 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3471 that are not enabled.
3473 Where the breakpoint is in your program, as a memory address. For a
3474 pending breakpoint whose address is not yet known, this field will
3475 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3476 library that has the symbol or line referred by breakpoint is loaded.
3477 See below for details. A breakpoint with several locations will
3478 have @samp{<MULTIPLE>} in this field---see below for details.
3480 Where the breakpoint is in the source for your program, as a file and
3481 line number. For a pending breakpoint, the original string passed to
3482 the breakpoint command will be listed as it cannot be resolved until
3483 the appropriate shared library is loaded in the future.
3487 If a breakpoint is conditional, @code{info break} shows the condition on
3488 the line following the affected breakpoint; breakpoint commands, if any,
3489 are listed after that. A pending breakpoint is allowed to have a condition
3490 specified for it. The condition is not parsed for validity until a shared
3491 library is loaded that allows the pending breakpoint to resolve to a
3495 @code{info break} with a breakpoint
3496 number @var{n} as argument lists only that breakpoint. The
3497 convenience variable @code{$_} and the default examining-address for
3498 the @code{x} command are set to the address of the last breakpoint
3499 listed (@pxref{Memory, ,Examining Memory}).
3502 @code{info break} displays a count of the number of times the breakpoint
3503 has been hit. This is especially useful in conjunction with the
3504 @code{ignore} command. You can ignore a large number of breakpoint
3505 hits, look at the breakpoint info to see how many times the breakpoint
3506 was hit, and then run again, ignoring one less than that number. This
3507 will get you quickly to the last hit of that breakpoint.
3510 For a breakpoints with an enable count (xref) greater than 1,
3511 @code{info break} also displays that count.
3515 @value{GDBN} allows you to set any number of breakpoints at the same place in
3516 your program. There is nothing silly or meaningless about this. When
3517 the breakpoints are conditional, this is even useful
3518 (@pxref{Conditions, ,Break Conditions}).
3520 @cindex multiple locations, breakpoints
3521 @cindex breakpoints, multiple locations
3522 It is possible that a breakpoint corresponds to several locations
3523 in your program. Examples of this situation are:
3527 Multiple functions in the program may have the same name.
3530 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3531 instances of the function body, used in different cases.
3534 For a C@t{++} template function, a given line in the function can
3535 correspond to any number of instantiations.
3538 For an inlined function, a given source line can correspond to
3539 several places where that function is inlined.
3542 In all those cases, @value{GDBN} will insert a breakpoint at all
3543 the relevant locations.
3545 A breakpoint with multiple locations is displayed in the breakpoint
3546 table using several rows---one header row, followed by one row for
3547 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3548 address column. The rows for individual locations contain the actual
3549 addresses for locations, and show the functions to which those
3550 locations belong. The number column for a location is of the form
3551 @var{breakpoint-number}.@var{location-number}.
3556 Num Type Disp Enb Address What
3557 1 breakpoint keep y <MULTIPLE>
3559 breakpoint already hit 1 time
3560 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3561 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3564 Each location can be individually enabled or disabled by passing
3565 @var{breakpoint-number}.@var{location-number} as argument to the
3566 @code{enable} and @code{disable} commands. Note that you cannot
3567 delete the individual locations from the list, you can only delete the
3568 entire list of locations that belong to their parent breakpoint (with
3569 the @kbd{delete @var{num}} command, where @var{num} is the number of
3570 the parent breakpoint, 1 in the above example). Disabling or enabling
3571 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3572 that belong to that breakpoint.
3574 @cindex pending breakpoints
3575 It's quite common to have a breakpoint inside a shared library.
3576 Shared libraries can be loaded and unloaded explicitly,
3577 and possibly repeatedly, as the program is executed. To support
3578 this use case, @value{GDBN} updates breakpoint locations whenever
3579 any shared library is loaded or unloaded. Typically, you would
3580 set a breakpoint in a shared library at the beginning of your
3581 debugging session, when the library is not loaded, and when the
3582 symbols from the library are not available. When you try to set
3583 breakpoint, @value{GDBN} will ask you if you want to set
3584 a so called @dfn{pending breakpoint}---breakpoint whose address
3585 is not yet resolved.
3587 After the program is run, whenever a new shared library is loaded,
3588 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3589 shared library contains the symbol or line referred to by some
3590 pending breakpoint, that breakpoint is resolved and becomes an
3591 ordinary breakpoint. When a library is unloaded, all breakpoints
3592 that refer to its symbols or source lines become pending again.
3594 This logic works for breakpoints with multiple locations, too. For
3595 example, if you have a breakpoint in a C@t{++} template function, and
3596 a newly loaded shared library has an instantiation of that template,
3597 a new location is added to the list of locations for the breakpoint.
3599 Except for having unresolved address, pending breakpoints do not
3600 differ from regular breakpoints. You can set conditions or commands,
3601 enable and disable them and perform other breakpoint operations.
3603 @value{GDBN} provides some additional commands for controlling what
3604 happens when the @samp{break} command cannot resolve breakpoint
3605 address specification to an address:
3607 @kindex set breakpoint pending
3608 @kindex show breakpoint pending
3610 @item set breakpoint pending auto
3611 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3612 location, it queries you whether a pending breakpoint should be created.
3614 @item set breakpoint pending on
3615 This indicates that an unrecognized breakpoint location should automatically
3616 result in a pending breakpoint being created.
3618 @item set breakpoint pending off
3619 This indicates that pending breakpoints are not to be created. Any
3620 unrecognized breakpoint location results in an error. This setting does
3621 not affect any pending breakpoints previously created.
3623 @item show breakpoint pending
3624 Show the current behavior setting for creating pending breakpoints.
3627 The settings above only affect the @code{break} command and its
3628 variants. Once breakpoint is set, it will be automatically updated
3629 as shared libraries are loaded and unloaded.
3631 @cindex automatic hardware breakpoints
3632 For some targets, @value{GDBN} can automatically decide if hardware or
3633 software breakpoints should be used, depending on whether the
3634 breakpoint address is read-only or read-write. This applies to
3635 breakpoints set with the @code{break} command as well as to internal
3636 breakpoints set by commands like @code{next} and @code{finish}. For
3637 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3640 You can control this automatic behaviour with the following commands::
3642 @kindex set breakpoint auto-hw
3643 @kindex show breakpoint auto-hw
3645 @item set breakpoint auto-hw on
3646 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3647 will try to use the target memory map to decide if software or hardware
3648 breakpoint must be used.
3650 @item set breakpoint auto-hw off
3651 This indicates @value{GDBN} should not automatically select breakpoint
3652 type. If the target provides a memory map, @value{GDBN} will warn when
3653 trying to set software breakpoint at a read-only address.
3656 @value{GDBN} normally implements breakpoints by replacing the program code
3657 at the breakpoint address with a special instruction, which, when
3658 executed, given control to the debugger. By default, the program
3659 code is so modified only when the program is resumed. As soon as
3660 the program stops, @value{GDBN} restores the original instructions. This
3661 behaviour guards against leaving breakpoints inserted in the
3662 target should gdb abrubptly disconnect. However, with slow remote
3663 targets, inserting and removing breakpoint can reduce the performance.
3664 This behavior can be controlled with the following commands::
3666 @kindex set breakpoint always-inserted
3667 @kindex show breakpoint always-inserted
3669 @item set breakpoint always-inserted off
3670 All breakpoints, including newly added by the user, are inserted in
3671 the target only when the target is resumed. All breakpoints are
3672 removed from the target when it stops.
3674 @item set breakpoint always-inserted on
3675 Causes all breakpoints to be inserted in the target at all times. If
3676 the user adds a new breakpoint, or changes an existing breakpoint, the
3677 breakpoints in the target are updated immediately. A breakpoint is
3678 removed from the target only when breakpoint itself is removed.
3680 @cindex non-stop mode, and @code{breakpoint always-inserted}
3681 @item set breakpoint always-inserted auto
3682 This is the default mode. If @value{GDBN} is controlling the inferior
3683 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3684 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3685 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3686 @code{breakpoint always-inserted} mode is off.
3689 @cindex negative breakpoint numbers
3690 @cindex internal @value{GDBN} breakpoints
3691 @value{GDBN} itself sometimes sets breakpoints in your program for
3692 special purposes, such as proper handling of @code{longjmp} (in C
3693 programs). These internal breakpoints are assigned negative numbers,
3694 starting with @code{-1}; @samp{info breakpoints} does not display them.
3695 You can see these breakpoints with the @value{GDBN} maintenance command
3696 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3699 @node Set Watchpoints
3700 @subsection Setting Watchpoints
3702 @cindex setting watchpoints
3703 You can use a watchpoint to stop execution whenever the value of an
3704 expression changes, without having to predict a particular place where
3705 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3706 The expression may be as simple as the value of a single variable, or
3707 as complex as many variables combined by operators. Examples include:
3711 A reference to the value of a single variable.
3714 An address cast to an appropriate data type. For example,
3715 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3716 address (assuming an @code{int} occupies 4 bytes).
3719 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3720 expression can use any operators valid in the program's native
3721 language (@pxref{Languages}).
3724 You can set a watchpoint on an expression even if the expression can
3725 not be evaluated yet. For instance, you can set a watchpoint on
3726 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3727 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3728 the expression produces a valid value. If the expression becomes
3729 valid in some other way than changing a variable (e.g.@: if the memory
3730 pointed to by @samp{*global_ptr} becomes readable as the result of a
3731 @code{malloc} call), @value{GDBN} may not stop until the next time
3732 the expression changes.
3734 @cindex software watchpoints
3735 @cindex hardware watchpoints
3736 Depending on your system, watchpoints may be implemented in software or
3737 hardware. @value{GDBN} does software watchpointing by single-stepping your
3738 program and testing the variable's value each time, which is hundreds of
3739 times slower than normal execution. (But this may still be worth it, to
3740 catch errors where you have no clue what part of your program is the
3743 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3744 x86-based targets, @value{GDBN} includes support for hardware
3745 watchpoints, which do not slow down the running of your program.
3749 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3750 Set a watchpoint for an expression. @value{GDBN} will break when the
3751 expression @var{expr} is written into by the program and its value
3752 changes. The simplest (and the most popular) use of this command is
3753 to watch the value of a single variable:
3756 (@value{GDBP}) watch foo
3759 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3760 argument, @value{GDBN} breaks only when the thread identified by
3761 @var{threadnum} changes the value of @var{expr}. If any other threads
3762 change the value of @var{expr}, @value{GDBN} will not break. Note
3763 that watchpoints restricted to a single thread in this way only work
3764 with Hardware Watchpoints.
3766 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3767 (see below). The @code{-location} argument tells @value{GDBN} to
3768 instead watch the memory referred to by @var{expr}. In this case,
3769 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3770 and watch the memory at that address. The type of the result is used
3771 to determine the size of the watched memory. If the expression's
3772 result does not have an address, then @value{GDBN} will print an
3775 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3776 of masked watchpoints, if the current architecture supports this
3777 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3778 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3779 to an address to watch. The mask specifies that some bits of an address
3780 (the bits which are reset in the mask) should be ignored when matching
3781 the address accessed by the inferior against the watchpoint address.
3782 Thus, a masked watchpoint watches many addresses simultaneously---those
3783 addresses whose unmasked bits are identical to the unmasked bits in the
3784 watchpoint address. The @code{mask} argument implies @code{-location}.
3788 (@value{GDBP}) watch foo mask 0xffff00ff
3789 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3793 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3794 Set a watchpoint that will break when the value of @var{expr} is read
3798 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3799 Set a watchpoint that will break when @var{expr} is either read from
3800 or written into by the program.
3802 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3803 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3804 This command prints a list of watchpoints, using the same format as
3805 @code{info break} (@pxref{Set Breaks}).
3808 If you watch for a change in a numerically entered address you need to
3809 dereference it, as the address itself is just a constant number which will
3810 never change. @value{GDBN} refuses to create a watchpoint that watches
3811 a never-changing value:
3814 (@value{GDBP}) watch 0x600850
3815 Cannot watch constant value 0x600850.
3816 (@value{GDBP}) watch *(int *) 0x600850
3817 Watchpoint 1: *(int *) 6293584
3820 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3821 watchpoints execute very quickly, and the debugger reports a change in
3822 value at the exact instruction where the change occurs. If @value{GDBN}
3823 cannot set a hardware watchpoint, it sets a software watchpoint, which
3824 executes more slowly and reports the change in value at the next
3825 @emph{statement}, not the instruction, after the change occurs.
3827 @cindex use only software watchpoints
3828 You can force @value{GDBN} to use only software watchpoints with the
3829 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3830 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3831 the underlying system supports them. (Note that hardware-assisted
3832 watchpoints that were set @emph{before} setting
3833 @code{can-use-hw-watchpoints} to zero will still use the hardware
3834 mechanism of watching expression values.)
3837 @item set can-use-hw-watchpoints
3838 @kindex set can-use-hw-watchpoints
3839 Set whether or not to use hardware watchpoints.
3841 @item show can-use-hw-watchpoints
3842 @kindex show can-use-hw-watchpoints
3843 Show the current mode of using hardware watchpoints.
3846 For remote targets, you can restrict the number of hardware
3847 watchpoints @value{GDBN} will use, see @ref{set remote
3848 hardware-breakpoint-limit}.
3850 When you issue the @code{watch} command, @value{GDBN} reports
3853 Hardware watchpoint @var{num}: @var{expr}
3857 if it was able to set a hardware watchpoint.
3859 Currently, the @code{awatch} and @code{rwatch} commands can only set
3860 hardware watchpoints, because accesses to data that don't change the
3861 value of the watched expression cannot be detected without examining
3862 every instruction as it is being executed, and @value{GDBN} does not do
3863 that currently. If @value{GDBN} finds that it is unable to set a
3864 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3865 will print a message like this:
3868 Expression cannot be implemented with read/access watchpoint.
3871 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3872 data type of the watched expression is wider than what a hardware
3873 watchpoint on the target machine can handle. For example, some systems
3874 can only watch regions that are up to 4 bytes wide; on such systems you
3875 cannot set hardware watchpoints for an expression that yields a
3876 double-precision floating-point number (which is typically 8 bytes
3877 wide). As a work-around, it might be possible to break the large region
3878 into a series of smaller ones and watch them with separate watchpoints.
3880 If you set too many hardware watchpoints, @value{GDBN} might be unable
3881 to insert all of them when you resume the execution of your program.
3882 Since the precise number of active watchpoints is unknown until such
3883 time as the program is about to be resumed, @value{GDBN} might not be
3884 able to warn you about this when you set the watchpoints, and the
3885 warning will be printed only when the program is resumed:
3888 Hardware watchpoint @var{num}: Could not insert watchpoint
3892 If this happens, delete or disable some of the watchpoints.
3894 Watching complex expressions that reference many variables can also
3895 exhaust the resources available for hardware-assisted watchpoints.
3896 That's because @value{GDBN} needs to watch every variable in the
3897 expression with separately allocated resources.
3899 If you call a function interactively using @code{print} or @code{call},
3900 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3901 kind of breakpoint or the call completes.
3903 @value{GDBN} automatically deletes watchpoints that watch local
3904 (automatic) variables, or expressions that involve such variables, when
3905 they go out of scope, that is, when the execution leaves the block in
3906 which these variables were defined. In particular, when the program
3907 being debugged terminates, @emph{all} local variables go out of scope,
3908 and so only watchpoints that watch global variables remain set. If you
3909 rerun the program, you will need to set all such watchpoints again. One
3910 way of doing that would be to set a code breakpoint at the entry to the
3911 @code{main} function and when it breaks, set all the watchpoints.
3913 @cindex watchpoints and threads
3914 @cindex threads and watchpoints
3915 In multi-threaded programs, watchpoints will detect changes to the
3916 watched expression from every thread.
3919 @emph{Warning:} In multi-threaded programs, software watchpoints
3920 have only limited usefulness. If @value{GDBN} creates a software
3921 watchpoint, it can only watch the value of an expression @emph{in a
3922 single thread}. If you are confident that the expression can only
3923 change due to the current thread's activity (and if you are also
3924 confident that no other thread can become current), then you can use
3925 software watchpoints as usual. However, @value{GDBN} may not notice
3926 when a non-current thread's activity changes the expression. (Hardware
3927 watchpoints, in contrast, watch an expression in all threads.)
3930 @xref{set remote hardware-watchpoint-limit}.
3932 @node Set Catchpoints
3933 @subsection Setting Catchpoints
3934 @cindex catchpoints, setting
3935 @cindex exception handlers
3936 @cindex event handling
3938 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3939 kinds of program events, such as C@t{++} exceptions or the loading of a
3940 shared library. Use the @code{catch} command to set a catchpoint.
3944 @item catch @var{event}
3945 Stop when @var{event} occurs. @var{event} can be any of the following:
3948 @cindex stop on C@t{++} exceptions
3949 The throwing of a C@t{++} exception.
3952 The catching of a C@t{++} exception.
3955 @cindex Ada exception catching
3956 @cindex catch Ada exceptions
3957 An Ada exception being raised. If an exception name is specified
3958 at the end of the command (eg @code{catch exception Program_Error}),
3959 the debugger will stop only when this specific exception is raised.
3960 Otherwise, the debugger stops execution when any Ada exception is raised.
3962 When inserting an exception catchpoint on a user-defined exception whose
3963 name is identical to one of the exceptions defined by the language, the
3964 fully qualified name must be used as the exception name. Otherwise,
3965 @value{GDBN} will assume that it should stop on the pre-defined exception
3966 rather than the user-defined one. For instance, assuming an exception
3967 called @code{Constraint_Error} is defined in package @code{Pck}, then
3968 the command to use to catch such exceptions is @kbd{catch exception
3969 Pck.Constraint_Error}.
3971 @item exception unhandled
3972 An exception that was raised but is not handled by the program.
3975 A failed Ada assertion.
3978 @cindex break on fork/exec
3979 A call to @code{exec}. This is currently only available for HP-UX
3983 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3984 @cindex break on a system call.
3985 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3986 syscall is a mechanism for application programs to request a service
3987 from the operating system (OS) or one of the OS system services.
3988 @value{GDBN} can catch some or all of the syscalls issued by the
3989 debuggee, and show the related information for each syscall. If no
3990 argument is specified, calls to and returns from all system calls
3993 @var{name} can be any system call name that is valid for the
3994 underlying OS. Just what syscalls are valid depends on the OS. On
3995 GNU and Unix systems, you can find the full list of valid syscall
3996 names on @file{/usr/include/asm/unistd.h}.
3998 @c For MS-Windows, the syscall names and the corresponding numbers
3999 @c can be found, e.g., on this URL:
4000 @c http://www.metasploit.com/users/opcode/syscalls.html
4001 @c but we don't support Windows syscalls yet.
4003 Normally, @value{GDBN} knows in advance which syscalls are valid for
4004 each OS, so you can use the @value{GDBN} command-line completion
4005 facilities (@pxref{Completion,, command completion}) to list the
4008 You may also specify the system call numerically. A syscall's
4009 number is the value passed to the OS's syscall dispatcher to
4010 identify the requested service. When you specify the syscall by its
4011 name, @value{GDBN} uses its database of syscalls to convert the name
4012 into the corresponding numeric code, but using the number directly
4013 may be useful if @value{GDBN}'s database does not have the complete
4014 list of syscalls on your system (e.g., because @value{GDBN} lags
4015 behind the OS upgrades).
4017 The example below illustrates how this command works if you don't provide
4021 (@value{GDBP}) catch syscall
4022 Catchpoint 1 (syscall)
4024 Starting program: /tmp/catch-syscall
4026 Catchpoint 1 (call to syscall 'close'), \
4027 0xffffe424 in __kernel_vsyscall ()
4031 Catchpoint 1 (returned from syscall 'close'), \
4032 0xffffe424 in __kernel_vsyscall ()
4036 Here is an example of catching a system call by name:
4039 (@value{GDBP}) catch syscall chroot
4040 Catchpoint 1 (syscall 'chroot' [61])
4042 Starting program: /tmp/catch-syscall
4044 Catchpoint 1 (call to syscall 'chroot'), \
4045 0xffffe424 in __kernel_vsyscall ()
4049 Catchpoint 1 (returned from syscall 'chroot'), \
4050 0xffffe424 in __kernel_vsyscall ()
4054 An example of specifying a system call numerically. In the case
4055 below, the syscall number has a corresponding entry in the XML
4056 file, so @value{GDBN} finds its name and prints it:
4059 (@value{GDBP}) catch syscall 252
4060 Catchpoint 1 (syscall(s) 'exit_group')
4062 Starting program: /tmp/catch-syscall
4064 Catchpoint 1 (call to syscall 'exit_group'), \
4065 0xffffe424 in __kernel_vsyscall ()
4069 Program exited normally.
4073 However, there can be situations when there is no corresponding name
4074 in XML file for that syscall number. In this case, @value{GDBN} prints
4075 a warning message saying that it was not able to find the syscall name,
4076 but the catchpoint will be set anyway. See the example below:
4079 (@value{GDBP}) catch syscall 764
4080 warning: The number '764' does not represent a known syscall.
4081 Catchpoint 2 (syscall 764)
4085 If you configure @value{GDBN} using the @samp{--without-expat} option,
4086 it will not be able to display syscall names. Also, if your
4087 architecture does not have an XML file describing its system calls,
4088 you will not be able to see the syscall names. It is important to
4089 notice that these two features are used for accessing the syscall
4090 name database. In either case, you will see a warning like this:
4093 (@value{GDBP}) catch syscall
4094 warning: Could not open "syscalls/i386-linux.xml"
4095 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4096 GDB will not be able to display syscall names.
4097 Catchpoint 1 (syscall)
4101 Of course, the file name will change depending on your architecture and system.
4103 Still using the example above, you can also try to catch a syscall by its
4104 number. In this case, you would see something like:
4107 (@value{GDBP}) catch syscall 252
4108 Catchpoint 1 (syscall(s) 252)
4111 Again, in this case @value{GDBN} would not be able to display syscall's names.
4114 A call to @code{fork}. This is currently only available for HP-UX
4118 A call to @code{vfork}. This is currently only available for HP-UX
4121 @item load @r{[}regexp@r{]}
4122 @itemx unload @r{[}regexp@r{]}
4123 The loading or unloading of a shared library. If @var{regexp} is
4124 given, then the catchpoint will stop only if the regular expression
4125 matches one of the affected libraries.
4129 @item tcatch @var{event}
4130 Set a catchpoint that is enabled only for one stop. The catchpoint is
4131 automatically deleted after the first time the event is caught.
4135 Use the @code{info break} command to list the current catchpoints.
4137 There are currently some limitations to C@t{++} exception handling
4138 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4142 If you call a function interactively, @value{GDBN} normally returns
4143 control to you when the function has finished executing. If the call
4144 raises an exception, however, the call may bypass the mechanism that
4145 returns control to you and cause your program either to abort or to
4146 simply continue running until it hits a breakpoint, catches a signal
4147 that @value{GDBN} is listening for, or exits. This is the case even if
4148 you set a catchpoint for the exception; catchpoints on exceptions are
4149 disabled within interactive calls.
4152 You cannot raise an exception interactively.
4155 You cannot install an exception handler interactively.
4158 @cindex raise exceptions
4159 Sometimes @code{catch} is not the best way to debug exception handling:
4160 if you need to know exactly where an exception is raised, it is better to
4161 stop @emph{before} the exception handler is called, since that way you
4162 can see the stack before any unwinding takes place. If you set a
4163 breakpoint in an exception handler instead, it may not be easy to find
4164 out where the exception was raised.
4166 To stop just before an exception handler is called, you need some
4167 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4168 raised by calling a library function named @code{__raise_exception}
4169 which has the following ANSI C interface:
4172 /* @var{addr} is where the exception identifier is stored.
4173 @var{id} is the exception identifier. */
4174 void __raise_exception (void **addr, void *id);
4178 To make the debugger catch all exceptions before any stack
4179 unwinding takes place, set a breakpoint on @code{__raise_exception}
4180 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4182 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4183 that depends on the value of @var{id}, you can stop your program when
4184 a specific exception is raised. You can use multiple conditional
4185 breakpoints to stop your program when any of a number of exceptions are
4190 @subsection Deleting Breakpoints
4192 @cindex clearing breakpoints, watchpoints, catchpoints
4193 @cindex deleting breakpoints, watchpoints, catchpoints
4194 It is often necessary to eliminate a breakpoint, watchpoint, or
4195 catchpoint once it has done its job and you no longer want your program
4196 to stop there. This is called @dfn{deleting} the breakpoint. A
4197 breakpoint that has been deleted no longer exists; it is forgotten.
4199 With the @code{clear} command you can delete breakpoints according to
4200 where they are in your program. With the @code{delete} command you can
4201 delete individual breakpoints, watchpoints, or catchpoints by specifying
4202 their breakpoint numbers.
4204 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4205 automatically ignores breakpoints on the first instruction to be executed
4206 when you continue execution without changing the execution address.
4211 Delete any breakpoints at the next instruction to be executed in the
4212 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4213 the innermost frame is selected, this is a good way to delete a
4214 breakpoint where your program just stopped.
4216 @item clear @var{location}
4217 Delete any breakpoints set at the specified @var{location}.
4218 @xref{Specify Location}, for the various forms of @var{location}; the
4219 most useful ones are listed below:
4222 @item clear @var{function}
4223 @itemx clear @var{filename}:@var{function}
4224 Delete any breakpoints set at entry to the named @var{function}.
4226 @item clear @var{linenum}
4227 @itemx clear @var{filename}:@var{linenum}
4228 Delete any breakpoints set at or within the code of the specified
4229 @var{linenum} of the specified @var{filename}.
4232 @cindex delete breakpoints
4234 @kindex d @r{(@code{delete})}
4235 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4236 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4237 ranges specified as arguments. If no argument is specified, delete all
4238 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4239 confirm off}). You can abbreviate this command as @code{d}.
4243 @subsection Disabling Breakpoints
4245 @cindex enable/disable a breakpoint
4246 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4247 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4248 it had been deleted, but remembers the information on the breakpoint so
4249 that you can @dfn{enable} it again later.
4251 You disable and enable breakpoints, watchpoints, and catchpoints with
4252 the @code{enable} and @code{disable} commands, optionally specifying
4253 one or more breakpoint numbers as arguments. Use @code{info break} to
4254 print a list of all breakpoints, watchpoints, and catchpoints if you
4255 do not know which numbers to use.
4257 Disabling and enabling a breakpoint that has multiple locations
4258 affects all of its locations.
4260 A breakpoint, watchpoint, or catchpoint can have any of several
4261 different states of enablement:
4265 Enabled. The breakpoint stops your program. A breakpoint set
4266 with the @code{break} command starts out in this state.
4268 Disabled. The breakpoint has no effect on your program.
4270 Enabled once. The breakpoint stops your program, but then becomes
4273 Enabled for a count. The breakpoint stops your program for the next
4274 N times, then becomes disabled.
4276 Enabled for deletion. The breakpoint stops your program, but
4277 immediately after it does so it is deleted permanently. A breakpoint
4278 set with the @code{tbreak} command starts out in this state.
4281 You can use the following commands to enable or disable breakpoints,
4282 watchpoints, and catchpoints:
4286 @kindex dis @r{(@code{disable})}
4287 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4288 Disable the specified breakpoints---or all breakpoints, if none are
4289 listed. A disabled breakpoint has no effect but is not forgotten. All
4290 options such as ignore-counts, conditions and commands are remembered in
4291 case the breakpoint is enabled again later. You may abbreviate
4292 @code{disable} as @code{dis}.
4295 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4296 Enable the specified breakpoints (or all defined breakpoints). They
4297 become effective once again in stopping your program.
4299 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4300 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4301 of these breakpoints immediately after stopping your program.
4303 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4304 Enable the specified breakpoints temporarily. @value{GDBN} records
4305 @var{count} with each of the specified breakpoints, and decrements a
4306 breakpoint's count when it is hit. When any count reaches 0,
4307 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4308 count (@pxref{Conditions, ,Break Conditions}), that will be
4309 decremented to 0 before @var{count} is affected.
4311 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4312 Enable the specified breakpoints to work once, then die. @value{GDBN}
4313 deletes any of these breakpoints as soon as your program stops there.
4314 Breakpoints set by the @code{tbreak} command start out in this state.
4317 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4318 @c confusing: tbreak is also initially enabled.
4319 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4320 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4321 subsequently, they become disabled or enabled only when you use one of
4322 the commands above. (The command @code{until} can set and delete a
4323 breakpoint of its own, but it does not change the state of your other
4324 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4328 @subsection Break Conditions
4329 @cindex conditional breakpoints
4330 @cindex breakpoint conditions
4332 @c FIXME what is scope of break condition expr? Context where wanted?
4333 @c in particular for a watchpoint?
4334 The simplest sort of breakpoint breaks every time your program reaches a
4335 specified place. You can also specify a @dfn{condition} for a
4336 breakpoint. A condition is just a Boolean expression in your
4337 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4338 a condition evaluates the expression each time your program reaches it,
4339 and your program stops only if the condition is @emph{true}.
4341 This is the converse of using assertions for program validation; in that
4342 situation, you want to stop when the assertion is violated---that is,
4343 when the condition is false. In C, if you want to test an assertion expressed
4344 by the condition @var{assert}, you should set the condition
4345 @samp{! @var{assert}} on the appropriate breakpoint.
4347 Conditions are also accepted for watchpoints; you may not need them,
4348 since a watchpoint is inspecting the value of an expression anyhow---but
4349 it might be simpler, say, to just set a watchpoint on a variable name,
4350 and specify a condition that tests whether the new value is an interesting
4353 Break conditions can have side effects, and may even call functions in
4354 your program. This can be useful, for example, to activate functions
4355 that log program progress, or to use your own print functions to
4356 format special data structures. The effects are completely predictable
4357 unless there is another enabled breakpoint at the same address. (In
4358 that case, @value{GDBN} might see the other breakpoint first and stop your
4359 program without checking the condition of this one.) Note that
4360 breakpoint commands are usually more convenient and flexible than break
4362 purpose of performing side effects when a breakpoint is reached
4363 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4365 Break conditions can be specified when a breakpoint is set, by using
4366 @samp{if} in the arguments to the @code{break} command. @xref{Set
4367 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4368 with the @code{condition} command.
4370 You can also use the @code{if} keyword with the @code{watch} command.
4371 The @code{catch} command does not recognize the @code{if} keyword;
4372 @code{condition} is the only way to impose a further condition on a
4377 @item condition @var{bnum} @var{expression}
4378 Specify @var{expression} as the break condition for breakpoint,
4379 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4380 breakpoint @var{bnum} stops your program only if the value of
4381 @var{expression} is true (nonzero, in C). When you use
4382 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4383 syntactic correctness, and to determine whether symbols in it have
4384 referents in the context of your breakpoint. If @var{expression} uses
4385 symbols not referenced in the context of the breakpoint, @value{GDBN}
4386 prints an error message:
4389 No symbol "foo" in current context.
4394 not actually evaluate @var{expression} at the time the @code{condition}
4395 command (or a command that sets a breakpoint with a condition, like
4396 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4398 @item condition @var{bnum}
4399 Remove the condition from breakpoint number @var{bnum}. It becomes
4400 an ordinary unconditional breakpoint.
4403 @cindex ignore count (of breakpoint)
4404 A special case of a breakpoint condition is to stop only when the
4405 breakpoint has been reached a certain number of times. This is so
4406 useful that there is a special way to do it, using the @dfn{ignore
4407 count} of the breakpoint. Every breakpoint has an ignore count, which
4408 is an integer. Most of the time, the ignore count is zero, and
4409 therefore has no effect. But if your program reaches a breakpoint whose
4410 ignore count is positive, then instead of stopping, it just decrements
4411 the ignore count by one and continues. As a result, if the ignore count
4412 value is @var{n}, the breakpoint does not stop the next @var{n} times
4413 your program reaches it.
4417 @item ignore @var{bnum} @var{count}
4418 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4419 The next @var{count} times the breakpoint is reached, your program's
4420 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4423 To make the breakpoint stop the next time it is reached, specify
4426 When you use @code{continue} to resume execution of your program from a
4427 breakpoint, you can specify an ignore count directly as an argument to
4428 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4429 Stepping,,Continuing and Stepping}.
4431 If a breakpoint has a positive ignore count and a condition, the
4432 condition is not checked. Once the ignore count reaches zero,
4433 @value{GDBN} resumes checking the condition.
4435 You could achieve the effect of the ignore count with a condition such
4436 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4437 is decremented each time. @xref{Convenience Vars, ,Convenience
4441 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4444 @node Break Commands
4445 @subsection Breakpoint Command Lists
4447 @cindex breakpoint commands
4448 You can give any breakpoint (or watchpoint or catchpoint) a series of
4449 commands to execute when your program stops due to that breakpoint. For
4450 example, you might want to print the values of certain expressions, or
4451 enable other breakpoints.
4455 @kindex end@r{ (breakpoint commands)}
4456 @item commands @r{[}@var{range}@dots{}@r{]}
4457 @itemx @dots{} @var{command-list} @dots{}
4459 Specify a list of commands for the given breakpoints. The commands
4460 themselves appear on the following lines. Type a line containing just
4461 @code{end} to terminate the commands.
4463 To remove all commands from a breakpoint, type @code{commands} and
4464 follow it immediately with @code{end}; that is, give no commands.
4466 With no argument, @code{commands} refers to the last breakpoint,
4467 watchpoint, or catchpoint set (not to the breakpoint most recently
4468 encountered). If the most recent breakpoints were set with a single
4469 command, then the @code{commands} will apply to all the breakpoints
4470 set by that command. This applies to breakpoints set by
4471 @code{rbreak}, and also applies when a single @code{break} command
4472 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4476 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4477 disabled within a @var{command-list}.
4479 You can use breakpoint commands to start your program up again. Simply
4480 use the @code{continue} command, or @code{step}, or any other command
4481 that resumes execution.
4483 Any other commands in the command list, after a command that resumes
4484 execution, are ignored. This is because any time you resume execution
4485 (even with a simple @code{next} or @code{step}), you may encounter
4486 another breakpoint---which could have its own command list, leading to
4487 ambiguities about which list to execute.
4490 If the first command you specify in a command list is @code{silent}, the
4491 usual message about stopping at a breakpoint is not printed. This may
4492 be desirable for breakpoints that are to print a specific message and
4493 then continue. If none of the remaining commands print anything, you
4494 see no sign that the breakpoint was reached. @code{silent} is
4495 meaningful only at the beginning of a breakpoint command list.
4497 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4498 print precisely controlled output, and are often useful in silent
4499 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4501 For example, here is how you could use breakpoint commands to print the
4502 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4508 printf "x is %d\n",x
4513 One application for breakpoint commands is to compensate for one bug so
4514 you can test for another. Put a breakpoint just after the erroneous line
4515 of code, give it a condition to detect the case in which something
4516 erroneous has been done, and give it commands to assign correct values
4517 to any variables that need them. End with the @code{continue} command
4518 so that your program does not stop, and start with the @code{silent}
4519 command so that no output is produced. Here is an example:
4530 @node Save Breakpoints
4531 @subsection How to save breakpoints to a file
4533 To save breakpoint definitions to a file use the @w{@code{save
4534 breakpoints}} command.
4537 @kindex save breakpoints
4538 @cindex save breakpoints to a file for future sessions
4539 @item save breakpoints [@var{filename}]
4540 This command saves all current breakpoint definitions together with
4541 their commands and ignore counts, into a file @file{@var{filename}}
4542 suitable for use in a later debugging session. This includes all
4543 types of breakpoints (breakpoints, watchpoints, catchpoints,
4544 tracepoints). To read the saved breakpoint definitions, use the
4545 @code{source} command (@pxref{Command Files}). Note that watchpoints
4546 with expressions involving local variables may fail to be recreated
4547 because it may not be possible to access the context where the
4548 watchpoint is valid anymore. Because the saved breakpoint definitions
4549 are simply a sequence of @value{GDBN} commands that recreate the
4550 breakpoints, you can edit the file in your favorite editing program,
4551 and remove the breakpoint definitions you're not interested in, or
4552 that can no longer be recreated.
4555 @c @ifclear BARETARGET
4556 @node Error in Breakpoints
4557 @subsection ``Cannot insert breakpoints''
4559 If you request too many active hardware-assisted breakpoints and
4560 watchpoints, you will see this error message:
4562 @c FIXME: the precise wording of this message may change; the relevant
4563 @c source change is not committed yet (Sep 3, 1999).
4565 Stopped; cannot insert breakpoints.
4566 You may have requested too many hardware breakpoints and watchpoints.
4570 This message is printed when you attempt to resume the program, since
4571 only then @value{GDBN} knows exactly how many hardware breakpoints and
4572 watchpoints it needs to insert.
4574 When this message is printed, you need to disable or remove some of the
4575 hardware-assisted breakpoints and watchpoints, and then continue.
4577 @node Breakpoint-related Warnings
4578 @subsection ``Breakpoint address adjusted...''
4579 @cindex breakpoint address adjusted
4581 Some processor architectures place constraints on the addresses at
4582 which breakpoints may be placed. For architectures thus constrained,
4583 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4584 with the constraints dictated by the architecture.
4586 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4587 a VLIW architecture in which a number of RISC-like instructions may be
4588 bundled together for parallel execution. The FR-V architecture
4589 constrains the location of a breakpoint instruction within such a
4590 bundle to the instruction with the lowest address. @value{GDBN}
4591 honors this constraint by adjusting a breakpoint's address to the
4592 first in the bundle.
4594 It is not uncommon for optimized code to have bundles which contain
4595 instructions from different source statements, thus it may happen that
4596 a breakpoint's address will be adjusted from one source statement to
4597 another. Since this adjustment may significantly alter @value{GDBN}'s
4598 breakpoint related behavior from what the user expects, a warning is
4599 printed when the breakpoint is first set and also when the breakpoint
4602 A warning like the one below is printed when setting a breakpoint
4603 that's been subject to address adjustment:
4606 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4609 Such warnings are printed both for user settable and @value{GDBN}'s
4610 internal breakpoints. If you see one of these warnings, you should
4611 verify that a breakpoint set at the adjusted address will have the
4612 desired affect. If not, the breakpoint in question may be removed and
4613 other breakpoints may be set which will have the desired behavior.
4614 E.g., it may be sufficient to place the breakpoint at a later
4615 instruction. A conditional breakpoint may also be useful in some
4616 cases to prevent the breakpoint from triggering too often.
4618 @value{GDBN} will also issue a warning when stopping at one of these
4619 adjusted breakpoints:
4622 warning: Breakpoint 1 address previously adjusted from 0x00010414
4626 When this warning is encountered, it may be too late to take remedial
4627 action except in cases where the breakpoint is hit earlier or more
4628 frequently than expected.
4630 @node Continuing and Stepping
4631 @section Continuing and Stepping
4635 @cindex resuming execution
4636 @dfn{Continuing} means resuming program execution until your program
4637 completes normally. In contrast, @dfn{stepping} means executing just
4638 one more ``step'' of your program, where ``step'' may mean either one
4639 line of source code, or one machine instruction (depending on what
4640 particular command you use). Either when continuing or when stepping,
4641 your program may stop even sooner, due to a breakpoint or a signal. (If
4642 it stops due to a signal, you may want to use @code{handle}, or use
4643 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4647 @kindex c @r{(@code{continue})}
4648 @kindex fg @r{(resume foreground execution)}
4649 @item continue @r{[}@var{ignore-count}@r{]}
4650 @itemx c @r{[}@var{ignore-count}@r{]}
4651 @itemx fg @r{[}@var{ignore-count}@r{]}
4652 Resume program execution, at the address where your program last stopped;
4653 any breakpoints set at that address are bypassed. The optional argument
4654 @var{ignore-count} allows you to specify a further number of times to
4655 ignore a breakpoint at this location; its effect is like that of
4656 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4658 The argument @var{ignore-count} is meaningful only when your program
4659 stopped due to a breakpoint. At other times, the argument to
4660 @code{continue} is ignored.
4662 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4663 debugged program is deemed to be the foreground program) are provided
4664 purely for convenience, and have exactly the same behavior as
4668 To resume execution at a different place, you can use @code{return}
4669 (@pxref{Returning, ,Returning from a Function}) to go back to the
4670 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4671 Different Address}) to go to an arbitrary location in your program.
4673 A typical technique for using stepping is to set a breakpoint
4674 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4675 beginning of the function or the section of your program where a problem
4676 is believed to lie, run your program until it stops at that breakpoint,
4677 and then step through the suspect area, examining the variables that are
4678 interesting, until you see the problem happen.
4682 @kindex s @r{(@code{step})}
4684 Continue running your program until control reaches a different source
4685 line, then stop it and return control to @value{GDBN}. This command is
4686 abbreviated @code{s}.
4689 @c "without debugging information" is imprecise; actually "without line
4690 @c numbers in the debugging information". (gcc -g1 has debugging info but
4691 @c not line numbers). But it seems complex to try to make that
4692 @c distinction here.
4693 @emph{Warning:} If you use the @code{step} command while control is
4694 within a function that was compiled without debugging information,
4695 execution proceeds until control reaches a function that does have
4696 debugging information. Likewise, it will not step into a function which
4697 is compiled without debugging information. To step through functions
4698 without debugging information, use the @code{stepi} command, described
4702 The @code{step} command only stops at the first instruction of a source
4703 line. This prevents the multiple stops that could otherwise occur in
4704 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4705 to stop if a function that has debugging information is called within
4706 the line. In other words, @code{step} @emph{steps inside} any functions
4707 called within the line.
4709 Also, the @code{step} command only enters a function if there is line
4710 number information for the function. Otherwise it acts like the
4711 @code{next} command. This avoids problems when using @code{cc -gl}
4712 on MIPS machines. Previously, @code{step} entered subroutines if there
4713 was any debugging information about the routine.
4715 @item step @var{count}
4716 Continue running as in @code{step}, but do so @var{count} times. If a
4717 breakpoint is reached, or a signal not related to stepping occurs before
4718 @var{count} steps, stepping stops right away.
4721 @kindex n @r{(@code{next})}
4722 @item next @r{[}@var{count}@r{]}
4723 Continue to the next source line in the current (innermost) stack frame.
4724 This is similar to @code{step}, but function calls that appear within
4725 the line of code are executed without stopping. Execution stops when
4726 control reaches a different line of code at the original stack level
4727 that was executing when you gave the @code{next} command. This command
4728 is abbreviated @code{n}.
4730 An argument @var{count} is a repeat count, as for @code{step}.
4733 @c FIX ME!! Do we delete this, or is there a way it fits in with
4734 @c the following paragraph? --- Vctoria
4736 @c @code{next} within a function that lacks debugging information acts like
4737 @c @code{step}, but any function calls appearing within the code of the
4738 @c function are executed without stopping.
4740 The @code{next} command only stops at the first instruction of a
4741 source line. This prevents multiple stops that could otherwise occur in
4742 @code{switch} statements, @code{for} loops, etc.
4744 @kindex set step-mode
4746 @cindex functions without line info, and stepping
4747 @cindex stepping into functions with no line info
4748 @itemx set step-mode on
4749 The @code{set step-mode on} command causes the @code{step} command to
4750 stop at the first instruction of a function which contains no debug line
4751 information rather than stepping over it.
4753 This is useful in cases where you may be interested in inspecting the
4754 machine instructions of a function which has no symbolic info and do not
4755 want @value{GDBN} to automatically skip over this function.
4757 @item set step-mode off
4758 Causes the @code{step} command to step over any functions which contains no
4759 debug information. This is the default.
4761 @item show step-mode
4762 Show whether @value{GDBN} will stop in or step over functions without
4763 source line debug information.
4766 @kindex fin @r{(@code{finish})}
4768 Continue running until just after function in the selected stack frame
4769 returns. Print the returned value (if any). This command can be
4770 abbreviated as @code{fin}.
4772 Contrast this with the @code{return} command (@pxref{Returning,
4773 ,Returning from a Function}).
4776 @kindex u @r{(@code{until})}
4777 @cindex run until specified location
4780 Continue running until a source line past the current line, in the
4781 current stack frame, is reached. This command is used to avoid single
4782 stepping through a loop more than once. It is like the @code{next}
4783 command, except that when @code{until} encounters a jump, it
4784 automatically continues execution until the program counter is greater
4785 than the address of the jump.
4787 This means that when you reach the end of a loop after single stepping
4788 though it, @code{until} makes your program continue execution until it
4789 exits the loop. In contrast, a @code{next} command at the end of a loop
4790 simply steps back to the beginning of the loop, which forces you to step
4791 through the next iteration.
4793 @code{until} always stops your program if it attempts to exit the current
4796 @code{until} may produce somewhat counterintuitive results if the order
4797 of machine code does not match the order of the source lines. For
4798 example, in the following excerpt from a debugging session, the @code{f}
4799 (@code{frame}) command shows that execution is stopped at line
4800 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4804 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4806 (@value{GDBP}) until
4807 195 for ( ; argc > 0; NEXTARG) @{
4810 This happened because, for execution efficiency, the compiler had
4811 generated code for the loop closure test at the end, rather than the
4812 start, of the loop---even though the test in a C @code{for}-loop is
4813 written before the body of the loop. The @code{until} command appeared
4814 to step back to the beginning of the loop when it advanced to this
4815 expression; however, it has not really gone to an earlier
4816 statement---not in terms of the actual machine code.
4818 @code{until} with no argument works by means of single
4819 instruction stepping, and hence is slower than @code{until} with an
4822 @item until @var{location}
4823 @itemx u @var{location}
4824 Continue running your program until either the specified location is
4825 reached, or the current stack frame returns. @var{location} is any of
4826 the forms described in @ref{Specify Location}.
4827 This form of the command uses temporary breakpoints, and
4828 hence is quicker than @code{until} without an argument. The specified
4829 location is actually reached only if it is in the current frame. This
4830 implies that @code{until} can be used to skip over recursive function
4831 invocations. For instance in the code below, if the current location is
4832 line @code{96}, issuing @code{until 99} will execute the program up to
4833 line @code{99} in the same invocation of factorial, i.e., after the inner
4834 invocations have returned.
4837 94 int factorial (int value)
4839 96 if (value > 1) @{
4840 97 value *= factorial (value - 1);
4847 @kindex advance @var{location}
4848 @itemx advance @var{location}
4849 Continue running the program up to the given @var{location}. An argument is
4850 required, which should be of one of the forms described in
4851 @ref{Specify Location}.
4852 Execution will also stop upon exit from the current stack
4853 frame. This command is similar to @code{until}, but @code{advance} will
4854 not skip over recursive function calls, and the target location doesn't
4855 have to be in the same frame as the current one.
4859 @kindex si @r{(@code{stepi})}
4861 @itemx stepi @var{arg}
4863 Execute one machine instruction, then stop and return to the debugger.
4865 It is often useful to do @samp{display/i $pc} when stepping by machine
4866 instructions. This makes @value{GDBN} automatically display the next
4867 instruction to be executed, each time your program stops. @xref{Auto
4868 Display,, Automatic Display}.
4870 An argument is a repeat count, as in @code{step}.
4874 @kindex ni @r{(@code{nexti})}
4876 @itemx nexti @var{arg}
4878 Execute one machine instruction, but if it is a function call,
4879 proceed until the function returns.
4881 An argument is a repeat count, as in @code{next}.
4884 @node Skipping Over Functions and Files
4885 @section Skipping Over Functions and Files
4886 @cindex skipping over functions and files
4888 The program you are debugging may contain some functions which are
4889 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4890 skip a function or all functions in a file when stepping.
4892 For example, consider the following C function:
4903 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4904 are not interested in stepping through @code{boring}. If you run @code{step}
4905 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4906 step over both @code{foo} and @code{boring}!
4908 One solution is to @code{step} into @code{boring} and use the @code{finish}
4909 command to immediately exit it. But this can become tedious if @code{boring}
4910 is called from many places.
4912 A more flexible solution is to execute @kbd{skip boring}. This instructs
4913 @value{GDBN} never to step into @code{boring}. Now when you execute
4914 @code{step} at line 103, you'll step over @code{boring} and directly into
4917 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4918 example, @code{skip file boring.c}.
4921 @kindex skip function
4922 @item skip @r{[}@var{linespec}@r{]}
4923 @itemx skip function @r{[}@var{linespec}@r{]}
4924 After running this command, the function named by @var{linespec} or the
4925 function containing the line named by @var{linespec} will be skipped over when
4926 stepping. @xref{Specify Location}.
4928 If you do not specify @var{linespec}, the function you're currently debugging
4931 (If you have a function called @code{file} that you want to skip, use
4932 @kbd{skip function file}.)
4935 @item skip file @r{[}@var{filename}@r{]}
4936 After running this command, any function whose source lives in @var{filename}
4937 will be skipped over when stepping.
4939 If you do not specify @var{filename}, functions whose source lives in the file
4940 you're currently debugging will be skipped.
4943 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4944 These are the commands for managing your list of skips:
4948 @item info skip @r{[}@var{range}@r{]}
4949 Print details about the specified skip(s). If @var{range} is not specified,
4950 print a table with details about all functions and files marked for skipping.
4951 @code{info skip} prints the following information about each skip:
4955 A number identifying this skip.
4957 The type of this skip, either @samp{function} or @samp{file}.
4958 @item Enabled or Disabled
4959 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4961 For function skips, this column indicates the address in memory of the function
4962 being skipped. If you've set a function skip on a function which has not yet
4963 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4964 which has the function is loaded, @code{info skip} will show the function's
4967 For file skips, this field contains the filename being skipped. For functions
4968 skips, this field contains the function name and its line number in the file
4969 where it is defined.
4973 @item skip delete @r{[}@var{range}@r{]}
4974 Delete the specified skip(s). If @var{range} is not specified, delete all
4978 @item skip enable @r{[}@var{range}@r{]}
4979 Enable the specified skip(s). If @var{range} is not specified, enable all
4982 @kindex skip disable
4983 @item skip disable @r{[}@var{range}@r{]}
4984 Disable the specified skip(s). If @var{range} is not specified, disable all
4993 A signal is an asynchronous event that can happen in a program. The
4994 operating system defines the possible kinds of signals, and gives each
4995 kind a name and a number. For example, in Unix @code{SIGINT} is the
4996 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4997 @code{SIGSEGV} is the signal a program gets from referencing a place in
4998 memory far away from all the areas in use; @code{SIGALRM} occurs when
4999 the alarm clock timer goes off (which happens only if your program has
5000 requested an alarm).
5002 @cindex fatal signals
5003 Some signals, including @code{SIGALRM}, are a normal part of the
5004 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5005 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5006 program has not specified in advance some other way to handle the signal.
5007 @code{SIGINT} does not indicate an error in your program, but it is normally
5008 fatal so it can carry out the purpose of the interrupt: to kill the program.
5010 @value{GDBN} has the ability to detect any occurrence of a signal in your
5011 program. You can tell @value{GDBN} in advance what to do for each kind of
5014 @cindex handling signals
5015 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5016 @code{SIGALRM} be silently passed to your program
5017 (so as not to interfere with their role in the program's functioning)
5018 but to stop your program immediately whenever an error signal happens.
5019 You can change these settings with the @code{handle} command.
5022 @kindex info signals
5026 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5027 handle each one. You can use this to see the signal numbers of all
5028 the defined types of signals.
5030 @item info signals @var{sig}
5031 Similar, but print information only about the specified signal number.
5033 @code{info handle} is an alias for @code{info signals}.
5036 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5037 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5038 can be the number of a signal or its name (with or without the
5039 @samp{SIG} at the beginning); a list of signal numbers of the form
5040 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5041 known signals. Optional arguments @var{keywords}, described below,
5042 say what change to make.
5046 The keywords allowed by the @code{handle} command can be abbreviated.
5047 Their full names are:
5051 @value{GDBN} should not stop your program when this signal happens. It may
5052 still print a message telling you that the signal has come in.
5055 @value{GDBN} should stop your program when this signal happens. This implies
5056 the @code{print} keyword as well.
5059 @value{GDBN} should print a message when this signal happens.
5062 @value{GDBN} should not mention the occurrence of the signal at all. This
5063 implies the @code{nostop} keyword as well.
5067 @value{GDBN} should allow your program to see this signal; your program
5068 can handle the signal, or else it may terminate if the signal is fatal
5069 and not handled. @code{pass} and @code{noignore} are synonyms.
5073 @value{GDBN} should not allow your program to see this signal.
5074 @code{nopass} and @code{ignore} are synonyms.
5078 When a signal stops your program, the signal is not visible to the
5080 continue. Your program sees the signal then, if @code{pass} is in
5081 effect for the signal in question @emph{at that time}. In other words,
5082 after @value{GDBN} reports a signal, you can use the @code{handle}
5083 command with @code{pass} or @code{nopass} to control whether your
5084 program sees that signal when you continue.
5086 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5087 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5088 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5091 You can also use the @code{signal} command to prevent your program from
5092 seeing a signal, or cause it to see a signal it normally would not see,
5093 or to give it any signal at any time. For example, if your program stopped
5094 due to some sort of memory reference error, you might store correct
5095 values into the erroneous variables and continue, hoping to see more
5096 execution; but your program would probably terminate immediately as
5097 a result of the fatal signal once it saw the signal. To prevent this,
5098 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5101 @cindex extra signal information
5102 @anchor{extra signal information}
5104 On some targets, @value{GDBN} can inspect extra signal information
5105 associated with the intercepted signal, before it is actually
5106 delivered to the program being debugged. This information is exported
5107 by the convenience variable @code{$_siginfo}, and consists of data
5108 that is passed by the kernel to the signal handler at the time of the
5109 receipt of a signal. The data type of the information itself is
5110 target dependent. You can see the data type using the @code{ptype
5111 $_siginfo} command. On Unix systems, it typically corresponds to the
5112 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5115 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5116 referenced address that raised a segmentation fault.
5120 (@value{GDBP}) continue
5121 Program received signal SIGSEGV, Segmentation fault.
5122 0x0000000000400766 in main ()
5124 (@value{GDBP}) ptype $_siginfo
5131 struct @{...@} _kill;
5132 struct @{...@} _timer;
5134 struct @{...@} _sigchld;
5135 struct @{...@} _sigfault;
5136 struct @{...@} _sigpoll;
5139 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5143 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5144 $1 = (void *) 0x7ffff7ff7000
5148 Depending on target support, @code{$_siginfo} may also be writable.
5151 @section Stopping and Starting Multi-thread Programs
5153 @cindex stopped threads
5154 @cindex threads, stopped
5156 @cindex continuing threads
5157 @cindex threads, continuing
5159 @value{GDBN} supports debugging programs with multiple threads
5160 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5161 are two modes of controlling execution of your program within the
5162 debugger. In the default mode, referred to as @dfn{all-stop mode},
5163 when any thread in your program stops (for example, at a breakpoint
5164 or while being stepped), all other threads in the program are also stopped by
5165 @value{GDBN}. On some targets, @value{GDBN} also supports
5166 @dfn{non-stop mode}, in which other threads can continue to run freely while
5167 you examine the stopped thread in the debugger.
5170 * All-Stop Mode:: All threads stop when GDB takes control
5171 * Non-Stop Mode:: Other threads continue to execute
5172 * Background Execution:: Running your program asynchronously
5173 * Thread-Specific Breakpoints:: Controlling breakpoints
5174 * Interrupted System Calls:: GDB may interfere with system calls
5175 * Observer Mode:: GDB does not alter program behavior
5179 @subsection All-Stop Mode
5181 @cindex all-stop mode
5183 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5184 @emph{all} threads of execution stop, not just the current thread. This
5185 allows you to examine the overall state of the program, including
5186 switching between threads, without worrying that things may change
5189 Conversely, whenever you restart the program, @emph{all} threads start
5190 executing. @emph{This is true even when single-stepping} with commands
5191 like @code{step} or @code{next}.
5193 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5194 Since thread scheduling is up to your debugging target's operating
5195 system (not controlled by @value{GDBN}), other threads may
5196 execute more than one statement while the current thread completes a
5197 single step. Moreover, in general other threads stop in the middle of a
5198 statement, rather than at a clean statement boundary, when the program
5201 You might even find your program stopped in another thread after
5202 continuing or even single-stepping. This happens whenever some other
5203 thread runs into a breakpoint, a signal, or an exception before the
5204 first thread completes whatever you requested.
5206 @cindex automatic thread selection
5207 @cindex switching threads automatically
5208 @cindex threads, automatic switching
5209 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5210 signal, it automatically selects the thread where that breakpoint or
5211 signal happened. @value{GDBN} alerts you to the context switch with a
5212 message such as @samp{[Switching to Thread @var{n}]} to identify the
5215 On some OSes, you can modify @value{GDBN}'s default behavior by
5216 locking the OS scheduler to allow only a single thread to run.
5219 @item set scheduler-locking @var{mode}
5220 @cindex scheduler locking mode
5221 @cindex lock scheduler
5222 Set the scheduler locking mode. If it is @code{off}, then there is no
5223 locking and any thread may run at any time. If @code{on}, then only the
5224 current thread may run when the inferior is resumed. The @code{step}
5225 mode optimizes for single-stepping; it prevents other threads
5226 from preempting the current thread while you are stepping, so that
5227 the focus of debugging does not change unexpectedly.
5228 Other threads only rarely (or never) get a chance to run
5229 when you step. They are more likely to run when you @samp{next} over a
5230 function call, and they are completely free to run when you use commands
5231 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5232 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5233 the current thread away from the thread that you are debugging.
5235 @item show scheduler-locking
5236 Display the current scheduler locking mode.
5239 @cindex resume threads of multiple processes simultaneously
5240 By default, when you issue one of the execution commands such as
5241 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5242 threads of the current inferior to run. For example, if @value{GDBN}
5243 is attached to two inferiors, each with two threads, the
5244 @code{continue} command resumes only the two threads of the current
5245 inferior. This is useful, for example, when you debug a program that
5246 forks and you want to hold the parent stopped (so that, for instance,
5247 it doesn't run to exit), while you debug the child. In other
5248 situations, you may not be interested in inspecting the current state
5249 of any of the processes @value{GDBN} is attached to, and you may want
5250 to resume them all until some breakpoint is hit. In the latter case,
5251 you can instruct @value{GDBN} to allow all threads of all the
5252 inferiors to run with the @w{@code{set schedule-multiple}} command.
5255 @kindex set schedule-multiple
5256 @item set schedule-multiple
5257 Set the mode for allowing threads of multiple processes to be resumed
5258 when an execution command is issued. When @code{on}, all threads of
5259 all processes are allowed to run. When @code{off}, only the threads
5260 of the current process are resumed. The default is @code{off}. The
5261 @code{scheduler-locking} mode takes precedence when set to @code{on},
5262 or while you are stepping and set to @code{step}.
5264 @item show schedule-multiple
5265 Display the current mode for resuming the execution of threads of
5270 @subsection Non-Stop Mode
5272 @cindex non-stop mode
5274 @c This section is really only a place-holder, and needs to be expanded
5275 @c with more details.
5277 For some multi-threaded targets, @value{GDBN} supports an optional
5278 mode of operation in which you can examine stopped program threads in
5279 the debugger while other threads continue to execute freely. This
5280 minimizes intrusion when debugging live systems, such as programs
5281 where some threads have real-time constraints or must continue to
5282 respond to external events. This is referred to as @dfn{non-stop} mode.
5284 In non-stop mode, when a thread stops to report a debugging event,
5285 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5286 threads as well, in contrast to the all-stop mode behavior. Additionally,
5287 execution commands such as @code{continue} and @code{step} apply by default
5288 only to the current thread in non-stop mode, rather than all threads as
5289 in all-stop mode. This allows you to control threads explicitly in
5290 ways that are not possible in all-stop mode --- for example, stepping
5291 one thread while allowing others to run freely, stepping
5292 one thread while holding all others stopped, or stepping several threads
5293 independently and simultaneously.
5295 To enter non-stop mode, use this sequence of commands before you run
5296 or attach to your program:
5299 # Enable the async interface.
5302 # If using the CLI, pagination breaks non-stop.
5305 # Finally, turn it on!
5309 You can use these commands to manipulate the non-stop mode setting:
5312 @kindex set non-stop
5313 @item set non-stop on
5314 Enable selection of non-stop mode.
5315 @item set non-stop off
5316 Disable selection of non-stop mode.
5317 @kindex show non-stop
5319 Show the current non-stop enablement setting.
5322 Note these commands only reflect whether non-stop mode is enabled,
5323 not whether the currently-executing program is being run in non-stop mode.
5324 In particular, the @code{set non-stop} preference is only consulted when
5325 @value{GDBN} starts or connects to the target program, and it is generally
5326 not possible to switch modes once debugging has started. Furthermore,
5327 since not all targets support non-stop mode, even when you have enabled
5328 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5331 In non-stop mode, all execution commands apply only to the current thread
5332 by default. That is, @code{continue} only continues one thread.
5333 To continue all threads, issue @code{continue -a} or @code{c -a}.
5335 You can use @value{GDBN}'s background execution commands
5336 (@pxref{Background Execution}) to run some threads in the background
5337 while you continue to examine or step others from @value{GDBN}.
5338 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5339 always executed asynchronously in non-stop mode.
5341 Suspending execution is done with the @code{interrupt} command when
5342 running in the background, or @kbd{Ctrl-c} during foreground execution.
5343 In all-stop mode, this stops the whole process;
5344 but in non-stop mode the interrupt applies only to the current thread.
5345 To stop the whole program, use @code{interrupt -a}.
5347 Other execution commands do not currently support the @code{-a} option.
5349 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5350 that thread current, as it does in all-stop mode. This is because the
5351 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5352 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5353 changed to a different thread just as you entered a command to operate on the
5354 previously current thread.
5356 @node Background Execution
5357 @subsection Background Execution
5359 @cindex foreground execution
5360 @cindex background execution
5361 @cindex asynchronous execution
5362 @cindex execution, foreground, background and asynchronous
5364 @value{GDBN}'s execution commands have two variants: the normal
5365 foreground (synchronous) behavior, and a background
5366 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5367 the program to report that some thread has stopped before prompting for
5368 another command. In background execution, @value{GDBN} immediately gives
5369 a command prompt so that you can issue other commands while your program runs.
5371 You need to explicitly enable asynchronous mode before you can use
5372 background execution commands. You can use these commands to
5373 manipulate the asynchronous mode setting:
5376 @kindex set target-async
5377 @item set target-async on
5378 Enable asynchronous mode.
5379 @item set target-async off
5380 Disable asynchronous mode.
5381 @kindex show target-async
5382 @item show target-async
5383 Show the current target-async setting.
5386 If the target doesn't support async mode, @value{GDBN} issues an error
5387 message if you attempt to use the background execution commands.
5389 To specify background execution, add a @code{&} to the command. For example,
5390 the background form of the @code{continue} command is @code{continue&}, or
5391 just @code{c&}. The execution commands that accept background execution
5397 @xref{Starting, , Starting your Program}.
5401 @xref{Attach, , Debugging an Already-running Process}.
5405 @xref{Continuing and Stepping, step}.
5409 @xref{Continuing and Stepping, stepi}.
5413 @xref{Continuing and Stepping, next}.
5417 @xref{Continuing and Stepping, nexti}.
5421 @xref{Continuing and Stepping, continue}.
5425 @xref{Continuing and Stepping, finish}.
5429 @xref{Continuing and Stepping, until}.
5433 Background execution is especially useful in conjunction with non-stop
5434 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5435 However, you can also use these commands in the normal all-stop mode with
5436 the restriction that you cannot issue another execution command until the
5437 previous one finishes. Examples of commands that are valid in all-stop
5438 mode while the program is running include @code{help} and @code{info break}.
5440 You can interrupt your program while it is running in the background by
5441 using the @code{interrupt} command.
5448 Suspend execution of the running program. In all-stop mode,
5449 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5450 only the current thread. To stop the whole program in non-stop mode,
5451 use @code{interrupt -a}.
5454 @node Thread-Specific Breakpoints
5455 @subsection Thread-Specific Breakpoints
5457 When your program has multiple threads (@pxref{Threads,, Debugging
5458 Programs with Multiple Threads}), you can choose whether to set
5459 breakpoints on all threads, or on a particular thread.
5462 @cindex breakpoints and threads
5463 @cindex thread breakpoints
5464 @kindex break @dots{} thread @var{threadno}
5465 @item break @var{linespec} thread @var{threadno}
5466 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5467 @var{linespec} specifies source lines; there are several ways of
5468 writing them (@pxref{Specify Location}), but the effect is always to
5469 specify some source line.
5471 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5472 to specify that you only want @value{GDBN} to stop the program when a
5473 particular thread reaches this breakpoint. @var{threadno} is one of the
5474 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5475 column of the @samp{info threads} display.
5477 If you do not specify @samp{thread @var{threadno}} when you set a
5478 breakpoint, the breakpoint applies to @emph{all} threads of your
5481 You can use the @code{thread} qualifier on conditional breakpoints as
5482 well; in this case, place @samp{thread @var{threadno}} before or
5483 after the breakpoint condition, like this:
5486 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5491 @node Interrupted System Calls
5492 @subsection Interrupted System Calls
5494 @cindex thread breakpoints and system calls
5495 @cindex system calls and thread breakpoints
5496 @cindex premature return from system calls
5497 There is an unfortunate side effect when using @value{GDBN} to debug
5498 multi-threaded programs. If one thread stops for a
5499 breakpoint, or for some other reason, and another thread is blocked in a
5500 system call, then the system call may return prematurely. This is a
5501 consequence of the interaction between multiple threads and the signals
5502 that @value{GDBN} uses to implement breakpoints and other events that
5505 To handle this problem, your program should check the return value of
5506 each system call and react appropriately. This is good programming
5509 For example, do not write code like this:
5515 The call to @code{sleep} will return early if a different thread stops
5516 at a breakpoint or for some other reason.
5518 Instead, write this:
5523 unslept = sleep (unslept);
5526 A system call is allowed to return early, so the system is still
5527 conforming to its specification. But @value{GDBN} does cause your
5528 multi-threaded program to behave differently than it would without
5531 Also, @value{GDBN} uses internal breakpoints in the thread library to
5532 monitor certain events such as thread creation and thread destruction.
5533 When such an event happens, a system call in another thread may return
5534 prematurely, even though your program does not appear to stop.
5537 @subsection Observer Mode
5539 If you want to build on non-stop mode and observe program behavior
5540 without any chance of disruption by @value{GDBN}, you can set
5541 variables to disable all of the debugger's attempts to modify state,
5542 whether by writing memory, inserting breakpoints, etc. These operate
5543 at a low level, intercepting operations from all commands.
5545 When all of these are set to @code{off}, then @value{GDBN} is said to
5546 be @dfn{observer mode}. As a convenience, the variable
5547 @code{observer} can be set to disable these, plus enable non-stop
5550 Note that @value{GDBN} will not prevent you from making nonsensical
5551 combinations of these settings. For instance, if you have enabled
5552 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5553 then breakpoints that work by writing trap instructions into the code
5554 stream will still not be able to be placed.
5559 @item set observer on
5560 @itemx set observer off
5561 When set to @code{on}, this disables all the permission variables
5562 below (except for @code{insert-fast-tracepoints}), plus enables
5563 non-stop debugging. Setting this to @code{off} switches back to
5564 normal debugging, though remaining in non-stop mode.
5567 Show whether observer mode is on or off.
5569 @kindex may-write-registers
5570 @item set may-write-registers on
5571 @itemx set may-write-registers off
5572 This controls whether @value{GDBN} will attempt to alter the values of
5573 registers, such as with assignment expressions in @code{print}, or the
5574 @code{jump} command. It defaults to @code{on}.
5576 @item show may-write-registers
5577 Show the current permission to write registers.
5579 @kindex may-write-memory
5580 @item set may-write-memory on
5581 @itemx set may-write-memory off
5582 This controls whether @value{GDBN} will attempt to alter the contents
5583 of memory, such as with assignment expressions in @code{print}. It
5584 defaults to @code{on}.
5586 @item show may-write-memory
5587 Show the current permission to write memory.
5589 @kindex may-insert-breakpoints
5590 @item set may-insert-breakpoints on
5591 @itemx set may-insert-breakpoints off
5592 This controls whether @value{GDBN} will attempt to insert breakpoints.
5593 This affects all breakpoints, including internal breakpoints defined
5594 by @value{GDBN}. It defaults to @code{on}.
5596 @item show may-insert-breakpoints
5597 Show the current permission to insert breakpoints.
5599 @kindex may-insert-tracepoints
5600 @item set may-insert-tracepoints on
5601 @itemx set may-insert-tracepoints off
5602 This controls whether @value{GDBN} will attempt to insert (regular)
5603 tracepoints at the beginning of a tracing experiment. It affects only
5604 non-fast tracepoints, fast tracepoints being under the control of
5605 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5607 @item show may-insert-tracepoints
5608 Show the current permission to insert tracepoints.
5610 @kindex may-insert-fast-tracepoints
5611 @item set may-insert-fast-tracepoints on
5612 @itemx set may-insert-fast-tracepoints off
5613 This controls whether @value{GDBN} will attempt to insert fast
5614 tracepoints at the beginning of a tracing experiment. It affects only
5615 fast tracepoints, regular (non-fast) tracepoints being under the
5616 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5618 @item show may-insert-fast-tracepoints
5619 Show the current permission to insert fast tracepoints.
5621 @kindex may-interrupt
5622 @item set may-interrupt on
5623 @itemx set may-interrupt off
5624 This controls whether @value{GDBN} will attempt to interrupt or stop
5625 program execution. When this variable is @code{off}, the
5626 @code{interrupt} command will have no effect, nor will
5627 @kbd{Ctrl-c}. It defaults to @code{on}.
5629 @item show may-interrupt
5630 Show the current permission to interrupt or stop the program.
5634 @node Reverse Execution
5635 @chapter Running programs backward
5636 @cindex reverse execution
5637 @cindex running programs backward
5639 When you are debugging a program, it is not unusual to realize that
5640 you have gone too far, and some event of interest has already happened.
5641 If the target environment supports it, @value{GDBN} can allow you to
5642 ``rewind'' the program by running it backward.
5644 A target environment that supports reverse execution should be able
5645 to ``undo'' the changes in machine state that have taken place as the
5646 program was executing normally. Variables, registers etc.@: should
5647 revert to their previous values. Obviously this requires a great
5648 deal of sophistication on the part of the target environment; not
5649 all target environments can support reverse execution.
5651 When a program is executed in reverse, the instructions that
5652 have most recently been executed are ``un-executed'', in reverse
5653 order. The program counter runs backward, following the previous
5654 thread of execution in reverse. As each instruction is ``un-executed'',
5655 the values of memory and/or registers that were changed by that
5656 instruction are reverted to their previous states. After executing
5657 a piece of source code in reverse, all side effects of that code
5658 should be ``undone'', and all variables should be returned to their
5659 prior values@footnote{
5660 Note that some side effects are easier to undo than others. For instance,
5661 memory and registers are relatively easy, but device I/O is hard. Some
5662 targets may be able undo things like device I/O, and some may not.
5664 The contract between @value{GDBN} and the reverse executing target
5665 requires only that the target do something reasonable when
5666 @value{GDBN} tells it to execute backwards, and then report the
5667 results back to @value{GDBN}. Whatever the target reports back to
5668 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5669 assumes that the memory and registers that the target reports are in a
5670 consistant state, but @value{GDBN} accepts whatever it is given.
5673 If you are debugging in a target environment that supports
5674 reverse execution, @value{GDBN} provides the following commands.
5677 @kindex reverse-continue
5678 @kindex rc @r{(@code{reverse-continue})}
5679 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5680 @itemx rc @r{[}@var{ignore-count}@r{]}
5681 Beginning at the point where your program last stopped, start executing
5682 in reverse. Reverse execution will stop for breakpoints and synchronous
5683 exceptions (signals), just like normal execution. Behavior of
5684 asynchronous signals depends on the target environment.
5686 @kindex reverse-step
5687 @kindex rs @r{(@code{step})}
5688 @item reverse-step @r{[}@var{count}@r{]}
5689 Run the program backward until control reaches the start of a
5690 different source line; then stop it, and return control to @value{GDBN}.
5692 Like the @code{step} command, @code{reverse-step} will only stop
5693 at the beginning of a source line. It ``un-executes'' the previously
5694 executed source line. If the previous source line included calls to
5695 debuggable functions, @code{reverse-step} will step (backward) into
5696 the called function, stopping at the beginning of the @emph{last}
5697 statement in the called function (typically a return statement).
5699 Also, as with the @code{step} command, if non-debuggable functions are
5700 called, @code{reverse-step} will run thru them backward without stopping.
5702 @kindex reverse-stepi
5703 @kindex rsi @r{(@code{reverse-stepi})}
5704 @item reverse-stepi @r{[}@var{count}@r{]}
5705 Reverse-execute one machine instruction. Note that the instruction
5706 to be reverse-executed is @emph{not} the one pointed to by the program
5707 counter, but the instruction executed prior to that one. For instance,
5708 if the last instruction was a jump, @code{reverse-stepi} will take you
5709 back from the destination of the jump to the jump instruction itself.
5711 @kindex reverse-next
5712 @kindex rn @r{(@code{reverse-next})}
5713 @item reverse-next @r{[}@var{count}@r{]}
5714 Run backward to the beginning of the previous line executed in
5715 the current (innermost) stack frame. If the line contains function
5716 calls, they will be ``un-executed'' without stopping. Starting from
5717 the first line of a function, @code{reverse-next} will take you back
5718 to the caller of that function, @emph{before} the function was called,
5719 just as the normal @code{next} command would take you from the last
5720 line of a function back to its return to its caller
5721 @footnote{Unless the code is too heavily optimized.}.
5723 @kindex reverse-nexti
5724 @kindex rni @r{(@code{reverse-nexti})}
5725 @item reverse-nexti @r{[}@var{count}@r{]}
5726 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5727 in reverse, except that called functions are ``un-executed'' atomically.
5728 That is, if the previously executed instruction was a return from
5729 another function, @code{reverse-nexti} will continue to execute
5730 in reverse until the call to that function (from the current stack
5733 @kindex reverse-finish
5734 @item reverse-finish
5735 Just as the @code{finish} command takes you to the point where the
5736 current function returns, @code{reverse-finish} takes you to the point
5737 where it was called. Instead of ending up at the end of the current
5738 function invocation, you end up at the beginning.
5740 @kindex set exec-direction
5741 @item set exec-direction
5742 Set the direction of target execution.
5743 @itemx set exec-direction reverse
5744 @cindex execute forward or backward in time
5745 @value{GDBN} will perform all execution commands in reverse, until the
5746 exec-direction mode is changed to ``forward''. Affected commands include
5747 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5748 command cannot be used in reverse mode.
5749 @item set exec-direction forward
5750 @value{GDBN} will perform all execution commands in the normal fashion.
5751 This is the default.
5755 @node Process Record and Replay
5756 @chapter Recording Inferior's Execution and Replaying It
5757 @cindex process record and replay
5758 @cindex recording inferior's execution and replaying it
5760 On some platforms, @value{GDBN} provides a special @dfn{process record
5761 and replay} target that can record a log of the process execution, and
5762 replay it later with both forward and reverse execution commands.
5765 When this target is in use, if the execution log includes the record
5766 for the next instruction, @value{GDBN} will debug in @dfn{replay
5767 mode}. In the replay mode, the inferior does not really execute code
5768 instructions. Instead, all the events that normally happen during
5769 code execution are taken from the execution log. While code is not
5770 really executed in replay mode, the values of registers (including the
5771 program counter register) and the memory of the inferior are still
5772 changed as they normally would. Their contents are taken from the
5776 If the record for the next instruction is not in the execution log,
5777 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5778 inferior executes normally, and @value{GDBN} records the execution log
5781 The process record and replay target supports reverse execution
5782 (@pxref{Reverse Execution}), even if the platform on which the
5783 inferior runs does not. However, the reverse execution is limited in
5784 this case by the range of the instructions recorded in the execution
5785 log. In other words, reverse execution on platforms that don't
5786 support it directly can only be done in the replay mode.
5788 When debugging in the reverse direction, @value{GDBN} will work in
5789 replay mode as long as the execution log includes the record for the
5790 previous instruction; otherwise, it will work in record mode, if the
5791 platform supports reverse execution, or stop if not.
5793 For architecture environments that support process record and replay,
5794 @value{GDBN} provides the following commands:
5797 @kindex target record
5801 This command starts the process record and replay target. The process
5802 record and replay target can only debug a process that is already
5803 running. Therefore, you need first to start the process with the
5804 @kbd{run} or @kbd{start} commands, and then start the recording with
5805 the @kbd{target record} command.
5807 Both @code{record} and @code{rec} are aliases of @code{target record}.
5809 @cindex displaced stepping, and process record and replay
5810 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5811 will be automatically disabled when process record and replay target
5812 is started. That's because the process record and replay target
5813 doesn't support displaced stepping.
5815 @cindex non-stop mode, and process record and replay
5816 @cindex asynchronous execution, and process record and replay
5817 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5818 the asynchronous execution mode (@pxref{Background Execution}), the
5819 process record and replay target cannot be started because it doesn't
5820 support these two modes.
5825 Stop the process record and replay target. When process record and
5826 replay target stops, the entire execution log will be deleted and the
5827 inferior will either be terminated, or will remain in its final state.
5829 When you stop the process record and replay target in record mode (at
5830 the end of the execution log), the inferior will be stopped at the
5831 next instruction that would have been recorded. In other words, if
5832 you record for a while and then stop recording, the inferior process
5833 will be left in the same state as if the recording never happened.
5835 On the other hand, if the process record and replay target is stopped
5836 while in replay mode (that is, not at the end of the execution log,
5837 but at some earlier point), the inferior process will become ``live''
5838 at that earlier state, and it will then be possible to continue the
5839 usual ``live'' debugging of the process from that state.
5841 When the inferior process exits, or @value{GDBN} detaches from it,
5842 process record and replay target will automatically stop itself.
5845 @item record save @var{filename}
5846 Save the execution log to a file @file{@var{filename}}.
5847 Default filename is @file{gdb_record.@var{process_id}}, where
5848 @var{process_id} is the process ID of the inferior.
5850 @kindex record restore
5851 @item record restore @var{filename}
5852 Restore the execution log from a file @file{@var{filename}}.
5853 File must have been created with @code{record save}.
5855 @kindex set record insn-number-max
5856 @item set record insn-number-max @var{limit}
5857 Set the limit of instructions to be recorded. Default value is 200000.
5859 If @var{limit} is a positive number, then @value{GDBN} will start
5860 deleting instructions from the log once the number of the record
5861 instructions becomes greater than @var{limit}. For every new recorded
5862 instruction, @value{GDBN} will delete the earliest recorded
5863 instruction to keep the number of recorded instructions at the limit.
5864 (Since deleting recorded instructions loses information, @value{GDBN}
5865 lets you control what happens when the limit is reached, by means of
5866 the @code{stop-at-limit} option, described below.)
5868 If @var{limit} is zero, @value{GDBN} will never delete recorded
5869 instructions from the execution log. The number of recorded
5870 instructions is unlimited in this case.
5872 @kindex show record insn-number-max
5873 @item show record insn-number-max
5874 Show the limit of instructions to be recorded.
5876 @kindex set record stop-at-limit
5877 @item set record stop-at-limit
5878 Control the behavior when the number of recorded instructions reaches
5879 the limit. If ON (the default), @value{GDBN} will stop when the limit
5880 is reached for the first time and ask you whether you want to stop the
5881 inferior or continue running it and recording the execution log. If
5882 you decide to continue recording, each new recorded instruction will
5883 cause the oldest one to be deleted.
5885 If this option is OFF, @value{GDBN} will automatically delete the
5886 oldest record to make room for each new one, without asking.
5888 @kindex show record stop-at-limit
5889 @item show record stop-at-limit
5890 Show the current setting of @code{stop-at-limit}.
5892 @kindex set record memory-query
5893 @item set record memory-query
5894 Control the behavior when @value{GDBN} is unable to record memory
5895 changes caused by an instruction. If ON, @value{GDBN} will query
5896 whether to stop the inferior in that case.
5898 If this option is OFF (the default), @value{GDBN} will automatically
5899 ignore the effect of such instructions on memory. Later, when
5900 @value{GDBN} replays this execution log, it will mark the log of this
5901 instruction as not accessible, and it will not affect the replay
5904 @kindex show record memory-query
5905 @item show record memory-query
5906 Show the current setting of @code{memory-query}.
5910 Show various statistics about the state of process record and its
5911 in-memory execution log buffer, including:
5915 Whether in record mode or replay mode.
5917 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5919 Highest recorded instruction number.
5921 Current instruction about to be replayed (if in replay mode).
5923 Number of instructions contained in the execution log.
5925 Maximum number of instructions that may be contained in the execution log.
5928 @kindex record delete
5931 When record target runs in replay mode (``in the past''), delete the
5932 subsequent execution log and begin to record a new execution log starting
5933 from the current address. This means you will abandon the previously
5934 recorded ``future'' and begin recording a new ``future''.
5939 @chapter Examining the Stack
5941 When your program has stopped, the first thing you need to know is where it
5942 stopped and how it got there.
5945 Each time your program performs a function call, information about the call
5947 That information includes the location of the call in your program,
5948 the arguments of the call,
5949 and the local variables of the function being called.
5950 The information is saved in a block of data called a @dfn{stack frame}.
5951 The stack frames are allocated in a region of memory called the @dfn{call
5954 When your program stops, the @value{GDBN} commands for examining the
5955 stack allow you to see all of this information.
5957 @cindex selected frame
5958 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5959 @value{GDBN} commands refer implicitly to the selected frame. In
5960 particular, whenever you ask @value{GDBN} for the value of a variable in
5961 your program, the value is found in the selected frame. There are
5962 special @value{GDBN} commands to select whichever frame you are
5963 interested in. @xref{Selection, ,Selecting a Frame}.
5965 When your program stops, @value{GDBN} automatically selects the
5966 currently executing frame and describes it briefly, similar to the
5967 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5970 * Frames:: Stack frames
5971 * Backtrace:: Backtraces
5972 * Selection:: Selecting a frame
5973 * Frame Info:: Information on a frame
5978 @section Stack Frames
5980 @cindex frame, definition
5982 The call stack is divided up into contiguous pieces called @dfn{stack
5983 frames}, or @dfn{frames} for short; each frame is the data associated
5984 with one call to one function. The frame contains the arguments given
5985 to the function, the function's local variables, and the address at
5986 which the function is executing.
5988 @cindex initial frame
5989 @cindex outermost frame
5990 @cindex innermost frame
5991 When your program is started, the stack has only one frame, that of the
5992 function @code{main}. This is called the @dfn{initial} frame or the
5993 @dfn{outermost} frame. Each time a function is called, a new frame is
5994 made. Each time a function returns, the frame for that function invocation
5995 is eliminated. If a function is recursive, there can be many frames for
5996 the same function. The frame for the function in which execution is
5997 actually occurring is called the @dfn{innermost} frame. This is the most
5998 recently created of all the stack frames that still exist.
6000 @cindex frame pointer
6001 Inside your program, stack frames are identified by their addresses. A
6002 stack frame consists of many bytes, each of which has its own address; each
6003 kind of computer has a convention for choosing one byte whose
6004 address serves as the address of the frame. Usually this address is kept
6005 in a register called the @dfn{frame pointer register}
6006 (@pxref{Registers, $fp}) while execution is going on in that frame.
6008 @cindex frame number
6009 @value{GDBN} assigns numbers to all existing stack frames, starting with
6010 zero for the innermost frame, one for the frame that called it,
6011 and so on upward. These numbers do not really exist in your program;
6012 they are assigned by @value{GDBN} to give you a way of designating stack
6013 frames in @value{GDBN} commands.
6015 @c The -fomit-frame-pointer below perennially causes hbox overflow
6016 @c underflow problems.
6017 @cindex frameless execution
6018 Some compilers provide a way to compile functions so that they operate
6019 without stack frames. (For example, the @value{NGCC} option
6021 @samp{-fomit-frame-pointer}
6023 generates functions without a frame.)
6024 This is occasionally done with heavily used library functions to save
6025 the frame setup time. @value{GDBN} has limited facilities for dealing
6026 with these function invocations. If the innermost function invocation
6027 has no stack frame, @value{GDBN} nevertheless regards it as though
6028 it had a separate frame, which is numbered zero as usual, allowing
6029 correct tracing of the function call chain. However, @value{GDBN} has
6030 no provision for frameless functions elsewhere in the stack.
6033 @kindex frame@r{, command}
6034 @cindex current stack frame
6035 @item frame @var{args}
6036 The @code{frame} command allows you to move from one stack frame to another,
6037 and to print the stack frame you select. @var{args} may be either the
6038 address of the frame or the stack frame number. Without an argument,
6039 @code{frame} prints the current stack frame.
6041 @kindex select-frame
6042 @cindex selecting frame silently
6044 The @code{select-frame} command allows you to move from one stack frame
6045 to another without printing the frame. This is the silent version of
6053 @cindex call stack traces
6054 A backtrace is a summary of how your program got where it is. It shows one
6055 line per frame, for many frames, starting with the currently executing
6056 frame (frame zero), followed by its caller (frame one), and on up the
6061 @kindex bt @r{(@code{backtrace})}
6064 Print a backtrace of the entire stack: one line per frame for all
6065 frames in the stack.
6067 You can stop the backtrace at any time by typing the system interrupt
6068 character, normally @kbd{Ctrl-c}.
6070 @item backtrace @var{n}
6072 Similar, but print only the innermost @var{n} frames.
6074 @item backtrace -@var{n}
6076 Similar, but print only the outermost @var{n} frames.
6078 @item backtrace full
6080 @itemx bt full @var{n}
6081 @itemx bt full -@var{n}
6082 Print the values of the local variables also. @var{n} specifies the
6083 number of frames to print, as described above.
6088 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6089 are additional aliases for @code{backtrace}.
6091 @cindex multiple threads, backtrace
6092 In a multi-threaded program, @value{GDBN} by default shows the
6093 backtrace only for the current thread. To display the backtrace for
6094 several or all of the threads, use the command @code{thread apply}
6095 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6096 apply all backtrace}, @value{GDBN} will display the backtrace for all
6097 the threads; this is handy when you debug a core dump of a
6098 multi-threaded program.
6100 Each line in the backtrace shows the frame number and the function name.
6101 The program counter value is also shown---unless you use @code{set
6102 print address off}. The backtrace also shows the source file name and
6103 line number, as well as the arguments to the function. The program
6104 counter value is omitted if it is at the beginning of the code for that
6107 Here is an example of a backtrace. It was made with the command
6108 @samp{bt 3}, so it shows the innermost three frames.
6112 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6114 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6115 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6117 (More stack frames follow...)
6122 The display for frame zero does not begin with a program counter
6123 value, indicating that your program has stopped at the beginning of the
6124 code for line @code{993} of @code{builtin.c}.
6127 The value of parameter @code{data} in frame 1 has been replaced by
6128 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6129 only if it is a scalar (integer, pointer, enumeration, etc). See command
6130 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6131 on how to configure the way function parameter values are printed.
6133 @cindex optimized out, in backtrace
6134 @cindex function call arguments, optimized out
6135 If your program was compiled with optimizations, some compilers will
6136 optimize away arguments passed to functions if those arguments are
6137 never used after the call. Such optimizations generate code that
6138 passes arguments through registers, but doesn't store those arguments
6139 in the stack frame. @value{GDBN} has no way of displaying such
6140 arguments in stack frames other than the innermost one. Here's what
6141 such a backtrace might look like:
6145 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6147 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6148 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6150 (More stack frames follow...)
6155 The values of arguments that were not saved in their stack frames are
6156 shown as @samp{<optimized out>}.
6158 If you need to display the values of such optimized-out arguments,
6159 either deduce that from other variables whose values depend on the one
6160 you are interested in, or recompile without optimizations.
6162 @cindex backtrace beyond @code{main} function
6163 @cindex program entry point
6164 @cindex startup code, and backtrace
6165 Most programs have a standard user entry point---a place where system
6166 libraries and startup code transition into user code. For C this is
6167 @code{main}@footnote{
6168 Note that embedded programs (the so-called ``free-standing''
6169 environment) are not required to have a @code{main} function as the
6170 entry point. They could even have multiple entry points.}.
6171 When @value{GDBN} finds the entry function in a backtrace
6172 it will terminate the backtrace, to avoid tracing into highly
6173 system-specific (and generally uninteresting) code.
6175 If you need to examine the startup code, or limit the number of levels
6176 in a backtrace, you can change this behavior:
6179 @item set backtrace past-main
6180 @itemx set backtrace past-main on
6181 @kindex set backtrace
6182 Backtraces will continue past the user entry point.
6184 @item set backtrace past-main off
6185 Backtraces will stop when they encounter the user entry point. This is the
6188 @item show backtrace past-main
6189 @kindex show backtrace
6190 Display the current user entry point backtrace policy.
6192 @item set backtrace past-entry
6193 @itemx set backtrace past-entry on
6194 Backtraces will continue past the internal entry point of an application.
6195 This entry point is encoded by the linker when the application is built,
6196 and is likely before the user entry point @code{main} (or equivalent) is called.
6198 @item set backtrace past-entry off
6199 Backtraces will stop when they encounter the internal entry point of an
6200 application. This is the default.
6202 @item show backtrace past-entry
6203 Display the current internal entry point backtrace policy.
6205 @item set backtrace limit @var{n}
6206 @itemx set backtrace limit 0
6207 @cindex backtrace limit
6208 Limit the backtrace to @var{n} levels. A value of zero means
6211 @item show backtrace limit
6212 Display the current limit on backtrace levels.
6216 @section Selecting a Frame
6218 Most commands for examining the stack and other data in your program work on
6219 whichever stack frame is selected at the moment. Here are the commands for
6220 selecting a stack frame; all of them finish by printing a brief description
6221 of the stack frame just selected.
6224 @kindex frame@r{, selecting}
6225 @kindex f @r{(@code{frame})}
6228 Select frame number @var{n}. Recall that frame zero is the innermost
6229 (currently executing) frame, frame one is the frame that called the
6230 innermost one, and so on. The highest-numbered frame is the one for
6233 @item frame @var{addr}
6235 Select the frame at address @var{addr}. This is useful mainly if the
6236 chaining of stack frames has been damaged by a bug, making it
6237 impossible for @value{GDBN} to assign numbers properly to all frames. In
6238 addition, this can be useful when your program has multiple stacks and
6239 switches between them.
6241 On the SPARC architecture, @code{frame} needs two addresses to
6242 select an arbitrary frame: a frame pointer and a stack pointer.
6244 On the MIPS and Alpha architecture, it needs two addresses: a stack
6245 pointer and a program counter.
6247 On the 29k architecture, it needs three addresses: a register stack
6248 pointer, a program counter, and a memory stack pointer.
6252 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6253 advances toward the outermost frame, to higher frame numbers, to frames
6254 that have existed longer. @var{n} defaults to one.
6257 @kindex do @r{(@code{down})}
6259 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6260 advances toward the innermost frame, to lower frame numbers, to frames
6261 that were created more recently. @var{n} defaults to one. You may
6262 abbreviate @code{down} as @code{do}.
6265 All of these commands end by printing two lines of output describing the
6266 frame. The first line shows the frame number, the function name, the
6267 arguments, and the source file and line number of execution in that
6268 frame. The second line shows the text of that source line.
6276 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6278 10 read_input_file (argv[i]);
6282 After such a printout, the @code{list} command with no arguments
6283 prints ten lines centered on the point of execution in the frame.
6284 You can also edit the program at the point of execution with your favorite
6285 editing program by typing @code{edit}.
6286 @xref{List, ,Printing Source Lines},
6290 @kindex down-silently
6292 @item up-silently @var{n}
6293 @itemx down-silently @var{n}
6294 These two commands are variants of @code{up} and @code{down},
6295 respectively; they differ in that they do their work silently, without
6296 causing display of the new frame. They are intended primarily for use
6297 in @value{GDBN} command scripts, where the output might be unnecessary and
6302 @section Information About a Frame
6304 There are several other commands to print information about the selected
6310 When used without any argument, this command does not change which
6311 frame is selected, but prints a brief description of the currently
6312 selected stack frame. It can be abbreviated @code{f}. With an
6313 argument, this command is used to select a stack frame.
6314 @xref{Selection, ,Selecting a Frame}.
6317 @kindex info f @r{(@code{info frame})}
6320 This command prints a verbose description of the selected stack frame,
6325 the address of the frame
6327 the address of the next frame down (called by this frame)
6329 the address of the next frame up (caller of this frame)
6331 the language in which the source code corresponding to this frame is written
6333 the address of the frame's arguments
6335 the address of the frame's local variables
6337 the program counter saved in it (the address of execution in the caller frame)
6339 which registers were saved in the frame
6342 @noindent The verbose description is useful when
6343 something has gone wrong that has made the stack format fail to fit
6344 the usual conventions.
6346 @item info frame @var{addr}
6347 @itemx info f @var{addr}
6348 Print a verbose description of the frame at address @var{addr}, without
6349 selecting that frame. The selected frame remains unchanged by this
6350 command. This requires the same kind of address (more than one for some
6351 architectures) that you specify in the @code{frame} command.
6352 @xref{Selection, ,Selecting a Frame}.
6356 Print the arguments of the selected frame, each on a separate line.
6360 Print the local variables of the selected frame, each on a separate
6361 line. These are all variables (declared either static or automatic)
6362 accessible at the point of execution of the selected frame.
6368 @chapter Examining Source Files
6370 @value{GDBN} can print parts of your program's source, since the debugging
6371 information recorded in the program tells @value{GDBN} what source files were
6372 used to build it. When your program stops, @value{GDBN} spontaneously prints
6373 the line where it stopped. Likewise, when you select a stack frame
6374 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6375 execution in that frame has stopped. You can print other portions of
6376 source files by explicit command.
6378 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6379 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6380 @value{GDBN} under @sc{gnu} Emacs}.
6383 * List:: Printing source lines
6384 * Specify Location:: How to specify code locations
6385 * Edit:: Editing source files
6386 * Search:: Searching source files
6387 * Source Path:: Specifying source directories
6388 * Machine Code:: Source and machine code
6392 @section Printing Source Lines
6395 @kindex l @r{(@code{list})}
6396 To print lines from a source file, use the @code{list} command
6397 (abbreviated @code{l}). By default, ten lines are printed.
6398 There are several ways to specify what part of the file you want to
6399 print; see @ref{Specify Location}, for the full list.
6401 Here are the forms of the @code{list} command most commonly used:
6404 @item list @var{linenum}
6405 Print lines centered around line number @var{linenum} in the
6406 current source file.
6408 @item list @var{function}
6409 Print lines centered around the beginning of function
6413 Print more lines. If the last lines printed were printed with a
6414 @code{list} command, this prints lines following the last lines
6415 printed; however, if the last line printed was a solitary line printed
6416 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6417 Stack}), this prints lines centered around that line.
6420 Print lines just before the lines last printed.
6423 @cindex @code{list}, how many lines to display
6424 By default, @value{GDBN} prints ten source lines with any of these forms of
6425 the @code{list} command. You can change this using @code{set listsize}:
6428 @kindex set listsize
6429 @item set listsize @var{count}
6430 Make the @code{list} command display @var{count} source lines (unless
6431 the @code{list} argument explicitly specifies some other number).
6433 @kindex show listsize
6435 Display the number of lines that @code{list} prints.
6438 Repeating a @code{list} command with @key{RET} discards the argument,
6439 so it is equivalent to typing just @code{list}. This is more useful
6440 than listing the same lines again. An exception is made for an
6441 argument of @samp{-}; that argument is preserved in repetition so that
6442 each repetition moves up in the source file.
6444 In general, the @code{list} command expects you to supply zero, one or two
6445 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6446 of writing them (@pxref{Specify Location}), but the effect is always
6447 to specify some source line.
6449 Here is a complete description of the possible arguments for @code{list}:
6452 @item list @var{linespec}
6453 Print lines centered around the line specified by @var{linespec}.
6455 @item list @var{first},@var{last}
6456 Print lines from @var{first} to @var{last}. Both arguments are
6457 linespecs. When a @code{list} command has two linespecs, and the
6458 source file of the second linespec is omitted, this refers to
6459 the same source file as the first linespec.
6461 @item list ,@var{last}
6462 Print lines ending with @var{last}.
6464 @item list @var{first},
6465 Print lines starting with @var{first}.
6468 Print lines just after the lines last printed.
6471 Print lines just before the lines last printed.
6474 As described in the preceding table.
6477 @node Specify Location
6478 @section Specifying a Location
6479 @cindex specifying location
6482 Several @value{GDBN} commands accept arguments that specify a location
6483 of your program's code. Since @value{GDBN} is a source-level
6484 debugger, a location usually specifies some line in the source code;
6485 for that reason, locations are also known as @dfn{linespecs}.
6487 Here are all the different ways of specifying a code location that
6488 @value{GDBN} understands:
6492 Specifies the line number @var{linenum} of the current source file.
6495 @itemx +@var{offset}
6496 Specifies the line @var{offset} lines before or after the @dfn{current
6497 line}. For the @code{list} command, the current line is the last one
6498 printed; for the breakpoint commands, this is the line at which
6499 execution stopped in the currently selected @dfn{stack frame}
6500 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6501 used as the second of the two linespecs in a @code{list} command,
6502 this specifies the line @var{offset} lines up or down from the first
6505 @item @var{filename}:@var{linenum}
6506 Specifies the line @var{linenum} in the source file @var{filename}.
6507 If @var{filename} is a relative file name, then it will match any
6508 source file name with the same trailing components. For example, if
6509 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6510 name of @file{/build/trunk/gcc/expr.c}, but not
6511 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6513 @item @var{function}
6514 Specifies the line that begins the body of the function @var{function}.
6515 For example, in C, this is the line with the open brace.
6517 @item @var{function}:@var{label}
6518 Specifies the line where @var{label} appears in @var{function}.
6520 @item @var{filename}:@var{function}
6521 Specifies the line that begins the body of the function @var{function}
6522 in the file @var{filename}. You only need the file name with a
6523 function name to avoid ambiguity when there are identically named
6524 functions in different source files.
6527 Specifies the line at which the label named @var{label} appears.
6528 @value{GDBN} searches for the label in the function corresponding to
6529 the currently selected stack frame. If there is no current selected
6530 stack frame (for instance, if the inferior is not running), then
6531 @value{GDBN} will not search for a label.
6533 @item *@var{address}
6534 Specifies the program address @var{address}. For line-oriented
6535 commands, such as @code{list} and @code{edit}, this specifies a source
6536 line that contains @var{address}. For @code{break} and other
6537 breakpoint oriented commands, this can be used to set breakpoints in
6538 parts of your program which do not have debugging information or
6541 Here @var{address} may be any expression valid in the current working
6542 language (@pxref{Languages, working language}) that specifies a code
6543 address. In addition, as a convenience, @value{GDBN} extends the
6544 semantics of expressions used in locations to cover the situations
6545 that frequently happen during debugging. Here are the various forms
6549 @item @var{expression}
6550 Any expression valid in the current working language.
6552 @item @var{funcaddr}
6553 An address of a function or procedure derived from its name. In C,
6554 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6555 simply the function's name @var{function} (and actually a special case
6556 of a valid expression). In Pascal and Modula-2, this is
6557 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6558 (although the Pascal form also works).
6560 This form specifies the address of the function's first instruction,
6561 before the stack frame and arguments have been set up.
6563 @item '@var{filename}'::@var{funcaddr}
6564 Like @var{funcaddr} above, but also specifies the name of the source
6565 file explicitly. This is useful if the name of the function does not
6566 specify the function unambiguously, e.g., if there are several
6567 functions with identical names in different source files.
6574 @section Editing Source Files
6575 @cindex editing source files
6578 @kindex e @r{(@code{edit})}
6579 To edit the lines in a source file, use the @code{edit} command.
6580 The editing program of your choice
6581 is invoked with the current line set to
6582 the active line in the program.
6583 Alternatively, there are several ways to specify what part of the file you
6584 want to print if you want to see other parts of the program:
6587 @item edit @var{location}
6588 Edit the source file specified by @code{location}. Editing starts at
6589 that @var{location}, e.g., at the specified source line of the
6590 specified file. @xref{Specify Location}, for all the possible forms
6591 of the @var{location} argument; here are the forms of the @code{edit}
6592 command most commonly used:
6595 @item edit @var{number}
6596 Edit the current source file with @var{number} as the active line number.
6598 @item edit @var{function}
6599 Edit the file containing @var{function} at the beginning of its definition.
6604 @subsection Choosing your Editor
6605 You can customize @value{GDBN} to use any editor you want
6607 The only restriction is that your editor (say @code{ex}), recognizes the
6608 following command-line syntax:
6610 ex +@var{number} file
6612 The optional numeric value +@var{number} specifies the number of the line in
6613 the file where to start editing.}.
6614 By default, it is @file{@value{EDITOR}}, but you can change this
6615 by setting the environment variable @code{EDITOR} before using
6616 @value{GDBN}. For example, to configure @value{GDBN} to use the
6617 @code{vi} editor, you could use these commands with the @code{sh} shell:
6623 or in the @code{csh} shell,
6625 setenv EDITOR /usr/bin/vi
6630 @section Searching Source Files
6631 @cindex searching source files
6633 There are two commands for searching through the current source file for a
6638 @kindex forward-search
6639 @item forward-search @var{regexp}
6640 @itemx search @var{regexp}
6641 The command @samp{forward-search @var{regexp}} checks each line,
6642 starting with the one following the last line listed, for a match for
6643 @var{regexp}. It lists the line that is found. You can use the
6644 synonym @samp{search @var{regexp}} or abbreviate the command name as
6647 @kindex reverse-search
6648 @item reverse-search @var{regexp}
6649 The command @samp{reverse-search @var{regexp}} checks each line, starting
6650 with the one before the last line listed and going backward, for a match
6651 for @var{regexp}. It lists the line that is found. You can abbreviate
6652 this command as @code{rev}.
6656 @section Specifying Source Directories
6659 @cindex directories for source files
6660 Executable programs sometimes do not record the directories of the source
6661 files from which they were compiled, just the names. Even when they do,
6662 the directories could be moved between the compilation and your debugging
6663 session. @value{GDBN} has a list of directories to search for source files;
6664 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6665 it tries all the directories in the list, in the order they are present
6666 in the list, until it finds a file with the desired name.
6668 For example, suppose an executable references the file
6669 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6670 @file{/mnt/cross}. The file is first looked up literally; if this
6671 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6672 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6673 message is printed. @value{GDBN} does not look up the parts of the
6674 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6675 Likewise, the subdirectories of the source path are not searched: if
6676 the source path is @file{/mnt/cross}, and the binary refers to
6677 @file{foo.c}, @value{GDBN} would not find it under
6678 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6680 Plain file names, relative file names with leading directories, file
6681 names containing dots, etc.@: are all treated as described above; for
6682 instance, if the source path is @file{/mnt/cross}, and the source file
6683 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6684 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6685 that---@file{/mnt/cross/foo.c}.
6687 Note that the executable search path is @emph{not} used to locate the
6690 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6691 any information it has cached about where source files are found and where
6692 each line is in the file.
6696 When you start @value{GDBN}, its source path includes only @samp{cdir}
6697 and @samp{cwd}, in that order.
6698 To add other directories, use the @code{directory} command.
6700 The search path is used to find both program source files and @value{GDBN}
6701 script files (read using the @samp{-command} option and @samp{source} command).
6703 In addition to the source path, @value{GDBN} provides a set of commands
6704 that manage a list of source path substitution rules. A @dfn{substitution
6705 rule} specifies how to rewrite source directories stored in the program's
6706 debug information in case the sources were moved to a different
6707 directory between compilation and debugging. A rule is made of
6708 two strings, the first specifying what needs to be rewritten in
6709 the path, and the second specifying how it should be rewritten.
6710 In @ref{set substitute-path}, we name these two parts @var{from} and
6711 @var{to} respectively. @value{GDBN} does a simple string replacement
6712 of @var{from} with @var{to} at the start of the directory part of the
6713 source file name, and uses that result instead of the original file
6714 name to look up the sources.
6716 Using the previous example, suppose the @file{foo-1.0} tree has been
6717 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6718 @value{GDBN} to replace @file{/usr/src} in all source path names with
6719 @file{/mnt/cross}. The first lookup will then be
6720 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6721 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6722 substitution rule, use the @code{set substitute-path} command
6723 (@pxref{set substitute-path}).
6725 To avoid unexpected substitution results, a rule is applied only if the
6726 @var{from} part of the directory name ends at a directory separator.
6727 For instance, a rule substituting @file{/usr/source} into
6728 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6729 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6730 is applied only at the beginning of the directory name, this rule will
6731 not be applied to @file{/root/usr/source/baz.c} either.
6733 In many cases, you can achieve the same result using the @code{directory}
6734 command. However, @code{set substitute-path} can be more efficient in
6735 the case where the sources are organized in a complex tree with multiple
6736 subdirectories. With the @code{directory} command, you need to add each
6737 subdirectory of your project. If you moved the entire tree while
6738 preserving its internal organization, then @code{set substitute-path}
6739 allows you to direct the debugger to all the sources with one single
6742 @code{set substitute-path} is also more than just a shortcut command.
6743 The source path is only used if the file at the original location no
6744 longer exists. On the other hand, @code{set substitute-path} modifies
6745 the debugger behavior to look at the rewritten location instead. So, if
6746 for any reason a source file that is not relevant to your executable is
6747 located at the original location, a substitution rule is the only
6748 method available to point @value{GDBN} at the new location.
6750 @cindex @samp{--with-relocated-sources}
6751 @cindex default source path substitution
6752 You can configure a default source path substitution rule by
6753 configuring @value{GDBN} with the
6754 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6755 should be the name of a directory under @value{GDBN}'s configured
6756 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6757 directory names in debug information under @var{dir} will be adjusted
6758 automatically if the installed @value{GDBN} is moved to a new
6759 location. This is useful if @value{GDBN}, libraries or executables
6760 with debug information and corresponding source code are being moved
6764 @item directory @var{dirname} @dots{}
6765 @item dir @var{dirname} @dots{}
6766 Add directory @var{dirname} to the front of the source path. Several
6767 directory names may be given to this command, separated by @samp{:}
6768 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6769 part of absolute file names) or
6770 whitespace. You may specify a directory that is already in the source
6771 path; this moves it forward, so @value{GDBN} searches it sooner.
6775 @vindex $cdir@r{, convenience variable}
6776 @vindex $cwd@r{, convenience variable}
6777 @cindex compilation directory
6778 @cindex current directory
6779 @cindex working directory
6780 @cindex directory, current
6781 @cindex directory, compilation
6782 You can use the string @samp{$cdir} to refer to the compilation
6783 directory (if one is recorded), and @samp{$cwd} to refer to the current
6784 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6785 tracks the current working directory as it changes during your @value{GDBN}
6786 session, while the latter is immediately expanded to the current
6787 directory at the time you add an entry to the source path.
6790 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6792 @c RET-repeat for @code{directory} is explicitly disabled, but since
6793 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6795 @item set directories @var{path-list}
6796 @kindex set directories
6797 Set the source path to @var{path-list}.
6798 @samp{$cdir:$cwd} are added if missing.
6800 @item show directories
6801 @kindex show directories
6802 Print the source path: show which directories it contains.
6804 @anchor{set substitute-path}
6805 @item set substitute-path @var{from} @var{to}
6806 @kindex set substitute-path
6807 Define a source path substitution rule, and add it at the end of the
6808 current list of existing substitution rules. If a rule with the same
6809 @var{from} was already defined, then the old rule is also deleted.
6811 For example, if the file @file{/foo/bar/baz.c} was moved to
6812 @file{/mnt/cross/baz.c}, then the command
6815 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6819 will tell @value{GDBN} to replace @samp{/usr/src} with
6820 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6821 @file{baz.c} even though it was moved.
6823 In the case when more than one substitution rule have been defined,
6824 the rules are evaluated one by one in the order where they have been
6825 defined. The first one matching, if any, is selected to perform
6828 For instance, if we had entered the following commands:
6831 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6832 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6836 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6837 @file{/mnt/include/defs.h} by using the first rule. However, it would
6838 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6839 @file{/mnt/src/lib/foo.c}.
6842 @item unset substitute-path [path]
6843 @kindex unset substitute-path
6844 If a path is specified, search the current list of substitution rules
6845 for a rule that would rewrite that path. Delete that rule if found.
6846 A warning is emitted by the debugger if no rule could be found.
6848 If no path is specified, then all substitution rules are deleted.
6850 @item show substitute-path [path]
6851 @kindex show substitute-path
6852 If a path is specified, then print the source path substitution rule
6853 which would rewrite that path, if any.
6855 If no path is specified, then print all existing source path substitution
6860 If your source path is cluttered with directories that are no longer of
6861 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6862 versions of source. You can correct the situation as follows:
6866 Use @code{directory} with no argument to reset the source path to its default value.
6869 Use @code{directory} with suitable arguments to reinstall the
6870 directories you want in the source path. You can add all the
6871 directories in one command.
6875 @section Source and Machine Code
6876 @cindex source line and its code address
6878 You can use the command @code{info line} to map source lines to program
6879 addresses (and vice versa), and the command @code{disassemble} to display
6880 a range of addresses as machine instructions. You can use the command
6881 @code{set disassemble-next-line} to set whether to disassemble next
6882 source line when execution stops. When run under @sc{gnu} Emacs
6883 mode, the @code{info line} command causes the arrow to point to the
6884 line specified. Also, @code{info line} prints addresses in symbolic form as
6889 @item info line @var{linespec}
6890 Print the starting and ending addresses of the compiled code for
6891 source line @var{linespec}. You can specify source lines in any of
6892 the ways documented in @ref{Specify Location}.
6895 For example, we can use @code{info line} to discover the location of
6896 the object code for the first line of function
6897 @code{m4_changequote}:
6899 @c FIXME: I think this example should also show the addresses in
6900 @c symbolic form, as they usually would be displayed.
6902 (@value{GDBP}) info line m4_changequote
6903 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6907 @cindex code address and its source line
6908 We can also inquire (using @code{*@var{addr}} as the form for
6909 @var{linespec}) what source line covers a particular address:
6911 (@value{GDBP}) info line *0x63ff
6912 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6915 @cindex @code{$_} and @code{info line}
6916 @cindex @code{x} command, default address
6917 @kindex x@r{(examine), and} info line
6918 After @code{info line}, the default address for the @code{x} command
6919 is changed to the starting address of the line, so that @samp{x/i} is
6920 sufficient to begin examining the machine code (@pxref{Memory,
6921 ,Examining Memory}). Also, this address is saved as the value of the
6922 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6927 @cindex assembly instructions
6928 @cindex instructions, assembly
6929 @cindex machine instructions
6930 @cindex listing machine instructions
6932 @itemx disassemble /m
6933 @itemx disassemble /r
6934 This specialized command dumps a range of memory as machine
6935 instructions. It can also print mixed source+disassembly by specifying
6936 the @code{/m} modifier and print the raw instructions in hex as well as
6937 in symbolic form by specifying the @code{/r}.
6938 The default memory range is the function surrounding the
6939 program counter of the selected frame. A single argument to this
6940 command is a program counter value; @value{GDBN} dumps the function
6941 surrounding this value. When two arguments are given, they should
6942 be separated by a comma, possibly surrounded by whitespace. The
6943 arguments specify a range of addresses to dump, in one of two forms:
6946 @item @var{start},@var{end}
6947 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6948 @item @var{start},+@var{length}
6949 the addresses from @var{start} (inclusive) to
6950 @code{@var{start}+@var{length}} (exclusive).
6954 When 2 arguments are specified, the name of the function is also
6955 printed (since there could be several functions in the given range).
6957 The argument(s) can be any expression yielding a numeric value, such as
6958 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6960 If the range of memory being disassembled contains current program counter,
6961 the instruction at that location is shown with a @code{=>} marker.
6964 The following example shows the disassembly of a range of addresses of
6965 HP PA-RISC 2.0 code:
6968 (@value{GDBP}) disas 0x32c4, 0x32e4
6969 Dump of assembler code from 0x32c4 to 0x32e4:
6970 0x32c4 <main+204>: addil 0,dp
6971 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6972 0x32cc <main+212>: ldil 0x3000,r31
6973 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6974 0x32d4 <main+220>: ldo 0(r31),rp
6975 0x32d8 <main+224>: addil -0x800,dp
6976 0x32dc <main+228>: ldo 0x588(r1),r26
6977 0x32e0 <main+232>: ldil 0x3000,r31
6978 End of assembler dump.
6981 Here is an example showing mixed source+assembly for Intel x86, when the
6982 program is stopped just after function prologue:
6985 (@value{GDBP}) disas /m main
6986 Dump of assembler code for function main:
6988 0x08048330 <+0>: push %ebp
6989 0x08048331 <+1>: mov %esp,%ebp
6990 0x08048333 <+3>: sub $0x8,%esp
6991 0x08048336 <+6>: and $0xfffffff0,%esp
6992 0x08048339 <+9>: sub $0x10,%esp
6994 6 printf ("Hello.\n");
6995 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6996 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7000 0x08048348 <+24>: mov $0x0,%eax
7001 0x0804834d <+29>: leave
7002 0x0804834e <+30>: ret
7004 End of assembler dump.
7007 Here is another example showing raw instructions in hex for AMD x86-64,
7010 (gdb) disas /r 0x400281,+10
7011 Dump of assembler code from 0x400281 to 0x40028b:
7012 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7013 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7014 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7015 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7016 End of assembler dump.
7019 Some architectures have more than one commonly-used set of instruction
7020 mnemonics or other syntax.
7022 For programs that were dynamically linked and use shared libraries,
7023 instructions that call functions or branch to locations in the shared
7024 libraries might show a seemingly bogus location---it's actually a
7025 location of the relocation table. On some architectures, @value{GDBN}
7026 might be able to resolve these to actual function names.
7029 @kindex set disassembly-flavor
7030 @cindex Intel disassembly flavor
7031 @cindex AT&T disassembly flavor
7032 @item set disassembly-flavor @var{instruction-set}
7033 Select the instruction set to use when disassembling the
7034 program via the @code{disassemble} or @code{x/i} commands.
7036 Currently this command is only defined for the Intel x86 family. You
7037 can set @var{instruction-set} to either @code{intel} or @code{att}.
7038 The default is @code{att}, the AT&T flavor used by default by Unix
7039 assemblers for x86-based targets.
7041 @kindex show disassembly-flavor
7042 @item show disassembly-flavor
7043 Show the current setting of the disassembly flavor.
7047 @kindex set disassemble-next-line
7048 @kindex show disassemble-next-line
7049 @item set disassemble-next-line
7050 @itemx show disassemble-next-line
7051 Control whether or not @value{GDBN} will disassemble the next source
7052 line or instruction when execution stops. If ON, @value{GDBN} will
7053 display disassembly of the next source line when execution of the
7054 program being debugged stops. This is @emph{in addition} to
7055 displaying the source line itself, which @value{GDBN} always does if
7056 possible. If the next source line cannot be displayed for some reason
7057 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7058 info in the debug info), @value{GDBN} will display disassembly of the
7059 next @emph{instruction} instead of showing the next source line. If
7060 AUTO, @value{GDBN} will display disassembly of next instruction only
7061 if the source line cannot be displayed. This setting causes
7062 @value{GDBN} to display some feedback when you step through a function
7063 with no line info or whose source file is unavailable. The default is
7064 OFF, which means never display the disassembly of the next line or
7070 @chapter Examining Data
7072 @cindex printing data
7073 @cindex examining data
7076 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7077 @c document because it is nonstandard... Under Epoch it displays in a
7078 @c different window or something like that.
7079 The usual way to examine data in your program is with the @code{print}
7080 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7081 evaluates and prints the value of an expression of the language your
7082 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7083 Different Languages}). It may also print the expression using a
7084 Python-based pretty-printer (@pxref{Pretty Printing}).
7087 @item print @var{expr}
7088 @itemx print /@var{f} @var{expr}
7089 @var{expr} is an expression (in the source language). By default the
7090 value of @var{expr} is printed in a format appropriate to its data type;
7091 you can choose a different format by specifying @samp{/@var{f}}, where
7092 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7096 @itemx print /@var{f}
7097 @cindex reprint the last value
7098 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7099 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7100 conveniently inspect the same value in an alternative format.
7103 A more low-level way of examining data is with the @code{x} command.
7104 It examines data in memory at a specified address and prints it in a
7105 specified format. @xref{Memory, ,Examining Memory}.
7107 If you are interested in information about types, or about how the
7108 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7109 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7113 * Expressions:: Expressions
7114 * Ambiguous Expressions:: Ambiguous Expressions
7115 * Variables:: Program variables
7116 * Arrays:: Artificial arrays
7117 * Output Formats:: Output formats
7118 * Memory:: Examining memory
7119 * Auto Display:: Automatic display
7120 * Print Settings:: Print settings
7121 * Pretty Printing:: Python pretty printing
7122 * Value History:: Value history
7123 * Convenience Vars:: Convenience variables
7124 * Registers:: Registers
7125 * Floating Point Hardware:: Floating point hardware
7126 * Vector Unit:: Vector Unit
7127 * OS Information:: Auxiliary data provided by operating system
7128 * Memory Region Attributes:: Memory region attributes
7129 * Dump/Restore Files:: Copy between memory and a file
7130 * Core File Generation:: Cause a program dump its core
7131 * Character Sets:: Debugging programs that use a different
7132 character set than GDB does
7133 * Caching Remote Data:: Data caching for remote targets
7134 * Searching Memory:: Searching memory for a sequence of bytes
7138 @section Expressions
7141 @code{print} and many other @value{GDBN} commands accept an expression and
7142 compute its value. Any kind of constant, variable or operator defined
7143 by the programming language you are using is valid in an expression in
7144 @value{GDBN}. This includes conditional expressions, function calls,
7145 casts, and string constants. It also includes preprocessor macros, if
7146 you compiled your program to include this information; see
7149 @cindex arrays in expressions
7150 @value{GDBN} supports array constants in expressions input by
7151 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7152 you can use the command @code{print @{1, 2, 3@}} to create an array
7153 of three integers. If you pass an array to a function or assign it
7154 to a program variable, @value{GDBN} copies the array to memory that
7155 is @code{malloc}ed in the target program.
7157 Because C is so widespread, most of the expressions shown in examples in
7158 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7159 Languages}, for information on how to use expressions in other
7162 In this section, we discuss operators that you can use in @value{GDBN}
7163 expressions regardless of your programming language.
7165 @cindex casts, in expressions
7166 Casts are supported in all languages, not just in C, because it is so
7167 useful to cast a number into a pointer in order to examine a structure
7168 at that address in memory.
7169 @c FIXME: casts supported---Mod2 true?
7171 @value{GDBN} supports these operators, in addition to those common
7172 to programming languages:
7176 @samp{@@} is a binary operator for treating parts of memory as arrays.
7177 @xref{Arrays, ,Artificial Arrays}, for more information.
7180 @samp{::} allows you to specify a variable in terms of the file or
7181 function where it is defined. @xref{Variables, ,Program Variables}.
7183 @cindex @{@var{type}@}
7184 @cindex type casting memory
7185 @cindex memory, viewing as typed object
7186 @cindex casts, to view memory
7187 @item @{@var{type}@} @var{addr}
7188 Refers to an object of type @var{type} stored at address @var{addr} in
7189 memory. @var{addr} may be any expression whose value is an integer or
7190 pointer (but parentheses are required around binary operators, just as in
7191 a cast). This construct is allowed regardless of what kind of data is
7192 normally supposed to reside at @var{addr}.
7195 @node Ambiguous Expressions
7196 @section Ambiguous Expressions
7197 @cindex ambiguous expressions
7199 Expressions can sometimes contain some ambiguous elements. For instance,
7200 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7201 a single function name to be defined several times, for application in
7202 different contexts. This is called @dfn{overloading}. Another example
7203 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7204 templates and is typically instantiated several times, resulting in
7205 the same function name being defined in different contexts.
7207 In some cases and depending on the language, it is possible to adjust
7208 the expression to remove the ambiguity. For instance in C@t{++}, you
7209 can specify the signature of the function you want to break on, as in
7210 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7211 qualified name of your function often makes the expression unambiguous
7214 When an ambiguity that needs to be resolved is detected, the debugger
7215 has the capability to display a menu of numbered choices for each
7216 possibility, and then waits for the selection with the prompt @samp{>}.
7217 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7218 aborts the current command. If the command in which the expression was
7219 used allows more than one choice to be selected, the next option in the
7220 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7223 For example, the following session excerpt shows an attempt to set a
7224 breakpoint at the overloaded symbol @code{String::after}.
7225 We choose three particular definitions of that function name:
7227 @c FIXME! This is likely to change to show arg type lists, at least
7230 (@value{GDBP}) b String::after
7233 [2] file:String.cc; line number:867
7234 [3] file:String.cc; line number:860
7235 [4] file:String.cc; line number:875
7236 [5] file:String.cc; line number:853
7237 [6] file:String.cc; line number:846
7238 [7] file:String.cc; line number:735
7240 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7241 Breakpoint 2 at 0xb344: file String.cc, line 875.
7242 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7243 Multiple breakpoints were set.
7244 Use the "delete" command to delete unwanted
7251 @kindex set multiple-symbols
7252 @item set multiple-symbols @var{mode}
7253 @cindex multiple-symbols menu
7255 This option allows you to adjust the debugger behavior when an expression
7258 By default, @var{mode} is set to @code{all}. If the command with which
7259 the expression is used allows more than one choice, then @value{GDBN}
7260 automatically selects all possible choices. For instance, inserting
7261 a breakpoint on a function using an ambiguous name results in a breakpoint
7262 inserted on each possible match. However, if a unique choice must be made,
7263 then @value{GDBN} uses the menu to help you disambiguate the expression.
7264 For instance, printing the address of an overloaded function will result
7265 in the use of the menu.
7267 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7268 when an ambiguity is detected.
7270 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7271 an error due to the ambiguity and the command is aborted.
7273 @kindex show multiple-symbols
7274 @item show multiple-symbols
7275 Show the current value of the @code{multiple-symbols} setting.
7279 @section Program Variables
7281 The most common kind of expression to use is the name of a variable
7284 Variables in expressions are understood in the selected stack frame
7285 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7289 global (or file-static)
7296 visible according to the scope rules of the
7297 programming language from the point of execution in that frame
7300 @noindent This means that in the function
7315 you can examine and use the variable @code{a} whenever your program is
7316 executing within the function @code{foo}, but you can only use or
7317 examine the variable @code{b} while your program is executing inside
7318 the block where @code{b} is declared.
7320 @cindex variable name conflict
7321 There is an exception: you can refer to a variable or function whose
7322 scope is a single source file even if the current execution point is not
7323 in this file. But it is possible to have more than one such variable or
7324 function with the same name (in different source files). If that
7325 happens, referring to that name has unpredictable effects. If you wish,
7326 you can specify a static variable in a particular function or file by
7327 using the colon-colon (@code{::}) notation:
7329 @cindex colon-colon, context for variables/functions
7331 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7332 @cindex @code{::}, context for variables/functions
7335 @var{file}::@var{variable}
7336 @var{function}::@var{variable}
7340 Here @var{file} or @var{function} is the name of the context for the
7341 static @var{variable}. In the case of file names, you can use quotes to
7342 make sure @value{GDBN} parses the file name as a single word---for example,
7343 to print a global value of @code{x} defined in @file{f2.c}:
7346 (@value{GDBP}) p 'f2.c'::x
7349 The @code{::} notation is normally used for referring to
7350 static variables, since you typically disambiguate uses of local variables
7351 in functions by selecting the appropriate frame and using the
7352 simple name of the variable. However, you may also use this notation
7353 to refer to local variables in frames enclosing the selected frame:
7362 process (a); /* Stop here */
7373 For example, if there is a breakpoint at the commented line,
7374 here is what you might see
7375 when the program stops after executing the call @code{bar(0)}:
7380 (@value{GDBP}) p bar::a
7383 #2 0x080483d0 in foo (a=5) at foobar.c:12
7386 (@value{GDBP}) p bar::a
7390 @cindex C@t{++} scope resolution
7391 These uses of @samp{::} are very rarely in conflict with the very similar
7392 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7393 scope resolution operator in @value{GDBN} expressions.
7394 @c FIXME: Um, so what happens in one of those rare cases where it's in
7397 @cindex wrong values
7398 @cindex variable values, wrong
7399 @cindex function entry/exit, wrong values of variables
7400 @cindex optimized code, wrong values of variables
7402 @emph{Warning:} Occasionally, a local variable may appear to have the
7403 wrong value at certain points in a function---just after entry to a new
7404 scope, and just before exit.
7406 You may see this problem when you are stepping by machine instructions.
7407 This is because, on most machines, it takes more than one instruction to
7408 set up a stack frame (including local variable definitions); if you are
7409 stepping by machine instructions, variables may appear to have the wrong
7410 values until the stack frame is completely built. On exit, it usually
7411 also takes more than one machine instruction to destroy a stack frame;
7412 after you begin stepping through that group of instructions, local
7413 variable definitions may be gone.
7415 This may also happen when the compiler does significant optimizations.
7416 To be sure of always seeing accurate values, turn off all optimization
7419 @cindex ``No symbol "foo" in current context''
7420 Another possible effect of compiler optimizations is to optimize
7421 unused variables out of existence, or assign variables to registers (as
7422 opposed to memory addresses). Depending on the support for such cases
7423 offered by the debug info format used by the compiler, @value{GDBN}
7424 might not be able to display values for such local variables. If that
7425 happens, @value{GDBN} will print a message like this:
7428 No symbol "foo" in current context.
7431 To solve such problems, either recompile without optimizations, or use a
7432 different debug info format, if the compiler supports several such
7433 formats. @xref{Compilation}, for more information on choosing compiler
7434 options. @xref{C, ,C and C@t{++}}, for more information about debug
7435 info formats that are best suited to C@t{++} programs.
7437 If you ask to print an object whose contents are unknown to
7438 @value{GDBN}, e.g., because its data type is not completely specified
7439 by the debug information, @value{GDBN} will say @samp{<incomplete
7440 type>}. @xref{Symbols, incomplete type}, for more about this.
7442 If you append @kbd{@@entry} string to a function parameter name you get its
7443 value at the time the function got called. If the value is not available an
7444 error message is printed. Entry values are available only with some compilers.
7445 Entry values are normally also printed at the function parameter list according
7446 to @ref{set print entry-values}.
7449 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7455 (gdb) print i@@entry
7459 Strings are identified as arrays of @code{char} values without specified
7460 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7461 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7462 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7463 defines literal string type @code{"char"} as @code{char} without a sign.
7468 signed char var1[] = "A";
7471 You get during debugging
7476 $2 = @{65 'A', 0 '\0'@}
7480 @section Artificial Arrays
7482 @cindex artificial array
7484 @kindex @@@r{, referencing memory as an array}
7485 It is often useful to print out several successive objects of the
7486 same type in memory; a section of an array, or an array of
7487 dynamically determined size for which only a pointer exists in the
7490 You can do this by referring to a contiguous span of memory as an
7491 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7492 operand of @samp{@@} should be the first element of the desired array
7493 and be an individual object. The right operand should be the desired length
7494 of the array. The result is an array value whose elements are all of
7495 the type of the left argument. The first element is actually the left
7496 argument; the second element comes from bytes of memory immediately
7497 following those that hold the first element, and so on. Here is an
7498 example. If a program says
7501 int *array = (int *) malloc (len * sizeof (int));
7505 you can print the contents of @code{array} with
7511 The left operand of @samp{@@} must reside in memory. Array values made
7512 with @samp{@@} in this way behave just like other arrays in terms of
7513 subscripting, and are coerced to pointers when used in expressions.
7514 Artificial arrays most often appear in expressions via the value history
7515 (@pxref{Value History, ,Value History}), after printing one out.
7517 Another way to create an artificial array is to use a cast.
7518 This re-interprets a value as if it were an array.
7519 The value need not be in memory:
7521 (@value{GDBP}) p/x (short[2])0x12345678
7522 $1 = @{0x1234, 0x5678@}
7525 As a convenience, if you leave the array length out (as in
7526 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7527 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7529 (@value{GDBP}) p/x (short[])0x12345678
7530 $2 = @{0x1234, 0x5678@}
7533 Sometimes the artificial array mechanism is not quite enough; in
7534 moderately complex data structures, the elements of interest may not
7535 actually be adjacent---for example, if you are interested in the values
7536 of pointers in an array. One useful work-around in this situation is
7537 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7538 Variables}) as a counter in an expression that prints the first
7539 interesting value, and then repeat that expression via @key{RET}. For
7540 instance, suppose you have an array @code{dtab} of pointers to
7541 structures, and you are interested in the values of a field @code{fv}
7542 in each structure. Here is an example of what you might type:
7552 @node Output Formats
7553 @section Output Formats
7555 @cindex formatted output
7556 @cindex output formats
7557 By default, @value{GDBN} prints a value according to its data type. Sometimes
7558 this is not what you want. For example, you might want to print a number
7559 in hex, or a pointer in decimal. Or you might want to view data in memory
7560 at a certain address as a character string or as an instruction. To do
7561 these things, specify an @dfn{output format} when you print a value.
7563 The simplest use of output formats is to say how to print a value
7564 already computed. This is done by starting the arguments of the
7565 @code{print} command with a slash and a format letter. The format
7566 letters supported are:
7570 Regard the bits of the value as an integer, and print the integer in
7574 Print as integer in signed decimal.
7577 Print as integer in unsigned decimal.
7580 Print as integer in octal.
7583 Print as integer in binary. The letter @samp{t} stands for ``two''.
7584 @footnote{@samp{b} cannot be used because these format letters are also
7585 used with the @code{x} command, where @samp{b} stands for ``byte'';
7586 see @ref{Memory,,Examining Memory}.}
7589 @cindex unknown address, locating
7590 @cindex locate address
7591 Print as an address, both absolute in hexadecimal and as an offset from
7592 the nearest preceding symbol. You can use this format used to discover
7593 where (in what function) an unknown address is located:
7596 (@value{GDBP}) p/a 0x54320
7597 $3 = 0x54320 <_initialize_vx+396>
7601 The command @code{info symbol 0x54320} yields similar results.
7602 @xref{Symbols, info symbol}.
7605 Regard as an integer and print it as a character constant. This
7606 prints both the numerical value and its character representation. The
7607 character representation is replaced with the octal escape @samp{\nnn}
7608 for characters outside the 7-bit @sc{ascii} range.
7610 Without this format, @value{GDBN} displays @code{char},
7611 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7612 constants. Single-byte members of vectors are displayed as integer
7616 Regard the bits of the value as a floating point number and print
7617 using typical floating point syntax.
7620 @cindex printing strings
7621 @cindex printing byte arrays
7622 Regard as a string, if possible. With this format, pointers to single-byte
7623 data are displayed as null-terminated strings and arrays of single-byte data
7624 are displayed as fixed-length strings. Other values are displayed in their
7627 Without this format, @value{GDBN} displays pointers to and arrays of
7628 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7629 strings. Single-byte members of a vector are displayed as an integer
7633 @cindex raw printing
7634 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7635 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7636 Printing}). This typically results in a higher-level display of the
7637 value's contents. The @samp{r} format bypasses any Python
7638 pretty-printer which might exist.
7641 For example, to print the program counter in hex (@pxref{Registers}), type
7648 Note that no space is required before the slash; this is because command
7649 names in @value{GDBN} cannot contain a slash.
7651 To reprint the last value in the value history with a different format,
7652 you can use the @code{print} command with just a format and no
7653 expression. For example, @samp{p/x} reprints the last value in hex.
7656 @section Examining Memory
7658 You can use the command @code{x} (for ``examine'') to examine memory in
7659 any of several formats, independently of your program's data types.
7661 @cindex examining memory
7663 @kindex x @r{(examine memory)}
7664 @item x/@var{nfu} @var{addr}
7667 Use the @code{x} command to examine memory.
7670 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7671 much memory to display and how to format it; @var{addr} is an
7672 expression giving the address where you want to start displaying memory.
7673 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7674 Several commands set convenient defaults for @var{addr}.
7677 @item @var{n}, the repeat count
7678 The repeat count is a decimal integer; the default is 1. It specifies
7679 how much memory (counting by units @var{u}) to display.
7680 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7683 @item @var{f}, the display format
7684 The display format is one of the formats used by @code{print}
7685 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7686 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7687 The default is @samp{x} (hexadecimal) initially. The default changes
7688 each time you use either @code{x} or @code{print}.
7690 @item @var{u}, the unit size
7691 The unit size is any of
7697 Halfwords (two bytes).
7699 Words (four bytes). This is the initial default.
7701 Giant words (eight bytes).
7704 Each time you specify a unit size with @code{x}, that size becomes the
7705 default unit the next time you use @code{x}. For the @samp{i} format,
7706 the unit size is ignored and is normally not written. For the @samp{s} format,
7707 the unit size defaults to @samp{b}, unless it is explicitly given.
7708 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7709 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7710 Note that the results depend on the programming language of the
7711 current compilation unit. If the language is C, the @samp{s}
7712 modifier will use the UTF-16 encoding while @samp{w} will use
7713 UTF-32. The encoding is set by the programming language and cannot
7716 @item @var{addr}, starting display address
7717 @var{addr} is the address where you want @value{GDBN} to begin displaying
7718 memory. The expression need not have a pointer value (though it may);
7719 it is always interpreted as an integer address of a byte of memory.
7720 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7721 @var{addr} is usually just after the last address examined---but several
7722 other commands also set the default address: @code{info breakpoints} (to
7723 the address of the last breakpoint listed), @code{info line} (to the
7724 starting address of a line), and @code{print} (if you use it to display
7725 a value from memory).
7728 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7729 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7730 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7731 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7732 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7734 Since the letters indicating unit sizes are all distinct from the
7735 letters specifying output formats, you do not have to remember whether
7736 unit size or format comes first; either order works. The output
7737 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7738 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7740 Even though the unit size @var{u} is ignored for the formats @samp{s}
7741 and @samp{i}, you might still want to use a count @var{n}; for example,
7742 @samp{3i} specifies that you want to see three machine instructions,
7743 including any operands. For convenience, especially when used with
7744 the @code{display} command, the @samp{i} format also prints branch delay
7745 slot instructions, if any, beyond the count specified, which immediately
7746 follow the last instruction that is within the count. The command
7747 @code{disassemble} gives an alternative way of inspecting machine
7748 instructions; see @ref{Machine Code,,Source and Machine Code}.
7750 All the defaults for the arguments to @code{x} are designed to make it
7751 easy to continue scanning memory with minimal specifications each time
7752 you use @code{x}. For example, after you have inspected three machine
7753 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7754 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7755 the repeat count @var{n} is used again; the other arguments default as
7756 for successive uses of @code{x}.
7758 When examining machine instructions, the instruction at current program
7759 counter is shown with a @code{=>} marker. For example:
7762 (@value{GDBP}) x/5i $pc-6
7763 0x804837f <main+11>: mov %esp,%ebp
7764 0x8048381 <main+13>: push %ecx
7765 0x8048382 <main+14>: sub $0x4,%esp
7766 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7767 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7770 @cindex @code{$_}, @code{$__}, and value history
7771 The addresses and contents printed by the @code{x} command are not saved
7772 in the value history because there is often too much of them and they
7773 would get in the way. Instead, @value{GDBN} makes these values available for
7774 subsequent use in expressions as values of the convenience variables
7775 @code{$_} and @code{$__}. After an @code{x} command, the last address
7776 examined is available for use in expressions in the convenience variable
7777 @code{$_}. The contents of that address, as examined, are available in
7778 the convenience variable @code{$__}.
7780 If the @code{x} command has a repeat count, the address and contents saved
7781 are from the last memory unit printed; this is not the same as the last
7782 address printed if several units were printed on the last line of output.
7784 @cindex remote memory comparison
7785 @cindex verify remote memory image
7786 When you are debugging a program running on a remote target machine
7787 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7788 remote machine's memory against the executable file you downloaded to
7789 the target. The @code{compare-sections} command is provided for such
7793 @kindex compare-sections
7794 @item compare-sections @r{[}@var{section-name}@r{]}
7795 Compare the data of a loadable section @var{section-name} in the
7796 executable file of the program being debugged with the same section in
7797 the remote machine's memory, and report any mismatches. With no
7798 arguments, compares all loadable sections. This command's
7799 availability depends on the target's support for the @code{"qCRC"}
7804 @section Automatic Display
7805 @cindex automatic display
7806 @cindex display of expressions
7808 If you find that you want to print the value of an expression frequently
7809 (to see how it changes), you might want to add it to the @dfn{automatic
7810 display list} so that @value{GDBN} prints its value each time your program stops.
7811 Each expression added to the list is given a number to identify it;
7812 to remove an expression from the list, you specify that number.
7813 The automatic display looks like this:
7817 3: bar[5] = (struct hack *) 0x3804
7821 This display shows item numbers, expressions and their current values. As with
7822 displays you request manually using @code{x} or @code{print}, you can
7823 specify the output format you prefer; in fact, @code{display} decides
7824 whether to use @code{print} or @code{x} depending your format
7825 specification---it uses @code{x} if you specify either the @samp{i}
7826 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7830 @item display @var{expr}
7831 Add the expression @var{expr} to the list of expressions to display
7832 each time your program stops. @xref{Expressions, ,Expressions}.
7834 @code{display} does not repeat if you press @key{RET} again after using it.
7836 @item display/@var{fmt} @var{expr}
7837 For @var{fmt} specifying only a display format and not a size or
7838 count, add the expression @var{expr} to the auto-display list but
7839 arrange to display it each time in the specified format @var{fmt}.
7840 @xref{Output Formats,,Output Formats}.
7842 @item display/@var{fmt} @var{addr}
7843 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7844 number of units, add the expression @var{addr} as a memory address to
7845 be examined each time your program stops. Examining means in effect
7846 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7849 For example, @samp{display/i $pc} can be helpful, to see the machine
7850 instruction about to be executed each time execution stops (@samp{$pc}
7851 is a common name for the program counter; @pxref{Registers, ,Registers}).
7854 @kindex delete display
7856 @item undisplay @var{dnums}@dots{}
7857 @itemx delete display @var{dnums}@dots{}
7858 Remove items from the list of expressions to display. Specify the
7859 numbers of the displays that you want affected with the command
7860 argument @var{dnums}. It can be a single display number, one of the
7861 numbers shown in the first field of the @samp{info display} display;
7862 or it could be a range of display numbers, as in @code{2-4}.
7864 @code{undisplay} does not repeat if you press @key{RET} after using it.
7865 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7867 @kindex disable display
7868 @item disable display @var{dnums}@dots{}
7869 Disable the display of item numbers @var{dnums}. A disabled display
7870 item is not printed automatically, but is not forgotten. It may be
7871 enabled again later. Specify the numbers of the displays that you
7872 want affected with the command argument @var{dnums}. It can be a
7873 single display number, one of the numbers shown in the first field of
7874 the @samp{info display} display; or it could be a range of display
7875 numbers, as in @code{2-4}.
7877 @kindex enable display
7878 @item enable display @var{dnums}@dots{}
7879 Enable display of item numbers @var{dnums}. It becomes effective once
7880 again in auto display of its expression, until you specify otherwise.
7881 Specify the numbers of the displays that you want affected with the
7882 command argument @var{dnums}. It can be a single display number, one
7883 of the numbers shown in the first field of the @samp{info display}
7884 display; or it could be a range of display numbers, as in @code{2-4}.
7887 Display the current values of the expressions on the list, just as is
7888 done when your program stops.
7890 @kindex info display
7892 Print the list of expressions previously set up to display
7893 automatically, each one with its item number, but without showing the
7894 values. This includes disabled expressions, which are marked as such.
7895 It also includes expressions which would not be displayed right now
7896 because they refer to automatic variables not currently available.
7899 @cindex display disabled out of scope
7900 If a display expression refers to local variables, then it does not make
7901 sense outside the lexical context for which it was set up. Such an
7902 expression is disabled when execution enters a context where one of its
7903 variables is not defined. For example, if you give the command
7904 @code{display last_char} while inside a function with an argument
7905 @code{last_char}, @value{GDBN} displays this argument while your program
7906 continues to stop inside that function. When it stops elsewhere---where
7907 there is no variable @code{last_char}---the display is disabled
7908 automatically. The next time your program stops where @code{last_char}
7909 is meaningful, you can enable the display expression once again.
7911 @node Print Settings
7912 @section Print Settings
7914 @cindex format options
7915 @cindex print settings
7916 @value{GDBN} provides the following ways to control how arrays, structures,
7917 and symbols are printed.
7920 These settings are useful for debugging programs in any language:
7924 @item set print address
7925 @itemx set print address on
7926 @cindex print/don't print memory addresses
7927 @value{GDBN} prints memory addresses showing the location of stack
7928 traces, structure values, pointer values, breakpoints, and so forth,
7929 even when it also displays the contents of those addresses. The default
7930 is @code{on}. For example, this is what a stack frame display looks like with
7931 @code{set print address on}:
7936 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7938 530 if (lquote != def_lquote)
7942 @item set print address off
7943 Do not print addresses when displaying their contents. For example,
7944 this is the same stack frame displayed with @code{set print address off}:
7948 (@value{GDBP}) set print addr off
7950 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7951 530 if (lquote != def_lquote)
7955 You can use @samp{set print address off} to eliminate all machine
7956 dependent displays from the @value{GDBN} interface. For example, with
7957 @code{print address off}, you should get the same text for backtraces on
7958 all machines---whether or not they involve pointer arguments.
7961 @item show print address
7962 Show whether or not addresses are to be printed.
7965 When @value{GDBN} prints a symbolic address, it normally prints the
7966 closest earlier symbol plus an offset. If that symbol does not uniquely
7967 identify the address (for example, it is a name whose scope is a single
7968 source file), you may need to clarify. One way to do this is with
7969 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7970 you can set @value{GDBN} to print the source file and line number when
7971 it prints a symbolic address:
7974 @item set print symbol-filename on
7975 @cindex source file and line of a symbol
7976 @cindex symbol, source file and line
7977 Tell @value{GDBN} to print the source file name and line number of a
7978 symbol in the symbolic form of an address.
7980 @item set print symbol-filename off
7981 Do not print source file name and line number of a symbol. This is the
7984 @item show print symbol-filename
7985 Show whether or not @value{GDBN} will print the source file name and
7986 line number of a symbol in the symbolic form of an address.
7989 Another situation where it is helpful to show symbol filenames and line
7990 numbers is when disassembling code; @value{GDBN} shows you the line
7991 number and source file that corresponds to each instruction.
7993 Also, you may wish to see the symbolic form only if the address being
7994 printed is reasonably close to the closest earlier symbol:
7997 @item set print max-symbolic-offset @var{max-offset}
7998 @cindex maximum value for offset of closest symbol
7999 Tell @value{GDBN} to only display the symbolic form of an address if the
8000 offset between the closest earlier symbol and the address is less than
8001 @var{max-offset}. The default is 0, which tells @value{GDBN}
8002 to always print the symbolic form of an address if any symbol precedes it.
8004 @item show print max-symbolic-offset
8005 Ask how large the maximum offset is that @value{GDBN} prints in a
8009 @cindex wild pointer, interpreting
8010 @cindex pointer, finding referent
8011 If you have a pointer and you are not sure where it points, try
8012 @samp{set print symbol-filename on}. Then you can determine the name
8013 and source file location of the variable where it points, using
8014 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8015 For example, here @value{GDBN} shows that a variable @code{ptt} points
8016 at another variable @code{t}, defined in @file{hi2.c}:
8019 (@value{GDBP}) set print symbol-filename on
8020 (@value{GDBP}) p/a ptt
8021 $4 = 0xe008 <t in hi2.c>
8025 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8026 does not show the symbol name and filename of the referent, even with
8027 the appropriate @code{set print} options turned on.
8030 Other settings control how different kinds of objects are printed:
8033 @item set print array
8034 @itemx set print array on
8035 @cindex pretty print arrays
8036 Pretty print arrays. This format is more convenient to read,
8037 but uses more space. The default is off.
8039 @item set print array off
8040 Return to compressed format for arrays.
8042 @item show print array
8043 Show whether compressed or pretty format is selected for displaying
8046 @cindex print array indexes
8047 @item set print array-indexes
8048 @itemx set print array-indexes on
8049 Print the index of each element when displaying arrays. May be more
8050 convenient to locate a given element in the array or quickly find the
8051 index of a given element in that printed array. The default is off.
8053 @item set print array-indexes off
8054 Stop printing element indexes when displaying arrays.
8056 @item show print array-indexes
8057 Show whether the index of each element is printed when displaying
8060 @item set print elements @var{number-of-elements}
8061 @cindex number of array elements to print
8062 @cindex limit on number of printed array elements
8063 Set a limit on how many elements of an array @value{GDBN} will print.
8064 If @value{GDBN} is printing a large array, it stops printing after it has
8065 printed the number of elements set by the @code{set print elements} command.
8066 This limit also applies to the display of strings.
8067 When @value{GDBN} starts, this limit is set to 200.
8068 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8070 @item show print elements
8071 Display the number of elements of a large array that @value{GDBN} will print.
8072 If the number is 0, then the printing is unlimited.
8074 @item set print frame-arguments @var{value}
8075 @kindex set print frame-arguments
8076 @cindex printing frame argument values
8077 @cindex print all frame argument values
8078 @cindex print frame argument values for scalars only
8079 @cindex do not print frame argument values
8080 This command allows to control how the values of arguments are printed
8081 when the debugger prints a frame (@pxref{Frames}). The possible
8086 The values of all arguments are printed.
8089 Print the value of an argument only if it is a scalar. The value of more
8090 complex arguments such as arrays, structures, unions, etc, is replaced
8091 by @code{@dots{}}. This is the default. Here is an example where
8092 only scalar arguments are shown:
8095 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8100 None of the argument values are printed. Instead, the value of each argument
8101 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8104 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8109 By default, only scalar arguments are printed. This command can be used
8110 to configure the debugger to print the value of all arguments, regardless
8111 of their type. However, it is often advantageous to not print the value
8112 of more complex parameters. For instance, it reduces the amount of
8113 information printed in each frame, making the backtrace more readable.
8114 Also, it improves performance when displaying Ada frames, because
8115 the computation of large arguments can sometimes be CPU-intensive,
8116 especially in large applications. Setting @code{print frame-arguments}
8117 to @code{scalars} (the default) or @code{none} avoids this computation,
8118 thus speeding up the display of each Ada frame.
8120 @item show print frame-arguments
8121 Show how the value of arguments should be displayed when printing a frame.
8123 @anchor{set print entry-values}
8124 @item set print entry-values @var{value}
8125 @kindex set print entry-values
8126 Set printing of frame argument values at function entry. In some cases
8127 @value{GDBN} can determine the value of function argument which was passed by
8128 the function caller, even if the value was modified inside the called function
8129 and therefore is different. With optimized code, the current value could be
8130 unavailable, but the entry value may still be known.
8132 The default value is @code{default} (see below for its description). Older
8133 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8134 this feature will behave in the @code{default} setting the same way as with the
8137 This functionality is currently supported only by DWARF 2 debugging format and
8138 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8139 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8142 The @var{value} parameter can be one of the following:
8146 Print only actual parameter values, never print values from function entry
8150 #0 different (val=6)
8151 #0 lost (val=<optimized out>)
8153 #0 invalid (val=<optimized out>)
8157 Print only parameter values from function entry point. The actual parameter
8158 values are never printed.
8160 #0 equal (val@@entry=5)
8161 #0 different (val@@entry=5)
8162 #0 lost (val@@entry=5)
8163 #0 born (val@@entry=<optimized out>)
8164 #0 invalid (val@@entry=<optimized out>)
8168 Print only parameter values from function entry point. If value from function
8169 entry point is not known while the actual value is known, print the actual
8170 value for such parameter.
8172 #0 equal (val@@entry=5)
8173 #0 different (val@@entry=5)
8174 #0 lost (val@@entry=5)
8176 #0 invalid (val@@entry=<optimized out>)
8180 Print actual parameter values. If actual parameter value is not known while
8181 value from function entry point is known, print the entry point value for such
8185 #0 different (val=6)
8186 #0 lost (val@@entry=5)
8188 #0 invalid (val=<optimized out>)
8192 Always print both the actual parameter value and its value from function entry
8193 point, even if values of one or both are not available due to compiler
8196 #0 equal (val=5, val@@entry=5)
8197 #0 different (val=6, val@@entry=5)
8198 #0 lost (val=<optimized out>, val@@entry=5)
8199 #0 born (val=10, val@@entry=<optimized out>)
8200 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8204 Print the actual parameter value if it is known and also its value from
8205 function entry point if it is known. If neither is known, print for the actual
8206 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8207 values are known and identical, print the shortened
8208 @code{param=param@@entry=VALUE} notation.
8210 #0 equal (val=val@@entry=5)
8211 #0 different (val=6, val@@entry=5)
8212 #0 lost (val@@entry=5)
8214 #0 invalid (val=<optimized out>)
8218 Always print the actual parameter value. Print also its value from function
8219 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8220 if both values are known and identical, print the shortened
8221 @code{param=param@@entry=VALUE} notation.
8223 #0 equal (val=val@@entry=5)
8224 #0 different (val=6, val@@entry=5)
8225 #0 lost (val=<optimized out>, val@@entry=5)
8227 #0 invalid (val=<optimized out>)
8231 For analysis messages on possible failures of frame argument values at function
8232 entry resolution see @ref{set debug entry-values}.
8234 @item show print entry-values
8235 Show the method being used for printing of frame argument values at function
8238 @item set print repeats
8239 @cindex repeated array elements
8240 Set the threshold for suppressing display of repeated array
8241 elements. When the number of consecutive identical elements of an
8242 array exceeds the threshold, @value{GDBN} prints the string
8243 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8244 identical repetitions, instead of displaying the identical elements
8245 themselves. Setting the threshold to zero will cause all elements to
8246 be individually printed. The default threshold is 10.
8248 @item show print repeats
8249 Display the current threshold for printing repeated identical
8252 @item set print null-stop
8253 @cindex @sc{null} elements in arrays
8254 Cause @value{GDBN} to stop printing the characters of an array when the first
8255 @sc{null} is encountered. This is useful when large arrays actually
8256 contain only short strings.
8259 @item show print null-stop
8260 Show whether @value{GDBN} stops printing an array on the first
8261 @sc{null} character.
8263 @item set print pretty on
8264 @cindex print structures in indented form
8265 @cindex indentation in structure display
8266 Cause @value{GDBN} to print structures in an indented format with one member
8267 per line, like this:
8282 @item set print pretty off
8283 Cause @value{GDBN} to print structures in a compact format, like this:
8287 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8288 meat = 0x54 "Pork"@}
8293 This is the default format.
8295 @item show print pretty
8296 Show which format @value{GDBN} is using to print structures.
8298 @item set print sevenbit-strings on
8299 @cindex eight-bit characters in strings
8300 @cindex octal escapes in strings
8301 Print using only seven-bit characters; if this option is set,
8302 @value{GDBN} displays any eight-bit characters (in strings or
8303 character values) using the notation @code{\}@var{nnn}. This setting is
8304 best if you are working in English (@sc{ascii}) and you use the
8305 high-order bit of characters as a marker or ``meta'' bit.
8307 @item set print sevenbit-strings off
8308 Print full eight-bit characters. This allows the use of more
8309 international character sets, and is the default.
8311 @item show print sevenbit-strings
8312 Show whether or not @value{GDBN} is printing only seven-bit characters.
8314 @item set print union on
8315 @cindex unions in structures, printing
8316 Tell @value{GDBN} to print unions which are contained in structures
8317 and other unions. This is the default setting.
8319 @item set print union off
8320 Tell @value{GDBN} not to print unions which are contained in
8321 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8324 @item show print union
8325 Ask @value{GDBN} whether or not it will print unions which are contained in
8326 structures and other unions.
8328 For example, given the declarations
8331 typedef enum @{Tree, Bug@} Species;
8332 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8333 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8344 struct thing foo = @{Tree, @{Acorn@}@};
8348 with @code{set print union on} in effect @samp{p foo} would print
8351 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8355 and with @code{set print union off} in effect it would print
8358 $1 = @{it = Tree, form = @{...@}@}
8362 @code{set print union} affects programs written in C-like languages
8368 These settings are of interest when debugging C@t{++} programs:
8371 @cindex demangling C@t{++} names
8372 @item set print demangle
8373 @itemx set print demangle on
8374 Print C@t{++} names in their source form rather than in the encoded
8375 (``mangled'') form passed to the assembler and linker for type-safe
8376 linkage. The default is on.
8378 @item show print demangle
8379 Show whether C@t{++} names are printed in mangled or demangled form.
8381 @item set print asm-demangle
8382 @itemx set print asm-demangle on
8383 Print C@t{++} names in their source form rather than their mangled form, even
8384 in assembler code printouts such as instruction disassemblies.
8387 @item show print asm-demangle
8388 Show whether C@t{++} names in assembly listings are printed in mangled
8391 @cindex C@t{++} symbol decoding style
8392 @cindex symbol decoding style, C@t{++}
8393 @kindex set demangle-style
8394 @item set demangle-style @var{style}
8395 Choose among several encoding schemes used by different compilers to
8396 represent C@t{++} names. The choices for @var{style} are currently:
8400 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8403 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8404 This is the default.
8407 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8410 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8413 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8414 @strong{Warning:} this setting alone is not sufficient to allow
8415 debugging @code{cfront}-generated executables. @value{GDBN} would
8416 require further enhancement to permit that.
8419 If you omit @var{style}, you will see a list of possible formats.
8421 @item show demangle-style
8422 Display the encoding style currently in use for decoding C@t{++} symbols.
8424 @item set print object
8425 @itemx set print object on
8426 @cindex derived type of an object, printing
8427 @cindex display derived types
8428 When displaying a pointer to an object, identify the @emph{actual}
8429 (derived) type of the object rather than the @emph{declared} type, using
8430 the virtual function table. Note that the virtual function table is
8431 required---this feature can only work for objects that have run-time
8432 type identification; a single virtual method in the object's declared
8435 @item set print object off
8436 Display only the declared type of objects, without reference to the
8437 virtual function table. This is the default setting.
8439 @item show print object
8440 Show whether actual, or declared, object types are displayed.
8442 @item set print static-members
8443 @itemx set print static-members on
8444 @cindex static members of C@t{++} objects
8445 Print static members when displaying a C@t{++} object. The default is on.
8447 @item set print static-members off
8448 Do not print static members when displaying a C@t{++} object.
8450 @item show print static-members
8451 Show whether C@t{++} static members are printed or not.
8453 @item set print pascal_static-members
8454 @itemx set print pascal_static-members on
8455 @cindex static members of Pascal objects
8456 @cindex Pascal objects, static members display
8457 Print static members when displaying a Pascal object. The default is on.
8459 @item set print pascal_static-members off
8460 Do not print static members when displaying a Pascal object.
8462 @item show print pascal_static-members
8463 Show whether Pascal static members are printed or not.
8465 @c These don't work with HP ANSI C++ yet.
8466 @item set print vtbl
8467 @itemx set print vtbl on
8468 @cindex pretty print C@t{++} virtual function tables
8469 @cindex virtual functions (C@t{++}) display
8470 @cindex VTBL display
8471 Pretty print C@t{++} virtual function tables. The default is off.
8472 (The @code{vtbl} commands do not work on programs compiled with the HP
8473 ANSI C@t{++} compiler (@code{aCC}).)
8475 @item set print vtbl off
8476 Do not pretty print C@t{++} virtual function tables.
8478 @item show print vtbl
8479 Show whether C@t{++} virtual function tables are pretty printed, or not.
8482 @node Pretty Printing
8483 @section Pretty Printing
8485 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8486 Python code. It greatly simplifies the display of complex objects. This
8487 mechanism works for both MI and the CLI.
8490 * Pretty-Printer Introduction:: Introduction to pretty-printers
8491 * Pretty-Printer Example:: An example pretty-printer
8492 * Pretty-Printer Commands:: Pretty-printer commands
8495 @node Pretty-Printer Introduction
8496 @subsection Pretty-Printer Introduction
8498 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8499 registered for the value. If there is then @value{GDBN} invokes the
8500 pretty-printer to print the value. Otherwise the value is printed normally.
8502 Pretty-printers are normally named. This makes them easy to manage.
8503 The @samp{info pretty-printer} command will list all the installed
8504 pretty-printers with their names.
8505 If a pretty-printer can handle multiple data types, then its
8506 @dfn{subprinters} are the printers for the individual data types.
8507 Each such subprinter has its own name.
8508 The format of the name is @var{printer-name};@var{subprinter-name}.
8510 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8511 Typically they are automatically loaded and registered when the corresponding
8512 debug information is loaded, thus making them available without having to
8513 do anything special.
8515 There are three places where a pretty-printer can be registered.
8519 Pretty-printers registered globally are available when debugging
8523 Pretty-printers registered with a program space are available only
8524 when debugging that program.
8525 @xref{Progspaces In Python}, for more details on program spaces in Python.
8528 Pretty-printers registered with an objfile are loaded and unloaded
8529 with the corresponding objfile (e.g., shared library).
8530 @xref{Objfiles In Python}, for more details on objfiles in Python.
8533 @xref{Selecting Pretty-Printers}, for further information on how
8534 pretty-printers are selected,
8536 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8539 @node Pretty-Printer Example
8540 @subsection Pretty-Printer Example
8542 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8545 (@value{GDBP}) print s
8547 static npos = 4294967295,
8549 <std::allocator<char>> = @{
8550 <__gnu_cxx::new_allocator<char>> = @{
8551 <No data fields>@}, <No data fields>
8553 members of std::basic_string<char, std::char_traits<char>,
8554 std::allocator<char> >::_Alloc_hider:
8555 _M_p = 0x804a014 "abcd"
8560 With a pretty-printer for @code{std::string} only the contents are printed:
8563 (@value{GDBP}) print s
8567 @node Pretty-Printer Commands
8568 @subsection Pretty-Printer Commands
8569 @cindex pretty-printer commands
8572 @kindex info pretty-printer
8573 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8574 Print the list of installed pretty-printers.
8575 This includes disabled pretty-printers, which are marked as such.
8577 @var{object-regexp} is a regular expression matching the objects
8578 whose pretty-printers to list.
8579 Objects can be @code{global}, the program space's file
8580 (@pxref{Progspaces In Python}),
8581 and the object files within that program space (@pxref{Objfiles In Python}).
8582 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8583 looks up a printer from these three objects.
8585 @var{name-regexp} is a regular expression matching the name of the printers
8588 @kindex disable pretty-printer
8589 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8590 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8591 A disabled pretty-printer is not forgotten, it may be enabled again later.
8593 @kindex enable pretty-printer
8594 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8595 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8600 Suppose we have three pretty-printers installed: one from library1.so
8601 named @code{foo} that prints objects of type @code{foo}, and
8602 another from library2.so named @code{bar} that prints two types of objects,
8603 @code{bar1} and @code{bar2}.
8606 (gdb) info pretty-printer
8613 (gdb) info pretty-printer library2
8618 (gdb) disable pretty-printer library1
8620 2 of 3 printers enabled
8621 (gdb) info pretty-printer
8628 (gdb) disable pretty-printer library2 bar:bar1
8630 1 of 3 printers enabled
8631 (gdb) info pretty-printer library2
8638 (gdb) disable pretty-printer library2 bar
8640 0 of 3 printers enabled
8641 (gdb) info pretty-printer library2
8650 Note that for @code{bar} the entire printer can be disabled,
8651 as can each individual subprinter.
8654 @section Value History
8656 @cindex value history
8657 @cindex history of values printed by @value{GDBN}
8658 Values printed by the @code{print} command are saved in the @value{GDBN}
8659 @dfn{value history}. This allows you to refer to them in other expressions.
8660 Values are kept until the symbol table is re-read or discarded
8661 (for example with the @code{file} or @code{symbol-file} commands).
8662 When the symbol table changes, the value history is discarded,
8663 since the values may contain pointers back to the types defined in the
8668 @cindex history number
8669 The values printed are given @dfn{history numbers} by which you can
8670 refer to them. These are successive integers starting with one.
8671 @code{print} shows you the history number assigned to a value by
8672 printing @samp{$@var{num} = } before the value; here @var{num} is the
8675 To refer to any previous value, use @samp{$} followed by the value's
8676 history number. The way @code{print} labels its output is designed to
8677 remind you of this. Just @code{$} refers to the most recent value in
8678 the history, and @code{$$} refers to the value before that.
8679 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8680 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8681 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8683 For example, suppose you have just printed a pointer to a structure and
8684 want to see the contents of the structure. It suffices to type
8690 If you have a chain of structures where the component @code{next} points
8691 to the next one, you can print the contents of the next one with this:
8698 You can print successive links in the chain by repeating this
8699 command---which you can do by just typing @key{RET}.
8701 Note that the history records values, not expressions. If the value of
8702 @code{x} is 4 and you type these commands:
8710 then the value recorded in the value history by the @code{print} command
8711 remains 4 even though the value of @code{x} has changed.
8716 Print the last ten values in the value history, with their item numbers.
8717 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8718 values} does not change the history.
8720 @item show values @var{n}
8721 Print ten history values centered on history item number @var{n}.
8724 Print ten history values just after the values last printed. If no more
8725 values are available, @code{show values +} produces no display.
8728 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8729 same effect as @samp{show values +}.
8731 @node Convenience Vars
8732 @section Convenience Variables
8734 @cindex convenience variables
8735 @cindex user-defined variables
8736 @value{GDBN} provides @dfn{convenience variables} that you can use within
8737 @value{GDBN} to hold on to a value and refer to it later. These variables
8738 exist entirely within @value{GDBN}; they are not part of your program, and
8739 setting a convenience variable has no direct effect on further execution
8740 of your program. That is why you can use them freely.
8742 Convenience variables are prefixed with @samp{$}. Any name preceded by
8743 @samp{$} can be used for a convenience variable, unless it is one of
8744 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8745 (Value history references, in contrast, are @emph{numbers} preceded
8746 by @samp{$}. @xref{Value History, ,Value History}.)
8748 You can save a value in a convenience variable with an assignment
8749 expression, just as you would set a variable in your program.
8753 set $foo = *object_ptr
8757 would save in @code{$foo} the value contained in the object pointed to by
8760 Using a convenience variable for the first time creates it, but its
8761 value is @code{void} until you assign a new value. You can alter the
8762 value with another assignment at any time.
8764 Convenience variables have no fixed types. You can assign a convenience
8765 variable any type of value, including structures and arrays, even if
8766 that variable already has a value of a different type. The convenience
8767 variable, when used as an expression, has the type of its current value.
8770 @kindex show convenience
8771 @cindex show all user variables
8772 @item show convenience
8773 Print a list of convenience variables used so far, and their values.
8774 Abbreviated @code{show conv}.
8776 @kindex init-if-undefined
8777 @cindex convenience variables, initializing
8778 @item init-if-undefined $@var{variable} = @var{expression}
8779 Set a convenience variable if it has not already been set. This is useful
8780 for user-defined commands that keep some state. It is similar, in concept,
8781 to using local static variables with initializers in C (except that
8782 convenience variables are global). It can also be used to allow users to
8783 override default values used in a command script.
8785 If the variable is already defined then the expression is not evaluated so
8786 any side-effects do not occur.
8789 One of the ways to use a convenience variable is as a counter to be
8790 incremented or a pointer to be advanced. For example, to print
8791 a field from successive elements of an array of structures:
8795 print bar[$i++]->contents
8799 Repeat that command by typing @key{RET}.
8801 Some convenience variables are created automatically by @value{GDBN} and given
8802 values likely to be useful.
8805 @vindex $_@r{, convenience variable}
8807 The variable @code{$_} is automatically set by the @code{x} command to
8808 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8809 commands which provide a default address for @code{x} to examine also
8810 set @code{$_} to that address; these commands include @code{info line}
8811 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8812 except when set by the @code{x} command, in which case it is a pointer
8813 to the type of @code{$__}.
8815 @vindex $__@r{, convenience variable}
8817 The variable @code{$__} is automatically set by the @code{x} command
8818 to the value found in the last address examined. Its type is chosen
8819 to match the format in which the data was printed.
8822 @vindex $_exitcode@r{, convenience variable}
8823 The variable @code{$_exitcode} is automatically set to the exit code when
8824 the program being debugged terminates.
8827 @vindex $_sdata@r{, inspect, convenience variable}
8828 The variable @code{$_sdata} contains extra collected static tracepoint
8829 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8830 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8831 if extra static tracepoint data has not been collected.
8834 @vindex $_siginfo@r{, convenience variable}
8835 The variable @code{$_siginfo} contains extra signal information
8836 (@pxref{extra signal information}). Note that @code{$_siginfo}
8837 could be empty, if the application has not yet received any signals.
8838 For example, it will be empty before you execute the @code{run} command.
8841 @vindex $_tlb@r{, convenience variable}
8842 The variable @code{$_tlb} is automatically set when debugging
8843 applications running on MS-Windows in native mode or connected to
8844 gdbserver that supports the @code{qGetTIBAddr} request.
8845 @xref{General Query Packets}.
8846 This variable contains the address of the thread information block.
8850 On HP-UX systems, if you refer to a function or variable name that
8851 begins with a dollar sign, @value{GDBN} searches for a user or system
8852 name first, before it searches for a convenience variable.
8854 @cindex convenience functions
8855 @value{GDBN} also supplies some @dfn{convenience functions}. These
8856 have a syntax similar to convenience variables. A convenience
8857 function can be used in an expression just like an ordinary function;
8858 however, a convenience function is implemented internally to
8863 @kindex help function
8864 @cindex show all convenience functions
8865 Print a list of all convenience functions.
8872 You can refer to machine register contents, in expressions, as variables
8873 with names starting with @samp{$}. The names of registers are different
8874 for each machine; use @code{info registers} to see the names used on
8878 @kindex info registers
8879 @item info registers
8880 Print the names and values of all registers except floating-point
8881 and vector registers (in the selected stack frame).
8883 @kindex info all-registers
8884 @cindex floating point registers
8885 @item info all-registers
8886 Print the names and values of all registers, including floating-point
8887 and vector registers (in the selected stack frame).
8889 @item info registers @var{regname} @dots{}
8890 Print the @dfn{relativized} value of each specified register @var{regname}.
8891 As discussed in detail below, register values are normally relative to
8892 the selected stack frame. @var{regname} may be any register name valid on
8893 the machine you are using, with or without the initial @samp{$}.
8896 @cindex stack pointer register
8897 @cindex program counter register
8898 @cindex process status register
8899 @cindex frame pointer register
8900 @cindex standard registers
8901 @value{GDBN} has four ``standard'' register names that are available (in
8902 expressions) on most machines---whenever they do not conflict with an
8903 architecture's canonical mnemonics for registers. The register names
8904 @code{$pc} and @code{$sp} are used for the program counter register and
8905 the stack pointer. @code{$fp} is used for a register that contains a
8906 pointer to the current stack frame, and @code{$ps} is used for a
8907 register that contains the processor status. For example,
8908 you could print the program counter in hex with
8915 or print the instruction to be executed next with
8922 or add four to the stack pointer@footnote{This is a way of removing
8923 one word from the stack, on machines where stacks grow downward in
8924 memory (most machines, nowadays). This assumes that the innermost
8925 stack frame is selected; setting @code{$sp} is not allowed when other
8926 stack frames are selected. To pop entire frames off the stack,
8927 regardless of machine architecture, use @code{return};
8928 see @ref{Returning, ,Returning from a Function}.} with
8934 Whenever possible, these four standard register names are available on
8935 your machine even though the machine has different canonical mnemonics,
8936 so long as there is no conflict. The @code{info registers} command
8937 shows the canonical names. For example, on the SPARC, @code{info
8938 registers} displays the processor status register as @code{$psr} but you
8939 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8940 is an alias for the @sc{eflags} register.
8942 @value{GDBN} always considers the contents of an ordinary register as an
8943 integer when the register is examined in this way. Some machines have
8944 special registers which can hold nothing but floating point; these
8945 registers are considered to have floating point values. There is no way
8946 to refer to the contents of an ordinary register as floating point value
8947 (although you can @emph{print} it as a floating point value with
8948 @samp{print/f $@var{regname}}).
8950 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8951 means that the data format in which the register contents are saved by
8952 the operating system is not the same one that your program normally
8953 sees. For example, the registers of the 68881 floating point
8954 coprocessor are always saved in ``extended'' (raw) format, but all C
8955 programs expect to work with ``double'' (virtual) format. In such
8956 cases, @value{GDBN} normally works with the virtual format only (the format
8957 that makes sense for your program), but the @code{info registers} command
8958 prints the data in both formats.
8960 @cindex SSE registers (x86)
8961 @cindex MMX registers (x86)
8962 Some machines have special registers whose contents can be interpreted
8963 in several different ways. For example, modern x86-based machines
8964 have SSE and MMX registers that can hold several values packed
8965 together in several different formats. @value{GDBN} refers to such
8966 registers in @code{struct} notation:
8969 (@value{GDBP}) print $xmm1
8971 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8972 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8973 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8974 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8975 v4_int32 = @{0, 20657912, 11, 13@},
8976 v2_int64 = @{88725056443645952, 55834574859@},
8977 uint128 = 0x0000000d0000000b013b36f800000000
8982 To set values of such registers, you need to tell @value{GDBN} which
8983 view of the register you wish to change, as if you were assigning
8984 value to a @code{struct} member:
8987 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8990 Normally, register values are relative to the selected stack frame
8991 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8992 value that the register would contain if all stack frames farther in
8993 were exited and their saved registers restored. In order to see the
8994 true contents of hardware registers, you must select the innermost
8995 frame (with @samp{frame 0}).
8997 However, @value{GDBN} must deduce where registers are saved, from the machine
8998 code generated by your compiler. If some registers are not saved, or if
8999 @value{GDBN} is unable to locate the saved registers, the selected stack
9000 frame makes no difference.
9002 @node Floating Point Hardware
9003 @section Floating Point Hardware
9004 @cindex floating point
9006 Depending on the configuration, @value{GDBN} may be able to give
9007 you more information about the status of the floating point hardware.
9012 Display hardware-dependent information about the floating
9013 point unit. The exact contents and layout vary depending on the
9014 floating point chip. Currently, @samp{info float} is supported on
9015 the ARM and x86 machines.
9019 @section Vector Unit
9022 Depending on the configuration, @value{GDBN} may be able to give you
9023 more information about the status of the vector unit.
9028 Display information about the vector unit. The exact contents and
9029 layout vary depending on the hardware.
9032 @node OS Information
9033 @section Operating System Auxiliary Information
9034 @cindex OS information
9036 @value{GDBN} provides interfaces to useful OS facilities that can help
9037 you debug your program.
9039 @cindex @code{ptrace} system call
9040 @cindex @code{struct user} contents
9041 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9042 machines), it interfaces with the inferior via the @code{ptrace}
9043 system call. The operating system creates a special sata structure,
9044 called @code{struct user}, for this interface. You can use the
9045 command @code{info udot} to display the contents of this data
9051 Display the contents of the @code{struct user} maintained by the OS
9052 kernel for the program being debugged. @value{GDBN} displays the
9053 contents of @code{struct user} as a list of hex numbers, similar to
9054 the @code{examine} command.
9057 @cindex auxiliary vector
9058 @cindex vector, auxiliary
9059 Some operating systems supply an @dfn{auxiliary vector} to programs at
9060 startup. This is akin to the arguments and environment that you
9061 specify for a program, but contains a system-dependent variety of
9062 binary values that tell system libraries important details about the
9063 hardware, operating system, and process. Each value's purpose is
9064 identified by an integer tag; the meanings are well-known but system-specific.
9065 Depending on the configuration and operating system facilities,
9066 @value{GDBN} may be able to show you this information. For remote
9067 targets, this functionality may further depend on the remote stub's
9068 support of the @samp{qXfer:auxv:read} packet, see
9069 @ref{qXfer auxiliary vector read}.
9074 Display the auxiliary vector of the inferior, which can be either a
9075 live process or a core dump file. @value{GDBN} prints each tag value
9076 numerically, and also shows names and text descriptions for recognized
9077 tags. Some values in the vector are numbers, some bit masks, and some
9078 pointers to strings or other data. @value{GDBN} displays each value in the
9079 most appropriate form for a recognized tag, and in hexadecimal for
9080 an unrecognized tag.
9083 On some targets, @value{GDBN} can access operating-system-specific information
9084 and display it to user, without interpretation. For remote targets,
9085 this functionality depends on the remote stub's support of the
9086 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9091 List the types of OS information available for the target. If the
9092 target does not return a list of possible types, this command will
9095 @kindex info os processes
9096 @item info os processes
9097 Display the list of processes on the target. For each process,
9098 @value{GDBN} prints the process identifier, the name of the user, and
9099 the command corresponding to the process.
9102 @node Memory Region Attributes
9103 @section Memory Region Attributes
9104 @cindex memory region attributes
9106 @dfn{Memory region attributes} allow you to describe special handling
9107 required by regions of your target's memory. @value{GDBN} uses
9108 attributes to determine whether to allow certain types of memory
9109 accesses; whether to use specific width accesses; and whether to cache
9110 target memory. By default the description of memory regions is
9111 fetched from the target (if the current target supports this), but the
9112 user can override the fetched regions.
9114 Defined memory regions can be individually enabled and disabled. When a
9115 memory region is disabled, @value{GDBN} uses the default attributes when
9116 accessing memory in that region. Similarly, if no memory regions have
9117 been defined, @value{GDBN} uses the default attributes when accessing
9120 When a memory region is defined, it is given a number to identify it;
9121 to enable, disable, or remove a memory region, you specify that number.
9125 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9126 Define a memory region bounded by @var{lower} and @var{upper} with
9127 attributes @var{attributes}@dots{}, and add it to the list of regions
9128 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9129 case: it is treated as the target's maximum memory address.
9130 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9133 Discard any user changes to the memory regions and use target-supplied
9134 regions, if available, or no regions if the target does not support.
9137 @item delete mem @var{nums}@dots{}
9138 Remove memory regions @var{nums}@dots{} from the list of regions
9139 monitored by @value{GDBN}.
9142 @item disable mem @var{nums}@dots{}
9143 Disable monitoring of memory regions @var{nums}@dots{}.
9144 A disabled memory region is not forgotten.
9145 It may be enabled again later.
9148 @item enable mem @var{nums}@dots{}
9149 Enable monitoring of memory regions @var{nums}@dots{}.
9153 Print a table of all defined memory regions, with the following columns
9157 @item Memory Region Number
9158 @item Enabled or Disabled.
9159 Enabled memory regions are marked with @samp{y}.
9160 Disabled memory regions are marked with @samp{n}.
9163 The address defining the inclusive lower bound of the memory region.
9166 The address defining the exclusive upper bound of the memory region.
9169 The list of attributes set for this memory region.
9174 @subsection Attributes
9176 @subsubsection Memory Access Mode
9177 The access mode attributes set whether @value{GDBN} may make read or
9178 write accesses to a memory region.
9180 While these attributes prevent @value{GDBN} from performing invalid
9181 memory accesses, they do nothing to prevent the target system, I/O DMA,
9182 etc.@: from accessing memory.
9186 Memory is read only.
9188 Memory is write only.
9190 Memory is read/write. This is the default.
9193 @subsubsection Memory Access Size
9194 The access size attribute tells @value{GDBN} to use specific sized
9195 accesses in the memory region. Often memory mapped device registers
9196 require specific sized accesses. If no access size attribute is
9197 specified, @value{GDBN} may use accesses of any size.
9201 Use 8 bit memory accesses.
9203 Use 16 bit memory accesses.
9205 Use 32 bit memory accesses.
9207 Use 64 bit memory accesses.
9210 @c @subsubsection Hardware/Software Breakpoints
9211 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9212 @c will use hardware or software breakpoints for the internal breakpoints
9213 @c used by the step, next, finish, until, etc. commands.
9217 @c Always use hardware breakpoints
9218 @c @item swbreak (default)
9221 @subsubsection Data Cache
9222 The data cache attributes set whether @value{GDBN} will cache target
9223 memory. While this generally improves performance by reducing debug
9224 protocol overhead, it can lead to incorrect results because @value{GDBN}
9225 does not know about volatile variables or memory mapped device
9230 Enable @value{GDBN} to cache target memory.
9232 Disable @value{GDBN} from caching target memory. This is the default.
9235 @subsection Memory Access Checking
9236 @value{GDBN} can be instructed to refuse accesses to memory that is
9237 not explicitly described. This can be useful if accessing such
9238 regions has undesired effects for a specific target, or to provide
9239 better error checking. The following commands control this behaviour.
9242 @kindex set mem inaccessible-by-default
9243 @item set mem inaccessible-by-default [on|off]
9244 If @code{on} is specified, make @value{GDBN} treat memory not
9245 explicitly described by the memory ranges as non-existent and refuse accesses
9246 to such memory. The checks are only performed if there's at least one
9247 memory range defined. If @code{off} is specified, make @value{GDBN}
9248 treat the memory not explicitly described by the memory ranges as RAM.
9249 The default value is @code{on}.
9250 @kindex show mem inaccessible-by-default
9251 @item show mem inaccessible-by-default
9252 Show the current handling of accesses to unknown memory.
9256 @c @subsubsection Memory Write Verification
9257 @c The memory write verification attributes set whether @value{GDBN}
9258 @c will re-reads data after each write to verify the write was successful.
9262 @c @item noverify (default)
9265 @node Dump/Restore Files
9266 @section Copy Between Memory and a File
9267 @cindex dump/restore files
9268 @cindex append data to a file
9269 @cindex dump data to a file
9270 @cindex restore data from a file
9272 You can use the commands @code{dump}, @code{append}, and
9273 @code{restore} to copy data between target memory and a file. The
9274 @code{dump} and @code{append} commands write data to a file, and the
9275 @code{restore} command reads data from a file back into the inferior's
9276 memory. Files may be in binary, Motorola S-record, Intel hex, or
9277 Tektronix Hex format; however, @value{GDBN} can only append to binary
9283 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9284 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9285 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9286 or the value of @var{expr}, to @var{filename} in the given format.
9288 The @var{format} parameter may be any one of:
9295 Motorola S-record format.
9297 Tektronix Hex format.
9300 @value{GDBN} uses the same definitions of these formats as the
9301 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9302 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9306 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9307 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9308 Append the contents of memory from @var{start_addr} to @var{end_addr},
9309 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9310 (@value{GDBN} can only append data to files in raw binary form.)
9313 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9314 Restore the contents of file @var{filename} into memory. The
9315 @code{restore} command can automatically recognize any known @sc{bfd}
9316 file format, except for raw binary. To restore a raw binary file you
9317 must specify the optional keyword @code{binary} after the filename.
9319 If @var{bias} is non-zero, its value will be added to the addresses
9320 contained in the file. Binary files always start at address zero, so
9321 they will be restored at address @var{bias}. Other bfd files have
9322 a built-in location; they will be restored at offset @var{bias}
9325 If @var{start} and/or @var{end} are non-zero, then only data between
9326 file offset @var{start} and file offset @var{end} will be restored.
9327 These offsets are relative to the addresses in the file, before
9328 the @var{bias} argument is applied.
9332 @node Core File Generation
9333 @section How to Produce a Core File from Your Program
9334 @cindex dump core from inferior
9336 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9337 image of a running process and its process status (register values
9338 etc.). Its primary use is post-mortem debugging of a program that
9339 crashed while it ran outside a debugger. A program that crashes
9340 automatically produces a core file, unless this feature is disabled by
9341 the user. @xref{Files}, for information on invoking @value{GDBN} in
9342 the post-mortem debugging mode.
9344 Occasionally, you may wish to produce a core file of the program you
9345 are debugging in order to preserve a snapshot of its state.
9346 @value{GDBN} has a special command for that.
9350 @kindex generate-core-file
9351 @item generate-core-file [@var{file}]
9352 @itemx gcore [@var{file}]
9353 Produce a core dump of the inferior process. The optional argument
9354 @var{file} specifies the file name where to put the core dump. If not
9355 specified, the file name defaults to @file{core.@var{pid}}, where
9356 @var{pid} is the inferior process ID.
9358 Note that this command is implemented only for some systems (as of
9359 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9362 @node Character Sets
9363 @section Character Sets
9364 @cindex character sets
9366 @cindex translating between character sets
9367 @cindex host character set
9368 @cindex target character set
9370 If the program you are debugging uses a different character set to
9371 represent characters and strings than the one @value{GDBN} uses itself,
9372 @value{GDBN} can automatically translate between the character sets for
9373 you. The character set @value{GDBN} uses we call the @dfn{host
9374 character set}; the one the inferior program uses we call the
9375 @dfn{target character set}.
9377 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9378 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9379 remote protocol (@pxref{Remote Debugging}) to debug a program
9380 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9381 then the host character set is Latin-1, and the target character set is
9382 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9383 target-charset EBCDIC-US}, then @value{GDBN} translates between
9384 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9385 character and string literals in expressions.
9387 @value{GDBN} has no way to automatically recognize which character set
9388 the inferior program uses; you must tell it, using the @code{set
9389 target-charset} command, described below.
9391 Here are the commands for controlling @value{GDBN}'s character set
9395 @item set target-charset @var{charset}
9396 @kindex set target-charset
9397 Set the current target character set to @var{charset}. To display the
9398 list of supported target character sets, type
9399 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9401 @item set host-charset @var{charset}
9402 @kindex set host-charset
9403 Set the current host character set to @var{charset}.
9405 By default, @value{GDBN} uses a host character set appropriate to the
9406 system it is running on; you can override that default using the
9407 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9408 automatically determine the appropriate host character set. In this
9409 case, @value{GDBN} uses @samp{UTF-8}.
9411 @value{GDBN} can only use certain character sets as its host character
9412 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9413 @value{GDBN} will list the host character sets it supports.
9415 @item set charset @var{charset}
9417 Set the current host and target character sets to @var{charset}. As
9418 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9419 @value{GDBN} will list the names of the character sets that can be used
9420 for both host and target.
9423 @kindex show charset
9424 Show the names of the current host and target character sets.
9426 @item show host-charset
9427 @kindex show host-charset
9428 Show the name of the current host character set.
9430 @item show target-charset
9431 @kindex show target-charset
9432 Show the name of the current target character set.
9434 @item set target-wide-charset @var{charset}
9435 @kindex set target-wide-charset
9436 Set the current target's wide character set to @var{charset}. This is
9437 the character set used by the target's @code{wchar_t} type. To
9438 display the list of supported wide character sets, type
9439 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9441 @item show target-wide-charset
9442 @kindex show target-wide-charset
9443 Show the name of the current target's wide character set.
9446 Here is an example of @value{GDBN}'s character set support in action.
9447 Assume that the following source code has been placed in the file
9448 @file{charset-test.c}:
9454 = @{72, 101, 108, 108, 111, 44, 32, 119,
9455 111, 114, 108, 100, 33, 10, 0@};
9456 char ibm1047_hello[]
9457 = @{200, 133, 147, 147, 150, 107, 64, 166,
9458 150, 153, 147, 132, 90, 37, 0@};
9462 printf ("Hello, world!\n");
9466 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9467 containing the string @samp{Hello, world!} followed by a newline,
9468 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9470 We compile the program, and invoke the debugger on it:
9473 $ gcc -g charset-test.c -o charset-test
9474 $ gdb -nw charset-test
9475 GNU gdb 2001-12-19-cvs
9476 Copyright 2001 Free Software Foundation, Inc.
9481 We can use the @code{show charset} command to see what character sets
9482 @value{GDBN} is currently using to interpret and display characters and
9486 (@value{GDBP}) show charset
9487 The current host and target character set is `ISO-8859-1'.
9491 For the sake of printing this manual, let's use @sc{ascii} as our
9492 initial character set:
9494 (@value{GDBP}) set charset ASCII
9495 (@value{GDBP}) show charset
9496 The current host and target character set is `ASCII'.
9500 Let's assume that @sc{ascii} is indeed the correct character set for our
9501 host system --- in other words, let's assume that if @value{GDBN} prints
9502 characters using the @sc{ascii} character set, our terminal will display
9503 them properly. Since our current target character set is also
9504 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9507 (@value{GDBP}) print ascii_hello
9508 $1 = 0x401698 "Hello, world!\n"
9509 (@value{GDBP}) print ascii_hello[0]
9514 @value{GDBN} uses the target character set for character and string
9515 literals you use in expressions:
9518 (@value{GDBP}) print '+'
9523 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9526 @value{GDBN} relies on the user to tell it which character set the
9527 target program uses. If we print @code{ibm1047_hello} while our target
9528 character set is still @sc{ascii}, we get jibberish:
9531 (@value{GDBP}) print ibm1047_hello
9532 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9533 (@value{GDBP}) print ibm1047_hello[0]
9538 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9539 @value{GDBN} tells us the character sets it supports:
9542 (@value{GDBP}) set target-charset
9543 ASCII EBCDIC-US IBM1047 ISO-8859-1
9544 (@value{GDBP}) set target-charset
9547 We can select @sc{ibm1047} as our target character set, and examine the
9548 program's strings again. Now the @sc{ascii} string is wrong, but
9549 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9550 target character set, @sc{ibm1047}, to the host character set,
9551 @sc{ascii}, and they display correctly:
9554 (@value{GDBP}) set target-charset IBM1047
9555 (@value{GDBP}) show charset
9556 The current host character set is `ASCII'.
9557 The current target character set is `IBM1047'.
9558 (@value{GDBP}) print ascii_hello
9559 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9560 (@value{GDBP}) print ascii_hello[0]
9562 (@value{GDBP}) print ibm1047_hello
9563 $8 = 0x4016a8 "Hello, world!\n"
9564 (@value{GDBP}) print ibm1047_hello[0]
9569 As above, @value{GDBN} uses the target character set for character and
9570 string literals you use in expressions:
9573 (@value{GDBP}) print '+'
9578 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9581 @node Caching Remote Data
9582 @section Caching Data of Remote Targets
9583 @cindex caching data of remote targets
9585 @value{GDBN} caches data exchanged between the debugger and a
9586 remote target (@pxref{Remote Debugging}). Such caching generally improves
9587 performance, because it reduces the overhead of the remote protocol by
9588 bundling memory reads and writes into large chunks. Unfortunately, simply
9589 caching everything would lead to incorrect results, since @value{GDBN}
9590 does not necessarily know anything about volatile values, memory-mapped I/O
9591 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9592 memory can be changed @emph{while} a gdb command is executing.
9593 Therefore, by default, @value{GDBN} only caches data
9594 known to be on the stack@footnote{In non-stop mode, it is moderately
9595 rare for a running thread to modify the stack of a stopped thread
9596 in a way that would interfere with a backtrace, and caching of
9597 stack reads provides a significant speed up of remote backtraces.}.
9598 Other regions of memory can be explicitly marked as
9599 cacheable; see @pxref{Memory Region Attributes}.
9602 @kindex set remotecache
9603 @item set remotecache on
9604 @itemx set remotecache off
9605 This option no longer does anything; it exists for compatibility
9608 @kindex show remotecache
9609 @item show remotecache
9610 Show the current state of the obsolete remotecache flag.
9612 @kindex set stack-cache
9613 @item set stack-cache on
9614 @itemx set stack-cache off
9615 Enable or disable caching of stack accesses. When @code{ON}, use
9616 caching. By default, this option is @code{ON}.
9618 @kindex show stack-cache
9619 @item show stack-cache
9620 Show the current state of data caching for memory accesses.
9623 @item info dcache @r{[}line@r{]}
9624 Print the information about the data cache performance. The
9625 information displayed includes the dcache width and depth, and for
9626 each cache line, its number, address, and how many times it was
9627 referenced. This command is useful for debugging the data cache
9630 If a line number is specified, the contents of that line will be
9633 @item set dcache size @var{size}
9635 @kindex set dcache size
9636 Set maximum number of entries in dcache (dcache depth above).
9638 @item set dcache line-size @var{line-size}
9639 @cindex dcache line-size
9640 @kindex set dcache line-size
9641 Set number of bytes each dcache entry caches (dcache width above).
9642 Must be a power of 2.
9644 @item show dcache size
9645 @kindex show dcache size
9646 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9648 @item show dcache line-size
9649 @kindex show dcache line-size
9650 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9654 @node Searching Memory
9655 @section Search Memory
9656 @cindex searching memory
9658 Memory can be searched for a particular sequence of bytes with the
9659 @code{find} command.
9663 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9664 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9665 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9666 etc. The search begins at address @var{start_addr} and continues for either
9667 @var{len} bytes or through to @var{end_addr} inclusive.
9670 @var{s} and @var{n} are optional parameters.
9671 They may be specified in either order, apart or together.
9674 @item @var{s}, search query size
9675 The size of each search query value.
9681 halfwords (two bytes)
9685 giant words (eight bytes)
9688 All values are interpreted in the current language.
9689 This means, for example, that if the current source language is C/C@t{++}
9690 then searching for the string ``hello'' includes the trailing '\0'.
9692 If the value size is not specified, it is taken from the
9693 value's type in the current language.
9694 This is useful when one wants to specify the search
9695 pattern as a mixture of types.
9696 Note that this means, for example, that in the case of C-like languages
9697 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9698 which is typically four bytes.
9700 @item @var{n}, maximum number of finds
9701 The maximum number of matches to print. The default is to print all finds.
9704 You can use strings as search values. Quote them with double-quotes
9706 The string value is copied into the search pattern byte by byte,
9707 regardless of the endianness of the target and the size specification.
9709 The address of each match found is printed as well as a count of the
9710 number of matches found.
9712 The address of the last value found is stored in convenience variable
9714 A count of the number of matches is stored in @samp{$numfound}.
9716 For example, if stopped at the @code{printf} in this function:
9722 static char hello[] = "hello-hello";
9723 static struct @{ char c; short s; int i; @}
9724 __attribute__ ((packed)) mixed
9725 = @{ 'c', 0x1234, 0x87654321 @};
9726 printf ("%s\n", hello);
9731 you get during debugging:
9734 (gdb) find &hello[0], +sizeof(hello), "hello"
9735 0x804956d <hello.1620+6>
9737 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9738 0x8049567 <hello.1620>
9739 0x804956d <hello.1620+6>
9741 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9742 0x8049567 <hello.1620>
9744 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9745 0x8049560 <mixed.1625>
9747 (gdb) print $numfound
9750 $2 = (void *) 0x8049560
9753 @node Optimized Code
9754 @chapter Debugging Optimized Code
9755 @cindex optimized code, debugging
9756 @cindex debugging optimized code
9758 Almost all compilers support optimization. With optimization
9759 disabled, the compiler generates assembly code that corresponds
9760 directly to your source code, in a simplistic way. As the compiler
9761 applies more powerful optimizations, the generated assembly code
9762 diverges from your original source code. With help from debugging
9763 information generated by the compiler, @value{GDBN} can map from
9764 the running program back to constructs from your original source.
9766 @value{GDBN} is more accurate with optimization disabled. If you
9767 can recompile without optimization, it is easier to follow the
9768 progress of your program during debugging. But, there are many cases
9769 where you may need to debug an optimized version.
9771 When you debug a program compiled with @samp{-g -O}, remember that the
9772 optimizer has rearranged your code; the debugger shows you what is
9773 really there. Do not be too surprised when the execution path does not
9774 exactly match your source file! An extreme example: if you define a
9775 variable, but never use it, @value{GDBN} never sees that
9776 variable---because the compiler optimizes it out of existence.
9778 Some things do not work as well with @samp{-g -O} as with just
9779 @samp{-g}, particularly on machines with instruction scheduling. If in
9780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9781 please report it to us as a bug (including a test case!).
9782 @xref{Variables}, for more information about debugging optimized code.
9785 * Inline Functions:: How @value{GDBN} presents inlining
9786 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9789 @node Inline Functions
9790 @section Inline Functions
9791 @cindex inline functions, debugging
9793 @dfn{Inlining} is an optimization that inserts a copy of the function
9794 body directly at each call site, instead of jumping to a shared
9795 routine. @value{GDBN} displays inlined functions just like
9796 non-inlined functions. They appear in backtraces. You can view their
9797 arguments and local variables, step into them with @code{step}, skip
9798 them with @code{next}, and escape from them with @code{finish}.
9799 You can check whether a function was inlined by using the
9800 @code{info frame} command.
9802 For @value{GDBN} to support inlined functions, the compiler must
9803 record information about inlining in the debug information ---
9804 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9805 other compilers do also. @value{GDBN} only supports inlined functions
9806 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9807 do not emit two required attributes (@samp{DW_AT_call_file} and
9808 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9809 function calls with earlier versions of @value{NGCC}. It instead
9810 displays the arguments and local variables of inlined functions as
9811 local variables in the caller.
9813 The body of an inlined function is directly included at its call site;
9814 unlike a non-inlined function, there are no instructions devoted to
9815 the call. @value{GDBN} still pretends that the call site and the
9816 start of the inlined function are different instructions. Stepping to
9817 the call site shows the call site, and then stepping again shows
9818 the first line of the inlined function, even though no additional
9819 instructions are executed.
9821 This makes source-level debugging much clearer; you can see both the
9822 context of the call and then the effect of the call. Only stepping by
9823 a single instruction using @code{stepi} or @code{nexti} does not do
9824 this; single instruction steps always show the inlined body.
9826 There are some ways that @value{GDBN} does not pretend that inlined
9827 function calls are the same as normal calls:
9831 You cannot set breakpoints on inlined functions. @value{GDBN}
9832 either reports that there is no symbol with that name, or else sets the
9833 breakpoint only on non-inlined copies of the function. This limitation
9834 will be removed in a future version of @value{GDBN}; until then,
9835 set a breakpoint by line number on the first line of the inlined
9839 Setting breakpoints at the call site of an inlined function may not
9840 work, because the call site does not contain any code. @value{GDBN}
9841 may incorrectly move the breakpoint to the next line of the enclosing
9842 function, after the call. This limitation will be removed in a future
9843 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9844 or inside the inlined function instead.
9847 @value{GDBN} cannot locate the return value of inlined calls after
9848 using the @code{finish} command. This is a limitation of compiler-generated
9849 debugging information; after @code{finish}, you can step to the next line
9850 and print a variable where your program stored the return value.
9854 @node Tail Call Frames
9855 @section Tail Call Frames
9856 @cindex tail call frames, debugging
9858 Function @code{B} can call function @code{C} in its very last statement. In
9859 unoptimized compilation the call of @code{C} is immediately followed by return
9860 instruction at the end of @code{B} code. Optimizing compiler may replace the
9861 call and return in function @code{B} into one jump to function @code{C}
9862 instead. Such use of a jump instruction is called @dfn{tail call}.
9864 During execution of function @code{C}, there will be no indication in the
9865 function call stack frames that it was tail-called from @code{B}. If function
9866 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9867 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9868 some cases @value{GDBN} can determine that @code{C} was tail-called from
9869 @code{B}, and it will then create fictitious call frame for that, with the
9870 return address set up as if @code{B} called @code{C} normally.
9872 This functionality is currently supported only by DWARF 2 debugging format and
9873 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9874 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9877 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9878 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9882 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9884 Stack level 1, frame at 0x7fffffffda30:
9885 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9886 tail call frame, caller of frame at 0x7fffffffda30
9887 source language c++.
9888 Arglist at unknown address.
9889 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9892 The detection of all the possible code path executions can find them ambiguous.
9893 There is no execution history stored (possible @ref{Reverse Execution} is never
9894 used for this purpose) and the last known caller could have reached the known
9895 callee by multiple different jump sequences. In such case @value{GDBN} still
9896 tries to show at least all the unambiguous top tail callers and all the
9897 unambiguous bottom tail calees, if any.
9900 @anchor{set debug entry-values}
9901 @item set debug entry-values
9902 @kindex set debug entry-values
9903 When set to on, enables printing of analysis messages for both frame argument
9904 values at function entry and tail calls. It will show all the possible valid
9905 tail calls code paths it has considered. It will also print the intersection
9906 of them with the final unambiguous (possibly partial or even empty) code path
9909 @item show debug entry-values
9910 @kindex show debug entry-values
9911 Show the current state of analysis messages printing for both frame argument
9912 values at function entry and tail calls.
9915 The analysis messages for tail calls can for example show why the virtual tail
9916 call frame for function @code{c} has not been recognized (due to the indirect
9917 reference by variable @code{x}):
9920 static void __attribute__((noinline, noclone)) c (void);
9921 void (*x) (void) = c;
9922 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9923 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9924 int main (void) @{ x (); return 0; @}
9926 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9927 DW_TAG_GNU_call_site 0x40039a in main
9929 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9932 #1 0x000000000040039a in main () at t.c:5
9935 Another possibility is an ambiguous virtual tail call frames resolution:
9939 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9940 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9941 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9942 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9943 static void __attribute__((noinline, noclone)) b (void)
9944 @{ if (i) c (); else e (); @}
9945 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9946 int main (void) @{ a (); return 0; @}
9948 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9949 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9950 tailcall: reduced: 0x4004d2(a) |
9953 #1 0x00000000004004d2 in a () at t.c:8
9954 #2 0x0000000000400395 in main () at t.c:9
9957 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9958 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9960 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9961 @ifset HAVE_MAKEINFO_CLICK
9963 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9964 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9966 @ifclear HAVE_MAKEINFO_CLICK
9968 @set CALLSEQ1B @value{CALLSEQ1A}
9969 @set CALLSEQ2B @value{CALLSEQ2A}
9972 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9973 The code can have possible execution paths @value{CALLSEQ1B} or
9974 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9976 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9977 has found. It then finds another possible calling sequcen - that one is
9978 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9979 printed as the @code{reduced:} calling sequence. That one could have many
9980 futher @code{compare:} and @code{reduced:} statements as long as there remain
9981 any non-ambiguous sequence entries.
9983 For the frame of function @code{b} in both cases there are different possible
9984 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9985 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9986 therefore this one is displayed to the user while the ambiguous frames are
9989 There can be also reasons why printing of frame argument values at function
9994 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9995 static void __attribute__((noinline, noclone)) a (int i);
9996 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9997 static void __attribute__((noinline, noclone)) a (int i)
9998 @{ if (i) b (i - 1); else c (0); @}
9999 int main (void) @{ a (5); return 0; @}
10002 #0 c (i=i@@entry=0) at t.c:2
10003 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10004 function "a" at 0x400420 can call itself via tail calls
10005 i=<optimized out>) at t.c:6
10006 #2 0x000000000040036e in main () at t.c:7
10009 @value{GDBN} cannot find out from the inferior state if and how many times did
10010 function @code{a} call itself (via function @code{b}) as these calls would be
10011 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10012 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10013 prints @code{<optimized out>} instead.
10016 @chapter C Preprocessor Macros
10018 Some languages, such as C and C@t{++}, provide a way to define and invoke
10019 ``preprocessor macros'' which expand into strings of tokens.
10020 @value{GDBN} can evaluate expressions containing macro invocations, show
10021 the result of macro expansion, and show a macro's definition, including
10022 where it was defined.
10024 You may need to compile your program specially to provide @value{GDBN}
10025 with information about preprocessor macros. Most compilers do not
10026 include macros in their debugging information, even when you compile
10027 with the @option{-g} flag. @xref{Compilation}.
10029 A program may define a macro at one point, remove that definition later,
10030 and then provide a different definition after that. Thus, at different
10031 points in the program, a macro may have different definitions, or have
10032 no definition at all. If there is a current stack frame, @value{GDBN}
10033 uses the macros in scope at that frame's source code line. Otherwise,
10034 @value{GDBN} uses the macros in scope at the current listing location;
10037 Whenever @value{GDBN} evaluates an expression, it always expands any
10038 macro invocations present in the expression. @value{GDBN} also provides
10039 the following commands for working with macros explicitly.
10043 @kindex macro expand
10044 @cindex macro expansion, showing the results of preprocessor
10045 @cindex preprocessor macro expansion, showing the results of
10046 @cindex expanding preprocessor macros
10047 @item macro expand @var{expression}
10048 @itemx macro exp @var{expression}
10049 Show the results of expanding all preprocessor macro invocations in
10050 @var{expression}. Since @value{GDBN} simply expands macros, but does
10051 not parse the result, @var{expression} need not be a valid expression;
10052 it can be any string of tokens.
10055 @item macro expand-once @var{expression}
10056 @itemx macro exp1 @var{expression}
10057 @cindex expand macro once
10058 @i{(This command is not yet implemented.)} Show the results of
10059 expanding those preprocessor macro invocations that appear explicitly in
10060 @var{expression}. Macro invocations appearing in that expansion are
10061 left unchanged. This command allows you to see the effect of a
10062 particular macro more clearly, without being confused by further
10063 expansions. Since @value{GDBN} simply expands macros, but does not
10064 parse the result, @var{expression} need not be a valid expression; it
10065 can be any string of tokens.
10068 @cindex macro definition, showing
10069 @cindex definition of a macro, showing
10070 @cindex macros, from debug info
10071 @item info macro [-a|-all] [--] @var{macro}
10072 Show the current definition or all definitions of the named @var{macro},
10073 and describe the source location or compiler command-line where that
10074 definition was established. The optional double dash is to signify the end of
10075 argument processing and the beginning of @var{macro} for non C-like macros where
10076 the macro may begin with a hyphen.
10078 @kindex info macros
10079 @item info macros @var{linespec}
10080 Show all macro definitions that are in effect at the location specified
10081 by @var{linespec}, and describe the source location or compiler
10082 command-line where those definitions were established.
10084 @kindex macro define
10085 @cindex user-defined macros
10086 @cindex defining macros interactively
10087 @cindex macros, user-defined
10088 @item macro define @var{macro} @var{replacement-list}
10089 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10090 Introduce a definition for a preprocessor macro named @var{macro},
10091 invocations of which are replaced by the tokens given in
10092 @var{replacement-list}. The first form of this command defines an
10093 ``object-like'' macro, which takes no arguments; the second form
10094 defines a ``function-like'' macro, which takes the arguments given in
10097 A definition introduced by this command is in scope in every
10098 expression evaluated in @value{GDBN}, until it is removed with the
10099 @code{macro undef} command, described below. The definition overrides
10100 all definitions for @var{macro} present in the program being debugged,
10101 as well as any previous user-supplied definition.
10103 @kindex macro undef
10104 @item macro undef @var{macro}
10105 Remove any user-supplied definition for the macro named @var{macro}.
10106 This command only affects definitions provided with the @code{macro
10107 define} command, described above; it cannot remove definitions present
10108 in the program being debugged.
10112 List all the macros defined using the @code{macro define} command.
10115 @cindex macros, example of debugging with
10116 Here is a transcript showing the above commands in action. First, we
10117 show our source files:
10122 #include "sample.h"
10125 #define ADD(x) (M + x)
10130 printf ("Hello, world!\n");
10132 printf ("We're so creative.\n");
10134 printf ("Goodbye, world!\n");
10141 Now, we compile the program using the @sc{gnu} C compiler,
10142 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10143 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10144 and @option{-gdwarf-4}; we recommend always choosing the most recent
10145 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10146 includes information about preprocessor macros in the debugging
10150 $ gcc -gdwarf-2 -g3 sample.c -o sample
10154 Now, we start @value{GDBN} on our sample program:
10158 GNU gdb 2002-05-06-cvs
10159 Copyright 2002 Free Software Foundation, Inc.
10160 GDB is free software, @dots{}
10164 We can expand macros and examine their definitions, even when the
10165 program is not running. @value{GDBN} uses the current listing position
10166 to decide which macro definitions are in scope:
10169 (@value{GDBP}) list main
10172 5 #define ADD(x) (M + x)
10177 10 printf ("Hello, world!\n");
10179 12 printf ("We're so creative.\n");
10180 (@value{GDBP}) info macro ADD
10181 Defined at /home/jimb/gdb/macros/play/sample.c:5
10182 #define ADD(x) (M + x)
10183 (@value{GDBP}) info macro Q
10184 Defined at /home/jimb/gdb/macros/play/sample.h:1
10185 included at /home/jimb/gdb/macros/play/sample.c:2
10187 (@value{GDBP}) macro expand ADD(1)
10188 expands to: (42 + 1)
10189 (@value{GDBP}) macro expand-once ADD(1)
10190 expands to: once (M + 1)
10194 In the example above, note that @code{macro expand-once} expands only
10195 the macro invocation explicit in the original text --- the invocation of
10196 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10197 which was introduced by @code{ADD}.
10199 Once the program is running, @value{GDBN} uses the macro definitions in
10200 force at the source line of the current stack frame:
10203 (@value{GDBP}) break main
10204 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10206 Starting program: /home/jimb/gdb/macros/play/sample
10208 Breakpoint 1, main () at sample.c:10
10209 10 printf ("Hello, world!\n");
10213 At line 10, the definition of the macro @code{N} at line 9 is in force:
10216 (@value{GDBP}) info macro N
10217 Defined at /home/jimb/gdb/macros/play/sample.c:9
10219 (@value{GDBP}) macro expand N Q M
10220 expands to: 28 < 42
10221 (@value{GDBP}) print N Q M
10226 As we step over directives that remove @code{N}'s definition, and then
10227 give it a new definition, @value{GDBN} finds the definition (or lack
10228 thereof) in force at each point:
10231 (@value{GDBP}) next
10233 12 printf ("We're so creative.\n");
10234 (@value{GDBP}) info macro N
10235 The symbol `N' has no definition as a C/C++ preprocessor macro
10236 at /home/jimb/gdb/macros/play/sample.c:12
10237 (@value{GDBP}) next
10239 14 printf ("Goodbye, world!\n");
10240 (@value{GDBP}) info macro N
10241 Defined at /home/jimb/gdb/macros/play/sample.c:13
10243 (@value{GDBP}) macro expand N Q M
10244 expands to: 1729 < 42
10245 (@value{GDBP}) print N Q M
10250 In addition to source files, macros can be defined on the compilation command
10251 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10252 such a way, @value{GDBN} displays the location of their definition as line zero
10253 of the source file submitted to the compiler.
10256 (@value{GDBP}) info macro __STDC__
10257 Defined at /home/jimb/gdb/macros/play/sample.c:0
10264 @chapter Tracepoints
10265 @c This chapter is based on the documentation written by Michael
10266 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10268 @cindex tracepoints
10269 In some applications, it is not feasible for the debugger to interrupt
10270 the program's execution long enough for the developer to learn
10271 anything helpful about its behavior. If the program's correctness
10272 depends on its real-time behavior, delays introduced by a debugger
10273 might cause the program to change its behavior drastically, or perhaps
10274 fail, even when the code itself is correct. It is useful to be able
10275 to observe the program's behavior without interrupting it.
10277 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10278 specify locations in the program, called @dfn{tracepoints}, and
10279 arbitrary expressions to evaluate when those tracepoints are reached.
10280 Later, using the @code{tfind} command, you can examine the values
10281 those expressions had when the program hit the tracepoints. The
10282 expressions may also denote objects in memory---structures or arrays,
10283 for example---whose values @value{GDBN} should record; while visiting
10284 a particular tracepoint, you may inspect those objects as if they were
10285 in memory at that moment. However, because @value{GDBN} records these
10286 values without interacting with you, it can do so quickly and
10287 unobtrusively, hopefully not disturbing the program's behavior.
10289 The tracepoint facility is currently available only for remote
10290 targets. @xref{Targets}. In addition, your remote target must know
10291 how to collect trace data. This functionality is implemented in the
10292 remote stub; however, none of the stubs distributed with @value{GDBN}
10293 support tracepoints as of this writing. The format of the remote
10294 packets used to implement tracepoints are described in @ref{Tracepoint
10297 It is also possible to get trace data from a file, in a manner reminiscent
10298 of corefiles; you specify the filename, and use @code{tfind} to search
10299 through the file. @xref{Trace Files}, for more details.
10301 This chapter describes the tracepoint commands and features.
10304 * Set Tracepoints::
10305 * Analyze Collected Data::
10306 * Tracepoint Variables::
10310 @node Set Tracepoints
10311 @section Commands to Set Tracepoints
10313 Before running such a @dfn{trace experiment}, an arbitrary number of
10314 tracepoints can be set. A tracepoint is actually a special type of
10315 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10316 standard breakpoint commands. For instance, as with breakpoints,
10317 tracepoint numbers are successive integers starting from one, and many
10318 of the commands associated with tracepoints take the tracepoint number
10319 as their argument, to identify which tracepoint to work on.
10321 For each tracepoint, you can specify, in advance, some arbitrary set
10322 of data that you want the target to collect in the trace buffer when
10323 it hits that tracepoint. The collected data can include registers,
10324 local variables, or global data. Later, you can use @value{GDBN}
10325 commands to examine the values these data had at the time the
10326 tracepoint was hit.
10328 Tracepoints do not support every breakpoint feature. Ignore counts on
10329 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10330 commands when they are hit. Tracepoints may not be thread-specific
10333 @cindex fast tracepoints
10334 Some targets may support @dfn{fast tracepoints}, which are inserted in
10335 a different way (such as with a jump instead of a trap), that is
10336 faster but possibly restricted in where they may be installed.
10338 @cindex static tracepoints
10339 @cindex markers, static tracepoints
10340 @cindex probing markers, static tracepoints
10341 Regular and fast tracepoints are dynamic tracing facilities, meaning
10342 that they can be used to insert tracepoints at (almost) any location
10343 in the target. Some targets may also support controlling @dfn{static
10344 tracepoints} from @value{GDBN}. With static tracing, a set of
10345 instrumentation points, also known as @dfn{markers}, are embedded in
10346 the target program, and can be activated or deactivated by name or
10347 address. These are usually placed at locations which facilitate
10348 investigating what the target is actually doing. @value{GDBN}'s
10349 support for static tracing includes being able to list instrumentation
10350 points, and attach them with @value{GDBN} defined high level
10351 tracepoints that expose the whole range of convenience of
10352 @value{GDBN}'s tracepoints support. Namely, support for collecting
10353 registers values and values of global or local (to the instrumentation
10354 point) variables; tracepoint conditions and trace state variables.
10355 The act of installing a @value{GDBN} static tracepoint on an
10356 instrumentation point, or marker, is referred to as @dfn{probing} a
10357 static tracepoint marker.
10359 @code{gdbserver} supports tracepoints on some target systems.
10360 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10362 This section describes commands to set tracepoints and associated
10363 conditions and actions.
10366 * Create and Delete Tracepoints::
10367 * Enable and Disable Tracepoints::
10368 * Tracepoint Passcounts::
10369 * Tracepoint Conditions::
10370 * Trace State Variables::
10371 * Tracepoint Actions::
10372 * Listing Tracepoints::
10373 * Listing Static Tracepoint Markers::
10374 * Starting and Stopping Trace Experiments::
10375 * Tracepoint Restrictions::
10378 @node Create and Delete Tracepoints
10379 @subsection Create and Delete Tracepoints
10382 @cindex set tracepoint
10384 @item trace @var{location}
10385 The @code{trace} command is very similar to the @code{break} command.
10386 Its argument @var{location} can be a source line, a function name, or
10387 an address in the target program. @xref{Specify Location}. The
10388 @code{trace} command defines a tracepoint, which is a point in the
10389 target program where the debugger will briefly stop, collect some
10390 data, and then allow the program to continue. Setting a tracepoint or
10391 changing its actions takes effect immediately if the remote stub
10392 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10394 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10395 these changes don't take effect until the next @code{tstart}
10396 command, and once a trace experiment is running, further changes will
10397 not have any effect until the next trace experiment starts. In addition,
10398 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10399 address is not yet resolved. (This is similar to pending breakpoints.)
10400 Pending tracepoints are not downloaded to the target and not installed
10401 until they are resolved. The resolution of pending tracepoints requires
10402 @value{GDBN} support---when debugging with the remote target, and
10403 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10404 tracing}), pending tracepoints can not be resolved (and downloaded to
10405 the remote stub) while @value{GDBN} is disconnected.
10407 Here are some examples of using the @code{trace} command:
10410 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10412 (@value{GDBP}) @b{trace +2} // 2 lines forward
10414 (@value{GDBP}) @b{trace my_function} // first source line of function
10416 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10418 (@value{GDBP}) @b{trace *0x2117c4} // an address
10422 You can abbreviate @code{trace} as @code{tr}.
10424 @item trace @var{location} if @var{cond}
10425 Set a tracepoint with condition @var{cond}; evaluate the expression
10426 @var{cond} each time the tracepoint is reached, and collect data only
10427 if the value is nonzero---that is, if @var{cond} evaluates as true.
10428 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10429 information on tracepoint conditions.
10431 @item ftrace @var{location} [ if @var{cond} ]
10432 @cindex set fast tracepoint
10433 @cindex fast tracepoints, setting
10435 The @code{ftrace} command sets a fast tracepoint. For targets that
10436 support them, fast tracepoints will use a more efficient but possibly
10437 less general technique to trigger data collection, such as a jump
10438 instruction instead of a trap, or some sort of hardware support. It
10439 may not be possible to create a fast tracepoint at the desired
10440 location, in which case the command will exit with an explanatory
10443 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10446 On 32-bit x86-architecture systems, fast tracepoints normally need to
10447 be placed at an instruction that is 5 bytes or longer, but can be
10448 placed at 4-byte instructions if the low 64K of memory of the target
10449 program is available to install trampolines. Some Unix-type systems,
10450 such as @sc{gnu}/Linux, exclude low addresses from the program's
10451 address space; but for instance with the Linux kernel it is possible
10452 to let @value{GDBN} use this area by doing a @command{sysctl} command
10453 to set the @code{mmap_min_addr} kernel parameter, as in
10456 sudo sysctl -w vm.mmap_min_addr=32768
10460 which sets the low address to 32K, which leaves plenty of room for
10461 trampolines. The minimum address should be set to a page boundary.
10463 @item strace @var{location} [ if @var{cond} ]
10464 @cindex set static tracepoint
10465 @cindex static tracepoints, setting
10466 @cindex probe static tracepoint marker
10468 The @code{strace} command sets a static tracepoint. For targets that
10469 support it, setting a static tracepoint probes a static
10470 instrumentation point, or marker, found at @var{location}. It may not
10471 be possible to set a static tracepoint at the desired location, in
10472 which case the command will exit with an explanatory message.
10474 @value{GDBN} handles arguments to @code{strace} exactly as for
10475 @code{trace}, with the addition that the user can also specify
10476 @code{-m @var{marker}} as @var{location}. This probes the marker
10477 identified by the @var{marker} string identifier. This identifier
10478 depends on the static tracepoint backend library your program is
10479 using. You can find all the marker identifiers in the @samp{ID} field
10480 of the @code{info static-tracepoint-markers} command output.
10481 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10482 Markers}. For example, in the following small program using the UST
10488 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10493 the marker id is composed of joining the first two arguments to the
10494 @code{trace_mark} call with a slash, which translates to:
10497 (@value{GDBP}) info static-tracepoint-markers
10498 Cnt Enb ID Address What
10499 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10505 so you may probe the marker above with:
10508 (@value{GDBP}) strace -m ust/bar33
10511 Static tracepoints accept an extra collect action --- @code{collect
10512 $_sdata}. This collects arbitrary user data passed in the probe point
10513 call to the tracing library. In the UST example above, you'll see
10514 that the third argument to @code{trace_mark} is a printf-like format
10515 string. The user data is then the result of running that formating
10516 string against the following arguments. Note that @code{info
10517 static-tracepoint-markers} command output lists that format string in
10518 the @samp{Data:} field.
10520 You can inspect this data when analyzing the trace buffer, by printing
10521 the $_sdata variable like any other variable available to
10522 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10525 @cindex last tracepoint number
10526 @cindex recent tracepoint number
10527 @cindex tracepoint number
10528 The convenience variable @code{$tpnum} records the tracepoint number
10529 of the most recently set tracepoint.
10531 @kindex delete tracepoint
10532 @cindex tracepoint deletion
10533 @item delete tracepoint @r{[}@var{num}@r{]}
10534 Permanently delete one or more tracepoints. With no argument, the
10535 default is to delete all tracepoints. Note that the regular
10536 @code{delete} command can remove tracepoints also.
10541 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10543 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10547 You can abbreviate this command as @code{del tr}.
10550 @node Enable and Disable Tracepoints
10551 @subsection Enable and Disable Tracepoints
10553 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10556 @kindex disable tracepoint
10557 @item disable tracepoint @r{[}@var{num}@r{]}
10558 Disable tracepoint @var{num}, or all tracepoints if no argument
10559 @var{num} is given. A disabled tracepoint will have no effect during
10560 a trace experiment, but it is not forgotten. You can re-enable
10561 a disabled tracepoint using the @code{enable tracepoint} command.
10562 If the command is issued during a trace experiment and the debug target
10563 has support for disabling tracepoints during a trace experiment, then the
10564 change will be effective immediately. Otherwise, it will be applied to the
10565 next trace experiment.
10567 @kindex enable tracepoint
10568 @item enable tracepoint @r{[}@var{num}@r{]}
10569 Enable tracepoint @var{num}, or all tracepoints. If this command is
10570 issued during a trace experiment and the debug target supports enabling
10571 tracepoints during a trace experiment, then the enabled tracepoints will
10572 become effective immediately. Otherwise, they will become effective the
10573 next time a trace experiment is run.
10576 @node Tracepoint Passcounts
10577 @subsection Tracepoint Passcounts
10581 @cindex tracepoint pass count
10582 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10583 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10584 automatically stop a trace experiment. If a tracepoint's passcount is
10585 @var{n}, then the trace experiment will be automatically stopped on
10586 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10587 @var{num} is not specified, the @code{passcount} command sets the
10588 passcount of the most recently defined tracepoint. If no passcount is
10589 given, the trace experiment will run until stopped explicitly by the
10595 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10596 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10598 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10599 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10600 (@value{GDBP}) @b{trace foo}
10601 (@value{GDBP}) @b{pass 3}
10602 (@value{GDBP}) @b{trace bar}
10603 (@value{GDBP}) @b{pass 2}
10604 (@value{GDBP}) @b{trace baz}
10605 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10606 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10607 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10608 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10612 @node Tracepoint Conditions
10613 @subsection Tracepoint Conditions
10614 @cindex conditional tracepoints
10615 @cindex tracepoint conditions
10617 The simplest sort of tracepoint collects data every time your program
10618 reaches a specified place. You can also specify a @dfn{condition} for
10619 a tracepoint. A condition is just a Boolean expression in your
10620 programming language (@pxref{Expressions, ,Expressions}). A
10621 tracepoint with a condition evaluates the expression each time your
10622 program reaches it, and data collection happens only if the condition
10625 Tracepoint conditions can be specified when a tracepoint is set, by
10626 using @samp{if} in the arguments to the @code{trace} command.
10627 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10628 also be set or changed at any time with the @code{condition} command,
10629 just as with breakpoints.
10631 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10632 the conditional expression itself. Instead, @value{GDBN} encodes the
10633 expression into an agent expression (@pxref{Agent Expressions})
10634 suitable for execution on the target, independently of @value{GDBN}.
10635 Global variables become raw memory locations, locals become stack
10636 accesses, and so forth.
10638 For instance, suppose you have a function that is usually called
10639 frequently, but should not be called after an error has occurred. You
10640 could use the following tracepoint command to collect data about calls
10641 of that function that happen while the error code is propagating
10642 through the program; an unconditional tracepoint could end up
10643 collecting thousands of useless trace frames that you would have to
10647 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10650 @node Trace State Variables
10651 @subsection Trace State Variables
10652 @cindex trace state variables
10654 A @dfn{trace state variable} is a special type of variable that is
10655 created and managed by target-side code. The syntax is the same as
10656 that for GDB's convenience variables (a string prefixed with ``$''),
10657 but they are stored on the target. They must be created explicitly,
10658 using a @code{tvariable} command. They are always 64-bit signed
10661 Trace state variables are remembered by @value{GDBN}, and downloaded
10662 to the target along with tracepoint information when the trace
10663 experiment starts. There are no intrinsic limits on the number of
10664 trace state variables, beyond memory limitations of the target.
10666 @cindex convenience variables, and trace state variables
10667 Although trace state variables are managed by the target, you can use
10668 them in print commands and expressions as if they were convenience
10669 variables; @value{GDBN} will get the current value from the target
10670 while the trace experiment is running. Trace state variables share
10671 the same namespace as other ``$'' variables, which means that you
10672 cannot have trace state variables with names like @code{$23} or
10673 @code{$pc}, nor can you have a trace state variable and a convenience
10674 variable with the same name.
10678 @item tvariable $@var{name} [ = @var{expression} ]
10680 The @code{tvariable} command creates a new trace state variable named
10681 @code{$@var{name}}, and optionally gives it an initial value of
10682 @var{expression}. @var{expression} is evaluated when this command is
10683 entered; the result will be converted to an integer if possible,
10684 otherwise @value{GDBN} will report an error. A subsequent
10685 @code{tvariable} command specifying the same name does not create a
10686 variable, but instead assigns the supplied initial value to the
10687 existing variable of that name, overwriting any previous initial
10688 value. The default initial value is 0.
10690 @item info tvariables
10691 @kindex info tvariables
10692 List all the trace state variables along with their initial values.
10693 Their current values may also be displayed, if the trace experiment is
10696 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10697 @kindex delete tvariable
10698 Delete the given trace state variables, or all of them if no arguments
10703 @node Tracepoint Actions
10704 @subsection Tracepoint Action Lists
10708 @cindex tracepoint actions
10709 @item actions @r{[}@var{num}@r{]}
10710 This command will prompt for a list of actions to be taken when the
10711 tracepoint is hit. If the tracepoint number @var{num} is not
10712 specified, this command sets the actions for the one that was most
10713 recently defined (so that you can define a tracepoint and then say
10714 @code{actions} without bothering about its number). You specify the
10715 actions themselves on the following lines, one action at a time, and
10716 terminate the actions list with a line containing just @code{end}. So
10717 far, the only defined actions are @code{collect}, @code{teval}, and
10718 @code{while-stepping}.
10720 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10721 Commands, ,Breakpoint Command Lists}), except that only the defined
10722 actions are allowed; any other @value{GDBN} command is rejected.
10724 @cindex remove actions from a tracepoint
10725 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10726 and follow it immediately with @samp{end}.
10729 (@value{GDBP}) @b{collect @var{data}} // collect some data
10731 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10733 (@value{GDBP}) @b{end} // signals the end of actions.
10736 In the following example, the action list begins with @code{collect}
10737 commands indicating the things to be collected when the tracepoint is
10738 hit. Then, in order to single-step and collect additional data
10739 following the tracepoint, a @code{while-stepping} command is used,
10740 followed by the list of things to be collected after each step in a
10741 sequence of single steps. The @code{while-stepping} command is
10742 terminated by its own separate @code{end} command. Lastly, the action
10743 list is terminated by an @code{end} command.
10746 (@value{GDBP}) @b{trace foo}
10747 (@value{GDBP}) @b{actions}
10748 Enter actions for tracepoint 1, one per line:
10751 > while-stepping 12
10752 > collect $pc, arr[i]
10757 @kindex collect @r{(tracepoints)}
10758 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10759 Collect values of the given expressions when the tracepoint is hit.
10760 This command accepts a comma-separated list of any valid expressions.
10761 In addition to global, static, or local variables, the following
10762 special arguments are supported:
10766 Collect all registers.
10769 Collect all function arguments.
10772 Collect all local variables.
10775 Collect the return address. This is helpful if you want to see more
10779 @vindex $_sdata@r{, collect}
10780 Collect static tracepoint marker specific data. Only available for
10781 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10782 Lists}. On the UST static tracepoints library backend, an
10783 instrumentation point resembles a @code{printf} function call. The
10784 tracing library is able to collect user specified data formatted to a
10785 character string using the format provided by the programmer that
10786 instrumented the program. Other backends have similar mechanisms.
10787 Here's an example of a UST marker call:
10790 const char master_name[] = "$your_name";
10791 trace_mark(channel1, marker1, "hello %s", master_name)
10794 In this case, collecting @code{$_sdata} collects the string
10795 @samp{hello $yourname}. When analyzing the trace buffer, you can
10796 inspect @samp{$_sdata} like any other variable available to
10800 You can give several consecutive @code{collect} commands, each one
10801 with a single argument, or one @code{collect} command with several
10802 arguments separated by commas; the effect is the same.
10804 The optional @var{mods} changes the usual handling of the arguments.
10805 @code{s} requests that pointers to chars be handled as strings, in
10806 particular collecting the contents of the memory being pointed at, up
10807 to the first zero. The upper bound is by default the value of the
10808 @code{print elements} variable; if @code{s} is followed by a decimal
10809 number, that is the upper bound instead. So for instance
10810 @samp{collect/s25 mystr} collects as many as 25 characters at
10813 The command @code{info scope} (@pxref{Symbols, info scope}) is
10814 particularly useful for figuring out what data to collect.
10816 @kindex teval @r{(tracepoints)}
10817 @item teval @var{expr1}, @var{expr2}, @dots{}
10818 Evaluate the given expressions when the tracepoint is hit. This
10819 command accepts a comma-separated list of expressions. The results
10820 are discarded, so this is mainly useful for assigning values to trace
10821 state variables (@pxref{Trace State Variables}) without adding those
10822 values to the trace buffer, as would be the case if the @code{collect}
10825 @kindex while-stepping @r{(tracepoints)}
10826 @item while-stepping @var{n}
10827 Perform @var{n} single-step instruction traces after the tracepoint,
10828 collecting new data after each step. The @code{while-stepping}
10829 command is followed by the list of what to collect while stepping
10830 (followed by its own @code{end} command):
10833 > while-stepping 12
10834 > collect $regs, myglobal
10840 Note that @code{$pc} is not automatically collected by
10841 @code{while-stepping}; you need to explicitly collect that register if
10842 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10845 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10846 @kindex set default-collect
10847 @cindex default collection action
10848 This variable is a list of expressions to collect at each tracepoint
10849 hit. It is effectively an additional @code{collect} action prepended
10850 to every tracepoint action list. The expressions are parsed
10851 individually for each tracepoint, so for instance a variable named
10852 @code{xyz} may be interpreted as a global for one tracepoint, and a
10853 local for another, as appropriate to the tracepoint's location.
10855 @item show default-collect
10856 @kindex show default-collect
10857 Show the list of expressions that are collected by default at each
10862 @node Listing Tracepoints
10863 @subsection Listing Tracepoints
10866 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10867 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10868 @cindex information about tracepoints
10869 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10870 Display information about the tracepoint @var{num}. If you don't
10871 specify a tracepoint number, displays information about all the
10872 tracepoints defined so far. The format is similar to that used for
10873 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10874 command, simply restricting itself to tracepoints.
10876 A tracepoint's listing may include additional information specific to
10881 its passcount as given by the @code{passcount @var{n}} command
10885 (@value{GDBP}) @b{info trace}
10886 Num Type Disp Enb Address What
10887 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10889 collect globfoo, $regs
10898 This command can be abbreviated @code{info tp}.
10901 @node Listing Static Tracepoint Markers
10902 @subsection Listing Static Tracepoint Markers
10905 @kindex info static-tracepoint-markers
10906 @cindex information about static tracepoint markers
10907 @item info static-tracepoint-markers
10908 Display information about all static tracepoint markers defined in the
10911 For each marker, the following columns are printed:
10915 An incrementing counter, output to help readability. This is not a
10918 The marker ID, as reported by the target.
10919 @item Enabled or Disabled
10920 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10921 that are not enabled.
10923 Where the marker is in your program, as a memory address.
10925 Where the marker is in the source for your program, as a file and line
10926 number. If the debug information included in the program does not
10927 allow @value{GDBN} to locate the source of the marker, this column
10928 will be left blank.
10932 In addition, the following information may be printed for each marker:
10936 User data passed to the tracing library by the marker call. In the
10937 UST backend, this is the format string passed as argument to the
10939 @item Static tracepoints probing the marker
10940 The list of static tracepoints attached to the marker.
10944 (@value{GDBP}) info static-tracepoint-markers
10945 Cnt ID Enb Address What
10946 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10947 Data: number1 %d number2 %d
10948 Probed by static tracepoints: #2
10949 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10955 @node Starting and Stopping Trace Experiments
10956 @subsection Starting and Stopping Trace Experiments
10959 @kindex tstart [ @var{notes} ]
10960 @cindex start a new trace experiment
10961 @cindex collected data discarded
10963 This command starts the trace experiment, and begins collecting data.
10964 It has the side effect of discarding all the data collected in the
10965 trace buffer during the previous trace experiment. If any arguments
10966 are supplied, they are taken as a note and stored with the trace
10967 experiment's state. The notes may be arbitrary text, and are
10968 especially useful with disconnected tracing in a multi-user context;
10969 the notes can explain what the trace is doing, supply user contact
10970 information, and so forth.
10972 @kindex tstop [ @var{notes} ]
10973 @cindex stop a running trace experiment
10975 This command stops the trace experiment. If any arguments are
10976 supplied, they are recorded with the experiment as a note. This is
10977 useful if you are stopping a trace started by someone else, for
10978 instance if the trace is interfering with the system's behavior and
10979 needs to be stopped quickly.
10981 @strong{Note}: a trace experiment and data collection may stop
10982 automatically if any tracepoint's passcount is reached
10983 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10986 @cindex status of trace data collection
10987 @cindex trace experiment, status of
10989 This command displays the status of the current trace data
10993 Here is an example of the commands we described so far:
10996 (@value{GDBP}) @b{trace gdb_c_test}
10997 (@value{GDBP}) @b{actions}
10998 Enter actions for tracepoint #1, one per line.
10999 > collect $regs,$locals,$args
11000 > while-stepping 11
11004 (@value{GDBP}) @b{tstart}
11005 [time passes @dots{}]
11006 (@value{GDBP}) @b{tstop}
11009 @anchor{disconnected tracing}
11010 @cindex disconnected tracing
11011 You can choose to continue running the trace experiment even if
11012 @value{GDBN} disconnects from the target, voluntarily or
11013 involuntarily. For commands such as @code{detach}, the debugger will
11014 ask what you want to do with the trace. But for unexpected
11015 terminations (@value{GDBN} crash, network outage), it would be
11016 unfortunate to lose hard-won trace data, so the variable
11017 @code{disconnected-tracing} lets you decide whether the trace should
11018 continue running without @value{GDBN}.
11021 @item set disconnected-tracing on
11022 @itemx set disconnected-tracing off
11023 @kindex set disconnected-tracing
11024 Choose whether a tracing run should continue to run if @value{GDBN}
11025 has disconnected from the target. Note that @code{detach} or
11026 @code{quit} will ask you directly what to do about a running trace no
11027 matter what this variable's setting, so the variable is mainly useful
11028 for handling unexpected situations, such as loss of the network.
11030 @item show disconnected-tracing
11031 @kindex show disconnected-tracing
11032 Show the current choice for disconnected tracing.
11036 When you reconnect to the target, the trace experiment may or may not
11037 still be running; it might have filled the trace buffer in the
11038 meantime, or stopped for one of the other reasons. If it is running,
11039 it will continue after reconnection.
11041 Upon reconnection, the target will upload information about the
11042 tracepoints in effect. @value{GDBN} will then compare that
11043 information to the set of tracepoints currently defined, and attempt
11044 to match them up, allowing for the possibility that the numbers may
11045 have changed due to creation and deletion in the meantime. If one of
11046 the target's tracepoints does not match any in @value{GDBN}, the
11047 debugger will create a new tracepoint, so that you have a number with
11048 which to specify that tracepoint. This matching-up process is
11049 necessarily heuristic, and it may result in useless tracepoints being
11050 created; you may simply delete them if they are of no use.
11052 @cindex circular trace buffer
11053 If your target agent supports a @dfn{circular trace buffer}, then you
11054 can run a trace experiment indefinitely without filling the trace
11055 buffer; when space runs out, the agent deletes already-collected trace
11056 frames, oldest first, until there is enough room to continue
11057 collecting. This is especially useful if your tracepoints are being
11058 hit too often, and your trace gets terminated prematurely because the
11059 buffer is full. To ask for a circular trace buffer, simply set
11060 @samp{circular-trace-buffer} to on. You can set this at any time,
11061 including during tracing; if the agent can do it, it will change
11062 buffer handling on the fly, otherwise it will not take effect until
11066 @item set circular-trace-buffer on
11067 @itemx set circular-trace-buffer off
11068 @kindex set circular-trace-buffer
11069 Choose whether a tracing run should use a linear or circular buffer
11070 for trace data. A linear buffer will not lose any trace data, but may
11071 fill up prematurely, while a circular buffer will discard old trace
11072 data, but it will have always room for the latest tracepoint hits.
11074 @item show circular-trace-buffer
11075 @kindex show circular-trace-buffer
11076 Show the current choice for the trace buffer. Note that this may not
11077 match the agent's current buffer handling, nor is it guaranteed to
11078 match the setting that might have been in effect during a past run,
11079 for instance if you are looking at frames from a trace file.
11084 @item set trace-user @var{text}
11085 @kindex set trace-user
11087 @item show trace-user
11088 @kindex show trace-user
11090 @item set trace-notes @var{text}
11091 @kindex set trace-notes
11092 Set the trace run's notes.
11094 @item show trace-notes
11095 @kindex show trace-notes
11096 Show the trace run's notes.
11098 @item set trace-stop-notes @var{text}
11099 @kindex set trace-stop-notes
11100 Set the trace run's stop notes. The handling of the note is as for
11101 @code{tstop} arguments; the set command is convenient way to fix a
11102 stop note that is mistaken or incomplete.
11104 @item show trace-stop-notes
11105 @kindex show trace-stop-notes
11106 Show the trace run's stop notes.
11110 @node Tracepoint Restrictions
11111 @subsection Tracepoint Restrictions
11113 @cindex tracepoint restrictions
11114 There are a number of restrictions on the use of tracepoints. As
11115 described above, tracepoint data gathering occurs on the target
11116 without interaction from @value{GDBN}. Thus the full capabilities of
11117 the debugger are not available during data gathering, and then at data
11118 examination time, you will be limited by only having what was
11119 collected. The following items describe some common problems, but it
11120 is not exhaustive, and you may run into additional difficulties not
11126 Tracepoint expressions are intended to gather objects (lvalues). Thus
11127 the full flexibility of GDB's expression evaluator is not available.
11128 You cannot call functions, cast objects to aggregate types, access
11129 convenience variables or modify values (except by assignment to trace
11130 state variables). Some language features may implicitly call
11131 functions (for instance Objective-C fields with accessors), and therefore
11132 cannot be collected either.
11135 Collection of local variables, either individually or in bulk with
11136 @code{$locals} or @code{$args}, during @code{while-stepping} may
11137 behave erratically. The stepping action may enter a new scope (for
11138 instance by stepping into a function), or the location of the variable
11139 may change (for instance it is loaded into a register). The
11140 tracepoint data recorded uses the location information for the
11141 variables that is correct for the tracepoint location. When the
11142 tracepoint is created, it is not possible, in general, to determine
11143 where the steps of a @code{while-stepping} sequence will advance the
11144 program---particularly if a conditional branch is stepped.
11147 Collection of an incompletely-initialized or partially-destroyed object
11148 may result in something that @value{GDBN} cannot display, or displays
11149 in a misleading way.
11152 When @value{GDBN} displays a pointer to character it automatically
11153 dereferences the pointer to also display characters of the string
11154 being pointed to. However, collecting the pointer during tracing does
11155 not automatically collect the string. You need to explicitly
11156 dereference the pointer and provide size information if you want to
11157 collect not only the pointer, but the memory pointed to. For example,
11158 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11162 It is not possible to collect a complete stack backtrace at a
11163 tracepoint. Instead, you may collect the registers and a few hundred
11164 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11165 (adjust to use the name of the actual stack pointer register on your
11166 target architecture, and the amount of stack you wish to capture).
11167 Then the @code{backtrace} command will show a partial backtrace when
11168 using a trace frame. The number of stack frames that can be examined
11169 depends on the sizes of the frames in the collected stack. Note that
11170 if you ask for a block so large that it goes past the bottom of the
11171 stack, the target agent may report an error trying to read from an
11175 If you do not collect registers at a tracepoint, @value{GDBN} can
11176 infer that the value of @code{$pc} must be the same as the address of
11177 the tracepoint and use that when you are looking at a trace frame
11178 for that tracepoint. However, this cannot work if the tracepoint has
11179 multiple locations (for instance if it was set in a function that was
11180 inlined), or if it has a @code{while-stepping} loop. In those cases
11181 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11186 @node Analyze Collected Data
11187 @section Using the Collected Data
11189 After the tracepoint experiment ends, you use @value{GDBN} commands
11190 for examining the trace data. The basic idea is that each tracepoint
11191 collects a trace @dfn{snapshot} every time it is hit and another
11192 snapshot every time it single-steps. All these snapshots are
11193 consecutively numbered from zero and go into a buffer, and you can
11194 examine them later. The way you examine them is to @dfn{focus} on a
11195 specific trace snapshot. When the remote stub is focused on a trace
11196 snapshot, it will respond to all @value{GDBN} requests for memory and
11197 registers by reading from the buffer which belongs to that snapshot,
11198 rather than from @emph{real} memory or registers of the program being
11199 debugged. This means that @strong{all} @value{GDBN} commands
11200 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11201 behave as if we were currently debugging the program state as it was
11202 when the tracepoint occurred. Any requests for data that are not in
11203 the buffer will fail.
11206 * tfind:: How to select a trace snapshot
11207 * tdump:: How to display all data for a snapshot
11208 * save tracepoints:: How to save tracepoints for a future run
11212 @subsection @code{tfind @var{n}}
11215 @cindex select trace snapshot
11216 @cindex find trace snapshot
11217 The basic command for selecting a trace snapshot from the buffer is
11218 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11219 counting from zero. If no argument @var{n} is given, the next
11220 snapshot is selected.
11222 Here are the various forms of using the @code{tfind} command.
11226 Find the first snapshot in the buffer. This is a synonym for
11227 @code{tfind 0} (since 0 is the number of the first snapshot).
11230 Stop debugging trace snapshots, resume @emph{live} debugging.
11233 Same as @samp{tfind none}.
11236 No argument means find the next trace snapshot.
11239 Find the previous trace snapshot before the current one. This permits
11240 retracing earlier steps.
11242 @item tfind tracepoint @var{num}
11243 Find the next snapshot associated with tracepoint @var{num}. Search
11244 proceeds forward from the last examined trace snapshot. If no
11245 argument @var{num} is given, it means find the next snapshot collected
11246 for the same tracepoint as the current snapshot.
11248 @item tfind pc @var{addr}
11249 Find the next snapshot associated with the value @var{addr} of the
11250 program counter. Search proceeds forward from the last examined trace
11251 snapshot. If no argument @var{addr} is given, it means find the next
11252 snapshot with the same value of PC as the current snapshot.
11254 @item tfind outside @var{addr1}, @var{addr2}
11255 Find the next snapshot whose PC is outside the given range of
11256 addresses (exclusive).
11258 @item tfind range @var{addr1}, @var{addr2}
11259 Find the next snapshot whose PC is between @var{addr1} and
11260 @var{addr2} (inclusive).
11262 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11263 Find the next snapshot associated with the source line @var{n}. If
11264 the optional argument @var{file} is given, refer to line @var{n} in
11265 that source file. Search proceeds forward from the last examined
11266 trace snapshot. If no argument @var{n} is given, it means find the
11267 next line other than the one currently being examined; thus saying
11268 @code{tfind line} repeatedly can appear to have the same effect as
11269 stepping from line to line in a @emph{live} debugging session.
11272 The default arguments for the @code{tfind} commands are specifically
11273 designed to make it easy to scan through the trace buffer. For
11274 instance, @code{tfind} with no argument selects the next trace
11275 snapshot, and @code{tfind -} with no argument selects the previous
11276 trace snapshot. So, by giving one @code{tfind} command, and then
11277 simply hitting @key{RET} repeatedly you can examine all the trace
11278 snapshots in order. Or, by saying @code{tfind -} and then hitting
11279 @key{RET} repeatedly you can examine the snapshots in reverse order.
11280 The @code{tfind line} command with no argument selects the snapshot
11281 for the next source line executed. The @code{tfind pc} command with
11282 no argument selects the next snapshot with the same program counter
11283 (PC) as the current frame. The @code{tfind tracepoint} command with
11284 no argument selects the next trace snapshot collected by the same
11285 tracepoint as the current one.
11287 In addition to letting you scan through the trace buffer manually,
11288 these commands make it easy to construct @value{GDBN} scripts that
11289 scan through the trace buffer and print out whatever collected data
11290 you are interested in. Thus, if we want to examine the PC, FP, and SP
11291 registers from each trace frame in the buffer, we can say this:
11294 (@value{GDBP}) @b{tfind start}
11295 (@value{GDBP}) @b{while ($trace_frame != -1)}
11296 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11297 $trace_frame, $pc, $sp, $fp
11301 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11302 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11303 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11304 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11305 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11306 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11307 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11308 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11309 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11310 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11311 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11314 Or, if we want to examine the variable @code{X} at each source line in
11318 (@value{GDBP}) @b{tfind start}
11319 (@value{GDBP}) @b{while ($trace_frame != -1)}
11320 > printf "Frame %d, X == %d\n", $trace_frame, X
11330 @subsection @code{tdump}
11332 @cindex dump all data collected at tracepoint
11333 @cindex tracepoint data, display
11335 This command takes no arguments. It prints all the data collected at
11336 the current trace snapshot.
11339 (@value{GDBP}) @b{trace 444}
11340 (@value{GDBP}) @b{actions}
11341 Enter actions for tracepoint #2, one per line:
11342 > collect $regs, $locals, $args, gdb_long_test
11345 (@value{GDBP}) @b{tstart}
11347 (@value{GDBP}) @b{tfind line 444}
11348 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11350 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11352 (@value{GDBP}) @b{tdump}
11353 Data collected at tracepoint 2, trace frame 1:
11354 d0 0xc4aa0085 -995491707
11358 d4 0x71aea3d 119204413
11361 d7 0x380035 3670069
11362 a0 0x19e24a 1696330
11363 a1 0x3000668 50333288
11365 a3 0x322000 3284992
11366 a4 0x3000698 50333336
11367 a5 0x1ad3cc 1758156
11368 fp 0x30bf3c 0x30bf3c
11369 sp 0x30bf34 0x30bf34
11371 pc 0x20b2c8 0x20b2c8
11375 p = 0x20e5b4 "gdb-test"
11382 gdb_long_test = 17 '\021'
11387 @code{tdump} works by scanning the tracepoint's current collection
11388 actions and printing the value of each expression listed. So
11389 @code{tdump} can fail, if after a run, you change the tracepoint's
11390 actions to mention variables that were not collected during the run.
11392 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11393 uses the collected value of @code{$pc} to distinguish between trace
11394 frames that were collected at the tracepoint hit, and frames that were
11395 collected while stepping. This allows it to correctly choose whether
11396 to display the basic list of collections, or the collections from the
11397 body of the while-stepping loop. However, if @code{$pc} was not collected,
11398 then @code{tdump} will always attempt to dump using the basic collection
11399 list, and may fail if a while-stepping frame does not include all the
11400 same data that is collected at the tracepoint hit.
11401 @c This is getting pretty arcane, example would be good.
11403 @node save tracepoints
11404 @subsection @code{save tracepoints @var{filename}}
11405 @kindex save tracepoints
11406 @kindex save-tracepoints
11407 @cindex save tracepoints for future sessions
11409 This command saves all current tracepoint definitions together with
11410 their actions and passcounts, into a file @file{@var{filename}}
11411 suitable for use in a later debugging session. To read the saved
11412 tracepoint definitions, use the @code{source} command (@pxref{Command
11413 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11414 alias for @w{@code{save tracepoints}}
11416 @node Tracepoint Variables
11417 @section Convenience Variables for Tracepoints
11418 @cindex tracepoint variables
11419 @cindex convenience variables for tracepoints
11422 @vindex $trace_frame
11423 @item (int) $trace_frame
11424 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11425 snapshot is selected.
11427 @vindex $tracepoint
11428 @item (int) $tracepoint
11429 The tracepoint for the current trace snapshot.
11431 @vindex $trace_line
11432 @item (int) $trace_line
11433 The line number for the current trace snapshot.
11435 @vindex $trace_file
11436 @item (char []) $trace_file
11437 The source file for the current trace snapshot.
11439 @vindex $trace_func
11440 @item (char []) $trace_func
11441 The name of the function containing @code{$tracepoint}.
11444 Note: @code{$trace_file} is not suitable for use in @code{printf},
11445 use @code{output} instead.
11447 Here's a simple example of using these convenience variables for
11448 stepping through all the trace snapshots and printing some of their
11449 data. Note that these are not the same as trace state variables,
11450 which are managed by the target.
11453 (@value{GDBP}) @b{tfind start}
11455 (@value{GDBP}) @b{while $trace_frame != -1}
11456 > output $trace_file
11457 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11463 @section Using Trace Files
11464 @cindex trace files
11466 In some situations, the target running a trace experiment may no
11467 longer be available; perhaps it crashed, or the hardware was needed
11468 for a different activity. To handle these cases, you can arrange to
11469 dump the trace data into a file, and later use that file as a source
11470 of trace data, via the @code{target tfile} command.
11475 @item tsave [ -r ] @var{filename}
11476 Save the trace data to @var{filename}. By default, this command
11477 assumes that @var{filename} refers to the host filesystem, so if
11478 necessary @value{GDBN} will copy raw trace data up from the target and
11479 then save it. If the target supports it, you can also supply the
11480 optional argument @code{-r} (``remote'') to direct the target to save
11481 the data directly into @var{filename} in its own filesystem, which may be
11482 more efficient if the trace buffer is very large. (Note, however, that
11483 @code{target tfile} can only read from files accessible to the host.)
11485 @kindex target tfile
11487 @item target tfile @var{filename}
11488 Use the file named @var{filename} as a source of trace data. Commands
11489 that examine data work as they do with a live target, but it is not
11490 possible to run any new trace experiments. @code{tstatus} will report
11491 the state of the trace run at the moment the data was saved, as well
11492 as the current trace frame you are examining. @var{filename} must be
11493 on a filesystem accessible to the host.
11498 @chapter Debugging Programs That Use Overlays
11501 If your program is too large to fit completely in your target system's
11502 memory, you can sometimes use @dfn{overlays} to work around this
11503 problem. @value{GDBN} provides some support for debugging programs that
11507 * How Overlays Work:: A general explanation of overlays.
11508 * Overlay Commands:: Managing overlays in @value{GDBN}.
11509 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11510 mapped by asking the inferior.
11511 * Overlay Sample Program:: A sample program using overlays.
11514 @node How Overlays Work
11515 @section How Overlays Work
11516 @cindex mapped overlays
11517 @cindex unmapped overlays
11518 @cindex load address, overlay's
11519 @cindex mapped address
11520 @cindex overlay area
11522 Suppose you have a computer whose instruction address space is only 64
11523 kilobytes long, but which has much more memory which can be accessed by
11524 other means: special instructions, segment registers, or memory
11525 management hardware, for example. Suppose further that you want to
11526 adapt a program which is larger than 64 kilobytes to run on this system.
11528 One solution is to identify modules of your program which are relatively
11529 independent, and need not call each other directly; call these modules
11530 @dfn{overlays}. Separate the overlays from the main program, and place
11531 their machine code in the larger memory. Place your main program in
11532 instruction memory, but leave at least enough space there to hold the
11533 largest overlay as well.
11535 Now, to call a function located in an overlay, you must first copy that
11536 overlay's machine code from the large memory into the space set aside
11537 for it in the instruction memory, and then jump to its entry point
11540 @c NB: In the below the mapped area's size is greater or equal to the
11541 @c size of all overlays. This is intentional to remind the developer
11542 @c that overlays don't necessarily need to be the same size.
11546 Data Instruction Larger
11547 Address Space Address Space Address Space
11548 +-----------+ +-----------+ +-----------+
11550 +-----------+ +-----------+ +-----------+<-- overlay 1
11551 | program | | main | .----| overlay 1 | load address
11552 | variables | | program | | +-----------+
11553 | and heap | | | | | |
11554 +-----------+ | | | +-----------+<-- overlay 2
11555 | | +-----------+ | | | load address
11556 +-----------+ | | | .-| overlay 2 |
11558 mapped --->+-----------+ | | +-----------+
11559 address | | | | | |
11560 | overlay | <-' | | |
11561 | area | <---' +-----------+<-- overlay 3
11562 | | <---. | | load address
11563 +-----------+ `--| overlay 3 |
11570 @anchor{A code overlay}A code overlay
11574 The diagram (@pxref{A code overlay}) shows a system with separate data
11575 and instruction address spaces. To map an overlay, the program copies
11576 its code from the larger address space to the instruction address space.
11577 Since the overlays shown here all use the same mapped address, only one
11578 may be mapped at a time. For a system with a single address space for
11579 data and instructions, the diagram would be similar, except that the
11580 program variables and heap would share an address space with the main
11581 program and the overlay area.
11583 An overlay loaded into instruction memory and ready for use is called a
11584 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11585 instruction memory. An overlay not present (or only partially present)
11586 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11587 is its address in the larger memory. The mapped address is also called
11588 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11589 called the @dfn{load memory address}, or @dfn{LMA}.
11591 Unfortunately, overlays are not a completely transparent way to adapt a
11592 program to limited instruction memory. They introduce a new set of
11593 global constraints you must keep in mind as you design your program:
11598 Before calling or returning to a function in an overlay, your program
11599 must make sure that overlay is actually mapped. Otherwise, the call or
11600 return will transfer control to the right address, but in the wrong
11601 overlay, and your program will probably crash.
11604 If the process of mapping an overlay is expensive on your system, you
11605 will need to choose your overlays carefully to minimize their effect on
11606 your program's performance.
11609 The executable file you load onto your system must contain each
11610 overlay's instructions, appearing at the overlay's load address, not its
11611 mapped address. However, each overlay's instructions must be relocated
11612 and its symbols defined as if the overlay were at its mapped address.
11613 You can use GNU linker scripts to specify different load and relocation
11614 addresses for pieces of your program; see @ref{Overlay Description,,,
11615 ld.info, Using ld: the GNU linker}.
11618 The procedure for loading executable files onto your system must be able
11619 to load their contents into the larger address space as well as the
11620 instruction and data spaces.
11624 The overlay system described above is rather simple, and could be
11625 improved in many ways:
11630 If your system has suitable bank switch registers or memory management
11631 hardware, you could use those facilities to make an overlay's load area
11632 contents simply appear at their mapped address in instruction space.
11633 This would probably be faster than copying the overlay to its mapped
11634 area in the usual way.
11637 If your overlays are small enough, you could set aside more than one
11638 overlay area, and have more than one overlay mapped at a time.
11641 You can use overlays to manage data, as well as instructions. In
11642 general, data overlays are even less transparent to your design than
11643 code overlays: whereas code overlays only require care when you call or
11644 return to functions, data overlays require care every time you access
11645 the data. Also, if you change the contents of a data overlay, you
11646 must copy its contents back out to its load address before you can copy a
11647 different data overlay into the same mapped area.
11652 @node Overlay Commands
11653 @section Overlay Commands
11655 To use @value{GDBN}'s overlay support, each overlay in your program must
11656 correspond to a separate section of the executable file. The section's
11657 virtual memory address and load memory address must be the overlay's
11658 mapped and load addresses. Identifying overlays with sections allows
11659 @value{GDBN} to determine the appropriate address of a function or
11660 variable, depending on whether the overlay is mapped or not.
11662 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11663 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11668 Disable @value{GDBN}'s overlay support. When overlay support is
11669 disabled, @value{GDBN} assumes that all functions and variables are
11670 always present at their mapped addresses. By default, @value{GDBN}'s
11671 overlay support is disabled.
11673 @item overlay manual
11674 @cindex manual overlay debugging
11675 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11676 relies on you to tell it which overlays are mapped, and which are not,
11677 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11678 commands described below.
11680 @item overlay map-overlay @var{overlay}
11681 @itemx overlay map @var{overlay}
11682 @cindex map an overlay
11683 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11684 be the name of the object file section containing the overlay. When an
11685 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11686 functions and variables at their mapped addresses. @value{GDBN} assumes
11687 that any other overlays whose mapped ranges overlap that of
11688 @var{overlay} are now unmapped.
11690 @item overlay unmap-overlay @var{overlay}
11691 @itemx overlay unmap @var{overlay}
11692 @cindex unmap an overlay
11693 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11694 must be the name of the object file section containing the overlay.
11695 When an overlay is unmapped, @value{GDBN} assumes it can find the
11696 overlay's functions and variables at their load addresses.
11699 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11700 consults a data structure the overlay manager maintains in the inferior
11701 to see which overlays are mapped. For details, see @ref{Automatic
11702 Overlay Debugging}.
11704 @item overlay load-target
11705 @itemx overlay load
11706 @cindex reloading the overlay table
11707 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11708 re-reads the table @value{GDBN} automatically each time the inferior
11709 stops, so this command should only be necessary if you have changed the
11710 overlay mapping yourself using @value{GDBN}. This command is only
11711 useful when using automatic overlay debugging.
11713 @item overlay list-overlays
11714 @itemx overlay list
11715 @cindex listing mapped overlays
11716 Display a list of the overlays currently mapped, along with their mapped
11717 addresses, load addresses, and sizes.
11721 Normally, when @value{GDBN} prints a code address, it includes the name
11722 of the function the address falls in:
11725 (@value{GDBP}) print main
11726 $3 = @{int ()@} 0x11a0 <main>
11729 When overlay debugging is enabled, @value{GDBN} recognizes code in
11730 unmapped overlays, and prints the names of unmapped functions with
11731 asterisks around them. For example, if @code{foo} is a function in an
11732 unmapped overlay, @value{GDBN} prints it this way:
11735 (@value{GDBP}) overlay list
11736 No sections are mapped.
11737 (@value{GDBP}) print foo
11738 $5 = @{int (int)@} 0x100000 <*foo*>
11741 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11745 (@value{GDBP}) overlay list
11746 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11747 mapped at 0x1016 - 0x104a
11748 (@value{GDBP}) print foo
11749 $6 = @{int (int)@} 0x1016 <foo>
11752 When overlay debugging is enabled, @value{GDBN} can find the correct
11753 address for functions and variables in an overlay, whether or not the
11754 overlay is mapped. This allows most @value{GDBN} commands, like
11755 @code{break} and @code{disassemble}, to work normally, even on unmapped
11756 code. However, @value{GDBN}'s breakpoint support has some limitations:
11760 @cindex breakpoints in overlays
11761 @cindex overlays, setting breakpoints in
11762 You can set breakpoints in functions in unmapped overlays, as long as
11763 @value{GDBN} can write to the overlay at its load address.
11765 @value{GDBN} can not set hardware or simulator-based breakpoints in
11766 unmapped overlays. However, if you set a breakpoint at the end of your
11767 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11768 you are using manual overlay management), @value{GDBN} will re-set its
11769 breakpoints properly.
11773 @node Automatic Overlay Debugging
11774 @section Automatic Overlay Debugging
11775 @cindex automatic overlay debugging
11777 @value{GDBN} can automatically track which overlays are mapped and which
11778 are not, given some simple co-operation from the overlay manager in the
11779 inferior. If you enable automatic overlay debugging with the
11780 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11781 looks in the inferior's memory for certain variables describing the
11782 current state of the overlays.
11784 Here are the variables your overlay manager must define to support
11785 @value{GDBN}'s automatic overlay debugging:
11789 @item @code{_ovly_table}:
11790 This variable must be an array of the following structures:
11795 /* The overlay's mapped address. */
11798 /* The size of the overlay, in bytes. */
11799 unsigned long size;
11801 /* The overlay's load address. */
11804 /* Non-zero if the overlay is currently mapped;
11806 unsigned long mapped;
11810 @item @code{_novlys}:
11811 This variable must be a four-byte signed integer, holding the total
11812 number of elements in @code{_ovly_table}.
11816 To decide whether a particular overlay is mapped or not, @value{GDBN}
11817 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11818 @code{lma} members equal the VMA and LMA of the overlay's section in the
11819 executable file. When @value{GDBN} finds a matching entry, it consults
11820 the entry's @code{mapped} member to determine whether the overlay is
11823 In addition, your overlay manager may define a function called
11824 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11825 will silently set a breakpoint there. If the overlay manager then
11826 calls this function whenever it has changed the overlay table, this
11827 will enable @value{GDBN} to accurately keep track of which overlays
11828 are in program memory, and update any breakpoints that may be set
11829 in overlays. This will allow breakpoints to work even if the
11830 overlays are kept in ROM or other non-writable memory while they
11831 are not being executed.
11833 @node Overlay Sample Program
11834 @section Overlay Sample Program
11835 @cindex overlay example program
11837 When linking a program which uses overlays, you must place the overlays
11838 at their load addresses, while relocating them to run at their mapped
11839 addresses. To do this, you must write a linker script (@pxref{Overlay
11840 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11841 since linker scripts are specific to a particular host system, target
11842 architecture, and target memory layout, this manual cannot provide
11843 portable sample code demonstrating @value{GDBN}'s overlay support.
11845 However, the @value{GDBN} source distribution does contain an overlaid
11846 program, with linker scripts for a few systems, as part of its test
11847 suite. The program consists of the following files from
11848 @file{gdb/testsuite/gdb.base}:
11852 The main program file.
11854 A simple overlay manager, used by @file{overlays.c}.
11859 Overlay modules, loaded and used by @file{overlays.c}.
11862 Linker scripts for linking the test program on the @code{d10v-elf}
11863 and @code{m32r-elf} targets.
11866 You can build the test program using the @code{d10v-elf} GCC
11867 cross-compiler like this:
11870 $ d10v-elf-gcc -g -c overlays.c
11871 $ d10v-elf-gcc -g -c ovlymgr.c
11872 $ d10v-elf-gcc -g -c foo.c
11873 $ d10v-elf-gcc -g -c bar.c
11874 $ d10v-elf-gcc -g -c baz.c
11875 $ d10v-elf-gcc -g -c grbx.c
11876 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11877 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11880 The build process is identical for any other architecture, except that
11881 you must substitute the appropriate compiler and linker script for the
11882 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11886 @chapter Using @value{GDBN} with Different Languages
11889 Although programming languages generally have common aspects, they are
11890 rarely expressed in the same manner. For instance, in ANSI C,
11891 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11892 Modula-2, it is accomplished by @code{p^}. Values can also be
11893 represented (and displayed) differently. Hex numbers in C appear as
11894 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11896 @cindex working language
11897 Language-specific information is built into @value{GDBN} for some languages,
11898 allowing you to express operations like the above in your program's
11899 native language, and allowing @value{GDBN} to output values in a manner
11900 consistent with the syntax of your program's native language. The
11901 language you use to build expressions is called the @dfn{working
11905 * Setting:: Switching between source languages
11906 * Show:: Displaying the language
11907 * Checks:: Type and range checks
11908 * Supported Languages:: Supported languages
11909 * Unsupported Languages:: Unsupported languages
11913 @section Switching Between Source Languages
11915 There are two ways to control the working language---either have @value{GDBN}
11916 set it automatically, or select it manually yourself. You can use the
11917 @code{set language} command for either purpose. On startup, @value{GDBN}
11918 defaults to setting the language automatically. The working language is
11919 used to determine how expressions you type are interpreted, how values
11922 In addition to the working language, every source file that
11923 @value{GDBN} knows about has its own working language. For some object
11924 file formats, the compiler might indicate which language a particular
11925 source file is in. However, most of the time @value{GDBN} infers the
11926 language from the name of the file. The language of a source file
11927 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11928 show each frame appropriately for its own language. There is no way to
11929 set the language of a source file from within @value{GDBN}, but you can
11930 set the language associated with a filename extension. @xref{Show, ,
11931 Displaying the Language}.
11933 This is most commonly a problem when you use a program, such
11934 as @code{cfront} or @code{f2c}, that generates C but is written in
11935 another language. In that case, make the
11936 program use @code{#line} directives in its C output; that way
11937 @value{GDBN} will know the correct language of the source code of the original
11938 program, and will display that source code, not the generated C code.
11941 * Filenames:: Filename extensions and languages.
11942 * Manually:: Setting the working language manually
11943 * Automatically:: Having @value{GDBN} infer the source language
11947 @subsection List of Filename Extensions and Languages
11949 If a source file name ends in one of the following extensions, then
11950 @value{GDBN} infers that its language is the one indicated.
11968 C@t{++} source file
11974 Objective-C source file
11978 Fortran source file
11981 Modula-2 source file
11985 Assembler source file. This actually behaves almost like C, but
11986 @value{GDBN} does not skip over function prologues when stepping.
11989 In addition, you may set the language associated with a filename
11990 extension. @xref{Show, , Displaying the Language}.
11993 @subsection Setting the Working Language
11995 If you allow @value{GDBN} to set the language automatically,
11996 expressions are interpreted the same way in your debugging session and
11999 @kindex set language
12000 If you wish, you may set the language manually. To do this, issue the
12001 command @samp{set language @var{lang}}, where @var{lang} is the name of
12002 a language, such as
12003 @code{c} or @code{modula-2}.
12004 For a list of the supported languages, type @samp{set language}.
12006 Setting the language manually prevents @value{GDBN} from updating the working
12007 language automatically. This can lead to confusion if you try
12008 to debug a program when the working language is not the same as the
12009 source language, when an expression is acceptable to both
12010 languages---but means different things. For instance, if the current
12011 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12019 might not have the effect you intended. In C, this means to add
12020 @code{b} and @code{c} and place the result in @code{a}. The result
12021 printed would be the value of @code{a}. In Modula-2, this means to compare
12022 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12024 @node Automatically
12025 @subsection Having @value{GDBN} Infer the Source Language
12027 To have @value{GDBN} set the working language automatically, use
12028 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12029 then infers the working language. That is, when your program stops in a
12030 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12031 working language to the language recorded for the function in that
12032 frame. If the language for a frame is unknown (that is, if the function
12033 or block corresponding to the frame was defined in a source file that
12034 does not have a recognized extension), the current working language is
12035 not changed, and @value{GDBN} issues a warning.
12037 This may not seem necessary for most programs, which are written
12038 entirely in one source language. However, program modules and libraries
12039 written in one source language can be used by a main program written in
12040 a different source language. Using @samp{set language auto} in this
12041 case frees you from having to set the working language manually.
12044 @section Displaying the Language
12046 The following commands help you find out which language is the
12047 working language, and also what language source files were written in.
12050 @item show language
12051 @kindex show language
12052 Display the current working language. This is the
12053 language you can use with commands such as @code{print} to
12054 build and compute expressions that may involve variables in your program.
12057 @kindex info frame@r{, show the source language}
12058 Display the source language for this frame. This language becomes the
12059 working language if you use an identifier from this frame.
12060 @xref{Frame Info, ,Information about a Frame}, to identify the other
12061 information listed here.
12064 @kindex info source@r{, show the source language}
12065 Display the source language of this source file.
12066 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12067 information listed here.
12070 In unusual circumstances, you may have source files with extensions
12071 not in the standard list. You can then set the extension associated
12072 with a language explicitly:
12075 @item set extension-language @var{ext} @var{language}
12076 @kindex set extension-language
12077 Tell @value{GDBN} that source files with extension @var{ext} are to be
12078 assumed as written in the source language @var{language}.
12080 @item info extensions
12081 @kindex info extensions
12082 List all the filename extensions and the associated languages.
12086 @section Type and Range Checking
12089 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12090 checking are included, but they do not yet have any effect. This
12091 section documents the intended facilities.
12093 @c FIXME remove warning when type/range code added
12095 Some languages are designed to guard you against making seemingly common
12096 errors through a series of compile- and run-time checks. These include
12097 checking the type of arguments to functions and operators, and making
12098 sure mathematical overflows are caught at run time. Checks such as
12099 these help to ensure a program's correctness once it has been compiled
12100 by eliminating type mismatches, and providing active checks for range
12101 errors when your program is running.
12103 @value{GDBN} can check for conditions like the above if you wish.
12104 Although @value{GDBN} does not check the statements in your program,
12105 it can check expressions entered directly into @value{GDBN} for
12106 evaluation via the @code{print} command, for example. As with the
12107 working language, @value{GDBN} can also decide whether or not to check
12108 automatically based on your program's source language.
12109 @xref{Supported Languages, ,Supported Languages}, for the default
12110 settings of supported languages.
12113 * Type Checking:: An overview of type checking
12114 * Range Checking:: An overview of range checking
12117 @cindex type checking
12118 @cindex checks, type
12119 @node Type Checking
12120 @subsection An Overview of Type Checking
12122 Some languages, such as Modula-2, are strongly typed, meaning that the
12123 arguments to operators and functions have to be of the correct type,
12124 otherwise an error occurs. These checks prevent type mismatch
12125 errors from ever causing any run-time problems. For example,
12133 The second example fails because the @code{CARDINAL} 1 is not
12134 type-compatible with the @code{REAL} 2.3.
12136 For the expressions you use in @value{GDBN} commands, you can tell the
12137 @value{GDBN} type checker to skip checking;
12138 to treat any mismatches as errors and abandon the expression;
12139 or to only issue warnings when type mismatches occur,
12140 but evaluate the expression anyway. When you choose the last of
12141 these, @value{GDBN} evaluates expressions like the second example above, but
12142 also issues a warning.
12144 Even if you turn type checking off, there may be other reasons
12145 related to type that prevent @value{GDBN} from evaluating an expression.
12146 For instance, @value{GDBN} does not know how to add an @code{int} and
12147 a @code{struct foo}. These particular type errors have nothing to do
12148 with the language in use, and usually arise from expressions, such as
12149 the one described above, which make little sense to evaluate anyway.
12151 Each language defines to what degree it is strict about type. For
12152 instance, both Modula-2 and C require the arguments to arithmetical
12153 operators to be numbers. In C, enumerated types and pointers can be
12154 represented as numbers, so that they are valid arguments to mathematical
12155 operators. @xref{Supported Languages, ,Supported Languages}, for further
12156 details on specific languages.
12158 @value{GDBN} provides some additional commands for controlling the type checker:
12160 @kindex set check type
12161 @kindex show check type
12163 @item set check type auto
12164 Set type checking on or off based on the current working language.
12165 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12168 @item set check type on
12169 @itemx set check type off
12170 Set type checking on or off, overriding the default setting for the
12171 current working language. Issue a warning if the setting does not
12172 match the language default. If any type mismatches occur in
12173 evaluating an expression while type checking is on, @value{GDBN} prints a
12174 message and aborts evaluation of the expression.
12176 @item set check type warn
12177 Cause the type checker to issue warnings, but to always attempt to
12178 evaluate the expression. Evaluating the expression may still
12179 be impossible for other reasons. For example, @value{GDBN} cannot add
12180 numbers and structures.
12183 Show the current setting of the type checker, and whether or not @value{GDBN}
12184 is setting it automatically.
12187 @cindex range checking
12188 @cindex checks, range
12189 @node Range Checking
12190 @subsection An Overview of Range Checking
12192 In some languages (such as Modula-2), it is an error to exceed the
12193 bounds of a type; this is enforced with run-time checks. Such range
12194 checking is meant to ensure program correctness by making sure
12195 computations do not overflow, or indices on an array element access do
12196 not exceed the bounds of the array.
12198 For expressions you use in @value{GDBN} commands, you can tell
12199 @value{GDBN} to treat range errors in one of three ways: ignore them,
12200 always treat them as errors and abandon the expression, or issue
12201 warnings but evaluate the expression anyway.
12203 A range error can result from numerical overflow, from exceeding an
12204 array index bound, or when you type a constant that is not a member
12205 of any type. Some languages, however, do not treat overflows as an
12206 error. In many implementations of C, mathematical overflow causes the
12207 result to ``wrap around'' to lower values---for example, if @var{m} is
12208 the largest integer value, and @var{s} is the smallest, then
12211 @var{m} + 1 @result{} @var{s}
12214 This, too, is specific to individual languages, and in some cases
12215 specific to individual compilers or machines. @xref{Supported Languages, ,
12216 Supported Languages}, for further details on specific languages.
12218 @value{GDBN} provides some additional commands for controlling the range checker:
12220 @kindex set check range
12221 @kindex show check range
12223 @item set check range auto
12224 Set range checking on or off based on the current working language.
12225 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12228 @item set check range on
12229 @itemx set check range off
12230 Set range checking on or off, overriding the default setting for the
12231 current working language. A warning is issued if the setting does not
12232 match the language default. If a range error occurs and range checking is on,
12233 then a message is printed and evaluation of the expression is aborted.
12235 @item set check range warn
12236 Output messages when the @value{GDBN} range checker detects a range error,
12237 but attempt to evaluate the expression anyway. Evaluating the
12238 expression may still be impossible for other reasons, such as accessing
12239 memory that the process does not own (a typical example from many Unix
12243 Show the current setting of the range checker, and whether or not it is
12244 being set automatically by @value{GDBN}.
12247 @node Supported Languages
12248 @section Supported Languages
12250 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12251 assembly, Modula-2, and Ada.
12252 @c This is false ...
12253 Some @value{GDBN} features may be used in expressions regardless of the
12254 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12255 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12256 ,Expressions}) can be used with the constructs of any supported
12259 The following sections detail to what degree each source language is
12260 supported by @value{GDBN}. These sections are not meant to be language
12261 tutorials or references, but serve only as a reference guide to what the
12262 @value{GDBN} expression parser accepts, and what input and output
12263 formats should look like for different languages. There are many good
12264 books written on each of these languages; please look to these for a
12265 language reference or tutorial.
12268 * C:: C and C@t{++}
12270 * Objective-C:: Objective-C
12271 * OpenCL C:: OpenCL C
12272 * Fortran:: Fortran
12274 * Modula-2:: Modula-2
12279 @subsection C and C@t{++}
12281 @cindex C and C@t{++}
12282 @cindex expressions in C or C@t{++}
12284 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12285 to both languages. Whenever this is the case, we discuss those languages
12289 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12290 @cindex @sc{gnu} C@t{++}
12291 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12292 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12293 effectively, you must compile your C@t{++} programs with a supported
12294 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12295 compiler (@code{aCC}).
12298 * C Operators:: C and C@t{++} operators
12299 * C Constants:: C and C@t{++} constants
12300 * C Plus Plus Expressions:: C@t{++} expressions
12301 * C Defaults:: Default settings for C and C@t{++}
12302 * C Checks:: C and C@t{++} type and range checks
12303 * Debugging C:: @value{GDBN} and C
12304 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12305 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12309 @subsubsection C and C@t{++} Operators
12311 @cindex C and C@t{++} operators
12313 Operators must be defined on values of specific types. For instance,
12314 @code{+} is defined on numbers, but not on structures. Operators are
12315 often defined on groups of types.
12317 For the purposes of C and C@t{++}, the following definitions hold:
12322 @emph{Integral types} include @code{int} with any of its storage-class
12323 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12326 @emph{Floating-point types} include @code{float}, @code{double}, and
12327 @code{long double} (if supported by the target platform).
12330 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12333 @emph{Scalar types} include all of the above.
12338 The following operators are supported. They are listed here
12339 in order of increasing precedence:
12343 The comma or sequencing operator. Expressions in a comma-separated list
12344 are evaluated from left to right, with the result of the entire
12345 expression being the last expression evaluated.
12348 Assignment. The value of an assignment expression is the value
12349 assigned. Defined on scalar types.
12352 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12353 and translated to @w{@code{@var{a} = @var{a op b}}}.
12354 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12355 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12356 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12359 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12360 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12364 Logical @sc{or}. Defined on integral types.
12367 Logical @sc{and}. Defined on integral types.
12370 Bitwise @sc{or}. Defined on integral types.
12373 Bitwise exclusive-@sc{or}. Defined on integral types.
12376 Bitwise @sc{and}. Defined on integral types.
12379 Equality and inequality. Defined on scalar types. The value of these
12380 expressions is 0 for false and non-zero for true.
12382 @item <@r{, }>@r{, }<=@r{, }>=
12383 Less than, greater than, less than or equal, greater than or equal.
12384 Defined on scalar types. The value of these expressions is 0 for false
12385 and non-zero for true.
12388 left shift, and right shift. Defined on integral types.
12391 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12394 Addition and subtraction. Defined on integral types, floating-point types and
12397 @item *@r{, }/@r{, }%
12398 Multiplication, division, and modulus. Multiplication and division are
12399 defined on integral and floating-point types. Modulus is defined on
12403 Increment and decrement. When appearing before a variable, the
12404 operation is performed before the variable is used in an expression;
12405 when appearing after it, the variable's value is used before the
12406 operation takes place.
12409 Pointer dereferencing. Defined on pointer types. Same precedence as
12413 Address operator. Defined on variables. Same precedence as @code{++}.
12415 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12416 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12417 to examine the address
12418 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12422 Negative. Defined on integral and floating-point types. Same
12423 precedence as @code{++}.
12426 Logical negation. Defined on integral types. Same precedence as
12430 Bitwise complement operator. Defined on integral types. Same precedence as
12435 Structure member, and pointer-to-structure member. For convenience,
12436 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12437 pointer based on the stored type information.
12438 Defined on @code{struct} and @code{union} data.
12441 Dereferences of pointers to members.
12444 Array indexing. @code{@var{a}[@var{i}]} is defined as
12445 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12448 Function parameter list. Same precedence as @code{->}.
12451 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12452 and @code{class} types.
12455 Doubled colons also represent the @value{GDBN} scope operator
12456 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12460 If an operator is redefined in the user code, @value{GDBN} usually
12461 attempts to invoke the redefined version instead of using the operator's
12462 predefined meaning.
12465 @subsubsection C and C@t{++} Constants
12467 @cindex C and C@t{++} constants
12469 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12474 Integer constants are a sequence of digits. Octal constants are
12475 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12476 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12477 @samp{l}, specifying that the constant should be treated as a
12481 Floating point constants are a sequence of digits, followed by a decimal
12482 point, followed by a sequence of digits, and optionally followed by an
12483 exponent. An exponent is of the form:
12484 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12485 sequence of digits. The @samp{+} is optional for positive exponents.
12486 A floating-point constant may also end with a letter @samp{f} or
12487 @samp{F}, specifying that the constant should be treated as being of
12488 the @code{float} (as opposed to the default @code{double}) type; or with
12489 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12493 Enumerated constants consist of enumerated identifiers, or their
12494 integral equivalents.
12497 Character constants are a single character surrounded by single quotes
12498 (@code{'}), or a number---the ordinal value of the corresponding character
12499 (usually its @sc{ascii} value). Within quotes, the single character may
12500 be represented by a letter or by @dfn{escape sequences}, which are of
12501 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12502 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12503 @samp{@var{x}} is a predefined special character---for example,
12504 @samp{\n} for newline.
12506 Wide character constants can be written by prefixing a character
12507 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12508 form of @samp{x}. The target wide character set is used when
12509 computing the value of this constant (@pxref{Character Sets}).
12512 String constants are a sequence of character constants surrounded by
12513 double quotes (@code{"}). Any valid character constant (as described
12514 above) may appear. Double quotes within the string must be preceded by
12515 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12518 Wide string constants can be written by prefixing a string constant
12519 with @samp{L}, as in C. The target wide character set is used when
12520 computing the value of this constant (@pxref{Character Sets}).
12523 Pointer constants are an integral value. You can also write pointers
12524 to constants using the C operator @samp{&}.
12527 Array constants are comma-separated lists surrounded by braces @samp{@{}
12528 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12529 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12530 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12533 @node C Plus Plus Expressions
12534 @subsubsection C@t{++} Expressions
12536 @cindex expressions in C@t{++}
12537 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12539 @cindex debugging C@t{++} programs
12540 @cindex C@t{++} compilers
12541 @cindex debug formats and C@t{++}
12542 @cindex @value{NGCC} and C@t{++}
12544 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12545 the proper compiler and the proper debug format. Currently,
12546 @value{GDBN} works best when debugging C@t{++} code that is compiled
12547 with the most recent version of @value{NGCC} possible. The DWARF
12548 debugging format is preferred; @value{NGCC} defaults to this on most
12549 popular platforms. Other compilers and/or debug formats are likely to
12550 work badly or not at all when using @value{GDBN} to debug C@t{++}
12551 code. @xref{Compilation}.
12556 @cindex member functions
12558 Member function calls are allowed; you can use expressions like
12561 count = aml->GetOriginal(x, y)
12564 @vindex this@r{, inside C@t{++} member functions}
12565 @cindex namespace in C@t{++}
12567 While a member function is active (in the selected stack frame), your
12568 expressions have the same namespace available as the member function;
12569 that is, @value{GDBN} allows implicit references to the class instance
12570 pointer @code{this} following the same rules as C@t{++}. @code{using}
12571 declarations in the current scope are also respected by @value{GDBN}.
12573 @cindex call overloaded functions
12574 @cindex overloaded functions, calling
12575 @cindex type conversions in C@t{++}
12577 You can call overloaded functions; @value{GDBN} resolves the function
12578 call to the right definition, with some restrictions. @value{GDBN} does not
12579 perform overload resolution involving user-defined type conversions,
12580 calls to constructors, or instantiations of templates that do not exist
12581 in the program. It also cannot handle ellipsis argument lists or
12584 It does perform integral conversions and promotions, floating-point
12585 promotions, arithmetic conversions, pointer conversions, conversions of
12586 class objects to base classes, and standard conversions such as those of
12587 functions or arrays to pointers; it requires an exact match on the
12588 number of function arguments.
12590 Overload resolution is always performed, unless you have specified
12591 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12592 ,@value{GDBN} Features for C@t{++}}.
12594 You must specify @code{set overload-resolution off} in order to use an
12595 explicit function signature to call an overloaded function, as in
12597 p 'foo(char,int)'('x', 13)
12600 The @value{GDBN} command-completion facility can simplify this;
12601 see @ref{Completion, ,Command Completion}.
12603 @cindex reference declarations
12605 @value{GDBN} understands variables declared as C@t{++} references; you can use
12606 them in expressions just as you do in C@t{++} source---they are automatically
12609 In the parameter list shown when @value{GDBN} displays a frame, the values of
12610 reference variables are not displayed (unlike other variables); this
12611 avoids clutter, since references are often used for large structures.
12612 The @emph{address} of a reference variable is always shown, unless
12613 you have specified @samp{set print address off}.
12616 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12617 expressions can use it just as expressions in your program do. Since
12618 one scope may be defined in another, you can use @code{::} repeatedly if
12619 necessary, for example in an expression like
12620 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12621 resolving name scope by reference to source files, in both C and C@t{++}
12622 debugging (@pxref{Variables, ,Program Variables}).
12625 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12630 @subsubsection C and C@t{++} Defaults
12632 @cindex C and C@t{++} defaults
12634 If you allow @value{GDBN} to set type and range checking automatically, they
12635 both default to @code{off} whenever the working language changes to
12636 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12637 selects the working language.
12639 If you allow @value{GDBN} to set the language automatically, it
12640 recognizes source files whose names end with @file{.c}, @file{.C}, or
12641 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12642 these files, it sets the working language to C or C@t{++}.
12643 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12644 for further details.
12646 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12647 @c unimplemented. If (b) changes, it might make sense to let this node
12648 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12651 @subsubsection C and C@t{++} Type and Range Checks
12653 @cindex C and C@t{++} checks
12655 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12656 is not used. However, if you turn type checking on, @value{GDBN}
12657 considers two variables type equivalent if:
12661 The two variables are structured and have the same structure, union, or
12665 The two variables have the same type name, or types that have been
12666 declared equivalent through @code{typedef}.
12669 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12672 The two @code{struct}, @code{union}, or @code{enum} variables are
12673 declared in the same declaration. (Note: this may not be true for all C
12678 Range checking, if turned on, is done on mathematical operations. Array
12679 indices are not checked, since they are often used to index a pointer
12680 that is not itself an array.
12683 @subsubsection @value{GDBN} and C
12685 The @code{set print union} and @code{show print union} commands apply to
12686 the @code{union} type. When set to @samp{on}, any @code{union} that is
12687 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12688 appears as @samp{@{...@}}.
12690 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12691 with pointers and a memory allocation function. @xref{Expressions,
12694 @node Debugging C Plus Plus
12695 @subsubsection @value{GDBN} Features for C@t{++}
12697 @cindex commands for C@t{++}
12699 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12700 designed specifically for use with C@t{++}. Here is a summary:
12703 @cindex break in overloaded functions
12704 @item @r{breakpoint menus}
12705 When you want a breakpoint in a function whose name is overloaded,
12706 @value{GDBN} has the capability to display a menu of possible breakpoint
12707 locations to help you specify which function definition you want.
12708 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12710 @cindex overloading in C@t{++}
12711 @item rbreak @var{regex}
12712 Setting breakpoints using regular expressions is helpful for setting
12713 breakpoints on overloaded functions that are not members of any special
12715 @xref{Set Breaks, ,Setting Breakpoints}.
12717 @cindex C@t{++} exception handling
12720 Debug C@t{++} exception handling using these commands. @xref{Set
12721 Catchpoints, , Setting Catchpoints}.
12723 @cindex inheritance
12724 @item ptype @var{typename}
12725 Print inheritance relationships as well as other information for type
12727 @xref{Symbols, ,Examining the Symbol Table}.
12729 @cindex C@t{++} symbol display
12730 @item set print demangle
12731 @itemx show print demangle
12732 @itemx set print asm-demangle
12733 @itemx show print asm-demangle
12734 Control whether C@t{++} symbols display in their source form, both when
12735 displaying code as C@t{++} source and when displaying disassemblies.
12736 @xref{Print Settings, ,Print Settings}.
12738 @item set print object
12739 @itemx show print object
12740 Choose whether to print derived (actual) or declared types of objects.
12741 @xref{Print Settings, ,Print Settings}.
12743 @item set print vtbl
12744 @itemx show print vtbl
12745 Control the format for printing virtual function tables.
12746 @xref{Print Settings, ,Print Settings}.
12747 (The @code{vtbl} commands do not work on programs compiled with the HP
12748 ANSI C@t{++} compiler (@code{aCC}).)
12750 @kindex set overload-resolution
12751 @cindex overloaded functions, overload resolution
12752 @item set overload-resolution on
12753 Enable overload resolution for C@t{++} expression evaluation. The default
12754 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12755 and searches for a function whose signature matches the argument types,
12756 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12757 Expressions, ,C@t{++} Expressions}, for details).
12758 If it cannot find a match, it emits a message.
12760 @item set overload-resolution off
12761 Disable overload resolution for C@t{++} expression evaluation. For
12762 overloaded functions that are not class member functions, @value{GDBN}
12763 chooses the first function of the specified name that it finds in the
12764 symbol table, whether or not its arguments are of the correct type. For
12765 overloaded functions that are class member functions, @value{GDBN}
12766 searches for a function whose signature @emph{exactly} matches the
12769 @kindex show overload-resolution
12770 @item show overload-resolution
12771 Show the current setting of overload resolution.
12773 @item @r{Overloaded symbol names}
12774 You can specify a particular definition of an overloaded symbol, using
12775 the same notation that is used to declare such symbols in C@t{++}: type
12776 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12777 also use the @value{GDBN} command-line word completion facilities to list the
12778 available choices, or to finish the type list for you.
12779 @xref{Completion,, Command Completion}, for details on how to do this.
12782 @node Decimal Floating Point
12783 @subsubsection Decimal Floating Point format
12784 @cindex decimal floating point format
12786 @value{GDBN} can examine, set and perform computations with numbers in
12787 decimal floating point format, which in the C language correspond to the
12788 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12789 specified by the extension to support decimal floating-point arithmetic.
12791 There are two encodings in use, depending on the architecture: BID (Binary
12792 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12793 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12796 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12797 to manipulate decimal floating point numbers, it is not possible to convert
12798 (using a cast, for example) integers wider than 32-bit to decimal float.
12800 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12801 point computations, error checking in decimal float operations ignores
12802 underflow, overflow and divide by zero exceptions.
12804 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12805 to inspect @code{_Decimal128} values stored in floating point registers.
12806 See @ref{PowerPC,,PowerPC} for more details.
12812 @value{GDBN} can be used to debug programs written in D and compiled with
12813 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12814 specific feature --- dynamic arrays.
12817 @subsection Objective-C
12819 @cindex Objective-C
12820 This section provides information about some commands and command
12821 options that are useful for debugging Objective-C code. See also
12822 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12823 few more commands specific to Objective-C support.
12826 * Method Names in Commands::
12827 * The Print Command with Objective-C::
12830 @node Method Names in Commands
12831 @subsubsection Method Names in Commands
12833 The following commands have been extended to accept Objective-C method
12834 names as line specifications:
12836 @kindex clear@r{, and Objective-C}
12837 @kindex break@r{, and Objective-C}
12838 @kindex info line@r{, and Objective-C}
12839 @kindex jump@r{, and Objective-C}
12840 @kindex list@r{, and Objective-C}
12844 @item @code{info line}
12849 A fully qualified Objective-C method name is specified as
12852 -[@var{Class} @var{methodName}]
12855 where the minus sign is used to indicate an instance method and a
12856 plus sign (not shown) is used to indicate a class method. The class
12857 name @var{Class} and method name @var{methodName} are enclosed in
12858 brackets, similar to the way messages are specified in Objective-C
12859 source code. For example, to set a breakpoint at the @code{create}
12860 instance method of class @code{Fruit} in the program currently being
12864 break -[Fruit create]
12867 To list ten program lines around the @code{initialize} class method,
12871 list +[NSText initialize]
12874 In the current version of @value{GDBN}, the plus or minus sign is
12875 required. In future versions of @value{GDBN}, the plus or minus
12876 sign will be optional, but you can use it to narrow the search. It
12877 is also possible to specify just a method name:
12883 You must specify the complete method name, including any colons. If
12884 your program's source files contain more than one @code{create} method,
12885 you'll be presented with a numbered list of classes that implement that
12886 method. Indicate your choice by number, or type @samp{0} to exit if
12889 As another example, to clear a breakpoint established at the
12890 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12893 clear -[NSWindow makeKeyAndOrderFront:]
12896 @node The Print Command with Objective-C
12897 @subsubsection The Print Command With Objective-C
12898 @cindex Objective-C, print objects
12899 @kindex print-object
12900 @kindex po @r{(@code{print-object})}
12902 The print command has also been extended to accept methods. For example:
12905 print -[@var{object} hash]
12908 @cindex print an Objective-C object description
12909 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12911 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12912 and print the result. Also, an additional command has been added,
12913 @code{print-object} or @code{po} for short, which is meant to print
12914 the description of an object. However, this command may only work
12915 with certain Objective-C libraries that have a particular hook
12916 function, @code{_NSPrintForDebugger}, defined.
12919 @subsection OpenCL C
12922 This section provides information about @value{GDBN}s OpenCL C support.
12925 * OpenCL C Datatypes::
12926 * OpenCL C Expressions::
12927 * OpenCL C Operators::
12930 @node OpenCL C Datatypes
12931 @subsubsection OpenCL C Datatypes
12933 @cindex OpenCL C Datatypes
12934 @value{GDBN} supports the builtin scalar and vector datatypes specified
12935 by OpenCL 1.1. In addition the half- and double-precision floating point
12936 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12937 extensions are also known to @value{GDBN}.
12939 @node OpenCL C Expressions
12940 @subsubsection OpenCL C Expressions
12942 @cindex OpenCL C Expressions
12943 @value{GDBN} supports accesses to vector components including the access as
12944 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12945 supported by @value{GDBN} can be used as well.
12947 @node OpenCL C Operators
12948 @subsubsection OpenCL C Operators
12950 @cindex OpenCL C Operators
12951 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12955 @subsection Fortran
12956 @cindex Fortran-specific support in @value{GDBN}
12958 @value{GDBN} can be used to debug programs written in Fortran, but it
12959 currently supports only the features of Fortran 77 language.
12961 @cindex trailing underscore, in Fortran symbols
12962 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12963 among them) append an underscore to the names of variables and
12964 functions. When you debug programs compiled by those compilers, you
12965 will need to refer to variables and functions with a trailing
12969 * Fortran Operators:: Fortran operators and expressions
12970 * Fortran Defaults:: Default settings for Fortran
12971 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12974 @node Fortran Operators
12975 @subsubsection Fortran Operators and Expressions
12977 @cindex Fortran operators and expressions
12979 Operators must be defined on values of specific types. For instance,
12980 @code{+} is defined on numbers, but not on characters or other non-
12981 arithmetic types. Operators are often defined on groups of types.
12985 The exponentiation operator. It raises the first operand to the power
12989 The range operator. Normally used in the form of array(low:high) to
12990 represent a section of array.
12993 The access component operator. Normally used to access elements in derived
12994 types. Also suitable for unions. As unions aren't part of regular Fortran,
12995 this can only happen when accessing a register that uses a gdbarch-defined
12999 @node Fortran Defaults
13000 @subsubsection Fortran Defaults
13002 @cindex Fortran Defaults
13004 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13005 default uses case-insensitive matches for Fortran symbols. You can
13006 change that with the @samp{set case-insensitive} command, see
13007 @ref{Symbols}, for the details.
13009 @node Special Fortran Commands
13010 @subsubsection Special Fortran Commands
13012 @cindex Special Fortran commands
13014 @value{GDBN} has some commands to support Fortran-specific features,
13015 such as displaying common blocks.
13018 @cindex @code{COMMON} blocks, Fortran
13019 @kindex info common
13020 @item info common @r{[}@var{common-name}@r{]}
13021 This command prints the values contained in the Fortran @code{COMMON}
13022 block whose name is @var{common-name}. With no argument, the names of
13023 all @code{COMMON} blocks visible at the current program location are
13030 @cindex Pascal support in @value{GDBN}, limitations
13031 Debugging Pascal programs which use sets, subranges, file variables, or
13032 nested functions does not currently work. @value{GDBN} does not support
13033 entering expressions, printing values, or similar features using Pascal
13036 The Pascal-specific command @code{set print pascal_static-members}
13037 controls whether static members of Pascal objects are displayed.
13038 @xref{Print Settings, pascal_static-members}.
13041 @subsection Modula-2
13043 @cindex Modula-2, @value{GDBN} support
13045 The extensions made to @value{GDBN} to support Modula-2 only support
13046 output from the @sc{gnu} Modula-2 compiler (which is currently being
13047 developed). Other Modula-2 compilers are not currently supported, and
13048 attempting to debug executables produced by them is most likely
13049 to give an error as @value{GDBN} reads in the executable's symbol
13052 @cindex expressions in Modula-2
13054 * M2 Operators:: Built-in operators
13055 * Built-In Func/Proc:: Built-in functions and procedures
13056 * M2 Constants:: Modula-2 constants
13057 * M2 Types:: Modula-2 types
13058 * M2 Defaults:: Default settings for Modula-2
13059 * Deviations:: Deviations from standard Modula-2
13060 * M2 Checks:: Modula-2 type and range checks
13061 * M2 Scope:: The scope operators @code{::} and @code{.}
13062 * GDB/M2:: @value{GDBN} and Modula-2
13066 @subsubsection Operators
13067 @cindex Modula-2 operators
13069 Operators must be defined on values of specific types. For instance,
13070 @code{+} is defined on numbers, but not on structures. Operators are
13071 often defined on groups of types. For the purposes of Modula-2, the
13072 following definitions hold:
13077 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13081 @emph{Character types} consist of @code{CHAR} and its subranges.
13084 @emph{Floating-point types} consist of @code{REAL}.
13087 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13091 @emph{Scalar types} consist of all of the above.
13094 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13097 @emph{Boolean types} consist of @code{BOOLEAN}.
13101 The following operators are supported, and appear in order of
13102 increasing precedence:
13106 Function argument or array index separator.
13109 Assignment. The value of @var{var} @code{:=} @var{value} is
13113 Less than, greater than on integral, floating-point, or enumerated
13117 Less than or equal to, greater than or equal to
13118 on integral, floating-point and enumerated types, or set inclusion on
13119 set types. Same precedence as @code{<}.
13121 @item =@r{, }<>@r{, }#
13122 Equality and two ways of expressing inequality, valid on scalar types.
13123 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13124 available for inequality, since @code{#} conflicts with the script
13128 Set membership. Defined on set types and the types of their members.
13129 Same precedence as @code{<}.
13132 Boolean disjunction. Defined on boolean types.
13135 Boolean conjunction. Defined on boolean types.
13138 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13141 Addition and subtraction on integral and floating-point types, or union
13142 and difference on set types.
13145 Multiplication on integral and floating-point types, or set intersection
13149 Division on floating-point types, or symmetric set difference on set
13150 types. Same precedence as @code{*}.
13153 Integer division and remainder. Defined on integral types. Same
13154 precedence as @code{*}.
13157 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13160 Pointer dereferencing. Defined on pointer types.
13163 Boolean negation. Defined on boolean types. Same precedence as
13167 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13168 precedence as @code{^}.
13171 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13174 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13178 @value{GDBN} and Modula-2 scope operators.
13182 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13183 treats the use of the operator @code{IN}, or the use of operators
13184 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13185 @code{<=}, and @code{>=} on sets as an error.
13189 @node Built-In Func/Proc
13190 @subsubsection Built-in Functions and Procedures
13191 @cindex Modula-2 built-ins
13193 Modula-2 also makes available several built-in procedures and functions.
13194 In describing these, the following metavariables are used:
13199 represents an @code{ARRAY} variable.
13202 represents a @code{CHAR} constant or variable.
13205 represents a variable or constant of integral type.
13208 represents an identifier that belongs to a set. Generally used in the
13209 same function with the metavariable @var{s}. The type of @var{s} should
13210 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13213 represents a variable or constant of integral or floating-point type.
13216 represents a variable or constant of floating-point type.
13222 represents a variable.
13225 represents a variable or constant of one of many types. See the
13226 explanation of the function for details.
13229 All Modula-2 built-in procedures also return a result, described below.
13233 Returns the absolute value of @var{n}.
13236 If @var{c} is a lower case letter, it returns its upper case
13237 equivalent, otherwise it returns its argument.
13240 Returns the character whose ordinal value is @var{i}.
13243 Decrements the value in the variable @var{v} by one. Returns the new value.
13245 @item DEC(@var{v},@var{i})
13246 Decrements the value in the variable @var{v} by @var{i}. Returns the
13249 @item EXCL(@var{m},@var{s})
13250 Removes the element @var{m} from the set @var{s}. Returns the new
13253 @item FLOAT(@var{i})
13254 Returns the floating point equivalent of the integer @var{i}.
13256 @item HIGH(@var{a})
13257 Returns the index of the last member of @var{a}.
13260 Increments the value in the variable @var{v} by one. Returns the new value.
13262 @item INC(@var{v},@var{i})
13263 Increments the value in the variable @var{v} by @var{i}. Returns the
13266 @item INCL(@var{m},@var{s})
13267 Adds the element @var{m} to the set @var{s} if it is not already
13268 there. Returns the new set.
13271 Returns the maximum value of the type @var{t}.
13274 Returns the minimum value of the type @var{t}.
13277 Returns boolean TRUE if @var{i} is an odd number.
13280 Returns the ordinal value of its argument. For example, the ordinal
13281 value of a character is its @sc{ascii} value (on machines supporting the
13282 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13283 integral, character and enumerated types.
13285 @item SIZE(@var{x})
13286 Returns the size of its argument. @var{x} can be a variable or a type.
13288 @item TRUNC(@var{r})
13289 Returns the integral part of @var{r}.
13291 @item TSIZE(@var{x})
13292 Returns the size of its argument. @var{x} can be a variable or a type.
13294 @item VAL(@var{t},@var{i})
13295 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13299 @emph{Warning:} Sets and their operations are not yet supported, so
13300 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13304 @cindex Modula-2 constants
13306 @subsubsection Constants
13308 @value{GDBN} allows you to express the constants of Modula-2 in the following
13314 Integer constants are simply a sequence of digits. When used in an
13315 expression, a constant is interpreted to be type-compatible with the
13316 rest of the expression. Hexadecimal integers are specified by a
13317 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13320 Floating point constants appear as a sequence of digits, followed by a
13321 decimal point and another sequence of digits. An optional exponent can
13322 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13323 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13324 digits of the floating point constant must be valid decimal (base 10)
13328 Character constants consist of a single character enclosed by a pair of
13329 like quotes, either single (@code{'}) or double (@code{"}). They may
13330 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13331 followed by a @samp{C}.
13334 String constants consist of a sequence of characters enclosed by a
13335 pair of like quotes, either single (@code{'}) or double (@code{"}).
13336 Escape sequences in the style of C are also allowed. @xref{C
13337 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13341 Enumerated constants consist of an enumerated identifier.
13344 Boolean constants consist of the identifiers @code{TRUE} and
13348 Pointer constants consist of integral values only.
13351 Set constants are not yet supported.
13355 @subsubsection Modula-2 Types
13356 @cindex Modula-2 types
13358 Currently @value{GDBN} can print the following data types in Modula-2
13359 syntax: array types, record types, set types, pointer types, procedure
13360 types, enumerated types, subrange types and base types. You can also
13361 print the contents of variables declared using these type.
13362 This section gives a number of simple source code examples together with
13363 sample @value{GDBN} sessions.
13365 The first example contains the following section of code:
13374 and you can request @value{GDBN} to interrogate the type and value of
13375 @code{r} and @code{s}.
13378 (@value{GDBP}) print s
13380 (@value{GDBP}) ptype s
13382 (@value{GDBP}) print r
13384 (@value{GDBP}) ptype r
13389 Likewise if your source code declares @code{s} as:
13393 s: SET ['A'..'Z'] ;
13397 then you may query the type of @code{s} by:
13400 (@value{GDBP}) ptype s
13401 type = SET ['A'..'Z']
13405 Note that at present you cannot interactively manipulate set
13406 expressions using the debugger.
13408 The following example shows how you might declare an array in Modula-2
13409 and how you can interact with @value{GDBN} to print its type and contents:
13413 s: ARRAY [-10..10] OF CHAR ;
13417 (@value{GDBP}) ptype s
13418 ARRAY [-10..10] OF CHAR
13421 Note that the array handling is not yet complete and although the type
13422 is printed correctly, expression handling still assumes that all
13423 arrays have a lower bound of zero and not @code{-10} as in the example
13426 Here are some more type related Modula-2 examples:
13430 colour = (blue, red, yellow, green) ;
13431 t = [blue..yellow] ;
13439 The @value{GDBN} interaction shows how you can query the data type
13440 and value of a variable.
13443 (@value{GDBP}) print s
13445 (@value{GDBP}) ptype t
13446 type = [blue..yellow]
13450 In this example a Modula-2 array is declared and its contents
13451 displayed. Observe that the contents are written in the same way as
13452 their @code{C} counterparts.
13456 s: ARRAY [1..5] OF CARDINAL ;
13462 (@value{GDBP}) print s
13463 $1 = @{1, 0, 0, 0, 0@}
13464 (@value{GDBP}) ptype s
13465 type = ARRAY [1..5] OF CARDINAL
13468 The Modula-2 language interface to @value{GDBN} also understands
13469 pointer types as shown in this example:
13473 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13480 and you can request that @value{GDBN} describes the type of @code{s}.
13483 (@value{GDBP}) ptype s
13484 type = POINTER TO ARRAY [1..5] OF CARDINAL
13487 @value{GDBN} handles compound types as we can see in this example.
13488 Here we combine array types, record types, pointer types and subrange
13499 myarray = ARRAY myrange OF CARDINAL ;
13500 myrange = [-2..2] ;
13502 s: POINTER TO ARRAY myrange OF foo ;
13506 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13510 (@value{GDBP}) ptype s
13511 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13514 f3 : ARRAY [-2..2] OF CARDINAL;
13519 @subsubsection Modula-2 Defaults
13520 @cindex Modula-2 defaults
13522 If type and range checking are set automatically by @value{GDBN}, they
13523 both default to @code{on} whenever the working language changes to
13524 Modula-2. This happens regardless of whether you or @value{GDBN}
13525 selected the working language.
13527 If you allow @value{GDBN} to set the language automatically, then entering
13528 code compiled from a file whose name ends with @file{.mod} sets the
13529 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13530 Infer the Source Language}, for further details.
13533 @subsubsection Deviations from Standard Modula-2
13534 @cindex Modula-2, deviations from
13536 A few changes have been made to make Modula-2 programs easier to debug.
13537 This is done primarily via loosening its type strictness:
13541 Unlike in standard Modula-2, pointer constants can be formed by
13542 integers. This allows you to modify pointer variables during
13543 debugging. (In standard Modula-2, the actual address contained in a
13544 pointer variable is hidden from you; it can only be modified
13545 through direct assignment to another pointer variable or expression that
13546 returned a pointer.)
13549 C escape sequences can be used in strings and characters to represent
13550 non-printable characters. @value{GDBN} prints out strings with these
13551 escape sequences embedded. Single non-printable characters are
13552 printed using the @samp{CHR(@var{nnn})} format.
13555 The assignment operator (@code{:=}) returns the value of its right-hand
13559 All built-in procedures both modify @emph{and} return their argument.
13563 @subsubsection Modula-2 Type and Range Checks
13564 @cindex Modula-2 checks
13567 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13570 @c FIXME remove warning when type/range checks added
13572 @value{GDBN} considers two Modula-2 variables type equivalent if:
13576 They are of types that have been declared equivalent via a @code{TYPE
13577 @var{t1} = @var{t2}} statement
13580 They have been declared on the same line. (Note: This is true of the
13581 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13584 As long as type checking is enabled, any attempt to combine variables
13585 whose types are not equivalent is an error.
13587 Range checking is done on all mathematical operations, assignment, array
13588 index bounds, and all built-in functions and procedures.
13591 @subsubsection The Scope Operators @code{::} and @code{.}
13593 @cindex @code{.}, Modula-2 scope operator
13594 @cindex colon, doubled as scope operator
13596 @vindex colon-colon@r{, in Modula-2}
13597 @c Info cannot handle :: but TeX can.
13600 @vindex ::@r{, in Modula-2}
13603 There are a few subtle differences between the Modula-2 scope operator
13604 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13609 @var{module} . @var{id}
13610 @var{scope} :: @var{id}
13614 where @var{scope} is the name of a module or a procedure,
13615 @var{module} the name of a module, and @var{id} is any declared
13616 identifier within your program, except another module.
13618 Using the @code{::} operator makes @value{GDBN} search the scope
13619 specified by @var{scope} for the identifier @var{id}. If it is not
13620 found in the specified scope, then @value{GDBN} searches all scopes
13621 enclosing the one specified by @var{scope}.
13623 Using the @code{.} operator makes @value{GDBN} search the current scope for
13624 the identifier specified by @var{id} that was imported from the
13625 definition module specified by @var{module}. With this operator, it is
13626 an error if the identifier @var{id} was not imported from definition
13627 module @var{module}, or if @var{id} is not an identifier in
13631 @subsubsection @value{GDBN} and Modula-2
13633 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13634 Five subcommands of @code{set print} and @code{show print} apply
13635 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13636 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13637 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13638 analogue in Modula-2.
13640 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13641 with any language, is not useful with Modula-2. Its
13642 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13643 created in Modula-2 as they can in C or C@t{++}. However, because an
13644 address can be specified by an integral constant, the construct
13645 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13647 @cindex @code{#} in Modula-2
13648 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13649 interpreted as the beginning of a comment. Use @code{<>} instead.
13655 The extensions made to @value{GDBN} for Ada only support
13656 output from the @sc{gnu} Ada (GNAT) compiler.
13657 Other Ada compilers are not currently supported, and
13658 attempting to debug executables produced by them is most likely
13662 @cindex expressions in Ada
13664 * Ada Mode Intro:: General remarks on the Ada syntax
13665 and semantics supported by Ada mode
13667 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13668 * Additions to Ada:: Extensions of the Ada expression syntax.
13669 * Stopping Before Main Program:: Debugging the program during elaboration.
13670 * Ada Tasks:: Listing and setting breakpoints in tasks.
13671 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13672 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13674 * Ada Glitches:: Known peculiarities of Ada mode.
13677 @node Ada Mode Intro
13678 @subsubsection Introduction
13679 @cindex Ada mode, general
13681 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13682 syntax, with some extensions.
13683 The philosophy behind the design of this subset is
13687 That @value{GDBN} should provide basic literals and access to operations for
13688 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13689 leaving more sophisticated computations to subprograms written into the
13690 program (which therefore may be called from @value{GDBN}).
13693 That type safety and strict adherence to Ada language restrictions
13694 are not particularly important to the @value{GDBN} user.
13697 That brevity is important to the @value{GDBN} user.
13700 Thus, for brevity, the debugger acts as if all names declared in
13701 user-written packages are directly visible, even if they are not visible
13702 according to Ada rules, thus making it unnecessary to fully qualify most
13703 names with their packages, regardless of context. Where this causes
13704 ambiguity, @value{GDBN} asks the user's intent.
13706 The debugger will start in Ada mode if it detects an Ada main program.
13707 As for other languages, it will enter Ada mode when stopped in a program that
13708 was translated from an Ada source file.
13710 While in Ada mode, you may use `@t{--}' for comments. This is useful
13711 mostly for documenting command files. The standard @value{GDBN} comment
13712 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13713 middle (to allow based literals).
13715 The debugger supports limited overloading. Given a subprogram call in which
13716 the function symbol has multiple definitions, it will use the number of
13717 actual parameters and some information about their types to attempt to narrow
13718 the set of definitions. It also makes very limited use of context, preferring
13719 procedures to functions in the context of the @code{call} command, and
13720 functions to procedures elsewhere.
13722 @node Omissions from Ada
13723 @subsubsection Omissions from Ada
13724 @cindex Ada, omissions from
13726 Here are the notable omissions from the subset:
13730 Only a subset of the attributes are supported:
13734 @t{'First}, @t{'Last}, and @t{'Length}
13735 on array objects (not on types and subtypes).
13738 @t{'Min} and @t{'Max}.
13741 @t{'Pos} and @t{'Val}.
13747 @t{'Range} on array objects (not subtypes), but only as the right
13748 operand of the membership (@code{in}) operator.
13751 @t{'Access}, @t{'Unchecked_Access}, and
13752 @t{'Unrestricted_Access} (a GNAT extension).
13760 @code{Characters.Latin_1} are not available and
13761 concatenation is not implemented. Thus, escape characters in strings are
13762 not currently available.
13765 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13766 equality of representations. They will generally work correctly
13767 for strings and arrays whose elements have integer or enumeration types.
13768 They may not work correctly for arrays whose element
13769 types have user-defined equality, for arrays of real values
13770 (in particular, IEEE-conformant floating point, because of negative
13771 zeroes and NaNs), and for arrays whose elements contain unused bits with
13772 indeterminate values.
13775 The other component-by-component array operations (@code{and}, @code{or},
13776 @code{xor}, @code{not}, and relational tests other than equality)
13777 are not implemented.
13780 @cindex array aggregates (Ada)
13781 @cindex record aggregates (Ada)
13782 @cindex aggregates (Ada)
13783 There is limited support for array and record aggregates. They are
13784 permitted only on the right sides of assignments, as in these examples:
13787 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13788 (@value{GDBP}) set An_Array := (1, others => 0)
13789 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13790 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13791 (@value{GDBP}) set A_Record := (1, "Peter", True);
13792 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13796 discriminant's value by assigning an aggregate has an
13797 undefined effect if that discriminant is used within the record.
13798 However, you can first modify discriminants by directly assigning to
13799 them (which normally would not be allowed in Ada), and then performing an
13800 aggregate assignment. For example, given a variable @code{A_Rec}
13801 declared to have a type such as:
13804 type Rec (Len : Small_Integer := 0) is record
13806 Vals : IntArray (1 .. Len);
13810 you can assign a value with a different size of @code{Vals} with two
13814 (@value{GDBP}) set A_Rec.Len := 4
13815 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13818 As this example also illustrates, @value{GDBN} is very loose about the usual
13819 rules concerning aggregates. You may leave out some of the
13820 components of an array or record aggregate (such as the @code{Len}
13821 component in the assignment to @code{A_Rec} above); they will retain their
13822 original values upon assignment. You may freely use dynamic values as
13823 indices in component associations. You may even use overlapping or
13824 redundant component associations, although which component values are
13825 assigned in such cases is not defined.
13828 Calls to dispatching subprograms are not implemented.
13831 The overloading algorithm is much more limited (i.e., less selective)
13832 than that of real Ada. It makes only limited use of the context in
13833 which a subexpression appears to resolve its meaning, and it is much
13834 looser in its rules for allowing type matches. As a result, some
13835 function calls will be ambiguous, and the user will be asked to choose
13836 the proper resolution.
13839 The @code{new} operator is not implemented.
13842 Entry calls are not implemented.
13845 Aside from printing, arithmetic operations on the native VAX floating-point
13846 formats are not supported.
13849 It is not possible to slice a packed array.
13852 The names @code{True} and @code{False}, when not part of a qualified name,
13853 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13855 Should your program
13856 redefine these names in a package or procedure (at best a dubious practice),
13857 you will have to use fully qualified names to access their new definitions.
13860 @node Additions to Ada
13861 @subsubsection Additions to Ada
13862 @cindex Ada, deviations from
13864 As it does for other languages, @value{GDBN} makes certain generic
13865 extensions to Ada (@pxref{Expressions}):
13869 If the expression @var{E} is a variable residing in memory (typically
13870 a local variable or array element) and @var{N} is a positive integer,
13871 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13872 @var{N}-1 adjacent variables following it in memory as an array. In
13873 Ada, this operator is generally not necessary, since its prime use is
13874 in displaying parts of an array, and slicing will usually do this in
13875 Ada. However, there are occasional uses when debugging programs in
13876 which certain debugging information has been optimized away.
13879 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13880 appears in function or file @var{B}.'' When @var{B} is a file name,
13881 you must typically surround it in single quotes.
13884 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13885 @var{type} that appears at address @var{addr}.''
13888 A name starting with @samp{$} is a convenience variable
13889 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13892 In addition, @value{GDBN} provides a few other shortcuts and outright
13893 additions specific to Ada:
13897 The assignment statement is allowed as an expression, returning
13898 its right-hand operand as its value. Thus, you may enter
13901 (@value{GDBP}) set x := y + 3
13902 (@value{GDBP}) print A(tmp := y + 1)
13906 The semicolon is allowed as an ``operator,'' returning as its value
13907 the value of its right-hand operand.
13908 This allows, for example,
13909 complex conditional breaks:
13912 (@value{GDBP}) break f
13913 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13917 Rather than use catenation and symbolic character names to introduce special
13918 characters into strings, one may instead use a special bracket notation,
13919 which is also used to print strings. A sequence of characters of the form
13920 @samp{["@var{XX}"]} within a string or character literal denotes the
13921 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13922 sequence of characters @samp{["""]} also denotes a single quotation mark
13923 in strings. For example,
13925 "One line.["0a"]Next line.["0a"]"
13928 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13932 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13933 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13937 (@value{GDBP}) print 'max(x, y)
13941 When printing arrays, @value{GDBN} uses positional notation when the
13942 array has a lower bound of 1, and uses a modified named notation otherwise.
13943 For example, a one-dimensional array of three integers with a lower bound
13944 of 3 might print as
13951 That is, in contrast to valid Ada, only the first component has a @code{=>}
13955 You may abbreviate attributes in expressions with any unique,
13956 multi-character subsequence of
13957 their names (an exact match gets preference).
13958 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13959 in place of @t{a'length}.
13962 @cindex quoting Ada internal identifiers
13963 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13964 to lower case. The GNAT compiler uses upper-case characters for
13965 some of its internal identifiers, which are normally of no interest to users.
13966 For the rare occasions when you actually have to look at them,
13967 enclose them in angle brackets to avoid the lower-case mapping.
13970 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13974 Printing an object of class-wide type or dereferencing an
13975 access-to-class-wide value will display all the components of the object's
13976 specific type (as indicated by its run-time tag). Likewise, component
13977 selection on such a value will operate on the specific type of the
13982 @node Stopping Before Main Program
13983 @subsubsection Stopping at the Very Beginning
13985 @cindex breakpointing Ada elaboration code
13986 It is sometimes necessary to debug the program during elaboration, and
13987 before reaching the main procedure.
13988 As defined in the Ada Reference
13989 Manual, the elaboration code is invoked from a procedure called
13990 @code{adainit}. To run your program up to the beginning of
13991 elaboration, simply use the following two commands:
13992 @code{tbreak adainit} and @code{run}.
13995 @subsubsection Extensions for Ada Tasks
13996 @cindex Ada, tasking
13998 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13999 @value{GDBN} provides the following task-related commands:
14004 This command shows a list of current Ada tasks, as in the following example:
14011 (@value{GDBP}) info tasks
14012 ID TID P-ID Pri State Name
14013 1 8088000 0 15 Child Activation Wait main_task
14014 2 80a4000 1 15 Accept Statement b
14015 3 809a800 1 15 Child Activation Wait a
14016 * 4 80ae800 3 15 Runnable c
14021 In this listing, the asterisk before the last task indicates it to be the
14022 task currently being inspected.
14026 Represents @value{GDBN}'s internal task number.
14032 The parent's task ID (@value{GDBN}'s internal task number).
14035 The base priority of the task.
14038 Current state of the task.
14042 The task has been created but has not been activated. It cannot be
14046 The task is not blocked for any reason known to Ada. (It may be waiting
14047 for a mutex, though.) It is conceptually "executing" in normal mode.
14050 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14051 that were waiting on terminate alternatives have been awakened and have
14052 terminated themselves.
14054 @item Child Activation Wait
14055 The task is waiting for created tasks to complete activation.
14057 @item Accept Statement
14058 The task is waiting on an accept or selective wait statement.
14060 @item Waiting on entry call
14061 The task is waiting on an entry call.
14063 @item Async Select Wait
14064 The task is waiting to start the abortable part of an asynchronous
14068 The task is waiting on a select statement with only a delay
14071 @item Child Termination Wait
14072 The task is sleeping having completed a master within itself, and is
14073 waiting for the tasks dependent on that master to become terminated or
14074 waiting on a terminate Phase.
14076 @item Wait Child in Term Alt
14077 The task is sleeping waiting for tasks on terminate alternatives to
14078 finish terminating.
14080 @item Accepting RV with @var{taskno}
14081 The task is accepting a rendez-vous with the task @var{taskno}.
14085 Name of the task in the program.
14089 @kindex info task @var{taskno}
14090 @item info task @var{taskno}
14091 This command shows detailled informations on the specified task, as in
14092 the following example:
14097 (@value{GDBP}) info tasks
14098 ID TID P-ID Pri State Name
14099 1 8077880 0 15 Child Activation Wait main_task
14100 * 2 807c468 1 15 Runnable task_1
14101 (@value{GDBP}) info task 2
14102 Ada Task: 0x807c468
14105 Parent: 1 (main_task)
14111 @kindex task@r{ (Ada)}
14112 @cindex current Ada task ID
14113 This command prints the ID of the current task.
14119 (@value{GDBP}) info tasks
14120 ID TID P-ID Pri State Name
14121 1 8077870 0 15 Child Activation Wait main_task
14122 * 2 807c458 1 15 Runnable t
14123 (@value{GDBP}) task
14124 [Current task is 2]
14127 @item task @var{taskno}
14128 @cindex Ada task switching
14129 This command is like the @code{thread @var{threadno}}
14130 command (@pxref{Threads}). It switches the context of debugging
14131 from the current task to the given task.
14137 (@value{GDBP}) info tasks
14138 ID TID P-ID Pri State Name
14139 1 8077870 0 15 Child Activation Wait main_task
14140 * 2 807c458 1 15 Runnable t
14141 (@value{GDBP}) task 1
14142 [Switching to task 1]
14143 #0 0x8067726 in pthread_cond_wait ()
14145 #0 0x8067726 in pthread_cond_wait ()
14146 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14147 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14148 #3 0x806153e in system.tasking.stages.activate_tasks ()
14149 #4 0x804aacc in un () at un.adb:5
14152 @item break @var{linespec} task @var{taskno}
14153 @itemx break @var{linespec} task @var{taskno} if @dots{}
14154 @cindex breakpoints and tasks, in Ada
14155 @cindex task breakpoints, in Ada
14156 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14157 These commands are like the @code{break @dots{} thread @dots{}}
14158 command (@pxref{Thread Stops}).
14159 @var{linespec} specifies source lines, as described
14160 in @ref{Specify Location}.
14162 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14163 to specify that you only want @value{GDBN} to stop the program when a
14164 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14165 numeric task identifiers assigned by @value{GDBN}, shown in the first
14166 column of the @samp{info tasks} display.
14168 If you do not specify @samp{task @var{taskno}} when you set a
14169 breakpoint, the breakpoint applies to @emph{all} tasks of your
14172 You can use the @code{task} qualifier on conditional breakpoints as
14173 well; in this case, place @samp{task @var{taskno}} before the
14174 breakpoint condition (before the @code{if}).
14182 (@value{GDBP}) info tasks
14183 ID TID P-ID Pri State Name
14184 1 140022020 0 15 Child Activation Wait main_task
14185 2 140045060 1 15 Accept/Select Wait t2
14186 3 140044840 1 15 Runnable t1
14187 * 4 140056040 1 15 Runnable t3
14188 (@value{GDBP}) b 15 task 2
14189 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14190 (@value{GDBP}) cont
14195 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14197 (@value{GDBP}) info tasks
14198 ID TID P-ID Pri State Name
14199 1 140022020 0 15 Child Activation Wait main_task
14200 * 2 140045060 1 15 Runnable t2
14201 3 140044840 1 15 Runnable t1
14202 4 140056040 1 15 Delay Sleep t3
14206 @node Ada Tasks and Core Files
14207 @subsubsection Tasking Support when Debugging Core Files
14208 @cindex Ada tasking and core file debugging
14210 When inspecting a core file, as opposed to debugging a live program,
14211 tasking support may be limited or even unavailable, depending on
14212 the platform being used.
14213 For instance, on x86-linux, the list of tasks is available, but task
14214 switching is not supported. On Tru64, however, task switching will work
14217 On certain platforms, including Tru64, the debugger needs to perform some
14218 memory writes in order to provide Ada tasking support. When inspecting
14219 a core file, this means that the core file must be opened with read-write
14220 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14221 Under these circumstances, you should make a backup copy of the core
14222 file before inspecting it with @value{GDBN}.
14224 @node Ravenscar Profile
14225 @subsubsection Tasking Support when using the Ravenscar Profile
14226 @cindex Ravenscar Profile
14228 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14229 specifically designed for systems with safety-critical real-time
14233 @kindex set ravenscar task-switching on
14234 @cindex task switching with program using Ravenscar Profile
14235 @item set ravenscar task-switching on
14236 Allows task switching when debugging a program that uses the Ravenscar
14237 Profile. This is the default.
14239 @kindex set ravenscar task-switching off
14240 @item set ravenscar task-switching off
14241 Turn off task switching when debugging a program that uses the Ravenscar
14242 Profile. This is mostly intended to disable the code that adds support
14243 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14244 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14245 To be effective, this command should be run before the program is started.
14247 @kindex show ravenscar task-switching
14248 @item show ravenscar task-switching
14249 Show whether it is possible to switch from task to task in a program
14250 using the Ravenscar Profile.
14255 @subsubsection Known Peculiarities of Ada Mode
14256 @cindex Ada, problems
14258 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14259 we know of several problems with and limitations of Ada mode in
14261 some of which will be fixed with planned future releases of the debugger
14262 and the GNU Ada compiler.
14266 Static constants that the compiler chooses not to materialize as objects in
14267 storage are invisible to the debugger.
14270 Named parameter associations in function argument lists are ignored (the
14271 argument lists are treated as positional).
14274 Many useful library packages are currently invisible to the debugger.
14277 Fixed-point arithmetic, conversions, input, and output is carried out using
14278 floating-point arithmetic, and may give results that only approximate those on
14282 The GNAT compiler never generates the prefix @code{Standard} for any of
14283 the standard symbols defined by the Ada language. @value{GDBN} knows about
14284 this: it will strip the prefix from names when you use it, and will never
14285 look for a name you have so qualified among local symbols, nor match against
14286 symbols in other packages or subprograms. If you have
14287 defined entities anywhere in your program other than parameters and
14288 local variables whose simple names match names in @code{Standard},
14289 GNAT's lack of qualification here can cause confusion. When this happens,
14290 you can usually resolve the confusion
14291 by qualifying the problematic names with package
14292 @code{Standard} explicitly.
14295 Older versions of the compiler sometimes generate erroneous debugging
14296 information, resulting in the debugger incorrectly printing the value
14297 of affected entities. In some cases, the debugger is able to work
14298 around an issue automatically. In other cases, the debugger is able
14299 to work around the issue, but the work-around has to be specifically
14302 @kindex set ada trust-PAD-over-XVS
14303 @kindex show ada trust-PAD-over-XVS
14306 @item set ada trust-PAD-over-XVS on
14307 Configure GDB to strictly follow the GNAT encoding when computing the
14308 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14309 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14310 a complete description of the encoding used by the GNAT compiler).
14311 This is the default.
14313 @item set ada trust-PAD-over-XVS off
14314 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14315 sometimes prints the wrong value for certain entities, changing @code{ada
14316 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14317 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14318 @code{off}, but this incurs a slight performance penalty, so it is
14319 recommended to leave this setting to @code{on} unless necessary.
14323 @node Unsupported Languages
14324 @section Unsupported Languages
14326 @cindex unsupported languages
14327 @cindex minimal language
14328 In addition to the other fully-supported programming languages,
14329 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14330 It does not represent a real programming language, but provides a set
14331 of capabilities close to what the C or assembly languages provide.
14332 This should allow most simple operations to be performed while debugging
14333 an application that uses a language currently not supported by @value{GDBN}.
14335 If the language is set to @code{auto}, @value{GDBN} will automatically
14336 select this language if the current frame corresponds to an unsupported
14340 @chapter Examining the Symbol Table
14342 The commands described in this chapter allow you to inquire about the
14343 symbols (names of variables, functions and types) defined in your
14344 program. This information is inherent in the text of your program and
14345 does not change as your program executes. @value{GDBN} finds it in your
14346 program's symbol table, in the file indicated when you started @value{GDBN}
14347 (@pxref{File Options, ,Choosing Files}), or by one of the
14348 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14350 @cindex symbol names
14351 @cindex names of symbols
14352 @cindex quoting names
14353 Occasionally, you may need to refer to symbols that contain unusual
14354 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14355 most frequent case is in referring to static variables in other
14356 source files (@pxref{Variables,,Program Variables}). File names
14357 are recorded in object files as debugging symbols, but @value{GDBN} would
14358 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14359 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14360 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14367 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14370 @cindex case-insensitive symbol names
14371 @cindex case sensitivity in symbol names
14372 @kindex set case-sensitive
14373 @item set case-sensitive on
14374 @itemx set case-sensitive off
14375 @itemx set case-sensitive auto
14376 Normally, when @value{GDBN} looks up symbols, it matches their names
14377 with case sensitivity determined by the current source language.
14378 Occasionally, you may wish to control that. The command @code{set
14379 case-sensitive} lets you do that by specifying @code{on} for
14380 case-sensitive matches or @code{off} for case-insensitive ones. If
14381 you specify @code{auto}, case sensitivity is reset to the default
14382 suitable for the source language. The default is case-sensitive
14383 matches for all languages except for Fortran, for which the default is
14384 case-insensitive matches.
14386 @kindex show case-sensitive
14387 @item show case-sensitive
14388 This command shows the current setting of case sensitivity for symbols
14391 @kindex info address
14392 @cindex address of a symbol
14393 @item info address @var{symbol}
14394 Describe where the data for @var{symbol} is stored. For a register
14395 variable, this says which register it is kept in. For a non-register
14396 local variable, this prints the stack-frame offset at which the variable
14399 Note the contrast with @samp{print &@var{symbol}}, which does not work
14400 at all for a register variable, and for a stack local variable prints
14401 the exact address of the current instantiation of the variable.
14403 @kindex info symbol
14404 @cindex symbol from address
14405 @cindex closest symbol and offset for an address
14406 @item info symbol @var{addr}
14407 Print the name of a symbol which is stored at the address @var{addr}.
14408 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14409 nearest symbol and an offset from it:
14412 (@value{GDBP}) info symbol 0x54320
14413 _initialize_vx + 396 in section .text
14417 This is the opposite of the @code{info address} command. You can use
14418 it to find out the name of a variable or a function given its address.
14420 For dynamically linked executables, the name of executable or shared
14421 library containing the symbol is also printed:
14424 (@value{GDBP}) info symbol 0x400225
14425 _start + 5 in section .text of /tmp/a.out
14426 (@value{GDBP}) info symbol 0x2aaaac2811cf
14427 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14431 @item whatis [@var{arg}]
14432 Print the data type of @var{arg}, which can be either an expression
14433 or a name of a data type. With no argument, print the data type of
14434 @code{$}, the last value in the value history.
14436 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14437 is not actually evaluated, and any side-effecting operations (such as
14438 assignments or function calls) inside it do not take place.
14440 If @var{arg} is a variable or an expression, @code{whatis} prints its
14441 literal type as it is used in the source code. If the type was
14442 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14443 the data type underlying the @code{typedef}. If the type of the
14444 variable or the expression is a compound data type, such as
14445 @code{struct} or @code{class}, @code{whatis} never prints their
14446 fields or methods. It just prints the @code{struct}/@code{class}
14447 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14448 such a compound data type, use @code{ptype}.
14450 If @var{arg} is a type name that was defined using @code{typedef},
14451 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14452 Unrolling means that @code{whatis} will show the underlying type used
14453 in the @code{typedef} declaration of @var{arg}. However, if that
14454 underlying type is also a @code{typedef}, @code{whatis} will not
14457 For C code, the type names may also have the form @samp{class
14458 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14459 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14462 @item ptype [@var{arg}]
14463 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14464 detailed description of the type, instead of just the name of the type.
14465 @xref{Expressions, ,Expressions}.
14467 Contrary to @code{whatis}, @code{ptype} always unrolls any
14468 @code{typedef}s in its argument declaration, whether the argument is
14469 a variable, expression, or a data type. This means that @code{ptype}
14470 of a variable or an expression will not print literally its type as
14471 present in the source code---use @code{whatis} for that. @code{typedef}s at
14472 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14473 fields, methods and inner @code{class typedef}s of @code{struct}s,
14474 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14476 For example, for this variable declaration:
14479 typedef double real_t;
14480 struct complex @{ real_t real; double imag; @};
14481 typedef struct complex complex_t;
14483 real_t *real_pointer_var;
14487 the two commands give this output:
14491 (@value{GDBP}) whatis var
14493 (@value{GDBP}) ptype var
14494 type = struct complex @{
14498 (@value{GDBP}) whatis complex_t
14499 type = struct complex
14500 (@value{GDBP}) whatis struct complex
14501 type = struct complex
14502 (@value{GDBP}) ptype struct complex
14503 type = struct complex @{
14507 (@value{GDBP}) whatis real_pointer_var
14509 (@value{GDBP}) ptype real_pointer_var
14515 As with @code{whatis}, using @code{ptype} without an argument refers to
14516 the type of @code{$}, the last value in the value history.
14518 @cindex incomplete type
14519 Sometimes, programs use opaque data types or incomplete specifications
14520 of complex data structure. If the debug information included in the
14521 program does not allow @value{GDBN} to display a full declaration of
14522 the data type, it will say @samp{<incomplete type>}. For example,
14523 given these declarations:
14527 struct foo *fooptr;
14531 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14534 (@value{GDBP}) ptype foo
14535 $1 = <incomplete type>
14539 ``Incomplete type'' is C terminology for data types that are not
14540 completely specified.
14543 @item info types @var{regexp}
14545 Print a brief description of all types whose names match the regular
14546 expression @var{regexp} (or all types in your program, if you supply
14547 no argument). Each complete typename is matched as though it were a
14548 complete line; thus, @samp{i type value} gives information on all
14549 types in your program whose names include the string @code{value}, but
14550 @samp{i type ^value$} gives information only on types whose complete
14551 name is @code{value}.
14553 This command differs from @code{ptype} in two ways: first, like
14554 @code{whatis}, it does not print a detailed description; second, it
14555 lists all source files where a type is defined.
14558 @cindex local variables
14559 @item info scope @var{location}
14560 List all the variables local to a particular scope. This command
14561 accepts a @var{location} argument---a function name, a source line, or
14562 an address preceded by a @samp{*}, and prints all the variables local
14563 to the scope defined by that location. (@xref{Specify Location}, for
14564 details about supported forms of @var{location}.) For example:
14567 (@value{GDBP}) @b{info scope command_line_handler}
14568 Scope for command_line_handler:
14569 Symbol rl is an argument at stack/frame offset 8, length 4.
14570 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14571 Symbol linelength is in static storage at address 0x150a1c, length 4.
14572 Symbol p is a local variable in register $esi, length 4.
14573 Symbol p1 is a local variable in register $ebx, length 4.
14574 Symbol nline is a local variable in register $edx, length 4.
14575 Symbol repeat is a local variable at frame offset -8, length 4.
14579 This command is especially useful for determining what data to collect
14580 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14583 @kindex info source
14585 Show information about the current source file---that is, the source file for
14586 the function containing the current point of execution:
14589 the name of the source file, and the directory containing it,
14591 the directory it was compiled in,
14593 its length, in lines,
14595 which programming language it is written in,
14597 whether the executable includes debugging information for that file, and
14598 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14600 whether the debugging information includes information about
14601 preprocessor macros.
14605 @kindex info sources
14607 Print the names of all source files in your program for which there is
14608 debugging information, organized into two lists: files whose symbols
14609 have already been read, and files whose symbols will be read when needed.
14611 @kindex info functions
14612 @item info functions
14613 Print the names and data types of all defined functions.
14615 @item info functions @var{regexp}
14616 Print the names and data types of all defined functions
14617 whose names contain a match for regular expression @var{regexp}.
14618 Thus, @samp{info fun step} finds all functions whose names
14619 include @code{step}; @samp{info fun ^step} finds those whose names
14620 start with @code{step}. If a function name contains characters
14621 that conflict with the regular expression language (e.g.@:
14622 @samp{operator*()}), they may be quoted with a backslash.
14624 @kindex info variables
14625 @item info variables
14626 Print the names and data types of all variables that are defined
14627 outside of functions (i.e.@: excluding local variables).
14629 @item info variables @var{regexp}
14630 Print the names and data types of all variables (except for local
14631 variables) whose names contain a match for regular expression
14634 @kindex info classes
14635 @cindex Objective-C, classes and selectors
14637 @itemx info classes @var{regexp}
14638 Display all Objective-C classes in your program, or
14639 (with the @var{regexp} argument) all those matching a particular regular
14642 @kindex info selectors
14643 @item info selectors
14644 @itemx info selectors @var{regexp}
14645 Display all Objective-C selectors in your program, or
14646 (with the @var{regexp} argument) all those matching a particular regular
14650 This was never implemented.
14651 @kindex info methods
14653 @itemx info methods @var{regexp}
14654 The @code{info methods} command permits the user to examine all defined
14655 methods within C@t{++} program, or (with the @var{regexp} argument) a
14656 specific set of methods found in the various C@t{++} classes. Many
14657 C@t{++} classes provide a large number of methods. Thus, the output
14658 from the @code{ptype} command can be overwhelming and hard to use. The
14659 @code{info-methods} command filters the methods, printing only those
14660 which match the regular-expression @var{regexp}.
14663 @cindex reloading symbols
14664 Some systems allow individual object files that make up your program to
14665 be replaced without stopping and restarting your program. For example,
14666 in VxWorks you can simply recompile a defective object file and keep on
14667 running. If you are running on one of these systems, you can allow
14668 @value{GDBN} to reload the symbols for automatically relinked modules:
14671 @kindex set symbol-reloading
14672 @item set symbol-reloading on
14673 Replace symbol definitions for the corresponding source file when an
14674 object file with a particular name is seen again.
14676 @item set symbol-reloading off
14677 Do not replace symbol definitions when encountering object files of the
14678 same name more than once. This is the default state; if you are not
14679 running on a system that permits automatic relinking of modules, you
14680 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14681 may discard symbols when linking large programs, that may contain
14682 several modules (from different directories or libraries) with the same
14685 @kindex show symbol-reloading
14686 @item show symbol-reloading
14687 Show the current @code{on} or @code{off} setting.
14690 @cindex opaque data types
14691 @kindex set opaque-type-resolution
14692 @item set opaque-type-resolution on
14693 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14694 declared as a pointer to a @code{struct}, @code{class}, or
14695 @code{union}---for example, @code{struct MyType *}---that is used in one
14696 source file although the full declaration of @code{struct MyType} is in
14697 another source file. The default is on.
14699 A change in the setting of this subcommand will not take effect until
14700 the next time symbols for a file are loaded.
14702 @item set opaque-type-resolution off
14703 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14704 is printed as follows:
14706 @{<no data fields>@}
14709 @kindex show opaque-type-resolution
14710 @item show opaque-type-resolution
14711 Show whether opaque types are resolved or not.
14713 @kindex maint print symbols
14714 @cindex symbol dump
14715 @kindex maint print psymbols
14716 @cindex partial symbol dump
14717 @item maint print symbols @var{filename}
14718 @itemx maint print psymbols @var{filename}
14719 @itemx maint print msymbols @var{filename}
14720 Write a dump of debugging symbol data into the file @var{filename}.
14721 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14722 symbols with debugging data are included. If you use @samp{maint print
14723 symbols}, @value{GDBN} includes all the symbols for which it has already
14724 collected full details: that is, @var{filename} reflects symbols for
14725 only those files whose symbols @value{GDBN} has read. You can use the
14726 command @code{info sources} to find out which files these are. If you
14727 use @samp{maint print psymbols} instead, the dump shows information about
14728 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14729 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14730 @samp{maint print msymbols} dumps just the minimal symbol information
14731 required for each object file from which @value{GDBN} has read some symbols.
14732 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14733 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14735 @kindex maint info symtabs
14736 @kindex maint info psymtabs
14737 @cindex listing @value{GDBN}'s internal symbol tables
14738 @cindex symbol tables, listing @value{GDBN}'s internal
14739 @cindex full symbol tables, listing @value{GDBN}'s internal
14740 @cindex partial symbol tables, listing @value{GDBN}'s internal
14741 @item maint info symtabs @r{[} @var{regexp} @r{]}
14742 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14744 List the @code{struct symtab} or @code{struct partial_symtab}
14745 structures whose names match @var{regexp}. If @var{regexp} is not
14746 given, list them all. The output includes expressions which you can
14747 copy into a @value{GDBN} debugging this one to examine a particular
14748 structure in more detail. For example:
14751 (@value{GDBP}) maint info psymtabs dwarf2read
14752 @{ objfile /home/gnu/build/gdb/gdb
14753 ((struct objfile *) 0x82e69d0)
14754 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14755 ((struct partial_symtab *) 0x8474b10)
14758 text addresses 0x814d3c8 -- 0x8158074
14759 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14760 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14761 dependencies (none)
14764 (@value{GDBP}) maint info symtabs
14768 We see that there is one partial symbol table whose filename contains
14769 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14770 and we see that @value{GDBN} has not read in any symtabs yet at all.
14771 If we set a breakpoint on a function, that will cause @value{GDBN} to
14772 read the symtab for the compilation unit containing that function:
14775 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14776 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14778 (@value{GDBP}) maint info symtabs
14779 @{ objfile /home/gnu/build/gdb/gdb
14780 ((struct objfile *) 0x82e69d0)
14781 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14782 ((struct symtab *) 0x86c1f38)
14785 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14786 linetable ((struct linetable *) 0x8370fa0)
14787 debugformat DWARF 2
14796 @chapter Altering Execution
14798 Once you think you have found an error in your program, you might want to
14799 find out for certain whether correcting the apparent error would lead to
14800 correct results in the rest of the run. You can find the answer by
14801 experiment, using the @value{GDBN} features for altering execution of the
14804 For example, you can store new values into variables or memory
14805 locations, give your program a signal, restart it at a different
14806 address, or even return prematurely from a function.
14809 * Assignment:: Assignment to variables
14810 * Jumping:: Continuing at a different address
14811 * Signaling:: Giving your program a signal
14812 * Returning:: Returning from a function
14813 * Calling:: Calling your program's functions
14814 * Patching:: Patching your program
14818 @section Assignment to Variables
14821 @cindex setting variables
14822 To alter the value of a variable, evaluate an assignment expression.
14823 @xref{Expressions, ,Expressions}. For example,
14830 stores the value 4 into the variable @code{x}, and then prints the
14831 value of the assignment expression (which is 4).
14832 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14833 information on operators in supported languages.
14835 @kindex set variable
14836 @cindex variables, setting
14837 If you are not interested in seeing the value of the assignment, use the
14838 @code{set} command instead of the @code{print} command. @code{set} is
14839 really the same as @code{print} except that the expression's value is
14840 not printed and is not put in the value history (@pxref{Value History,
14841 ,Value History}). The expression is evaluated only for its effects.
14843 If the beginning of the argument string of the @code{set} command
14844 appears identical to a @code{set} subcommand, use the @code{set
14845 variable} command instead of just @code{set}. This command is identical
14846 to @code{set} except for its lack of subcommands. For example, if your
14847 program has a variable @code{width}, you get an error if you try to set
14848 a new value with just @samp{set width=13}, because @value{GDBN} has the
14849 command @code{set width}:
14852 (@value{GDBP}) whatis width
14854 (@value{GDBP}) p width
14856 (@value{GDBP}) set width=47
14857 Invalid syntax in expression.
14861 The invalid expression, of course, is @samp{=47}. In
14862 order to actually set the program's variable @code{width}, use
14865 (@value{GDBP}) set var width=47
14868 Because the @code{set} command has many subcommands that can conflict
14869 with the names of program variables, it is a good idea to use the
14870 @code{set variable} command instead of just @code{set}. For example, if
14871 your program has a variable @code{g}, you run into problems if you try
14872 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14873 the command @code{set gnutarget}, abbreviated @code{set g}:
14877 (@value{GDBP}) whatis g
14881 (@value{GDBP}) set g=4
14885 The program being debugged has been started already.
14886 Start it from the beginning? (y or n) y
14887 Starting program: /home/smith/cc_progs/a.out
14888 "/home/smith/cc_progs/a.out": can't open to read symbols:
14889 Invalid bfd target.
14890 (@value{GDBP}) show g
14891 The current BFD target is "=4".
14896 The program variable @code{g} did not change, and you silently set the
14897 @code{gnutarget} to an invalid value. In order to set the variable
14901 (@value{GDBP}) set var g=4
14904 @value{GDBN} allows more implicit conversions in assignments than C; you can
14905 freely store an integer value into a pointer variable or vice versa,
14906 and you can convert any structure to any other structure that is the
14907 same length or shorter.
14908 @comment FIXME: how do structs align/pad in these conversions?
14909 @comment /doc@cygnus.com 18dec1990
14911 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14912 construct to generate a value of specified type at a specified address
14913 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14914 to memory location @code{0x83040} as an integer (which implies a certain size
14915 and representation in memory), and
14918 set @{int@}0x83040 = 4
14922 stores the value 4 into that memory location.
14925 @section Continuing at a Different Address
14927 Ordinarily, when you continue your program, you do so at the place where
14928 it stopped, with the @code{continue} command. You can instead continue at
14929 an address of your own choosing, with the following commands:
14933 @item jump @var{linespec}
14934 @itemx jump @var{location}
14935 Resume execution at line @var{linespec} or at address given by
14936 @var{location}. Execution stops again immediately if there is a
14937 breakpoint there. @xref{Specify Location}, for a description of the
14938 different forms of @var{linespec} and @var{location}. It is common
14939 practice to use the @code{tbreak} command in conjunction with
14940 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14942 The @code{jump} command does not change the current stack frame, or
14943 the stack pointer, or the contents of any memory location or any
14944 register other than the program counter. If line @var{linespec} is in
14945 a different function from the one currently executing, the results may
14946 be bizarre if the two functions expect different patterns of arguments or
14947 of local variables. For this reason, the @code{jump} command requests
14948 confirmation if the specified line is not in the function currently
14949 executing. However, even bizarre results are predictable if you are
14950 well acquainted with the machine-language code of your program.
14953 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14954 On many systems, you can get much the same effect as the @code{jump}
14955 command by storing a new value into the register @code{$pc}. The
14956 difference is that this does not start your program running; it only
14957 changes the address of where it @emph{will} run when you continue. For
14965 makes the next @code{continue} command or stepping command execute at
14966 address @code{0x485}, rather than at the address where your program stopped.
14967 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14969 The most common occasion to use the @code{jump} command is to back
14970 up---perhaps with more breakpoints set---over a portion of a program
14971 that has already executed, in order to examine its execution in more
14976 @section Giving your Program a Signal
14977 @cindex deliver a signal to a program
14981 @item signal @var{signal}
14982 Resume execution where your program stopped, but immediately give it the
14983 signal @var{signal}. @var{signal} can be the name or the number of a
14984 signal. For example, on many systems @code{signal 2} and @code{signal
14985 SIGINT} are both ways of sending an interrupt signal.
14987 Alternatively, if @var{signal} is zero, continue execution without
14988 giving a signal. This is useful when your program stopped on account of
14989 a signal and would ordinary see the signal when resumed with the
14990 @code{continue} command; @samp{signal 0} causes it to resume without a
14993 @code{signal} does not repeat when you press @key{RET} a second time
14994 after executing the command.
14998 Invoking the @code{signal} command is not the same as invoking the
14999 @code{kill} utility from the shell. Sending a signal with @code{kill}
15000 causes @value{GDBN} to decide what to do with the signal depending on
15001 the signal handling tables (@pxref{Signals}). The @code{signal} command
15002 passes the signal directly to your program.
15006 @section Returning from a Function
15009 @cindex returning from a function
15012 @itemx return @var{expression}
15013 You can cancel execution of a function call with the @code{return}
15014 command. If you give an
15015 @var{expression} argument, its value is used as the function's return
15019 When you use @code{return}, @value{GDBN} discards the selected stack frame
15020 (and all frames within it). You can think of this as making the
15021 discarded frame return prematurely. If you wish to specify a value to
15022 be returned, give that value as the argument to @code{return}.
15024 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15025 Frame}), and any other frames inside of it, leaving its caller as the
15026 innermost remaining frame. That frame becomes selected. The
15027 specified value is stored in the registers used for returning values
15030 The @code{return} command does not resume execution; it leaves the
15031 program stopped in the state that would exist if the function had just
15032 returned. In contrast, the @code{finish} command (@pxref{Continuing
15033 and Stepping, ,Continuing and Stepping}) resumes execution until the
15034 selected stack frame returns naturally.
15036 @value{GDBN} needs to know how the @var{expression} argument should be set for
15037 the inferior. The concrete registers assignment depends on the OS ABI and the
15038 type being returned by the selected stack frame. For example it is common for
15039 OS ABI to return floating point values in FPU registers while integer values in
15040 CPU registers. Still some ABIs return even floating point values in CPU
15041 registers. Larger integer widths (such as @code{long long int}) also have
15042 specific placement rules. @value{GDBN} already knows the OS ABI from its
15043 current target so it needs to find out also the type being returned to make the
15044 assignment into the right register(s).
15046 Normally, the selected stack frame has debug info. @value{GDBN} will always
15047 use the debug info instead of the implicit type of @var{expression} when the
15048 debug info is available. For example, if you type @kbd{return -1}, and the
15049 function in the current stack frame is declared to return a @code{long long
15050 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15051 into a @code{long long int}:
15054 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15056 (@value{GDBP}) return -1
15057 Make func return now? (y or n) y
15058 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15059 43 printf ("result=%lld\n", func ());
15063 However, if the selected stack frame does not have a debug info, e.g., if the
15064 function was compiled without debug info, @value{GDBN} has to find out the type
15065 to return from user. Specifying a different type by mistake may set the value
15066 in different inferior registers than the caller code expects. For example,
15067 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15068 of a @code{long long int} result for a debug info less function (on 32-bit
15069 architectures). Therefore the user is required to specify the return type by
15070 an appropriate cast explicitly:
15073 Breakpoint 2, 0x0040050b in func ()
15074 (@value{GDBP}) return -1
15075 Return value type not available for selected stack frame.
15076 Please use an explicit cast of the value to return.
15077 (@value{GDBP}) return (long long int) -1
15078 Make selected stack frame return now? (y or n) y
15079 #0 0x00400526 in main ()
15084 @section Calling Program Functions
15087 @cindex calling functions
15088 @cindex inferior functions, calling
15089 @item print @var{expr}
15090 Evaluate the expression @var{expr} and display the resulting value.
15091 @var{expr} may include calls to functions in the program being
15095 @item call @var{expr}
15096 Evaluate the expression @var{expr} without displaying @code{void}
15099 You can use this variant of the @code{print} command if you want to
15100 execute a function from your program that does not return anything
15101 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15102 with @code{void} returned values that @value{GDBN} will otherwise
15103 print. If the result is not void, it is printed and saved in the
15107 It is possible for the function you call via the @code{print} or
15108 @code{call} command to generate a signal (e.g., if there's a bug in
15109 the function, or if you passed it incorrect arguments). What happens
15110 in that case is controlled by the @code{set unwindonsignal} command.
15112 Similarly, with a C@t{++} program it is possible for the function you
15113 call via the @code{print} or @code{call} command to generate an
15114 exception that is not handled due to the constraints of the dummy
15115 frame. In this case, any exception that is raised in the frame, but has
15116 an out-of-frame exception handler will not be found. GDB builds a
15117 dummy-frame for the inferior function call, and the unwinder cannot
15118 seek for exception handlers outside of this dummy-frame. What happens
15119 in that case is controlled by the
15120 @code{set unwind-on-terminating-exception} command.
15123 @item set unwindonsignal
15124 @kindex set unwindonsignal
15125 @cindex unwind stack in called functions
15126 @cindex call dummy stack unwinding
15127 Set unwinding of the stack if a signal is received while in a function
15128 that @value{GDBN} called in the program being debugged. If set to on,
15129 @value{GDBN} unwinds the stack it created for the call and restores
15130 the context to what it was before the call. If set to off (the
15131 default), @value{GDBN} stops in the frame where the signal was
15134 @item show unwindonsignal
15135 @kindex show unwindonsignal
15136 Show the current setting of stack unwinding in the functions called by
15139 @item set unwind-on-terminating-exception
15140 @kindex set unwind-on-terminating-exception
15141 @cindex unwind stack in called functions with unhandled exceptions
15142 @cindex call dummy stack unwinding on unhandled exception.
15143 Set unwinding of the stack if a C@t{++} exception is raised, but left
15144 unhandled while in a function that @value{GDBN} called in the program being
15145 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15146 it created for the call and restores the context to what it was before
15147 the call. If set to off, @value{GDBN} the exception is delivered to
15148 the default C@t{++} exception handler and the inferior terminated.
15150 @item show unwind-on-terminating-exception
15151 @kindex show unwind-on-terminating-exception
15152 Show the current setting of stack unwinding in the functions called by
15157 @cindex weak alias functions
15158 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15159 for another function. In such case, @value{GDBN} might not pick up
15160 the type information, including the types of the function arguments,
15161 which causes @value{GDBN} to call the inferior function incorrectly.
15162 As a result, the called function will function erroneously and may
15163 even crash. A solution to that is to use the name of the aliased
15167 @section Patching Programs
15169 @cindex patching binaries
15170 @cindex writing into executables
15171 @cindex writing into corefiles
15173 By default, @value{GDBN} opens the file containing your program's
15174 executable code (or the corefile) read-only. This prevents accidental
15175 alterations to machine code; but it also prevents you from intentionally
15176 patching your program's binary.
15178 If you'd like to be able to patch the binary, you can specify that
15179 explicitly with the @code{set write} command. For example, you might
15180 want to turn on internal debugging flags, or even to make emergency
15186 @itemx set write off
15187 If you specify @samp{set write on}, @value{GDBN} opens executable and
15188 core files for both reading and writing; if you specify @kbd{set write
15189 off} (the default), @value{GDBN} opens them read-only.
15191 If you have already loaded a file, you must load it again (using the
15192 @code{exec-file} or @code{core-file} command) after changing @code{set
15193 write}, for your new setting to take effect.
15197 Display whether executable files and core files are opened for writing
15198 as well as reading.
15202 @chapter @value{GDBN} Files
15204 @value{GDBN} needs to know the file name of the program to be debugged,
15205 both in order to read its symbol table and in order to start your
15206 program. To debug a core dump of a previous run, you must also tell
15207 @value{GDBN} the name of the core dump file.
15210 * Files:: Commands to specify files
15211 * Separate Debug Files:: Debugging information in separate files
15212 * Index Files:: Index files speed up GDB
15213 * Symbol Errors:: Errors reading symbol files
15214 * Data Files:: GDB data files
15218 @section Commands to Specify Files
15220 @cindex symbol table
15221 @cindex core dump file
15223 You may want to specify executable and core dump file names. The usual
15224 way to do this is at start-up time, using the arguments to
15225 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15226 Out of @value{GDBN}}).
15228 Occasionally it is necessary to change to a different file during a
15229 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15230 specify a file you want to use. Or you are debugging a remote target
15231 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15232 Program}). In these situations the @value{GDBN} commands to specify
15233 new files are useful.
15236 @cindex executable file
15238 @item file @var{filename}
15239 Use @var{filename} as the program to be debugged. It is read for its
15240 symbols and for the contents of pure memory. It is also the program
15241 executed when you use the @code{run} command. If you do not specify a
15242 directory and the file is not found in the @value{GDBN} working directory,
15243 @value{GDBN} uses the environment variable @code{PATH} as a list of
15244 directories to search, just as the shell does when looking for a program
15245 to run. You can change the value of this variable, for both @value{GDBN}
15246 and your program, using the @code{path} command.
15248 @cindex unlinked object files
15249 @cindex patching object files
15250 You can load unlinked object @file{.o} files into @value{GDBN} using
15251 the @code{file} command. You will not be able to ``run'' an object
15252 file, but you can disassemble functions and inspect variables. Also,
15253 if the underlying BFD functionality supports it, you could use
15254 @kbd{gdb -write} to patch object files using this technique. Note
15255 that @value{GDBN} can neither interpret nor modify relocations in this
15256 case, so branches and some initialized variables will appear to go to
15257 the wrong place. But this feature is still handy from time to time.
15260 @code{file} with no argument makes @value{GDBN} discard any information it
15261 has on both executable file and the symbol table.
15264 @item exec-file @r{[} @var{filename} @r{]}
15265 Specify that the program to be run (but not the symbol table) is found
15266 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15267 if necessary to locate your program. Omitting @var{filename} means to
15268 discard information on the executable file.
15270 @kindex symbol-file
15271 @item symbol-file @r{[} @var{filename} @r{]}
15272 Read symbol table information from file @var{filename}. @code{PATH} is
15273 searched when necessary. Use the @code{file} command to get both symbol
15274 table and program to run from the same file.
15276 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15277 program's symbol table.
15279 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15280 some breakpoints and auto-display expressions. This is because they may
15281 contain pointers to the internal data recording symbols and data types,
15282 which are part of the old symbol table data being discarded inside
15285 @code{symbol-file} does not repeat if you press @key{RET} again after
15288 When @value{GDBN} is configured for a particular environment, it
15289 understands debugging information in whatever format is the standard
15290 generated for that environment; you may use either a @sc{gnu} compiler, or
15291 other compilers that adhere to the local conventions.
15292 Best results are usually obtained from @sc{gnu} compilers; for example,
15293 using @code{@value{NGCC}} you can generate debugging information for
15296 For most kinds of object files, with the exception of old SVR3 systems
15297 using COFF, the @code{symbol-file} command does not normally read the
15298 symbol table in full right away. Instead, it scans the symbol table
15299 quickly to find which source files and which symbols are present. The
15300 details are read later, one source file at a time, as they are needed.
15302 The purpose of this two-stage reading strategy is to make @value{GDBN}
15303 start up faster. For the most part, it is invisible except for
15304 occasional pauses while the symbol table details for a particular source
15305 file are being read. (The @code{set verbose} command can turn these
15306 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15307 Warnings and Messages}.)
15309 We have not implemented the two-stage strategy for COFF yet. When the
15310 symbol table is stored in COFF format, @code{symbol-file} reads the
15311 symbol table data in full right away. Note that ``stabs-in-COFF''
15312 still does the two-stage strategy, since the debug info is actually
15316 @cindex reading symbols immediately
15317 @cindex symbols, reading immediately
15318 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15319 @itemx file @r{[} -readnow @r{]} @var{filename}
15320 You can override the @value{GDBN} two-stage strategy for reading symbol
15321 tables by using the @samp{-readnow} option with any of the commands that
15322 load symbol table information, if you want to be sure @value{GDBN} has the
15323 entire symbol table available.
15325 @c FIXME: for now no mention of directories, since this seems to be in
15326 @c flux. 13mar1992 status is that in theory GDB would look either in
15327 @c current dir or in same dir as myprog; but issues like competing
15328 @c GDB's, or clutter in system dirs, mean that in practice right now
15329 @c only current dir is used. FFish says maybe a special GDB hierarchy
15330 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15334 @item core-file @r{[}@var{filename}@r{]}
15336 Specify the whereabouts of a core dump file to be used as the ``contents
15337 of memory''. Traditionally, core files contain only some parts of the
15338 address space of the process that generated them; @value{GDBN} can access the
15339 executable file itself for other parts.
15341 @code{core-file} with no argument specifies that no core file is
15344 Note that the core file is ignored when your program is actually running
15345 under @value{GDBN}. So, if you have been running your program and you
15346 wish to debug a core file instead, you must kill the subprocess in which
15347 the program is running. To do this, use the @code{kill} command
15348 (@pxref{Kill Process, ,Killing the Child Process}).
15350 @kindex add-symbol-file
15351 @cindex dynamic linking
15352 @item add-symbol-file @var{filename} @var{address}
15353 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15354 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15355 The @code{add-symbol-file} command reads additional symbol table
15356 information from the file @var{filename}. You would use this command
15357 when @var{filename} has been dynamically loaded (by some other means)
15358 into the program that is running. @var{address} should be the memory
15359 address at which the file has been loaded; @value{GDBN} cannot figure
15360 this out for itself. You can additionally specify an arbitrary number
15361 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15362 section name and base address for that section. You can specify any
15363 @var{address} as an expression.
15365 The symbol table of the file @var{filename} is added to the symbol table
15366 originally read with the @code{symbol-file} command. You can use the
15367 @code{add-symbol-file} command any number of times; the new symbol data
15368 thus read keeps adding to the old. To discard all old symbol data
15369 instead, use the @code{symbol-file} command without any arguments.
15371 @cindex relocatable object files, reading symbols from
15372 @cindex object files, relocatable, reading symbols from
15373 @cindex reading symbols from relocatable object files
15374 @cindex symbols, reading from relocatable object files
15375 @cindex @file{.o} files, reading symbols from
15376 Although @var{filename} is typically a shared library file, an
15377 executable file, or some other object file which has been fully
15378 relocated for loading into a process, you can also load symbolic
15379 information from relocatable @file{.o} files, as long as:
15383 the file's symbolic information refers only to linker symbols defined in
15384 that file, not to symbols defined by other object files,
15386 every section the file's symbolic information refers to has actually
15387 been loaded into the inferior, as it appears in the file, and
15389 you can determine the address at which every section was loaded, and
15390 provide these to the @code{add-symbol-file} command.
15394 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15395 relocatable files into an already running program; such systems
15396 typically make the requirements above easy to meet. However, it's
15397 important to recognize that many native systems use complex link
15398 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15399 assembly, for example) that make the requirements difficult to meet. In
15400 general, one cannot assume that using @code{add-symbol-file} to read a
15401 relocatable object file's symbolic information will have the same effect
15402 as linking the relocatable object file into the program in the normal
15405 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15407 @kindex add-symbol-file-from-memory
15408 @cindex @code{syscall DSO}
15409 @cindex load symbols from memory
15410 @item add-symbol-file-from-memory @var{address}
15411 Load symbols from the given @var{address} in a dynamically loaded
15412 object file whose image is mapped directly into the inferior's memory.
15413 For example, the Linux kernel maps a @code{syscall DSO} into each
15414 process's address space; this DSO provides kernel-specific code for
15415 some system calls. The argument can be any expression whose
15416 evaluation yields the address of the file's shared object file header.
15417 For this command to work, you must have used @code{symbol-file} or
15418 @code{exec-file} commands in advance.
15420 @kindex add-shared-symbol-files
15422 @item add-shared-symbol-files @var{library-file}
15423 @itemx assf @var{library-file}
15424 The @code{add-shared-symbol-files} command can currently be used only
15425 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15426 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15427 @value{GDBN} automatically looks for shared libraries, however if
15428 @value{GDBN} does not find yours, you can invoke
15429 @code{add-shared-symbol-files}. It takes one argument: the shared
15430 library's file name. @code{assf} is a shorthand alias for
15431 @code{add-shared-symbol-files}.
15434 @item section @var{section} @var{addr}
15435 The @code{section} command changes the base address of the named
15436 @var{section} of the exec file to @var{addr}. This can be used if the
15437 exec file does not contain section addresses, (such as in the
15438 @code{a.out} format), or when the addresses specified in the file
15439 itself are wrong. Each section must be changed separately. The
15440 @code{info files} command, described below, lists all the sections and
15444 @kindex info target
15447 @code{info files} and @code{info target} are synonymous; both print the
15448 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15449 including the names of the executable and core dump files currently in
15450 use by @value{GDBN}, and the files from which symbols were loaded. The
15451 command @code{help target} lists all possible targets rather than
15454 @kindex maint info sections
15455 @item maint info sections
15456 Another command that can give you extra information about program sections
15457 is @code{maint info sections}. In addition to the section information
15458 displayed by @code{info files}, this command displays the flags and file
15459 offset of each section in the executable and core dump files. In addition,
15460 @code{maint info sections} provides the following command options (which
15461 may be arbitrarily combined):
15465 Display sections for all loaded object files, including shared libraries.
15466 @item @var{sections}
15467 Display info only for named @var{sections}.
15468 @item @var{section-flags}
15469 Display info only for sections for which @var{section-flags} are true.
15470 The section flags that @value{GDBN} currently knows about are:
15473 Section will have space allocated in the process when loaded.
15474 Set for all sections except those containing debug information.
15476 Section will be loaded from the file into the child process memory.
15477 Set for pre-initialized code and data, clear for @code{.bss} sections.
15479 Section needs to be relocated before loading.
15481 Section cannot be modified by the child process.
15483 Section contains executable code only.
15485 Section contains data only (no executable code).
15487 Section will reside in ROM.
15489 Section contains data for constructor/destructor lists.
15491 Section is not empty.
15493 An instruction to the linker to not output the section.
15494 @item COFF_SHARED_LIBRARY
15495 A notification to the linker that the section contains
15496 COFF shared library information.
15498 Section contains common symbols.
15501 @kindex set trust-readonly-sections
15502 @cindex read-only sections
15503 @item set trust-readonly-sections on
15504 Tell @value{GDBN} that readonly sections in your object file
15505 really are read-only (i.e.@: that their contents will not change).
15506 In that case, @value{GDBN} can fetch values from these sections
15507 out of the object file, rather than from the target program.
15508 For some targets (notably embedded ones), this can be a significant
15509 enhancement to debugging performance.
15511 The default is off.
15513 @item set trust-readonly-sections off
15514 Tell @value{GDBN} not to trust readonly sections. This means that
15515 the contents of the section might change while the program is running,
15516 and must therefore be fetched from the target when needed.
15518 @item show trust-readonly-sections
15519 Show the current setting of trusting readonly sections.
15522 All file-specifying commands allow both absolute and relative file names
15523 as arguments. @value{GDBN} always converts the file name to an absolute file
15524 name and remembers it that way.
15526 @cindex shared libraries
15527 @anchor{Shared Libraries}
15528 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15529 and IBM RS/6000 AIX shared libraries.
15531 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15532 shared libraries. @xref{Expat}.
15534 @value{GDBN} automatically loads symbol definitions from shared libraries
15535 when you use the @code{run} command, or when you examine a core file.
15536 (Before you issue the @code{run} command, @value{GDBN} does not understand
15537 references to a function in a shared library, however---unless you are
15538 debugging a core file).
15540 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15541 automatically loads the symbols at the time of the @code{shl_load} call.
15543 @c FIXME: some @value{GDBN} release may permit some refs to undef
15544 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15545 @c FIXME...lib; check this from time to time when updating manual
15547 There are times, however, when you may wish to not automatically load
15548 symbol definitions from shared libraries, such as when they are
15549 particularly large or there are many of them.
15551 To control the automatic loading of shared library symbols, use the
15555 @kindex set auto-solib-add
15556 @item set auto-solib-add @var{mode}
15557 If @var{mode} is @code{on}, symbols from all shared object libraries
15558 will be loaded automatically when the inferior begins execution, you
15559 attach to an independently started inferior, or when the dynamic linker
15560 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15561 is @code{off}, symbols must be loaded manually, using the
15562 @code{sharedlibrary} command. The default value is @code{on}.
15564 @cindex memory used for symbol tables
15565 If your program uses lots of shared libraries with debug info that
15566 takes large amounts of memory, you can decrease the @value{GDBN}
15567 memory footprint by preventing it from automatically loading the
15568 symbols from shared libraries. To that end, type @kbd{set
15569 auto-solib-add off} before running the inferior, then load each
15570 library whose debug symbols you do need with @kbd{sharedlibrary
15571 @var{regexp}}, where @var{regexp} is a regular expression that matches
15572 the libraries whose symbols you want to be loaded.
15574 @kindex show auto-solib-add
15575 @item show auto-solib-add
15576 Display the current autoloading mode.
15579 @cindex load shared library
15580 To explicitly load shared library symbols, use the @code{sharedlibrary}
15584 @kindex info sharedlibrary
15586 @item info share @var{regex}
15587 @itemx info sharedlibrary @var{regex}
15588 Print the names of the shared libraries which are currently loaded
15589 that match @var{regex}. If @var{regex} is omitted then print
15590 all shared libraries that are loaded.
15592 @kindex sharedlibrary
15594 @item sharedlibrary @var{regex}
15595 @itemx share @var{regex}
15596 Load shared object library symbols for files matching a
15597 Unix regular expression.
15598 As with files loaded automatically, it only loads shared libraries
15599 required by your program for a core file or after typing @code{run}. If
15600 @var{regex} is omitted all shared libraries required by your program are
15603 @item nosharedlibrary
15604 @kindex nosharedlibrary
15605 @cindex unload symbols from shared libraries
15606 Unload all shared object library symbols. This discards all symbols
15607 that have been loaded from all shared libraries. Symbols from shared
15608 libraries that were loaded by explicit user requests are not
15612 Sometimes you may wish that @value{GDBN} stops and gives you control
15613 when any of shared library events happen. The best way to do this is
15614 to use @code{catch load} and @code{catch unload} (@pxref{Set
15617 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15618 command for this. This command exists for historical reasons. It is
15619 less useful than setting a catchpoint, because it does not allow for
15620 conditions or commands as a catchpoint does.
15623 @item set stop-on-solib-events
15624 @kindex set stop-on-solib-events
15625 This command controls whether @value{GDBN} should give you control
15626 when the dynamic linker notifies it about some shared library event.
15627 The most common event of interest is loading or unloading of a new
15630 @item show stop-on-solib-events
15631 @kindex show stop-on-solib-events
15632 Show whether @value{GDBN} stops and gives you control when shared
15633 library events happen.
15636 Shared libraries are also supported in many cross or remote debugging
15637 configurations. @value{GDBN} needs to have access to the target's libraries;
15638 this can be accomplished either by providing copies of the libraries
15639 on the host system, or by asking @value{GDBN} to automatically retrieve the
15640 libraries from the target. If copies of the target libraries are
15641 provided, they need to be the same as the target libraries, although the
15642 copies on the target can be stripped as long as the copies on the host are
15645 @cindex where to look for shared libraries
15646 For remote debugging, you need to tell @value{GDBN} where the target
15647 libraries are, so that it can load the correct copies---otherwise, it
15648 may try to load the host's libraries. @value{GDBN} has two variables
15649 to specify the search directories for target libraries.
15652 @cindex prefix for shared library file names
15653 @cindex system root, alternate
15654 @kindex set solib-absolute-prefix
15655 @kindex set sysroot
15656 @item set sysroot @var{path}
15657 Use @var{path} as the system root for the program being debugged. Any
15658 absolute shared library paths will be prefixed with @var{path}; many
15659 runtime loaders store the absolute paths to the shared library in the
15660 target program's memory. If you use @code{set sysroot} to find shared
15661 libraries, they need to be laid out in the same way that they are on
15662 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15665 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15666 retrieve the target libraries from the remote system. This is only
15667 supported when using a remote target that supports the @code{remote get}
15668 command (@pxref{File Transfer,,Sending files to a remote system}).
15669 The part of @var{path} following the initial @file{remote:}
15670 (if present) is used as system root prefix on the remote file system.
15671 @footnote{If you want to specify a local system root using a directory
15672 that happens to be named @file{remote:}, you need to use some equivalent
15673 variant of the name like @file{./remote:}.}
15675 For targets with an MS-DOS based filesystem, such as MS-Windows and
15676 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15677 absolute file name with @var{path}. But first, on Unix hosts,
15678 @value{GDBN} converts all backslash directory separators into forward
15679 slashes, because the backslash is not a directory separator on Unix:
15682 c:\foo\bar.dll @result{} c:/foo/bar.dll
15685 Then, @value{GDBN} attempts prefixing the target file name with
15686 @var{path}, and looks for the resulting file name in the host file
15690 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15693 If that does not find the shared library, @value{GDBN} tries removing
15694 the @samp{:} character from the drive spec, both for convenience, and,
15695 for the case of the host file system not supporting file names with
15699 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15702 This makes it possible to have a system root that mirrors a target
15703 with more than one drive. E.g., you may want to setup your local
15704 copies of the target system shared libraries like so (note @samp{c} vs
15708 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15709 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15710 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15714 and point the system root at @file{/path/to/sysroot}, so that
15715 @value{GDBN} can find the correct copies of both
15716 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15718 If that still does not find the shared library, @value{GDBN} tries
15719 removing the whole drive spec from the target file name:
15722 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15725 This last lookup makes it possible to not care about the drive name,
15726 if you don't want or need to.
15728 The @code{set solib-absolute-prefix} command is an alias for @code{set
15731 @cindex default system root
15732 @cindex @samp{--with-sysroot}
15733 You can set the default system root by using the configure-time
15734 @samp{--with-sysroot} option. If the system root is inside
15735 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15736 @samp{--exec-prefix}), then the default system root will be updated
15737 automatically if the installed @value{GDBN} is moved to a new
15740 @kindex show sysroot
15742 Display the current shared library prefix.
15744 @kindex set solib-search-path
15745 @item set solib-search-path @var{path}
15746 If this variable is set, @var{path} is a colon-separated list of
15747 directories to search for shared libraries. @samp{solib-search-path}
15748 is used after @samp{sysroot} fails to locate the library, or if the
15749 path to the library is relative instead of absolute. If you want to
15750 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15751 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15752 finding your host's libraries. @samp{sysroot} is preferred; setting
15753 it to a nonexistent directory may interfere with automatic loading
15754 of shared library symbols.
15756 @kindex show solib-search-path
15757 @item show solib-search-path
15758 Display the current shared library search path.
15760 @cindex DOS file-name semantics of file names.
15761 @kindex set target-file-system-kind (unix|dos-based|auto)
15762 @kindex show target-file-system-kind
15763 @item set target-file-system-kind @var{kind}
15764 Set assumed file system kind for target reported file names.
15766 Shared library file names as reported by the target system may not
15767 make sense as is on the system @value{GDBN} is running on. For
15768 example, when remote debugging a target that has MS-DOS based file
15769 system semantics, from a Unix host, the target may be reporting to
15770 @value{GDBN} a list of loaded shared libraries with file names such as
15771 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15772 drive letters, so the @samp{c:\} prefix is not normally understood as
15773 indicating an absolute file name, and neither is the backslash
15774 normally considered a directory separator character. In that case,
15775 the native file system would interpret this whole absolute file name
15776 as a relative file name with no directory components. This would make
15777 it impossible to point @value{GDBN} at a copy of the remote target's
15778 shared libraries on the host using @code{set sysroot}, and impractical
15779 with @code{set solib-search-path}. Setting
15780 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15781 to interpret such file names similarly to how the target would, and to
15782 map them to file names valid on @value{GDBN}'s native file system
15783 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15784 to one of the supported file system kinds. In that case, @value{GDBN}
15785 tries to determine the appropriate file system variant based on the
15786 current target's operating system (@pxref{ABI, ,Configuring the
15787 Current ABI}). The supported file system settings are:
15791 Instruct @value{GDBN} to assume the target file system is of Unix
15792 kind. Only file names starting the forward slash (@samp{/}) character
15793 are considered absolute, and the directory separator character is also
15797 Instruct @value{GDBN} to assume the target file system is DOS based.
15798 File names starting with either a forward slash, or a drive letter
15799 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15800 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15801 considered directory separators.
15804 Instruct @value{GDBN} to use the file system kind associated with the
15805 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15806 This is the default.
15810 @cindex file name canonicalization
15811 @cindex base name differences
15812 When processing file names provided by the user, @value{GDBN}
15813 frequently needs to compare them to the file names recorded in the
15814 program's debug info. Normally, @value{GDBN} compares just the
15815 @dfn{base names} of the files as strings, which is reasonably fast
15816 even for very large programs. (The base name of a file is the last
15817 portion of its name, after stripping all the leading directories.)
15818 This shortcut in comparison is based upon the assumption that files
15819 cannot have more than one base name. This is usually true, but
15820 references to files that use symlinks or similar filesystem
15821 facilities violate that assumption. If your program records files
15822 using such facilities, or if you provide file names to @value{GDBN}
15823 using symlinks etc., you can set @code{basenames-may-differ} to
15824 @code{true} to instruct @value{GDBN} to completely canonicalize each
15825 pair of file names it needs to compare. This will make file-name
15826 comparisons accurate, but at a price of a significant slowdown.
15829 @item set basenames-may-differ
15830 @kindex set basenames-may-differ
15831 Set whether a source file may have multiple base names.
15833 @item show basenames-may-differ
15834 @kindex show basenames-may-differ
15835 Show whether a source file may have multiple base names.
15838 @node Separate Debug Files
15839 @section Debugging Information in Separate Files
15840 @cindex separate debugging information files
15841 @cindex debugging information in separate files
15842 @cindex @file{.debug} subdirectories
15843 @cindex debugging information directory, global
15844 @cindex global debugging information directory
15845 @cindex build ID, and separate debugging files
15846 @cindex @file{.build-id} directory
15848 @value{GDBN} allows you to put a program's debugging information in a
15849 file separate from the executable itself, in a way that allows
15850 @value{GDBN} to find and load the debugging information automatically.
15851 Since debugging information can be very large---sometimes larger
15852 than the executable code itself---some systems distribute debugging
15853 information for their executables in separate files, which users can
15854 install only when they need to debug a problem.
15856 @value{GDBN} supports two ways of specifying the separate debug info
15861 The executable contains a @dfn{debug link} that specifies the name of
15862 the separate debug info file. The separate debug file's name is
15863 usually @file{@var{executable}.debug}, where @var{executable} is the
15864 name of the corresponding executable file without leading directories
15865 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15866 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15867 checksum for the debug file, which @value{GDBN} uses to validate that
15868 the executable and the debug file came from the same build.
15871 The executable contains a @dfn{build ID}, a unique bit string that is
15872 also present in the corresponding debug info file. (This is supported
15873 only on some operating systems, notably those which use the ELF format
15874 for binary files and the @sc{gnu} Binutils.) For more details about
15875 this feature, see the description of the @option{--build-id}
15876 command-line option in @ref{Options, , Command Line Options, ld.info,
15877 The GNU Linker}. The debug info file's name is not specified
15878 explicitly by the build ID, but can be computed from the build ID, see
15882 Depending on the way the debug info file is specified, @value{GDBN}
15883 uses two different methods of looking for the debug file:
15887 For the ``debug link'' method, @value{GDBN} looks up the named file in
15888 the directory of the executable file, then in a subdirectory of that
15889 directory named @file{.debug}, and finally under the global debug
15890 directory, in a subdirectory whose name is identical to the leading
15891 directories of the executable's absolute file name.
15894 For the ``build ID'' method, @value{GDBN} looks in the
15895 @file{.build-id} subdirectory of the global debug directory for a file
15896 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15897 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15898 are the rest of the bit string. (Real build ID strings are 32 or more
15899 hex characters, not 10.)
15902 So, for example, suppose you ask @value{GDBN} to debug
15903 @file{/usr/bin/ls}, which has a debug link that specifies the
15904 file @file{ls.debug}, and a build ID whose value in hex is
15905 @code{abcdef1234}. If the global debug directory is
15906 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15907 debug information files, in the indicated order:
15911 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15913 @file{/usr/bin/ls.debug}
15915 @file{/usr/bin/.debug/ls.debug}
15917 @file{/usr/lib/debug/usr/bin/ls.debug}.
15920 You can set the global debugging info directory's name, and view the
15921 name @value{GDBN} is currently using.
15925 @kindex set debug-file-directory
15926 @item set debug-file-directory @var{directories}
15927 Set the directories which @value{GDBN} searches for separate debugging
15928 information files to @var{directory}. Multiple directory components can be set
15929 concatenating them by a directory separator.
15931 @kindex show debug-file-directory
15932 @item show debug-file-directory
15933 Show the directories @value{GDBN} searches for separate debugging
15938 @cindex @code{.gnu_debuglink} sections
15939 @cindex debug link sections
15940 A debug link is a special section of the executable file named
15941 @code{.gnu_debuglink}. The section must contain:
15945 A filename, with any leading directory components removed, followed by
15948 zero to three bytes of padding, as needed to reach the next four-byte
15949 boundary within the section, and
15951 a four-byte CRC checksum, stored in the same endianness used for the
15952 executable file itself. The checksum is computed on the debugging
15953 information file's full contents by the function given below, passing
15954 zero as the @var{crc} argument.
15957 Any executable file format can carry a debug link, as long as it can
15958 contain a section named @code{.gnu_debuglink} with the contents
15961 @cindex @code{.note.gnu.build-id} sections
15962 @cindex build ID sections
15963 The build ID is a special section in the executable file (and in other
15964 ELF binary files that @value{GDBN} may consider). This section is
15965 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15966 It contains unique identification for the built files---the ID remains
15967 the same across multiple builds of the same build tree. The default
15968 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15969 content for the build ID string. The same section with an identical
15970 value is present in the original built binary with symbols, in its
15971 stripped variant, and in the separate debugging information file.
15973 The debugging information file itself should be an ordinary
15974 executable, containing a full set of linker symbols, sections, and
15975 debugging information. The sections of the debugging information file
15976 should have the same names, addresses, and sizes as the original file,
15977 but they need not contain any data---much like a @code{.bss} section
15978 in an ordinary executable.
15980 The @sc{gnu} binary utilities (Binutils) package includes the
15981 @samp{objcopy} utility that can produce
15982 the separated executable / debugging information file pairs using the
15983 following commands:
15986 @kbd{objcopy --only-keep-debug foo foo.debug}
15991 These commands remove the debugging
15992 information from the executable file @file{foo} and place it in the file
15993 @file{foo.debug}. You can use the first, second or both methods to link the
15998 The debug link method needs the following additional command to also leave
15999 behind a debug link in @file{foo}:
16002 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16005 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16006 a version of the @code{strip} command such that the command @kbd{strip foo -f
16007 foo.debug} has the same functionality as the two @code{objcopy} commands and
16008 the @code{ln -s} command above, together.
16011 Build ID gets embedded into the main executable using @code{ld --build-id} or
16012 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16013 compatibility fixes for debug files separation are present in @sc{gnu} binary
16014 utilities (Binutils) package since version 2.18.
16019 @cindex CRC algorithm definition
16020 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16021 IEEE 802.3 using the polynomial:
16023 @c TexInfo requires naked braces for multi-digit exponents for Tex
16024 @c output, but this causes HTML output to barf. HTML has to be set using
16025 @c raw commands. So we end up having to specify this equation in 2
16030 <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>
16031 + <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
16037 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16038 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16042 The function is computed byte at a time, taking the least
16043 significant bit of each byte first. The initial pattern
16044 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16045 the final result is inverted to ensure trailing zeros also affect the
16048 @emph{Note:} This is the same CRC polynomial as used in handling the
16049 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16050 , @value{GDBN} Remote Serial Protocol}). However in the
16051 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16052 significant bit first, and the result is not inverted, so trailing
16053 zeros have no effect on the CRC value.
16055 To complete the description, we show below the code of the function
16056 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16057 initially supplied @code{crc} argument means that an initial call to
16058 this function passing in zero will start computing the CRC using
16061 @kindex gnu_debuglink_crc32
16064 gnu_debuglink_crc32 (unsigned long crc,
16065 unsigned char *buf, size_t len)
16067 static const unsigned long crc32_table[256] =
16069 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16070 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16071 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16072 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16073 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16074 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16075 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16076 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16077 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16078 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16079 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16080 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16081 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16082 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16083 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16084 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16085 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16086 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16087 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16088 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16089 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16090 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16091 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16092 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16093 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16094 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16095 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16096 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16097 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16098 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16099 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16100 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16101 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16102 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16103 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16104 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16105 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16106 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16107 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16108 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16109 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16110 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16111 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16112 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16113 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16114 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16115 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16116 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16117 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16118 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16119 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16122 unsigned char *end;
16124 crc = ~crc & 0xffffffff;
16125 for (end = buf + len; buf < end; ++buf)
16126 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16127 return ~crc & 0xffffffff;
16132 This computation does not apply to the ``build ID'' method.
16136 @section Index Files Speed Up @value{GDBN}
16137 @cindex index files
16138 @cindex @samp{.gdb_index} section
16140 When @value{GDBN} finds a symbol file, it scans the symbols in the
16141 file in order to construct an internal symbol table. This lets most
16142 @value{GDBN} operations work quickly---at the cost of a delay early
16143 on. For large programs, this delay can be quite lengthy, so
16144 @value{GDBN} provides a way to build an index, which speeds up
16147 The index is stored as a section in the symbol file. @value{GDBN} can
16148 write the index to a file, then you can put it into the symbol file
16149 using @command{objcopy}.
16151 To create an index file, use the @code{save gdb-index} command:
16154 @item save gdb-index @var{directory}
16155 @kindex save gdb-index
16156 Create an index file for each symbol file currently known by
16157 @value{GDBN}. Each file is named after its corresponding symbol file,
16158 with @samp{.gdb-index} appended, and is written into the given
16162 Once you have created an index file you can merge it into your symbol
16163 file, here named @file{symfile}, using @command{objcopy}:
16166 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16167 --set-section-flags .gdb_index=readonly symfile symfile
16170 There are currently some limitation on indices. They only work when
16171 for DWARF debugging information, not stabs. And, they do not
16172 currently work for programs using Ada.
16174 @node Symbol Errors
16175 @section Errors Reading Symbol Files
16177 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16178 such as symbol types it does not recognize, or known bugs in compiler
16179 output. By default, @value{GDBN} does not notify you of such problems, since
16180 they are relatively common and primarily of interest to people
16181 debugging compilers. If you are interested in seeing information
16182 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16183 only one message about each such type of problem, no matter how many
16184 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16185 to see how many times the problems occur, with the @code{set
16186 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16189 The messages currently printed, and their meanings, include:
16192 @item inner block not inside outer block in @var{symbol}
16194 The symbol information shows where symbol scopes begin and end
16195 (such as at the start of a function or a block of statements). This
16196 error indicates that an inner scope block is not fully contained
16197 in its outer scope blocks.
16199 @value{GDBN} circumvents the problem by treating the inner block as if it had
16200 the same scope as the outer block. In the error message, @var{symbol}
16201 may be shown as ``@code{(don't know)}'' if the outer block is not a
16204 @item block at @var{address} out of order
16206 The symbol information for symbol scope blocks should occur in
16207 order of increasing addresses. This error indicates that it does not
16210 @value{GDBN} does not circumvent this problem, and has trouble
16211 locating symbols in the source file whose symbols it is reading. (You
16212 can often determine what source file is affected by specifying
16213 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16216 @item bad block start address patched
16218 The symbol information for a symbol scope block has a start address
16219 smaller than the address of the preceding source line. This is known
16220 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16222 @value{GDBN} circumvents the problem by treating the symbol scope block as
16223 starting on the previous source line.
16225 @item bad string table offset in symbol @var{n}
16228 Symbol number @var{n} contains a pointer into the string table which is
16229 larger than the size of the string table.
16231 @value{GDBN} circumvents the problem by considering the symbol to have the
16232 name @code{foo}, which may cause other problems if many symbols end up
16235 @item unknown symbol type @code{0x@var{nn}}
16237 The symbol information contains new data types that @value{GDBN} does
16238 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16239 uncomprehended information, in hexadecimal.
16241 @value{GDBN} circumvents the error by ignoring this symbol information.
16242 This usually allows you to debug your program, though certain symbols
16243 are not accessible. If you encounter such a problem and feel like
16244 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16245 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16246 and examine @code{*bufp} to see the symbol.
16248 @item stub type has NULL name
16250 @value{GDBN} could not find the full definition for a struct or class.
16252 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16253 The symbol information for a C@t{++} member function is missing some
16254 information that recent versions of the compiler should have output for
16257 @item info mismatch between compiler and debugger
16259 @value{GDBN} could not parse a type specification output by the compiler.
16264 @section GDB Data Files
16266 @cindex prefix for data files
16267 @value{GDBN} will sometimes read an auxiliary data file. These files
16268 are kept in a directory known as the @dfn{data directory}.
16270 You can set the data directory's name, and view the name @value{GDBN}
16271 is currently using.
16274 @kindex set data-directory
16275 @item set data-directory @var{directory}
16276 Set the directory which @value{GDBN} searches for auxiliary data files
16277 to @var{directory}.
16279 @kindex show data-directory
16280 @item show data-directory
16281 Show the directory @value{GDBN} searches for auxiliary data files.
16284 @cindex default data directory
16285 @cindex @samp{--with-gdb-datadir}
16286 You can set the default data directory by using the configure-time
16287 @samp{--with-gdb-datadir} option. If the data directory is inside
16288 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16289 @samp{--exec-prefix}), then the default data directory will be updated
16290 automatically if the installed @value{GDBN} is moved to a new
16293 The data directory may also be specified with the
16294 @code{--data-directory} command line option.
16295 @xref{Mode Options}.
16298 @chapter Specifying a Debugging Target
16300 @cindex debugging target
16301 A @dfn{target} is the execution environment occupied by your program.
16303 Often, @value{GDBN} runs in the same host environment as your program;
16304 in that case, the debugging target is specified as a side effect when
16305 you use the @code{file} or @code{core} commands. When you need more
16306 flexibility---for example, running @value{GDBN} on a physically separate
16307 host, or controlling a standalone system over a serial port or a
16308 realtime system over a TCP/IP connection---you can use the @code{target}
16309 command to specify one of the target types configured for @value{GDBN}
16310 (@pxref{Target Commands, ,Commands for Managing Targets}).
16312 @cindex target architecture
16313 It is possible to build @value{GDBN} for several different @dfn{target
16314 architectures}. When @value{GDBN} is built like that, you can choose
16315 one of the available architectures with the @kbd{set architecture}
16319 @kindex set architecture
16320 @kindex show architecture
16321 @item set architecture @var{arch}
16322 This command sets the current target architecture to @var{arch}. The
16323 value of @var{arch} can be @code{"auto"}, in addition to one of the
16324 supported architectures.
16326 @item show architecture
16327 Show the current target architecture.
16329 @item set processor
16331 @kindex set processor
16332 @kindex show processor
16333 These are alias commands for, respectively, @code{set architecture}
16334 and @code{show architecture}.
16338 * Active Targets:: Active targets
16339 * Target Commands:: Commands for managing targets
16340 * Byte Order:: Choosing target byte order
16343 @node Active Targets
16344 @section Active Targets
16346 @cindex stacking targets
16347 @cindex active targets
16348 @cindex multiple targets
16350 There are multiple classes of targets such as: processes, executable files or
16351 recording sessions. Core files belong to the process class, making core file
16352 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16353 on multiple active targets, one in each class. This allows you to (for
16354 example) start a process and inspect its activity, while still having access to
16355 the executable file after the process finishes. Or if you start process
16356 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16357 presented a virtual layer of the recording target, while the process target
16358 remains stopped at the chronologically last point of the process execution.
16360 Use the @code{core-file} and @code{exec-file} commands to select a new core
16361 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16362 specify as a target a process that is already running, use the @code{attach}
16363 command (@pxref{Attach, ,Debugging an Already-running Process}).
16365 @node Target Commands
16366 @section Commands for Managing Targets
16369 @item target @var{type} @var{parameters}
16370 Connects the @value{GDBN} host environment to a target machine or
16371 process. A target is typically a protocol for talking to debugging
16372 facilities. You use the argument @var{type} to specify the type or
16373 protocol of the target machine.
16375 Further @var{parameters} are interpreted by the target protocol, but
16376 typically include things like device names or host names to connect
16377 with, process numbers, and baud rates.
16379 The @code{target} command does not repeat if you press @key{RET} again
16380 after executing the command.
16382 @kindex help target
16384 Displays the names of all targets available. To display targets
16385 currently selected, use either @code{info target} or @code{info files}
16386 (@pxref{Files, ,Commands to Specify Files}).
16388 @item help target @var{name}
16389 Describe a particular target, including any parameters necessary to
16392 @kindex set gnutarget
16393 @item set gnutarget @var{args}
16394 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16395 knows whether it is reading an @dfn{executable},
16396 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16397 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16398 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16401 @emph{Warning:} To specify a file format with @code{set gnutarget},
16402 you must know the actual BFD name.
16406 @xref{Files, , Commands to Specify Files}.
16408 @kindex show gnutarget
16409 @item show gnutarget
16410 Use the @code{show gnutarget} command to display what file format
16411 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16412 @value{GDBN} will determine the file format for each file automatically,
16413 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16416 @cindex common targets
16417 Here are some common targets (available, or not, depending on the GDB
16422 @item target exec @var{program}
16423 @cindex executable file target
16424 An executable file. @samp{target exec @var{program}} is the same as
16425 @samp{exec-file @var{program}}.
16427 @item target core @var{filename}
16428 @cindex core dump file target
16429 A core dump file. @samp{target core @var{filename}} is the same as
16430 @samp{core-file @var{filename}}.
16432 @item target remote @var{medium}
16433 @cindex remote target
16434 A remote system connected to @value{GDBN} via a serial line or network
16435 connection. This command tells @value{GDBN} to use its own remote
16436 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16438 For example, if you have a board connected to @file{/dev/ttya} on the
16439 machine running @value{GDBN}, you could say:
16442 target remote /dev/ttya
16445 @code{target remote} supports the @code{load} command. This is only
16446 useful if you have some other way of getting the stub to the target
16447 system, and you can put it somewhere in memory where it won't get
16448 clobbered by the download.
16450 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16451 @cindex built-in simulator target
16452 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16460 works; however, you cannot assume that a specific memory map, device
16461 drivers, or even basic I/O is available, although some simulators do
16462 provide these. For info about any processor-specific simulator details,
16463 see the appropriate section in @ref{Embedded Processors, ,Embedded
16468 Some configurations may include these targets as well:
16472 @item target nrom @var{dev}
16473 @cindex NetROM ROM emulator target
16474 NetROM ROM emulator. This target only supports downloading.
16478 Different targets are available on different configurations of @value{GDBN};
16479 your configuration may have more or fewer targets.
16481 Many remote targets require you to download the executable's code once
16482 you've successfully established a connection. You may wish to control
16483 various aspects of this process.
16488 @kindex set hash@r{, for remote monitors}
16489 @cindex hash mark while downloading
16490 This command controls whether a hash mark @samp{#} is displayed while
16491 downloading a file to the remote monitor. If on, a hash mark is
16492 displayed after each S-record is successfully downloaded to the
16496 @kindex show hash@r{, for remote monitors}
16497 Show the current status of displaying the hash mark.
16499 @item set debug monitor
16500 @kindex set debug monitor
16501 @cindex display remote monitor communications
16502 Enable or disable display of communications messages between
16503 @value{GDBN} and the remote monitor.
16505 @item show debug monitor
16506 @kindex show debug monitor
16507 Show the current status of displaying communications between
16508 @value{GDBN} and the remote monitor.
16513 @kindex load @var{filename}
16514 @item load @var{filename}
16516 Depending on what remote debugging facilities are configured into
16517 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16518 is meant to make @var{filename} (an executable) available for debugging
16519 on the remote system---by downloading, or dynamic linking, for example.
16520 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16521 the @code{add-symbol-file} command.
16523 If your @value{GDBN} does not have a @code{load} command, attempting to
16524 execute it gets the error message ``@code{You can't do that when your
16525 target is @dots{}}''
16527 The file is loaded at whatever address is specified in the executable.
16528 For some object file formats, you can specify the load address when you
16529 link the program; for other formats, like a.out, the object file format
16530 specifies a fixed address.
16531 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16533 Depending on the remote side capabilities, @value{GDBN} may be able to
16534 load programs into flash memory.
16536 @code{load} does not repeat if you press @key{RET} again after using it.
16540 @section Choosing Target Byte Order
16542 @cindex choosing target byte order
16543 @cindex target byte order
16545 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16546 offer the ability to run either big-endian or little-endian byte
16547 orders. Usually the executable or symbol will include a bit to
16548 designate the endian-ness, and you will not need to worry about
16549 which to use. However, you may still find it useful to adjust
16550 @value{GDBN}'s idea of processor endian-ness manually.
16554 @item set endian big
16555 Instruct @value{GDBN} to assume the target is big-endian.
16557 @item set endian little
16558 Instruct @value{GDBN} to assume the target is little-endian.
16560 @item set endian auto
16561 Instruct @value{GDBN} to use the byte order associated with the
16565 Display @value{GDBN}'s current idea of the target byte order.
16569 Note that these commands merely adjust interpretation of symbolic
16570 data on the host, and that they have absolutely no effect on the
16574 @node Remote Debugging
16575 @chapter Debugging Remote Programs
16576 @cindex remote debugging
16578 If you are trying to debug a program running on a machine that cannot run
16579 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16580 For example, you might use remote debugging on an operating system kernel,
16581 or on a small system which does not have a general purpose operating system
16582 powerful enough to run a full-featured debugger.
16584 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16585 to make this work with particular debugging targets. In addition,
16586 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16587 but not specific to any particular target system) which you can use if you
16588 write the remote stubs---the code that runs on the remote system to
16589 communicate with @value{GDBN}.
16591 Other remote targets may be available in your
16592 configuration of @value{GDBN}; use @code{help target} to list them.
16595 * Connecting:: Connecting to a remote target
16596 * File Transfer:: Sending files to a remote system
16597 * Server:: Using the gdbserver program
16598 * Remote Configuration:: Remote configuration
16599 * Remote Stub:: Implementing a remote stub
16603 @section Connecting to a Remote Target
16605 On the @value{GDBN} host machine, you will need an unstripped copy of
16606 your program, since @value{GDBN} needs symbol and debugging information.
16607 Start up @value{GDBN} as usual, using the name of the local copy of your
16608 program as the first argument.
16610 @cindex @code{target remote}
16611 @value{GDBN} can communicate with the target over a serial line, or
16612 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16613 each case, @value{GDBN} uses the same protocol for debugging your
16614 program; only the medium carrying the debugging packets varies. The
16615 @code{target remote} command establishes a connection to the target.
16616 Its arguments indicate which medium to use:
16620 @item target remote @var{serial-device}
16621 @cindex serial line, @code{target remote}
16622 Use @var{serial-device} to communicate with the target. For example,
16623 to use a serial line connected to the device named @file{/dev/ttyb}:
16626 target remote /dev/ttyb
16629 If you're using a serial line, you may want to give @value{GDBN} the
16630 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16631 (@pxref{Remote Configuration, set remotebaud}) before the
16632 @code{target} command.
16634 @item target remote @code{@var{host}:@var{port}}
16635 @itemx target remote @code{tcp:@var{host}:@var{port}}
16636 @cindex @acronym{TCP} port, @code{target remote}
16637 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16638 The @var{host} may be either a host name or a numeric @acronym{IP}
16639 address; @var{port} must be a decimal number. The @var{host} could be
16640 the target machine itself, if it is directly connected to the net, or
16641 it might be a terminal server which in turn has a serial line to the
16644 For example, to connect to port 2828 on a terminal server named
16648 target remote manyfarms:2828
16651 If your remote target is actually running on the same machine as your
16652 debugger session (e.g.@: a simulator for your target running on the
16653 same host), you can omit the hostname. For example, to connect to
16654 port 1234 on your local machine:
16657 target remote :1234
16661 Note that the colon is still required here.
16663 @item target remote @code{udp:@var{host}:@var{port}}
16664 @cindex @acronym{UDP} port, @code{target remote}
16665 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16666 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16669 target remote udp:manyfarms:2828
16672 When using a @acronym{UDP} connection for remote debugging, you should
16673 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16674 can silently drop packets on busy or unreliable networks, which will
16675 cause havoc with your debugging session.
16677 @item target remote | @var{command}
16678 @cindex pipe, @code{target remote} to
16679 Run @var{command} in the background and communicate with it using a
16680 pipe. The @var{command} is a shell command, to be parsed and expanded
16681 by the system's command shell, @code{/bin/sh}; it should expect remote
16682 protocol packets on its standard input, and send replies on its
16683 standard output. You could use this to run a stand-alone simulator
16684 that speaks the remote debugging protocol, to make net connections
16685 using programs like @code{ssh}, or for other similar tricks.
16687 If @var{command} closes its standard output (perhaps by exiting),
16688 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16689 program has already exited, this will have no effect.)
16693 Once the connection has been established, you can use all the usual
16694 commands to examine and change data. The remote program is already
16695 running; you can use @kbd{step} and @kbd{continue}, and you do not
16696 need to use @kbd{run}.
16698 @cindex interrupting remote programs
16699 @cindex remote programs, interrupting
16700 Whenever @value{GDBN} is waiting for the remote program, if you type the
16701 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16702 program. This may or may not succeed, depending in part on the hardware
16703 and the serial drivers the remote system uses. If you type the
16704 interrupt character once again, @value{GDBN} displays this prompt:
16707 Interrupted while waiting for the program.
16708 Give up (and stop debugging it)? (y or n)
16711 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16712 (If you decide you want to try again later, you can use @samp{target
16713 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16714 goes back to waiting.
16717 @kindex detach (remote)
16719 When you have finished debugging the remote program, you can use the
16720 @code{detach} command to release it from @value{GDBN} control.
16721 Detaching from the target normally resumes its execution, but the results
16722 will depend on your particular remote stub. After the @code{detach}
16723 command, @value{GDBN} is free to connect to another target.
16727 The @code{disconnect} command behaves like @code{detach}, except that
16728 the target is generally not resumed. It will wait for @value{GDBN}
16729 (this instance or another one) to connect and continue debugging. After
16730 the @code{disconnect} command, @value{GDBN} is again free to connect to
16733 @cindex send command to remote monitor
16734 @cindex extend @value{GDBN} for remote targets
16735 @cindex add new commands for external monitor
16737 @item monitor @var{cmd}
16738 This command allows you to send arbitrary commands directly to the
16739 remote monitor. Since @value{GDBN} doesn't care about the commands it
16740 sends like this, this command is the way to extend @value{GDBN}---you
16741 can add new commands that only the external monitor will understand
16745 @node File Transfer
16746 @section Sending files to a remote system
16747 @cindex remote target, file transfer
16748 @cindex file transfer
16749 @cindex sending files to remote systems
16751 Some remote targets offer the ability to transfer files over the same
16752 connection used to communicate with @value{GDBN}. This is convenient
16753 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16754 running @code{gdbserver} over a network interface. For other targets,
16755 e.g.@: embedded devices with only a single serial port, this may be
16756 the only way to upload or download files.
16758 Not all remote targets support these commands.
16762 @item remote put @var{hostfile} @var{targetfile}
16763 Copy file @var{hostfile} from the host system (the machine running
16764 @value{GDBN}) to @var{targetfile} on the target system.
16767 @item remote get @var{targetfile} @var{hostfile}
16768 Copy file @var{targetfile} from the target system to @var{hostfile}
16769 on the host system.
16771 @kindex remote delete
16772 @item remote delete @var{targetfile}
16773 Delete @var{targetfile} from the target system.
16778 @section Using the @code{gdbserver} Program
16781 @cindex remote connection without stubs
16782 @code{gdbserver} is a control program for Unix-like systems, which
16783 allows you to connect your program with a remote @value{GDBN} via
16784 @code{target remote}---but without linking in the usual debugging stub.
16786 @code{gdbserver} is not a complete replacement for the debugging stubs,
16787 because it requires essentially the same operating-system facilities
16788 that @value{GDBN} itself does. In fact, a system that can run
16789 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16790 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16791 because it is a much smaller program than @value{GDBN} itself. It is
16792 also easier to port than all of @value{GDBN}, so you may be able to get
16793 started more quickly on a new system by using @code{gdbserver}.
16794 Finally, if you develop code for real-time systems, you may find that
16795 the tradeoffs involved in real-time operation make it more convenient to
16796 do as much development work as possible on another system, for example
16797 by cross-compiling. You can use @code{gdbserver} to make a similar
16798 choice for debugging.
16800 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16801 or a TCP connection, using the standard @value{GDBN} remote serial
16805 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16806 Do not run @code{gdbserver} connected to any public network; a
16807 @value{GDBN} connection to @code{gdbserver} provides access to the
16808 target system with the same privileges as the user running
16812 @subsection Running @code{gdbserver}
16813 @cindex arguments, to @code{gdbserver}
16814 @cindex @code{gdbserver}, command-line arguments
16816 Run @code{gdbserver} on the target system. You need a copy of the
16817 program you want to debug, including any libraries it requires.
16818 @code{gdbserver} does not need your program's symbol table, so you can
16819 strip the program if necessary to save space. @value{GDBN} on the host
16820 system does all the symbol handling.
16822 To use the server, you must tell it how to communicate with @value{GDBN};
16823 the name of your program; and the arguments for your program. The usual
16827 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16830 @var{comm} is either a device name (to use a serial line), or a TCP
16831 hostname and portnumber, or @code{-} or @code{stdio} to use
16832 stdin/stdout of @code{gdbserver}.
16833 For example, to debug Emacs with the argument
16834 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16838 target> gdbserver /dev/com1 emacs foo.txt
16841 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16844 To use a TCP connection instead of a serial line:
16847 target> gdbserver host:2345 emacs foo.txt
16850 The only difference from the previous example is the first argument,
16851 specifying that you are communicating with the host @value{GDBN} via
16852 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16853 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16854 (Currently, the @samp{host} part is ignored.) You can choose any number
16855 you want for the port number as long as it does not conflict with any
16856 TCP ports already in use on the target system (for example, @code{23} is
16857 reserved for @code{telnet}).@footnote{If you choose a port number that
16858 conflicts with another service, @code{gdbserver} prints an error message
16859 and exits.} You must use the same port number with the host @value{GDBN}
16860 @code{target remote} command.
16862 The @code{stdio} connection is useful when starting @code{gdbserver}
16866 (gdb) target remote | ssh -T hostname gdbserver - hello
16869 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16870 and we don't want escape-character handling. Ssh does this by default when
16871 a command is provided, the flag is provided to make it explicit.
16872 You could elide it if you want to.
16874 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16875 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16876 display through a pipe connected to gdbserver.
16877 Both @code{stdout} and @code{stderr} use the same pipe.
16879 @subsubsection Attaching to a Running Program
16880 @cindex attach to a program, @code{gdbserver}
16881 @cindex @option{--attach}, @code{gdbserver} option
16883 On some targets, @code{gdbserver} can also attach to running programs.
16884 This is accomplished via the @code{--attach} argument. The syntax is:
16887 target> gdbserver --attach @var{comm} @var{pid}
16890 @var{pid} is the process ID of a currently running process. It isn't necessary
16891 to point @code{gdbserver} at a binary for the running process.
16894 You can debug processes by name instead of process ID if your target has the
16895 @code{pidof} utility:
16898 target> gdbserver --attach @var{comm} `pidof @var{program}`
16901 In case more than one copy of @var{program} is running, or @var{program}
16902 has multiple threads, most versions of @code{pidof} support the
16903 @code{-s} option to only return the first process ID.
16905 @subsubsection Multi-Process Mode for @code{gdbserver}
16906 @cindex @code{gdbserver}, multiple processes
16907 @cindex multiple processes with @code{gdbserver}
16909 When you connect to @code{gdbserver} using @code{target remote},
16910 @code{gdbserver} debugs the specified program only once. When the
16911 program exits, or you detach from it, @value{GDBN} closes the connection
16912 and @code{gdbserver} exits.
16914 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16915 enters multi-process mode. When the debugged program exits, or you
16916 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16917 though no program is running. The @code{run} and @code{attach}
16918 commands instruct @code{gdbserver} to run or attach to a new program.
16919 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16920 remote exec-file}) to select the program to run. Command line
16921 arguments are supported, except for wildcard expansion and I/O
16922 redirection (@pxref{Arguments}).
16924 @cindex @option{--multi}, @code{gdbserver} option
16925 To start @code{gdbserver} without supplying an initial command to run
16926 or process ID to attach, use the @option{--multi} command line option.
16927 Then you can connect using @kbd{target extended-remote} and start
16928 the program you want to debug.
16930 In multi-process mode @code{gdbserver} does not automatically exit unless you
16931 use the option @option{--once}. You can terminate it by using
16932 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16933 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16934 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16935 @option{--multi} option to @code{gdbserver} has no influence on that.
16937 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16939 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16941 @code{gdbserver} normally terminates after all of its debugged processes have
16942 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16943 extended-remote}, @code{gdbserver} stays running even with no processes left.
16944 @value{GDBN} normally terminates the spawned debugged process on its exit,
16945 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16946 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16947 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16948 stays running even in the @kbd{target remote} mode.
16950 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16951 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16952 completeness, at most one @value{GDBN} can be connected at a time.
16954 @cindex @option{--once}, @code{gdbserver} option
16955 By default, @code{gdbserver} keeps the listening TCP port open, so that
16956 additional connections are possible. However, if you start @code{gdbserver}
16957 with the @option{--once} option, it will stop listening for any further
16958 connection attempts after connecting to the first @value{GDBN} session. This
16959 means no further connections to @code{gdbserver} will be possible after the
16960 first one. It also means @code{gdbserver} will terminate after the first
16961 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16962 connections and even in the @kbd{target extended-remote} mode. The
16963 @option{--once} option allows reusing the same port number for connecting to
16964 multiple instances of @code{gdbserver} running on the same host, since each
16965 instance closes its port after the first connection.
16967 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16969 @cindex @option{--debug}, @code{gdbserver} option
16970 The @option{--debug} option tells @code{gdbserver} to display extra
16971 status information about the debugging process.
16972 @cindex @option{--remote-debug}, @code{gdbserver} option
16973 The @option{--remote-debug} option tells @code{gdbserver} to display
16974 remote protocol debug output. These options are intended for
16975 @code{gdbserver} development and for bug reports to the developers.
16977 @cindex @option{--wrapper}, @code{gdbserver} option
16978 The @option{--wrapper} option specifies a wrapper to launch programs
16979 for debugging. The option should be followed by the name of the
16980 wrapper, then any command-line arguments to pass to the wrapper, then
16981 @kbd{--} indicating the end of the wrapper arguments.
16983 @code{gdbserver} runs the specified wrapper program with a combined
16984 command line including the wrapper arguments, then the name of the
16985 program to debug, then any arguments to the program. The wrapper
16986 runs until it executes your program, and then @value{GDBN} gains control.
16988 You can use any program that eventually calls @code{execve} with
16989 its arguments as a wrapper. Several standard Unix utilities do
16990 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16991 with @code{exec "$@@"} will also work.
16993 For example, you can use @code{env} to pass an environment variable to
16994 the debugged program, without setting the variable in @code{gdbserver}'s
16998 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17001 @subsection Connecting to @code{gdbserver}
17003 Run @value{GDBN} on the host system.
17005 First make sure you have the necessary symbol files. Load symbols for
17006 your application using the @code{file} command before you connect. Use
17007 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17008 was compiled with the correct sysroot using @code{--with-sysroot}).
17010 The symbol file and target libraries must exactly match the executable
17011 and libraries on the target, with one exception: the files on the host
17012 system should not be stripped, even if the files on the target system
17013 are. Mismatched or missing files will lead to confusing results
17014 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17015 files may also prevent @code{gdbserver} from debugging multi-threaded
17018 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17019 For TCP connections, you must start up @code{gdbserver} prior to using
17020 the @code{target remote} command. Otherwise you may get an error whose
17021 text depends on the host system, but which usually looks something like
17022 @samp{Connection refused}. Don't use the @code{load}
17023 command in @value{GDBN} when using @code{gdbserver}, since the program is
17024 already on the target.
17026 @subsection Monitor Commands for @code{gdbserver}
17027 @cindex monitor commands, for @code{gdbserver}
17028 @anchor{Monitor Commands for gdbserver}
17030 During a @value{GDBN} session using @code{gdbserver}, you can use the
17031 @code{monitor} command to send special requests to @code{gdbserver}.
17032 Here are the available commands.
17036 List the available monitor commands.
17038 @item monitor set debug 0
17039 @itemx monitor set debug 1
17040 Disable or enable general debugging messages.
17042 @item monitor set remote-debug 0
17043 @itemx monitor set remote-debug 1
17044 Disable or enable specific debugging messages associated with the remote
17045 protocol (@pxref{Remote Protocol}).
17047 @item monitor set libthread-db-search-path [PATH]
17048 @cindex gdbserver, search path for @code{libthread_db}
17049 When this command is issued, @var{path} is a colon-separated list of
17050 directories to search for @code{libthread_db} (@pxref{Threads,,set
17051 libthread-db-search-path}). If you omit @var{path},
17052 @samp{libthread-db-search-path} will be reset to its default value.
17054 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17055 not supported in @code{gdbserver}.
17058 Tell gdbserver to exit immediately. This command should be followed by
17059 @code{disconnect} to close the debugging session. @code{gdbserver} will
17060 detach from any attached processes and kill any processes it created.
17061 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17062 of a multi-process mode debug session.
17066 @subsection Tracepoints support in @code{gdbserver}
17067 @cindex tracepoints support in @code{gdbserver}
17069 On some targets, @code{gdbserver} supports tracepoints, fast
17070 tracepoints and static tracepoints.
17072 For fast or static tracepoints to work, a special library called the
17073 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17074 This library is built and distributed as an integral part of
17075 @code{gdbserver}. In addition, support for static tracepoints
17076 requires building the in-process agent library with static tracepoints
17077 support. At present, the UST (LTTng Userspace Tracer,
17078 @url{http://lttng.org/ust}) tracing engine is supported. This support
17079 is automatically available if UST development headers are found in the
17080 standard include path when @code{gdbserver} is built, or if
17081 @code{gdbserver} was explicitly configured using @option{--with-ust}
17082 to point at such headers. You can explicitly disable the support
17083 using @option{--with-ust=no}.
17085 There are several ways to load the in-process agent in your program:
17088 @item Specifying it as dependency at link time
17090 You can link your program dynamically with the in-process agent
17091 library. On most systems, this is accomplished by adding
17092 @code{-linproctrace} to the link command.
17094 @item Using the system's preloading mechanisms
17096 You can force loading the in-process agent at startup time by using
17097 your system's support for preloading shared libraries. Many Unixes
17098 support the concept of preloading user defined libraries. In most
17099 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17100 in the environment. See also the description of @code{gdbserver}'s
17101 @option{--wrapper} command line option.
17103 @item Using @value{GDBN} to force loading the agent at run time
17105 On some systems, you can force the inferior to load a shared library,
17106 by calling a dynamic loader function in the inferior that takes care
17107 of dynamically looking up and loading a shared library. On most Unix
17108 systems, the function is @code{dlopen}. You'll use the @code{call}
17109 command for that. For example:
17112 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17115 Note that on most Unix systems, for the @code{dlopen} function to be
17116 available, the program needs to be linked with @code{-ldl}.
17119 On systems that have a userspace dynamic loader, like most Unix
17120 systems, when you connect to @code{gdbserver} using @code{target
17121 remote}, you'll find that the program is stopped at the dynamic
17122 loader's entry point, and no shared library has been loaded in the
17123 program's address space yet, including the in-process agent. In that
17124 case, before being able to use any of the fast or static tracepoints
17125 features, you need to let the loader run and load the shared
17126 libraries. The simplest way to do that is to run the program to the
17127 main procedure. E.g., if debugging a C or C@t{++} program, start
17128 @code{gdbserver} like so:
17131 $ gdbserver :9999 myprogram
17134 Start GDB and connect to @code{gdbserver} like so, and run to main:
17138 (@value{GDBP}) target remote myhost:9999
17139 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17140 (@value{GDBP}) b main
17141 (@value{GDBP}) continue
17144 The in-process tracing agent library should now be loaded into the
17145 process; you can confirm it with the @code{info sharedlibrary}
17146 command, which will list @file{libinproctrace.so} as loaded in the
17147 process. You are now ready to install fast tracepoints, list static
17148 tracepoint markers, probe static tracepoints markers, and start
17151 @node Remote Configuration
17152 @section Remote Configuration
17155 @kindex show remote
17156 This section documents the configuration options available when
17157 debugging remote programs. For the options related to the File I/O
17158 extensions of the remote protocol, see @ref{system,
17159 system-call-allowed}.
17162 @item set remoteaddresssize @var{bits}
17163 @cindex address size for remote targets
17164 @cindex bits in remote address
17165 Set the maximum size of address in a memory packet to the specified
17166 number of bits. @value{GDBN} will mask off the address bits above
17167 that number, when it passes addresses to the remote target. The
17168 default value is the number of bits in the target's address.
17170 @item show remoteaddresssize
17171 Show the current value of remote address size in bits.
17173 @item set remotebaud @var{n}
17174 @cindex baud rate for remote targets
17175 Set the baud rate for the remote serial I/O to @var{n} baud. The
17176 value is used to set the speed of the serial port used for debugging
17179 @item show remotebaud
17180 Show the current speed of the remote connection.
17182 @item set remotebreak
17183 @cindex interrupt remote programs
17184 @cindex BREAK signal instead of Ctrl-C
17185 @anchor{set remotebreak}
17186 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17187 when you type @kbd{Ctrl-c} to interrupt the program running
17188 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17189 character instead. The default is off, since most remote systems
17190 expect to see @samp{Ctrl-C} as the interrupt signal.
17192 @item show remotebreak
17193 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17194 interrupt the remote program.
17196 @item set remoteflow on
17197 @itemx set remoteflow off
17198 @kindex set remoteflow
17199 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17200 on the serial port used to communicate to the remote target.
17202 @item show remoteflow
17203 @kindex show remoteflow
17204 Show the current setting of hardware flow control.
17206 @item set remotelogbase @var{base}
17207 Set the base (a.k.a.@: radix) of logging serial protocol
17208 communications to @var{base}. Supported values of @var{base} are:
17209 @code{ascii}, @code{octal}, and @code{hex}. The default is
17212 @item show remotelogbase
17213 Show the current setting of the radix for logging remote serial
17216 @item set remotelogfile @var{file}
17217 @cindex record serial communications on file
17218 Record remote serial communications on the named @var{file}. The
17219 default is not to record at all.
17221 @item show remotelogfile.
17222 Show the current setting of the file name on which to record the
17223 serial communications.
17225 @item set remotetimeout @var{num}
17226 @cindex timeout for serial communications
17227 @cindex remote timeout
17228 Set the timeout limit to wait for the remote target to respond to
17229 @var{num} seconds. The default is 2 seconds.
17231 @item show remotetimeout
17232 Show the current number of seconds to wait for the remote target
17235 @cindex limit hardware breakpoints and watchpoints
17236 @cindex remote target, limit break- and watchpoints
17237 @anchor{set remote hardware-watchpoint-limit}
17238 @anchor{set remote hardware-breakpoint-limit}
17239 @item set remote hardware-watchpoint-limit @var{limit}
17240 @itemx set remote hardware-breakpoint-limit @var{limit}
17241 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17242 watchpoints. A limit of -1, the default, is treated as unlimited.
17244 @cindex limit hardware watchpoints length
17245 @cindex remote target, limit watchpoints length
17246 @anchor{set remote hardware-watchpoint-length-limit}
17247 @item set remote hardware-watchpoint-length-limit @var{limit}
17248 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17249 a remote hardware watchpoint. A limit of -1, the default, is treated
17252 @item show remote hardware-watchpoint-length-limit
17253 Show the current limit (in bytes) of the maximum length of
17254 a remote hardware watchpoint.
17256 @item set remote exec-file @var{filename}
17257 @itemx show remote exec-file
17258 @anchor{set remote exec-file}
17259 @cindex executable file, for remote target
17260 Select the file used for @code{run} with @code{target
17261 extended-remote}. This should be set to a filename valid on the
17262 target system. If it is not set, the target will use a default
17263 filename (e.g.@: the last program run).
17265 @item set remote interrupt-sequence
17266 @cindex interrupt remote programs
17267 @cindex select Ctrl-C, BREAK or BREAK-g
17268 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17269 @samp{BREAK-g} as the
17270 sequence to the remote target in order to interrupt the execution.
17271 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17272 is high level of serial line for some certain time.
17273 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17274 It is @code{BREAK} signal followed by character @code{g}.
17276 @item show interrupt-sequence
17277 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17278 is sent by @value{GDBN} to interrupt the remote program.
17279 @code{BREAK-g} is BREAK signal followed by @code{g} and
17280 also known as Magic SysRq g.
17282 @item set remote interrupt-on-connect
17283 @cindex send interrupt-sequence on start
17284 Specify whether interrupt-sequence is sent to remote target when
17285 @value{GDBN} connects to it. This is mostly needed when you debug
17286 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17287 which is known as Magic SysRq g in order to connect @value{GDBN}.
17289 @item show interrupt-on-connect
17290 Show whether interrupt-sequence is sent
17291 to remote target when @value{GDBN} connects to it.
17295 @item set tcp auto-retry on
17296 @cindex auto-retry, for remote TCP target
17297 Enable auto-retry for remote TCP connections. This is useful if the remote
17298 debugging agent is launched in parallel with @value{GDBN}; there is a race
17299 condition because the agent may not become ready to accept the connection
17300 before @value{GDBN} attempts to connect. When auto-retry is
17301 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17302 to establish the connection using the timeout specified by
17303 @code{set tcp connect-timeout}.
17305 @item set tcp auto-retry off
17306 Do not auto-retry failed TCP connections.
17308 @item show tcp auto-retry
17309 Show the current auto-retry setting.
17311 @item set tcp connect-timeout @var{seconds}
17312 @cindex connection timeout, for remote TCP target
17313 @cindex timeout, for remote target connection
17314 Set the timeout for establishing a TCP connection to the remote target to
17315 @var{seconds}. The timeout affects both polling to retry failed connections
17316 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17317 that are merely slow to complete, and represents an approximate cumulative
17320 @item show tcp connect-timeout
17321 Show the current connection timeout setting.
17324 @cindex remote packets, enabling and disabling
17325 The @value{GDBN} remote protocol autodetects the packets supported by
17326 your debugging stub. If you need to override the autodetection, you
17327 can use these commands to enable or disable individual packets. Each
17328 packet can be set to @samp{on} (the remote target supports this
17329 packet), @samp{off} (the remote target does not support this packet),
17330 or @samp{auto} (detect remote target support for this packet). They
17331 all default to @samp{auto}. For more information about each packet,
17332 see @ref{Remote Protocol}.
17334 During normal use, you should not have to use any of these commands.
17335 If you do, that may be a bug in your remote debugging stub, or a bug
17336 in @value{GDBN}. You may want to report the problem to the
17337 @value{GDBN} developers.
17339 For each packet @var{name}, the command to enable or disable the
17340 packet is @code{set remote @var{name}-packet}. The available settings
17343 @multitable @columnfractions 0.28 0.32 0.25
17346 @tab Related Features
17348 @item @code{fetch-register}
17350 @tab @code{info registers}
17352 @item @code{set-register}
17356 @item @code{binary-download}
17358 @tab @code{load}, @code{set}
17360 @item @code{read-aux-vector}
17361 @tab @code{qXfer:auxv:read}
17362 @tab @code{info auxv}
17364 @item @code{symbol-lookup}
17365 @tab @code{qSymbol}
17366 @tab Detecting multiple threads
17368 @item @code{attach}
17369 @tab @code{vAttach}
17372 @item @code{verbose-resume}
17374 @tab Stepping or resuming multiple threads
17380 @item @code{software-breakpoint}
17384 @item @code{hardware-breakpoint}
17388 @item @code{write-watchpoint}
17392 @item @code{read-watchpoint}
17396 @item @code{access-watchpoint}
17400 @item @code{target-features}
17401 @tab @code{qXfer:features:read}
17402 @tab @code{set architecture}
17404 @item @code{library-info}
17405 @tab @code{qXfer:libraries:read}
17406 @tab @code{info sharedlibrary}
17408 @item @code{memory-map}
17409 @tab @code{qXfer:memory-map:read}
17410 @tab @code{info mem}
17412 @item @code{read-sdata-object}
17413 @tab @code{qXfer:sdata:read}
17414 @tab @code{print $_sdata}
17416 @item @code{read-spu-object}
17417 @tab @code{qXfer:spu:read}
17418 @tab @code{info spu}
17420 @item @code{write-spu-object}
17421 @tab @code{qXfer:spu:write}
17422 @tab @code{info spu}
17424 @item @code{read-siginfo-object}
17425 @tab @code{qXfer:siginfo:read}
17426 @tab @code{print $_siginfo}
17428 @item @code{write-siginfo-object}
17429 @tab @code{qXfer:siginfo:write}
17430 @tab @code{set $_siginfo}
17432 @item @code{threads}
17433 @tab @code{qXfer:threads:read}
17434 @tab @code{info threads}
17436 @item @code{get-thread-local-@*storage-address}
17437 @tab @code{qGetTLSAddr}
17438 @tab Displaying @code{__thread} variables
17440 @item @code{get-thread-information-block-address}
17441 @tab @code{qGetTIBAddr}
17442 @tab Display MS-Windows Thread Information Block.
17444 @item @code{search-memory}
17445 @tab @code{qSearch:memory}
17448 @item @code{supported-packets}
17449 @tab @code{qSupported}
17450 @tab Remote communications parameters
17452 @item @code{pass-signals}
17453 @tab @code{QPassSignals}
17454 @tab @code{handle @var{signal}}
17456 @item @code{hostio-close-packet}
17457 @tab @code{vFile:close}
17458 @tab @code{remote get}, @code{remote put}
17460 @item @code{hostio-open-packet}
17461 @tab @code{vFile:open}
17462 @tab @code{remote get}, @code{remote put}
17464 @item @code{hostio-pread-packet}
17465 @tab @code{vFile:pread}
17466 @tab @code{remote get}, @code{remote put}
17468 @item @code{hostio-pwrite-packet}
17469 @tab @code{vFile:pwrite}
17470 @tab @code{remote get}, @code{remote put}
17472 @item @code{hostio-unlink-packet}
17473 @tab @code{vFile:unlink}
17474 @tab @code{remote delete}
17476 @item @code{hostio-readlink-packet}
17477 @tab @code{vFile:readlink}
17480 @item @code{noack-packet}
17481 @tab @code{QStartNoAckMode}
17482 @tab Packet acknowledgment
17484 @item @code{osdata}
17485 @tab @code{qXfer:osdata:read}
17486 @tab @code{info os}
17488 @item @code{query-attached}
17489 @tab @code{qAttached}
17490 @tab Querying remote process attach state.
17492 @item @code{traceframe-info}
17493 @tab @code{qXfer:traceframe-info:read}
17494 @tab Traceframe info
17496 @item @code{install-in-trace}
17497 @tab @code{InstallInTrace}
17498 @tab Install tracepoint in tracing
17500 @item @code{disable-randomization}
17501 @tab @code{QDisableRandomization}
17502 @tab @code{set disable-randomization}
17506 @section Implementing a Remote Stub
17508 @cindex debugging stub, example
17509 @cindex remote stub, example
17510 @cindex stub example, remote debugging
17511 The stub files provided with @value{GDBN} implement the target side of the
17512 communication protocol, and the @value{GDBN} side is implemented in the
17513 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17514 these subroutines to communicate, and ignore the details. (If you're
17515 implementing your own stub file, you can still ignore the details: start
17516 with one of the existing stub files. @file{sparc-stub.c} is the best
17517 organized, and therefore the easiest to read.)
17519 @cindex remote serial debugging, overview
17520 To debug a program running on another machine (the debugging
17521 @dfn{target} machine), you must first arrange for all the usual
17522 prerequisites for the program to run by itself. For example, for a C
17527 A startup routine to set up the C runtime environment; these usually
17528 have a name like @file{crt0}. The startup routine may be supplied by
17529 your hardware supplier, or you may have to write your own.
17532 A C subroutine library to support your program's
17533 subroutine calls, notably managing input and output.
17536 A way of getting your program to the other machine---for example, a
17537 download program. These are often supplied by the hardware
17538 manufacturer, but you may have to write your own from hardware
17542 The next step is to arrange for your program to use a serial port to
17543 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17544 machine). In general terms, the scheme looks like this:
17548 @value{GDBN} already understands how to use this protocol; when everything
17549 else is set up, you can simply use the @samp{target remote} command
17550 (@pxref{Targets,,Specifying a Debugging Target}).
17552 @item On the target,
17553 you must link with your program a few special-purpose subroutines that
17554 implement the @value{GDBN} remote serial protocol. The file containing these
17555 subroutines is called a @dfn{debugging stub}.
17557 On certain remote targets, you can use an auxiliary program
17558 @code{gdbserver} instead of linking a stub into your program.
17559 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17562 The debugging stub is specific to the architecture of the remote
17563 machine; for example, use @file{sparc-stub.c} to debug programs on
17566 @cindex remote serial stub list
17567 These working remote stubs are distributed with @value{GDBN}:
17572 @cindex @file{i386-stub.c}
17575 For Intel 386 and compatible architectures.
17578 @cindex @file{m68k-stub.c}
17579 @cindex Motorola 680x0
17581 For Motorola 680x0 architectures.
17584 @cindex @file{sh-stub.c}
17587 For Renesas SH architectures.
17590 @cindex @file{sparc-stub.c}
17592 For @sc{sparc} architectures.
17594 @item sparcl-stub.c
17595 @cindex @file{sparcl-stub.c}
17598 For Fujitsu @sc{sparclite} architectures.
17602 The @file{README} file in the @value{GDBN} distribution may list other
17603 recently added stubs.
17606 * Stub Contents:: What the stub can do for you
17607 * Bootstrapping:: What you must do for the stub
17608 * Debug Session:: Putting it all together
17611 @node Stub Contents
17612 @subsection What the Stub Can Do for You
17614 @cindex remote serial stub
17615 The debugging stub for your architecture supplies these three
17619 @item set_debug_traps
17620 @findex set_debug_traps
17621 @cindex remote serial stub, initialization
17622 This routine arranges for @code{handle_exception} to run when your
17623 program stops. You must call this subroutine explicitly in your
17624 program's startup code.
17626 @item handle_exception
17627 @findex handle_exception
17628 @cindex remote serial stub, main routine
17629 This is the central workhorse, but your program never calls it
17630 explicitly---the setup code arranges for @code{handle_exception} to
17631 run when a trap is triggered.
17633 @code{handle_exception} takes control when your program stops during
17634 execution (for example, on a breakpoint), and mediates communications
17635 with @value{GDBN} on the host machine. This is where the communications
17636 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17637 representative on the target machine. It begins by sending summary
17638 information on the state of your program, then continues to execute,
17639 retrieving and transmitting any information @value{GDBN} needs, until you
17640 execute a @value{GDBN} command that makes your program resume; at that point,
17641 @code{handle_exception} returns control to your own code on the target
17645 @cindex @code{breakpoint} subroutine, remote
17646 Use this auxiliary subroutine to make your program contain a
17647 breakpoint. Depending on the particular situation, this may be the only
17648 way for @value{GDBN} to get control. For instance, if your target
17649 machine has some sort of interrupt button, you won't need to call this;
17650 pressing the interrupt button transfers control to
17651 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17652 simply receiving characters on the serial port may also trigger a trap;
17653 again, in that situation, you don't need to call @code{breakpoint} from
17654 your own program---simply running @samp{target remote} from the host
17655 @value{GDBN} session gets control.
17657 Call @code{breakpoint} if none of these is true, or if you simply want
17658 to make certain your program stops at a predetermined point for the
17659 start of your debugging session.
17662 @node Bootstrapping
17663 @subsection What You Must Do for the Stub
17665 @cindex remote stub, support routines
17666 The debugging stubs that come with @value{GDBN} are set up for a particular
17667 chip architecture, but they have no information about the rest of your
17668 debugging target machine.
17670 First of all you need to tell the stub how to communicate with the
17674 @item int getDebugChar()
17675 @findex getDebugChar
17676 Write this subroutine to read a single character from the serial port.
17677 It may be identical to @code{getchar} for your target system; a
17678 different name is used to allow you to distinguish the two if you wish.
17680 @item void putDebugChar(int)
17681 @findex putDebugChar
17682 Write this subroutine to write a single character to the serial port.
17683 It may be identical to @code{putchar} for your target system; a
17684 different name is used to allow you to distinguish the two if you wish.
17687 @cindex control C, and remote debugging
17688 @cindex interrupting remote targets
17689 If you want @value{GDBN} to be able to stop your program while it is
17690 running, you need to use an interrupt-driven serial driver, and arrange
17691 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17692 character). That is the character which @value{GDBN} uses to tell the
17693 remote system to stop.
17695 Getting the debugging target to return the proper status to @value{GDBN}
17696 probably requires changes to the standard stub; one quick and dirty way
17697 is to just execute a breakpoint instruction (the ``dirty'' part is that
17698 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17700 Other routines you need to supply are:
17703 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17704 @findex exceptionHandler
17705 Write this function to install @var{exception_address} in the exception
17706 handling tables. You need to do this because the stub does not have any
17707 way of knowing what the exception handling tables on your target system
17708 are like (for example, the processor's table might be in @sc{rom},
17709 containing entries which point to a table in @sc{ram}).
17710 @var{exception_number} is the exception number which should be changed;
17711 its meaning is architecture-dependent (for example, different numbers
17712 might represent divide by zero, misaligned access, etc). When this
17713 exception occurs, control should be transferred directly to
17714 @var{exception_address}, and the processor state (stack, registers,
17715 and so on) should be just as it is when a processor exception occurs. So if
17716 you want to use a jump instruction to reach @var{exception_address}, it
17717 should be a simple jump, not a jump to subroutine.
17719 For the 386, @var{exception_address} should be installed as an interrupt
17720 gate so that interrupts are masked while the handler runs. The gate
17721 should be at privilege level 0 (the most privileged level). The
17722 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17723 help from @code{exceptionHandler}.
17725 @item void flush_i_cache()
17726 @findex flush_i_cache
17727 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17728 instruction cache, if any, on your target machine. If there is no
17729 instruction cache, this subroutine may be a no-op.
17731 On target machines that have instruction caches, @value{GDBN} requires this
17732 function to make certain that the state of your program is stable.
17736 You must also make sure this library routine is available:
17739 @item void *memset(void *, int, int)
17741 This is the standard library function @code{memset} that sets an area of
17742 memory to a known value. If you have one of the free versions of
17743 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17744 either obtain it from your hardware manufacturer, or write your own.
17747 If you do not use the GNU C compiler, you may need other standard
17748 library subroutines as well; this varies from one stub to another,
17749 but in general the stubs are likely to use any of the common library
17750 subroutines which @code{@value{NGCC}} generates as inline code.
17753 @node Debug Session
17754 @subsection Putting it All Together
17756 @cindex remote serial debugging summary
17757 In summary, when your program is ready to debug, you must follow these
17762 Make sure you have defined the supporting low-level routines
17763 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17765 @code{getDebugChar}, @code{putDebugChar},
17766 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17770 Insert these lines in your program's startup code, before the main
17771 procedure is called:
17778 On some machines, when a breakpoint trap is raised, the hardware
17779 automatically makes the PC point to the instruction after the
17780 breakpoint. If your machine doesn't do that, you may need to adjust
17781 @code{handle_exception} to arrange for it to return to the instruction
17782 after the breakpoint on this first invocation, so that your program
17783 doesn't keep hitting the initial breakpoint instead of making
17787 For the 680x0 stub only, you need to provide a variable called
17788 @code{exceptionHook}. Normally you just use:
17791 void (*exceptionHook)() = 0;
17795 but if before calling @code{set_debug_traps}, you set it to point to a
17796 function in your program, that function is called when
17797 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17798 error). The function indicated by @code{exceptionHook} is called with
17799 one parameter: an @code{int} which is the exception number.
17802 Compile and link together: your program, the @value{GDBN} debugging stub for
17803 your target architecture, and the supporting subroutines.
17806 Make sure you have a serial connection between your target machine and
17807 the @value{GDBN} host, and identify the serial port on the host.
17810 @c The "remote" target now provides a `load' command, so we should
17811 @c document that. FIXME.
17812 Download your program to your target machine (or get it there by
17813 whatever means the manufacturer provides), and start it.
17816 Start @value{GDBN} on the host, and connect to the target
17817 (@pxref{Connecting,,Connecting to a Remote Target}).
17821 @node Configurations
17822 @chapter Configuration-Specific Information
17824 While nearly all @value{GDBN} commands are available for all native and
17825 cross versions of the debugger, there are some exceptions. This chapter
17826 describes things that are only available in certain configurations.
17828 There are three major categories of configurations: native
17829 configurations, where the host and target are the same, embedded
17830 operating system configurations, which are usually the same for several
17831 different processor architectures, and bare embedded processors, which
17832 are quite different from each other.
17837 * Embedded Processors::
17844 This section describes details specific to particular native
17849 * BSD libkvm Interface:: Debugging BSD kernel memory images
17850 * SVR4 Process Information:: SVR4 process information
17851 * DJGPP Native:: Features specific to the DJGPP port
17852 * Cygwin Native:: Features specific to the Cygwin port
17853 * Hurd Native:: Features specific to @sc{gnu} Hurd
17854 * Neutrino:: Features specific to QNX Neutrino
17855 * Darwin:: Features specific to Darwin
17861 On HP-UX systems, if you refer to a function or variable name that
17862 begins with a dollar sign, @value{GDBN} searches for a user or system
17863 name first, before it searches for a convenience variable.
17866 @node BSD libkvm Interface
17867 @subsection BSD libkvm Interface
17870 @cindex kernel memory image
17871 @cindex kernel crash dump
17873 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17874 interface that provides a uniform interface for accessing kernel virtual
17875 memory images, including live systems and crash dumps. @value{GDBN}
17876 uses this interface to allow you to debug live kernels and kernel crash
17877 dumps on many native BSD configurations. This is implemented as a
17878 special @code{kvm} debugging target. For debugging a live system, load
17879 the currently running kernel into @value{GDBN} and connect to the
17883 (@value{GDBP}) @b{target kvm}
17886 For debugging crash dumps, provide the file name of the crash dump as an
17890 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17893 Once connected to the @code{kvm} target, the following commands are
17899 Set current context from the @dfn{Process Control Block} (PCB) address.
17902 Set current context from proc address. This command isn't available on
17903 modern FreeBSD systems.
17906 @node SVR4 Process Information
17907 @subsection SVR4 Process Information
17909 @cindex examine process image
17910 @cindex process info via @file{/proc}
17912 Many versions of SVR4 and compatible systems provide a facility called
17913 @samp{/proc} that can be used to examine the image of a running
17914 process using file-system subroutines. If @value{GDBN} is configured
17915 for an operating system with this facility, the command @code{info
17916 proc} is available to report information about the process running
17917 your program, or about any process running on your system. @code{info
17918 proc} works only on SVR4 systems that include the @code{procfs} code.
17919 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17920 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17926 @itemx info proc @var{process-id}
17927 Summarize available information about any running process. If a
17928 process ID is specified by @var{process-id}, display information about
17929 that process; otherwise display information about the program being
17930 debugged. The summary includes the debugged process ID, the command
17931 line used to invoke it, its current working directory, and its
17932 executable file's absolute file name.
17934 On some systems, @var{process-id} can be of the form
17935 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17936 within a process. If the optional @var{pid} part is missing, it means
17937 a thread from the process being debugged (the leading @samp{/} still
17938 needs to be present, or else @value{GDBN} will interpret the number as
17939 a process ID rather than a thread ID).
17941 @item info proc mappings
17942 @cindex memory address space mappings
17943 Report the memory address space ranges accessible in the program, with
17944 information on whether the process has read, write, or execute access
17945 rights to each range. On @sc{gnu}/Linux systems, each memory range
17946 includes the object file which is mapped to that range, instead of the
17947 memory access rights to that range.
17949 @item info proc stat
17950 @itemx info proc status
17951 @cindex process detailed status information
17952 These subcommands are specific to @sc{gnu}/Linux systems. They show
17953 the process-related information, including the user ID and group ID;
17954 how many threads are there in the process; its virtual memory usage;
17955 the signals that are pending, blocked, and ignored; its TTY; its
17956 consumption of system and user time; its stack size; its @samp{nice}
17957 value; etc. For more information, see the @samp{proc} man page
17958 (type @kbd{man 5 proc} from your shell prompt).
17960 @item info proc all
17961 Show all the information about the process described under all of the
17962 above @code{info proc} subcommands.
17965 @comment These sub-options of 'info proc' were not included when
17966 @comment procfs.c was re-written. Keep their descriptions around
17967 @comment against the day when someone finds the time to put them back in.
17968 @kindex info proc times
17969 @item info proc times
17970 Starting time, user CPU time, and system CPU time for your program and
17973 @kindex info proc id
17975 Report on the process IDs related to your program: its own process ID,
17976 the ID of its parent, the process group ID, and the session ID.
17979 @item set procfs-trace
17980 @kindex set procfs-trace
17981 @cindex @code{procfs} API calls
17982 This command enables and disables tracing of @code{procfs} API calls.
17984 @item show procfs-trace
17985 @kindex show procfs-trace
17986 Show the current state of @code{procfs} API call tracing.
17988 @item set procfs-file @var{file}
17989 @kindex set procfs-file
17990 Tell @value{GDBN} to write @code{procfs} API trace to the named
17991 @var{file}. @value{GDBN} appends the trace info to the previous
17992 contents of the file. The default is to display the trace on the
17995 @item show procfs-file
17996 @kindex show procfs-file
17997 Show the file to which @code{procfs} API trace is written.
17999 @item proc-trace-entry
18000 @itemx proc-trace-exit
18001 @itemx proc-untrace-entry
18002 @itemx proc-untrace-exit
18003 @kindex proc-trace-entry
18004 @kindex proc-trace-exit
18005 @kindex proc-untrace-entry
18006 @kindex proc-untrace-exit
18007 These commands enable and disable tracing of entries into and exits
18008 from the @code{syscall} interface.
18011 @kindex info pidlist
18012 @cindex process list, QNX Neutrino
18013 For QNX Neutrino only, this command displays the list of all the
18014 processes and all the threads within each process.
18017 @kindex info meminfo
18018 @cindex mapinfo list, QNX Neutrino
18019 For QNX Neutrino only, this command displays the list of all mapinfos.
18023 @subsection Features for Debugging @sc{djgpp} Programs
18024 @cindex @sc{djgpp} debugging
18025 @cindex native @sc{djgpp} debugging
18026 @cindex MS-DOS-specific commands
18029 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18030 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18031 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18032 top of real-mode DOS systems and their emulations.
18034 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18035 defines a few commands specific to the @sc{djgpp} port. This
18036 subsection describes those commands.
18041 This is a prefix of @sc{djgpp}-specific commands which print
18042 information about the target system and important OS structures.
18045 @cindex MS-DOS system info
18046 @cindex free memory information (MS-DOS)
18047 @item info dos sysinfo
18048 This command displays assorted information about the underlying
18049 platform: the CPU type and features, the OS version and flavor, the
18050 DPMI version, and the available conventional and DPMI memory.
18055 @cindex segment descriptor tables
18056 @cindex descriptor tables display
18058 @itemx info dos ldt
18059 @itemx info dos idt
18060 These 3 commands display entries from, respectively, Global, Local,
18061 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18062 tables are data structures which store a descriptor for each segment
18063 that is currently in use. The segment's selector is an index into a
18064 descriptor table; the table entry for that index holds the
18065 descriptor's base address and limit, and its attributes and access
18068 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18069 segment (used for both data and the stack), and a DOS segment (which
18070 allows access to DOS/BIOS data structures and absolute addresses in
18071 conventional memory). However, the DPMI host will usually define
18072 additional segments in order to support the DPMI environment.
18074 @cindex garbled pointers
18075 These commands allow to display entries from the descriptor tables.
18076 Without an argument, all entries from the specified table are
18077 displayed. An argument, which should be an integer expression, means
18078 display a single entry whose index is given by the argument. For
18079 example, here's a convenient way to display information about the
18080 debugged program's data segment:
18083 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18084 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18088 This comes in handy when you want to see whether a pointer is outside
18089 the data segment's limit (i.e.@: @dfn{garbled}).
18091 @cindex page tables display (MS-DOS)
18093 @itemx info dos pte
18094 These two commands display entries from, respectively, the Page
18095 Directory and the Page Tables. Page Directories and Page Tables are
18096 data structures which control how virtual memory addresses are mapped
18097 into physical addresses. A Page Table includes an entry for every
18098 page of memory that is mapped into the program's address space; there
18099 may be several Page Tables, each one holding up to 4096 entries. A
18100 Page Directory has up to 4096 entries, one each for every Page Table
18101 that is currently in use.
18103 Without an argument, @kbd{info dos pde} displays the entire Page
18104 Directory, and @kbd{info dos pte} displays all the entries in all of
18105 the Page Tables. An argument, an integer expression, given to the
18106 @kbd{info dos pde} command means display only that entry from the Page
18107 Directory table. An argument given to the @kbd{info dos pte} command
18108 means display entries from a single Page Table, the one pointed to by
18109 the specified entry in the Page Directory.
18111 @cindex direct memory access (DMA) on MS-DOS
18112 These commands are useful when your program uses @dfn{DMA} (Direct
18113 Memory Access), which needs physical addresses to program the DMA
18116 These commands are supported only with some DPMI servers.
18118 @cindex physical address from linear address
18119 @item info dos address-pte @var{addr}
18120 This command displays the Page Table entry for a specified linear
18121 address. The argument @var{addr} is a linear address which should
18122 already have the appropriate segment's base address added to it,
18123 because this command accepts addresses which may belong to @emph{any}
18124 segment. For example, here's how to display the Page Table entry for
18125 the page where a variable @code{i} is stored:
18128 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18129 @exdent @code{Page Table entry for address 0x11a00d30:}
18130 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18134 This says that @code{i} is stored at offset @code{0xd30} from the page
18135 whose physical base address is @code{0x02698000}, and shows all the
18136 attributes of that page.
18138 Note that you must cast the addresses of variables to a @code{char *},
18139 since otherwise the value of @code{__djgpp_base_address}, the base
18140 address of all variables and functions in a @sc{djgpp} program, will
18141 be added using the rules of C pointer arithmetics: if @code{i} is
18142 declared an @code{int}, @value{GDBN} will add 4 times the value of
18143 @code{__djgpp_base_address} to the address of @code{i}.
18145 Here's another example, it displays the Page Table entry for the
18149 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18150 @exdent @code{Page Table entry for address 0x29110:}
18151 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18155 (The @code{+ 3} offset is because the transfer buffer's address is the
18156 3rd member of the @code{_go32_info_block} structure.) The output
18157 clearly shows that this DPMI server maps the addresses in conventional
18158 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18159 linear (@code{0x29110}) addresses are identical.
18161 This command is supported only with some DPMI servers.
18164 @cindex DOS serial data link, remote debugging
18165 In addition to native debugging, the DJGPP port supports remote
18166 debugging via a serial data link. The following commands are specific
18167 to remote serial debugging in the DJGPP port of @value{GDBN}.
18170 @kindex set com1base
18171 @kindex set com1irq
18172 @kindex set com2base
18173 @kindex set com2irq
18174 @kindex set com3base
18175 @kindex set com3irq
18176 @kindex set com4base
18177 @kindex set com4irq
18178 @item set com1base @var{addr}
18179 This command sets the base I/O port address of the @file{COM1} serial
18182 @item set com1irq @var{irq}
18183 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18184 for the @file{COM1} serial port.
18186 There are similar commands @samp{set com2base}, @samp{set com3irq},
18187 etc.@: for setting the port address and the @code{IRQ} lines for the
18190 @kindex show com1base
18191 @kindex show com1irq
18192 @kindex show com2base
18193 @kindex show com2irq
18194 @kindex show com3base
18195 @kindex show com3irq
18196 @kindex show com4base
18197 @kindex show com4irq
18198 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18199 display the current settings of the base address and the @code{IRQ}
18200 lines used by the COM ports.
18203 @kindex info serial
18204 @cindex DOS serial port status
18205 This command prints the status of the 4 DOS serial ports. For each
18206 port, it prints whether it's active or not, its I/O base address and
18207 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18208 counts of various errors encountered so far.
18212 @node Cygwin Native
18213 @subsection Features for Debugging MS Windows PE Executables
18214 @cindex MS Windows debugging
18215 @cindex native Cygwin debugging
18216 @cindex Cygwin-specific commands
18218 @value{GDBN} supports native debugging of MS Windows programs, including
18219 DLLs with and without symbolic debugging information.
18221 @cindex Ctrl-BREAK, MS-Windows
18222 @cindex interrupt debuggee on MS-Windows
18223 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18224 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18225 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18226 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18227 sequence, which can be used to interrupt the debuggee even if it
18230 There are various additional Cygwin-specific commands, described in
18231 this section. Working with DLLs that have no debugging symbols is
18232 described in @ref{Non-debug DLL Symbols}.
18237 This is a prefix of MS Windows-specific commands which print
18238 information about the target system and important OS structures.
18240 @item info w32 selector
18241 This command displays information returned by
18242 the Win32 API @code{GetThreadSelectorEntry} function.
18243 It takes an optional argument that is evaluated to
18244 a long value to give the information about this given selector.
18245 Without argument, this command displays information
18246 about the six segment registers.
18248 @item info w32 thread-information-block
18249 This command displays thread specific information stored in the
18250 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18251 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18255 This is a Cygwin-specific alias of @code{info shared}.
18257 @kindex dll-symbols
18259 This command loads symbols from a dll similarly to
18260 add-sym command but without the need to specify a base address.
18262 @kindex set cygwin-exceptions
18263 @cindex debugging the Cygwin DLL
18264 @cindex Cygwin DLL, debugging
18265 @item set cygwin-exceptions @var{mode}
18266 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18267 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18268 @value{GDBN} will delay recognition of exceptions, and may ignore some
18269 exceptions which seem to be caused by internal Cygwin DLL
18270 ``bookkeeping''. This option is meant primarily for debugging the
18271 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18272 @value{GDBN} users with false @code{SIGSEGV} signals.
18274 @kindex show cygwin-exceptions
18275 @item show cygwin-exceptions
18276 Displays whether @value{GDBN} will break on exceptions that happen
18277 inside the Cygwin DLL itself.
18279 @kindex set new-console
18280 @item set new-console @var{mode}
18281 If @var{mode} is @code{on} the debuggee will
18282 be started in a new console on next start.
18283 If @var{mode} is @code{off}, the debuggee will
18284 be started in the same console as the debugger.
18286 @kindex show new-console
18287 @item show new-console
18288 Displays whether a new console is used
18289 when the debuggee is started.
18291 @kindex set new-group
18292 @item set new-group @var{mode}
18293 This boolean value controls whether the debuggee should
18294 start a new group or stay in the same group as the debugger.
18295 This affects the way the Windows OS handles
18298 @kindex show new-group
18299 @item show new-group
18300 Displays current value of new-group boolean.
18302 @kindex set debugevents
18303 @item set debugevents
18304 This boolean value adds debug output concerning kernel events related
18305 to the debuggee seen by the debugger. This includes events that
18306 signal thread and process creation and exit, DLL loading and
18307 unloading, console interrupts, and debugging messages produced by the
18308 Windows @code{OutputDebugString} API call.
18310 @kindex set debugexec
18311 @item set debugexec
18312 This boolean value adds debug output concerning execute events
18313 (such as resume thread) seen by the debugger.
18315 @kindex set debugexceptions
18316 @item set debugexceptions
18317 This boolean value adds debug output concerning exceptions in the
18318 debuggee seen by the debugger.
18320 @kindex set debugmemory
18321 @item set debugmemory
18322 This boolean value adds debug output concerning debuggee memory reads
18323 and writes by the debugger.
18327 This boolean values specifies whether the debuggee is called
18328 via a shell or directly (default value is on).
18332 Displays if the debuggee will be started with a shell.
18337 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18340 @node Non-debug DLL Symbols
18341 @subsubsection Support for DLLs without Debugging Symbols
18342 @cindex DLLs with no debugging symbols
18343 @cindex Minimal symbols and DLLs
18345 Very often on windows, some of the DLLs that your program relies on do
18346 not include symbolic debugging information (for example,
18347 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18348 symbols in a DLL, it relies on the minimal amount of symbolic
18349 information contained in the DLL's export table. This section
18350 describes working with such symbols, known internally to @value{GDBN} as
18351 ``minimal symbols''.
18353 Note that before the debugged program has started execution, no DLLs
18354 will have been loaded. The easiest way around this problem is simply to
18355 start the program --- either by setting a breakpoint or letting the
18356 program run once to completion. It is also possible to force
18357 @value{GDBN} to load a particular DLL before starting the executable ---
18358 see the shared library information in @ref{Files}, or the
18359 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18360 explicitly loading symbols from a DLL with no debugging information will
18361 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18362 which may adversely affect symbol lookup performance.
18364 @subsubsection DLL Name Prefixes
18366 In keeping with the naming conventions used by the Microsoft debugging
18367 tools, DLL export symbols are made available with a prefix based on the
18368 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18369 also entered into the symbol table, so @code{CreateFileA} is often
18370 sufficient. In some cases there will be name clashes within a program
18371 (particularly if the executable itself includes full debugging symbols)
18372 necessitating the use of the fully qualified name when referring to the
18373 contents of the DLL. Use single-quotes around the name to avoid the
18374 exclamation mark (``!'') being interpreted as a language operator.
18376 Note that the internal name of the DLL may be all upper-case, even
18377 though the file name of the DLL is lower-case, or vice-versa. Since
18378 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18379 some confusion. If in doubt, try the @code{info functions} and
18380 @code{info variables} commands or even @code{maint print msymbols}
18381 (@pxref{Symbols}). Here's an example:
18384 (@value{GDBP}) info function CreateFileA
18385 All functions matching regular expression "CreateFileA":
18387 Non-debugging symbols:
18388 0x77e885f4 CreateFileA
18389 0x77e885f4 KERNEL32!CreateFileA
18393 (@value{GDBP}) info function !
18394 All functions matching regular expression "!":
18396 Non-debugging symbols:
18397 0x6100114c cygwin1!__assert
18398 0x61004034 cygwin1!_dll_crt0@@0
18399 0x61004240 cygwin1!dll_crt0(per_process *)
18403 @subsubsection Working with Minimal Symbols
18405 Symbols extracted from a DLL's export table do not contain very much
18406 type information. All that @value{GDBN} can do is guess whether a symbol
18407 refers to a function or variable depending on the linker section that
18408 contains the symbol. Also note that the actual contents of the memory
18409 contained in a DLL are not available unless the program is running. This
18410 means that you cannot examine the contents of a variable or disassemble
18411 a function within a DLL without a running program.
18413 Variables are generally treated as pointers and dereferenced
18414 automatically. For this reason, it is often necessary to prefix a
18415 variable name with the address-of operator (``&'') and provide explicit
18416 type information in the command. Here's an example of the type of
18420 (@value{GDBP}) print 'cygwin1!__argv'
18425 (@value{GDBP}) x 'cygwin1!__argv'
18426 0x10021610: "\230y\""
18429 And two possible solutions:
18432 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18433 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18437 (@value{GDBP}) x/2x &'cygwin1!__argv'
18438 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18439 (@value{GDBP}) x/x 0x10021608
18440 0x10021608: 0x0022fd98
18441 (@value{GDBP}) x/s 0x0022fd98
18442 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18445 Setting a break point within a DLL is possible even before the program
18446 starts execution. However, under these circumstances, @value{GDBN} can't
18447 examine the initial instructions of the function in order to skip the
18448 function's frame set-up code. You can work around this by using ``*&''
18449 to set the breakpoint at a raw memory address:
18452 (@value{GDBP}) break *&'python22!PyOS_Readline'
18453 Breakpoint 1 at 0x1e04eff0
18456 The author of these extensions is not entirely convinced that setting a
18457 break point within a shared DLL like @file{kernel32.dll} is completely
18461 @subsection Commands Specific to @sc{gnu} Hurd Systems
18462 @cindex @sc{gnu} Hurd debugging
18464 This subsection describes @value{GDBN} commands specific to the
18465 @sc{gnu} Hurd native debugging.
18470 @kindex set signals@r{, Hurd command}
18471 @kindex set sigs@r{, Hurd command}
18472 This command toggles the state of inferior signal interception by
18473 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18474 affected by this command. @code{sigs} is a shorthand alias for
18479 @kindex show signals@r{, Hurd command}
18480 @kindex show sigs@r{, Hurd command}
18481 Show the current state of intercepting inferior's signals.
18483 @item set signal-thread
18484 @itemx set sigthread
18485 @kindex set signal-thread
18486 @kindex set sigthread
18487 This command tells @value{GDBN} which thread is the @code{libc} signal
18488 thread. That thread is run when a signal is delivered to a running
18489 process. @code{set sigthread} is the shorthand alias of @code{set
18492 @item show signal-thread
18493 @itemx show sigthread
18494 @kindex show signal-thread
18495 @kindex show sigthread
18496 These two commands show which thread will run when the inferior is
18497 delivered a signal.
18500 @kindex set stopped@r{, Hurd command}
18501 This commands tells @value{GDBN} that the inferior process is stopped,
18502 as with the @code{SIGSTOP} signal. The stopped process can be
18503 continued by delivering a signal to it.
18506 @kindex show stopped@r{, Hurd command}
18507 This command shows whether @value{GDBN} thinks the debuggee is
18510 @item set exceptions
18511 @kindex set exceptions@r{, Hurd command}
18512 Use this command to turn off trapping of exceptions in the inferior.
18513 When exception trapping is off, neither breakpoints nor
18514 single-stepping will work. To restore the default, set exception
18517 @item show exceptions
18518 @kindex show exceptions@r{, Hurd command}
18519 Show the current state of trapping exceptions in the inferior.
18521 @item set task pause
18522 @kindex set task@r{, Hurd commands}
18523 @cindex task attributes (@sc{gnu} Hurd)
18524 @cindex pause current task (@sc{gnu} Hurd)
18525 This command toggles task suspension when @value{GDBN} has control.
18526 Setting it to on takes effect immediately, and the task is suspended
18527 whenever @value{GDBN} gets control. Setting it to off will take
18528 effect the next time the inferior is continued. If this option is set
18529 to off, you can use @code{set thread default pause on} or @code{set
18530 thread pause on} (see below) to pause individual threads.
18532 @item show task pause
18533 @kindex show task@r{, Hurd commands}
18534 Show the current state of task suspension.
18536 @item set task detach-suspend-count
18537 @cindex task suspend count
18538 @cindex detach from task, @sc{gnu} Hurd
18539 This command sets the suspend count the task will be left with when
18540 @value{GDBN} detaches from it.
18542 @item show task detach-suspend-count
18543 Show the suspend count the task will be left with when detaching.
18545 @item set task exception-port
18546 @itemx set task excp
18547 @cindex task exception port, @sc{gnu} Hurd
18548 This command sets the task exception port to which @value{GDBN} will
18549 forward exceptions. The argument should be the value of the @dfn{send
18550 rights} of the task. @code{set task excp} is a shorthand alias.
18552 @item set noninvasive
18553 @cindex noninvasive task options
18554 This command switches @value{GDBN} to a mode that is the least
18555 invasive as far as interfering with the inferior is concerned. This
18556 is the same as using @code{set task pause}, @code{set exceptions}, and
18557 @code{set signals} to values opposite to the defaults.
18559 @item info send-rights
18560 @itemx info receive-rights
18561 @itemx info port-rights
18562 @itemx info port-sets
18563 @itemx info dead-names
18566 @cindex send rights, @sc{gnu} Hurd
18567 @cindex receive rights, @sc{gnu} Hurd
18568 @cindex port rights, @sc{gnu} Hurd
18569 @cindex port sets, @sc{gnu} Hurd
18570 @cindex dead names, @sc{gnu} Hurd
18571 These commands display information about, respectively, send rights,
18572 receive rights, port rights, port sets, and dead names of a task.
18573 There are also shorthand aliases: @code{info ports} for @code{info
18574 port-rights} and @code{info psets} for @code{info port-sets}.
18576 @item set thread pause
18577 @kindex set thread@r{, Hurd command}
18578 @cindex thread properties, @sc{gnu} Hurd
18579 @cindex pause current thread (@sc{gnu} Hurd)
18580 This command toggles current thread suspension when @value{GDBN} has
18581 control. Setting it to on takes effect immediately, and the current
18582 thread is suspended whenever @value{GDBN} gets control. Setting it to
18583 off will take effect the next time the inferior is continued.
18584 Normally, this command has no effect, since when @value{GDBN} has
18585 control, the whole task is suspended. However, if you used @code{set
18586 task pause off} (see above), this command comes in handy to suspend
18587 only the current thread.
18589 @item show thread pause
18590 @kindex show thread@r{, Hurd command}
18591 This command shows the state of current thread suspension.
18593 @item set thread run
18594 This command sets whether the current thread is allowed to run.
18596 @item show thread run
18597 Show whether the current thread is allowed to run.
18599 @item set thread detach-suspend-count
18600 @cindex thread suspend count, @sc{gnu} Hurd
18601 @cindex detach from thread, @sc{gnu} Hurd
18602 This command sets the suspend count @value{GDBN} will leave on a
18603 thread when detaching. This number is relative to the suspend count
18604 found by @value{GDBN} when it notices the thread; use @code{set thread
18605 takeover-suspend-count} to force it to an absolute value.
18607 @item show thread detach-suspend-count
18608 Show the suspend count @value{GDBN} will leave on the thread when
18611 @item set thread exception-port
18612 @itemx set thread excp
18613 Set the thread exception port to which to forward exceptions. This
18614 overrides the port set by @code{set task exception-port} (see above).
18615 @code{set thread excp} is the shorthand alias.
18617 @item set thread takeover-suspend-count
18618 Normally, @value{GDBN}'s thread suspend counts are relative to the
18619 value @value{GDBN} finds when it notices each thread. This command
18620 changes the suspend counts to be absolute instead.
18622 @item set thread default
18623 @itemx show thread default
18624 @cindex thread default settings, @sc{gnu} Hurd
18625 Each of the above @code{set thread} commands has a @code{set thread
18626 default} counterpart (e.g., @code{set thread default pause}, @code{set
18627 thread default exception-port}, etc.). The @code{thread default}
18628 variety of commands sets the default thread properties for all
18629 threads; you can then change the properties of individual threads with
18630 the non-default commands.
18635 @subsection QNX Neutrino
18636 @cindex QNX Neutrino
18638 @value{GDBN} provides the following commands specific to the QNX
18642 @item set debug nto-debug
18643 @kindex set debug nto-debug
18644 When set to on, enables debugging messages specific to the QNX
18647 @item show debug nto-debug
18648 @kindex show debug nto-debug
18649 Show the current state of QNX Neutrino messages.
18656 @value{GDBN} provides the following commands specific to the Darwin target:
18659 @item set debug darwin @var{num}
18660 @kindex set debug darwin
18661 When set to a non zero value, enables debugging messages specific to
18662 the Darwin support. Higher values produce more verbose output.
18664 @item show debug darwin
18665 @kindex show debug darwin
18666 Show the current state of Darwin messages.
18668 @item set debug mach-o @var{num}
18669 @kindex set debug mach-o
18670 When set to a non zero value, enables debugging messages while
18671 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18672 file format used on Darwin for object and executable files.) Higher
18673 values produce more verbose output. This is a command to diagnose
18674 problems internal to @value{GDBN} and should not be needed in normal
18677 @item show debug mach-o
18678 @kindex show debug mach-o
18679 Show the current state of Mach-O file messages.
18681 @item set mach-exceptions on
18682 @itemx set mach-exceptions off
18683 @kindex set mach-exceptions
18684 On Darwin, faults are first reported as a Mach exception and are then
18685 mapped to a Posix signal. Use this command to turn on trapping of
18686 Mach exceptions in the inferior. This might be sometimes useful to
18687 better understand the cause of a fault. The default is off.
18689 @item show mach-exceptions
18690 @kindex show mach-exceptions
18691 Show the current state of exceptions trapping.
18696 @section Embedded Operating Systems
18698 This section describes configurations involving the debugging of
18699 embedded operating systems that are available for several different
18703 * VxWorks:: Using @value{GDBN} with VxWorks
18706 @value{GDBN} includes the ability to debug programs running on
18707 various real-time operating systems.
18710 @subsection Using @value{GDBN} with VxWorks
18716 @kindex target vxworks
18717 @item target vxworks @var{machinename}
18718 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18719 is the target system's machine name or IP address.
18723 On VxWorks, @code{load} links @var{filename} dynamically on the
18724 current target system as well as adding its symbols in @value{GDBN}.
18726 @value{GDBN} enables developers to spawn and debug tasks running on networked
18727 VxWorks targets from a Unix host. Already-running tasks spawned from
18728 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18729 both the Unix host and on the VxWorks target. The program
18730 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18731 installed with the name @code{vxgdb}, to distinguish it from a
18732 @value{GDBN} for debugging programs on the host itself.)
18735 @item VxWorks-timeout @var{args}
18736 @kindex vxworks-timeout
18737 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18738 This option is set by the user, and @var{args} represents the number of
18739 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18740 your VxWorks target is a slow software simulator or is on the far side
18741 of a thin network line.
18744 The following information on connecting to VxWorks was current when
18745 this manual was produced; newer releases of VxWorks may use revised
18748 @findex INCLUDE_RDB
18749 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18750 to include the remote debugging interface routines in the VxWorks
18751 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18752 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18753 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18754 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18755 information on configuring and remaking VxWorks, see the manufacturer's
18757 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18759 Once you have included @file{rdb.a} in your VxWorks system image and set
18760 your Unix execution search path to find @value{GDBN}, you are ready to
18761 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18762 @code{vxgdb}, depending on your installation).
18764 @value{GDBN} comes up showing the prompt:
18771 * VxWorks Connection:: Connecting to VxWorks
18772 * VxWorks Download:: VxWorks download
18773 * VxWorks Attach:: Running tasks
18776 @node VxWorks Connection
18777 @subsubsection Connecting to VxWorks
18779 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18780 network. To connect to a target whose host name is ``@code{tt}'', type:
18783 (vxgdb) target vxworks tt
18787 @value{GDBN} displays messages like these:
18790 Attaching remote machine across net...
18795 @value{GDBN} then attempts to read the symbol tables of any object modules
18796 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18797 these files by searching the directories listed in the command search
18798 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18799 to find an object file, it displays a message such as:
18802 prog.o: No such file or directory.
18805 When this happens, add the appropriate directory to the search path with
18806 the @value{GDBN} command @code{path}, and execute the @code{target}
18809 @node VxWorks Download
18810 @subsubsection VxWorks Download
18812 @cindex download to VxWorks
18813 If you have connected to the VxWorks target and you want to debug an
18814 object that has not yet been loaded, you can use the @value{GDBN}
18815 @code{load} command to download a file from Unix to VxWorks
18816 incrementally. The object file given as an argument to the @code{load}
18817 command is actually opened twice: first by the VxWorks target in order
18818 to download the code, then by @value{GDBN} in order to read the symbol
18819 table. This can lead to problems if the current working directories on
18820 the two systems differ. If both systems have NFS mounted the same
18821 filesystems, you can avoid these problems by using absolute paths.
18822 Otherwise, it is simplest to set the working directory on both systems
18823 to the directory in which the object file resides, and then to reference
18824 the file by its name, without any path. For instance, a program
18825 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18826 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18827 program, type this on VxWorks:
18830 -> cd "@var{vxpath}/vw/demo/rdb"
18834 Then, in @value{GDBN}, type:
18837 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18838 (vxgdb) load prog.o
18841 @value{GDBN} displays a response similar to this:
18844 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18847 You can also use the @code{load} command to reload an object module
18848 after editing and recompiling the corresponding source file. Note that
18849 this makes @value{GDBN} delete all currently-defined breakpoints,
18850 auto-displays, and convenience variables, and to clear the value
18851 history. (This is necessary in order to preserve the integrity of
18852 debugger's data structures that reference the target system's symbol
18855 @node VxWorks Attach
18856 @subsubsection Running Tasks
18858 @cindex running VxWorks tasks
18859 You can also attach to an existing task using the @code{attach} command as
18863 (vxgdb) attach @var{task}
18867 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18868 or suspended when you attach to it. Running tasks are suspended at
18869 the time of attachment.
18871 @node Embedded Processors
18872 @section Embedded Processors
18874 This section goes into details specific to particular embedded
18877 @cindex send command to simulator
18878 Whenever a specific embedded processor has a simulator, @value{GDBN}
18879 allows to send an arbitrary command to the simulator.
18882 @item sim @var{command}
18883 @kindex sim@r{, a command}
18884 Send an arbitrary @var{command} string to the simulator. Consult the
18885 documentation for the specific simulator in use for information about
18886 acceptable commands.
18892 * M32R/D:: Renesas M32R/D
18893 * M68K:: Motorola M68K
18894 * MicroBlaze:: Xilinx MicroBlaze
18895 * MIPS Embedded:: MIPS Embedded
18896 * OpenRISC 1000:: OpenRisc 1000
18897 * PA:: HP PA Embedded
18898 * PowerPC Embedded:: PowerPC Embedded
18899 * Sparclet:: Tsqware Sparclet
18900 * Sparclite:: Fujitsu Sparclite
18901 * Z8000:: Zilog Z8000
18904 * Super-H:: Renesas Super-H
18913 @item target rdi @var{dev}
18914 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18915 use this target to communicate with both boards running the Angel
18916 monitor, or with the EmbeddedICE JTAG debug device.
18919 @item target rdp @var{dev}
18924 @value{GDBN} provides the following ARM-specific commands:
18927 @item set arm disassembler
18929 This commands selects from a list of disassembly styles. The
18930 @code{"std"} style is the standard style.
18932 @item show arm disassembler
18934 Show the current disassembly style.
18936 @item set arm apcs32
18937 @cindex ARM 32-bit mode
18938 This command toggles ARM operation mode between 32-bit and 26-bit.
18940 @item show arm apcs32
18941 Display the current usage of the ARM 32-bit mode.
18943 @item set arm fpu @var{fputype}
18944 This command sets the ARM floating-point unit (FPU) type. The
18945 argument @var{fputype} can be one of these:
18949 Determine the FPU type by querying the OS ABI.
18951 Software FPU, with mixed-endian doubles on little-endian ARM
18954 GCC-compiled FPA co-processor.
18956 Software FPU with pure-endian doubles.
18962 Show the current type of the FPU.
18965 This command forces @value{GDBN} to use the specified ABI.
18968 Show the currently used ABI.
18970 @item set arm fallback-mode (arm|thumb|auto)
18971 @value{GDBN} uses the symbol table, when available, to determine
18972 whether instructions are ARM or Thumb. This command controls
18973 @value{GDBN}'s default behavior when the symbol table is not
18974 available. The default is @samp{auto}, which causes @value{GDBN} to
18975 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18978 @item show arm fallback-mode
18979 Show the current fallback instruction mode.
18981 @item set arm force-mode (arm|thumb|auto)
18982 This command overrides use of the symbol table to determine whether
18983 instructions are ARM or Thumb. The default is @samp{auto}, which
18984 causes @value{GDBN} to use the symbol table and then the setting
18985 of @samp{set arm fallback-mode}.
18987 @item show arm force-mode
18988 Show the current forced instruction mode.
18990 @item set debug arm
18991 Toggle whether to display ARM-specific debugging messages from the ARM
18992 target support subsystem.
18994 @item show debug arm
18995 Show whether ARM-specific debugging messages are enabled.
18998 The following commands are available when an ARM target is debugged
18999 using the RDI interface:
19002 @item rdilogfile @r{[}@var{file}@r{]}
19004 @cindex ADP (Angel Debugger Protocol) logging
19005 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19006 With an argument, sets the log file to the specified @var{file}. With
19007 no argument, show the current log file name. The default log file is
19010 @item rdilogenable @r{[}@var{arg}@r{]}
19011 @kindex rdilogenable
19012 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19013 enables logging, with an argument 0 or @code{"no"} disables it. With
19014 no arguments displays the current setting. When logging is enabled,
19015 ADP packets exchanged between @value{GDBN} and the RDI target device
19016 are logged to a file.
19018 @item set rdiromatzero
19019 @kindex set rdiromatzero
19020 @cindex ROM at zero address, RDI
19021 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19022 vector catching is disabled, so that zero address can be used. If off
19023 (the default), vector catching is enabled. For this command to take
19024 effect, it needs to be invoked prior to the @code{target rdi} command.
19026 @item show rdiromatzero
19027 @kindex show rdiromatzero
19028 Show the current setting of ROM at zero address.
19030 @item set rdiheartbeat
19031 @kindex set rdiheartbeat
19032 @cindex RDI heartbeat
19033 Enable or disable RDI heartbeat packets. It is not recommended to
19034 turn on this option, since it confuses ARM and EPI JTAG interface, as
19035 well as the Angel monitor.
19037 @item show rdiheartbeat
19038 @kindex show rdiheartbeat
19039 Show the setting of RDI heartbeat packets.
19043 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19044 The @value{GDBN} ARM simulator accepts the following optional arguments.
19047 @item --swi-support=@var{type}
19048 Tell the simulator which SWI interfaces to support.
19049 @var{type} may be a comma separated list of the following values.
19050 The default value is @code{all}.
19063 @subsection Renesas M32R/D and M32R/SDI
19066 @kindex target m32r
19067 @item target m32r @var{dev}
19068 Renesas M32R/D ROM monitor.
19070 @kindex target m32rsdi
19071 @item target m32rsdi @var{dev}
19072 Renesas M32R SDI server, connected via parallel port to the board.
19075 The following @value{GDBN} commands are specific to the M32R monitor:
19078 @item set download-path @var{path}
19079 @kindex set download-path
19080 @cindex find downloadable @sc{srec} files (M32R)
19081 Set the default path for finding downloadable @sc{srec} files.
19083 @item show download-path
19084 @kindex show download-path
19085 Show the default path for downloadable @sc{srec} files.
19087 @item set board-address @var{addr}
19088 @kindex set board-address
19089 @cindex M32-EVA target board address
19090 Set the IP address for the M32R-EVA target board.
19092 @item show board-address
19093 @kindex show board-address
19094 Show the current IP address of the target board.
19096 @item set server-address @var{addr}
19097 @kindex set server-address
19098 @cindex download server address (M32R)
19099 Set the IP address for the download server, which is the @value{GDBN}'s
19102 @item show server-address
19103 @kindex show server-address
19104 Display the IP address of the download server.
19106 @item upload @r{[}@var{file}@r{]}
19107 @kindex upload@r{, M32R}
19108 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19109 upload capability. If no @var{file} argument is given, the current
19110 executable file is uploaded.
19112 @item tload @r{[}@var{file}@r{]}
19113 @kindex tload@r{, M32R}
19114 Test the @code{upload} command.
19117 The following commands are available for M32R/SDI:
19122 @cindex reset SDI connection, M32R
19123 This command resets the SDI connection.
19127 This command shows the SDI connection status.
19130 @kindex debug_chaos
19131 @cindex M32R/Chaos debugging
19132 Instructs the remote that M32R/Chaos debugging is to be used.
19134 @item use_debug_dma
19135 @kindex use_debug_dma
19136 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19139 @kindex use_mon_code
19140 Instructs the remote to use the MON_CODE method of accessing memory.
19143 @kindex use_ib_break
19144 Instructs the remote to set breakpoints by IB break.
19146 @item use_dbt_break
19147 @kindex use_dbt_break
19148 Instructs the remote to set breakpoints by DBT.
19154 The Motorola m68k configuration includes ColdFire support, and a
19155 target command for the following ROM monitor.
19159 @kindex target dbug
19160 @item target dbug @var{dev}
19161 dBUG ROM monitor for Motorola ColdFire.
19166 @subsection MicroBlaze
19167 @cindex Xilinx MicroBlaze
19168 @cindex XMD, Xilinx Microprocessor Debugger
19170 The MicroBlaze is a soft-core processor supported on various Xilinx
19171 FPGAs, such as Spartan or Virtex series. Boards with these processors
19172 usually have JTAG ports which connect to a host system running the Xilinx
19173 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19174 This host system is used to download the configuration bitstream to
19175 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19176 communicates with the target board using the JTAG interface and
19177 presents a @code{gdbserver} interface to the board. By default
19178 @code{xmd} uses port @code{1234}. (While it is possible to change
19179 this default port, it requires the use of undocumented @code{xmd}
19180 commands. Contact Xilinx support if you need to do this.)
19182 Use these GDB commands to connect to the MicroBlaze target processor.
19185 @item target remote :1234
19186 Use this command to connect to the target if you are running @value{GDBN}
19187 on the same system as @code{xmd}.
19189 @item target remote @var{xmd-host}:1234
19190 Use this command to connect to the target if it is connected to @code{xmd}
19191 running on a different system named @var{xmd-host}.
19194 Use this command to download a program to the MicroBlaze target.
19196 @item set debug microblaze @var{n}
19197 Enable MicroBlaze-specific debugging messages if non-zero.
19199 @item show debug microblaze @var{n}
19200 Show MicroBlaze-specific debugging level.
19203 @node MIPS Embedded
19204 @subsection MIPS Embedded
19206 @cindex MIPS boards
19207 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19208 MIPS board attached to a serial line. This is available when
19209 you configure @value{GDBN} with @samp{--target=mips-elf}.
19212 Use these @value{GDBN} commands to specify the connection to your target board:
19215 @item target mips @var{port}
19216 @kindex target mips @var{port}
19217 To run a program on the board, start up @code{@value{GDBP}} with the
19218 name of your program as the argument. To connect to the board, use the
19219 command @samp{target mips @var{port}}, where @var{port} is the name of
19220 the serial port connected to the board. If the program has not already
19221 been downloaded to the board, you may use the @code{load} command to
19222 download it. You can then use all the usual @value{GDBN} commands.
19224 For example, this sequence connects to the target board through a serial
19225 port, and loads and runs a program called @var{prog} through the
19229 host$ @value{GDBP} @var{prog}
19230 @value{GDBN} is free software and @dots{}
19231 (@value{GDBP}) target mips /dev/ttyb
19232 (@value{GDBP}) load @var{prog}
19236 @item target mips @var{hostname}:@var{portnumber}
19237 On some @value{GDBN} host configurations, you can specify a TCP
19238 connection (for instance, to a serial line managed by a terminal
19239 concentrator) instead of a serial port, using the syntax
19240 @samp{@var{hostname}:@var{portnumber}}.
19242 @item target pmon @var{port}
19243 @kindex target pmon @var{port}
19246 @item target ddb @var{port}
19247 @kindex target ddb @var{port}
19248 NEC's DDB variant of PMON for Vr4300.
19250 @item target lsi @var{port}
19251 @kindex target lsi @var{port}
19252 LSI variant of PMON.
19254 @kindex target r3900
19255 @item target r3900 @var{dev}
19256 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19258 @kindex target array
19259 @item target array @var{dev}
19260 Array Tech LSI33K RAID controller board.
19266 @value{GDBN} also supports these special commands for MIPS targets:
19269 @item set mipsfpu double
19270 @itemx set mipsfpu single
19271 @itemx set mipsfpu none
19272 @itemx set mipsfpu auto
19273 @itemx show mipsfpu
19274 @kindex set mipsfpu
19275 @kindex show mipsfpu
19276 @cindex MIPS remote floating point
19277 @cindex floating point, MIPS remote
19278 If your target board does not support the MIPS floating point
19279 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19280 need this, you may wish to put the command in your @value{GDBN} init
19281 file). This tells @value{GDBN} how to find the return value of
19282 functions which return floating point values. It also allows
19283 @value{GDBN} to avoid saving the floating point registers when calling
19284 functions on the board. If you are using a floating point coprocessor
19285 with only single precision floating point support, as on the @sc{r4650}
19286 processor, use the command @samp{set mipsfpu single}. The default
19287 double precision floating point coprocessor may be selected using
19288 @samp{set mipsfpu double}.
19290 In previous versions the only choices were double precision or no
19291 floating point, so @samp{set mipsfpu on} will select double precision
19292 and @samp{set mipsfpu off} will select no floating point.
19294 As usual, you can inquire about the @code{mipsfpu} variable with
19295 @samp{show mipsfpu}.
19297 @item set timeout @var{seconds}
19298 @itemx set retransmit-timeout @var{seconds}
19299 @itemx show timeout
19300 @itemx show retransmit-timeout
19301 @cindex @code{timeout}, MIPS protocol
19302 @cindex @code{retransmit-timeout}, MIPS protocol
19303 @kindex set timeout
19304 @kindex show timeout
19305 @kindex set retransmit-timeout
19306 @kindex show retransmit-timeout
19307 You can control the timeout used while waiting for a packet, in the MIPS
19308 remote protocol, with the @code{set timeout @var{seconds}} command. The
19309 default is 5 seconds. Similarly, you can control the timeout used while
19310 waiting for an acknowledgment of a packet with the @code{set
19311 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19312 You can inspect both values with @code{show timeout} and @code{show
19313 retransmit-timeout}. (These commands are @emph{only} available when
19314 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19316 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19317 is waiting for your program to stop. In that case, @value{GDBN} waits
19318 forever because it has no way of knowing how long the program is going
19319 to run before stopping.
19321 @item set syn-garbage-limit @var{num}
19322 @kindex set syn-garbage-limit@r{, MIPS remote}
19323 @cindex synchronize with remote MIPS target
19324 Limit the maximum number of characters @value{GDBN} should ignore when
19325 it tries to synchronize with the remote target. The default is 10
19326 characters. Setting the limit to -1 means there's no limit.
19328 @item show syn-garbage-limit
19329 @kindex show syn-garbage-limit@r{, MIPS remote}
19330 Show the current limit on the number of characters to ignore when
19331 trying to synchronize with the remote system.
19333 @item set monitor-prompt @var{prompt}
19334 @kindex set monitor-prompt@r{, MIPS remote}
19335 @cindex remote monitor prompt
19336 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19337 remote monitor. The default depends on the target:
19347 @item show monitor-prompt
19348 @kindex show monitor-prompt@r{, MIPS remote}
19349 Show the current strings @value{GDBN} expects as the prompt from the
19352 @item set monitor-warnings
19353 @kindex set monitor-warnings@r{, MIPS remote}
19354 Enable or disable monitor warnings about hardware breakpoints. This
19355 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19356 display warning messages whose codes are returned by the @code{lsi}
19357 PMON monitor for breakpoint commands.
19359 @item show monitor-warnings
19360 @kindex show monitor-warnings@r{, MIPS remote}
19361 Show the current setting of printing monitor warnings.
19363 @item pmon @var{command}
19364 @kindex pmon@r{, MIPS remote}
19365 @cindex send PMON command
19366 This command allows sending an arbitrary @var{command} string to the
19367 monitor. The monitor must be in debug mode for this to work.
19370 @node OpenRISC 1000
19371 @subsection OpenRISC 1000
19372 @cindex OpenRISC 1000
19374 @cindex or1k boards
19375 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19376 about platform and commands.
19380 @kindex target jtag
19381 @item target jtag jtag://@var{host}:@var{port}
19383 Connects to remote JTAG server.
19384 JTAG remote server can be either an or1ksim or JTAG server,
19385 connected via parallel port to the board.
19387 Example: @code{target jtag jtag://localhost:9999}
19390 @item or1ksim @var{command}
19391 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19392 Simulator, proprietary commands can be executed.
19394 @kindex info or1k spr
19395 @item info or1k spr
19396 Displays spr groups.
19398 @item info or1k spr @var{group}
19399 @itemx info or1k spr @var{groupno}
19400 Displays register names in selected group.
19402 @item info or1k spr @var{group} @var{register}
19403 @itemx info or1k spr @var{register}
19404 @itemx info or1k spr @var{groupno} @var{registerno}
19405 @itemx info or1k spr @var{registerno}
19406 Shows information about specified spr register.
19409 @item spr @var{group} @var{register} @var{value}
19410 @itemx spr @var{register @var{value}}
19411 @itemx spr @var{groupno} @var{registerno @var{value}}
19412 @itemx spr @var{registerno @var{value}}
19413 Writes @var{value} to specified spr register.
19416 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19417 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19418 program execution and is thus much faster. Hardware breakpoints/watchpoint
19419 triggers can be set using:
19422 Load effective address/data
19424 Store effective address/data
19426 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19431 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19432 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19434 @code{htrace} commands:
19435 @cindex OpenRISC 1000 htrace
19438 @item hwatch @var{conditional}
19439 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19440 or Data. For example:
19442 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19444 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19448 Display information about current HW trace configuration.
19450 @item htrace trigger @var{conditional}
19451 Set starting criteria for HW trace.
19453 @item htrace qualifier @var{conditional}
19454 Set acquisition qualifier for HW trace.
19456 @item htrace stop @var{conditional}
19457 Set HW trace stopping criteria.
19459 @item htrace record [@var{data}]*
19460 Selects the data to be recorded, when qualifier is met and HW trace was
19463 @item htrace enable
19464 @itemx htrace disable
19465 Enables/disables the HW trace.
19467 @item htrace rewind [@var{filename}]
19468 Clears currently recorded trace data.
19470 If filename is specified, new trace file is made and any newly collected data
19471 will be written there.
19473 @item htrace print [@var{start} [@var{len}]]
19474 Prints trace buffer, using current record configuration.
19476 @item htrace mode continuous
19477 Set continuous trace mode.
19479 @item htrace mode suspend
19480 Set suspend trace mode.
19484 @node PowerPC Embedded
19485 @subsection PowerPC Embedded
19487 @cindex DVC register
19488 @value{GDBN} supports using the DVC (Data Value Compare) register to
19489 implement in hardware simple hardware watchpoint conditions of the form:
19492 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19493 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19496 The DVC register will be automatically used when @value{GDBN} detects
19497 such pattern in a condition expression, and the created watchpoint uses one
19498 debug register (either the @code{exact-watchpoints} option is on and the
19499 variable is scalar, or the variable has a length of one byte). This feature
19500 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19503 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19504 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19505 in which case watchpoints using only one debug register are created when
19506 watching variables of scalar types.
19508 You can create an artificial array to watch an arbitrary memory
19509 region using one of the following commands (@pxref{Expressions}):
19512 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19513 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19516 PowerPC embedded processors support masked watchpoints. See the discussion
19517 about the @code{mask} argument in @ref{Set Watchpoints}.
19519 @cindex ranged breakpoint
19520 PowerPC embedded processors support hardware accelerated
19521 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19522 the inferior whenever it executes an instruction at any address within
19523 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19524 use the @code{break-range} command.
19526 @value{GDBN} provides the following PowerPC-specific commands:
19529 @kindex break-range
19530 @item break-range @var{start-location}, @var{end-location}
19531 Set a breakpoint for an address range.
19532 @var{start-location} and @var{end-location} can specify a function name,
19533 a line number, an offset of lines from the current line or from the start
19534 location, or an address of an instruction (see @ref{Specify Location},
19535 for a list of all the possible ways to specify a @var{location}.)
19536 The breakpoint will stop execution of the inferior whenever it
19537 executes an instruction at any address within the specified range,
19538 (including @var{start-location} and @var{end-location}.)
19540 @kindex set powerpc
19541 @item set powerpc soft-float
19542 @itemx show powerpc soft-float
19543 Force @value{GDBN} to use (or not use) a software floating point calling
19544 convention. By default, @value{GDBN} selects the calling convention based
19545 on the selected architecture and the provided executable file.
19547 @item set powerpc vector-abi
19548 @itemx show powerpc vector-abi
19549 Force @value{GDBN} to use the specified calling convention for vector
19550 arguments and return values. The valid options are @samp{auto};
19551 @samp{generic}, to avoid vector registers even if they are present;
19552 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19553 registers. By default, @value{GDBN} selects the calling convention
19554 based on the selected architecture and the provided executable file.
19556 @item set powerpc exact-watchpoints
19557 @itemx show powerpc exact-watchpoints
19558 Allow @value{GDBN} to use only one debug register when watching a variable
19559 of scalar type, thus assuming that the variable is accessed through the
19560 address of its first byte.
19562 @kindex target dink32
19563 @item target dink32 @var{dev}
19564 DINK32 ROM monitor.
19566 @kindex target ppcbug
19567 @item target ppcbug @var{dev}
19568 @kindex target ppcbug1
19569 @item target ppcbug1 @var{dev}
19570 PPCBUG ROM monitor for PowerPC.
19573 @item target sds @var{dev}
19574 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19577 @cindex SDS protocol
19578 The following commands specific to the SDS protocol are supported
19582 @item set sdstimeout @var{nsec}
19583 @kindex set sdstimeout
19584 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19585 default is 2 seconds.
19587 @item show sdstimeout
19588 @kindex show sdstimeout
19589 Show the current value of the SDS timeout.
19591 @item sds @var{command}
19592 @kindex sds@r{, a command}
19593 Send the specified @var{command} string to the SDS monitor.
19598 @subsection HP PA Embedded
19602 @kindex target op50n
19603 @item target op50n @var{dev}
19604 OP50N monitor, running on an OKI HPPA board.
19606 @kindex target w89k
19607 @item target w89k @var{dev}
19608 W89K monitor, running on a Winbond HPPA board.
19613 @subsection Tsqware Sparclet
19617 @value{GDBN} enables developers to debug tasks running on
19618 Sparclet targets from a Unix host.
19619 @value{GDBN} uses code that runs on
19620 both the Unix host and on the Sparclet target. The program
19621 @code{@value{GDBP}} is installed and executed on the Unix host.
19624 @item remotetimeout @var{args}
19625 @kindex remotetimeout
19626 @value{GDBN} supports the option @code{remotetimeout}.
19627 This option is set by the user, and @var{args} represents the number of
19628 seconds @value{GDBN} waits for responses.
19631 @cindex compiling, on Sparclet
19632 When compiling for debugging, include the options @samp{-g} to get debug
19633 information and @samp{-Ttext} to relocate the program to where you wish to
19634 load it on the target. You may also want to add the options @samp{-n} or
19635 @samp{-N} in order to reduce the size of the sections. Example:
19638 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19641 You can use @code{objdump} to verify that the addresses are what you intended:
19644 sparclet-aout-objdump --headers --syms prog
19647 @cindex running, on Sparclet
19649 your Unix execution search path to find @value{GDBN}, you are ready to
19650 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19651 (or @code{sparclet-aout-gdb}, depending on your installation).
19653 @value{GDBN} comes up showing the prompt:
19660 * Sparclet File:: Setting the file to debug
19661 * Sparclet Connection:: Connecting to Sparclet
19662 * Sparclet Download:: Sparclet download
19663 * Sparclet Execution:: Running and debugging
19666 @node Sparclet File
19667 @subsubsection Setting File to Debug
19669 The @value{GDBN} command @code{file} lets you choose with program to debug.
19672 (gdbslet) file prog
19676 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19677 @value{GDBN} locates
19678 the file by searching the directories listed in the command search
19680 If the file was compiled with debug information (option @samp{-g}), source
19681 files will be searched as well.
19682 @value{GDBN} locates
19683 the source files by searching the directories listed in the directory search
19684 path (@pxref{Environment, ,Your Program's Environment}).
19686 to find a file, it displays a message such as:
19689 prog: No such file or directory.
19692 When this happens, add the appropriate directories to the search paths with
19693 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19694 @code{target} command again.
19696 @node Sparclet Connection
19697 @subsubsection Connecting to Sparclet
19699 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19700 To connect to a target on serial port ``@code{ttya}'', type:
19703 (gdbslet) target sparclet /dev/ttya
19704 Remote target sparclet connected to /dev/ttya
19705 main () at ../prog.c:3
19709 @value{GDBN} displays messages like these:
19715 @node Sparclet Download
19716 @subsubsection Sparclet Download
19718 @cindex download to Sparclet
19719 Once connected to the Sparclet target,
19720 you can use the @value{GDBN}
19721 @code{load} command to download the file from the host to the target.
19722 The file name and load offset should be given as arguments to the @code{load}
19724 Since the file format is aout, the program must be loaded to the starting
19725 address. You can use @code{objdump} to find out what this value is. The load
19726 offset is an offset which is added to the VMA (virtual memory address)
19727 of each of the file's sections.
19728 For instance, if the program
19729 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19730 and bss at 0x12010170, in @value{GDBN}, type:
19733 (gdbslet) load prog 0x12010000
19734 Loading section .text, size 0xdb0 vma 0x12010000
19737 If the code is loaded at a different address then what the program was linked
19738 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19739 to tell @value{GDBN} where to map the symbol table.
19741 @node Sparclet Execution
19742 @subsubsection Running and Debugging
19744 @cindex running and debugging Sparclet programs
19745 You can now begin debugging the task using @value{GDBN}'s execution control
19746 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19747 manual for the list of commands.
19751 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19753 Starting program: prog
19754 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19755 3 char *symarg = 0;
19757 4 char *execarg = "hello!";
19762 @subsection Fujitsu Sparclite
19766 @kindex target sparclite
19767 @item target sparclite @var{dev}
19768 Fujitsu sparclite boards, used only for the purpose of loading.
19769 You must use an additional command to debug the program.
19770 For example: target remote @var{dev} using @value{GDBN} standard
19776 @subsection Zilog Z8000
19779 @cindex simulator, Z8000
19780 @cindex Zilog Z8000 simulator
19782 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19785 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19786 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19787 segmented variant). The simulator recognizes which architecture is
19788 appropriate by inspecting the object code.
19791 @item target sim @var{args}
19793 @kindex target sim@r{, with Z8000}
19794 Debug programs on a simulated CPU. If the simulator supports setup
19795 options, specify them via @var{args}.
19799 After specifying this target, you can debug programs for the simulated
19800 CPU in the same style as programs for your host computer; use the
19801 @code{file} command to load a new program image, the @code{run} command
19802 to run your program, and so on.
19804 As well as making available all the usual machine registers
19805 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19806 additional items of information as specially named registers:
19811 Counts clock-ticks in the simulator.
19814 Counts instructions run in the simulator.
19817 Execution time in 60ths of a second.
19821 You can refer to these values in @value{GDBN} expressions with the usual
19822 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19823 conditional breakpoint that suspends only after at least 5000
19824 simulated clock ticks.
19827 @subsection Atmel AVR
19830 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19831 following AVR-specific commands:
19834 @item info io_registers
19835 @kindex info io_registers@r{, AVR}
19836 @cindex I/O registers (Atmel AVR)
19837 This command displays information about the AVR I/O registers. For
19838 each register, @value{GDBN} prints its number and value.
19845 When configured for debugging CRIS, @value{GDBN} provides the
19846 following CRIS-specific commands:
19849 @item set cris-version @var{ver}
19850 @cindex CRIS version
19851 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19852 The CRIS version affects register names and sizes. This command is useful in
19853 case autodetection of the CRIS version fails.
19855 @item show cris-version
19856 Show the current CRIS version.
19858 @item set cris-dwarf2-cfi
19859 @cindex DWARF-2 CFI and CRIS
19860 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19861 Change to @samp{off} when using @code{gcc-cris} whose version is below
19864 @item show cris-dwarf2-cfi
19865 Show the current state of using DWARF-2 CFI.
19867 @item set cris-mode @var{mode}
19869 Set the current CRIS mode to @var{mode}. It should only be changed when
19870 debugging in guru mode, in which case it should be set to
19871 @samp{guru} (the default is @samp{normal}).
19873 @item show cris-mode
19874 Show the current CRIS mode.
19878 @subsection Renesas Super-H
19881 For the Renesas Super-H processor, @value{GDBN} provides these
19886 @kindex regs@r{, Super-H}
19887 Show the values of all Super-H registers.
19889 @item set sh calling-convention @var{convention}
19890 @kindex set sh calling-convention
19891 Set the calling-convention used when calling functions from @value{GDBN}.
19892 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19893 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19894 convention. If the DWARF-2 information of the called function specifies
19895 that the function follows the Renesas calling convention, the function
19896 is called using the Renesas calling convention. If the calling convention
19897 is set to @samp{renesas}, the Renesas calling convention is always used,
19898 regardless of the DWARF-2 information. This can be used to override the
19899 default of @samp{gcc} if debug information is missing, or the compiler
19900 does not emit the DWARF-2 calling convention entry for a function.
19902 @item show sh calling-convention
19903 @kindex show sh calling-convention
19904 Show the current calling convention setting.
19909 @node Architectures
19910 @section Architectures
19912 This section describes characteristics of architectures that affect
19913 all uses of @value{GDBN} with the architecture, both native and cross.
19920 * HPPA:: HP PA architecture
19921 * SPU:: Cell Broadband Engine SPU architecture
19926 @subsection x86 Architecture-specific Issues
19929 @item set struct-convention @var{mode}
19930 @kindex set struct-convention
19931 @cindex struct return convention
19932 @cindex struct/union returned in registers
19933 Set the convention used by the inferior to return @code{struct}s and
19934 @code{union}s from functions to @var{mode}. Possible values of
19935 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19936 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19937 are returned on the stack, while @code{"reg"} means that a
19938 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19939 be returned in a register.
19941 @item show struct-convention
19942 @kindex show struct-convention
19943 Show the current setting of the convention to return @code{struct}s
19952 @kindex set rstack_high_address
19953 @cindex AMD 29K register stack
19954 @cindex register stack, AMD29K
19955 @item set rstack_high_address @var{address}
19956 On AMD 29000 family processors, registers are saved in a separate
19957 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19958 extent of this stack. Normally, @value{GDBN} just assumes that the
19959 stack is ``large enough''. This may result in @value{GDBN} referencing
19960 memory locations that do not exist. If necessary, you can get around
19961 this problem by specifying the ending address of the register stack with
19962 the @code{set rstack_high_address} command. The argument should be an
19963 address, which you probably want to precede with @samp{0x} to specify in
19966 @kindex show rstack_high_address
19967 @item show rstack_high_address
19968 Display the current limit of the register stack, on AMD 29000 family
19976 See the following section.
19981 @cindex stack on Alpha
19982 @cindex stack on MIPS
19983 @cindex Alpha stack
19985 Alpha- and MIPS-based computers use an unusual stack frame, which
19986 sometimes requires @value{GDBN} to search backward in the object code to
19987 find the beginning of a function.
19989 @cindex response time, MIPS debugging
19990 To improve response time (especially for embedded applications, where
19991 @value{GDBN} may be restricted to a slow serial line for this search)
19992 you may want to limit the size of this search, using one of these
19996 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19997 @item set heuristic-fence-post @var{limit}
19998 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19999 search for the beginning of a function. A value of @var{0} (the
20000 default) means there is no limit. However, except for @var{0}, the
20001 larger the limit the more bytes @code{heuristic-fence-post} must search
20002 and therefore the longer it takes to run. You should only need to use
20003 this command when debugging a stripped executable.
20005 @item show heuristic-fence-post
20006 Display the current limit.
20010 These commands are available @emph{only} when @value{GDBN} is configured
20011 for debugging programs on Alpha or MIPS processors.
20013 Several MIPS-specific commands are available when debugging MIPS
20017 @item set mips abi @var{arg}
20018 @kindex set mips abi
20019 @cindex set ABI for MIPS
20020 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20021 values of @var{arg} are:
20025 The default ABI associated with the current binary (this is the
20035 @item show mips abi
20036 @kindex show mips abi
20037 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20040 @itemx show mipsfpu
20041 @xref{MIPS Embedded, set mipsfpu}.
20043 @item set mips mask-address @var{arg}
20044 @kindex set mips mask-address
20045 @cindex MIPS addresses, masking
20046 This command determines whether the most-significant 32 bits of 64-bit
20047 MIPS addresses are masked off. The argument @var{arg} can be
20048 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20049 setting, which lets @value{GDBN} determine the correct value.
20051 @item show mips mask-address
20052 @kindex show mips mask-address
20053 Show whether the upper 32 bits of MIPS addresses are masked off or
20056 @item set remote-mips64-transfers-32bit-regs
20057 @kindex set remote-mips64-transfers-32bit-regs
20058 This command controls compatibility with 64-bit MIPS targets that
20059 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20060 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20061 and 64 bits for other registers, set this option to @samp{on}.
20063 @item show remote-mips64-transfers-32bit-regs
20064 @kindex show remote-mips64-transfers-32bit-regs
20065 Show the current setting of compatibility with older MIPS 64 targets.
20067 @item set debug mips
20068 @kindex set debug mips
20069 This command turns on and off debugging messages for the MIPS-specific
20070 target code in @value{GDBN}.
20072 @item show debug mips
20073 @kindex show debug mips
20074 Show the current setting of MIPS debugging messages.
20080 @cindex HPPA support
20082 When @value{GDBN} is debugging the HP PA architecture, it provides the
20083 following special commands:
20086 @item set debug hppa
20087 @kindex set debug hppa
20088 This command determines whether HPPA architecture-specific debugging
20089 messages are to be displayed.
20091 @item show debug hppa
20092 Show whether HPPA debugging messages are displayed.
20094 @item maint print unwind @var{address}
20095 @kindex maint print unwind@r{, HPPA}
20096 This command displays the contents of the unwind table entry at the
20097 given @var{address}.
20103 @subsection Cell Broadband Engine SPU architecture
20104 @cindex Cell Broadband Engine
20107 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20108 it provides the following special commands:
20111 @item info spu event
20113 Display SPU event facility status. Shows current event mask
20114 and pending event status.
20116 @item info spu signal
20117 Display SPU signal notification facility status. Shows pending
20118 signal-control word and signal notification mode of both signal
20119 notification channels.
20121 @item info spu mailbox
20122 Display SPU mailbox facility status. Shows all pending entries,
20123 in order of processing, in each of the SPU Write Outbound,
20124 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20127 Display MFC DMA status. Shows all pending commands in the MFC
20128 DMA queue. For each entry, opcode, tag, class IDs, effective
20129 and local store addresses and transfer size are shown.
20131 @item info spu proxydma
20132 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20133 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20134 and local store addresses and transfer size are shown.
20138 When @value{GDBN} is debugging a combined PowerPC/SPU application
20139 on the Cell Broadband Engine, it provides in addition the following
20143 @item set spu stop-on-load @var{arg}
20145 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20146 will give control to the user when a new SPE thread enters its @code{main}
20147 function. The default is @code{off}.
20149 @item show spu stop-on-load
20151 Show whether to stop for new SPE threads.
20153 @item set spu auto-flush-cache @var{arg}
20154 Set whether to automatically flush the software-managed cache. When set to
20155 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20156 cache to be flushed whenever SPE execution stops. This provides a consistent
20157 view of PowerPC memory that is accessed via the cache. If an application
20158 does not use the software-managed cache, this option has no effect.
20160 @item show spu auto-flush-cache
20161 Show whether to automatically flush the software-managed cache.
20166 @subsection PowerPC
20167 @cindex PowerPC architecture
20169 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20170 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20171 numbers stored in the floating point registers. These values must be stored
20172 in two consecutive registers, always starting at an even register like
20173 @code{f0} or @code{f2}.
20175 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20176 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20177 @code{f2} and @code{f3} for @code{$dl1} and so on.
20179 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20180 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20183 @node Controlling GDB
20184 @chapter Controlling @value{GDBN}
20186 You can alter the way @value{GDBN} interacts with you by using the
20187 @code{set} command. For commands controlling how @value{GDBN} displays
20188 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20193 * Editing:: Command editing
20194 * Command History:: Command history
20195 * Screen Size:: Screen size
20196 * Numbers:: Numbers
20197 * ABI:: Configuring the current ABI
20198 * Messages/Warnings:: Optional warnings and messages
20199 * Debugging Output:: Optional messages about internal happenings
20200 * Other Misc Settings:: Other Miscellaneous Settings
20208 @value{GDBN} indicates its readiness to read a command by printing a string
20209 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20210 can change the prompt string with the @code{set prompt} command. For
20211 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20212 the prompt in one of the @value{GDBN} sessions so that you can always tell
20213 which one you are talking to.
20215 @emph{Note:} @code{set prompt} does not add a space for you after the
20216 prompt you set. This allows you to set a prompt which ends in a space
20217 or a prompt that does not.
20221 @item set prompt @var{newprompt}
20222 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20224 @kindex show prompt
20226 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20229 Versions of @value{GDBN} that ship with Python scripting enabled have
20230 prompt extensions. The commands for interacting with these extensions
20234 @kindex set extended-prompt
20235 @item set extended-prompt @var{prompt}
20236 Set an extended prompt that allows for substitutions.
20237 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20238 substitution. Any escape sequences specified as part of the prompt
20239 string are replaced with the corresponding strings each time the prompt
20245 set extended-prompt Current working directory: \w (gdb)
20248 Note that when an extended-prompt is set, it takes control of the
20249 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20251 @kindex show extended-prompt
20252 @item show extended-prompt
20253 Prints the extended prompt. Any escape sequences specified as part of
20254 the prompt string with @code{set extended-prompt}, are replaced with the
20255 corresponding strings each time the prompt is displayed.
20259 @section Command Editing
20261 @cindex command line editing
20263 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20264 @sc{gnu} library provides consistent behavior for programs which provide a
20265 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20266 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20267 substitution, and a storage and recall of command history across
20268 debugging sessions.
20270 You may control the behavior of command line editing in @value{GDBN} with the
20271 command @code{set}.
20274 @kindex set editing
20277 @itemx set editing on
20278 Enable command line editing (enabled by default).
20280 @item set editing off
20281 Disable command line editing.
20283 @kindex show editing
20285 Show whether command line editing is enabled.
20288 @ifset SYSTEM_READLINE
20289 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20291 @ifclear SYSTEM_READLINE
20292 @xref{Command Line Editing},
20294 for more details about the Readline
20295 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20296 encouraged to read that chapter.
20298 @node Command History
20299 @section Command History
20300 @cindex command history
20302 @value{GDBN} can keep track of the commands you type during your
20303 debugging sessions, so that you can be certain of precisely what
20304 happened. Use these commands to manage the @value{GDBN} command
20307 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20308 package, to provide the history facility.
20309 @ifset SYSTEM_READLINE
20310 @xref{Using History Interactively, , , history, GNU History Library},
20312 @ifclear SYSTEM_READLINE
20313 @xref{Using History Interactively},
20315 for the detailed description of the History library.
20317 To issue a command to @value{GDBN} without affecting certain aspects of
20318 the state which is seen by users, prefix it with @samp{server }
20319 (@pxref{Server Prefix}). This
20320 means that this command will not affect the command history, nor will it
20321 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20322 pressed on a line by itself.
20324 @cindex @code{server}, command prefix
20325 The server prefix does not affect the recording of values into the value
20326 history; to print a value without recording it into the value history,
20327 use the @code{output} command instead of the @code{print} command.
20329 Here is the description of @value{GDBN} commands related to command
20333 @cindex history substitution
20334 @cindex history file
20335 @kindex set history filename
20336 @cindex @env{GDBHISTFILE}, environment variable
20337 @item set history filename @var{fname}
20338 Set the name of the @value{GDBN} command history file to @var{fname}.
20339 This is the file where @value{GDBN} reads an initial command history
20340 list, and where it writes the command history from this session when it
20341 exits. You can access this list through history expansion or through
20342 the history command editing characters listed below. This file defaults
20343 to the value of the environment variable @code{GDBHISTFILE}, or to
20344 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20347 @cindex save command history
20348 @kindex set history save
20349 @item set history save
20350 @itemx set history save on
20351 Record command history in a file, whose name may be specified with the
20352 @code{set history filename} command. By default, this option is disabled.
20354 @item set history save off
20355 Stop recording command history in a file.
20357 @cindex history size
20358 @kindex set history size
20359 @cindex @env{HISTSIZE}, environment variable
20360 @item set history size @var{size}
20361 Set the number of commands which @value{GDBN} keeps in its history list.
20362 This defaults to the value of the environment variable
20363 @code{HISTSIZE}, or to 256 if this variable is not set.
20366 History expansion assigns special meaning to the character @kbd{!}.
20367 @ifset SYSTEM_READLINE
20368 @xref{Event Designators, , , history, GNU History Library},
20370 @ifclear SYSTEM_READLINE
20371 @xref{Event Designators},
20375 @cindex history expansion, turn on/off
20376 Since @kbd{!} is also the logical not operator in C, history expansion
20377 is off by default. If you decide to enable history expansion with the
20378 @code{set history expansion on} command, you may sometimes need to
20379 follow @kbd{!} (when it is used as logical not, in an expression) with
20380 a space or a tab to prevent it from being expanded. The readline
20381 history facilities do not attempt substitution on the strings
20382 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20384 The commands to control history expansion are:
20387 @item set history expansion on
20388 @itemx set history expansion
20389 @kindex set history expansion
20390 Enable history expansion. History expansion is off by default.
20392 @item set history expansion off
20393 Disable history expansion.
20396 @kindex show history
20398 @itemx show history filename
20399 @itemx show history save
20400 @itemx show history size
20401 @itemx show history expansion
20402 These commands display the state of the @value{GDBN} history parameters.
20403 @code{show history} by itself displays all four states.
20408 @kindex show commands
20409 @cindex show last commands
20410 @cindex display command history
20411 @item show commands
20412 Display the last ten commands in the command history.
20414 @item show commands @var{n}
20415 Print ten commands centered on command number @var{n}.
20417 @item show commands +
20418 Print ten commands just after the commands last printed.
20422 @section Screen Size
20423 @cindex size of screen
20424 @cindex pauses in output
20426 Certain commands to @value{GDBN} may produce large amounts of
20427 information output to the screen. To help you read all of it,
20428 @value{GDBN} pauses and asks you for input at the end of each page of
20429 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20430 to discard the remaining output. Also, the screen width setting
20431 determines when to wrap lines of output. Depending on what is being
20432 printed, @value{GDBN} tries to break the line at a readable place,
20433 rather than simply letting it overflow onto the following line.
20435 Normally @value{GDBN} knows the size of the screen from the terminal
20436 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20437 together with the value of the @code{TERM} environment variable and the
20438 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20439 you can override it with the @code{set height} and @code{set
20446 @kindex show height
20447 @item set height @var{lpp}
20449 @itemx set width @var{cpl}
20451 These @code{set} commands specify a screen height of @var{lpp} lines and
20452 a screen width of @var{cpl} characters. The associated @code{show}
20453 commands display the current settings.
20455 If you specify a height of zero lines, @value{GDBN} does not pause during
20456 output no matter how long the output is. This is useful if output is to a
20457 file or to an editor buffer.
20459 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20460 from wrapping its output.
20462 @item set pagination on
20463 @itemx set pagination off
20464 @kindex set pagination
20465 Turn the output pagination on or off; the default is on. Turning
20466 pagination off is the alternative to @code{set height 0}. Note that
20467 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20468 Options, -batch}) also automatically disables pagination.
20470 @item show pagination
20471 @kindex show pagination
20472 Show the current pagination mode.
20477 @cindex number representation
20478 @cindex entering numbers
20480 You can always enter numbers in octal, decimal, or hexadecimal in
20481 @value{GDBN} by the usual conventions: octal numbers begin with
20482 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20483 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20484 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20485 10; likewise, the default display for numbers---when no particular
20486 format is specified---is base 10. You can change the default base for
20487 both input and output with the commands described below.
20490 @kindex set input-radix
20491 @item set input-radix @var{base}
20492 Set the default base for numeric input. Supported choices
20493 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20494 specified either unambiguously or using the current input radix; for
20498 set input-radix 012
20499 set input-radix 10.
20500 set input-radix 0xa
20504 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20505 leaves the input radix unchanged, no matter what it was, since
20506 @samp{10}, being without any leading or trailing signs of its base, is
20507 interpreted in the current radix. Thus, if the current radix is 16,
20508 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20511 @kindex set output-radix
20512 @item set output-radix @var{base}
20513 Set the default base for numeric display. Supported choices
20514 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20515 specified either unambiguously or using the current input radix.
20517 @kindex show input-radix
20518 @item show input-radix
20519 Display the current default base for numeric input.
20521 @kindex show output-radix
20522 @item show output-radix
20523 Display the current default base for numeric display.
20525 @item set radix @r{[}@var{base}@r{]}
20529 These commands set and show the default base for both input and output
20530 of numbers. @code{set radix} sets the radix of input and output to
20531 the same base; without an argument, it resets the radix back to its
20532 default value of 10.
20537 @section Configuring the Current ABI
20539 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20540 application automatically. However, sometimes you need to override its
20541 conclusions. Use these commands to manage @value{GDBN}'s view of the
20548 One @value{GDBN} configuration can debug binaries for multiple operating
20549 system targets, either via remote debugging or native emulation.
20550 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20551 but you can override its conclusion using the @code{set osabi} command.
20552 One example where this is useful is in debugging of binaries which use
20553 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20554 not have the same identifying marks that the standard C library for your
20559 Show the OS ABI currently in use.
20562 With no argument, show the list of registered available OS ABI's.
20564 @item set osabi @var{abi}
20565 Set the current OS ABI to @var{abi}.
20568 @cindex float promotion
20570 Generally, the way that an argument of type @code{float} is passed to a
20571 function depends on whether the function is prototyped. For a prototyped
20572 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20573 according to the architecture's convention for @code{float}. For unprototyped
20574 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20575 @code{double} and then passed.
20577 Unfortunately, some forms of debug information do not reliably indicate whether
20578 a function is prototyped. If @value{GDBN} calls a function that is not marked
20579 as prototyped, it consults @kbd{set coerce-float-to-double}.
20582 @kindex set coerce-float-to-double
20583 @item set coerce-float-to-double
20584 @itemx set coerce-float-to-double on
20585 Arguments of type @code{float} will be promoted to @code{double} when passed
20586 to an unprototyped function. This is the default setting.
20588 @item set coerce-float-to-double off
20589 Arguments of type @code{float} will be passed directly to unprototyped
20592 @kindex show coerce-float-to-double
20593 @item show coerce-float-to-double
20594 Show the current setting of promoting @code{float} to @code{double}.
20598 @kindex show cp-abi
20599 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20600 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20601 used to build your application. @value{GDBN} only fully supports
20602 programs with a single C@t{++} ABI; if your program contains code using
20603 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20604 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20605 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20606 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20607 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20608 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20613 Show the C@t{++} ABI currently in use.
20616 With no argument, show the list of supported C@t{++} ABI's.
20618 @item set cp-abi @var{abi}
20619 @itemx set cp-abi auto
20620 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20623 @node Messages/Warnings
20624 @section Optional Warnings and Messages
20626 @cindex verbose operation
20627 @cindex optional warnings
20628 By default, @value{GDBN} is silent about its inner workings. If you are
20629 running on a slow machine, you may want to use the @code{set verbose}
20630 command. This makes @value{GDBN} tell you when it does a lengthy
20631 internal operation, so you will not think it has crashed.
20633 Currently, the messages controlled by @code{set verbose} are those
20634 which announce that the symbol table for a source file is being read;
20635 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20638 @kindex set verbose
20639 @item set verbose on
20640 Enables @value{GDBN} output of certain informational messages.
20642 @item set verbose off
20643 Disables @value{GDBN} output of certain informational messages.
20645 @kindex show verbose
20647 Displays whether @code{set verbose} is on or off.
20650 By default, if @value{GDBN} encounters bugs in the symbol table of an
20651 object file, it is silent; but if you are debugging a compiler, you may
20652 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20657 @kindex set complaints
20658 @item set complaints @var{limit}
20659 Permits @value{GDBN} to output @var{limit} complaints about each type of
20660 unusual symbols before becoming silent about the problem. Set
20661 @var{limit} to zero to suppress all complaints; set it to a large number
20662 to prevent complaints from being suppressed.
20664 @kindex show complaints
20665 @item show complaints
20666 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20670 @anchor{confirmation requests}
20671 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20672 lot of stupid questions to confirm certain commands. For example, if
20673 you try to run a program which is already running:
20677 The program being debugged has been started already.
20678 Start it from the beginning? (y or n)
20681 If you are willing to unflinchingly face the consequences of your own
20682 commands, you can disable this ``feature'':
20686 @kindex set confirm
20688 @cindex confirmation
20689 @cindex stupid questions
20690 @item set confirm off
20691 Disables confirmation requests. Note that running @value{GDBN} with
20692 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20693 automatically disables confirmation requests.
20695 @item set confirm on
20696 Enables confirmation requests (the default).
20698 @kindex show confirm
20700 Displays state of confirmation requests.
20704 @cindex command tracing
20705 If you need to debug user-defined commands or sourced files you may find it
20706 useful to enable @dfn{command tracing}. In this mode each command will be
20707 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20708 quantity denoting the call depth of each command.
20711 @kindex set trace-commands
20712 @cindex command scripts, debugging
20713 @item set trace-commands on
20714 Enable command tracing.
20715 @item set trace-commands off
20716 Disable command tracing.
20717 @item show trace-commands
20718 Display the current state of command tracing.
20721 @node Debugging Output
20722 @section Optional Messages about Internal Happenings
20723 @cindex optional debugging messages
20725 @value{GDBN} has commands that enable optional debugging messages from
20726 various @value{GDBN} subsystems; normally these commands are of
20727 interest to @value{GDBN} maintainers, or when reporting a bug. This
20728 section documents those commands.
20731 @kindex set exec-done-display
20732 @item set exec-done-display
20733 Turns on or off the notification of asynchronous commands'
20734 completion. When on, @value{GDBN} will print a message when an
20735 asynchronous command finishes its execution. The default is off.
20736 @kindex show exec-done-display
20737 @item show exec-done-display
20738 Displays the current setting of asynchronous command completion
20741 @cindex gdbarch debugging info
20742 @cindex architecture debugging info
20743 @item set debug arch
20744 Turns on or off display of gdbarch debugging info. The default is off
20746 @item show debug arch
20747 Displays the current state of displaying gdbarch debugging info.
20748 @item set debug aix-thread
20749 @cindex AIX threads
20750 Display debugging messages about inner workings of the AIX thread
20752 @item show debug aix-thread
20753 Show the current state of AIX thread debugging info display.
20754 @item set debug check-physname
20756 Check the results of the ``physname'' computation. When reading DWARF
20757 debugging information for C@t{++}, @value{GDBN} attempts to compute
20758 each entity's name. @value{GDBN} can do this computation in two
20759 different ways, depending on exactly what information is present.
20760 When enabled, this setting causes @value{GDBN} to compute the names
20761 both ways and display any discrepancies.
20762 @item show debug check-physname
20763 Show the current state of ``physname'' checking.
20764 @item set debug dwarf2-die
20765 @cindex DWARF2 DIEs
20766 Dump DWARF2 DIEs after they are read in.
20767 The value is the number of nesting levels to print.
20768 A value of zero turns off the display.
20769 @item show debug dwarf2-die
20770 Show the current state of DWARF2 DIE debugging.
20771 @item set debug displaced
20772 @cindex displaced stepping debugging info
20773 Turns on or off display of @value{GDBN} debugging info for the
20774 displaced stepping support. The default is off.
20775 @item show debug displaced
20776 Displays the current state of displaying @value{GDBN} debugging info
20777 related to displaced stepping.
20778 @item set debug event
20779 @cindex event debugging info
20780 Turns on or off display of @value{GDBN} event debugging info. The
20782 @item show debug event
20783 Displays the current state of displaying @value{GDBN} event debugging
20785 @item set debug expression
20786 @cindex expression debugging info
20787 Turns on or off display of debugging info about @value{GDBN}
20788 expression parsing. The default is off.
20789 @item show debug expression
20790 Displays the current state of displaying debugging info about
20791 @value{GDBN} expression parsing.
20792 @item set debug frame
20793 @cindex frame debugging info
20794 Turns on or off display of @value{GDBN} frame debugging info. The
20796 @item show debug frame
20797 Displays the current state of displaying @value{GDBN} frame debugging
20799 @item set debug gnu-nat
20800 @cindex @sc{gnu}/Hurd debug messages
20801 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20802 @item show debug gnu-nat
20803 Show the current state of @sc{gnu}/Hurd debugging messages.
20804 @item set debug infrun
20805 @cindex inferior debugging info
20806 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20807 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20808 for implementing operations such as single-stepping the inferior.
20809 @item show debug infrun
20810 Displays the current state of @value{GDBN} inferior debugging.
20811 @item set debug jit
20812 @cindex just-in-time compilation, debugging messages
20813 Turns on or off debugging messages from JIT debug support.
20814 @item show debug jit
20815 Displays the current state of @value{GDBN} JIT debugging.
20816 @item set debug lin-lwp
20817 @cindex @sc{gnu}/Linux LWP debug messages
20818 @cindex Linux lightweight processes
20819 Turns on or off debugging messages from the Linux LWP debug support.
20820 @item show debug lin-lwp
20821 Show the current state of Linux LWP debugging messages.
20822 @item set debug observer
20823 @cindex observer debugging info
20824 Turns on or off display of @value{GDBN} observer debugging. This
20825 includes info such as the notification of observable events.
20826 @item show debug observer
20827 Displays the current state of observer debugging.
20828 @item set debug overload
20829 @cindex C@t{++} overload debugging info
20830 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20831 info. This includes info such as ranking of functions, etc. The default
20833 @item show debug overload
20834 Displays the current state of displaying @value{GDBN} C@t{++} overload
20836 @cindex expression parser, debugging info
20837 @cindex debug expression parser
20838 @item set debug parser
20839 Turns on or off the display of expression parser debugging output.
20840 Internally, this sets the @code{yydebug} variable in the expression
20841 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20842 details. The default is off.
20843 @item show debug parser
20844 Show the current state of expression parser debugging.
20845 @cindex packets, reporting on stdout
20846 @cindex serial connections, debugging
20847 @cindex debug remote protocol
20848 @cindex remote protocol debugging
20849 @cindex display remote packets
20850 @item set debug remote
20851 Turns on or off display of reports on all packets sent back and forth across
20852 the serial line to the remote machine. The info is printed on the
20853 @value{GDBN} standard output stream. The default is off.
20854 @item show debug remote
20855 Displays the state of display of remote packets.
20856 @item set debug serial
20857 Turns on or off display of @value{GDBN} serial debugging info. The
20859 @item show debug serial
20860 Displays the current state of displaying @value{GDBN} serial debugging
20862 @item set debug solib-frv
20863 @cindex FR-V shared-library debugging
20864 Turns on or off debugging messages for FR-V shared-library code.
20865 @item show debug solib-frv
20866 Display the current state of FR-V shared-library code debugging
20868 @item set debug target
20869 @cindex target debugging info
20870 Turns on or off display of @value{GDBN} target debugging info. This info
20871 includes what is going on at the target level of GDB, as it happens. The
20872 default is 0. Set it to 1 to track events, and to 2 to also track the
20873 value of large memory transfers. Changes to this flag do not take effect
20874 until the next time you connect to a target or use the @code{run} command.
20875 @item show debug target
20876 Displays the current state of displaying @value{GDBN} target debugging
20878 @item set debug timestamp
20879 @cindex timestampping debugging info
20880 Turns on or off display of timestamps with @value{GDBN} debugging info.
20881 When enabled, seconds and microseconds are displayed before each debugging
20883 @item show debug timestamp
20884 Displays the current state of displaying timestamps with @value{GDBN}
20886 @item set debugvarobj
20887 @cindex variable object debugging info
20888 Turns on or off display of @value{GDBN} variable object debugging
20889 info. The default is off.
20890 @item show debugvarobj
20891 Displays the current state of displaying @value{GDBN} variable object
20893 @item set debug xml
20894 @cindex XML parser debugging
20895 Turns on or off debugging messages for built-in XML parsers.
20896 @item show debug xml
20897 Displays the current state of XML debugging messages.
20900 @node Other Misc Settings
20901 @section Other Miscellaneous Settings
20902 @cindex miscellaneous settings
20905 @kindex set interactive-mode
20906 @item set interactive-mode
20907 If @code{on}, forces @value{GDBN} to assume that GDB was started
20908 in a terminal. In practice, this means that @value{GDBN} should wait
20909 for the user to answer queries generated by commands entered at
20910 the command prompt. If @code{off}, forces @value{GDBN} to operate
20911 in the opposite mode, and it uses the default answers to all queries.
20912 If @code{auto} (the default), @value{GDBN} tries to determine whether
20913 its standard input is a terminal, and works in interactive-mode if it
20914 is, non-interactively otherwise.
20916 In the vast majority of cases, the debugger should be able to guess
20917 correctly which mode should be used. But this setting can be useful
20918 in certain specific cases, such as running a MinGW @value{GDBN}
20919 inside a cygwin window.
20921 @kindex show interactive-mode
20922 @item show interactive-mode
20923 Displays whether the debugger is operating in interactive mode or not.
20926 @node Extending GDB
20927 @chapter Extending @value{GDBN}
20928 @cindex extending GDB
20930 @value{GDBN} provides three mechanisms for extension. The first is based
20931 on composition of @value{GDBN} commands, the second is based on the
20932 Python scripting language, and the third is for defining new aliases of
20935 To facilitate the use of the first two extensions, @value{GDBN} is capable
20936 of evaluating the contents of a file. When doing so, @value{GDBN}
20937 can recognize which scripting language is being used by looking at
20938 the filename extension. Files with an unrecognized filename extension
20939 are always treated as a @value{GDBN} Command Files.
20940 @xref{Command Files,, Command files}.
20942 You can control how @value{GDBN} evaluates these files with the following
20946 @kindex set script-extension
20947 @kindex show script-extension
20948 @item set script-extension off
20949 All scripts are always evaluated as @value{GDBN} Command Files.
20951 @item set script-extension soft
20952 The debugger determines the scripting language based on filename
20953 extension. If this scripting language is supported, @value{GDBN}
20954 evaluates the script using that language. Otherwise, it evaluates
20955 the file as a @value{GDBN} Command File.
20957 @item set script-extension strict
20958 The debugger determines the scripting language based on filename
20959 extension, and evaluates the script using that language. If the
20960 language is not supported, then the evaluation fails.
20962 @item show script-extension
20963 Display the current value of the @code{script-extension} option.
20968 * Sequences:: Canned Sequences of Commands
20969 * Python:: Scripting @value{GDBN} using Python
20970 * Aliases:: Creating new spellings of existing commands
20974 @section Canned Sequences of Commands
20976 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20977 Command Lists}), @value{GDBN} provides two ways to store sequences of
20978 commands for execution as a unit: user-defined commands and command
20982 * Define:: How to define your own commands
20983 * Hooks:: Hooks for user-defined commands
20984 * Command Files:: How to write scripts of commands to be stored in a file
20985 * Output:: Commands for controlled output
20989 @subsection User-defined Commands
20991 @cindex user-defined command
20992 @cindex arguments, to user-defined commands
20993 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20994 which you assign a new name as a command. This is done with the
20995 @code{define} command. User commands may accept up to 10 arguments
20996 separated by whitespace. Arguments are accessed within the user command
20997 via @code{$arg0@dots{}$arg9}. A trivial example:
21001 print $arg0 + $arg1 + $arg2
21006 To execute the command use:
21013 This defines the command @code{adder}, which prints the sum of
21014 its three arguments. Note the arguments are text substitutions, so they may
21015 reference variables, use complex expressions, or even perform inferior
21018 @cindex argument count in user-defined commands
21019 @cindex how many arguments (user-defined commands)
21020 In addition, @code{$argc} may be used to find out how many arguments have
21021 been passed. This expands to a number in the range 0@dots{}10.
21026 print $arg0 + $arg1
21029 print $arg0 + $arg1 + $arg2
21037 @item define @var{commandname}
21038 Define a command named @var{commandname}. If there is already a command
21039 by that name, you are asked to confirm that you want to redefine it.
21040 @var{commandname} may be a bare command name consisting of letters,
21041 numbers, dashes, and underscores. It may also start with any predefined
21042 prefix command. For example, @samp{define target my-target} creates
21043 a user-defined @samp{target my-target} command.
21045 The definition of the command is made up of other @value{GDBN} command lines,
21046 which are given following the @code{define} command. The end of these
21047 commands is marked by a line containing @code{end}.
21050 @kindex end@r{ (user-defined commands)}
21051 @item document @var{commandname}
21052 Document the user-defined command @var{commandname}, so that it can be
21053 accessed by @code{help}. The command @var{commandname} must already be
21054 defined. This command reads lines of documentation just as @code{define}
21055 reads the lines of the command definition, ending with @code{end}.
21056 After the @code{document} command is finished, @code{help} on command
21057 @var{commandname} displays the documentation you have written.
21059 You may use the @code{document} command again to change the
21060 documentation of a command. Redefining the command with @code{define}
21061 does not change the documentation.
21063 @kindex dont-repeat
21064 @cindex don't repeat command
21066 Used inside a user-defined command, this tells @value{GDBN} that this
21067 command should not be repeated when the user hits @key{RET}
21068 (@pxref{Command Syntax, repeat last command}).
21070 @kindex help user-defined
21071 @item help user-defined
21072 List all user-defined commands, with the first line of the documentation
21077 @itemx show user @var{commandname}
21078 Display the @value{GDBN} commands used to define @var{commandname} (but
21079 not its documentation). If no @var{commandname} is given, display the
21080 definitions for all user-defined commands.
21082 @cindex infinite recursion in user-defined commands
21083 @kindex show max-user-call-depth
21084 @kindex set max-user-call-depth
21085 @item show max-user-call-depth
21086 @itemx set max-user-call-depth
21087 The value of @code{max-user-call-depth} controls how many recursion
21088 levels are allowed in user-defined commands before @value{GDBN} suspects an
21089 infinite recursion and aborts the command.
21092 In addition to the above commands, user-defined commands frequently
21093 use control flow commands, described in @ref{Command Files}.
21095 When user-defined commands are executed, the
21096 commands of the definition are not printed. An error in any command
21097 stops execution of the user-defined command.
21099 If used interactively, commands that would ask for confirmation proceed
21100 without asking when used inside a user-defined command. Many @value{GDBN}
21101 commands that normally print messages to say what they are doing omit the
21102 messages when used in a user-defined command.
21105 @subsection User-defined Command Hooks
21106 @cindex command hooks
21107 @cindex hooks, for commands
21108 @cindex hooks, pre-command
21111 You may define @dfn{hooks}, which are a special kind of user-defined
21112 command. Whenever you run the command @samp{foo}, if the user-defined
21113 command @samp{hook-foo} exists, it is executed (with no arguments)
21114 before that command.
21116 @cindex hooks, post-command
21118 A hook may also be defined which is run after the command you executed.
21119 Whenever you run the command @samp{foo}, if the user-defined command
21120 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21121 that command. Post-execution hooks may exist simultaneously with
21122 pre-execution hooks, for the same command.
21124 It is valid for a hook to call the command which it hooks. If this
21125 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21127 @c It would be nice if hookpost could be passed a parameter indicating
21128 @c if the command it hooks executed properly or not. FIXME!
21130 @kindex stop@r{, a pseudo-command}
21131 In addition, a pseudo-command, @samp{stop} exists. Defining
21132 (@samp{hook-stop}) makes the associated commands execute every time
21133 execution stops in your program: before breakpoint commands are run,
21134 displays are printed, or the stack frame is printed.
21136 For example, to ignore @code{SIGALRM} signals while
21137 single-stepping, but treat them normally during normal execution,
21142 handle SIGALRM nopass
21146 handle SIGALRM pass
21149 define hook-continue
21150 handle SIGALRM pass
21154 As a further example, to hook at the beginning and end of the @code{echo}
21155 command, and to add extra text to the beginning and end of the message,
21163 define hookpost-echo
21167 (@value{GDBP}) echo Hello World
21168 <<<---Hello World--->>>
21173 You can define a hook for any single-word command in @value{GDBN}, but
21174 not for command aliases; you should define a hook for the basic command
21175 name, e.g.@: @code{backtrace} rather than @code{bt}.
21176 @c FIXME! So how does Joe User discover whether a command is an alias
21178 You can hook a multi-word command by adding @code{hook-} or
21179 @code{hookpost-} to the last word of the command, e.g.@:
21180 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21182 If an error occurs during the execution of your hook, execution of
21183 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21184 (before the command that you actually typed had a chance to run).
21186 If you try to define a hook which does not match any known command, you
21187 get a warning from the @code{define} command.
21189 @node Command Files
21190 @subsection Command Files
21192 @cindex command files
21193 @cindex scripting commands
21194 A command file for @value{GDBN} is a text file made of lines that are
21195 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21196 also be included. An empty line in a command file does nothing; it
21197 does not mean to repeat the last command, as it would from the
21200 You can request the execution of a command file with the @code{source}
21201 command. Note that the @code{source} command is also used to evaluate
21202 scripts that are not Command Files. The exact behavior can be configured
21203 using the @code{script-extension} setting.
21204 @xref{Extending GDB,, Extending GDB}.
21208 @cindex execute commands from a file
21209 @item source [-s] [-v] @var{filename}
21210 Execute the command file @var{filename}.
21213 The lines in a command file are generally executed sequentially,
21214 unless the order of execution is changed by one of the
21215 @emph{flow-control commands} described below. The commands are not
21216 printed as they are executed. An error in any command terminates
21217 execution of the command file and control is returned to the console.
21219 @value{GDBN} first searches for @var{filename} in the current directory.
21220 If the file is not found there, and @var{filename} does not specify a
21221 directory, then @value{GDBN} also looks for the file on the source search path
21222 (specified with the @samp{directory} command);
21223 except that @file{$cdir} is not searched because the compilation directory
21224 is not relevant to scripts.
21226 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21227 on the search path even if @var{filename} specifies a directory.
21228 The search is done by appending @var{filename} to each element of the
21229 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21230 and the search path contains @file{/home/user} then @value{GDBN} will
21231 look for the script @file{/home/user/mylib/myscript}.
21232 The search is also done if @var{filename} is an absolute path.
21233 For example, if @var{filename} is @file{/tmp/myscript} and
21234 the search path contains @file{/home/user} then @value{GDBN} will
21235 look for the script @file{/home/user/tmp/myscript}.
21236 For DOS-like systems, if @var{filename} contains a drive specification,
21237 it is stripped before concatenation. For example, if @var{filename} is
21238 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21239 will look for the script @file{c:/tmp/myscript}.
21241 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21242 each command as it is executed. The option must be given before
21243 @var{filename}, and is interpreted as part of the filename anywhere else.
21245 Commands that would ask for confirmation if used interactively proceed
21246 without asking when used in a command file. Many @value{GDBN} commands that
21247 normally print messages to say what they are doing omit the messages
21248 when called from command files.
21250 @value{GDBN} also accepts command input from standard input. In this
21251 mode, normal output goes to standard output and error output goes to
21252 standard error. Errors in a command file supplied on standard input do
21253 not terminate execution of the command file---execution continues with
21257 gdb < cmds > log 2>&1
21260 (The syntax above will vary depending on the shell used.) This example
21261 will execute commands from the file @file{cmds}. All output and errors
21262 would be directed to @file{log}.
21264 Since commands stored on command files tend to be more general than
21265 commands typed interactively, they frequently need to deal with
21266 complicated situations, such as different or unexpected values of
21267 variables and symbols, changes in how the program being debugged is
21268 built, etc. @value{GDBN} provides a set of flow-control commands to
21269 deal with these complexities. Using these commands, you can write
21270 complex scripts that loop over data structures, execute commands
21271 conditionally, etc.
21278 This command allows to include in your script conditionally executed
21279 commands. The @code{if} command takes a single argument, which is an
21280 expression to evaluate. It is followed by a series of commands that
21281 are executed only if the expression is true (its value is nonzero).
21282 There can then optionally be an @code{else} line, followed by a series
21283 of commands that are only executed if the expression was false. The
21284 end of the list is marked by a line containing @code{end}.
21288 This command allows to write loops. Its syntax is similar to
21289 @code{if}: the command takes a single argument, which is an expression
21290 to evaluate, and must be followed by the commands to execute, one per
21291 line, terminated by an @code{end}. These commands are called the
21292 @dfn{body} of the loop. The commands in the body of @code{while} are
21293 executed repeatedly as long as the expression evaluates to true.
21297 This command exits the @code{while} loop in whose body it is included.
21298 Execution of the script continues after that @code{while}s @code{end}
21301 @kindex loop_continue
21302 @item loop_continue
21303 This command skips the execution of the rest of the body of commands
21304 in the @code{while} loop in whose body it is included. Execution
21305 branches to the beginning of the @code{while} loop, where it evaluates
21306 the controlling expression.
21308 @kindex end@r{ (if/else/while commands)}
21310 Terminate the block of commands that are the body of @code{if},
21311 @code{else}, or @code{while} flow-control commands.
21316 @subsection Commands for Controlled Output
21318 During the execution of a command file or a user-defined command, normal
21319 @value{GDBN} output is suppressed; the only output that appears is what is
21320 explicitly printed by the commands in the definition. This section
21321 describes three commands useful for generating exactly the output you
21326 @item echo @var{text}
21327 @c I do not consider backslash-space a standard C escape sequence
21328 @c because it is not in ANSI.
21329 Print @var{text}. Nonprinting characters can be included in
21330 @var{text} using C escape sequences, such as @samp{\n} to print a
21331 newline. @strong{No newline is printed unless you specify one.}
21332 In addition to the standard C escape sequences, a backslash followed
21333 by a space stands for a space. This is useful for displaying a
21334 string with spaces at the beginning or the end, since leading and
21335 trailing spaces are otherwise trimmed from all arguments.
21336 To print @samp{@w{ }and foo =@w{ }}, use the command
21337 @samp{echo \@w{ }and foo = \@w{ }}.
21339 A backslash at the end of @var{text} can be used, as in C, to continue
21340 the command onto subsequent lines. For example,
21343 echo This is some text\n\
21344 which is continued\n\
21345 onto several lines.\n
21348 produces the same output as
21351 echo This is some text\n
21352 echo which is continued\n
21353 echo onto several lines.\n
21357 @item output @var{expression}
21358 Print the value of @var{expression} and nothing but that value: no
21359 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21360 value history either. @xref{Expressions, ,Expressions}, for more information
21363 @item output/@var{fmt} @var{expression}
21364 Print the value of @var{expression} in format @var{fmt}. You can use
21365 the same formats as for @code{print}. @xref{Output Formats,,Output
21366 Formats}, for more information.
21369 @item printf @var{template}, @var{expressions}@dots{}
21370 Print the values of one or more @var{expressions} under the control of
21371 the string @var{template}. To print several values, make
21372 @var{expressions} be a comma-separated list of individual expressions,
21373 which may be either numbers or pointers. Their values are printed as
21374 specified by @var{template}, exactly as a C program would do by
21375 executing the code below:
21378 printf (@var{template}, @var{expressions}@dots{});
21381 As in @code{C} @code{printf}, ordinary characters in @var{template}
21382 are printed verbatim, while @dfn{conversion specification} introduced
21383 by the @samp{%} character cause subsequent @var{expressions} to be
21384 evaluated, their values converted and formatted according to type and
21385 style information encoded in the conversion specifications, and then
21388 For example, you can print two values in hex like this:
21391 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21394 @code{printf} supports all the standard @code{C} conversion
21395 specifications, including the flags and modifiers between the @samp{%}
21396 character and the conversion letter, with the following exceptions:
21400 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21403 The modifier @samp{*} is not supported for specifying precision or
21407 The @samp{'} flag (for separation of digits into groups according to
21408 @code{LC_NUMERIC'}) is not supported.
21411 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21415 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21418 The conversion letters @samp{a} and @samp{A} are not supported.
21422 Note that the @samp{ll} type modifier is supported only if the
21423 underlying @code{C} implementation used to build @value{GDBN} supports
21424 the @code{long long int} type, and the @samp{L} type modifier is
21425 supported only if @code{long double} type is available.
21427 As in @code{C}, @code{printf} supports simple backslash-escape
21428 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21429 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21430 single character. Octal and hexadecimal escape sequences are not
21433 Additionally, @code{printf} supports conversion specifications for DFP
21434 (@dfn{Decimal Floating Point}) types using the following length modifiers
21435 together with a floating point specifier.
21440 @samp{H} for printing @code{Decimal32} types.
21443 @samp{D} for printing @code{Decimal64} types.
21446 @samp{DD} for printing @code{Decimal128} types.
21449 If the underlying @code{C} implementation used to build @value{GDBN} has
21450 support for the three length modifiers for DFP types, other modifiers
21451 such as width and precision will also be available for @value{GDBN} to use.
21453 In case there is no such @code{C} support, no additional modifiers will be
21454 available and the value will be printed in the standard way.
21456 Here's an example of printing DFP types using the above conversion letters:
21458 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21462 @item eval @var{template}, @var{expressions}@dots{}
21463 Convert the values of one or more @var{expressions} under the control of
21464 the string @var{template} to a command line, and call it.
21469 @section Scripting @value{GDBN} using Python
21470 @cindex python scripting
21471 @cindex scripting with python
21473 You can script @value{GDBN} using the @uref{http://www.python.org/,
21474 Python programming language}. This feature is available only if
21475 @value{GDBN} was configured using @option{--with-python}.
21477 @cindex python directory
21478 Python scripts used by @value{GDBN} should be installed in
21479 @file{@var{data-directory}/python}, where @var{data-directory} is
21480 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21481 This directory, known as the @dfn{python directory},
21482 is automatically added to the Python Search Path in order to allow
21483 the Python interpreter to locate all scripts installed at this location.
21485 Additionally, @value{GDBN} commands and convenience functions which
21486 are written in Python and are located in the
21487 @file{@var{data-directory}/python/gdb/command} or
21488 @file{@var{data-directory}/python/gdb/function} directories are
21489 automatically imported when @value{GDBN} starts.
21492 * Python Commands:: Accessing Python from @value{GDBN}.
21493 * Python API:: Accessing @value{GDBN} from Python.
21494 * Auto-loading:: Automatically loading Python code.
21495 * Python modules:: Python modules provided by @value{GDBN}.
21498 @node Python Commands
21499 @subsection Python Commands
21500 @cindex python commands
21501 @cindex commands to access python
21503 @value{GDBN} provides one command for accessing the Python interpreter,
21504 and one related setting:
21508 @item python @r{[}@var{code}@r{]}
21509 The @code{python} command can be used to evaluate Python code.
21511 If given an argument, the @code{python} command will evaluate the
21512 argument as a Python command. For example:
21515 (@value{GDBP}) python print 23
21519 If you do not provide an argument to @code{python}, it will act as a
21520 multi-line command, like @code{define}. In this case, the Python
21521 script is made up of subsequent command lines, given after the
21522 @code{python} command. This command list is terminated using a line
21523 containing @code{end}. For example:
21526 (@value{GDBP}) python
21528 End with a line saying just "end".
21534 @kindex set python print-stack
21535 @item set python print-stack
21536 By default, @value{GDBN} will print only the message component of a
21537 Python exception when an error occurs in a Python script. This can be
21538 controlled using @code{set python print-stack}: if @code{full}, then
21539 full Python stack printing is enabled; if @code{none}, then Python stack
21540 and message printing is disabled; if @code{message}, the default, only
21541 the message component of the error is printed.
21544 It is also possible to execute a Python script from the @value{GDBN}
21548 @item source @file{script-name}
21549 The script name must end with @samp{.py} and @value{GDBN} must be configured
21550 to recognize the script language based on filename extension using
21551 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21553 @item python execfile ("script-name")
21554 This method is based on the @code{execfile} Python built-in function,
21555 and thus is always available.
21559 @subsection Python API
21561 @cindex programming in python
21563 @cindex python stdout
21564 @cindex python pagination
21565 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21566 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21567 A Python program which outputs to one of these streams may have its
21568 output interrupted by the user (@pxref{Screen Size}). In this
21569 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21572 * Basic Python:: Basic Python Functions.
21573 * Exception Handling:: How Python exceptions are translated.
21574 * Values From Inferior:: Python representation of values.
21575 * Types In Python:: Python representation of types.
21576 * Pretty Printing API:: Pretty-printing values.
21577 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21578 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21579 * Inferiors In Python:: Python representation of inferiors (processes)
21580 * Events In Python:: Listening for events from @value{GDBN}.
21581 * Threads In Python:: Accessing inferior threads from Python.
21582 * Commands In Python:: Implementing new commands in Python.
21583 * Parameters In Python:: Adding new @value{GDBN} parameters.
21584 * Functions In Python:: Writing new convenience functions.
21585 * Progspaces In Python:: Program spaces.
21586 * Objfiles In Python:: Object files.
21587 * Frames In Python:: Accessing inferior stack frames from Python.
21588 * Blocks In Python:: Accessing frame blocks from Python.
21589 * Symbols In Python:: Python representation of symbols.
21590 * Symbol Tables In Python:: Python representation of symbol tables.
21591 * Lazy Strings In Python:: Python representation of lazy strings.
21592 * Breakpoints In Python:: Manipulating breakpoints using Python.
21593 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21598 @subsubsection Basic Python
21600 @cindex python functions
21601 @cindex python module
21603 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21604 methods and classes added by @value{GDBN} are placed in this module.
21605 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21606 use in all scripts evaluated by the @code{python} command.
21608 @findex gdb.PYTHONDIR
21609 @defvar gdb.PYTHONDIR
21610 A string containing the python directory (@pxref{Python}).
21613 @findex gdb.execute
21614 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21615 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21616 If a GDB exception happens while @var{command} runs, it is
21617 translated as described in @ref{Exception Handling,,Exception Handling}.
21619 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21620 command as having originated from the user invoking it interactively.
21621 It must be a boolean value. If omitted, it defaults to @code{False}.
21623 By default, any output produced by @var{command} is sent to
21624 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21625 @code{True}, then output will be collected by @code{gdb.execute} and
21626 returned as a string. The default is @code{False}, in which case the
21627 return value is @code{None}. If @var{to_string} is @code{True}, the
21628 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21629 and height, and its pagination will be disabled; @pxref{Screen Size}.
21632 @findex gdb.breakpoints
21633 @defun gdb.breakpoints ()
21634 Return a sequence holding all of @value{GDBN}'s breakpoints.
21635 @xref{Breakpoints In Python}, for more information.
21638 @findex gdb.parameter
21639 @defun gdb.parameter (parameter)
21640 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21641 string naming the parameter to look up; @var{parameter} may contain
21642 spaces if the parameter has a multi-part name. For example,
21643 @samp{print object} is a valid parameter name.
21645 If the named parameter does not exist, this function throws a
21646 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21647 parameter's value is converted to a Python value of the appropriate
21648 type, and returned.
21651 @findex gdb.history
21652 @defun gdb.history (number)
21653 Return a value from @value{GDBN}'s value history (@pxref{Value
21654 History}). @var{number} indicates which history element to return.
21655 If @var{number} is negative, then @value{GDBN} will take its absolute value
21656 and count backward from the last element (i.e., the most recent element) to
21657 find the value to return. If @var{number} is zero, then @value{GDBN} will
21658 return the most recent element. If the element specified by @var{number}
21659 doesn't exist in the value history, a @code{gdb.error} exception will be
21662 If no exception is raised, the return value is always an instance of
21663 @code{gdb.Value} (@pxref{Values From Inferior}).
21666 @findex gdb.parse_and_eval
21667 @defun gdb.parse_and_eval (expression)
21668 Parse @var{expression} as an expression in the current language,
21669 evaluate it, and return the result as a @code{gdb.Value}.
21670 @var{expression} must be a string.
21672 This function can be useful when implementing a new command
21673 (@pxref{Commands In Python}), as it provides a way to parse the
21674 command's argument as an expression. It is also useful simply to
21675 compute values, for example, it is the only way to get the value of a
21676 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21679 @findex gdb.post_event
21680 @defun gdb.post_event (event)
21681 Put @var{event}, a callable object taking no arguments, into
21682 @value{GDBN}'s internal event queue. This callable will be invoked at
21683 some later point, during @value{GDBN}'s event processing. Events
21684 posted using @code{post_event} will be run in the order in which they
21685 were posted; however, there is no way to know when they will be
21686 processed relative to other events inside @value{GDBN}.
21688 @value{GDBN} is not thread-safe. If your Python program uses multiple
21689 threads, you must be careful to only call @value{GDBN}-specific
21690 functions in the main @value{GDBN} thread. @code{post_event} ensures
21694 (@value{GDBP}) python
21698 > def __init__(self, message):
21699 > self.message = message;
21700 > def __call__(self):
21701 > gdb.write(self.message)
21703 >class MyThread1 (threading.Thread):
21705 > gdb.post_event(Writer("Hello "))
21707 >class MyThread2 (threading.Thread):
21709 > gdb.post_event(Writer("World\n"))
21711 >MyThread1().start()
21712 >MyThread2().start()
21714 (@value{GDBP}) Hello World
21719 @defun gdb.write (string @r{[}, stream{]})
21720 Print a string to @value{GDBN}'s paginated output stream. The
21721 optional @var{stream} determines the stream to print to. The default
21722 stream is @value{GDBN}'s standard output stream. Possible stream
21729 @value{GDBN}'s standard output stream.
21734 @value{GDBN}'s standard error stream.
21739 @value{GDBN}'s log stream (@pxref{Logging Output}).
21742 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21743 call this function and will automatically direct the output to the
21748 @defun gdb.flush ()
21749 Flush the buffer of a @value{GDBN} paginated stream so that the
21750 contents are displayed immediately. @value{GDBN} will flush the
21751 contents of a stream automatically when it encounters a newline in the
21752 buffer. The optional @var{stream} determines the stream to flush. The
21753 default stream is @value{GDBN}'s standard output stream. Possible
21760 @value{GDBN}'s standard output stream.
21765 @value{GDBN}'s standard error stream.
21770 @value{GDBN}'s log stream (@pxref{Logging Output}).
21774 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21775 call this function for the relevant stream.
21778 @findex gdb.target_charset
21779 @defun gdb.target_charset ()
21780 Return the name of the current target character set (@pxref{Character
21781 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21782 that @samp{auto} is never returned.
21785 @findex gdb.target_wide_charset
21786 @defun gdb.target_wide_charset ()
21787 Return the name of the current target wide character set
21788 (@pxref{Character Sets}). This differs from
21789 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21793 @findex gdb.solib_name
21794 @defun gdb.solib_name (address)
21795 Return the name of the shared library holding the given @var{address}
21796 as a string, or @code{None}.
21799 @findex gdb.decode_line
21800 @defun gdb.decode_line @r{[}expression@r{]}
21801 Return locations of the line specified by @var{expression}, or of the
21802 current line if no argument was given. This function returns a Python
21803 tuple containing two elements. The first element contains a string
21804 holding any unparsed section of @var{expression} (or @code{None} if
21805 the expression has been fully parsed). The second element contains
21806 either @code{None} or another tuple that contains all the locations
21807 that match the expression represented as @code{gdb.Symtab_and_line}
21808 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21809 provided, it is decoded the way that @value{GDBN}'s inbuilt
21810 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21813 @defun gdb.prompt_hook (current_prompt)
21814 @anchor{prompt_hook}
21816 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21817 assigned to this operation before a prompt is displayed by
21820 The parameter @code{current_prompt} contains the current @value{GDBN}
21821 prompt. This method must return a Python string, or @code{None}. If
21822 a string is returned, the @value{GDBN} prompt will be set to that
21823 string. If @code{None} is returned, @value{GDBN} will continue to use
21824 the current prompt.
21826 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21827 such as those used by readline for command input, and annotation
21828 related prompts are prohibited from being changed.
21831 @node Exception Handling
21832 @subsubsection Exception Handling
21833 @cindex python exceptions
21834 @cindex exceptions, python
21836 When executing the @code{python} command, Python exceptions
21837 uncaught within the Python code are translated to calls to
21838 @value{GDBN} error-reporting mechanism. If the command that called
21839 @code{python} does not handle the error, @value{GDBN} will
21840 terminate it and print an error message containing the Python
21841 exception name, the associated value, and the Python call stack
21842 backtrace at the point where the exception was raised. Example:
21845 (@value{GDBP}) python print foo
21846 Traceback (most recent call last):
21847 File "<string>", line 1, in <module>
21848 NameError: name 'foo' is not defined
21851 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21852 Python code are converted to Python exceptions. The type of the
21853 Python exception depends on the error.
21857 This is the base class for most exceptions generated by @value{GDBN}.
21858 It is derived from @code{RuntimeError}, for compatibility with earlier
21859 versions of @value{GDBN}.
21861 If an error occurring in @value{GDBN} does not fit into some more
21862 specific category, then the generated exception will have this type.
21864 @item gdb.MemoryError
21865 This is a subclass of @code{gdb.error} which is thrown when an
21866 operation tried to access invalid memory in the inferior.
21868 @item KeyboardInterrupt
21869 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21870 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21873 In all cases, your exception handler will see the @value{GDBN} error
21874 message as its value and the Python call stack backtrace at the Python
21875 statement closest to where the @value{GDBN} error occured as the
21878 @findex gdb.GdbError
21879 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21880 it is useful to be able to throw an exception that doesn't cause a
21881 traceback to be printed. For example, the user may have invoked the
21882 command incorrectly. Use the @code{gdb.GdbError} exception
21883 to handle this case. Example:
21887 >class HelloWorld (gdb.Command):
21888 > """Greet the whole world."""
21889 > def __init__ (self):
21890 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21891 > def invoke (self, args, from_tty):
21892 > argv = gdb.string_to_argv (args)
21893 > if len (argv) != 0:
21894 > raise gdb.GdbError ("hello-world takes no arguments")
21895 > print "Hello, World!"
21898 (gdb) hello-world 42
21899 hello-world takes no arguments
21902 @node Values From Inferior
21903 @subsubsection Values From Inferior
21904 @cindex values from inferior, with Python
21905 @cindex python, working with values from inferior
21907 @cindex @code{gdb.Value}
21908 @value{GDBN} provides values it obtains from the inferior program in
21909 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21910 for its internal bookkeeping of the inferior's values, and for
21911 fetching values when necessary.
21913 Inferior values that are simple scalars can be used directly in
21914 Python expressions that are valid for the value's data type. Here's
21915 an example for an integer or floating-point value @code{some_val}:
21922 As result of this, @code{bar} will also be a @code{gdb.Value} object
21923 whose values are of the same type as those of @code{some_val}.
21925 Inferior values that are structures or instances of some class can
21926 be accessed using the Python @dfn{dictionary syntax}. For example, if
21927 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21928 can access its @code{foo} element with:
21931 bar = some_val['foo']
21934 Again, @code{bar} will also be a @code{gdb.Value} object.
21936 A @code{gdb.Value} that represents a function can be executed via
21937 inferior function call. Any arguments provided to the call must match
21938 the function's prototype, and must be provided in the order specified
21941 For example, @code{some_val} is a @code{gdb.Value} instance
21942 representing a function that takes two integers as arguments. To
21943 execute this function, call it like so:
21946 result = some_val (10,20)
21949 Any values returned from a function call will be stored as a
21952 The following attributes are provided:
21955 @defvar Value.address
21956 If this object is addressable, this read-only attribute holds a
21957 @code{gdb.Value} object representing the address. Otherwise,
21958 this attribute holds @code{None}.
21961 @cindex optimized out value in Python
21962 @defvar Value.is_optimized_out
21963 This read-only boolean attribute is true if the compiler optimized out
21964 this value, thus it is not available for fetching from the inferior.
21968 The type of this @code{gdb.Value}. The value of this attribute is a
21969 @code{gdb.Type} object (@pxref{Types In Python}).
21972 @defvar Value.dynamic_type
21973 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21974 type information (@acronym{RTTI}) to determine the dynamic type of the
21975 value. If this value is of class type, it will return the class in
21976 which the value is embedded, if any. If this value is of pointer or
21977 reference to a class type, it will compute the dynamic type of the
21978 referenced object, and return a pointer or reference to that type,
21979 respectively. In all other cases, it will return the value's static
21982 Note that this feature will only work when debugging a C@t{++} program
21983 that includes @acronym{RTTI} for the object in question. Otherwise,
21984 it will just return the static type of the value as in @kbd{ptype foo}
21985 (@pxref{Symbols, ptype}).
21988 @defvar Value.is_lazy
21989 The value of this read-only boolean attribute is @code{True} if this
21990 @code{gdb.Value} has not yet been fetched from the inferior.
21991 @value{GDBN} does not fetch values until necessary, for efficiency.
21995 myval = gdb.parse_and_eval ('somevar')
21998 The value of @code{somevar} is not fetched at this time. It will be
21999 fetched when the value is needed, or when the @code{fetch_lazy}
22004 The following methods are provided:
22007 @defun Value.__init__ (@var{val})
22008 Many Python values can be converted directly to a @code{gdb.Value} via
22009 this object initializer. Specifically:
22012 @item Python boolean
22013 A Python boolean is converted to the boolean type from the current
22016 @item Python integer
22017 A Python integer is converted to the C @code{long} type for the
22018 current architecture.
22021 A Python long is converted to the C @code{long long} type for the
22022 current architecture.
22025 A Python float is converted to the C @code{double} type for the
22026 current architecture.
22028 @item Python string
22029 A Python string is converted to a target string, using the current
22032 @item @code{gdb.Value}
22033 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22035 @item @code{gdb.LazyString}
22036 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22037 Python}), then the lazy string's @code{value} method is called, and
22038 its result is used.
22042 @defun Value.cast (type)
22043 Return a new instance of @code{gdb.Value} that is the result of
22044 casting this instance to the type described by @var{type}, which must
22045 be a @code{gdb.Type} object. If the cast cannot be performed for some
22046 reason, this method throws an exception.
22049 @defun Value.dereference ()
22050 For pointer data types, this method returns a new @code{gdb.Value} object
22051 whose contents is the object pointed to by the pointer. For example, if
22052 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22059 then you can use the corresponding @code{gdb.Value} to access what
22060 @code{foo} points to like this:
22063 bar = foo.dereference ()
22066 The result @code{bar} will be a @code{gdb.Value} object holding the
22067 value pointed to by @code{foo}.
22070 @defun Value.dynamic_cast (type)
22071 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22072 operator were used. Consult a C@t{++} reference for details.
22075 @defun Value.reinterpret_cast (type)
22076 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22077 operator were used. Consult a C@t{++} reference for details.
22080 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22081 If this @code{gdb.Value} represents a string, then this method
22082 converts the contents to a Python string. Otherwise, this method will
22083 throw an exception.
22085 Strings are recognized in a language-specific way; whether a given
22086 @code{gdb.Value} represents a string is determined by the current
22089 For C-like languages, a value is a string if it is a pointer to or an
22090 array of characters or ints. The string is assumed to be terminated
22091 by a zero of the appropriate width. However if the optional length
22092 argument is given, the string will be converted to that given length,
22093 ignoring any embedded zeros that the string may contain.
22095 If the optional @var{encoding} argument is given, it must be a string
22096 naming the encoding of the string in the @code{gdb.Value}, such as
22097 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22098 the same encodings as the corresponding argument to Python's
22099 @code{string.decode} method, and the Python codec machinery will be used
22100 to convert the string. If @var{encoding} is not given, or if
22101 @var{encoding} is the empty string, then either the @code{target-charset}
22102 (@pxref{Character Sets}) will be used, or a language-specific encoding
22103 will be used, if the current language is able to supply one.
22105 The optional @var{errors} argument is the same as the corresponding
22106 argument to Python's @code{string.decode} method.
22108 If the optional @var{length} argument is given, the string will be
22109 fetched and converted to the given length.
22112 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22113 If this @code{gdb.Value} represents a string, then this method
22114 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22115 In Python}). Otherwise, this method will throw an exception.
22117 If the optional @var{encoding} argument is given, it must be a string
22118 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22119 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22120 @var{encoding} argument is an encoding that @value{GDBN} does
22121 recognize, @value{GDBN} will raise an error.
22123 When a lazy string is printed, the @value{GDBN} encoding machinery is
22124 used to convert the string during printing. If the optional
22125 @var{encoding} argument is not provided, or is an empty string,
22126 @value{GDBN} will automatically select the encoding most suitable for
22127 the string type. For further information on encoding in @value{GDBN}
22128 please see @ref{Character Sets}.
22130 If the optional @var{length} argument is given, the string will be
22131 fetched and encoded to the length of characters specified. If
22132 the @var{length} argument is not provided, the string will be fetched
22133 and encoded until a null of appropriate width is found.
22136 @defun Value.fetch_lazy ()
22137 If the @code{gdb.Value} object is currently a lazy value
22138 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22139 fetched from the inferior. Any errors that occur in the process
22140 will produce a Python exception.
22142 If the @code{gdb.Value} object is not a lazy value, this method
22145 This method does not return a value.
22150 @node Types In Python
22151 @subsubsection Types In Python
22152 @cindex types in Python
22153 @cindex Python, working with types
22156 @value{GDBN} represents types from the inferior using the class
22159 The following type-related functions are available in the @code{gdb}
22162 @findex gdb.lookup_type
22163 @defun gdb.lookup_type (name @r{[}, block@r{]})
22164 This function looks up a type by name. @var{name} is the name of the
22165 type to look up. It must be a string.
22167 If @var{block} is given, then @var{name} is looked up in that scope.
22168 Otherwise, it is searched for globally.
22170 Ordinarily, this function will return an instance of @code{gdb.Type}.
22171 If the named type cannot be found, it will throw an exception.
22174 If the type is a structure or class type, or an enum type, the fields
22175 of that type can be accessed using the Python @dfn{dictionary syntax}.
22176 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22177 a structure type, you can access its @code{foo} field with:
22180 bar = some_type['foo']
22183 @code{bar} will be a @code{gdb.Field} object; see below under the
22184 description of the @code{Type.fields} method for a description of the
22185 @code{gdb.Field} class.
22187 An instance of @code{Type} has the following attributes:
22191 The type code for this type. The type code will be one of the
22192 @code{TYPE_CODE_} constants defined below.
22195 @defvar Type.sizeof
22196 The size of this type, in target @code{char} units. Usually, a
22197 target's @code{char} type will be an 8-bit byte. However, on some
22198 unusual platforms, this type may have a different size.
22202 The tag name for this type. The tag name is the name after
22203 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22204 languages have this concept. If this type has no tag name, then
22205 @code{None} is returned.
22209 The following methods are provided:
22212 @defun Type.fields ()
22213 For structure and union types, this method returns the fields. Range
22214 types have two fields, the minimum and maximum values. Enum types
22215 have one field per enum constant. Function and method types have one
22216 field per parameter. The base types of C@t{++} classes are also
22217 represented as fields. If the type has no fields, or does not fit
22218 into one of these categories, an empty sequence will be returned.
22220 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22223 This attribute is not available for @code{static} fields (as in
22224 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22225 position of the field. For @code{enum} fields, the value is the
22226 enumeration member's integer representation.
22229 The name of the field, or @code{None} for anonymous fields.
22232 This is @code{True} if the field is artificial, usually meaning that
22233 it was provided by the compiler and not the user. This attribute is
22234 always provided, and is @code{False} if the field is not artificial.
22236 @item is_base_class
22237 This is @code{True} if the field represents a base class of a C@t{++}
22238 structure. This attribute is always provided, and is @code{False}
22239 if the field is not a base class of the type that is the argument of
22240 @code{fields}, or if that type was not a C@t{++} class.
22243 If the field is packed, or is a bitfield, then this will have a
22244 non-zero value, which is the size of the field in bits. Otherwise,
22245 this will be zero; in this case the field's size is given by its type.
22248 The type of the field. This is usually an instance of @code{Type},
22249 but it can be @code{None} in some situations.
22253 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22254 Return a new @code{gdb.Type} object which represents an array of this
22255 type. If one argument is given, it is the inclusive upper bound of
22256 the array; in this case the lower bound is zero. If two arguments are
22257 given, the first argument is the lower bound of the array, and the
22258 second argument is the upper bound of the array. An array's length
22259 must not be negative, but the bounds can be.
22262 @defun Type.const ()
22263 Return a new @code{gdb.Type} object which represents a
22264 @code{const}-qualified variant of this type.
22267 @defun Type.volatile ()
22268 Return a new @code{gdb.Type} object which represents a
22269 @code{volatile}-qualified variant of this type.
22272 @defun Type.unqualified ()
22273 Return a new @code{gdb.Type} object which represents an unqualified
22274 variant of this type. That is, the result is neither @code{const} nor
22278 @defun Type.range ()
22279 Return a Python @code{Tuple} object that contains two elements: the
22280 low bound of the argument type and the high bound of that type. If
22281 the type does not have a range, @value{GDBN} will raise a
22282 @code{gdb.error} exception (@pxref{Exception Handling}).
22285 @defun Type.reference ()
22286 Return a new @code{gdb.Type} object which represents a reference to this
22290 @defun Type.pointer ()
22291 Return a new @code{gdb.Type} object which represents a pointer to this
22295 @defun Type.strip_typedefs ()
22296 Return a new @code{gdb.Type} that represents the real type,
22297 after removing all layers of typedefs.
22300 @defun Type.target ()
22301 Return a new @code{gdb.Type} object which represents the target type
22304 For a pointer type, the target type is the type of the pointed-to
22305 object. For an array type (meaning C-like arrays), the target type is
22306 the type of the elements of the array. For a function or method type,
22307 the target type is the type of the return value. For a complex type,
22308 the target type is the type of the elements. For a typedef, the
22309 target type is the aliased type.
22311 If the type does not have a target, this method will throw an
22315 @defun Type.template_argument (n @r{[}, block@r{]})
22316 If this @code{gdb.Type} is an instantiation of a template, this will
22317 return a new @code{gdb.Type} which represents the type of the
22318 @var{n}th template argument.
22320 If this @code{gdb.Type} is not a template type, this will throw an
22321 exception. Ordinarily, only C@t{++} code will have template types.
22323 If @var{block} is given, then @var{name} is looked up in that scope.
22324 Otherwise, it is searched for globally.
22329 Each type has a code, which indicates what category this type falls
22330 into. The available type categories are represented by constants
22331 defined in the @code{gdb} module:
22334 @findex TYPE_CODE_PTR
22335 @findex gdb.TYPE_CODE_PTR
22336 @item gdb.TYPE_CODE_PTR
22337 The type is a pointer.
22339 @findex TYPE_CODE_ARRAY
22340 @findex gdb.TYPE_CODE_ARRAY
22341 @item gdb.TYPE_CODE_ARRAY
22342 The type is an array.
22344 @findex TYPE_CODE_STRUCT
22345 @findex gdb.TYPE_CODE_STRUCT
22346 @item gdb.TYPE_CODE_STRUCT
22347 The type is a structure.
22349 @findex TYPE_CODE_UNION
22350 @findex gdb.TYPE_CODE_UNION
22351 @item gdb.TYPE_CODE_UNION
22352 The type is a union.
22354 @findex TYPE_CODE_ENUM
22355 @findex gdb.TYPE_CODE_ENUM
22356 @item gdb.TYPE_CODE_ENUM
22357 The type is an enum.
22359 @findex TYPE_CODE_FLAGS
22360 @findex gdb.TYPE_CODE_FLAGS
22361 @item gdb.TYPE_CODE_FLAGS
22362 A bit flags type, used for things such as status registers.
22364 @findex TYPE_CODE_FUNC
22365 @findex gdb.TYPE_CODE_FUNC
22366 @item gdb.TYPE_CODE_FUNC
22367 The type is a function.
22369 @findex TYPE_CODE_INT
22370 @findex gdb.TYPE_CODE_INT
22371 @item gdb.TYPE_CODE_INT
22372 The type is an integer type.
22374 @findex TYPE_CODE_FLT
22375 @findex gdb.TYPE_CODE_FLT
22376 @item gdb.TYPE_CODE_FLT
22377 A floating point type.
22379 @findex TYPE_CODE_VOID
22380 @findex gdb.TYPE_CODE_VOID
22381 @item gdb.TYPE_CODE_VOID
22382 The special type @code{void}.
22384 @findex TYPE_CODE_SET
22385 @findex gdb.TYPE_CODE_SET
22386 @item gdb.TYPE_CODE_SET
22389 @findex TYPE_CODE_RANGE
22390 @findex gdb.TYPE_CODE_RANGE
22391 @item gdb.TYPE_CODE_RANGE
22392 A range type, that is, an integer type with bounds.
22394 @findex TYPE_CODE_STRING
22395 @findex gdb.TYPE_CODE_STRING
22396 @item gdb.TYPE_CODE_STRING
22397 A string type. Note that this is only used for certain languages with
22398 language-defined string types; C strings are not represented this way.
22400 @findex TYPE_CODE_BITSTRING
22401 @findex gdb.TYPE_CODE_BITSTRING
22402 @item gdb.TYPE_CODE_BITSTRING
22405 @findex TYPE_CODE_ERROR
22406 @findex gdb.TYPE_CODE_ERROR
22407 @item gdb.TYPE_CODE_ERROR
22408 An unknown or erroneous type.
22410 @findex TYPE_CODE_METHOD
22411 @findex gdb.TYPE_CODE_METHOD
22412 @item gdb.TYPE_CODE_METHOD
22413 A method type, as found in C@t{++} or Java.
22415 @findex TYPE_CODE_METHODPTR
22416 @findex gdb.TYPE_CODE_METHODPTR
22417 @item gdb.TYPE_CODE_METHODPTR
22418 A pointer-to-member-function.
22420 @findex TYPE_CODE_MEMBERPTR
22421 @findex gdb.TYPE_CODE_MEMBERPTR
22422 @item gdb.TYPE_CODE_MEMBERPTR
22423 A pointer-to-member.
22425 @findex TYPE_CODE_REF
22426 @findex gdb.TYPE_CODE_REF
22427 @item gdb.TYPE_CODE_REF
22430 @findex TYPE_CODE_CHAR
22431 @findex gdb.TYPE_CODE_CHAR
22432 @item gdb.TYPE_CODE_CHAR
22435 @findex TYPE_CODE_BOOL
22436 @findex gdb.TYPE_CODE_BOOL
22437 @item gdb.TYPE_CODE_BOOL
22440 @findex TYPE_CODE_COMPLEX
22441 @findex gdb.TYPE_CODE_COMPLEX
22442 @item gdb.TYPE_CODE_COMPLEX
22443 A complex float type.
22445 @findex TYPE_CODE_TYPEDEF
22446 @findex gdb.TYPE_CODE_TYPEDEF
22447 @item gdb.TYPE_CODE_TYPEDEF
22448 A typedef to some other type.
22450 @findex TYPE_CODE_NAMESPACE
22451 @findex gdb.TYPE_CODE_NAMESPACE
22452 @item gdb.TYPE_CODE_NAMESPACE
22453 A C@t{++} namespace.
22455 @findex TYPE_CODE_DECFLOAT
22456 @findex gdb.TYPE_CODE_DECFLOAT
22457 @item gdb.TYPE_CODE_DECFLOAT
22458 A decimal floating point type.
22460 @findex TYPE_CODE_INTERNAL_FUNCTION
22461 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22462 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22463 A function internal to @value{GDBN}. This is the type used to represent
22464 convenience functions.
22467 Further support for types is provided in the @code{gdb.types}
22468 Python module (@pxref{gdb.types}).
22470 @node Pretty Printing API
22471 @subsubsection Pretty Printing API
22473 An example output is provided (@pxref{Pretty Printing}).
22475 A pretty-printer is just an object that holds a value and implements a
22476 specific interface, defined here.
22478 @defun pretty_printer.children (self)
22479 @value{GDBN} will call this method on a pretty-printer to compute the
22480 children of the pretty-printer's value.
22482 This method must return an object conforming to the Python iterator
22483 protocol. Each item returned by the iterator must be a tuple holding
22484 two elements. The first element is the ``name'' of the child; the
22485 second element is the child's value. The value can be any Python
22486 object which is convertible to a @value{GDBN} value.
22488 This method is optional. If it does not exist, @value{GDBN} will act
22489 as though the value has no children.
22492 @defun pretty_printer.display_hint (self)
22493 The CLI may call this method and use its result to change the
22494 formatting of a value. The result will also be supplied to an MI
22495 consumer as a @samp{displayhint} attribute of the variable being
22498 This method is optional. If it does exist, this method must return a
22501 Some display hints are predefined by @value{GDBN}:
22505 Indicate that the object being printed is ``array-like''. The CLI
22506 uses this to respect parameters such as @code{set print elements} and
22507 @code{set print array}.
22510 Indicate that the object being printed is ``map-like'', and that the
22511 children of this value can be assumed to alternate between keys and
22515 Indicate that the object being printed is ``string-like''. If the
22516 printer's @code{to_string} method returns a Python string of some
22517 kind, then @value{GDBN} will call its internal language-specific
22518 string-printing function to format the string. For the CLI this means
22519 adding quotation marks, possibly escaping some characters, respecting
22520 @code{set print elements}, and the like.
22524 @defun pretty_printer.to_string (self)
22525 @value{GDBN} will call this method to display the string
22526 representation of the value passed to the object's constructor.
22528 When printing from the CLI, if the @code{to_string} method exists,
22529 then @value{GDBN} will prepend its result to the values returned by
22530 @code{children}. Exactly how this formatting is done is dependent on
22531 the display hint, and may change as more hints are added. Also,
22532 depending on the print settings (@pxref{Print Settings}), the CLI may
22533 print just the result of @code{to_string} in a stack trace, omitting
22534 the result of @code{children}.
22536 If this method returns a string, it is printed verbatim.
22538 Otherwise, if this method returns an instance of @code{gdb.Value},
22539 then @value{GDBN} prints this value. This may result in a call to
22540 another pretty-printer.
22542 If instead the method returns a Python value which is convertible to a
22543 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22544 the resulting value. Again, this may result in a call to another
22545 pretty-printer. Python scalars (integers, floats, and booleans) and
22546 strings are convertible to @code{gdb.Value}; other types are not.
22548 Finally, if this method returns @code{None} then no further operations
22549 are peformed in this method and nothing is printed.
22551 If the result is not one of these types, an exception is raised.
22554 @value{GDBN} provides a function which can be used to look up the
22555 default pretty-printer for a @code{gdb.Value}:
22557 @findex gdb.default_visualizer
22558 @defun gdb.default_visualizer (value)
22559 This function takes a @code{gdb.Value} object as an argument. If a
22560 pretty-printer for this value exists, then it is returned. If no such
22561 printer exists, then this returns @code{None}.
22564 @node Selecting Pretty-Printers
22565 @subsubsection Selecting Pretty-Printers
22567 The Python list @code{gdb.pretty_printers} contains an array of
22568 functions or callable objects that have been registered via addition
22569 as a pretty-printer. Printers in this list are called @code{global}
22570 printers, they're available when debugging all inferiors.
22571 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22572 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22575 Each function on these lists is passed a single @code{gdb.Value}
22576 argument and should return a pretty-printer object conforming to the
22577 interface definition above (@pxref{Pretty Printing API}). If a function
22578 cannot create a pretty-printer for the value, it should return
22581 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22582 @code{gdb.Objfile} in the current program space and iteratively calls
22583 each enabled lookup routine in the list for that @code{gdb.Objfile}
22584 until it receives a pretty-printer object.
22585 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22586 searches the pretty-printer list of the current program space,
22587 calling each enabled function until an object is returned.
22588 After these lists have been exhausted, it tries the global
22589 @code{gdb.pretty_printers} list, again calling each enabled function until an
22590 object is returned.
22592 The order in which the objfiles are searched is not specified. For a
22593 given list, functions are always invoked from the head of the list,
22594 and iterated over sequentially until the end of the list, or a printer
22595 object is returned.
22597 For various reasons a pretty-printer may not work.
22598 For example, the underlying data structure may have changed and
22599 the pretty-printer is out of date.
22601 The consequences of a broken pretty-printer are severe enough that
22602 @value{GDBN} provides support for enabling and disabling individual
22603 printers. For example, if @code{print frame-arguments} is on,
22604 a backtrace can become highly illegible if any argument is printed
22605 with a broken printer.
22607 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22608 attribute to the registered function or callable object. If this attribute
22609 is present and its value is @code{False}, the printer is disabled, otherwise
22610 the printer is enabled.
22612 @node Writing a Pretty-Printer
22613 @subsubsection Writing a Pretty-Printer
22614 @cindex writing a pretty-printer
22616 A pretty-printer consists of two parts: a lookup function to detect
22617 if the type is supported, and the printer itself.
22619 Here is an example showing how a @code{std::string} printer might be
22620 written. @xref{Pretty Printing API}, for details on the API this class
22624 class StdStringPrinter(object):
22625 "Print a std::string"
22627 def __init__(self, val):
22630 def to_string(self):
22631 return self.val['_M_dataplus']['_M_p']
22633 def display_hint(self):
22637 And here is an example showing how a lookup function for the printer
22638 example above might be written.
22641 def str_lookup_function(val):
22642 lookup_tag = val.type.tag
22643 if lookup_tag == None:
22645 regex = re.compile("^std::basic_string<char,.*>$")
22646 if regex.match(lookup_tag):
22647 return StdStringPrinter(val)
22651 The example lookup function extracts the value's type, and attempts to
22652 match it to a type that it can pretty-print. If it is a type the
22653 printer can pretty-print, it will return a printer object. If not, it
22654 returns @code{None}.
22656 We recommend that you put your core pretty-printers into a Python
22657 package. If your pretty-printers are for use with a library, we
22658 further recommend embedding a version number into the package name.
22659 This practice will enable @value{GDBN} to load multiple versions of
22660 your pretty-printers at the same time, because they will have
22663 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22664 can be evaluated multiple times without changing its meaning. An
22665 ideal auto-load file will consist solely of @code{import}s of your
22666 printer modules, followed by a call to a register pretty-printers with
22667 the current objfile.
22669 Taken as a whole, this approach will scale nicely to multiple
22670 inferiors, each potentially using a different library version.
22671 Embedding a version number in the Python package name will ensure that
22672 @value{GDBN} is able to load both sets of printers simultaneously.
22673 Then, because the search for pretty-printers is done by objfile, and
22674 because your auto-loaded code took care to register your library's
22675 printers with a specific objfile, @value{GDBN} will find the correct
22676 printers for the specific version of the library used by each
22679 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22680 this code might appear in @code{gdb.libstdcxx.v6}:
22683 def register_printers(objfile):
22684 objfile.pretty_printers.append(str_lookup_function)
22688 And then the corresponding contents of the auto-load file would be:
22691 import gdb.libstdcxx.v6
22692 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22695 The previous example illustrates a basic pretty-printer.
22696 There are a few things that can be improved on.
22697 The printer doesn't have a name, making it hard to identify in a
22698 list of installed printers. The lookup function has a name, but
22699 lookup functions can have arbitrary, even identical, names.
22701 Second, the printer only handles one type, whereas a library typically has
22702 several types. One could install a lookup function for each desired type
22703 in the library, but one could also have a single lookup function recognize
22704 several types. The latter is the conventional way this is handled.
22705 If a pretty-printer can handle multiple data types, then its
22706 @dfn{subprinters} are the printers for the individual data types.
22708 The @code{gdb.printing} module provides a formal way of solving these
22709 problems (@pxref{gdb.printing}).
22710 Here is another example that handles multiple types.
22712 These are the types we are going to pretty-print:
22715 struct foo @{ int a, b; @};
22716 struct bar @{ struct foo x, y; @};
22719 Here are the printers:
22723 """Print a foo object."""
22725 def __init__(self, val):
22728 def to_string(self):
22729 return ("a=<" + str(self.val["a"]) +
22730 "> b=<" + str(self.val["b"]) + ">")
22733 """Print a bar object."""
22735 def __init__(self, val):
22738 def to_string(self):
22739 return ("x=<" + str(self.val["x"]) +
22740 "> y=<" + str(self.val["y"]) + ">")
22743 This example doesn't need a lookup function, that is handled by the
22744 @code{gdb.printing} module. Instead a function is provided to build up
22745 the object that handles the lookup.
22748 import gdb.printing
22750 def build_pretty_printer():
22751 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22753 pp.add_printer('foo', '^foo$', fooPrinter)
22754 pp.add_printer('bar', '^bar$', barPrinter)
22758 And here is the autoload support:
22761 import gdb.printing
22763 gdb.printing.register_pretty_printer(
22764 gdb.current_objfile(),
22765 my_library.build_pretty_printer())
22768 Finally, when this printer is loaded into @value{GDBN}, here is the
22769 corresponding output of @samp{info pretty-printer}:
22772 (gdb) info pretty-printer
22779 @node Inferiors In Python
22780 @subsubsection Inferiors In Python
22781 @cindex inferiors in Python
22783 @findex gdb.Inferior
22784 Programs which are being run under @value{GDBN} are called inferiors
22785 (@pxref{Inferiors and Programs}). Python scripts can access
22786 information about and manipulate inferiors controlled by @value{GDBN}
22787 via objects of the @code{gdb.Inferior} class.
22789 The following inferior-related functions are available in the @code{gdb}
22792 @defun gdb.inferiors ()
22793 Return a tuple containing all inferior objects.
22796 @defun gdb.selected_inferior ()
22797 Return an object representing the current inferior.
22800 A @code{gdb.Inferior} object has the following attributes:
22803 @defvar Inferior.num
22804 ID of inferior, as assigned by GDB.
22807 @defvar Inferior.pid
22808 Process ID of the inferior, as assigned by the underlying operating
22812 @defvar Inferior.was_attached
22813 Boolean signaling whether the inferior was created using `attach', or
22814 started by @value{GDBN} itself.
22818 A @code{gdb.Inferior} object has the following methods:
22821 @defun Inferior.is_valid ()
22822 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22823 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22824 if the inferior no longer exists within @value{GDBN}. All other
22825 @code{gdb.Inferior} methods will throw an exception if it is invalid
22826 at the time the method is called.
22829 @defun Inferior.threads ()
22830 This method returns a tuple holding all the threads which are valid
22831 when it is called. If there are no valid threads, the method will
22832 return an empty tuple.
22835 @findex gdb.read_memory
22836 @defun Inferior.read_memory (address, length)
22837 Read @var{length} bytes of memory from the inferior, starting at
22838 @var{address}. Returns a buffer object, which behaves much like an array
22839 or a string. It can be modified and given to the @code{gdb.write_memory}
22843 @findex gdb.write_memory
22844 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22845 Write the contents of @var{buffer} to the inferior, starting at
22846 @var{address}. The @var{buffer} parameter must be a Python object
22847 which supports the buffer protocol, i.e., a string, an array or the
22848 object returned from @code{gdb.read_memory}. If given, @var{length}
22849 determines the number of bytes from @var{buffer} to be written.
22852 @findex gdb.search_memory
22853 @defun Inferior.search_memory (address, length, pattern)
22854 Search a region of the inferior memory starting at @var{address} with
22855 the given @var{length} using the search pattern supplied in
22856 @var{pattern}. The @var{pattern} parameter must be a Python object
22857 which supports the buffer protocol, i.e., a string, an array or the
22858 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22859 containing the address where the pattern was found, or @code{None} if
22860 the pattern could not be found.
22864 @node Events In Python
22865 @subsubsection Events In Python
22866 @cindex inferior events in Python
22868 @value{GDBN} provides a general event facility so that Python code can be
22869 notified of various state changes, particularly changes that occur in
22872 An @dfn{event} is just an object that describes some state change. The
22873 type of the object and its attributes will vary depending on the details
22874 of the change. All the existing events are described below.
22876 In order to be notified of an event, you must register an event handler
22877 with an @dfn{event registry}. An event registry is an object in the
22878 @code{gdb.events} module which dispatches particular events. A registry
22879 provides methods to register and unregister event handlers:
22882 @defun EventRegistry.connect (object)
22883 Add the given callable @var{object} to the registry. This object will be
22884 called when an event corresponding to this registry occurs.
22887 @defun EventRegistry.disconnect (object)
22888 Remove the given @var{object} from the registry. Once removed, the object
22889 will no longer receive notifications of events.
22893 Here is an example:
22896 def exit_handler (event):
22897 print "event type: exit"
22898 print "exit code: %d" % (event.exit_code)
22900 gdb.events.exited.connect (exit_handler)
22903 In the above example we connect our handler @code{exit_handler} to the
22904 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22905 called when the inferior exits. The argument @dfn{event} in this example is
22906 of type @code{gdb.ExitedEvent}. As you can see in the example the
22907 @code{ExitedEvent} object has an attribute which indicates the exit code of
22910 The following is a listing of the event registries that are available and
22911 details of the events they emit:
22916 Emits @code{gdb.ThreadEvent}.
22918 Some events can be thread specific when @value{GDBN} is running in non-stop
22919 mode. When represented in Python, these events all extend
22920 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22921 events which are emitted by this or other modules might extend this event.
22922 Examples of these events are @code{gdb.BreakpointEvent} and
22923 @code{gdb.ContinueEvent}.
22926 @defvar ThreadEvent.inferior_thread
22927 In non-stop mode this attribute will be set to the specific thread which was
22928 involved in the emitted event. Otherwise, it will be set to @code{None}.
22932 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22934 This event indicates that the inferior has been continued after a stop. For
22935 inherited attribute refer to @code{gdb.ThreadEvent} above.
22937 @item events.exited
22938 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22939 @code{events.ExitedEvent} has two attributes:
22941 @defvar ExitedEvent.exit_code
22942 An integer representing the exit code, if available, which the inferior
22943 has returned. (The exit code could be unavailable if, for example,
22944 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22945 the attribute does not exist.
22947 @defvar ExitedEvent inferior
22948 A reference to the inferior which triggered the @code{exited} event.
22953 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22955 Indicates that the inferior has stopped. All events emitted by this registry
22956 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22957 will indicate the stopped thread when @value{GDBN} is running in non-stop
22958 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22960 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22962 This event indicates that the inferior or one of its threads has received as
22963 signal. @code{gdb.SignalEvent} has the following attributes:
22966 @defvar SignalEvent.stop_signal
22967 A string representing the signal received by the inferior. A list of possible
22968 signal values can be obtained by running the command @code{info signals} in
22969 the @value{GDBN} command prompt.
22973 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22975 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22976 been hit, and has the following attributes:
22979 @defvar BreakpointEvent.breakpoints
22980 A sequence containing references to all the breakpoints (type
22981 @code{gdb.Breakpoint}) that were hit.
22982 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22984 @defvar BreakpointEvent.breakpoint
22985 A reference to the first breakpoint that was hit.
22986 This function is maintained for backward compatibility and is now deprecated
22987 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22991 @item events.new_objfile
22992 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22993 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22996 @defvar NewObjFileEvent.new_objfile
22997 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22998 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23004 @node Threads In Python
23005 @subsubsection Threads In Python
23006 @cindex threads in python
23008 @findex gdb.InferiorThread
23009 Python scripts can access information about, and manipulate inferior threads
23010 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23012 The following thread-related functions are available in the @code{gdb}
23015 @findex gdb.selected_thread
23016 @defun gdb.selected_thread ()
23017 This function returns the thread object for the selected thread. If there
23018 is no selected thread, this will return @code{None}.
23021 A @code{gdb.InferiorThread} object has the following attributes:
23024 @defvar InferiorThread.name
23025 The name of the thread. If the user specified a name using
23026 @code{thread name}, then this returns that name. Otherwise, if an
23027 OS-supplied name is available, then it is returned. Otherwise, this
23028 returns @code{None}.
23030 This attribute can be assigned to. The new value must be a string
23031 object, which sets the new name, or @code{None}, which removes any
23032 user-specified thread name.
23035 @defvar InferiorThread.num
23036 ID of the thread, as assigned by GDB.
23039 @defvar InferiorThread.ptid
23040 ID of the thread, as assigned by the operating system. This attribute is a
23041 tuple containing three integers. The first is the Process ID (PID); the second
23042 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23043 Either the LWPID or TID may be 0, which indicates that the operating system
23044 does not use that identifier.
23048 A @code{gdb.InferiorThread} object has the following methods:
23051 @defun InferiorThread.is_valid ()
23052 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23053 @code{False} if not. A @code{gdb.InferiorThread} object will become
23054 invalid if the thread exits, or the inferior that the thread belongs
23055 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23056 exception if it is invalid at the time the method is called.
23059 @defun InferiorThread.switch ()
23060 This changes @value{GDBN}'s currently selected thread to the one represented
23064 @defun InferiorThread.is_stopped ()
23065 Return a Boolean indicating whether the thread is stopped.
23068 @defun InferiorThread.is_running ()
23069 Return a Boolean indicating whether the thread is running.
23072 @defun InferiorThread.is_exited ()
23073 Return a Boolean indicating whether the thread is exited.
23077 @node Commands In Python
23078 @subsubsection Commands In Python
23080 @cindex commands in python
23081 @cindex python commands
23082 You can implement new @value{GDBN} CLI commands in Python. A CLI
23083 command is implemented using an instance of the @code{gdb.Command}
23084 class, most commonly using a subclass.
23086 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23087 The object initializer for @code{Command} registers the new command
23088 with @value{GDBN}. This initializer is normally invoked from the
23089 subclass' own @code{__init__} method.
23091 @var{name} is the name of the command. If @var{name} consists of
23092 multiple words, then the initial words are looked for as prefix
23093 commands. In this case, if one of the prefix commands does not exist,
23094 an exception is raised.
23096 There is no support for multi-line commands.
23098 @var{command_class} should be one of the @samp{COMMAND_} constants
23099 defined below. This argument tells @value{GDBN} how to categorize the
23100 new command in the help system.
23102 @var{completer_class} is an optional argument. If given, it should be
23103 one of the @samp{COMPLETE_} constants defined below. This argument
23104 tells @value{GDBN} how to perform completion for this command. If not
23105 given, @value{GDBN} will attempt to complete using the object's
23106 @code{complete} method (see below); if no such method is found, an
23107 error will occur when completion is attempted.
23109 @var{prefix} is an optional argument. If @code{True}, then the new
23110 command is a prefix command; sub-commands of this command may be
23113 The help text for the new command is taken from the Python
23114 documentation string for the command's class, if there is one. If no
23115 documentation string is provided, the default value ``This command is
23116 not documented.'' is used.
23119 @cindex don't repeat Python command
23120 @defun Command.dont_repeat ()
23121 By default, a @value{GDBN} command is repeated when the user enters a
23122 blank line at the command prompt. A command can suppress this
23123 behavior by invoking the @code{dont_repeat} method. This is similar
23124 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23127 @defun Command.invoke (argument, from_tty)
23128 This method is called by @value{GDBN} when this command is invoked.
23130 @var{argument} is a string. It is the argument to the command, after
23131 leading and trailing whitespace has been stripped.
23133 @var{from_tty} is a boolean argument. When true, this means that the
23134 command was entered by the user at the terminal; when false it means
23135 that the command came from elsewhere.
23137 If this method throws an exception, it is turned into a @value{GDBN}
23138 @code{error} call. Otherwise, the return value is ignored.
23140 @findex gdb.string_to_argv
23141 To break @var{argument} up into an argv-like string use
23142 @code{gdb.string_to_argv}. This function behaves identically to
23143 @value{GDBN}'s internal argument lexer @code{buildargv}.
23144 It is recommended to use this for consistency.
23145 Arguments are separated by spaces and may be quoted.
23149 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23150 ['1', '2 "3', '4 "5', "6 '7"]
23155 @cindex completion of Python commands
23156 @defun Command.complete (text, word)
23157 This method is called by @value{GDBN} when the user attempts
23158 completion on this command. All forms of completion are handled by
23159 this method, that is, the @key{TAB} and @key{M-?} key bindings
23160 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23163 The arguments @var{text} and @var{word} are both strings. @var{text}
23164 holds the complete command line up to the cursor's location.
23165 @var{word} holds the last word of the command line; this is computed
23166 using a word-breaking heuristic.
23168 The @code{complete} method can return several values:
23171 If the return value is a sequence, the contents of the sequence are
23172 used as the completions. It is up to @code{complete} to ensure that the
23173 contents actually do complete the word. A zero-length sequence is
23174 allowed, it means that there were no completions available. Only
23175 string elements of the sequence are used; other elements in the
23176 sequence are ignored.
23179 If the return value is one of the @samp{COMPLETE_} constants defined
23180 below, then the corresponding @value{GDBN}-internal completion
23181 function is invoked, and its result is used.
23184 All other results are treated as though there were no available
23189 When a new command is registered, it must be declared as a member of
23190 some general class of commands. This is used to classify top-level
23191 commands in the on-line help system; note that prefix commands are not
23192 listed under their own category but rather that of their top-level
23193 command. The available classifications are represented by constants
23194 defined in the @code{gdb} module:
23197 @findex COMMAND_NONE
23198 @findex gdb.COMMAND_NONE
23199 @item gdb.COMMAND_NONE
23200 The command does not belong to any particular class. A command in
23201 this category will not be displayed in any of the help categories.
23203 @findex COMMAND_RUNNING
23204 @findex gdb.COMMAND_RUNNING
23205 @item gdb.COMMAND_RUNNING
23206 The command is related to running the inferior. For example,
23207 @code{start}, @code{step}, and @code{continue} are in this category.
23208 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23209 commands in this category.
23211 @findex COMMAND_DATA
23212 @findex gdb.COMMAND_DATA
23213 @item gdb.COMMAND_DATA
23214 The command is related to data or variables. For example,
23215 @code{call}, @code{find}, and @code{print} are in this category. Type
23216 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23219 @findex COMMAND_STACK
23220 @findex gdb.COMMAND_STACK
23221 @item gdb.COMMAND_STACK
23222 The command has to do with manipulation of the stack. For example,
23223 @code{backtrace}, @code{frame}, and @code{return} are in this
23224 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23225 list of commands in this category.
23227 @findex COMMAND_FILES
23228 @findex gdb.COMMAND_FILES
23229 @item gdb.COMMAND_FILES
23230 This class is used for file-related commands. For example,
23231 @code{file}, @code{list} and @code{section} are in this category.
23232 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23233 commands in this category.
23235 @findex COMMAND_SUPPORT
23236 @findex gdb.COMMAND_SUPPORT
23237 @item gdb.COMMAND_SUPPORT
23238 This should be used for ``support facilities'', generally meaning
23239 things that are useful to the user when interacting with @value{GDBN},
23240 but not related to the state of the inferior. For example,
23241 @code{help}, @code{make}, and @code{shell} are in this category. Type
23242 @kbd{help support} at the @value{GDBN} prompt to see a list of
23243 commands in this category.
23245 @findex COMMAND_STATUS
23246 @findex gdb.COMMAND_STATUS
23247 @item gdb.COMMAND_STATUS
23248 The command is an @samp{info}-related command, that is, related to the
23249 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23250 and @code{show} are in this category. Type @kbd{help status} at the
23251 @value{GDBN} prompt to see a list of commands in this category.
23253 @findex COMMAND_BREAKPOINTS
23254 @findex gdb.COMMAND_BREAKPOINTS
23255 @item gdb.COMMAND_BREAKPOINTS
23256 The command has to do with breakpoints. For example, @code{break},
23257 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23258 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23261 @findex COMMAND_TRACEPOINTS
23262 @findex gdb.COMMAND_TRACEPOINTS
23263 @item gdb.COMMAND_TRACEPOINTS
23264 The command has to do with tracepoints. For example, @code{trace},
23265 @code{actions}, and @code{tfind} are in this category. Type
23266 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23267 commands in this category.
23269 @findex COMMAND_OBSCURE
23270 @findex gdb.COMMAND_OBSCURE
23271 @item gdb.COMMAND_OBSCURE
23272 The command is only used in unusual circumstances, or is not of
23273 general interest to users. For example, @code{checkpoint},
23274 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23275 obscure} at the @value{GDBN} prompt to see a list of commands in this
23278 @findex COMMAND_MAINTENANCE
23279 @findex gdb.COMMAND_MAINTENANCE
23280 @item gdb.COMMAND_MAINTENANCE
23281 The command is only useful to @value{GDBN} maintainers. The
23282 @code{maintenance} and @code{flushregs} commands are in this category.
23283 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23284 commands in this category.
23287 A new command can use a predefined completion function, either by
23288 specifying it via an argument at initialization, or by returning it
23289 from the @code{complete} method. These predefined completion
23290 constants are all defined in the @code{gdb} module:
23293 @findex COMPLETE_NONE
23294 @findex gdb.COMPLETE_NONE
23295 @item gdb.COMPLETE_NONE
23296 This constant means that no completion should be done.
23298 @findex COMPLETE_FILENAME
23299 @findex gdb.COMPLETE_FILENAME
23300 @item gdb.COMPLETE_FILENAME
23301 This constant means that filename completion should be performed.
23303 @findex COMPLETE_LOCATION
23304 @findex gdb.COMPLETE_LOCATION
23305 @item gdb.COMPLETE_LOCATION
23306 This constant means that location completion should be done.
23307 @xref{Specify Location}.
23309 @findex COMPLETE_COMMAND
23310 @findex gdb.COMPLETE_COMMAND
23311 @item gdb.COMPLETE_COMMAND
23312 This constant means that completion should examine @value{GDBN}
23315 @findex COMPLETE_SYMBOL
23316 @findex gdb.COMPLETE_SYMBOL
23317 @item gdb.COMPLETE_SYMBOL
23318 This constant means that completion should be done using symbol names
23322 The following code snippet shows how a trivial CLI command can be
23323 implemented in Python:
23326 class HelloWorld (gdb.Command):
23327 """Greet the whole world."""
23329 def __init__ (self):
23330 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23332 def invoke (self, arg, from_tty):
23333 print "Hello, World!"
23338 The last line instantiates the class, and is necessary to trigger the
23339 registration of the command with @value{GDBN}. Depending on how the
23340 Python code is read into @value{GDBN}, you may need to import the
23341 @code{gdb} module explicitly.
23343 @node Parameters In Python
23344 @subsubsection Parameters In Python
23346 @cindex parameters in python
23347 @cindex python parameters
23348 @tindex gdb.Parameter
23350 You can implement new @value{GDBN} parameters using Python. A new
23351 parameter is implemented as an instance of the @code{gdb.Parameter}
23354 Parameters are exposed to the user via the @code{set} and
23355 @code{show} commands. @xref{Help}.
23357 There are many parameters that already exist and can be set in
23358 @value{GDBN}. Two examples are: @code{set follow fork} and
23359 @code{set charset}. Setting these parameters influences certain
23360 behavior in @value{GDBN}. Similarly, you can define parameters that
23361 can be used to influence behavior in custom Python scripts and commands.
23363 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23364 The object initializer for @code{Parameter} registers the new
23365 parameter with @value{GDBN}. This initializer is normally invoked
23366 from the subclass' own @code{__init__} method.
23368 @var{name} is the name of the new parameter. If @var{name} consists
23369 of multiple words, then the initial words are looked for as prefix
23370 parameters. An example of this can be illustrated with the
23371 @code{set print} set of parameters. If @var{name} is
23372 @code{print foo}, then @code{print} will be searched as the prefix
23373 parameter. In this case the parameter can subsequently be accessed in
23374 @value{GDBN} as @code{set print foo}.
23376 If @var{name} consists of multiple words, and no prefix parameter group
23377 can be found, an exception is raised.
23379 @var{command-class} should be one of the @samp{COMMAND_} constants
23380 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23381 categorize the new parameter in the help system.
23383 @var{parameter-class} should be one of the @samp{PARAM_} constants
23384 defined below. This argument tells @value{GDBN} the type of the new
23385 parameter; this information is used for input validation and
23388 If @var{parameter-class} is @code{PARAM_ENUM}, then
23389 @var{enum-sequence} must be a sequence of strings. These strings
23390 represent the possible values for the parameter.
23392 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23393 of a fourth argument will cause an exception to be thrown.
23395 The help text for the new parameter is taken from the Python
23396 documentation string for the parameter's class, if there is one. If
23397 there is no documentation string, a default value is used.
23400 @defvar Parameter.set_doc
23401 If this attribute exists, and is a string, then its value is used as
23402 the help text for this parameter's @code{set} command. The value is
23403 examined when @code{Parameter.__init__} is invoked; subsequent changes
23407 @defvar Parameter.show_doc
23408 If this attribute exists, and is a string, then its value is used as
23409 the help text for this parameter's @code{show} command. The value is
23410 examined when @code{Parameter.__init__} is invoked; subsequent changes
23414 @defvar Parameter.value
23415 The @code{value} attribute holds the underlying value of the
23416 parameter. It can be read and assigned to just as any other
23417 attribute. @value{GDBN} does validation when assignments are made.
23420 There are two methods that should be implemented in any
23421 @code{Parameter} class. These are:
23423 @defun Parameter.get_set_string (self)
23424 @value{GDBN} will call this method when a @var{parameter}'s value has
23425 been changed via the @code{set} API (for example, @kbd{set foo off}).
23426 The @code{value} attribute has already been populated with the new
23427 value and may be used in output. This method must return a string.
23430 @defun Parameter.get_show_string (self, svalue)
23431 @value{GDBN} will call this method when a @var{parameter}'s
23432 @code{show} API has been invoked (for example, @kbd{show foo}). The
23433 argument @code{svalue} receives the string representation of the
23434 current value. This method must return a string.
23437 When a new parameter is defined, its type must be specified. The
23438 available types are represented by constants defined in the @code{gdb}
23442 @findex PARAM_BOOLEAN
23443 @findex gdb.PARAM_BOOLEAN
23444 @item gdb.PARAM_BOOLEAN
23445 The value is a plain boolean. The Python boolean values, @code{True}
23446 and @code{False} are the only valid values.
23448 @findex PARAM_AUTO_BOOLEAN
23449 @findex gdb.PARAM_AUTO_BOOLEAN
23450 @item gdb.PARAM_AUTO_BOOLEAN
23451 The value has three possible states: true, false, and @samp{auto}. In
23452 Python, true and false are represented using boolean constants, and
23453 @samp{auto} is represented using @code{None}.
23455 @findex PARAM_UINTEGER
23456 @findex gdb.PARAM_UINTEGER
23457 @item gdb.PARAM_UINTEGER
23458 The value is an unsigned integer. The value of 0 should be
23459 interpreted to mean ``unlimited''.
23461 @findex PARAM_INTEGER
23462 @findex gdb.PARAM_INTEGER
23463 @item gdb.PARAM_INTEGER
23464 The value is a signed integer. The value of 0 should be interpreted
23465 to mean ``unlimited''.
23467 @findex PARAM_STRING
23468 @findex gdb.PARAM_STRING
23469 @item gdb.PARAM_STRING
23470 The value is a string. When the user modifies the string, any escape
23471 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23472 translated into corresponding characters and encoded into the current
23475 @findex PARAM_STRING_NOESCAPE
23476 @findex gdb.PARAM_STRING_NOESCAPE
23477 @item gdb.PARAM_STRING_NOESCAPE
23478 The value is a string. When the user modifies the string, escapes are
23479 passed through untranslated.
23481 @findex PARAM_OPTIONAL_FILENAME
23482 @findex gdb.PARAM_OPTIONAL_FILENAME
23483 @item gdb.PARAM_OPTIONAL_FILENAME
23484 The value is a either a filename (a string), or @code{None}.
23486 @findex PARAM_FILENAME
23487 @findex gdb.PARAM_FILENAME
23488 @item gdb.PARAM_FILENAME
23489 The value is a filename. This is just like
23490 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23492 @findex PARAM_ZINTEGER
23493 @findex gdb.PARAM_ZINTEGER
23494 @item gdb.PARAM_ZINTEGER
23495 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23496 is interpreted as itself.
23499 @findex gdb.PARAM_ENUM
23500 @item gdb.PARAM_ENUM
23501 The value is a string, which must be one of a collection string
23502 constants provided when the parameter is created.
23505 @node Functions In Python
23506 @subsubsection Writing new convenience functions
23508 @cindex writing convenience functions
23509 @cindex convenience functions in python
23510 @cindex python convenience functions
23511 @tindex gdb.Function
23513 You can implement new convenience functions (@pxref{Convenience Vars})
23514 in Python. A convenience function is an instance of a subclass of the
23515 class @code{gdb.Function}.
23517 @defun Function.__init__ (name)
23518 The initializer for @code{Function} registers the new function with
23519 @value{GDBN}. The argument @var{name} is the name of the function,
23520 a string. The function will be visible to the user as a convenience
23521 variable of type @code{internal function}, whose name is the same as
23522 the given @var{name}.
23524 The documentation for the new function is taken from the documentation
23525 string for the new class.
23528 @defun Function.invoke (@var{*args})
23529 When a convenience function is evaluated, its arguments are converted
23530 to instances of @code{gdb.Value}, and then the function's
23531 @code{invoke} method is called. Note that @value{GDBN} does not
23532 predetermine the arity of convenience functions. Instead, all
23533 available arguments are passed to @code{invoke}, following the
23534 standard Python calling convention. In particular, a convenience
23535 function can have default values for parameters without ill effect.
23537 The return value of this method is used as its value in the enclosing
23538 expression. If an ordinary Python value is returned, it is converted
23539 to a @code{gdb.Value} following the usual rules.
23542 The following code snippet shows how a trivial convenience function can
23543 be implemented in Python:
23546 class Greet (gdb.Function):
23547 """Return string to greet someone.
23548 Takes a name as argument."""
23550 def __init__ (self):
23551 super (Greet, self).__init__ ("greet")
23553 def invoke (self, name):
23554 return "Hello, %s!" % name.string ()
23559 The last line instantiates the class, and is necessary to trigger the
23560 registration of the function with @value{GDBN}. Depending on how the
23561 Python code is read into @value{GDBN}, you may need to import the
23562 @code{gdb} module explicitly.
23564 @node Progspaces In Python
23565 @subsubsection Program Spaces In Python
23567 @cindex progspaces in python
23568 @tindex gdb.Progspace
23570 A program space, or @dfn{progspace}, represents a symbolic view
23571 of an address space.
23572 It consists of all of the objfiles of the program.
23573 @xref{Objfiles In Python}.
23574 @xref{Inferiors and Programs, program spaces}, for more details
23575 about program spaces.
23577 The following progspace-related functions are available in the
23580 @findex gdb.current_progspace
23581 @defun gdb.current_progspace ()
23582 This function returns the program space of the currently selected inferior.
23583 @xref{Inferiors and Programs}.
23586 @findex gdb.progspaces
23587 @defun gdb.progspaces ()
23588 Return a sequence of all the progspaces currently known to @value{GDBN}.
23591 Each progspace is represented by an instance of the @code{gdb.Progspace}
23594 @defvar Progspace.filename
23595 The file name of the progspace as a string.
23598 @defvar Progspace.pretty_printers
23599 The @code{pretty_printers} attribute is a list of functions. It is
23600 used to look up pretty-printers. A @code{Value} is passed to each
23601 function in order; if the function returns @code{None}, then the
23602 search continues. Otherwise, the return value should be an object
23603 which is used to format the value. @xref{Pretty Printing API}, for more
23607 @node Objfiles In Python
23608 @subsubsection Objfiles In Python
23610 @cindex objfiles in python
23611 @tindex gdb.Objfile
23613 @value{GDBN} loads symbols for an inferior from various
23614 symbol-containing files (@pxref{Files}). These include the primary
23615 executable file, any shared libraries used by the inferior, and any
23616 separate debug info files (@pxref{Separate Debug Files}).
23617 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23619 The following objfile-related functions are available in the
23622 @findex gdb.current_objfile
23623 @defun gdb.current_objfile ()
23624 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23625 sets the ``current objfile'' to the corresponding objfile. This
23626 function returns the current objfile. If there is no current objfile,
23627 this function returns @code{None}.
23630 @findex gdb.objfiles
23631 @defun gdb.objfiles ()
23632 Return a sequence of all the objfiles current known to @value{GDBN}.
23633 @xref{Objfiles In Python}.
23636 Each objfile is represented by an instance of the @code{gdb.Objfile}
23639 @defvar Objfile.filename
23640 The file name of the objfile as a string.
23643 @defvar Objfile.pretty_printers
23644 The @code{pretty_printers} attribute is a list of functions. It is
23645 used to look up pretty-printers. A @code{Value} is passed to each
23646 function in order; if the function returns @code{None}, then the
23647 search continues. Otherwise, the return value should be an object
23648 which is used to format the value. @xref{Pretty Printing API}, for more
23652 A @code{gdb.Objfile} object has the following methods:
23654 @defun Objfile.is_valid ()
23655 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23656 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23657 if the object file it refers to is not loaded in @value{GDBN} any
23658 longer. All other @code{gdb.Objfile} methods will throw an exception
23659 if it is invalid at the time the method is called.
23662 @node Frames In Python
23663 @subsubsection Accessing inferior stack frames from Python.
23665 @cindex frames in python
23666 When the debugged program stops, @value{GDBN} is able to analyze its call
23667 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23668 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23669 while its corresponding frame exists in the inferior's stack. If you try
23670 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23671 exception (@pxref{Exception Handling}).
23673 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23677 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23681 The following frame-related functions are available in the @code{gdb} module:
23683 @findex gdb.selected_frame
23684 @defun gdb.selected_frame ()
23685 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23688 @findex gdb.newest_frame
23689 @defun gdb.newest_frame ()
23690 Return the newest frame object for the selected thread.
23693 @defun gdb.frame_stop_reason_string (reason)
23694 Return a string explaining the reason why @value{GDBN} stopped unwinding
23695 frames, as expressed by the given @var{reason} code (an integer, see the
23696 @code{unwind_stop_reason} method further down in this section).
23699 A @code{gdb.Frame} object has the following methods:
23702 @defun Frame.is_valid ()
23703 Returns true if the @code{gdb.Frame} object is valid, false if not.
23704 A frame object can become invalid if the frame it refers to doesn't
23705 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23706 an exception if it is invalid at the time the method is called.
23709 @defun Frame.name ()
23710 Returns the function name of the frame, or @code{None} if it can't be
23714 @defun Frame.type ()
23715 Returns the type of the frame. The value can be one of:
23717 @item gdb.NORMAL_FRAME
23718 An ordinary stack frame.
23720 @item gdb.DUMMY_FRAME
23721 A fake stack frame that was created by @value{GDBN} when performing an
23722 inferior function call.
23724 @item gdb.INLINE_FRAME
23725 A frame representing an inlined function. The function was inlined
23726 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23728 @item gdb.TAILCALL_FRAME
23729 A frame representing a tail call. @xref{Tail Call Frames}.
23731 @item gdb.SIGTRAMP_FRAME
23732 A signal trampoline frame. This is the frame created by the OS when
23733 it calls into a signal handler.
23735 @item gdb.ARCH_FRAME
23736 A fake stack frame representing a cross-architecture call.
23738 @item gdb.SENTINEL_FRAME
23739 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23744 @defun Frame.unwind_stop_reason ()
23745 Return an integer representing the reason why it's not possible to find
23746 more frames toward the outermost frame. Use
23747 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23748 function to a string. The value can be one of:
23751 @item gdb.FRAME_UNWIND_NO_REASON
23752 No particular reason (older frames should be available).
23754 @item gdb.FRAME_UNWIND_NULL_ID
23755 The previous frame's analyzer returns an invalid result.
23757 @item gdb.FRAME_UNWIND_OUTERMOST
23758 This frame is the outermost.
23760 @item gdb.FRAME_UNWIND_UNAVAILABLE
23761 Cannot unwind further, because that would require knowing the
23762 values of registers or memory that have not been collected.
23764 @item gdb.FRAME_UNWIND_INNER_ID
23765 This frame ID looks like it ought to belong to a NEXT frame,
23766 but we got it for a PREV frame. Normally, this is a sign of
23767 unwinder failure. It could also indicate stack corruption.
23769 @item gdb.FRAME_UNWIND_SAME_ID
23770 This frame has the same ID as the previous one. That means
23771 that unwinding further would almost certainly give us another
23772 frame with exactly the same ID, so break the chain. Normally,
23773 this is a sign of unwinder failure. It could also indicate
23776 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23777 The frame unwinder did not find any saved PC, but we needed
23778 one to unwind further.
23780 @item gdb.FRAME_UNWIND_FIRST_ERROR
23781 Any stop reason greater or equal to this value indicates some kind
23782 of error. This special value facilitates writing code that tests
23783 for errors in unwinding in a way that will work correctly even if
23784 the list of the other values is modified in future @value{GDBN}
23785 versions. Using it, you could write:
23787 reason = gdb.selected_frame().unwind_stop_reason ()
23788 reason_str = gdb.frame_stop_reason_string (reason)
23789 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23790 print "An error occured: %s" % reason_str
23797 Returns the frame's resume address.
23800 @defun Frame.block ()
23801 Return the frame's code block. @xref{Blocks In Python}.
23804 @defun Frame.function ()
23805 Return the symbol for the function corresponding to this frame.
23806 @xref{Symbols In Python}.
23809 @defun Frame.older ()
23810 Return the frame that called this frame.
23813 @defun Frame.newer ()
23814 Return the frame called by this frame.
23817 @defun Frame.find_sal ()
23818 Return the frame's symtab and line object.
23819 @xref{Symbol Tables In Python}.
23822 @defun Frame.read_var (variable @r{[}, block@r{]})
23823 Return the value of @var{variable} in this frame. If the optional
23824 argument @var{block} is provided, search for the variable from that
23825 block; otherwise start at the frame's current block (which is
23826 determined by the frame's current program counter). @var{variable}
23827 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23828 @code{gdb.Block} object.
23831 @defun Frame.select ()
23832 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23837 @node Blocks In Python
23838 @subsubsection Accessing frame blocks from Python.
23840 @cindex blocks in python
23843 Within each frame, @value{GDBN} maintains information on each block
23844 stored in that frame. These blocks are organized hierarchically, and
23845 are represented individually in Python as a @code{gdb.Block}.
23846 Please see @ref{Frames In Python}, for a more in-depth discussion on
23847 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23848 detailed technical information on @value{GDBN}'s book-keeping of the
23851 A @code{gdb.Block} is iterable. The iterator returns the symbols
23852 (@pxref{Symbols In Python}) local to the block.
23854 The following block-related functions are available in the @code{gdb}
23857 @findex gdb.block_for_pc
23858 @defun gdb.block_for_pc (pc)
23859 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23860 block cannot be found for the @var{pc} value specified, the function
23861 will return @code{None}.
23864 A @code{gdb.Block} object has the following methods:
23867 @defun Block.is_valid ()
23868 Returns @code{True} if the @code{gdb.Block} object is valid,
23869 @code{False} if not. A block object can become invalid if the block it
23870 refers to doesn't exist anymore in the inferior. All other
23871 @code{gdb.Block} methods will throw an exception if it is invalid at
23872 the time the method is called. The block's validity is also checked
23873 during iteration over symbols of the block.
23877 A @code{gdb.Block} object has the following attributes:
23880 @defvar Block.start
23881 The start address of the block. This attribute is not writable.
23885 The end address of the block. This attribute is not writable.
23888 @defvar Block.function
23889 The name of the block represented as a @code{gdb.Symbol}. If the
23890 block is not named, then this attribute holds @code{None}. This
23891 attribute is not writable.
23894 @defvar Block.superblock
23895 The block containing this block. If this parent block does not exist,
23896 this attribute holds @code{None}. This attribute is not writable.
23899 @defvar Block.global_block
23900 The global block associated with this block. This attribute is not
23904 @defvar Block.static_block
23905 The static block associated with this block. This attribute is not
23909 @defvar Block.is_global
23910 @code{True} if the @code{gdb.Block} object is a global block,
23911 @code{False} if not. This attribute is not
23915 @defvar Block.is_static
23916 @code{True} if the @code{gdb.Block} object is a static block,
23917 @code{False} if not. This attribute is not writable.
23921 @node Symbols In Python
23922 @subsubsection Python representation of Symbols.
23924 @cindex symbols in python
23927 @value{GDBN} represents every variable, function and type as an
23928 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23929 Similarly, Python represents these symbols in @value{GDBN} with the
23930 @code{gdb.Symbol} object.
23932 The following symbol-related functions are available in the @code{gdb}
23935 @findex gdb.lookup_symbol
23936 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23937 This function searches for a symbol by name. The search scope can be
23938 restricted to the parameters defined in the optional domain and block
23941 @var{name} is the name of the symbol. It must be a string. The
23942 optional @var{block} argument restricts the search to symbols visible
23943 in that @var{block}. The @var{block} argument must be a
23944 @code{gdb.Block} object. If omitted, the block for the current frame
23945 is used. The optional @var{domain} argument restricts
23946 the search to the domain type. The @var{domain} argument must be a
23947 domain constant defined in the @code{gdb} module and described later
23950 The result is a tuple of two elements.
23951 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23953 If the symbol is found, the second element is @code{True} if the symbol
23954 is a field of a method's object (e.g., @code{this} in C@t{++}),
23955 otherwise it is @code{False}.
23956 If the symbol is not found, the second element is @code{False}.
23959 @findex gdb.lookup_global_symbol
23960 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23961 This function searches for a global symbol by name.
23962 The search scope can be restricted to by the domain argument.
23964 @var{name} is the name of the symbol. It must be a string.
23965 The optional @var{domain} argument restricts the search to the domain type.
23966 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23967 module and described later in this chapter.
23969 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23973 A @code{gdb.Symbol} object has the following attributes:
23976 @defvar Symbol.type
23977 The type of the symbol or @code{None} if no type is recorded.
23978 This attribute is represented as a @code{gdb.Type} object.
23979 @xref{Types In Python}. This attribute is not writable.
23982 @defvar Symbol.symtab
23983 The symbol table in which the symbol appears. This attribute is
23984 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23985 Python}. This attribute is not writable.
23988 @defvar Symbol.line
23989 The line number in the source code at which the symbol was defined.
23990 This is an integer.
23993 @defvar Symbol.name
23994 The name of the symbol as a string. This attribute is not writable.
23997 @defvar Symbol.linkage_name
23998 The name of the symbol, as used by the linker (i.e., may be mangled).
23999 This attribute is not writable.
24002 @defvar Symbol.print_name
24003 The name of the symbol in a form suitable for output. This is either
24004 @code{name} or @code{linkage_name}, depending on whether the user
24005 asked @value{GDBN} to display demangled or mangled names.
24008 @defvar Symbol.addr_class
24009 The address class of the symbol. This classifies how to find the value
24010 of a symbol. Each address class is a constant defined in the
24011 @code{gdb} module and described later in this chapter.
24014 @defvar Symbol.needs_frame
24015 This is @code{True} if evaluating this symbol's value requires a frame
24016 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24017 local variables will require a frame, but other symbols will not.
24020 @defvar Symbol.is_argument
24021 @code{True} if the symbol is an argument of a function.
24024 @defvar Symbol.is_constant
24025 @code{True} if the symbol is a constant.
24028 @defvar Symbol.is_function
24029 @code{True} if the symbol is a function or a method.
24032 @defvar Symbol.is_variable
24033 @code{True} if the symbol is a variable.
24037 A @code{gdb.Symbol} object has the following methods:
24040 @defun Symbol.is_valid ()
24041 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24042 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24043 the symbol it refers to does not exist in @value{GDBN} any longer.
24044 All other @code{gdb.Symbol} methods will throw an exception if it is
24045 invalid at the time the method is called.
24048 @defun Symbol.value (@r{[}frame@r{]})
24049 Compute the value of the symbol, as a @code{gdb.Value}. For
24050 functions, this computes the address of the function, cast to the
24051 appropriate type. If the symbol requires a frame in order to compute
24052 its value, then @var{frame} must be given. If @var{frame} is not
24053 given, or if @var{frame} is invalid, then this method will throw an
24058 The available domain categories in @code{gdb.Symbol} are represented
24059 as constants in the @code{gdb} module:
24062 @findex SYMBOL_UNDEF_DOMAIN
24063 @findex gdb.SYMBOL_UNDEF_DOMAIN
24064 @item gdb.SYMBOL_UNDEF_DOMAIN
24065 This is used when a domain has not been discovered or none of the
24066 following domains apply. This usually indicates an error either
24067 in the symbol information or in @value{GDBN}'s handling of symbols.
24068 @findex SYMBOL_VAR_DOMAIN
24069 @findex gdb.SYMBOL_VAR_DOMAIN
24070 @item gdb.SYMBOL_VAR_DOMAIN
24071 This domain contains variables, function names, typedef names and enum
24073 @findex SYMBOL_STRUCT_DOMAIN
24074 @findex gdb.SYMBOL_STRUCT_DOMAIN
24075 @item gdb.SYMBOL_STRUCT_DOMAIN
24076 This domain holds struct, union and enum type names.
24077 @findex SYMBOL_LABEL_DOMAIN
24078 @findex gdb.SYMBOL_LABEL_DOMAIN
24079 @item gdb.SYMBOL_LABEL_DOMAIN
24080 This domain contains names of labels (for gotos).
24081 @findex SYMBOL_VARIABLES_DOMAIN
24082 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24083 @item gdb.SYMBOL_VARIABLES_DOMAIN
24084 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24085 contains everything minus functions and types.
24086 @findex SYMBOL_FUNCTIONS_DOMAIN
24087 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24088 @item gdb.SYMBOL_FUNCTION_DOMAIN
24089 This domain contains all functions.
24090 @findex SYMBOL_TYPES_DOMAIN
24091 @findex gdb.SYMBOL_TYPES_DOMAIN
24092 @item gdb.SYMBOL_TYPES_DOMAIN
24093 This domain contains all types.
24096 The available address class categories in @code{gdb.Symbol} are represented
24097 as constants in the @code{gdb} module:
24100 @findex SYMBOL_LOC_UNDEF
24101 @findex gdb.SYMBOL_LOC_UNDEF
24102 @item gdb.SYMBOL_LOC_UNDEF
24103 If this is returned by address class, it indicates an error either in
24104 the symbol information or in @value{GDBN}'s handling of symbols.
24105 @findex SYMBOL_LOC_CONST
24106 @findex gdb.SYMBOL_LOC_CONST
24107 @item gdb.SYMBOL_LOC_CONST
24108 Value is constant int.
24109 @findex SYMBOL_LOC_STATIC
24110 @findex gdb.SYMBOL_LOC_STATIC
24111 @item gdb.SYMBOL_LOC_STATIC
24112 Value is at a fixed address.
24113 @findex SYMBOL_LOC_REGISTER
24114 @findex gdb.SYMBOL_LOC_REGISTER
24115 @item gdb.SYMBOL_LOC_REGISTER
24116 Value is in a register.
24117 @findex SYMBOL_LOC_ARG
24118 @findex gdb.SYMBOL_LOC_ARG
24119 @item gdb.SYMBOL_LOC_ARG
24120 Value is an argument. This value is at the offset stored within the
24121 symbol inside the frame's argument list.
24122 @findex SYMBOL_LOC_REF_ARG
24123 @findex gdb.SYMBOL_LOC_REF_ARG
24124 @item gdb.SYMBOL_LOC_REF_ARG
24125 Value address is stored in the frame's argument list. Just like
24126 @code{LOC_ARG} except that the value's address is stored at the
24127 offset, not the value itself.
24128 @findex SYMBOL_LOC_REGPARM_ADDR
24129 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24130 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24131 Value is a specified register. Just like @code{LOC_REGISTER} except
24132 the register holds the address of the argument instead of the argument
24134 @findex SYMBOL_LOC_LOCAL
24135 @findex gdb.SYMBOL_LOC_LOCAL
24136 @item gdb.SYMBOL_LOC_LOCAL
24137 Value is a local variable.
24138 @findex SYMBOL_LOC_TYPEDEF
24139 @findex gdb.SYMBOL_LOC_TYPEDEF
24140 @item gdb.SYMBOL_LOC_TYPEDEF
24141 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24143 @findex SYMBOL_LOC_BLOCK
24144 @findex gdb.SYMBOL_LOC_BLOCK
24145 @item gdb.SYMBOL_LOC_BLOCK
24147 @findex SYMBOL_LOC_CONST_BYTES
24148 @findex gdb.SYMBOL_LOC_CONST_BYTES
24149 @item gdb.SYMBOL_LOC_CONST_BYTES
24150 Value is a byte-sequence.
24151 @findex SYMBOL_LOC_UNRESOLVED
24152 @findex gdb.SYMBOL_LOC_UNRESOLVED
24153 @item gdb.SYMBOL_LOC_UNRESOLVED
24154 Value is at a fixed address, but the address of the variable has to be
24155 determined from the minimal symbol table whenever the variable is
24157 @findex SYMBOL_LOC_OPTIMIZED_OUT
24158 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24159 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24160 The value does not actually exist in the program.
24161 @findex SYMBOL_LOC_COMPUTED
24162 @findex gdb.SYMBOL_LOC_COMPUTED
24163 @item gdb.SYMBOL_LOC_COMPUTED
24164 The value's address is a computed location.
24167 @node Symbol Tables In Python
24168 @subsubsection Symbol table representation in Python.
24170 @cindex symbol tables in python
24172 @tindex gdb.Symtab_and_line
24174 Access to symbol table data maintained by @value{GDBN} on the inferior
24175 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24176 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24177 from the @code{find_sal} method in @code{gdb.Frame} object.
24178 @xref{Frames In Python}.
24180 For more information on @value{GDBN}'s symbol table management, see
24181 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24183 A @code{gdb.Symtab_and_line} object has the following attributes:
24186 @defvar Symtab_and_line.symtab
24187 The symbol table object (@code{gdb.Symtab}) for this frame.
24188 This attribute is not writable.
24191 @defvar Symtab_and_line.pc
24192 Indicates the current program counter address. This attribute is not
24196 @defvar Symtab_and_line.line
24197 Indicates the current line number for this object. This
24198 attribute is not writable.
24202 A @code{gdb.Symtab_and_line} object has the following methods:
24205 @defun Symtab_and_line.is_valid ()
24206 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24207 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24208 invalid if the Symbol table and line object it refers to does not
24209 exist in @value{GDBN} any longer. All other
24210 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24211 invalid at the time the method is called.
24215 A @code{gdb.Symtab} object has the following attributes:
24218 @defvar Symtab.filename
24219 The symbol table's source filename. This attribute is not writable.
24222 @defvar Symtab.objfile
24223 The symbol table's backing object file. @xref{Objfiles In Python}.
24224 This attribute is not writable.
24228 A @code{gdb.Symtab} object has the following methods:
24231 @defun Symtab.is_valid ()
24232 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24233 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24234 the symbol table it refers to does not exist in @value{GDBN} any
24235 longer. All other @code{gdb.Symtab} methods will throw an exception
24236 if it is invalid at the time the method is called.
24239 @defun Symtab.fullname ()
24240 Return the symbol table's source absolute file name.
24244 @node Breakpoints In Python
24245 @subsubsection Manipulating breakpoints using Python
24247 @cindex breakpoints in python
24248 @tindex gdb.Breakpoint
24250 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24253 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24254 Create a new breakpoint. @var{spec} is a string naming the
24255 location of the breakpoint, or an expression that defines a
24256 watchpoint. The contents can be any location recognized by the
24257 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24258 command. The optional @var{type} denotes the breakpoint to create
24259 from the types defined later in this chapter. This argument can be
24260 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24261 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24262 allows the breakpoint to become invisible to the user. The breakpoint
24263 will neither be reported when created, nor will it be listed in the
24264 output from @code{info breakpoints} (but will be listed with the
24265 @code{maint info breakpoints} command). The optional @var{wp_class}
24266 argument defines the class of watchpoint to create, if @var{type} is
24267 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24268 assumed to be a @code{gdb.WP_WRITE} class.
24271 @defun Breakpoint.stop (self)
24272 The @code{gdb.Breakpoint} class can be sub-classed and, in
24273 particular, you may choose to implement the @code{stop} method.
24274 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24275 it will be called when the inferior reaches any location of a
24276 breakpoint which instantiates that sub-class. If the method returns
24277 @code{True}, the inferior will be stopped at the location of the
24278 breakpoint, otherwise the inferior will continue.
24280 If there are multiple breakpoints at the same location with a
24281 @code{stop} method, each one will be called regardless of the
24282 return status of the previous. This ensures that all @code{stop}
24283 methods have a chance to execute at that location. In this scenario
24284 if one of the methods returns @code{True} but the others return
24285 @code{False}, the inferior will still be stopped.
24287 You should not alter the execution state of the inferior (i.e.@:, step,
24288 next, etc.), alter the current frame context (i.e.@:, change the current
24289 active frame), or alter, add or delete any breakpoint. As a general
24290 rule, you should not alter any data within @value{GDBN} or the inferior
24293 Example @code{stop} implementation:
24296 class MyBreakpoint (gdb.Breakpoint):
24298 inf_val = gdb.parse_and_eval("foo")
24305 The available watchpoint types represented by constants are defined in the
24310 @findex gdb.WP_READ
24312 Read only watchpoint.
24315 @findex gdb.WP_WRITE
24317 Write only watchpoint.
24320 @findex gdb.WP_ACCESS
24321 @item gdb.WP_ACCESS
24322 Read/Write watchpoint.
24325 @defun Breakpoint.is_valid ()
24326 Return @code{True} if this @code{Breakpoint} object is valid,
24327 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24328 if the user deletes the breakpoint. In this case, the object still
24329 exists, but the underlying breakpoint does not. In the cases of
24330 watchpoint scope, the watchpoint remains valid even if execution of the
24331 inferior leaves the scope of that watchpoint.
24334 @defun Breakpoint.delete
24335 Permanently deletes the @value{GDBN} breakpoint. This also
24336 invalidates the Python @code{Breakpoint} object. Any further access
24337 to this object's attributes or methods will raise an error.
24340 @defvar Breakpoint.enabled
24341 This attribute is @code{True} if the breakpoint is enabled, and
24342 @code{False} otherwise. This attribute is writable.
24345 @defvar Breakpoint.silent
24346 This attribute is @code{True} if the breakpoint is silent, and
24347 @code{False} otherwise. This attribute is writable.
24349 Note that a breakpoint can also be silent if it has commands and the
24350 first command is @code{silent}. This is not reported by the
24351 @code{silent} attribute.
24354 @defvar Breakpoint.thread
24355 If the breakpoint is thread-specific, this attribute holds the thread
24356 id. If the breakpoint is not thread-specific, this attribute is
24357 @code{None}. This attribute is writable.
24360 @defvar Breakpoint.task
24361 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24362 id. If the breakpoint is not task-specific (or the underlying
24363 language is not Ada), this attribute is @code{None}. This attribute
24367 @defvar Breakpoint.ignore_count
24368 This attribute holds the ignore count for the breakpoint, an integer.
24369 This attribute is writable.
24372 @defvar Breakpoint.number
24373 This attribute holds the breakpoint's number --- the identifier used by
24374 the user to manipulate the breakpoint. This attribute is not writable.
24377 @defvar Breakpoint.type
24378 This attribute holds the breakpoint's type --- the identifier used to
24379 determine the actual breakpoint type or use-case. This attribute is not
24383 @defvar Breakpoint.visible
24384 This attribute tells whether the breakpoint is visible to the user
24385 when set, or when the @samp{info breakpoints} command is run. This
24386 attribute is not writable.
24389 The available types are represented by constants defined in the @code{gdb}
24393 @findex BP_BREAKPOINT
24394 @findex gdb.BP_BREAKPOINT
24395 @item gdb.BP_BREAKPOINT
24396 Normal code breakpoint.
24398 @findex BP_WATCHPOINT
24399 @findex gdb.BP_WATCHPOINT
24400 @item gdb.BP_WATCHPOINT
24401 Watchpoint breakpoint.
24403 @findex BP_HARDWARE_WATCHPOINT
24404 @findex gdb.BP_HARDWARE_WATCHPOINT
24405 @item gdb.BP_HARDWARE_WATCHPOINT
24406 Hardware assisted watchpoint.
24408 @findex BP_READ_WATCHPOINT
24409 @findex gdb.BP_READ_WATCHPOINT
24410 @item gdb.BP_READ_WATCHPOINT
24411 Hardware assisted read watchpoint.
24413 @findex BP_ACCESS_WATCHPOINT
24414 @findex gdb.BP_ACCESS_WATCHPOINT
24415 @item gdb.BP_ACCESS_WATCHPOINT
24416 Hardware assisted access watchpoint.
24419 @defvar Breakpoint.hit_count
24420 This attribute holds the hit count for the breakpoint, an integer.
24421 This attribute is writable, but currently it can only be set to zero.
24424 @defvar Breakpoint.location
24425 This attribute holds the location of the breakpoint, as specified by
24426 the user. It is a string. If the breakpoint does not have a location
24427 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24428 attribute is not writable.
24431 @defvar Breakpoint.expression
24432 This attribute holds a breakpoint expression, as specified by
24433 the user. It is a string. If the breakpoint does not have an
24434 expression (the breakpoint is not a watchpoint) the attribute's value
24435 is @code{None}. This attribute is not writable.
24438 @defvar Breakpoint.condition
24439 This attribute holds the condition of the breakpoint, as specified by
24440 the user. It is a string. If there is no condition, this attribute's
24441 value is @code{None}. This attribute is writable.
24444 @defvar Breakpoint.commands
24445 This attribute holds the commands attached to the breakpoint. If
24446 there are commands, this attribute's value is a string holding all the
24447 commands, separated by newlines. If there are no commands, this
24448 attribute is @code{None}. This attribute is not writable.
24451 @node Finish Breakpoints in Python
24452 @subsubsection Finish Breakpoints
24454 @cindex python finish breakpoints
24455 @tindex gdb.FinishBreakpoint
24457 A finish breakpoint is a temporary breakpoint set at the return address of
24458 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24459 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24460 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24461 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24462 Finish breakpoints are thread specific and must be create with the right
24465 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24466 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24467 object @var{frame}. If @var{frame} is not provided, this defaults to the
24468 newest frame. The optional @var{internal} argument allows the breakpoint to
24469 become invisible to the user. @xref{Breakpoints In Python}, for further
24470 details about this argument.
24473 @defun FinishBreakpoint.out_of_scope (self)
24474 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24475 @code{return} command, @dots{}), a function may not properly terminate, and
24476 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24477 situation, the @code{out_of_scope} callback will be triggered.
24479 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24483 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24485 print "normal finish"
24488 def out_of_scope ():
24489 print "abnormal finish"
24493 @defvar FinishBreakpoint.return_value
24494 When @value{GDBN} is stopped at a finish breakpoint and the frame
24495 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24496 attribute will contain a @code{gdb.Value} object corresponding to the return
24497 value of the function. The value will be @code{None} if the function return
24498 type is @code{void} or if the return value was not computable. This attribute
24502 @node Lazy Strings In Python
24503 @subsubsection Python representation of lazy strings.
24505 @cindex lazy strings in python
24506 @tindex gdb.LazyString
24508 A @dfn{lazy string} is a string whose contents is not retrieved or
24509 encoded until it is needed.
24511 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24512 @code{address} that points to a region of memory, an @code{encoding}
24513 that will be used to encode that region of memory, and a @code{length}
24514 to delimit the region of memory that represents the string. The
24515 difference between a @code{gdb.LazyString} and a string wrapped within
24516 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24517 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24518 retrieved and encoded during printing, while a @code{gdb.Value}
24519 wrapping a string is immediately retrieved and encoded on creation.
24521 A @code{gdb.LazyString} object has the following functions:
24523 @defun LazyString.value ()
24524 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24525 will point to the string in memory, but will lose all the delayed
24526 retrieval, encoding and handling that @value{GDBN} applies to a
24527 @code{gdb.LazyString}.
24530 @defvar LazyString.address
24531 This attribute holds the address of the string. This attribute is not
24535 @defvar LazyString.length
24536 This attribute holds the length of the string in characters. If the
24537 length is -1, then the string will be fetched and encoded up to the
24538 first null of appropriate width. This attribute is not writable.
24541 @defvar LazyString.encoding
24542 This attribute holds the encoding that will be applied to the string
24543 when the string is printed by @value{GDBN}. If the encoding is not
24544 set, or contains an empty string, then @value{GDBN} will select the
24545 most appropriate encoding when the string is printed. This attribute
24549 @defvar LazyString.type
24550 This attribute holds the type that is represented by the lazy string's
24551 type. For a lazy string this will always be a pointer type. To
24552 resolve this to the lazy string's character type, use the type's
24553 @code{target} method. @xref{Types In Python}. This attribute is not
24558 @subsection Auto-loading
24559 @cindex auto-loading, Python
24561 When a new object file is read (for example, due to the @code{file}
24562 command, or because the inferior has loaded a shared library),
24563 @value{GDBN} will look for Python support scripts in several ways:
24564 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24567 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24568 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24569 * Which flavor to choose?::
24572 The auto-loading feature is useful for supplying application-specific
24573 debugging commands and scripts.
24575 Auto-loading can be enabled or disabled,
24576 and the list of auto-loaded scripts can be printed.
24579 @kindex set auto-load-scripts
24580 @item set auto-load-scripts [yes|no]
24581 Enable or disable the auto-loading of Python scripts.
24583 @kindex show auto-load-scripts
24584 @item show auto-load-scripts
24585 Show whether auto-loading of Python scripts is enabled or disabled.
24587 @kindex info auto-load-scripts
24588 @cindex print list of auto-loaded scripts
24589 @item info auto-load-scripts [@var{regexp}]
24590 Print the list of all scripts that @value{GDBN} auto-loaded.
24592 Also printed is the list of scripts that were mentioned in
24593 the @code{.debug_gdb_scripts} section and were not found
24594 (@pxref{.debug_gdb_scripts section}).
24595 This is useful because their names are not printed when @value{GDBN}
24596 tries to load them and fails. There may be many of them, and printing
24597 an error message for each one is problematic.
24599 If @var{regexp} is supplied only scripts with matching names are printed.
24604 (gdb) info auto-load-scripts
24606 Yes py-section-script.py
24607 full name: /tmp/py-section-script.py
24608 Missing my-foo-pretty-printers.py
24612 When reading an auto-loaded file, @value{GDBN} sets the
24613 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24614 function (@pxref{Objfiles In Python}). This can be useful for
24615 registering objfile-specific pretty-printers.
24617 @node objfile-gdb.py file
24618 @subsubsection The @file{@var{objfile}-gdb.py} file
24619 @cindex @file{@var{objfile}-gdb.py}
24621 When a new object file is read, @value{GDBN} looks for
24622 a file named @file{@var{objfile}-gdb.py},
24623 where @var{objfile} is the object file's real name, formed by ensuring
24624 that the file name is absolute, following all symlinks, and resolving
24625 @code{.} and @code{..} components. If this file exists and is
24626 readable, @value{GDBN} will evaluate it as a Python script.
24628 If this file does not exist, and if the parameter
24629 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24630 then @value{GDBN} will look for @var{real-name} in all of the
24631 directories mentioned in the value of @code{debug-file-directory}.
24633 Finally, if this file does not exist, then @value{GDBN} will look for
24634 a file named @file{@var{data-directory}/auto-load/@var{real-name}}, where
24635 @var{data-directory} is @value{GDBN}'s data directory (available via
24636 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24637 is the object file's real name, as described above.
24639 @value{GDBN} does not track which files it has already auto-loaded this way.
24640 @value{GDBN} will load the associated script every time the corresponding
24641 @var{objfile} is opened.
24642 So your @file{-gdb.py} file should be careful to avoid errors if it
24643 is evaluated more than once.
24645 @node .debug_gdb_scripts section
24646 @subsubsection The @code{.debug_gdb_scripts} section
24647 @cindex @code{.debug_gdb_scripts} section
24649 For systems using file formats like ELF and COFF,
24650 when @value{GDBN} loads a new object file
24651 it will look for a special section named @samp{.debug_gdb_scripts}.
24652 If this section exists, its contents is a list of names of scripts to load.
24654 @value{GDBN} will look for each specified script file first in the
24655 current directory and then along the source search path
24656 (@pxref{Source Path, ,Specifying Source Directories}),
24657 except that @file{$cdir} is not searched, since the compilation
24658 directory is not relevant to scripts.
24660 Entries can be placed in section @code{.debug_gdb_scripts} with,
24661 for example, this GCC macro:
24664 /* Note: The "MS" section flags are to remove duplicates. */
24665 #define DEFINE_GDB_SCRIPT(script_name) \
24667 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24669 .asciz \"" script_name "\"\n\
24675 Then one can reference the macro in a header or source file like this:
24678 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24681 The script name may include directories if desired.
24683 If the macro is put in a header, any application or library
24684 using this header will get a reference to the specified script.
24686 @node Which flavor to choose?
24687 @subsubsection Which flavor to choose?
24689 Given the multiple ways of auto-loading Python scripts, it might not always
24690 be clear which one to choose. This section provides some guidance.
24692 Benefits of the @file{-gdb.py} way:
24696 Can be used with file formats that don't support multiple sections.
24699 Ease of finding scripts for public libraries.
24701 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24702 in the source search path.
24703 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24704 isn't a source directory in which to find the script.
24707 Doesn't require source code additions.
24710 Benefits of the @code{.debug_gdb_scripts} way:
24714 Works with static linking.
24716 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24717 trigger their loading. When an application is statically linked the only
24718 objfile available is the executable, and it is cumbersome to attach all the
24719 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24722 Works with classes that are entirely inlined.
24724 Some classes can be entirely inlined, and thus there may not be an associated
24725 shared library to attach a @file{-gdb.py} script to.
24728 Scripts needn't be copied out of the source tree.
24730 In some circumstances, apps can be built out of large collections of internal
24731 libraries, and the build infrastructure necessary to install the
24732 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24733 cumbersome. It may be easier to specify the scripts in the
24734 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24735 top of the source tree to the source search path.
24738 @node Python modules
24739 @subsection Python modules
24740 @cindex python modules
24742 @value{GDBN} comes with several modules to assist writing Python code.
24745 * gdb.printing:: Building and registering pretty-printers.
24746 * gdb.types:: Utilities for working with types.
24747 * gdb.prompt:: Utilities for prompt value substitution.
24751 @subsubsection gdb.printing
24752 @cindex gdb.printing
24754 This module provides a collection of utilities for working with
24758 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24759 This class specifies the API that makes @samp{info pretty-printer},
24760 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24761 Pretty-printers should generally inherit from this class.
24763 @item SubPrettyPrinter (@var{name})
24764 For printers that handle multiple types, this class specifies the
24765 corresponding API for the subprinters.
24767 @item RegexpCollectionPrettyPrinter (@var{name})
24768 Utility class for handling multiple printers, all recognized via
24769 regular expressions.
24770 @xref{Writing a Pretty-Printer}, for an example.
24772 @item FlagEnumerationPrinter (@var{name})
24773 A pretty-printer which handles printing of @code{enum} values. Unlike
24774 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
24775 work properly when there is some overlap between the enumeration
24776 constants. @var{name} is the name of the printer and also the name of
24777 the @code{enum} type to look up.
24779 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24780 Register @var{printer} with the pretty-printer list of @var{obj}.
24781 If @var{replace} is @code{True} then any existing copy of the printer
24782 is replaced. Otherwise a @code{RuntimeError} exception is raised
24783 if a printer with the same name already exists.
24787 @subsubsection gdb.types
24790 This module provides a collection of utilities for working with
24791 @code{gdb.Types} objects.
24794 @item get_basic_type (@var{type})
24795 Return @var{type} with const and volatile qualifiers stripped,
24796 and with typedefs and C@t{++} references converted to the underlying type.
24801 typedef const int const_int;
24803 const_int& foo_ref (foo);
24804 int main () @{ return 0; @}
24811 (gdb) python import gdb.types
24812 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24813 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24817 @item has_field (@var{type}, @var{field})
24818 Return @code{True} if @var{type}, assumed to be a type with fields
24819 (e.g., a structure or union), has field @var{field}.
24821 @item make_enum_dict (@var{enum_type})
24822 Return a Python @code{dictionary} type produced from @var{enum_type}.
24824 @item deep_items (@var{type})
24825 Returns a Python iterator similar to the standard
24826 @code{gdb.Type.iteritems} method, except that the iterator returned
24827 by @code{deep_items} will recursively traverse anonymous struct or
24828 union fields. For example:
24842 Then in @value{GDBN}:
24844 (@value{GDBP}) python import gdb.types
24845 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24846 (@value{GDBP}) python print struct_a.keys ()
24848 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24849 @{['a', 'b0', 'b1']@}
24855 @subsubsection gdb.prompt
24858 This module provides a method for prompt value-substitution.
24861 @item substitute_prompt (@var{string})
24862 Return @var{string} with escape sequences substituted by values. Some
24863 escape sequences take arguments. You can specify arguments inside
24864 ``@{@}'' immediately following the escape sequence.
24866 The escape sequences you can pass to this function are:
24870 Substitute a backslash.
24872 Substitute an ESC character.
24874 Substitute the selected frame; an argument names a frame parameter.
24876 Substitute a newline.
24878 Substitute a parameter's value; the argument names the parameter.
24880 Substitute a carriage return.
24882 Substitute the selected thread; an argument names a thread parameter.
24884 Substitute the version of GDB.
24886 Substitute the current working directory.
24888 Begin a sequence of non-printing characters. These sequences are
24889 typically used with the ESC character, and are not counted in the string
24890 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24891 blue-colored ``(gdb)'' prompt where the length is five.
24893 End a sequence of non-printing characters.
24899 substitute_prompt (``frame: \f,
24900 print arguments: \p@{print frame-arguments@}'')
24903 @exdent will return the string:
24906 "frame: main, print arguments: scalars"
24911 @section Creating new spellings of existing commands
24912 @cindex aliases for commands
24914 It is often useful to define alternate spellings of existing commands.
24915 For example, if a new @value{GDBN} command defined in Python has
24916 a long name to type, it is handy to have an abbreviated version of it
24917 that involves less typing.
24919 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24920 of the @samp{step} command even though it is otherwise an ambiguous
24921 abbreviation of other commands like @samp{set} and @samp{show}.
24923 Aliases are also used to provide shortened or more common versions
24924 of multi-word commands. For example, @value{GDBN} provides the
24925 @samp{tty} alias of the @samp{set inferior-tty} command.
24927 You can define a new alias with the @samp{alias} command.
24932 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24936 @var{ALIAS} specifies the name of the new alias.
24937 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24940 @var{COMMAND} specifies the name of an existing command
24941 that is being aliased.
24943 The @samp{-a} option specifies that the new alias is an abbreviation
24944 of the command. Abbreviations are not shown in command
24945 lists displayed by the @samp{help} command.
24947 The @samp{--} option specifies the end of options,
24948 and is useful when @var{ALIAS} begins with a dash.
24950 Here is a simple example showing how to make an abbreviation
24951 of a command so that there is less to type.
24952 Suppose you were tired of typing @samp{disas}, the current
24953 shortest unambiguous abbreviation of the @samp{disassemble} command
24954 and you wanted an even shorter version named @samp{di}.
24955 The following will accomplish this.
24958 (gdb) alias -a di = disas
24961 Note that aliases are different from user-defined commands.
24962 With a user-defined command, you also need to write documentation
24963 for it with the @samp{document} command.
24964 An alias automatically picks up the documentation of the existing command.
24966 Here is an example where we make @samp{elms} an abbreviation of
24967 @samp{elements} in the @samp{set print elements} command.
24968 This is to show that you can make an abbreviation of any part
24972 (gdb) alias -a set print elms = set print elements
24973 (gdb) alias -a show print elms = show print elements
24974 (gdb) set p elms 20
24976 Limit on string chars or array elements to print is 200.
24979 Note that if you are defining an alias of a @samp{set} command,
24980 and you want to have an alias for the corresponding @samp{show}
24981 command, then you need to define the latter separately.
24983 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24984 @var{ALIAS}, just as they are normally.
24987 (gdb) alias -a set pr elms = set p ele
24990 Finally, here is an example showing the creation of a one word
24991 alias for a more complex command.
24992 This creates alias @samp{spe} of the command @samp{set print elements}.
24995 (gdb) alias spe = set print elements
25000 @chapter Command Interpreters
25001 @cindex command interpreters
25003 @value{GDBN} supports multiple command interpreters, and some command
25004 infrastructure to allow users or user interface writers to switch
25005 between interpreters or run commands in other interpreters.
25007 @value{GDBN} currently supports two command interpreters, the console
25008 interpreter (sometimes called the command-line interpreter or @sc{cli})
25009 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25010 describes both of these interfaces in great detail.
25012 By default, @value{GDBN} will start with the console interpreter.
25013 However, the user may choose to start @value{GDBN} with another
25014 interpreter by specifying the @option{-i} or @option{--interpreter}
25015 startup options. Defined interpreters include:
25019 @cindex console interpreter
25020 The traditional console or command-line interpreter. This is the most often
25021 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25022 @value{GDBN} will use this interpreter.
25025 @cindex mi interpreter
25026 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25027 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25028 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25032 @cindex mi2 interpreter
25033 The current @sc{gdb/mi} interface.
25036 @cindex mi1 interpreter
25037 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25041 @cindex invoke another interpreter
25042 The interpreter being used by @value{GDBN} may not be dynamically
25043 switched at runtime. Although possible, this could lead to a very
25044 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25045 enters the command "interpreter-set console" in a console view,
25046 @value{GDBN} would switch to using the console interpreter, rendering
25047 the IDE inoperable!
25049 @kindex interpreter-exec
25050 Although you may only choose a single interpreter at startup, you may execute
25051 commands in any interpreter from the current interpreter using the appropriate
25052 command. If you are running the console interpreter, simply use the
25053 @code{interpreter-exec} command:
25056 interpreter-exec mi "-data-list-register-names"
25059 @sc{gdb/mi} has a similar command, although it is only available in versions of
25060 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25063 @chapter @value{GDBN} Text User Interface
25065 @cindex Text User Interface
25068 * TUI Overview:: TUI overview
25069 * TUI Keys:: TUI key bindings
25070 * TUI Single Key Mode:: TUI single key mode
25071 * TUI Commands:: TUI-specific commands
25072 * TUI Configuration:: TUI configuration variables
25075 The @value{GDBN} Text User Interface (TUI) is a terminal
25076 interface which uses the @code{curses} library to show the source
25077 file, the assembly output, the program registers and @value{GDBN}
25078 commands in separate text windows. The TUI mode is supported only
25079 on platforms where a suitable version of the @code{curses} library
25082 The TUI mode is enabled by default when you invoke @value{GDBN} as
25083 @samp{@value{GDBP} -tui}.
25084 You can also switch in and out of TUI mode while @value{GDBN} runs by
25085 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25086 @xref{TUI Keys, ,TUI Key Bindings}.
25089 @section TUI Overview
25091 In TUI mode, @value{GDBN} can display several text windows:
25095 This window is the @value{GDBN} command window with the @value{GDBN}
25096 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25097 managed using readline.
25100 The source window shows the source file of the program. The current
25101 line and active breakpoints are displayed in this window.
25104 The assembly window shows the disassembly output of the program.
25107 This window shows the processor registers. Registers are highlighted
25108 when their values change.
25111 The source and assembly windows show the current program position
25112 by highlighting the current line and marking it with a @samp{>} marker.
25113 Breakpoints are indicated with two markers. The first marker
25114 indicates the breakpoint type:
25118 Breakpoint which was hit at least once.
25121 Breakpoint which was never hit.
25124 Hardware breakpoint which was hit at least once.
25127 Hardware breakpoint which was never hit.
25130 The second marker indicates whether the breakpoint is enabled or not:
25134 Breakpoint is enabled.
25137 Breakpoint is disabled.
25140 The source, assembly and register windows are updated when the current
25141 thread changes, when the frame changes, or when the program counter
25144 These windows are not all visible at the same time. The command
25145 window is always visible. The others can be arranged in several
25156 source and assembly,
25159 source and registers, or
25162 assembly and registers.
25165 A status line above the command window shows the following information:
25169 Indicates the current @value{GDBN} target.
25170 (@pxref{Targets, ,Specifying a Debugging Target}).
25173 Gives the current process or thread number.
25174 When no process is being debugged, this field is set to @code{No process}.
25177 Gives the current function name for the selected frame.
25178 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25179 When there is no symbol corresponding to the current program counter,
25180 the string @code{??} is displayed.
25183 Indicates the current line number for the selected frame.
25184 When the current line number is not known, the string @code{??} is displayed.
25187 Indicates the current program counter address.
25191 @section TUI Key Bindings
25192 @cindex TUI key bindings
25194 The TUI installs several key bindings in the readline keymaps
25195 @ifset SYSTEM_READLINE
25196 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25198 @ifclear SYSTEM_READLINE
25199 (@pxref{Command Line Editing}).
25201 The following key bindings are installed for both TUI mode and the
25202 @value{GDBN} standard mode.
25211 Enter or leave the TUI mode. When leaving the TUI mode,
25212 the curses window management stops and @value{GDBN} operates using
25213 its standard mode, writing on the terminal directly. When reentering
25214 the TUI mode, control is given back to the curses windows.
25215 The screen is then refreshed.
25219 Use a TUI layout with only one window. The layout will
25220 either be @samp{source} or @samp{assembly}. When the TUI mode
25221 is not active, it will switch to the TUI mode.
25223 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25227 Use a TUI layout with at least two windows. When the current
25228 layout already has two windows, the next layout with two windows is used.
25229 When a new layout is chosen, one window will always be common to the
25230 previous layout and the new one.
25232 Think of it as the Emacs @kbd{C-x 2} binding.
25236 Change the active window. The TUI associates several key bindings
25237 (like scrolling and arrow keys) with the active window. This command
25238 gives the focus to the next TUI window.
25240 Think of it as the Emacs @kbd{C-x o} binding.
25244 Switch in and out of the TUI SingleKey mode that binds single
25245 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25248 The following key bindings only work in the TUI mode:
25253 Scroll the active window one page up.
25257 Scroll the active window one page down.
25261 Scroll the active window one line up.
25265 Scroll the active window one line down.
25269 Scroll the active window one column left.
25273 Scroll the active window one column right.
25277 Refresh the screen.
25280 Because the arrow keys scroll the active window in the TUI mode, they
25281 are not available for their normal use by readline unless the command
25282 window has the focus. When another window is active, you must use
25283 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25284 and @kbd{C-f} to control the command window.
25286 @node TUI Single Key Mode
25287 @section TUI Single Key Mode
25288 @cindex TUI single key mode
25290 The TUI also provides a @dfn{SingleKey} mode, which binds several
25291 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25292 switch into this mode, where the following key bindings are used:
25295 @kindex c @r{(SingleKey TUI key)}
25299 @kindex d @r{(SingleKey TUI key)}
25303 @kindex f @r{(SingleKey TUI key)}
25307 @kindex n @r{(SingleKey TUI key)}
25311 @kindex q @r{(SingleKey TUI key)}
25313 exit the SingleKey mode.
25315 @kindex r @r{(SingleKey TUI key)}
25319 @kindex s @r{(SingleKey TUI key)}
25323 @kindex u @r{(SingleKey TUI key)}
25327 @kindex v @r{(SingleKey TUI key)}
25331 @kindex w @r{(SingleKey TUI key)}
25336 Other keys temporarily switch to the @value{GDBN} command prompt.
25337 The key that was pressed is inserted in the editing buffer so that
25338 it is possible to type most @value{GDBN} commands without interaction
25339 with the TUI SingleKey mode. Once the command is entered the TUI
25340 SingleKey mode is restored. The only way to permanently leave
25341 this mode is by typing @kbd{q} or @kbd{C-x s}.
25345 @section TUI-specific Commands
25346 @cindex TUI commands
25348 The TUI has specific commands to control the text windows.
25349 These commands are always available, even when @value{GDBN} is not in
25350 the TUI mode. When @value{GDBN} is in the standard mode, most
25351 of these commands will automatically switch to the TUI mode.
25353 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25354 terminal, or @value{GDBN} has been started with the machine interface
25355 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25356 these commands will fail with an error, because it would not be
25357 possible or desirable to enable curses window management.
25362 List and give the size of all displayed windows.
25366 Display the next layout.
25369 Display the previous layout.
25372 Display the source window only.
25375 Display the assembly window only.
25378 Display the source and assembly window.
25381 Display the register window together with the source or assembly window.
25385 Make the next window active for scrolling.
25388 Make the previous window active for scrolling.
25391 Make the source window active for scrolling.
25394 Make the assembly window active for scrolling.
25397 Make the register window active for scrolling.
25400 Make the command window active for scrolling.
25404 Refresh the screen. This is similar to typing @kbd{C-L}.
25406 @item tui reg float
25408 Show the floating point registers in the register window.
25410 @item tui reg general
25411 Show the general registers in the register window.
25414 Show the next register group. The list of register groups as well as
25415 their order is target specific. The predefined register groups are the
25416 following: @code{general}, @code{float}, @code{system}, @code{vector},
25417 @code{all}, @code{save}, @code{restore}.
25419 @item tui reg system
25420 Show the system registers in the register window.
25424 Update the source window and the current execution point.
25426 @item winheight @var{name} +@var{count}
25427 @itemx winheight @var{name} -@var{count}
25429 Change the height of the window @var{name} by @var{count}
25430 lines. Positive counts increase the height, while negative counts
25433 @item tabset @var{nchars}
25435 Set the width of tab stops to be @var{nchars} characters.
25438 @node TUI Configuration
25439 @section TUI Configuration Variables
25440 @cindex TUI configuration variables
25442 Several configuration variables control the appearance of TUI windows.
25445 @item set tui border-kind @var{kind}
25446 @kindex set tui border-kind
25447 Select the border appearance for the source, assembly and register windows.
25448 The possible values are the following:
25451 Use a space character to draw the border.
25454 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25457 Use the Alternate Character Set to draw the border. The border is
25458 drawn using character line graphics if the terminal supports them.
25461 @item set tui border-mode @var{mode}
25462 @kindex set tui border-mode
25463 @itemx set tui active-border-mode @var{mode}
25464 @kindex set tui active-border-mode
25465 Select the display attributes for the borders of the inactive windows
25466 or the active window. The @var{mode} can be one of the following:
25469 Use normal attributes to display the border.
25475 Use reverse video mode.
25478 Use half bright mode.
25480 @item half-standout
25481 Use half bright and standout mode.
25484 Use extra bright or bold mode.
25486 @item bold-standout
25487 Use extra bright or bold and standout mode.
25492 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25495 @cindex @sc{gnu} Emacs
25496 A special interface allows you to use @sc{gnu} Emacs to view (and
25497 edit) the source files for the program you are debugging with
25500 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25501 executable file you want to debug as an argument. This command starts
25502 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25503 created Emacs buffer.
25504 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25506 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25511 All ``terminal'' input and output goes through an Emacs buffer, called
25514 This applies both to @value{GDBN} commands and their output, and to the input
25515 and output done by the program you are debugging.
25517 This is useful because it means that you can copy the text of previous
25518 commands and input them again; you can even use parts of the output
25521 All the facilities of Emacs' Shell mode are available for interacting
25522 with your program. In particular, you can send signals the usual
25523 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25527 @value{GDBN} displays source code through Emacs.
25529 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25530 source file for that frame and puts an arrow (@samp{=>}) at the
25531 left margin of the current line. Emacs uses a separate buffer for
25532 source display, and splits the screen to show both your @value{GDBN} session
25535 Explicit @value{GDBN} @code{list} or search commands still produce output as
25536 usual, but you probably have no reason to use them from Emacs.
25539 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25540 a graphical mode, enabled by default, which provides further buffers
25541 that can control the execution and describe the state of your program.
25542 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25544 If you specify an absolute file name when prompted for the @kbd{M-x
25545 gdb} argument, then Emacs sets your current working directory to where
25546 your program resides. If you only specify the file name, then Emacs
25547 sets your current working directory to the directory associated
25548 with the previous buffer. In this case, @value{GDBN} may find your
25549 program by searching your environment's @code{PATH} variable, but on
25550 some operating systems it might not find the source. So, although the
25551 @value{GDBN} input and output session proceeds normally, the auxiliary
25552 buffer does not display the current source and line of execution.
25554 The initial working directory of @value{GDBN} is printed on the top
25555 line of the GUD buffer and this serves as a default for the commands
25556 that specify files for @value{GDBN} to operate on. @xref{Files,
25557 ,Commands to Specify Files}.
25559 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25560 need to call @value{GDBN} by a different name (for example, if you
25561 keep several configurations around, with different names) you can
25562 customize the Emacs variable @code{gud-gdb-command-name} to run the
25565 In the GUD buffer, you can use these special Emacs commands in
25566 addition to the standard Shell mode commands:
25570 Describe the features of Emacs' GUD Mode.
25573 Execute to another source line, like the @value{GDBN} @code{step} command; also
25574 update the display window to show the current file and location.
25577 Execute to next source line in this function, skipping all function
25578 calls, like the @value{GDBN} @code{next} command. Then update the display window
25579 to show the current file and location.
25582 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25583 display window accordingly.
25586 Execute until exit from the selected stack frame, like the @value{GDBN}
25587 @code{finish} command.
25590 Continue execution of your program, like the @value{GDBN} @code{continue}
25594 Go up the number of frames indicated by the numeric argument
25595 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25596 like the @value{GDBN} @code{up} command.
25599 Go down the number of frames indicated by the numeric argument, like the
25600 @value{GDBN} @code{down} command.
25603 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25604 tells @value{GDBN} to set a breakpoint on the source line point is on.
25606 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25607 separate frame which shows a backtrace when the GUD buffer is current.
25608 Move point to any frame in the stack and type @key{RET} to make it
25609 become the current frame and display the associated source in the
25610 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25611 selected frame become the current one. In graphical mode, the
25612 speedbar displays watch expressions.
25614 If you accidentally delete the source-display buffer, an easy way to get
25615 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25616 request a frame display; when you run under Emacs, this recreates
25617 the source buffer if necessary to show you the context of the current
25620 The source files displayed in Emacs are in ordinary Emacs buffers
25621 which are visiting the source files in the usual way. You can edit
25622 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25623 communicates with Emacs in terms of line numbers. If you add or
25624 delete lines from the text, the line numbers that @value{GDBN} knows cease
25625 to correspond properly with the code.
25627 A more detailed description of Emacs' interaction with @value{GDBN} is
25628 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25631 @c The following dropped because Epoch is nonstandard. Reactivate
25632 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25634 @kindex Emacs Epoch environment
25638 Version 18 of @sc{gnu} Emacs has a built-in window system
25639 called the @code{epoch}
25640 environment. Users of this environment can use a new command,
25641 @code{inspect} which performs identically to @code{print} except that
25642 each value is printed in its own window.
25647 @chapter The @sc{gdb/mi} Interface
25649 @unnumberedsec Function and Purpose
25651 @cindex @sc{gdb/mi}, its purpose
25652 @sc{gdb/mi} is a line based machine oriented text interface to
25653 @value{GDBN} and is activated by specifying using the
25654 @option{--interpreter} command line option (@pxref{Mode Options}). It
25655 is specifically intended to support the development of systems which
25656 use the debugger as just one small component of a larger system.
25658 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25659 in the form of a reference manual.
25661 Note that @sc{gdb/mi} is still under construction, so some of the
25662 features described below are incomplete and subject to change
25663 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25665 @unnumberedsec Notation and Terminology
25667 @cindex notational conventions, for @sc{gdb/mi}
25668 This chapter uses the following notation:
25672 @code{|} separates two alternatives.
25675 @code{[ @var{something} ]} indicates that @var{something} is optional:
25676 it may or may not be given.
25679 @code{( @var{group} )*} means that @var{group} inside the parentheses
25680 may repeat zero or more times.
25683 @code{( @var{group} )+} means that @var{group} inside the parentheses
25684 may repeat one or more times.
25687 @code{"@var{string}"} means a literal @var{string}.
25691 @heading Dependencies
25695 * GDB/MI General Design::
25696 * GDB/MI Command Syntax::
25697 * GDB/MI Compatibility with CLI::
25698 * GDB/MI Development and Front Ends::
25699 * GDB/MI Output Records::
25700 * GDB/MI Simple Examples::
25701 * GDB/MI Command Description Format::
25702 * GDB/MI Breakpoint Commands::
25703 * GDB/MI Program Context::
25704 * GDB/MI Thread Commands::
25705 * GDB/MI Ada Tasking Commands::
25706 * GDB/MI Program Execution::
25707 * GDB/MI Stack Manipulation::
25708 * GDB/MI Variable Objects::
25709 * GDB/MI Data Manipulation::
25710 * GDB/MI Tracepoint Commands::
25711 * GDB/MI Symbol Query::
25712 * GDB/MI File Commands::
25714 * GDB/MI Kod Commands::
25715 * GDB/MI Memory Overlay Commands::
25716 * GDB/MI Signal Handling Commands::
25718 * GDB/MI Target Manipulation::
25719 * GDB/MI File Transfer Commands::
25720 * GDB/MI Miscellaneous Commands::
25723 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25724 @node GDB/MI General Design
25725 @section @sc{gdb/mi} General Design
25726 @cindex GDB/MI General Design
25728 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25729 parts---commands sent to @value{GDBN}, responses to those commands
25730 and notifications. Each command results in exactly one response,
25731 indicating either successful completion of the command, or an error.
25732 For the commands that do not resume the target, the response contains the
25733 requested information. For the commands that resume the target, the
25734 response only indicates whether the target was successfully resumed.
25735 Notifications is the mechanism for reporting changes in the state of the
25736 target, or in @value{GDBN} state, that cannot conveniently be associated with
25737 a command and reported as part of that command response.
25739 The important examples of notifications are:
25743 Exec notifications. These are used to report changes in
25744 target state---when a target is resumed, or stopped. It would not
25745 be feasible to include this information in response of resuming
25746 commands, because one resume commands can result in multiple events in
25747 different threads. Also, quite some time may pass before any event
25748 happens in the target, while a frontend needs to know whether the resuming
25749 command itself was successfully executed.
25752 Console output, and status notifications. Console output
25753 notifications are used to report output of CLI commands, as well as
25754 diagnostics for other commands. Status notifications are used to
25755 report the progress of a long-running operation. Naturally, including
25756 this information in command response would mean no output is produced
25757 until the command is finished, which is undesirable.
25760 General notifications. Commands may have various side effects on
25761 the @value{GDBN} or target state beyond their official purpose. For example,
25762 a command may change the selected thread. Although such changes can
25763 be included in command response, using notification allows for more
25764 orthogonal frontend design.
25768 There's no guarantee that whenever an MI command reports an error,
25769 @value{GDBN} or the target are in any specific state, and especially,
25770 the state is not reverted to the state before the MI command was
25771 processed. Therefore, whenever an MI command results in an error,
25772 we recommend that the frontend refreshes all the information shown in
25773 the user interface.
25777 * Context management::
25778 * Asynchronous and non-stop modes::
25782 @node Context management
25783 @subsection Context management
25785 In most cases when @value{GDBN} accesses the target, this access is
25786 done in context of a specific thread and frame (@pxref{Frames}).
25787 Often, even when accessing global data, the target requires that a thread
25788 be specified. The CLI interface maintains the selected thread and frame,
25789 and supplies them to target on each command. This is convenient,
25790 because a command line user would not want to specify that information
25791 explicitly on each command, and because user interacts with
25792 @value{GDBN} via a single terminal, so no confusion is possible as
25793 to what thread and frame are the current ones.
25795 In the case of MI, the concept of selected thread and frame is less
25796 useful. First, a frontend can easily remember this information
25797 itself. Second, a graphical frontend can have more than one window,
25798 each one used for debugging a different thread, and the frontend might
25799 want to access additional threads for internal purposes. This
25800 increases the risk that by relying on implicitly selected thread, the
25801 frontend may be operating on a wrong one. Therefore, each MI command
25802 should explicitly specify which thread and frame to operate on. To
25803 make it possible, each MI command accepts the @samp{--thread} and
25804 @samp{--frame} options, the value to each is @value{GDBN} identifier
25805 for thread and frame to operate on.
25807 Usually, each top-level window in a frontend allows the user to select
25808 a thread and a frame, and remembers the user selection for further
25809 operations. However, in some cases @value{GDBN} may suggest that the
25810 current thread be changed. For example, when stopping on a breakpoint
25811 it is reasonable to switch to the thread where breakpoint is hit. For
25812 another example, if the user issues the CLI @samp{thread} command via
25813 the frontend, it is desirable to change the frontend's selected thread to the
25814 one specified by user. @value{GDBN} communicates the suggestion to
25815 change current thread using the @samp{=thread-selected} notification.
25816 No such notification is available for the selected frame at the moment.
25818 Note that historically, MI shares the selected thread with CLI, so
25819 frontends used the @code{-thread-select} to execute commands in the
25820 right context. However, getting this to work right is cumbersome. The
25821 simplest way is for frontend to emit @code{-thread-select} command
25822 before every command. This doubles the number of commands that need
25823 to be sent. The alternative approach is to suppress @code{-thread-select}
25824 if the selected thread in @value{GDBN} is supposed to be identical to the
25825 thread the frontend wants to operate on. However, getting this
25826 optimization right can be tricky. In particular, if the frontend
25827 sends several commands to @value{GDBN}, and one of the commands changes the
25828 selected thread, then the behaviour of subsequent commands will
25829 change. So, a frontend should either wait for response from such
25830 problematic commands, or explicitly add @code{-thread-select} for
25831 all subsequent commands. No frontend is known to do this exactly
25832 right, so it is suggested to just always pass the @samp{--thread} and
25833 @samp{--frame} options.
25835 @node Asynchronous and non-stop modes
25836 @subsection Asynchronous command execution and non-stop mode
25838 On some targets, @value{GDBN} is capable of processing MI commands
25839 even while the target is running. This is called @dfn{asynchronous
25840 command execution} (@pxref{Background Execution}). The frontend may
25841 specify a preferrence for asynchronous execution using the
25842 @code{-gdb-set target-async 1} command, which should be emitted before
25843 either running the executable or attaching to the target. After the
25844 frontend has started the executable or attached to the target, it can
25845 find if asynchronous execution is enabled using the
25846 @code{-list-target-features} command.
25848 Even if @value{GDBN} can accept a command while target is running,
25849 many commands that access the target do not work when the target is
25850 running. Therefore, asynchronous command execution is most useful
25851 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25852 it is possible to examine the state of one thread, while other threads
25855 When a given thread is running, MI commands that try to access the
25856 target in the context of that thread may not work, or may work only on
25857 some targets. In particular, commands that try to operate on thread's
25858 stack will not work, on any target. Commands that read memory, or
25859 modify breakpoints, may work or not work, depending on the target. Note
25860 that even commands that operate on global state, such as @code{print},
25861 @code{set}, and breakpoint commands, still access the target in the
25862 context of a specific thread, so frontend should try to find a
25863 stopped thread and perform the operation on that thread (using the
25864 @samp{--thread} option).
25866 Which commands will work in the context of a running thread is
25867 highly target dependent. However, the two commands
25868 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25869 to find the state of a thread, will always work.
25871 @node Thread groups
25872 @subsection Thread groups
25873 @value{GDBN} may be used to debug several processes at the same time.
25874 On some platfroms, @value{GDBN} may support debugging of several
25875 hardware systems, each one having several cores with several different
25876 processes running on each core. This section describes the MI
25877 mechanism to support such debugging scenarios.
25879 The key observation is that regardless of the structure of the
25880 target, MI can have a global list of threads, because most commands that
25881 accept the @samp{--thread} option do not need to know what process that
25882 thread belongs to. Therefore, it is not necessary to introduce
25883 neither additional @samp{--process} option, nor an notion of the
25884 current process in the MI interface. The only strictly new feature
25885 that is required is the ability to find how the threads are grouped
25888 To allow the user to discover such grouping, and to support arbitrary
25889 hierarchy of machines/cores/processes, MI introduces the concept of a
25890 @dfn{thread group}. Thread group is a collection of threads and other
25891 thread groups. A thread group always has a string identifier, a type,
25892 and may have additional attributes specific to the type. A new
25893 command, @code{-list-thread-groups}, returns the list of top-level
25894 thread groups, which correspond to processes that @value{GDBN} is
25895 debugging at the moment. By passing an identifier of a thread group
25896 to the @code{-list-thread-groups} command, it is possible to obtain
25897 the members of specific thread group.
25899 To allow the user to easily discover processes, and other objects, he
25900 wishes to debug, a concept of @dfn{available thread group} is
25901 introduced. Available thread group is an thread group that
25902 @value{GDBN} is not debugging, but that can be attached to, using the
25903 @code{-target-attach} command. The list of available top-level thread
25904 groups can be obtained using @samp{-list-thread-groups --available}.
25905 In general, the content of a thread group may be only retrieved only
25906 after attaching to that thread group.
25908 Thread groups are related to inferiors (@pxref{Inferiors and
25909 Programs}). Each inferior corresponds to a thread group of a special
25910 type @samp{process}, and some additional operations are permitted on
25911 such thread groups.
25913 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25914 @node GDB/MI Command Syntax
25915 @section @sc{gdb/mi} Command Syntax
25918 * GDB/MI Input Syntax::
25919 * GDB/MI Output Syntax::
25922 @node GDB/MI Input Syntax
25923 @subsection @sc{gdb/mi} Input Syntax
25925 @cindex input syntax for @sc{gdb/mi}
25926 @cindex @sc{gdb/mi}, input syntax
25928 @item @var{command} @expansion{}
25929 @code{@var{cli-command} | @var{mi-command}}
25931 @item @var{cli-command} @expansion{}
25932 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25933 @var{cli-command} is any existing @value{GDBN} CLI command.
25935 @item @var{mi-command} @expansion{}
25936 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25937 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25939 @item @var{token} @expansion{}
25940 "any sequence of digits"
25942 @item @var{option} @expansion{}
25943 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25945 @item @var{parameter} @expansion{}
25946 @code{@var{non-blank-sequence} | @var{c-string}}
25948 @item @var{operation} @expansion{}
25949 @emph{any of the operations described in this chapter}
25951 @item @var{non-blank-sequence} @expansion{}
25952 @emph{anything, provided it doesn't contain special characters such as
25953 "-", @var{nl}, """ and of course " "}
25955 @item @var{c-string} @expansion{}
25956 @code{""" @var{seven-bit-iso-c-string-content} """}
25958 @item @var{nl} @expansion{}
25967 The CLI commands are still handled by the @sc{mi} interpreter; their
25968 output is described below.
25971 The @code{@var{token}}, when present, is passed back when the command
25975 Some @sc{mi} commands accept optional arguments as part of the parameter
25976 list. Each option is identified by a leading @samp{-} (dash) and may be
25977 followed by an optional argument parameter. Options occur first in the
25978 parameter list and can be delimited from normal parameters using
25979 @samp{--} (this is useful when some parameters begin with a dash).
25986 We want easy access to the existing CLI syntax (for debugging).
25989 We want it to be easy to spot a @sc{mi} operation.
25992 @node GDB/MI Output Syntax
25993 @subsection @sc{gdb/mi} Output Syntax
25995 @cindex output syntax of @sc{gdb/mi}
25996 @cindex @sc{gdb/mi}, output syntax
25997 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25998 followed, optionally, by a single result record. This result record
25999 is for the most recent command. The sequence of output records is
26000 terminated by @samp{(gdb)}.
26002 If an input command was prefixed with a @code{@var{token}} then the
26003 corresponding output for that command will also be prefixed by that same
26007 @item @var{output} @expansion{}
26008 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26010 @item @var{result-record} @expansion{}
26011 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26013 @item @var{out-of-band-record} @expansion{}
26014 @code{@var{async-record} | @var{stream-record}}
26016 @item @var{async-record} @expansion{}
26017 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26019 @item @var{exec-async-output} @expansion{}
26020 @code{[ @var{token} ] "*" @var{async-output}}
26022 @item @var{status-async-output} @expansion{}
26023 @code{[ @var{token} ] "+" @var{async-output}}
26025 @item @var{notify-async-output} @expansion{}
26026 @code{[ @var{token} ] "=" @var{async-output}}
26028 @item @var{async-output} @expansion{}
26029 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26031 @item @var{result-class} @expansion{}
26032 @code{"done" | "running" | "connected" | "error" | "exit"}
26034 @item @var{async-class} @expansion{}
26035 @code{"stopped" | @var{others}} (where @var{others} will be added
26036 depending on the needs---this is still in development).
26038 @item @var{result} @expansion{}
26039 @code{ @var{variable} "=" @var{value}}
26041 @item @var{variable} @expansion{}
26042 @code{ @var{string} }
26044 @item @var{value} @expansion{}
26045 @code{ @var{const} | @var{tuple} | @var{list} }
26047 @item @var{const} @expansion{}
26048 @code{@var{c-string}}
26050 @item @var{tuple} @expansion{}
26051 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26053 @item @var{list} @expansion{}
26054 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26055 @var{result} ( "," @var{result} )* "]" }
26057 @item @var{stream-record} @expansion{}
26058 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26060 @item @var{console-stream-output} @expansion{}
26061 @code{"~" @var{c-string}}
26063 @item @var{target-stream-output} @expansion{}
26064 @code{"@@" @var{c-string}}
26066 @item @var{log-stream-output} @expansion{}
26067 @code{"&" @var{c-string}}
26069 @item @var{nl} @expansion{}
26072 @item @var{token} @expansion{}
26073 @emph{any sequence of digits}.
26081 All output sequences end in a single line containing a period.
26084 The @code{@var{token}} is from the corresponding request. Note that
26085 for all async output, while the token is allowed by the grammar and
26086 may be output by future versions of @value{GDBN} for select async
26087 output messages, it is generally omitted. Frontends should treat
26088 all async output as reporting general changes in the state of the
26089 target and there should be no need to associate async output to any
26093 @cindex status output in @sc{gdb/mi}
26094 @var{status-async-output} contains on-going status information about the
26095 progress of a slow operation. It can be discarded. All status output is
26096 prefixed by @samp{+}.
26099 @cindex async output in @sc{gdb/mi}
26100 @var{exec-async-output} contains asynchronous state change on the target
26101 (stopped, started, disappeared). All async output is prefixed by
26105 @cindex notify output in @sc{gdb/mi}
26106 @var{notify-async-output} contains supplementary information that the
26107 client should handle (e.g., a new breakpoint information). All notify
26108 output is prefixed by @samp{=}.
26111 @cindex console output in @sc{gdb/mi}
26112 @var{console-stream-output} is output that should be displayed as is in the
26113 console. It is the textual response to a CLI command. All the console
26114 output is prefixed by @samp{~}.
26117 @cindex target output in @sc{gdb/mi}
26118 @var{target-stream-output} is the output produced by the target program.
26119 All the target output is prefixed by @samp{@@}.
26122 @cindex log output in @sc{gdb/mi}
26123 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26124 instance messages that should be displayed as part of an error log. All
26125 the log output is prefixed by @samp{&}.
26128 @cindex list output in @sc{gdb/mi}
26129 New @sc{gdb/mi} commands should only output @var{lists} containing
26135 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26136 details about the various output records.
26138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26139 @node GDB/MI Compatibility with CLI
26140 @section @sc{gdb/mi} Compatibility with CLI
26142 @cindex compatibility, @sc{gdb/mi} and CLI
26143 @cindex @sc{gdb/mi}, compatibility with CLI
26145 For the developers convenience CLI commands can be entered directly,
26146 but there may be some unexpected behaviour. For example, commands
26147 that query the user will behave as if the user replied yes, breakpoint
26148 command lists are not executed and some CLI commands, such as
26149 @code{if}, @code{when} and @code{define}, prompt for further input with
26150 @samp{>}, which is not valid MI output.
26152 This feature may be removed at some stage in the future and it is
26153 recommended that front ends use the @code{-interpreter-exec} command
26154 (@pxref{-interpreter-exec}).
26156 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26157 @node GDB/MI Development and Front Ends
26158 @section @sc{gdb/mi} Development and Front Ends
26159 @cindex @sc{gdb/mi} development
26161 The application which takes the MI output and presents the state of the
26162 program being debugged to the user is called a @dfn{front end}.
26164 Although @sc{gdb/mi} is still incomplete, it is currently being used
26165 by a variety of front ends to @value{GDBN}. This makes it difficult
26166 to introduce new functionality without breaking existing usage. This
26167 section tries to minimize the problems by describing how the protocol
26170 Some changes in MI need not break a carefully designed front end, and
26171 for these the MI version will remain unchanged. The following is a
26172 list of changes that may occur within one level, so front ends should
26173 parse MI output in a way that can handle them:
26177 New MI commands may be added.
26180 New fields may be added to the output of any MI command.
26183 The range of values for fields with specified values, e.g.,
26184 @code{in_scope} (@pxref{-var-update}) may be extended.
26186 @c The format of field's content e.g type prefix, may change so parse it
26187 @c at your own risk. Yes, in general?
26189 @c The order of fields may change? Shouldn't really matter but it might
26190 @c resolve inconsistencies.
26193 If the changes are likely to break front ends, the MI version level
26194 will be increased by one. This will allow the front end to parse the
26195 output according to the MI version. Apart from mi0, new versions of
26196 @value{GDBN} will not support old versions of MI and it will be the
26197 responsibility of the front end to work with the new one.
26199 @c Starting with mi3, add a new command -mi-version that prints the MI
26202 The best way to avoid unexpected changes in MI that might break your front
26203 end is to make your project known to @value{GDBN} developers and
26204 follow development on @email{gdb@@sourceware.org} and
26205 @email{gdb-patches@@sourceware.org}.
26206 @cindex mailing lists
26208 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26209 @node GDB/MI Output Records
26210 @section @sc{gdb/mi} Output Records
26213 * GDB/MI Result Records::
26214 * GDB/MI Stream Records::
26215 * GDB/MI Async Records::
26216 * GDB/MI Frame Information::
26217 * GDB/MI Thread Information::
26218 * GDB/MI Ada Exception Information::
26221 @node GDB/MI Result Records
26222 @subsection @sc{gdb/mi} Result Records
26224 @cindex result records in @sc{gdb/mi}
26225 @cindex @sc{gdb/mi}, result records
26226 In addition to a number of out-of-band notifications, the response to a
26227 @sc{gdb/mi} command includes one of the following result indications:
26231 @item "^done" [ "," @var{results} ]
26232 The synchronous operation was successful, @code{@var{results}} are the return
26237 This result record is equivalent to @samp{^done}. Historically, it
26238 was output instead of @samp{^done} if the command has resumed the
26239 target. This behaviour is maintained for backward compatibility, but
26240 all frontends should treat @samp{^done} and @samp{^running}
26241 identically and rely on the @samp{*running} output record to determine
26242 which threads are resumed.
26246 @value{GDBN} has connected to a remote target.
26248 @item "^error" "," @var{c-string}
26250 The operation failed. The @code{@var{c-string}} contains the corresponding
26255 @value{GDBN} has terminated.
26259 @node GDB/MI Stream Records
26260 @subsection @sc{gdb/mi} Stream Records
26262 @cindex @sc{gdb/mi}, stream records
26263 @cindex stream records in @sc{gdb/mi}
26264 @value{GDBN} internally maintains a number of output streams: the console, the
26265 target, and the log. The output intended for each of these streams is
26266 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26268 Each stream record begins with a unique @dfn{prefix character} which
26269 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26270 Syntax}). In addition to the prefix, each stream record contains a
26271 @code{@var{string-output}}. This is either raw text (with an implicit new
26272 line) or a quoted C string (which does not contain an implicit newline).
26275 @item "~" @var{string-output}
26276 The console output stream contains text that should be displayed in the
26277 CLI console window. It contains the textual responses to CLI commands.
26279 @item "@@" @var{string-output}
26280 The target output stream contains any textual output from the running
26281 target. This is only present when GDB's event loop is truly
26282 asynchronous, which is currently only the case for remote targets.
26284 @item "&" @var{string-output}
26285 The log stream contains debugging messages being produced by @value{GDBN}'s
26289 @node GDB/MI Async Records
26290 @subsection @sc{gdb/mi} Async Records
26292 @cindex async records in @sc{gdb/mi}
26293 @cindex @sc{gdb/mi}, async records
26294 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26295 additional changes that have occurred. Those changes can either be a
26296 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26297 target activity (e.g., target stopped).
26299 The following is the list of possible async records:
26303 @item *running,thread-id="@var{thread}"
26304 The target is now running. The @var{thread} field tells which
26305 specific thread is now running, and can be @samp{all} if all threads
26306 are running. The frontend should assume that no interaction with a
26307 running thread is possible after this notification is produced.
26308 The frontend should not assume that this notification is output
26309 only once for any command. @value{GDBN} may emit this notification
26310 several times, either for different threads, because it cannot resume
26311 all threads together, or even for a single thread, if the thread must
26312 be stepped though some code before letting it run freely.
26314 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26315 The target has stopped. The @var{reason} field can have one of the
26319 @item breakpoint-hit
26320 A breakpoint was reached.
26321 @item watchpoint-trigger
26322 A watchpoint was triggered.
26323 @item read-watchpoint-trigger
26324 A read watchpoint was triggered.
26325 @item access-watchpoint-trigger
26326 An access watchpoint was triggered.
26327 @item function-finished
26328 An -exec-finish or similar CLI command was accomplished.
26329 @item location-reached
26330 An -exec-until or similar CLI command was accomplished.
26331 @item watchpoint-scope
26332 A watchpoint has gone out of scope.
26333 @item end-stepping-range
26334 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26335 similar CLI command was accomplished.
26336 @item exited-signalled
26337 The inferior exited because of a signal.
26339 The inferior exited.
26340 @item exited-normally
26341 The inferior exited normally.
26342 @item signal-received
26343 A signal was received by the inferior.
26345 The inferior has stopped due to a library being loaded or unloaded.
26346 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26347 set or when a @code{catch load} or @code{catch unload} catchpoint is
26348 in use (@pxref{Set Catchpoints}).
26350 The inferior has forked. This is reported when @code{catch fork}
26351 (@pxref{Set Catchpoints}) has been used.
26353 The inferior has vforked. This is reported in when @code{catch vfork}
26354 (@pxref{Set Catchpoints}) has been used.
26355 @item syscall-entry
26356 The inferior entered a system call. This is reported when @code{catch
26357 syscall} (@pxref{Set Catchpoints}) has been used.
26358 @item syscall-entry
26359 The inferior returned from a system call. This is reported when
26360 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26362 The inferior called @code{exec}. This is reported when @code{catch exec}
26363 (@pxref{Set Catchpoints}) has been used.
26366 The @var{id} field identifies the thread that directly caused the stop
26367 -- for example by hitting a breakpoint. Depending on whether all-stop
26368 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26369 stop all threads, or only the thread that directly triggered the stop.
26370 If all threads are stopped, the @var{stopped} field will have the
26371 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26372 field will be a list of thread identifiers. Presently, this list will
26373 always include a single thread, but frontend should be prepared to see
26374 several threads in the list. The @var{core} field reports the
26375 processor core on which the stop event has happened. This field may be absent
26376 if such information is not available.
26378 @item =thread-group-added,id="@var{id}"
26379 @itemx =thread-group-removed,id="@var{id}"
26380 A thread group was either added or removed. The @var{id} field
26381 contains the @value{GDBN} identifier of the thread group. When a thread
26382 group is added, it generally might not be associated with a running
26383 process. When a thread group is removed, its id becomes invalid and
26384 cannot be used in any way.
26386 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26387 A thread group became associated with a running program,
26388 either because the program was just started or the thread group
26389 was attached to a program. The @var{id} field contains the
26390 @value{GDBN} identifier of the thread group. The @var{pid} field
26391 contains process identifier, specific to the operating system.
26393 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26394 A thread group is no longer associated with a running program,
26395 either because the program has exited, or because it was detached
26396 from. The @var{id} field contains the @value{GDBN} identifier of the
26397 thread group. @var{code} is the exit code of the inferior; it exists
26398 only when the inferior exited with some code.
26400 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26401 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26402 A thread either was created, or has exited. The @var{id} field
26403 contains the @value{GDBN} identifier of the thread. The @var{gid}
26404 field identifies the thread group this thread belongs to.
26406 @item =thread-selected,id="@var{id}"
26407 Informs that the selected thread was changed as result of the last
26408 command. This notification is not emitted as result of @code{-thread-select}
26409 command but is emitted whenever an MI command that is not documented
26410 to change the selected thread actually changes it. In particular,
26411 invoking, directly or indirectly (via user-defined command), the CLI
26412 @code{thread} command, will generate this notification.
26414 We suggest that in response to this notification, front ends
26415 highlight the selected thread and cause subsequent commands to apply to
26418 @item =library-loaded,...
26419 Reports that a new library file was loaded by the program. This
26420 notification has 4 fields---@var{id}, @var{target-name},
26421 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26422 opaque identifier of the library. For remote debugging case,
26423 @var{target-name} and @var{host-name} fields give the name of the
26424 library file on the target, and on the host respectively. For native
26425 debugging, both those fields have the same value. The
26426 @var{symbols-loaded} field is emitted only for backward compatibility
26427 and should not be relied on to convey any useful information. The
26428 @var{thread-group} field, if present, specifies the id of the thread
26429 group in whose context the library was loaded. If the field is
26430 absent, it means the library was loaded in the context of all present
26433 @item =library-unloaded,...
26434 Reports that a library was unloaded by the program. This notification
26435 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26436 the same meaning as for the @code{=library-loaded} notification.
26437 The @var{thread-group} field, if present, specifies the id of the
26438 thread group in whose context the library was unloaded. If the field is
26439 absent, it means the library was unloaded in the context of all present
26442 @item =breakpoint-created,bkpt=@{...@}
26443 @itemx =breakpoint-modified,bkpt=@{...@}
26444 @itemx =breakpoint-deleted,bkpt=@{...@}
26445 Reports that a breakpoint was created, modified, or deleted,
26446 respectively. Only user-visible breakpoints are reported to the MI
26449 The @var{bkpt} argument is of the same form as returned by the various
26450 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26452 Note that if a breakpoint is emitted in the result record of a
26453 command, then it will not also be emitted in an async record.
26457 @node GDB/MI Frame Information
26458 @subsection @sc{gdb/mi} Frame Information
26460 Response from many MI commands includes an information about stack
26461 frame. This information is a tuple that may have the following
26466 The level of the stack frame. The innermost frame has the level of
26467 zero. This field is always present.
26470 The name of the function corresponding to the frame. This field may
26471 be absent if @value{GDBN} is unable to determine the function name.
26474 The code address for the frame. This field is always present.
26477 The name of the source files that correspond to the frame's code
26478 address. This field may be absent.
26481 The source line corresponding to the frames' code address. This field
26485 The name of the binary file (either executable or shared library) the
26486 corresponds to the frame's code address. This field may be absent.
26490 @node GDB/MI Thread Information
26491 @subsection @sc{gdb/mi} Thread Information
26493 Whenever @value{GDBN} has to report an information about a thread, it
26494 uses a tuple with the following fields:
26498 The numeric id assigned to the thread by @value{GDBN}. This field is
26502 Target-specific string identifying the thread. This field is always present.
26505 Additional information about the thread provided by the target.
26506 It is supposed to be human-readable and not interpreted by the
26507 frontend. This field is optional.
26510 Either @samp{stopped} or @samp{running}, depending on whether the
26511 thread is presently running. This field is always present.
26514 The value of this field is an integer number of the processor core the
26515 thread was last seen on. This field is optional.
26518 @node GDB/MI Ada Exception Information
26519 @subsection @sc{gdb/mi} Ada Exception Information
26521 Whenever a @code{*stopped} record is emitted because the program
26522 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26523 @value{GDBN} provides the name of the exception that was raised via
26524 the @code{exception-name} field.
26526 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26527 @node GDB/MI Simple Examples
26528 @section Simple Examples of @sc{gdb/mi} Interaction
26529 @cindex @sc{gdb/mi}, simple examples
26531 This subsection presents several simple examples of interaction using
26532 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26533 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26534 the output received from @sc{gdb/mi}.
26536 Note the line breaks shown in the examples are here only for
26537 readability, they don't appear in the real output.
26539 @subheading Setting a Breakpoint
26541 Setting a breakpoint generates synchronous output which contains detailed
26542 information of the breakpoint.
26545 -> -break-insert main
26546 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26547 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26548 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26552 @subheading Program Execution
26554 Program execution generates asynchronous records and MI gives the
26555 reason that execution stopped.
26561 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26562 frame=@{addr="0x08048564",func="main",
26563 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26564 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26569 <- *stopped,reason="exited-normally"
26573 @subheading Quitting @value{GDBN}
26575 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26583 Please note that @samp{^exit} is printed immediately, but it might
26584 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26585 performs necessary cleanups, including killing programs being debugged
26586 or disconnecting from debug hardware, so the frontend should wait till
26587 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26588 fails to exit in reasonable time.
26590 @subheading A Bad Command
26592 Here's what happens if you pass a non-existent command:
26596 <- ^error,msg="Undefined MI command: rubbish"
26601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26602 @node GDB/MI Command Description Format
26603 @section @sc{gdb/mi} Command Description Format
26605 The remaining sections describe blocks of commands. Each block of
26606 commands is laid out in a fashion similar to this section.
26608 @subheading Motivation
26610 The motivation for this collection of commands.
26612 @subheading Introduction
26614 A brief introduction to this collection of commands as a whole.
26616 @subheading Commands
26618 For each command in the block, the following is described:
26620 @subsubheading Synopsis
26623 -command @var{args}@dots{}
26626 @subsubheading Result
26628 @subsubheading @value{GDBN} Command
26630 The corresponding @value{GDBN} CLI command(s), if any.
26632 @subsubheading Example
26634 Example(s) formatted for readability. Some of the described commands have
26635 not been implemented yet and these are labeled N.A.@: (not available).
26638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26639 @node GDB/MI Breakpoint Commands
26640 @section @sc{gdb/mi} Breakpoint Commands
26642 @cindex breakpoint commands for @sc{gdb/mi}
26643 @cindex @sc{gdb/mi}, breakpoint commands
26644 This section documents @sc{gdb/mi} commands for manipulating
26647 @subheading The @code{-break-after} Command
26648 @findex -break-after
26650 @subsubheading Synopsis
26653 -break-after @var{number} @var{count}
26656 The breakpoint number @var{number} is not in effect until it has been
26657 hit @var{count} times. To see how this is reflected in the output of
26658 the @samp{-break-list} command, see the description of the
26659 @samp{-break-list} command below.
26661 @subsubheading @value{GDBN} Command
26663 The corresponding @value{GDBN} command is @samp{ignore}.
26665 @subsubheading Example
26670 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26671 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26672 fullname="/home/foo/hello.c",line="5",times="0"@}
26679 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26680 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26681 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26682 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26683 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26684 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26685 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26686 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26687 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26688 line="5",times="0",ignore="3"@}]@}
26693 @subheading The @code{-break-catch} Command
26694 @findex -break-catch
26697 @subheading The @code{-break-commands} Command
26698 @findex -break-commands
26700 @subsubheading Synopsis
26703 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26706 Specifies the CLI commands that should be executed when breakpoint
26707 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26708 are the commands. If no command is specified, any previously-set
26709 commands are cleared. @xref{Break Commands}. Typical use of this
26710 functionality is tracing a program, that is, printing of values of
26711 some variables whenever breakpoint is hit and then continuing.
26713 @subsubheading @value{GDBN} Command
26715 The corresponding @value{GDBN} command is @samp{commands}.
26717 @subsubheading Example
26722 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26723 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26724 fullname="/home/foo/hello.c",line="5",times="0"@}
26726 -break-commands 1 "print v" "continue"
26731 @subheading The @code{-break-condition} Command
26732 @findex -break-condition
26734 @subsubheading Synopsis
26737 -break-condition @var{number} @var{expr}
26740 Breakpoint @var{number} will stop the program only if the condition in
26741 @var{expr} is true. The condition becomes part of the
26742 @samp{-break-list} output (see the description of the @samp{-break-list}
26745 @subsubheading @value{GDBN} Command
26747 The corresponding @value{GDBN} command is @samp{condition}.
26749 @subsubheading Example
26753 -break-condition 1 1
26757 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26758 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26759 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26760 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26761 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26762 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26763 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26764 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26765 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26766 line="5",cond="1",times="0",ignore="3"@}]@}
26770 @subheading The @code{-break-delete} Command
26771 @findex -break-delete
26773 @subsubheading Synopsis
26776 -break-delete ( @var{breakpoint} )+
26779 Delete the breakpoint(s) whose number(s) are specified in the argument
26780 list. This is obviously reflected in the breakpoint list.
26782 @subsubheading @value{GDBN} Command
26784 The corresponding @value{GDBN} command is @samp{delete}.
26786 @subsubheading Example
26794 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26795 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26796 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26797 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26798 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26799 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26800 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26805 @subheading The @code{-break-disable} Command
26806 @findex -break-disable
26808 @subsubheading Synopsis
26811 -break-disable ( @var{breakpoint} )+
26814 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26815 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26817 @subsubheading @value{GDBN} Command
26819 The corresponding @value{GDBN} command is @samp{disable}.
26821 @subsubheading Example
26829 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26830 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26831 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26832 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26833 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26834 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26835 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26836 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26837 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26838 line="5",times="0"@}]@}
26842 @subheading The @code{-break-enable} Command
26843 @findex -break-enable
26845 @subsubheading Synopsis
26848 -break-enable ( @var{breakpoint} )+
26851 Enable (previously disabled) @var{breakpoint}(s).
26853 @subsubheading @value{GDBN} Command
26855 The corresponding @value{GDBN} command is @samp{enable}.
26857 @subsubheading Example
26865 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26866 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26867 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26868 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26869 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26870 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26871 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26872 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26873 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26874 line="5",times="0"@}]@}
26878 @subheading The @code{-break-info} Command
26879 @findex -break-info
26881 @subsubheading Synopsis
26884 -break-info @var{breakpoint}
26888 Get information about a single breakpoint.
26890 @subsubheading @value{GDBN} Command
26892 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26894 @subsubheading Example
26897 @subheading The @code{-break-insert} Command
26898 @findex -break-insert
26900 @subsubheading Synopsis
26903 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26904 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26905 [ -p @var{thread} ] [ @var{location} ]
26909 If specified, @var{location}, can be one of:
26916 @item filename:linenum
26917 @item filename:function
26921 The possible optional parameters of this command are:
26925 Insert a temporary breakpoint.
26927 Insert a hardware breakpoint.
26928 @item -c @var{condition}
26929 Make the breakpoint conditional on @var{condition}.
26930 @item -i @var{ignore-count}
26931 Initialize the @var{ignore-count}.
26933 If @var{location} cannot be parsed (for example if it
26934 refers to unknown files or functions), create a pending
26935 breakpoint. Without this flag, @value{GDBN} will report
26936 an error, and won't create a breakpoint, if @var{location}
26939 Create a disabled breakpoint.
26941 Create a tracepoint. @xref{Tracepoints}. When this parameter
26942 is used together with @samp{-h}, a fast tracepoint is created.
26945 @subsubheading Result
26947 The result is in the form:
26950 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26951 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26952 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26953 times="@var{times}"@}
26957 where @var{number} is the @value{GDBN} number for this breakpoint,
26958 @var{funcname} is the name of the function where the breakpoint was
26959 inserted, @var{filename} is the name of the source file which contains
26960 this function, @var{lineno} is the source line number within that file
26961 and @var{times} the number of times that the breakpoint has been hit
26962 (always 0 for -break-insert but may be greater for -break-info or -break-list
26963 which use the same output).
26965 Note: this format is open to change.
26966 @c An out-of-band breakpoint instead of part of the result?
26968 @subsubheading @value{GDBN} Command
26970 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26971 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26973 @subsubheading Example
26978 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26979 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26981 -break-insert -t foo
26982 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26983 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26986 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26987 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26988 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26989 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26990 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26991 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26992 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26993 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26994 addr="0x0001072c", func="main",file="recursive2.c",
26995 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26996 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26997 addr="0x00010774",func="foo",file="recursive2.c",
26998 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27000 -break-insert -r foo.*
27001 ~int foo(int, int);
27002 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27003 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27007 @subheading The @code{-break-list} Command
27008 @findex -break-list
27010 @subsubheading Synopsis
27016 Displays the list of inserted breakpoints, showing the following fields:
27020 number of the breakpoint
27022 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27024 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27027 is the breakpoint enabled or no: @samp{y} or @samp{n}
27029 memory location at which the breakpoint is set
27031 logical location of the breakpoint, expressed by function name, file
27034 number of times the breakpoint has been hit
27037 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27038 @code{body} field is an empty list.
27040 @subsubheading @value{GDBN} Command
27042 The corresponding @value{GDBN} command is @samp{info break}.
27044 @subsubheading Example
27049 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27050 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27051 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27052 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27053 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27054 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27055 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27056 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27057 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27058 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27059 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27060 line="13",times="0"@}]@}
27064 Here's an example of the result when there are no breakpoints:
27069 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27070 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27071 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27072 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27073 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27074 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27075 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27080 @subheading The @code{-break-passcount} Command
27081 @findex -break-passcount
27083 @subsubheading Synopsis
27086 -break-passcount @var{tracepoint-number} @var{passcount}
27089 Set the passcount for tracepoint @var{tracepoint-number} to
27090 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27091 is not a tracepoint, error is emitted. This corresponds to CLI
27092 command @samp{passcount}.
27094 @subheading The @code{-break-watch} Command
27095 @findex -break-watch
27097 @subsubheading Synopsis
27100 -break-watch [ -a | -r ]
27103 Create a watchpoint. With the @samp{-a} option it will create an
27104 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27105 read from or on a write to the memory location. With the @samp{-r}
27106 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27107 trigger only when the memory location is accessed for reading. Without
27108 either of the options, the watchpoint created is a regular watchpoint,
27109 i.e., it will trigger when the memory location is accessed for writing.
27110 @xref{Set Watchpoints, , Setting Watchpoints}.
27112 Note that @samp{-break-list} will report a single list of watchpoints and
27113 breakpoints inserted.
27115 @subsubheading @value{GDBN} Command
27117 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27120 @subsubheading Example
27122 Setting a watchpoint on a variable in the @code{main} function:
27127 ^done,wpt=@{number="2",exp="x"@}
27132 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27133 value=@{old="-268439212",new="55"@},
27134 frame=@{func="main",args=[],file="recursive2.c",
27135 fullname="/home/foo/bar/recursive2.c",line="5"@}
27139 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27140 the program execution twice: first for the variable changing value, then
27141 for the watchpoint going out of scope.
27146 ^done,wpt=@{number="5",exp="C"@}
27151 *stopped,reason="watchpoint-trigger",
27152 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27153 frame=@{func="callee4",args=[],
27154 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27155 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27160 *stopped,reason="watchpoint-scope",wpnum="5",
27161 frame=@{func="callee3",args=[@{name="strarg",
27162 value="0x11940 \"A string argument.\""@}],
27163 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27164 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27168 Listing breakpoints and watchpoints, at different points in the program
27169 execution. Note that once the watchpoint goes out of scope, it is
27175 ^done,wpt=@{number="2",exp="C"@}
27178 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27179 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27180 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27181 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27182 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27183 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27184 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27185 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27186 addr="0x00010734",func="callee4",
27187 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27188 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27189 bkpt=@{number="2",type="watchpoint",disp="keep",
27190 enabled="y",addr="",what="C",times="0"@}]@}
27195 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27196 value=@{old="-276895068",new="3"@},
27197 frame=@{func="callee4",args=[],
27198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27199 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27202 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27203 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27204 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27205 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27206 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27207 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27208 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27209 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27210 addr="0x00010734",func="callee4",
27211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27212 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27213 bkpt=@{number="2",type="watchpoint",disp="keep",
27214 enabled="y",addr="",what="C",times="-5"@}]@}
27218 ^done,reason="watchpoint-scope",wpnum="2",
27219 frame=@{func="callee3",args=[@{name="strarg",
27220 value="0x11940 \"A string argument.\""@}],
27221 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27222 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27225 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27226 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27227 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27228 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27229 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27230 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27231 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27232 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27233 addr="0x00010734",func="callee4",
27234 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27235 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27241 @node GDB/MI Program Context
27242 @section @sc{gdb/mi} Program Context
27244 @subheading The @code{-exec-arguments} Command
27245 @findex -exec-arguments
27248 @subsubheading Synopsis
27251 -exec-arguments @var{args}
27254 Set the inferior program arguments, to be used in the next
27257 @subsubheading @value{GDBN} Command
27259 The corresponding @value{GDBN} command is @samp{set args}.
27261 @subsubheading Example
27265 -exec-arguments -v word
27272 @subheading The @code{-exec-show-arguments} Command
27273 @findex -exec-show-arguments
27275 @subsubheading Synopsis
27278 -exec-show-arguments
27281 Print the arguments of the program.
27283 @subsubheading @value{GDBN} Command
27285 The corresponding @value{GDBN} command is @samp{show args}.
27287 @subsubheading Example
27292 @subheading The @code{-environment-cd} Command
27293 @findex -environment-cd
27295 @subsubheading Synopsis
27298 -environment-cd @var{pathdir}
27301 Set @value{GDBN}'s working directory.
27303 @subsubheading @value{GDBN} Command
27305 The corresponding @value{GDBN} command is @samp{cd}.
27307 @subsubheading Example
27311 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27317 @subheading The @code{-environment-directory} Command
27318 @findex -environment-directory
27320 @subsubheading Synopsis
27323 -environment-directory [ -r ] [ @var{pathdir} ]+
27326 Add directories @var{pathdir} to beginning of search path for source files.
27327 If the @samp{-r} option is used, the search path is reset to the default
27328 search path. If directories @var{pathdir} are supplied in addition to the
27329 @samp{-r} option, the search path is first reset and then addition
27331 Multiple directories may be specified, separated by blanks. Specifying
27332 multiple directories in a single command
27333 results in the directories added to the beginning of the
27334 search path in the same order they were presented in the command.
27335 If blanks are needed as
27336 part of a directory name, double-quotes should be used around
27337 the name. In the command output, the path will show up separated
27338 by the system directory-separator character. The directory-separator
27339 character must not be used
27340 in any directory name.
27341 If no directories are specified, the current search path is displayed.
27343 @subsubheading @value{GDBN} Command
27345 The corresponding @value{GDBN} command is @samp{dir}.
27347 @subsubheading Example
27351 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27352 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27354 -environment-directory ""
27355 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27357 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27358 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27360 -environment-directory -r
27361 ^done,source-path="$cdir:$cwd"
27366 @subheading The @code{-environment-path} Command
27367 @findex -environment-path
27369 @subsubheading Synopsis
27372 -environment-path [ -r ] [ @var{pathdir} ]+
27375 Add directories @var{pathdir} to beginning of search path for object files.
27376 If the @samp{-r} option is used, the search path is reset to the original
27377 search path that existed at gdb start-up. If directories @var{pathdir} are
27378 supplied in addition to the
27379 @samp{-r} option, the search path is first reset and then addition
27381 Multiple directories may be specified, separated by blanks. Specifying
27382 multiple directories in a single command
27383 results in the directories added to the beginning of the
27384 search path in the same order they were presented in the command.
27385 If blanks are needed as
27386 part of a directory name, double-quotes should be used around
27387 the name. In the command output, the path will show up separated
27388 by the system directory-separator character. The directory-separator
27389 character must not be used
27390 in any directory name.
27391 If no directories are specified, the current path is displayed.
27394 @subsubheading @value{GDBN} Command
27396 The corresponding @value{GDBN} command is @samp{path}.
27398 @subsubheading Example
27403 ^done,path="/usr/bin"
27405 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27406 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27408 -environment-path -r /usr/local/bin
27409 ^done,path="/usr/local/bin:/usr/bin"
27414 @subheading The @code{-environment-pwd} Command
27415 @findex -environment-pwd
27417 @subsubheading Synopsis
27423 Show the current working directory.
27425 @subsubheading @value{GDBN} Command
27427 The corresponding @value{GDBN} command is @samp{pwd}.
27429 @subsubheading Example
27434 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27438 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27439 @node GDB/MI Thread Commands
27440 @section @sc{gdb/mi} Thread Commands
27443 @subheading The @code{-thread-info} Command
27444 @findex -thread-info
27446 @subsubheading Synopsis
27449 -thread-info [ @var{thread-id} ]
27452 Reports information about either a specific thread, if
27453 the @var{thread-id} parameter is present, or about all
27454 threads. When printing information about all threads,
27455 also reports the current thread.
27457 @subsubheading @value{GDBN} Command
27459 The @samp{info thread} command prints the same information
27462 @subsubheading Result
27464 The result is a list of threads. The following attributes are
27465 defined for a given thread:
27469 This field exists only for the current thread. It has the value @samp{*}.
27472 The identifier that @value{GDBN} uses to refer to the thread.
27475 The identifier that the target uses to refer to the thread.
27478 Extra information about the thread, in a target-specific format. This
27482 The name of the thread. If the user specified a name using the
27483 @code{thread name} command, then this name is given. Otherwise, if
27484 @value{GDBN} can extract the thread name from the target, then that
27485 name is given. If @value{GDBN} cannot find the thread name, then this
27489 The stack frame currently executing in the thread.
27492 The thread's state. The @samp{state} field may have the following
27497 The thread is stopped. Frame information is available for stopped
27501 The thread is running. There's no frame information for running
27507 If @value{GDBN} can find the CPU core on which this thread is running,
27508 then this field is the core identifier. This field is optional.
27512 @subsubheading Example
27517 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27518 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27519 args=[]@},state="running"@},
27520 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27521 frame=@{level="0",addr="0x0804891f",func="foo",
27522 args=[@{name="i",value="10"@}],
27523 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27524 state="running"@}],
27525 current-thread-id="1"
27529 @subheading The @code{-thread-list-ids} Command
27530 @findex -thread-list-ids
27532 @subsubheading Synopsis
27538 Produces a list of the currently known @value{GDBN} thread ids. At the
27539 end of the list it also prints the total number of such threads.
27541 This command is retained for historical reasons, the
27542 @code{-thread-info} command should be used instead.
27544 @subsubheading @value{GDBN} Command
27546 Part of @samp{info threads} supplies the same information.
27548 @subsubheading Example
27553 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27554 current-thread-id="1",number-of-threads="3"
27559 @subheading The @code{-thread-select} Command
27560 @findex -thread-select
27562 @subsubheading Synopsis
27565 -thread-select @var{threadnum}
27568 Make @var{threadnum} the current thread. It prints the number of the new
27569 current thread, and the topmost frame for that thread.
27571 This command is deprecated in favor of explicitly using the
27572 @samp{--thread} option to each command.
27574 @subsubheading @value{GDBN} Command
27576 The corresponding @value{GDBN} command is @samp{thread}.
27578 @subsubheading Example
27585 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27586 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27590 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27591 number-of-threads="3"
27594 ^done,new-thread-id="3",
27595 frame=@{level="0",func="vprintf",
27596 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27597 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27602 @node GDB/MI Ada Tasking Commands
27603 @section @sc{gdb/mi} Ada Tasking Commands
27605 @subheading The @code{-ada-task-info} Command
27606 @findex -ada-task-info
27608 @subsubheading Synopsis
27611 -ada-task-info [ @var{task-id} ]
27614 Reports information about either a specific Ada task, if the
27615 @var{task-id} parameter is present, or about all Ada tasks.
27617 @subsubheading @value{GDBN} Command
27619 The @samp{info tasks} command prints the same information
27620 about all Ada tasks (@pxref{Ada Tasks}).
27622 @subsubheading Result
27624 The result is a table of Ada tasks. The following columns are
27625 defined for each Ada task:
27629 This field exists only for the current thread. It has the value @samp{*}.
27632 The identifier that @value{GDBN} uses to refer to the Ada task.
27635 The identifier that the target uses to refer to the Ada task.
27638 The identifier of the thread corresponding to the Ada task.
27640 This field should always exist, as Ada tasks are always implemented
27641 on top of a thread. But if @value{GDBN} cannot find this corresponding
27642 thread for any reason, the field is omitted.
27645 This field exists only when the task was created by another task.
27646 In this case, it provides the ID of the parent task.
27649 The base priority of the task.
27652 The current state of the task. For a detailed description of the
27653 possible states, see @ref{Ada Tasks}.
27656 The name of the task.
27660 @subsubheading Example
27664 ^done,tasks=@{nr_rows="3",nr_cols="8",
27665 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27666 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27667 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27668 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27669 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27670 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27671 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27672 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27673 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27674 state="Child Termination Wait",name="main_task"@}]@}
27678 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27679 @node GDB/MI Program Execution
27680 @section @sc{gdb/mi} Program Execution
27682 These are the asynchronous commands which generate the out-of-band
27683 record @samp{*stopped}. Currently @value{GDBN} only really executes
27684 asynchronously with remote targets and this interaction is mimicked in
27687 @subheading The @code{-exec-continue} Command
27688 @findex -exec-continue
27690 @subsubheading Synopsis
27693 -exec-continue [--reverse] [--all|--thread-group N]
27696 Resumes the execution of the inferior program, which will continue
27697 to execute until it reaches a debugger stop event. If the
27698 @samp{--reverse} option is specified, execution resumes in reverse until
27699 it reaches a stop event. Stop events may include
27702 breakpoints or watchpoints
27704 signals or exceptions
27706 the end of the process (or its beginning under @samp{--reverse})
27708 the end or beginning of a replay log if one is being used.
27710 In all-stop mode (@pxref{All-Stop
27711 Mode}), may resume only one thread, or all threads, depending on the
27712 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27713 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27714 ignored in all-stop mode. If the @samp{--thread-group} options is
27715 specified, then all threads in that thread group are resumed.
27717 @subsubheading @value{GDBN} Command
27719 The corresponding @value{GDBN} corresponding is @samp{continue}.
27721 @subsubheading Example
27728 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27729 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27735 @subheading The @code{-exec-finish} Command
27736 @findex -exec-finish
27738 @subsubheading Synopsis
27741 -exec-finish [--reverse]
27744 Resumes the execution of the inferior program until the current
27745 function is exited. Displays the results returned by the function.
27746 If the @samp{--reverse} option is specified, resumes the reverse
27747 execution of the inferior program until the point where current
27748 function was called.
27750 @subsubheading @value{GDBN} Command
27752 The corresponding @value{GDBN} command is @samp{finish}.
27754 @subsubheading Example
27756 Function returning @code{void}.
27763 *stopped,reason="function-finished",frame=@{func="main",args=[],
27764 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27768 Function returning other than @code{void}. The name of the internal
27769 @value{GDBN} variable storing the result is printed, together with the
27776 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27777 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27778 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27779 gdb-result-var="$1",return-value="0"
27784 @subheading The @code{-exec-interrupt} Command
27785 @findex -exec-interrupt
27787 @subsubheading Synopsis
27790 -exec-interrupt [--all|--thread-group N]
27793 Interrupts the background execution of the target. Note how the token
27794 associated with the stop message is the one for the execution command
27795 that has been interrupted. The token for the interrupt itself only
27796 appears in the @samp{^done} output. If the user is trying to
27797 interrupt a non-running program, an error message will be printed.
27799 Note that when asynchronous execution is enabled, this command is
27800 asynchronous just like other execution commands. That is, first the
27801 @samp{^done} response will be printed, and the target stop will be
27802 reported after that using the @samp{*stopped} notification.
27804 In non-stop mode, only the context thread is interrupted by default.
27805 All threads (in all inferiors) will be interrupted if the
27806 @samp{--all} option is specified. If the @samp{--thread-group}
27807 option is specified, all threads in that group will be interrupted.
27809 @subsubheading @value{GDBN} Command
27811 The corresponding @value{GDBN} command is @samp{interrupt}.
27813 @subsubheading Example
27824 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27825 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27826 fullname="/home/foo/bar/try.c",line="13"@}
27831 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27835 @subheading The @code{-exec-jump} Command
27838 @subsubheading Synopsis
27841 -exec-jump @var{location}
27844 Resumes execution of the inferior program at the location specified by
27845 parameter. @xref{Specify Location}, for a description of the
27846 different forms of @var{location}.
27848 @subsubheading @value{GDBN} Command
27850 The corresponding @value{GDBN} command is @samp{jump}.
27852 @subsubheading Example
27855 -exec-jump foo.c:10
27856 *running,thread-id="all"
27861 @subheading The @code{-exec-next} Command
27864 @subsubheading Synopsis
27867 -exec-next [--reverse]
27870 Resumes execution of the inferior program, stopping when the beginning
27871 of the next source line is reached.
27873 If the @samp{--reverse} option is specified, resumes reverse execution
27874 of the inferior program, stopping at the beginning of the previous
27875 source line. If you issue this command on the first line of a
27876 function, it will take you back to the caller of that function, to the
27877 source line where the function was called.
27880 @subsubheading @value{GDBN} Command
27882 The corresponding @value{GDBN} command is @samp{next}.
27884 @subsubheading Example
27890 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27895 @subheading The @code{-exec-next-instruction} Command
27896 @findex -exec-next-instruction
27898 @subsubheading Synopsis
27901 -exec-next-instruction [--reverse]
27904 Executes one machine instruction. If the instruction is a function
27905 call, continues until the function returns. If the program stops at an
27906 instruction in the middle of a source line, the address will be
27909 If the @samp{--reverse} option is specified, resumes reverse execution
27910 of the inferior program, stopping at the previous instruction. If the
27911 previously executed instruction was a return from another function,
27912 it will continue to execute in reverse until the call to that function
27913 (from the current stack frame) is reached.
27915 @subsubheading @value{GDBN} Command
27917 The corresponding @value{GDBN} command is @samp{nexti}.
27919 @subsubheading Example
27923 -exec-next-instruction
27927 *stopped,reason="end-stepping-range",
27928 addr="0x000100d4",line="5",file="hello.c"
27933 @subheading The @code{-exec-return} Command
27934 @findex -exec-return
27936 @subsubheading Synopsis
27942 Makes current function return immediately. Doesn't execute the inferior.
27943 Displays the new current frame.
27945 @subsubheading @value{GDBN} Command
27947 The corresponding @value{GDBN} command is @samp{return}.
27949 @subsubheading Example
27953 200-break-insert callee4
27954 200^done,bkpt=@{number="1",addr="0x00010734",
27955 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27960 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27961 frame=@{func="callee4",args=[],
27962 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27963 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27969 111^done,frame=@{level="0",func="callee3",
27970 args=[@{name="strarg",
27971 value="0x11940 \"A string argument.\""@}],
27972 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27973 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27978 @subheading The @code{-exec-run} Command
27981 @subsubheading Synopsis
27984 -exec-run [--all | --thread-group N]
27987 Starts execution of the inferior from the beginning. The inferior
27988 executes until either a breakpoint is encountered or the program
27989 exits. In the latter case the output will include an exit code, if
27990 the program has exited exceptionally.
27992 When no option is specified, the current inferior is started. If the
27993 @samp{--thread-group} option is specified, it should refer to a thread
27994 group of type @samp{process}, and that thread group will be started.
27995 If the @samp{--all} option is specified, then all inferiors will be started.
27997 @subsubheading @value{GDBN} Command
27999 The corresponding @value{GDBN} command is @samp{run}.
28001 @subsubheading Examples
28006 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28011 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28012 frame=@{func="main",args=[],file="recursive2.c",
28013 fullname="/home/foo/bar/recursive2.c",line="4"@}
28018 Program exited normally:
28026 *stopped,reason="exited-normally"
28031 Program exited exceptionally:
28039 *stopped,reason="exited",exit-code="01"
28043 Another way the program can terminate is if it receives a signal such as
28044 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28048 *stopped,reason="exited-signalled",signal-name="SIGINT",
28049 signal-meaning="Interrupt"
28053 @c @subheading -exec-signal
28056 @subheading The @code{-exec-step} Command
28059 @subsubheading Synopsis
28062 -exec-step [--reverse]
28065 Resumes execution of the inferior program, stopping when the beginning
28066 of the next source line is reached, if the next source line is not a
28067 function call. If it is, stop at the first instruction of the called
28068 function. If the @samp{--reverse} option is specified, resumes reverse
28069 execution of the inferior program, stopping at the beginning of the
28070 previously executed source line.
28072 @subsubheading @value{GDBN} Command
28074 The corresponding @value{GDBN} command is @samp{step}.
28076 @subsubheading Example
28078 Stepping into a function:
28084 *stopped,reason="end-stepping-range",
28085 frame=@{func="foo",args=[@{name="a",value="10"@},
28086 @{name="b",value="0"@}],file="recursive2.c",
28087 fullname="/home/foo/bar/recursive2.c",line="11"@}
28097 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28102 @subheading The @code{-exec-step-instruction} Command
28103 @findex -exec-step-instruction
28105 @subsubheading Synopsis
28108 -exec-step-instruction [--reverse]
28111 Resumes the inferior which executes one machine instruction. If the
28112 @samp{--reverse} option is specified, resumes reverse execution of the
28113 inferior program, stopping at the previously executed instruction.
28114 The output, once @value{GDBN} has stopped, will vary depending on
28115 whether we have stopped in the middle of a source line or not. In the
28116 former case, the address at which the program stopped will be printed
28119 @subsubheading @value{GDBN} Command
28121 The corresponding @value{GDBN} command is @samp{stepi}.
28123 @subsubheading Example
28127 -exec-step-instruction
28131 *stopped,reason="end-stepping-range",
28132 frame=@{func="foo",args=[],file="try.c",
28133 fullname="/home/foo/bar/try.c",line="10"@}
28135 -exec-step-instruction
28139 *stopped,reason="end-stepping-range",
28140 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28141 fullname="/home/foo/bar/try.c",line="10"@}
28146 @subheading The @code{-exec-until} Command
28147 @findex -exec-until
28149 @subsubheading Synopsis
28152 -exec-until [ @var{location} ]
28155 Executes the inferior until the @var{location} specified in the
28156 argument is reached. If there is no argument, the inferior executes
28157 until a source line greater than the current one is reached. The
28158 reason for stopping in this case will be @samp{location-reached}.
28160 @subsubheading @value{GDBN} Command
28162 The corresponding @value{GDBN} command is @samp{until}.
28164 @subsubheading Example
28168 -exec-until recursive2.c:6
28172 *stopped,reason="location-reached",frame=@{func="main",args=[],
28173 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28178 @subheading -file-clear
28179 Is this going away????
28182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28183 @node GDB/MI Stack Manipulation
28184 @section @sc{gdb/mi} Stack Manipulation Commands
28187 @subheading The @code{-stack-info-frame} Command
28188 @findex -stack-info-frame
28190 @subsubheading Synopsis
28196 Get info on the selected frame.
28198 @subsubheading @value{GDBN} Command
28200 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28201 (without arguments).
28203 @subsubheading Example
28208 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28210 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28214 @subheading The @code{-stack-info-depth} Command
28215 @findex -stack-info-depth
28217 @subsubheading Synopsis
28220 -stack-info-depth [ @var{max-depth} ]
28223 Return the depth of the stack. If the integer argument @var{max-depth}
28224 is specified, do not count beyond @var{max-depth} frames.
28226 @subsubheading @value{GDBN} Command
28228 There's no equivalent @value{GDBN} command.
28230 @subsubheading Example
28232 For a stack with frame levels 0 through 11:
28239 -stack-info-depth 4
28242 -stack-info-depth 12
28245 -stack-info-depth 11
28248 -stack-info-depth 13
28253 @subheading The @code{-stack-list-arguments} Command
28254 @findex -stack-list-arguments
28256 @subsubheading Synopsis
28259 -stack-list-arguments @var{print-values}
28260 [ @var{low-frame} @var{high-frame} ]
28263 Display a list of the arguments for the frames between @var{low-frame}
28264 and @var{high-frame} (inclusive). If @var{low-frame} and
28265 @var{high-frame} are not provided, list the arguments for the whole
28266 call stack. If the two arguments are equal, show the single frame
28267 at the corresponding level. It is an error if @var{low-frame} is
28268 larger than the actual number of frames. On the other hand,
28269 @var{high-frame} may be larger than the actual number of frames, in
28270 which case only existing frames will be returned.
28272 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28273 the variables; if it is 1 or @code{--all-values}, print also their
28274 values; and if it is 2 or @code{--simple-values}, print the name,
28275 type and value for simple data types, and the name and type for arrays,
28276 structures and unions.
28278 Use of this command to obtain arguments in a single frame is
28279 deprecated in favor of the @samp{-stack-list-variables} command.
28281 @subsubheading @value{GDBN} Command
28283 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28284 @samp{gdb_get_args} command which partially overlaps with the
28285 functionality of @samp{-stack-list-arguments}.
28287 @subsubheading Example
28294 frame=@{level="0",addr="0x00010734",func="callee4",
28295 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28296 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28297 frame=@{level="1",addr="0x0001076c",func="callee3",
28298 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28299 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28300 frame=@{level="2",addr="0x0001078c",func="callee2",
28301 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28302 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28303 frame=@{level="3",addr="0x000107b4",func="callee1",
28304 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28305 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28306 frame=@{level="4",addr="0x000107e0",func="main",
28307 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28308 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28310 -stack-list-arguments 0
28313 frame=@{level="0",args=[]@},
28314 frame=@{level="1",args=[name="strarg"]@},
28315 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28316 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28317 frame=@{level="4",args=[]@}]
28319 -stack-list-arguments 1
28322 frame=@{level="0",args=[]@},
28324 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28325 frame=@{level="2",args=[
28326 @{name="intarg",value="2"@},
28327 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28328 @{frame=@{level="3",args=[
28329 @{name="intarg",value="2"@},
28330 @{name="strarg",value="0x11940 \"A string argument.\""@},
28331 @{name="fltarg",value="3.5"@}]@},
28332 frame=@{level="4",args=[]@}]
28334 -stack-list-arguments 0 2 2
28335 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28337 -stack-list-arguments 1 2 2
28338 ^done,stack-args=[frame=@{level="2",
28339 args=[@{name="intarg",value="2"@},
28340 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28344 @c @subheading -stack-list-exception-handlers
28347 @subheading The @code{-stack-list-frames} Command
28348 @findex -stack-list-frames
28350 @subsubheading Synopsis
28353 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28356 List the frames currently on the stack. For each frame it displays the
28361 The frame number, 0 being the topmost frame, i.e., the innermost function.
28363 The @code{$pc} value for that frame.
28367 File name of the source file where the function lives.
28368 @item @var{fullname}
28369 The full file name of the source file where the function lives.
28371 Line number corresponding to the @code{$pc}.
28373 The shared library where this function is defined. This is only given
28374 if the frame's function is not known.
28377 If invoked without arguments, this command prints a backtrace for the
28378 whole stack. If given two integer arguments, it shows the frames whose
28379 levels are between the two arguments (inclusive). If the two arguments
28380 are equal, it shows the single frame at the corresponding level. It is
28381 an error if @var{low-frame} is larger than the actual number of
28382 frames. On the other hand, @var{high-frame} may be larger than the
28383 actual number of frames, in which case only existing frames will be returned.
28385 @subsubheading @value{GDBN} Command
28387 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28389 @subsubheading Example
28391 Full stack backtrace:
28397 [frame=@{level="0",addr="0x0001076c",func="foo",
28398 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28399 frame=@{level="1",addr="0x000107a4",func="foo",
28400 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28401 frame=@{level="2",addr="0x000107a4",func="foo",
28402 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28403 frame=@{level="3",addr="0x000107a4",func="foo",
28404 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28405 frame=@{level="4",addr="0x000107a4",func="foo",
28406 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28407 frame=@{level="5",addr="0x000107a4",func="foo",
28408 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28409 frame=@{level="6",addr="0x000107a4",func="foo",
28410 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28411 frame=@{level="7",addr="0x000107a4",func="foo",
28412 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28413 frame=@{level="8",addr="0x000107a4",func="foo",
28414 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28415 frame=@{level="9",addr="0x000107a4",func="foo",
28416 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28417 frame=@{level="10",addr="0x000107a4",func="foo",
28418 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28419 frame=@{level="11",addr="0x00010738",func="main",
28420 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28424 Show frames between @var{low_frame} and @var{high_frame}:
28428 -stack-list-frames 3 5
28430 [frame=@{level="3",addr="0x000107a4",func="foo",
28431 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28432 frame=@{level="4",addr="0x000107a4",func="foo",
28433 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28434 frame=@{level="5",addr="0x000107a4",func="foo",
28435 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28439 Show a single frame:
28443 -stack-list-frames 3 3
28445 [frame=@{level="3",addr="0x000107a4",func="foo",
28446 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28451 @subheading The @code{-stack-list-locals} Command
28452 @findex -stack-list-locals
28454 @subsubheading Synopsis
28457 -stack-list-locals @var{print-values}
28460 Display the local variable names for the selected frame. If
28461 @var{print-values} is 0 or @code{--no-values}, print only the names of
28462 the variables; if it is 1 or @code{--all-values}, print also their
28463 values; and if it is 2 or @code{--simple-values}, print the name,
28464 type and value for simple data types, and the name and type for arrays,
28465 structures and unions. In this last case, a frontend can immediately
28466 display the value of simple data types and create variable objects for
28467 other data types when the user wishes to explore their values in
28470 This command is deprecated in favor of the
28471 @samp{-stack-list-variables} command.
28473 @subsubheading @value{GDBN} Command
28475 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28477 @subsubheading Example
28481 -stack-list-locals 0
28482 ^done,locals=[name="A",name="B",name="C"]
28484 -stack-list-locals --all-values
28485 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28486 @{name="C",value="@{1, 2, 3@}"@}]
28487 -stack-list-locals --simple-values
28488 ^done,locals=[@{name="A",type="int",value="1"@},
28489 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28493 @subheading The @code{-stack-list-variables} Command
28494 @findex -stack-list-variables
28496 @subsubheading Synopsis
28499 -stack-list-variables @var{print-values}
28502 Display the names of local variables and function arguments for the selected frame. If
28503 @var{print-values} is 0 or @code{--no-values}, print only the names of
28504 the variables; if it is 1 or @code{--all-values}, print also their
28505 values; and if it is 2 or @code{--simple-values}, print the name,
28506 type and value for simple data types, and the name and type for arrays,
28507 structures and unions.
28509 @subsubheading Example
28513 -stack-list-variables --thread 1 --frame 0 --all-values
28514 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28519 @subheading The @code{-stack-select-frame} Command
28520 @findex -stack-select-frame
28522 @subsubheading Synopsis
28525 -stack-select-frame @var{framenum}
28528 Change the selected frame. Select a different frame @var{framenum} on
28531 This command in deprecated in favor of passing the @samp{--frame}
28532 option to every command.
28534 @subsubheading @value{GDBN} Command
28536 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28537 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28539 @subsubheading Example
28543 -stack-select-frame 2
28548 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28549 @node GDB/MI Variable Objects
28550 @section @sc{gdb/mi} Variable Objects
28554 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28556 For the implementation of a variable debugger window (locals, watched
28557 expressions, etc.), we are proposing the adaptation of the existing code
28558 used by @code{Insight}.
28560 The two main reasons for that are:
28564 It has been proven in practice (it is already on its second generation).
28567 It will shorten development time (needless to say how important it is
28571 The original interface was designed to be used by Tcl code, so it was
28572 slightly changed so it could be used through @sc{gdb/mi}. This section
28573 describes the @sc{gdb/mi} operations that will be available and gives some
28574 hints about their use.
28576 @emph{Note}: In addition to the set of operations described here, we
28577 expect the @sc{gui} implementation of a variable window to require, at
28578 least, the following operations:
28581 @item @code{-gdb-show} @code{output-radix}
28582 @item @code{-stack-list-arguments}
28583 @item @code{-stack-list-locals}
28584 @item @code{-stack-select-frame}
28589 @subheading Introduction to Variable Objects
28591 @cindex variable objects in @sc{gdb/mi}
28593 Variable objects are "object-oriented" MI interface for examining and
28594 changing values of expressions. Unlike some other MI interfaces that
28595 work with expressions, variable objects are specifically designed for
28596 simple and efficient presentation in the frontend. A variable object
28597 is identified by string name. When a variable object is created, the
28598 frontend specifies the expression for that variable object. The
28599 expression can be a simple variable, or it can be an arbitrary complex
28600 expression, and can even involve CPU registers. After creating a
28601 variable object, the frontend can invoke other variable object
28602 operations---for example to obtain or change the value of a variable
28603 object, or to change display format.
28605 Variable objects have hierarchical tree structure. Any variable object
28606 that corresponds to a composite type, such as structure in C, has
28607 a number of child variable objects, for example corresponding to each
28608 element of a structure. A child variable object can itself have
28609 children, recursively. Recursion ends when we reach
28610 leaf variable objects, which always have built-in types. Child variable
28611 objects are created only by explicit request, so if a frontend
28612 is not interested in the children of a particular variable object, no
28613 child will be created.
28615 For a leaf variable object it is possible to obtain its value as a
28616 string, or set the value from a string. String value can be also
28617 obtained for a non-leaf variable object, but it's generally a string
28618 that only indicates the type of the object, and does not list its
28619 contents. Assignment to a non-leaf variable object is not allowed.
28621 A frontend does not need to read the values of all variable objects each time
28622 the program stops. Instead, MI provides an update command that lists all
28623 variable objects whose values has changed since the last update
28624 operation. This considerably reduces the amount of data that must
28625 be transferred to the frontend. As noted above, children variable
28626 objects are created on demand, and only leaf variable objects have a
28627 real value. As result, gdb will read target memory only for leaf
28628 variables that frontend has created.
28630 The automatic update is not always desirable. For example, a frontend
28631 might want to keep a value of some expression for future reference,
28632 and never update it. For another example, fetching memory is
28633 relatively slow for embedded targets, so a frontend might want
28634 to disable automatic update for the variables that are either not
28635 visible on the screen, or ``closed''. This is possible using so
28636 called ``frozen variable objects''. Such variable objects are never
28637 implicitly updated.
28639 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28640 fixed variable object, the expression is parsed when the variable
28641 object is created, including associating identifiers to specific
28642 variables. The meaning of expression never changes. For a floating
28643 variable object the values of variables whose names appear in the
28644 expressions are re-evaluated every time in the context of the current
28645 frame. Consider this example:
28650 struct work_state state;
28657 If a fixed variable object for the @code{state} variable is created in
28658 this function, and we enter the recursive call, the variable
28659 object will report the value of @code{state} in the top-level
28660 @code{do_work} invocation. On the other hand, a floating variable
28661 object will report the value of @code{state} in the current frame.
28663 If an expression specified when creating a fixed variable object
28664 refers to a local variable, the variable object becomes bound to the
28665 thread and frame in which the variable object is created. When such
28666 variable object is updated, @value{GDBN} makes sure that the
28667 thread/frame combination the variable object is bound to still exists,
28668 and re-evaluates the variable object in context of that thread/frame.
28670 The following is the complete set of @sc{gdb/mi} operations defined to
28671 access this functionality:
28673 @multitable @columnfractions .4 .6
28674 @item @strong{Operation}
28675 @tab @strong{Description}
28677 @item @code{-enable-pretty-printing}
28678 @tab enable Python-based pretty-printing
28679 @item @code{-var-create}
28680 @tab create a variable object
28681 @item @code{-var-delete}
28682 @tab delete the variable object and/or its children
28683 @item @code{-var-set-format}
28684 @tab set the display format of this variable
28685 @item @code{-var-show-format}
28686 @tab show the display format of this variable
28687 @item @code{-var-info-num-children}
28688 @tab tells how many children this object has
28689 @item @code{-var-list-children}
28690 @tab return a list of the object's children
28691 @item @code{-var-info-type}
28692 @tab show the type of this variable object
28693 @item @code{-var-info-expression}
28694 @tab print parent-relative expression that this variable object represents
28695 @item @code{-var-info-path-expression}
28696 @tab print full expression that this variable object represents
28697 @item @code{-var-show-attributes}
28698 @tab is this variable editable? does it exist here?
28699 @item @code{-var-evaluate-expression}
28700 @tab get the value of this variable
28701 @item @code{-var-assign}
28702 @tab set the value of this variable
28703 @item @code{-var-update}
28704 @tab update the variable and its children
28705 @item @code{-var-set-frozen}
28706 @tab set frozeness attribute
28707 @item @code{-var-set-update-range}
28708 @tab set range of children to display on update
28711 In the next subsection we describe each operation in detail and suggest
28712 how it can be used.
28714 @subheading Description And Use of Operations on Variable Objects
28716 @subheading The @code{-enable-pretty-printing} Command
28717 @findex -enable-pretty-printing
28720 -enable-pretty-printing
28723 @value{GDBN} allows Python-based visualizers to affect the output of the
28724 MI variable object commands. However, because there was no way to
28725 implement this in a fully backward-compatible way, a front end must
28726 request that this functionality be enabled.
28728 Once enabled, this feature cannot be disabled.
28730 Note that if Python support has not been compiled into @value{GDBN},
28731 this command will still succeed (and do nothing).
28733 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28734 may work differently in future versions of @value{GDBN}.
28736 @subheading The @code{-var-create} Command
28737 @findex -var-create
28739 @subsubheading Synopsis
28742 -var-create @{@var{name} | "-"@}
28743 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28746 This operation creates a variable object, which allows the monitoring of
28747 a variable, the result of an expression, a memory cell or a CPU
28750 The @var{name} parameter is the string by which the object can be
28751 referenced. It must be unique. If @samp{-} is specified, the varobj
28752 system will generate a string ``varNNNNNN'' automatically. It will be
28753 unique provided that one does not specify @var{name} of that format.
28754 The command fails if a duplicate name is found.
28756 The frame under which the expression should be evaluated can be
28757 specified by @var{frame-addr}. A @samp{*} indicates that the current
28758 frame should be used. A @samp{@@} indicates that a floating variable
28759 object must be created.
28761 @var{expression} is any expression valid on the current language set (must not
28762 begin with a @samp{*}), or one of the following:
28766 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28769 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28772 @samp{$@var{regname}} --- a CPU register name
28775 @cindex dynamic varobj
28776 A varobj's contents may be provided by a Python-based pretty-printer. In this
28777 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28778 have slightly different semantics in some cases. If the
28779 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28780 will never create a dynamic varobj. This ensures backward
28781 compatibility for existing clients.
28783 @subsubheading Result
28785 This operation returns attributes of the newly-created varobj. These
28790 The name of the varobj.
28793 The number of children of the varobj. This number is not necessarily
28794 reliable for a dynamic varobj. Instead, you must examine the
28795 @samp{has_more} attribute.
28798 The varobj's scalar value. For a varobj whose type is some sort of
28799 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28800 will not be interesting.
28803 The varobj's type. This is a string representation of the type, as
28804 would be printed by the @value{GDBN} CLI.
28807 If a variable object is bound to a specific thread, then this is the
28808 thread's identifier.
28811 For a dynamic varobj, this indicates whether there appear to be any
28812 children available. For a non-dynamic varobj, this will be 0.
28815 This attribute will be present and have the value @samp{1} if the
28816 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28817 then this attribute will not be present.
28820 A dynamic varobj can supply a display hint to the front end. The
28821 value comes directly from the Python pretty-printer object's
28822 @code{display_hint} method. @xref{Pretty Printing API}.
28825 Typical output will look like this:
28828 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28829 has_more="@var{has_more}"
28833 @subheading The @code{-var-delete} Command
28834 @findex -var-delete
28836 @subsubheading Synopsis
28839 -var-delete [ -c ] @var{name}
28842 Deletes a previously created variable object and all of its children.
28843 With the @samp{-c} option, just deletes the children.
28845 Returns an error if the object @var{name} is not found.
28848 @subheading The @code{-var-set-format} Command
28849 @findex -var-set-format
28851 @subsubheading Synopsis
28854 -var-set-format @var{name} @var{format-spec}
28857 Sets the output format for the value of the object @var{name} to be
28860 @anchor{-var-set-format}
28861 The syntax for the @var{format-spec} is as follows:
28864 @var{format-spec} @expansion{}
28865 @{binary | decimal | hexadecimal | octal | natural@}
28868 The natural format is the default format choosen automatically
28869 based on the variable type (like decimal for an @code{int}, hex
28870 for pointers, etc.).
28872 For a variable with children, the format is set only on the
28873 variable itself, and the children are not affected.
28875 @subheading The @code{-var-show-format} Command
28876 @findex -var-show-format
28878 @subsubheading Synopsis
28881 -var-show-format @var{name}
28884 Returns the format used to display the value of the object @var{name}.
28887 @var{format} @expansion{}
28892 @subheading The @code{-var-info-num-children} Command
28893 @findex -var-info-num-children
28895 @subsubheading Synopsis
28898 -var-info-num-children @var{name}
28901 Returns the number of children of a variable object @var{name}:
28907 Note that this number is not completely reliable for a dynamic varobj.
28908 It will return the current number of children, but more children may
28912 @subheading The @code{-var-list-children} Command
28913 @findex -var-list-children
28915 @subsubheading Synopsis
28918 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28920 @anchor{-var-list-children}
28922 Return a list of the children of the specified variable object and
28923 create variable objects for them, if they do not already exist. With
28924 a single argument or if @var{print-values} has a value of 0 or
28925 @code{--no-values}, print only the names of the variables; if
28926 @var{print-values} is 1 or @code{--all-values}, also print their
28927 values; and if it is 2 or @code{--simple-values} print the name and
28928 value for simple data types and just the name for arrays, structures
28931 @var{from} and @var{to}, if specified, indicate the range of children
28932 to report. If @var{from} or @var{to} is less than zero, the range is
28933 reset and all children will be reported. Otherwise, children starting
28934 at @var{from} (zero-based) and up to and excluding @var{to} will be
28937 If a child range is requested, it will only affect the current call to
28938 @code{-var-list-children}, but not future calls to @code{-var-update}.
28939 For this, you must instead use @code{-var-set-update-range}. The
28940 intent of this approach is to enable a front end to implement any
28941 update approach it likes; for example, scrolling a view may cause the
28942 front end to request more children with @code{-var-list-children}, and
28943 then the front end could call @code{-var-set-update-range} with a
28944 different range to ensure that future updates are restricted to just
28947 For each child the following results are returned:
28952 Name of the variable object created for this child.
28955 The expression to be shown to the user by the front end to designate this child.
28956 For example this may be the name of a structure member.
28958 For a dynamic varobj, this value cannot be used to form an
28959 expression. There is no way to do this at all with a dynamic varobj.
28961 For C/C@t{++} structures there are several pseudo children returned to
28962 designate access qualifiers. For these pseudo children @var{exp} is
28963 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28964 type and value are not present.
28966 A dynamic varobj will not report the access qualifying
28967 pseudo-children, regardless of the language. This information is not
28968 available at all with a dynamic varobj.
28971 Number of children this child has. For a dynamic varobj, this will be
28975 The type of the child.
28978 If values were requested, this is the value.
28981 If this variable object is associated with a thread, this is the thread id.
28982 Otherwise this result is not present.
28985 If the variable object is frozen, this variable will be present with a value of 1.
28988 The result may have its own attributes:
28992 A dynamic varobj can supply a display hint to the front end. The
28993 value comes directly from the Python pretty-printer object's
28994 @code{display_hint} method. @xref{Pretty Printing API}.
28997 This is an integer attribute which is nonzero if there are children
28998 remaining after the end of the selected range.
29001 @subsubheading Example
29005 -var-list-children n
29006 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29007 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29009 -var-list-children --all-values n
29010 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29011 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29015 @subheading The @code{-var-info-type} Command
29016 @findex -var-info-type
29018 @subsubheading Synopsis
29021 -var-info-type @var{name}
29024 Returns the type of the specified variable @var{name}. The type is
29025 returned as a string in the same format as it is output by the
29029 type=@var{typename}
29033 @subheading The @code{-var-info-expression} Command
29034 @findex -var-info-expression
29036 @subsubheading Synopsis
29039 -var-info-expression @var{name}
29042 Returns a string that is suitable for presenting this
29043 variable object in user interface. The string is generally
29044 not valid expression in the current language, and cannot be evaluated.
29046 For example, if @code{a} is an array, and variable object
29047 @code{A} was created for @code{a}, then we'll get this output:
29050 (gdb) -var-info-expression A.1
29051 ^done,lang="C",exp="1"
29055 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29057 Note that the output of the @code{-var-list-children} command also
29058 includes those expressions, so the @code{-var-info-expression} command
29061 @subheading The @code{-var-info-path-expression} Command
29062 @findex -var-info-path-expression
29064 @subsubheading Synopsis
29067 -var-info-path-expression @var{name}
29070 Returns an expression that can be evaluated in the current
29071 context and will yield the same value that a variable object has.
29072 Compare this with the @code{-var-info-expression} command, which
29073 result can be used only for UI presentation. Typical use of
29074 the @code{-var-info-path-expression} command is creating a
29075 watchpoint from a variable object.
29077 This command is currently not valid for children of a dynamic varobj,
29078 and will give an error when invoked on one.
29080 For example, suppose @code{C} is a C@t{++} class, derived from class
29081 @code{Base}, and that the @code{Base} class has a member called
29082 @code{m_size}. Assume a variable @code{c} is has the type of
29083 @code{C} and a variable object @code{C} was created for variable
29084 @code{c}. Then, we'll get this output:
29086 (gdb) -var-info-path-expression C.Base.public.m_size
29087 ^done,path_expr=((Base)c).m_size)
29090 @subheading The @code{-var-show-attributes} Command
29091 @findex -var-show-attributes
29093 @subsubheading Synopsis
29096 -var-show-attributes @var{name}
29099 List attributes of the specified variable object @var{name}:
29102 status=@var{attr} [ ( ,@var{attr} )* ]
29106 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29108 @subheading The @code{-var-evaluate-expression} Command
29109 @findex -var-evaluate-expression
29111 @subsubheading Synopsis
29114 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29117 Evaluates the expression that is represented by the specified variable
29118 object and returns its value as a string. The format of the string
29119 can be specified with the @samp{-f} option. The possible values of
29120 this option are the same as for @code{-var-set-format}
29121 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29122 the current display format will be used. The current display format
29123 can be changed using the @code{-var-set-format} command.
29129 Note that one must invoke @code{-var-list-children} for a variable
29130 before the value of a child variable can be evaluated.
29132 @subheading The @code{-var-assign} Command
29133 @findex -var-assign
29135 @subsubheading Synopsis
29138 -var-assign @var{name} @var{expression}
29141 Assigns the value of @var{expression} to the variable object specified
29142 by @var{name}. The object must be @samp{editable}. If the variable's
29143 value is altered by the assign, the variable will show up in any
29144 subsequent @code{-var-update} list.
29146 @subsubheading Example
29154 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29158 @subheading The @code{-var-update} Command
29159 @findex -var-update
29161 @subsubheading Synopsis
29164 -var-update [@var{print-values}] @{@var{name} | "*"@}
29167 Reevaluate the expressions corresponding to the variable object
29168 @var{name} and all its direct and indirect children, and return the
29169 list of variable objects whose values have changed; @var{name} must
29170 be a root variable object. Here, ``changed'' means that the result of
29171 @code{-var-evaluate-expression} before and after the
29172 @code{-var-update} is different. If @samp{*} is used as the variable
29173 object names, all existing variable objects are updated, except
29174 for frozen ones (@pxref{-var-set-frozen}). The option
29175 @var{print-values} determines whether both names and values, or just
29176 names are printed. The possible values of this option are the same
29177 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29178 recommended to use the @samp{--all-values} option, to reduce the
29179 number of MI commands needed on each program stop.
29181 With the @samp{*} parameter, if a variable object is bound to a
29182 currently running thread, it will not be updated, without any
29185 If @code{-var-set-update-range} was previously used on a varobj, then
29186 only the selected range of children will be reported.
29188 @code{-var-update} reports all the changed varobjs in a tuple named
29191 Each item in the change list is itself a tuple holding:
29195 The name of the varobj.
29198 If values were requested for this update, then this field will be
29199 present and will hold the value of the varobj.
29202 @anchor{-var-update}
29203 This field is a string which may take one of three values:
29207 The variable object's current value is valid.
29210 The variable object does not currently hold a valid value but it may
29211 hold one in the future if its associated expression comes back into
29215 The variable object no longer holds a valid value.
29216 This can occur when the executable file being debugged has changed,
29217 either through recompilation or by using the @value{GDBN} @code{file}
29218 command. The front end should normally choose to delete these variable
29222 In the future new values may be added to this list so the front should
29223 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29226 This is only present if the varobj is still valid. If the type
29227 changed, then this will be the string @samp{true}; otherwise it will
29231 If the varobj's type changed, then this field will be present and will
29234 @item new_num_children
29235 For a dynamic varobj, if the number of children changed, or if the
29236 type changed, this will be the new number of children.
29238 The @samp{numchild} field in other varobj responses is generally not
29239 valid for a dynamic varobj -- it will show the number of children that
29240 @value{GDBN} knows about, but because dynamic varobjs lazily
29241 instantiate their children, this will not reflect the number of
29242 children which may be available.
29244 The @samp{new_num_children} attribute only reports changes to the
29245 number of children known by @value{GDBN}. This is the only way to
29246 detect whether an update has removed children (which necessarily can
29247 only happen at the end of the update range).
29250 The display hint, if any.
29253 This is an integer value, which will be 1 if there are more children
29254 available outside the varobj's update range.
29257 This attribute will be present and have the value @samp{1} if the
29258 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29259 then this attribute will not be present.
29262 If new children were added to a dynamic varobj within the selected
29263 update range (as set by @code{-var-set-update-range}), then they will
29264 be listed in this attribute.
29267 @subsubheading Example
29274 -var-update --all-values var1
29275 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29276 type_changed="false"@}]
29280 @subheading The @code{-var-set-frozen} Command
29281 @findex -var-set-frozen
29282 @anchor{-var-set-frozen}
29284 @subsubheading Synopsis
29287 -var-set-frozen @var{name} @var{flag}
29290 Set the frozenness flag on the variable object @var{name}. The
29291 @var{flag} parameter should be either @samp{1} to make the variable
29292 frozen or @samp{0} to make it unfrozen. If a variable object is
29293 frozen, then neither itself, nor any of its children, are
29294 implicitly updated by @code{-var-update} of
29295 a parent variable or by @code{-var-update *}. Only
29296 @code{-var-update} of the variable itself will update its value and
29297 values of its children. After a variable object is unfrozen, it is
29298 implicitly updated by all subsequent @code{-var-update} operations.
29299 Unfreezing a variable does not update it, only subsequent
29300 @code{-var-update} does.
29302 @subsubheading Example
29306 -var-set-frozen V 1
29311 @subheading The @code{-var-set-update-range} command
29312 @findex -var-set-update-range
29313 @anchor{-var-set-update-range}
29315 @subsubheading Synopsis
29318 -var-set-update-range @var{name} @var{from} @var{to}
29321 Set the range of children to be returned by future invocations of
29322 @code{-var-update}.
29324 @var{from} and @var{to} indicate the range of children to report. If
29325 @var{from} or @var{to} is less than zero, the range is reset and all
29326 children will be reported. Otherwise, children starting at @var{from}
29327 (zero-based) and up to and excluding @var{to} will be reported.
29329 @subsubheading Example
29333 -var-set-update-range V 1 2
29337 @subheading The @code{-var-set-visualizer} command
29338 @findex -var-set-visualizer
29339 @anchor{-var-set-visualizer}
29341 @subsubheading Synopsis
29344 -var-set-visualizer @var{name} @var{visualizer}
29347 Set a visualizer for the variable object @var{name}.
29349 @var{visualizer} is the visualizer to use. The special value
29350 @samp{None} means to disable any visualizer in use.
29352 If not @samp{None}, @var{visualizer} must be a Python expression.
29353 This expression must evaluate to a callable object which accepts a
29354 single argument. @value{GDBN} will call this object with the value of
29355 the varobj @var{name} as an argument (this is done so that the same
29356 Python pretty-printing code can be used for both the CLI and MI).
29357 When called, this object must return an object which conforms to the
29358 pretty-printing interface (@pxref{Pretty Printing API}).
29360 The pre-defined function @code{gdb.default_visualizer} may be used to
29361 select a visualizer by following the built-in process
29362 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29363 a varobj is created, and so ordinarily is not needed.
29365 This feature is only available if Python support is enabled. The MI
29366 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29367 can be used to check this.
29369 @subsubheading Example
29371 Resetting the visualizer:
29375 -var-set-visualizer V None
29379 Reselecting the default (type-based) visualizer:
29383 -var-set-visualizer V gdb.default_visualizer
29387 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29388 can be used to instantiate this class for a varobj:
29392 -var-set-visualizer V "lambda val: SomeClass()"
29396 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29397 @node GDB/MI Data Manipulation
29398 @section @sc{gdb/mi} Data Manipulation
29400 @cindex data manipulation, in @sc{gdb/mi}
29401 @cindex @sc{gdb/mi}, data manipulation
29402 This section describes the @sc{gdb/mi} commands that manipulate data:
29403 examine memory and registers, evaluate expressions, etc.
29405 @c REMOVED FROM THE INTERFACE.
29406 @c @subheading -data-assign
29407 @c Change the value of a program variable. Plenty of side effects.
29408 @c @subsubheading GDB Command
29410 @c @subsubheading Example
29413 @subheading The @code{-data-disassemble} Command
29414 @findex -data-disassemble
29416 @subsubheading Synopsis
29420 [ -s @var{start-addr} -e @var{end-addr} ]
29421 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29429 @item @var{start-addr}
29430 is the beginning address (or @code{$pc})
29431 @item @var{end-addr}
29433 @item @var{filename}
29434 is the name of the file to disassemble
29435 @item @var{linenum}
29436 is the line number to disassemble around
29438 is the number of disassembly lines to be produced. If it is -1,
29439 the whole function will be disassembled, in case no @var{end-addr} is
29440 specified. If @var{end-addr} is specified as a non-zero value, and
29441 @var{lines} is lower than the number of disassembly lines between
29442 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29443 displayed; if @var{lines} is higher than the number of lines between
29444 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29447 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29448 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29449 mixed source and disassembly with raw opcodes).
29452 @subsubheading Result
29454 The output for each instruction is composed of four fields:
29463 Note that whatever included in the instruction field, is not manipulated
29464 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29466 @subsubheading @value{GDBN} Command
29468 There's no direct mapping from this command to the CLI.
29470 @subsubheading Example
29472 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29476 -data-disassemble -s $pc -e "$pc + 20" -- 0
29479 @{address="0x000107c0",func-name="main",offset="4",
29480 inst="mov 2, %o0"@},
29481 @{address="0x000107c4",func-name="main",offset="8",
29482 inst="sethi %hi(0x11800), %o2"@},
29483 @{address="0x000107c8",func-name="main",offset="12",
29484 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29485 @{address="0x000107cc",func-name="main",offset="16",
29486 inst="sethi %hi(0x11800), %o2"@},
29487 @{address="0x000107d0",func-name="main",offset="20",
29488 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29492 Disassemble the whole @code{main} function. Line 32 is part of
29496 -data-disassemble -f basics.c -l 32 -- 0
29498 @{address="0x000107bc",func-name="main",offset="0",
29499 inst="save %sp, -112, %sp"@},
29500 @{address="0x000107c0",func-name="main",offset="4",
29501 inst="mov 2, %o0"@},
29502 @{address="0x000107c4",func-name="main",offset="8",
29503 inst="sethi %hi(0x11800), %o2"@},
29505 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29506 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29510 Disassemble 3 instructions from the start of @code{main}:
29514 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29516 @{address="0x000107bc",func-name="main",offset="0",
29517 inst="save %sp, -112, %sp"@},
29518 @{address="0x000107c0",func-name="main",offset="4",
29519 inst="mov 2, %o0"@},
29520 @{address="0x000107c4",func-name="main",offset="8",
29521 inst="sethi %hi(0x11800), %o2"@}]
29525 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29529 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29531 src_and_asm_line=@{line="31",
29532 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29533 testsuite/gdb.mi/basics.c",line_asm_insn=[
29534 @{address="0x000107bc",func-name="main",offset="0",
29535 inst="save %sp, -112, %sp"@}]@},
29536 src_and_asm_line=@{line="32",
29537 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29538 testsuite/gdb.mi/basics.c",line_asm_insn=[
29539 @{address="0x000107c0",func-name="main",offset="4",
29540 inst="mov 2, %o0"@},
29541 @{address="0x000107c4",func-name="main",offset="8",
29542 inst="sethi %hi(0x11800), %o2"@}]@}]
29547 @subheading The @code{-data-evaluate-expression} Command
29548 @findex -data-evaluate-expression
29550 @subsubheading Synopsis
29553 -data-evaluate-expression @var{expr}
29556 Evaluate @var{expr} as an expression. The expression could contain an
29557 inferior function call. The function call will execute synchronously.
29558 If the expression contains spaces, it must be enclosed in double quotes.
29560 @subsubheading @value{GDBN} Command
29562 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29563 @samp{call}. In @code{gdbtk} only, there's a corresponding
29564 @samp{gdb_eval} command.
29566 @subsubheading Example
29568 In the following example, the numbers that precede the commands are the
29569 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29570 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29574 211-data-evaluate-expression A
29577 311-data-evaluate-expression &A
29578 311^done,value="0xefffeb7c"
29580 411-data-evaluate-expression A+3
29583 511-data-evaluate-expression "A + 3"
29589 @subheading The @code{-data-list-changed-registers} Command
29590 @findex -data-list-changed-registers
29592 @subsubheading Synopsis
29595 -data-list-changed-registers
29598 Display a list of the registers that have changed.
29600 @subsubheading @value{GDBN} Command
29602 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29603 has the corresponding command @samp{gdb_changed_register_list}.
29605 @subsubheading Example
29607 On a PPC MBX board:
29615 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29616 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29619 -data-list-changed-registers
29620 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29621 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29622 "24","25","26","27","28","30","31","64","65","66","67","69"]
29627 @subheading The @code{-data-list-register-names} Command
29628 @findex -data-list-register-names
29630 @subsubheading Synopsis
29633 -data-list-register-names [ ( @var{regno} )+ ]
29636 Show a list of register names for the current target. If no arguments
29637 are given, it shows a list of the names of all the registers. If
29638 integer numbers are given as arguments, it will print a list of the
29639 names of the registers corresponding to the arguments. To ensure
29640 consistency between a register name and its number, the output list may
29641 include empty register names.
29643 @subsubheading @value{GDBN} Command
29645 @value{GDBN} does not have a command which corresponds to
29646 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29647 corresponding command @samp{gdb_regnames}.
29649 @subsubheading Example
29651 For the PPC MBX board:
29654 -data-list-register-names
29655 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29656 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29657 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29658 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29659 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29660 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29661 "", "pc","ps","cr","lr","ctr","xer"]
29663 -data-list-register-names 1 2 3
29664 ^done,register-names=["r1","r2","r3"]
29668 @subheading The @code{-data-list-register-values} Command
29669 @findex -data-list-register-values
29671 @subsubheading Synopsis
29674 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29677 Display the registers' contents. @var{fmt} is the format according to
29678 which the registers' contents are to be returned, followed by an optional
29679 list of numbers specifying the registers to display. A missing list of
29680 numbers indicates that the contents of all the registers must be returned.
29682 Allowed formats for @var{fmt} are:
29699 @subsubheading @value{GDBN} Command
29701 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29702 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29704 @subsubheading Example
29706 For a PPC MBX board (note: line breaks are for readability only, they
29707 don't appear in the actual output):
29711 -data-list-register-values r 64 65
29712 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29713 @{number="65",value="0x00029002"@}]
29715 -data-list-register-values x
29716 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29717 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29718 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29719 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29720 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29721 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29722 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29723 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29724 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29725 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29726 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29727 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29728 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29729 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29730 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29731 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29732 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29733 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29734 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29735 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29736 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29737 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29738 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29739 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29740 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29741 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29742 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29743 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29744 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29745 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29746 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29747 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29748 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29749 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29750 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29751 @{number="69",value="0x20002b03"@}]
29756 @subheading The @code{-data-read-memory} Command
29757 @findex -data-read-memory
29759 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29761 @subsubheading Synopsis
29764 -data-read-memory [ -o @var{byte-offset} ]
29765 @var{address} @var{word-format} @var{word-size}
29766 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29773 @item @var{address}
29774 An expression specifying the address of the first memory word to be
29775 read. Complex expressions containing embedded white space should be
29776 quoted using the C convention.
29778 @item @var{word-format}
29779 The format to be used to print the memory words. The notation is the
29780 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29783 @item @var{word-size}
29784 The size of each memory word in bytes.
29786 @item @var{nr-rows}
29787 The number of rows in the output table.
29789 @item @var{nr-cols}
29790 The number of columns in the output table.
29793 If present, indicates that each row should include an @sc{ascii} dump. The
29794 value of @var{aschar} is used as a padding character when a byte is not a
29795 member of the printable @sc{ascii} character set (printable @sc{ascii}
29796 characters are those whose code is between 32 and 126, inclusively).
29798 @item @var{byte-offset}
29799 An offset to add to the @var{address} before fetching memory.
29802 This command displays memory contents as a table of @var{nr-rows} by
29803 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29804 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29805 (returned as @samp{total-bytes}). Should less than the requested number
29806 of bytes be returned by the target, the missing words are identified
29807 using @samp{N/A}. The number of bytes read from the target is returned
29808 in @samp{nr-bytes} and the starting address used to read memory in
29811 The address of the next/previous row or page is available in
29812 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29815 @subsubheading @value{GDBN} Command
29817 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29818 @samp{gdb_get_mem} memory read command.
29820 @subsubheading Example
29822 Read six bytes of memory starting at @code{bytes+6} but then offset by
29823 @code{-6} bytes. Format as three rows of two columns. One byte per
29824 word. Display each word in hex.
29828 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29829 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29830 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29831 prev-page="0x0000138a",memory=[
29832 @{addr="0x00001390",data=["0x00","0x01"]@},
29833 @{addr="0x00001392",data=["0x02","0x03"]@},
29834 @{addr="0x00001394",data=["0x04","0x05"]@}]
29838 Read two bytes of memory starting at address @code{shorts + 64} and
29839 display as a single word formatted in decimal.
29843 5-data-read-memory shorts+64 d 2 1 1
29844 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29845 next-row="0x00001512",prev-row="0x0000150e",
29846 next-page="0x00001512",prev-page="0x0000150e",memory=[
29847 @{addr="0x00001510",data=["128"]@}]
29851 Read thirty two bytes of memory starting at @code{bytes+16} and format
29852 as eight rows of four columns. Include a string encoding with @samp{x}
29853 used as the non-printable character.
29857 4-data-read-memory bytes+16 x 1 8 4 x
29858 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29859 next-row="0x000013c0",prev-row="0x0000139c",
29860 next-page="0x000013c0",prev-page="0x00001380",memory=[
29861 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29862 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29863 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29864 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29865 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29866 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29867 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29868 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29872 @subheading The @code{-data-read-memory-bytes} Command
29873 @findex -data-read-memory-bytes
29875 @subsubheading Synopsis
29878 -data-read-memory-bytes [ -o @var{byte-offset} ]
29879 @var{address} @var{count}
29886 @item @var{address}
29887 An expression specifying the address of the first memory word to be
29888 read. Complex expressions containing embedded white space should be
29889 quoted using the C convention.
29892 The number of bytes to read. This should be an integer literal.
29894 @item @var{byte-offset}
29895 The offsets in bytes relative to @var{address} at which to start
29896 reading. This should be an integer literal. This option is provided
29897 so that a frontend is not required to first evaluate address and then
29898 perform address arithmetics itself.
29902 This command attempts to read all accessible memory regions in the
29903 specified range. First, all regions marked as unreadable in the memory
29904 map (if one is defined) will be skipped. @xref{Memory Region
29905 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29906 regions. For each one, if reading full region results in an errors,
29907 @value{GDBN} will try to read a subset of the region.
29909 In general, every single byte in the region may be readable or not,
29910 and the only way to read every readable byte is to try a read at
29911 every address, which is not practical. Therefore, @value{GDBN} will
29912 attempt to read all accessible bytes at either beginning or the end
29913 of the region, using a binary division scheme. This heuristic works
29914 well for reading accross a memory map boundary. Note that if a region
29915 has a readable range that is neither at the beginning or the end,
29916 @value{GDBN} will not read it.
29918 The result record (@pxref{GDB/MI Result Records}) that is output of
29919 the command includes a field named @samp{memory} whose content is a
29920 list of tuples. Each tuple represent a successfully read memory block
29921 and has the following fields:
29925 The start address of the memory block, as hexadecimal literal.
29928 The end address of the memory block, as hexadecimal literal.
29931 The offset of the memory block, as hexadecimal literal, relative to
29932 the start address passed to @code{-data-read-memory-bytes}.
29935 The contents of the memory block, in hex.
29941 @subsubheading @value{GDBN} Command
29943 The corresponding @value{GDBN} command is @samp{x}.
29945 @subsubheading Example
29949 -data-read-memory-bytes &a 10
29950 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29952 contents="01000000020000000300"@}]
29957 @subheading The @code{-data-write-memory-bytes} Command
29958 @findex -data-write-memory-bytes
29960 @subsubheading Synopsis
29963 -data-write-memory-bytes @var{address} @var{contents}
29970 @item @var{address}
29971 An expression specifying the address of the first memory word to be
29972 read. Complex expressions containing embedded white space should be
29973 quoted using the C convention.
29975 @item @var{contents}
29976 The hex-encoded bytes to write.
29980 @subsubheading @value{GDBN} Command
29982 There's no corresponding @value{GDBN} command.
29984 @subsubheading Example
29988 -data-write-memory-bytes &a "aabbccdd"
29994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29995 @node GDB/MI Tracepoint Commands
29996 @section @sc{gdb/mi} Tracepoint Commands
29998 The commands defined in this section implement MI support for
29999 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30001 @subheading The @code{-trace-find} Command
30002 @findex -trace-find
30004 @subsubheading Synopsis
30007 -trace-find @var{mode} [@var{parameters}@dots{}]
30010 Find a trace frame using criteria defined by @var{mode} and
30011 @var{parameters}. The following table lists permissible
30012 modes and their parameters. For details of operation, see @ref{tfind}.
30017 No parameters are required. Stops examining trace frames.
30020 An integer is required as parameter. Selects tracepoint frame with
30023 @item tracepoint-number
30024 An integer is required as parameter. Finds next
30025 trace frame that corresponds to tracepoint with the specified number.
30028 An address is required as parameter. Finds
30029 next trace frame that corresponds to any tracepoint at the specified
30032 @item pc-inside-range
30033 Two addresses are required as parameters. Finds next trace
30034 frame that corresponds to a tracepoint at an address inside the
30035 specified range. Both bounds are considered to be inside the range.
30037 @item pc-outside-range
30038 Two addresses are required as parameters. Finds
30039 next trace frame that corresponds to a tracepoint at an address outside
30040 the specified range. Both bounds are considered to be inside the range.
30043 Line specification is required as parameter. @xref{Specify Location}.
30044 Finds next trace frame that corresponds to a tracepoint at
30045 the specified location.
30049 If @samp{none} was passed as @var{mode}, the response does not
30050 have fields. Otherwise, the response may have the following fields:
30054 This field has either @samp{0} or @samp{1} as the value, depending
30055 on whether a matching tracepoint was found.
30058 The index of the found traceframe. This field is present iff
30059 the @samp{found} field has value of @samp{1}.
30062 The index of the found tracepoint. This field is present iff
30063 the @samp{found} field has value of @samp{1}.
30066 The information about the frame corresponding to the found trace
30067 frame. This field is present only if a trace frame was found.
30068 @xref{GDB/MI Frame Information}, for description of this field.
30072 @subsubheading @value{GDBN} Command
30074 The corresponding @value{GDBN} command is @samp{tfind}.
30076 @subheading -trace-define-variable
30077 @findex -trace-define-variable
30079 @subsubheading Synopsis
30082 -trace-define-variable @var{name} [ @var{value} ]
30085 Create trace variable @var{name} if it does not exist. If
30086 @var{value} is specified, sets the initial value of the specified
30087 trace variable to that value. Note that the @var{name} should start
30088 with the @samp{$} character.
30090 @subsubheading @value{GDBN} Command
30092 The corresponding @value{GDBN} command is @samp{tvariable}.
30094 @subheading -trace-list-variables
30095 @findex -trace-list-variables
30097 @subsubheading Synopsis
30100 -trace-list-variables
30103 Return a table of all defined trace variables. Each element of the
30104 table has the following fields:
30108 The name of the trace variable. This field is always present.
30111 The initial value. This is a 64-bit signed integer. This
30112 field is always present.
30115 The value the trace variable has at the moment. This is a 64-bit
30116 signed integer. This field is absent iff current value is
30117 not defined, for example if the trace was never run, or is
30122 @subsubheading @value{GDBN} Command
30124 The corresponding @value{GDBN} command is @samp{tvariables}.
30126 @subsubheading Example
30130 -trace-list-variables
30131 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30132 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30133 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30134 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30135 body=[variable=@{name="$trace_timestamp",initial="0"@}
30136 variable=@{name="$foo",initial="10",current="15"@}]@}
30140 @subheading -trace-save
30141 @findex -trace-save
30143 @subsubheading Synopsis
30146 -trace-save [-r ] @var{filename}
30149 Saves the collected trace data to @var{filename}. Without the
30150 @samp{-r} option, the data is downloaded from the target and saved
30151 in a local file. With the @samp{-r} option the target is asked
30152 to perform the save.
30154 @subsubheading @value{GDBN} Command
30156 The corresponding @value{GDBN} command is @samp{tsave}.
30159 @subheading -trace-start
30160 @findex -trace-start
30162 @subsubheading Synopsis
30168 Starts a tracing experiments. The result of this command does not
30171 @subsubheading @value{GDBN} Command
30173 The corresponding @value{GDBN} command is @samp{tstart}.
30175 @subheading -trace-status
30176 @findex -trace-status
30178 @subsubheading Synopsis
30184 Obtains the status of a tracing experiment. The result may include
30185 the following fields:
30190 May have a value of either @samp{0}, when no tracing operations are
30191 supported, @samp{1}, when all tracing operations are supported, or
30192 @samp{file} when examining trace file. In the latter case, examining
30193 of trace frame is possible but new tracing experiement cannot be
30194 started. This field is always present.
30197 May have a value of either @samp{0} or @samp{1} depending on whether
30198 tracing experiement is in progress on target. This field is present
30199 if @samp{supported} field is not @samp{0}.
30202 Report the reason why the tracing was stopped last time. This field
30203 may be absent iff tracing was never stopped on target yet. The
30204 value of @samp{request} means the tracing was stopped as result of
30205 the @code{-trace-stop} command. The value of @samp{overflow} means
30206 the tracing buffer is full. The value of @samp{disconnection} means
30207 tracing was automatically stopped when @value{GDBN} has disconnected.
30208 The value of @samp{passcount} means tracing was stopped when a
30209 tracepoint was passed a maximal number of times for that tracepoint.
30210 This field is present if @samp{supported} field is not @samp{0}.
30212 @item stopping-tracepoint
30213 The number of tracepoint whose passcount as exceeded. This field is
30214 present iff the @samp{stop-reason} field has the value of
30218 @itemx frames-created
30219 The @samp{frames} field is a count of the total number of trace frames
30220 in the trace buffer, while @samp{frames-created} is the total created
30221 during the run, including ones that were discarded, such as when a
30222 circular trace buffer filled up. Both fields are optional.
30226 These fields tell the current size of the tracing buffer and the
30227 remaining space. These fields are optional.
30230 The value of the circular trace buffer flag. @code{1} means that the
30231 trace buffer is circular and old trace frames will be discarded if
30232 necessary to make room, @code{0} means that the trace buffer is linear
30236 The value of the disconnected tracing flag. @code{1} means that
30237 tracing will continue after @value{GDBN} disconnects, @code{0} means
30238 that the trace run will stop.
30242 @subsubheading @value{GDBN} Command
30244 The corresponding @value{GDBN} command is @samp{tstatus}.
30246 @subheading -trace-stop
30247 @findex -trace-stop
30249 @subsubheading Synopsis
30255 Stops a tracing experiment. The result of this command has the same
30256 fields as @code{-trace-status}, except that the @samp{supported} and
30257 @samp{running} fields are not output.
30259 @subsubheading @value{GDBN} Command
30261 The corresponding @value{GDBN} command is @samp{tstop}.
30264 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30265 @node GDB/MI Symbol Query
30266 @section @sc{gdb/mi} Symbol Query Commands
30270 @subheading The @code{-symbol-info-address} Command
30271 @findex -symbol-info-address
30273 @subsubheading Synopsis
30276 -symbol-info-address @var{symbol}
30279 Describe where @var{symbol} is stored.
30281 @subsubheading @value{GDBN} Command
30283 The corresponding @value{GDBN} command is @samp{info address}.
30285 @subsubheading Example
30289 @subheading The @code{-symbol-info-file} Command
30290 @findex -symbol-info-file
30292 @subsubheading Synopsis
30298 Show the file for the symbol.
30300 @subsubheading @value{GDBN} Command
30302 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30303 @samp{gdb_find_file}.
30305 @subsubheading Example
30309 @subheading The @code{-symbol-info-function} Command
30310 @findex -symbol-info-function
30312 @subsubheading Synopsis
30315 -symbol-info-function
30318 Show which function the symbol lives in.
30320 @subsubheading @value{GDBN} Command
30322 @samp{gdb_get_function} in @code{gdbtk}.
30324 @subsubheading Example
30328 @subheading The @code{-symbol-info-line} Command
30329 @findex -symbol-info-line
30331 @subsubheading Synopsis
30337 Show the core addresses of the code for a source line.
30339 @subsubheading @value{GDBN} Command
30341 The corresponding @value{GDBN} command is @samp{info line}.
30342 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30344 @subsubheading Example
30348 @subheading The @code{-symbol-info-symbol} Command
30349 @findex -symbol-info-symbol
30351 @subsubheading Synopsis
30354 -symbol-info-symbol @var{addr}
30357 Describe what symbol is at location @var{addr}.
30359 @subsubheading @value{GDBN} Command
30361 The corresponding @value{GDBN} command is @samp{info symbol}.
30363 @subsubheading Example
30367 @subheading The @code{-symbol-list-functions} Command
30368 @findex -symbol-list-functions
30370 @subsubheading Synopsis
30373 -symbol-list-functions
30376 List the functions in the executable.
30378 @subsubheading @value{GDBN} Command
30380 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30381 @samp{gdb_search} in @code{gdbtk}.
30383 @subsubheading Example
30388 @subheading The @code{-symbol-list-lines} Command
30389 @findex -symbol-list-lines
30391 @subsubheading Synopsis
30394 -symbol-list-lines @var{filename}
30397 Print the list of lines that contain code and their associated program
30398 addresses for the given source filename. The entries are sorted in
30399 ascending PC order.
30401 @subsubheading @value{GDBN} Command
30403 There is no corresponding @value{GDBN} command.
30405 @subsubheading Example
30408 -symbol-list-lines basics.c
30409 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30415 @subheading The @code{-symbol-list-types} Command
30416 @findex -symbol-list-types
30418 @subsubheading Synopsis
30424 List all the type names.
30426 @subsubheading @value{GDBN} Command
30428 The corresponding commands are @samp{info types} in @value{GDBN},
30429 @samp{gdb_search} in @code{gdbtk}.
30431 @subsubheading Example
30435 @subheading The @code{-symbol-list-variables} Command
30436 @findex -symbol-list-variables
30438 @subsubheading Synopsis
30441 -symbol-list-variables
30444 List all the global and static variable names.
30446 @subsubheading @value{GDBN} Command
30448 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30450 @subsubheading Example
30454 @subheading The @code{-symbol-locate} Command
30455 @findex -symbol-locate
30457 @subsubheading Synopsis
30463 @subsubheading @value{GDBN} Command
30465 @samp{gdb_loc} in @code{gdbtk}.
30467 @subsubheading Example
30471 @subheading The @code{-symbol-type} Command
30472 @findex -symbol-type
30474 @subsubheading Synopsis
30477 -symbol-type @var{variable}
30480 Show type of @var{variable}.
30482 @subsubheading @value{GDBN} Command
30484 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30485 @samp{gdb_obj_variable}.
30487 @subsubheading Example
30492 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30493 @node GDB/MI File Commands
30494 @section @sc{gdb/mi} File Commands
30496 This section describes the GDB/MI commands to specify executable file names
30497 and to read in and obtain symbol table information.
30499 @subheading The @code{-file-exec-and-symbols} Command
30500 @findex -file-exec-and-symbols
30502 @subsubheading Synopsis
30505 -file-exec-and-symbols @var{file}
30508 Specify the executable file to be debugged. This file is the one from
30509 which the symbol table is also read. If no file is specified, the
30510 command clears the executable and symbol information. If breakpoints
30511 are set when using this command with no arguments, @value{GDBN} will produce
30512 error messages. Otherwise, no output is produced, except a completion
30515 @subsubheading @value{GDBN} Command
30517 The corresponding @value{GDBN} command is @samp{file}.
30519 @subsubheading Example
30523 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30529 @subheading The @code{-file-exec-file} Command
30530 @findex -file-exec-file
30532 @subsubheading Synopsis
30535 -file-exec-file @var{file}
30538 Specify the executable file to be debugged. Unlike
30539 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30540 from this file. If used without argument, @value{GDBN} clears the information
30541 about the executable file. No output is produced, except a completion
30544 @subsubheading @value{GDBN} Command
30546 The corresponding @value{GDBN} command is @samp{exec-file}.
30548 @subsubheading Example
30552 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30559 @subheading The @code{-file-list-exec-sections} Command
30560 @findex -file-list-exec-sections
30562 @subsubheading Synopsis
30565 -file-list-exec-sections
30568 List the sections of the current executable file.
30570 @subsubheading @value{GDBN} Command
30572 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30573 information as this command. @code{gdbtk} has a corresponding command
30574 @samp{gdb_load_info}.
30576 @subsubheading Example
30581 @subheading The @code{-file-list-exec-source-file} Command
30582 @findex -file-list-exec-source-file
30584 @subsubheading Synopsis
30587 -file-list-exec-source-file
30590 List the line number, the current source file, and the absolute path
30591 to the current source file for the current executable. The macro
30592 information field has a value of @samp{1} or @samp{0} depending on
30593 whether or not the file includes preprocessor macro information.
30595 @subsubheading @value{GDBN} Command
30597 The @value{GDBN} equivalent is @samp{info source}
30599 @subsubheading Example
30603 123-file-list-exec-source-file
30604 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30609 @subheading The @code{-file-list-exec-source-files} Command
30610 @findex -file-list-exec-source-files
30612 @subsubheading Synopsis
30615 -file-list-exec-source-files
30618 List the source files for the current executable.
30620 It will always output the filename, but only when @value{GDBN} can find
30621 the absolute file name of a source file, will it output the fullname.
30623 @subsubheading @value{GDBN} Command
30625 The @value{GDBN} equivalent is @samp{info sources}.
30626 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30628 @subsubheading Example
30631 -file-list-exec-source-files
30633 @{file=foo.c,fullname=/home/foo.c@},
30634 @{file=/home/bar.c,fullname=/home/bar.c@},
30635 @{file=gdb_could_not_find_fullpath.c@}]
30640 @subheading The @code{-file-list-shared-libraries} Command
30641 @findex -file-list-shared-libraries
30643 @subsubheading Synopsis
30646 -file-list-shared-libraries
30649 List the shared libraries in the program.
30651 @subsubheading @value{GDBN} Command
30653 The corresponding @value{GDBN} command is @samp{info shared}.
30655 @subsubheading Example
30659 @subheading The @code{-file-list-symbol-files} Command
30660 @findex -file-list-symbol-files
30662 @subsubheading Synopsis
30665 -file-list-symbol-files
30670 @subsubheading @value{GDBN} Command
30672 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30674 @subsubheading Example
30679 @subheading The @code{-file-symbol-file} Command
30680 @findex -file-symbol-file
30682 @subsubheading Synopsis
30685 -file-symbol-file @var{file}
30688 Read symbol table info from the specified @var{file} argument. When
30689 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30690 produced, except for a completion notification.
30692 @subsubheading @value{GDBN} Command
30694 The corresponding @value{GDBN} command is @samp{symbol-file}.
30696 @subsubheading Example
30700 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30706 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30707 @node GDB/MI Memory Overlay Commands
30708 @section @sc{gdb/mi} Memory Overlay Commands
30710 The memory overlay commands are not implemented.
30712 @c @subheading -overlay-auto
30714 @c @subheading -overlay-list-mapping-state
30716 @c @subheading -overlay-list-overlays
30718 @c @subheading -overlay-map
30720 @c @subheading -overlay-off
30722 @c @subheading -overlay-on
30724 @c @subheading -overlay-unmap
30726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30727 @node GDB/MI Signal Handling Commands
30728 @section @sc{gdb/mi} Signal Handling Commands
30730 Signal handling commands are not implemented.
30732 @c @subheading -signal-handle
30734 @c @subheading -signal-list-handle-actions
30736 @c @subheading -signal-list-signal-types
30740 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30741 @node GDB/MI Target Manipulation
30742 @section @sc{gdb/mi} Target Manipulation Commands
30745 @subheading The @code{-target-attach} Command
30746 @findex -target-attach
30748 @subsubheading Synopsis
30751 -target-attach @var{pid} | @var{gid} | @var{file}
30754 Attach to a process @var{pid} or a file @var{file} outside of
30755 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30756 group, the id previously returned by
30757 @samp{-list-thread-groups --available} must be used.
30759 @subsubheading @value{GDBN} Command
30761 The corresponding @value{GDBN} command is @samp{attach}.
30763 @subsubheading Example
30767 =thread-created,id="1"
30768 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30774 @subheading The @code{-target-compare-sections} Command
30775 @findex -target-compare-sections
30777 @subsubheading Synopsis
30780 -target-compare-sections [ @var{section} ]
30783 Compare data of section @var{section} on target to the exec file.
30784 Without the argument, all sections are compared.
30786 @subsubheading @value{GDBN} Command
30788 The @value{GDBN} equivalent is @samp{compare-sections}.
30790 @subsubheading Example
30795 @subheading The @code{-target-detach} Command
30796 @findex -target-detach
30798 @subsubheading Synopsis
30801 -target-detach [ @var{pid} | @var{gid} ]
30804 Detach from the remote target which normally resumes its execution.
30805 If either @var{pid} or @var{gid} is specified, detaches from either
30806 the specified process, or specified thread group. There's no output.
30808 @subsubheading @value{GDBN} Command
30810 The corresponding @value{GDBN} command is @samp{detach}.
30812 @subsubheading Example
30822 @subheading The @code{-target-disconnect} Command
30823 @findex -target-disconnect
30825 @subsubheading Synopsis
30831 Disconnect from the remote target. There's no output and the target is
30832 generally not resumed.
30834 @subsubheading @value{GDBN} Command
30836 The corresponding @value{GDBN} command is @samp{disconnect}.
30838 @subsubheading Example
30848 @subheading The @code{-target-download} Command
30849 @findex -target-download
30851 @subsubheading Synopsis
30857 Loads the executable onto the remote target.
30858 It prints out an update message every half second, which includes the fields:
30862 The name of the section.
30864 The size of what has been sent so far for that section.
30866 The size of the section.
30868 The total size of what was sent so far (the current and the previous sections).
30870 The size of the overall executable to download.
30874 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30875 @sc{gdb/mi} Output Syntax}).
30877 In addition, it prints the name and size of the sections, as they are
30878 downloaded. These messages include the following fields:
30882 The name of the section.
30884 The size of the section.
30886 The size of the overall executable to download.
30890 At the end, a summary is printed.
30892 @subsubheading @value{GDBN} Command
30894 The corresponding @value{GDBN} command is @samp{load}.
30896 @subsubheading Example
30898 Note: each status message appears on a single line. Here the messages
30899 have been broken down so that they can fit onto a page.
30904 +download,@{section=".text",section-size="6668",total-size="9880"@}
30905 +download,@{section=".text",section-sent="512",section-size="6668",
30906 total-sent="512",total-size="9880"@}
30907 +download,@{section=".text",section-sent="1024",section-size="6668",
30908 total-sent="1024",total-size="9880"@}
30909 +download,@{section=".text",section-sent="1536",section-size="6668",
30910 total-sent="1536",total-size="9880"@}
30911 +download,@{section=".text",section-sent="2048",section-size="6668",
30912 total-sent="2048",total-size="9880"@}
30913 +download,@{section=".text",section-sent="2560",section-size="6668",
30914 total-sent="2560",total-size="9880"@}
30915 +download,@{section=".text",section-sent="3072",section-size="6668",
30916 total-sent="3072",total-size="9880"@}
30917 +download,@{section=".text",section-sent="3584",section-size="6668",
30918 total-sent="3584",total-size="9880"@}
30919 +download,@{section=".text",section-sent="4096",section-size="6668",
30920 total-sent="4096",total-size="9880"@}
30921 +download,@{section=".text",section-sent="4608",section-size="6668",
30922 total-sent="4608",total-size="9880"@}
30923 +download,@{section=".text",section-sent="5120",section-size="6668",
30924 total-sent="5120",total-size="9880"@}
30925 +download,@{section=".text",section-sent="5632",section-size="6668",
30926 total-sent="5632",total-size="9880"@}
30927 +download,@{section=".text",section-sent="6144",section-size="6668",
30928 total-sent="6144",total-size="9880"@}
30929 +download,@{section=".text",section-sent="6656",section-size="6668",
30930 total-sent="6656",total-size="9880"@}
30931 +download,@{section=".init",section-size="28",total-size="9880"@}
30932 +download,@{section=".fini",section-size="28",total-size="9880"@}
30933 +download,@{section=".data",section-size="3156",total-size="9880"@}
30934 +download,@{section=".data",section-sent="512",section-size="3156",
30935 total-sent="7236",total-size="9880"@}
30936 +download,@{section=".data",section-sent="1024",section-size="3156",
30937 total-sent="7748",total-size="9880"@}
30938 +download,@{section=".data",section-sent="1536",section-size="3156",
30939 total-sent="8260",total-size="9880"@}
30940 +download,@{section=".data",section-sent="2048",section-size="3156",
30941 total-sent="8772",total-size="9880"@}
30942 +download,@{section=".data",section-sent="2560",section-size="3156",
30943 total-sent="9284",total-size="9880"@}
30944 +download,@{section=".data",section-sent="3072",section-size="3156",
30945 total-sent="9796",total-size="9880"@}
30946 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30953 @subheading The @code{-target-exec-status} Command
30954 @findex -target-exec-status
30956 @subsubheading Synopsis
30959 -target-exec-status
30962 Provide information on the state of the target (whether it is running or
30963 not, for instance).
30965 @subsubheading @value{GDBN} Command
30967 There's no equivalent @value{GDBN} command.
30969 @subsubheading Example
30973 @subheading The @code{-target-list-available-targets} Command
30974 @findex -target-list-available-targets
30976 @subsubheading Synopsis
30979 -target-list-available-targets
30982 List the possible targets to connect to.
30984 @subsubheading @value{GDBN} Command
30986 The corresponding @value{GDBN} command is @samp{help target}.
30988 @subsubheading Example
30992 @subheading The @code{-target-list-current-targets} Command
30993 @findex -target-list-current-targets
30995 @subsubheading Synopsis
30998 -target-list-current-targets
31001 Describe the current target.
31003 @subsubheading @value{GDBN} Command
31005 The corresponding information is printed by @samp{info file} (among
31008 @subsubheading Example
31012 @subheading The @code{-target-list-parameters} Command
31013 @findex -target-list-parameters
31015 @subsubheading Synopsis
31018 -target-list-parameters
31024 @subsubheading @value{GDBN} Command
31028 @subsubheading Example
31032 @subheading The @code{-target-select} Command
31033 @findex -target-select
31035 @subsubheading Synopsis
31038 -target-select @var{type} @var{parameters @dots{}}
31041 Connect @value{GDBN} to the remote target. This command takes two args:
31045 The type of target, for instance @samp{remote}, etc.
31046 @item @var{parameters}
31047 Device names, host names and the like. @xref{Target Commands, ,
31048 Commands for Managing Targets}, for more details.
31051 The output is a connection notification, followed by the address at
31052 which the target program is, in the following form:
31055 ^connected,addr="@var{address}",func="@var{function name}",
31056 args=[@var{arg list}]
31059 @subsubheading @value{GDBN} Command
31061 The corresponding @value{GDBN} command is @samp{target}.
31063 @subsubheading Example
31067 -target-select remote /dev/ttya
31068 ^connected,addr="0xfe00a300",func="??",args=[]
31072 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31073 @node GDB/MI File Transfer Commands
31074 @section @sc{gdb/mi} File Transfer Commands
31077 @subheading The @code{-target-file-put} Command
31078 @findex -target-file-put
31080 @subsubheading Synopsis
31083 -target-file-put @var{hostfile} @var{targetfile}
31086 Copy file @var{hostfile} from the host system (the machine running
31087 @value{GDBN}) to @var{targetfile} on the target system.
31089 @subsubheading @value{GDBN} Command
31091 The corresponding @value{GDBN} command is @samp{remote put}.
31093 @subsubheading Example
31097 -target-file-put localfile remotefile
31103 @subheading The @code{-target-file-get} Command
31104 @findex -target-file-get
31106 @subsubheading Synopsis
31109 -target-file-get @var{targetfile} @var{hostfile}
31112 Copy file @var{targetfile} from the target system to @var{hostfile}
31113 on the host system.
31115 @subsubheading @value{GDBN} Command
31117 The corresponding @value{GDBN} command is @samp{remote get}.
31119 @subsubheading Example
31123 -target-file-get remotefile localfile
31129 @subheading The @code{-target-file-delete} Command
31130 @findex -target-file-delete
31132 @subsubheading Synopsis
31135 -target-file-delete @var{targetfile}
31138 Delete @var{targetfile} from the target system.
31140 @subsubheading @value{GDBN} Command
31142 The corresponding @value{GDBN} command is @samp{remote delete}.
31144 @subsubheading Example
31148 -target-file-delete remotefile
31154 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31155 @node GDB/MI Miscellaneous Commands
31156 @section Miscellaneous @sc{gdb/mi} Commands
31158 @c @subheading -gdb-complete
31160 @subheading The @code{-gdb-exit} Command
31163 @subsubheading Synopsis
31169 Exit @value{GDBN} immediately.
31171 @subsubheading @value{GDBN} Command
31173 Approximately corresponds to @samp{quit}.
31175 @subsubheading Example
31185 @subheading The @code{-exec-abort} Command
31186 @findex -exec-abort
31188 @subsubheading Synopsis
31194 Kill the inferior running program.
31196 @subsubheading @value{GDBN} Command
31198 The corresponding @value{GDBN} command is @samp{kill}.
31200 @subsubheading Example
31205 @subheading The @code{-gdb-set} Command
31208 @subsubheading Synopsis
31214 Set an internal @value{GDBN} variable.
31215 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31217 @subsubheading @value{GDBN} Command
31219 The corresponding @value{GDBN} command is @samp{set}.
31221 @subsubheading Example
31231 @subheading The @code{-gdb-show} Command
31234 @subsubheading Synopsis
31240 Show the current value of a @value{GDBN} variable.
31242 @subsubheading @value{GDBN} Command
31244 The corresponding @value{GDBN} command is @samp{show}.
31246 @subsubheading Example
31255 @c @subheading -gdb-source
31258 @subheading The @code{-gdb-version} Command
31259 @findex -gdb-version
31261 @subsubheading Synopsis
31267 Show version information for @value{GDBN}. Used mostly in testing.
31269 @subsubheading @value{GDBN} Command
31271 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31272 default shows this information when you start an interactive session.
31274 @subsubheading Example
31276 @c This example modifies the actual output from GDB to avoid overfull
31282 ~Copyright 2000 Free Software Foundation, Inc.
31283 ~GDB is free software, covered by the GNU General Public License, and
31284 ~you are welcome to change it and/or distribute copies of it under
31285 ~ certain conditions.
31286 ~Type "show copying" to see the conditions.
31287 ~There is absolutely no warranty for GDB. Type "show warranty" for
31289 ~This GDB was configured as
31290 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31295 @subheading The @code{-list-features} Command
31296 @findex -list-features
31298 Returns a list of particular features of the MI protocol that
31299 this version of gdb implements. A feature can be a command,
31300 or a new field in an output of some command, or even an
31301 important bugfix. While a frontend can sometimes detect presence
31302 of a feature at runtime, it is easier to perform detection at debugger
31305 The command returns a list of strings, with each string naming an
31306 available feature. Each returned string is just a name, it does not
31307 have any internal structure. The list of possible feature names
31313 (gdb) -list-features
31314 ^done,result=["feature1","feature2"]
31317 The current list of features is:
31320 @item frozen-varobjs
31321 Indicates support for the @code{-var-set-frozen} command, as well
31322 as possible presense of the @code{frozen} field in the output
31323 of @code{-varobj-create}.
31324 @item pending-breakpoints
31325 Indicates support for the @option{-f} option to the @code{-break-insert}
31328 Indicates Python scripting support, Python-based
31329 pretty-printing commands, and possible presence of the
31330 @samp{display_hint} field in the output of @code{-var-list-children}
31332 Indicates support for the @code{-thread-info} command.
31333 @item data-read-memory-bytes
31334 Indicates support for the @code{-data-read-memory-bytes} and the
31335 @code{-data-write-memory-bytes} commands.
31336 @item breakpoint-notifications
31337 Indicates that changes to breakpoints and breakpoints created via the
31338 CLI will be announced via async records.
31339 @item ada-task-info
31340 Indicates support for the @code{-ada-task-info} command.
31343 @subheading The @code{-list-target-features} Command
31344 @findex -list-target-features
31346 Returns a list of particular features that are supported by the
31347 target. Those features affect the permitted MI commands, but
31348 unlike the features reported by the @code{-list-features} command, the
31349 features depend on which target GDB is using at the moment. Whenever
31350 a target can change, due to commands such as @code{-target-select},
31351 @code{-target-attach} or @code{-exec-run}, the list of target features
31352 may change, and the frontend should obtain it again.
31356 (gdb) -list-features
31357 ^done,result=["async"]
31360 The current list of features is:
31364 Indicates that the target is capable of asynchronous command
31365 execution, which means that @value{GDBN} will accept further commands
31366 while the target is running.
31369 Indicates that the target is capable of reverse execution.
31370 @xref{Reverse Execution}, for more information.
31374 @subheading The @code{-list-thread-groups} Command
31375 @findex -list-thread-groups
31377 @subheading Synopsis
31380 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31383 Lists thread groups (@pxref{Thread groups}). When a single thread
31384 group is passed as the argument, lists the children of that group.
31385 When several thread group are passed, lists information about those
31386 thread groups. Without any parameters, lists information about all
31387 top-level thread groups.
31389 Normally, thread groups that are being debugged are reported.
31390 With the @samp{--available} option, @value{GDBN} reports thread groups
31391 available on the target.
31393 The output of this command may have either a @samp{threads} result or
31394 a @samp{groups} result. The @samp{thread} result has a list of tuples
31395 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31396 Information}). The @samp{groups} result has a list of tuples as value,
31397 each tuple describing a thread group. If top-level groups are
31398 requested (that is, no parameter is passed), or when several groups
31399 are passed, the output always has a @samp{groups} result. The format
31400 of the @samp{group} result is described below.
31402 To reduce the number of roundtrips it's possible to list thread groups
31403 together with their children, by passing the @samp{--recurse} option
31404 and the recursion depth. Presently, only recursion depth of 1 is
31405 permitted. If this option is present, then every reported thread group
31406 will also include its children, either as @samp{group} or
31407 @samp{threads} field.
31409 In general, any combination of option and parameters is permitted, with
31410 the following caveats:
31414 When a single thread group is passed, the output will typically
31415 be the @samp{threads} result. Because threads may not contain
31416 anything, the @samp{recurse} option will be ignored.
31419 When the @samp{--available} option is passed, limited information may
31420 be available. In particular, the list of threads of a process might
31421 be inaccessible. Further, specifying specific thread groups might
31422 not give any performance advantage over listing all thread groups.
31423 The frontend should assume that @samp{-list-thread-groups --available}
31424 is always an expensive operation and cache the results.
31428 The @samp{groups} result is a list of tuples, where each tuple may
31429 have the following fields:
31433 Identifier of the thread group. This field is always present.
31434 The identifier is an opaque string; frontends should not try to
31435 convert it to an integer, even though it might look like one.
31438 The type of the thread group. At present, only @samp{process} is a
31442 The target-specific process identifier. This field is only present
31443 for thread groups of type @samp{process} and only if the process exists.
31446 The number of children this thread group has. This field may be
31447 absent for an available thread group.
31450 This field has a list of tuples as value, each tuple describing a
31451 thread. It may be present if the @samp{--recurse} option is
31452 specified, and it's actually possible to obtain the threads.
31455 This field is a list of integers, each identifying a core that one
31456 thread of the group is running on. This field may be absent if
31457 such information is not available.
31460 The name of the executable file that corresponds to this thread group.
31461 The field is only present for thread groups of type @samp{process},
31462 and only if there is a corresponding executable file.
31466 @subheading Example
31470 -list-thread-groups
31471 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31472 -list-thread-groups 17
31473 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31474 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31475 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31476 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31477 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31478 -list-thread-groups --available
31479 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31480 -list-thread-groups --available --recurse 1
31481 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31482 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31483 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31484 -list-thread-groups --available --recurse 1 17 18
31485 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31486 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31487 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31491 @subheading The @code{-add-inferior} Command
31492 @findex -add-inferior
31494 @subheading Synopsis
31500 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31501 inferior is not associated with any executable. Such association may
31502 be established with the @samp{-file-exec-and-symbols} command
31503 (@pxref{GDB/MI File Commands}). The command response has a single
31504 field, @samp{thread-group}, whose value is the identifier of the
31505 thread group corresponding to the new inferior.
31507 @subheading Example
31512 ^done,thread-group="i3"
31515 @subheading The @code{-interpreter-exec} Command
31516 @findex -interpreter-exec
31518 @subheading Synopsis
31521 -interpreter-exec @var{interpreter} @var{command}
31523 @anchor{-interpreter-exec}
31525 Execute the specified @var{command} in the given @var{interpreter}.
31527 @subheading @value{GDBN} Command
31529 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31531 @subheading Example
31535 -interpreter-exec console "break main"
31536 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31537 &"During symbol reading, bad structure-type format.\n"
31538 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31543 @subheading The @code{-inferior-tty-set} Command
31544 @findex -inferior-tty-set
31546 @subheading Synopsis
31549 -inferior-tty-set /dev/pts/1
31552 Set terminal for future runs of the program being debugged.
31554 @subheading @value{GDBN} Command
31556 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31558 @subheading Example
31562 -inferior-tty-set /dev/pts/1
31567 @subheading The @code{-inferior-tty-show} Command
31568 @findex -inferior-tty-show
31570 @subheading Synopsis
31576 Show terminal for future runs of program being debugged.
31578 @subheading @value{GDBN} Command
31580 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31582 @subheading Example
31586 -inferior-tty-set /dev/pts/1
31590 ^done,inferior_tty_terminal="/dev/pts/1"
31594 @subheading The @code{-enable-timings} Command
31595 @findex -enable-timings
31597 @subheading Synopsis
31600 -enable-timings [yes | no]
31603 Toggle the printing of the wallclock, user and system times for an MI
31604 command as a field in its output. This command is to help frontend
31605 developers optimize the performance of their code. No argument is
31606 equivalent to @samp{yes}.
31608 @subheading @value{GDBN} Command
31612 @subheading Example
31620 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31621 addr="0x080484ed",func="main",file="myprog.c",
31622 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31623 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31631 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31632 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31633 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31634 fullname="/home/nickrob/myprog.c",line="73"@}
31639 @chapter @value{GDBN} Annotations
31641 This chapter describes annotations in @value{GDBN}. Annotations were
31642 designed to interface @value{GDBN} to graphical user interfaces or other
31643 similar programs which want to interact with @value{GDBN} at a
31644 relatively high level.
31646 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31650 This is Edition @value{EDITION}, @value{DATE}.
31654 * Annotations Overview:: What annotations are; the general syntax.
31655 * Server Prefix:: Issuing a command without affecting user state.
31656 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31657 * Errors:: Annotations for error messages.
31658 * Invalidation:: Some annotations describe things now invalid.
31659 * Annotations for Running::
31660 Whether the program is running, how it stopped, etc.
31661 * Source Annotations:: Annotations describing source code.
31664 @node Annotations Overview
31665 @section What is an Annotation?
31666 @cindex annotations
31668 Annotations start with a newline character, two @samp{control-z}
31669 characters, and the name of the annotation. If there is no additional
31670 information associated with this annotation, the name of the annotation
31671 is followed immediately by a newline. If there is additional
31672 information, the name of the annotation is followed by a space, the
31673 additional information, and a newline. The additional information
31674 cannot contain newline characters.
31676 Any output not beginning with a newline and two @samp{control-z}
31677 characters denotes literal output from @value{GDBN}. Currently there is
31678 no need for @value{GDBN} to output a newline followed by two
31679 @samp{control-z} characters, but if there was such a need, the
31680 annotations could be extended with an @samp{escape} annotation which
31681 means those three characters as output.
31683 The annotation @var{level}, which is specified using the
31684 @option{--annotate} command line option (@pxref{Mode Options}), controls
31685 how much information @value{GDBN} prints together with its prompt,
31686 values of expressions, source lines, and other types of output. Level 0
31687 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31688 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31689 for programs that control @value{GDBN}, and level 2 annotations have
31690 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31691 Interface, annotate, GDB's Obsolete Annotations}).
31694 @kindex set annotate
31695 @item set annotate @var{level}
31696 The @value{GDBN} command @code{set annotate} sets the level of
31697 annotations to the specified @var{level}.
31699 @item show annotate
31700 @kindex show annotate
31701 Show the current annotation level.
31704 This chapter describes level 3 annotations.
31706 A simple example of starting up @value{GDBN} with annotations is:
31709 $ @kbd{gdb --annotate=3}
31711 Copyright 2003 Free Software Foundation, Inc.
31712 GDB is free software, covered by the GNU General Public License,
31713 and you are welcome to change it and/or distribute copies of it
31714 under certain conditions.
31715 Type "show copying" to see the conditions.
31716 There is absolutely no warranty for GDB. Type "show warranty"
31718 This GDB was configured as "i386-pc-linux-gnu"
31729 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31730 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31731 denotes a @samp{control-z} character) are annotations; the rest is
31732 output from @value{GDBN}.
31734 @node Server Prefix
31735 @section The Server Prefix
31736 @cindex server prefix
31738 If you prefix a command with @samp{server } then it will not affect
31739 the command history, nor will it affect @value{GDBN}'s notion of which
31740 command to repeat if @key{RET} is pressed on a line by itself. This
31741 means that commands can be run behind a user's back by a front-end in
31742 a transparent manner.
31744 The @code{server } prefix does not affect the recording of values into
31745 the value history; to print a value without recording it into the
31746 value history, use the @code{output} command instead of the
31747 @code{print} command.
31749 Using this prefix also disables confirmation requests
31750 (@pxref{confirmation requests}).
31753 @section Annotation for @value{GDBN} Input
31755 @cindex annotations for prompts
31756 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31757 to know when to send output, when the output from a given command is
31760 Different kinds of input each have a different @dfn{input type}. Each
31761 input type has three annotations: a @code{pre-} annotation, which
31762 denotes the beginning of any prompt which is being output, a plain
31763 annotation, which denotes the end of the prompt, and then a @code{post-}
31764 annotation which denotes the end of any echo which may (or may not) be
31765 associated with the input. For example, the @code{prompt} input type
31766 features the following annotations:
31774 The input types are
31777 @findex pre-prompt annotation
31778 @findex prompt annotation
31779 @findex post-prompt annotation
31781 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31783 @findex pre-commands annotation
31784 @findex commands annotation
31785 @findex post-commands annotation
31787 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31788 command. The annotations are repeated for each command which is input.
31790 @findex pre-overload-choice annotation
31791 @findex overload-choice annotation
31792 @findex post-overload-choice annotation
31793 @item overload-choice
31794 When @value{GDBN} wants the user to select between various overloaded functions.
31796 @findex pre-query annotation
31797 @findex query annotation
31798 @findex post-query annotation
31800 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31802 @findex pre-prompt-for-continue annotation
31803 @findex prompt-for-continue annotation
31804 @findex post-prompt-for-continue annotation
31805 @item prompt-for-continue
31806 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31807 expect this to work well; instead use @code{set height 0} to disable
31808 prompting. This is because the counting of lines is buggy in the
31809 presence of annotations.
31814 @cindex annotations for errors, warnings and interrupts
31816 @findex quit annotation
31821 This annotation occurs right before @value{GDBN} responds to an interrupt.
31823 @findex error annotation
31828 This annotation occurs right before @value{GDBN} responds to an error.
31830 Quit and error annotations indicate that any annotations which @value{GDBN} was
31831 in the middle of may end abruptly. For example, if a
31832 @code{value-history-begin} annotation is followed by a @code{error}, one
31833 cannot expect to receive the matching @code{value-history-end}. One
31834 cannot expect not to receive it either, however; an error annotation
31835 does not necessarily mean that @value{GDBN} is immediately returning all the way
31838 @findex error-begin annotation
31839 A quit or error annotation may be preceded by
31845 Any output between that and the quit or error annotation is the error
31848 Warning messages are not yet annotated.
31849 @c If we want to change that, need to fix warning(), type_error(),
31850 @c range_error(), and possibly other places.
31853 @section Invalidation Notices
31855 @cindex annotations for invalidation messages
31856 The following annotations say that certain pieces of state may have
31860 @findex frames-invalid annotation
31861 @item ^Z^Zframes-invalid
31863 The frames (for example, output from the @code{backtrace} command) may
31866 @findex breakpoints-invalid annotation
31867 @item ^Z^Zbreakpoints-invalid
31869 The breakpoints may have changed. For example, the user just added or
31870 deleted a breakpoint.
31873 @node Annotations for Running
31874 @section Running the Program
31875 @cindex annotations for running programs
31877 @findex starting annotation
31878 @findex stopping annotation
31879 When the program starts executing due to a @value{GDBN} command such as
31880 @code{step} or @code{continue},
31886 is output. When the program stops,
31892 is output. Before the @code{stopped} annotation, a variety of
31893 annotations describe how the program stopped.
31896 @findex exited annotation
31897 @item ^Z^Zexited @var{exit-status}
31898 The program exited, and @var{exit-status} is the exit status (zero for
31899 successful exit, otherwise nonzero).
31901 @findex signalled annotation
31902 @findex signal-name annotation
31903 @findex signal-name-end annotation
31904 @findex signal-string annotation
31905 @findex signal-string-end annotation
31906 @item ^Z^Zsignalled
31907 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31908 annotation continues:
31914 ^Z^Zsignal-name-end
31918 ^Z^Zsignal-string-end
31923 where @var{name} is the name of the signal, such as @code{SIGILL} or
31924 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31925 as @code{Illegal Instruction} or @code{Segmentation fault}.
31926 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31927 user's benefit and have no particular format.
31929 @findex signal annotation
31931 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31932 just saying that the program received the signal, not that it was
31933 terminated with it.
31935 @findex breakpoint annotation
31936 @item ^Z^Zbreakpoint @var{number}
31937 The program hit breakpoint number @var{number}.
31939 @findex watchpoint annotation
31940 @item ^Z^Zwatchpoint @var{number}
31941 The program hit watchpoint number @var{number}.
31944 @node Source Annotations
31945 @section Displaying Source
31946 @cindex annotations for source display
31948 @findex source annotation
31949 The following annotation is used instead of displaying source code:
31952 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31955 where @var{filename} is an absolute file name indicating which source
31956 file, @var{line} is the line number within that file (where 1 is the
31957 first line in the file), @var{character} is the character position
31958 within the file (where 0 is the first character in the file) (for most
31959 debug formats this will necessarily point to the beginning of a line),
31960 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31961 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31962 @var{addr} is the address in the target program associated with the
31963 source which is being displayed. @var{addr} is in the form @samp{0x}
31964 followed by one or more lowercase hex digits (note that this does not
31965 depend on the language).
31967 @node JIT Interface
31968 @chapter JIT Compilation Interface
31969 @cindex just-in-time compilation
31970 @cindex JIT compilation interface
31972 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31973 interface. A JIT compiler is a program or library that generates native
31974 executable code at runtime and executes it, usually in order to achieve good
31975 performance while maintaining platform independence.
31977 Programs that use JIT compilation are normally difficult to debug because
31978 portions of their code are generated at runtime, instead of being loaded from
31979 object files, which is where @value{GDBN} normally finds the program's symbols
31980 and debug information. In order to debug programs that use JIT compilation,
31981 @value{GDBN} has an interface that allows the program to register in-memory
31982 symbol files with @value{GDBN} at runtime.
31984 If you are using @value{GDBN} to debug a program that uses this interface, then
31985 it should work transparently so long as you have not stripped the binary. If
31986 you are developing a JIT compiler, then the interface is documented in the rest
31987 of this chapter. At this time, the only known client of this interface is the
31990 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31991 JIT compiler communicates with @value{GDBN} by writing data into a global
31992 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31993 attaches, it reads a linked list of symbol files from the global variable to
31994 find existing code, and puts a breakpoint in the function so that it can find
31995 out about additional code.
31998 * Declarations:: Relevant C struct declarations
31999 * Registering Code:: Steps to register code
32000 * Unregistering Code:: Steps to unregister code
32001 * Custom Debug Info:: Emit debug information in a custom format
32005 @section JIT Declarations
32007 These are the relevant struct declarations that a C program should include to
32008 implement the interface:
32018 struct jit_code_entry
32020 struct jit_code_entry *next_entry;
32021 struct jit_code_entry *prev_entry;
32022 const char *symfile_addr;
32023 uint64_t symfile_size;
32026 struct jit_descriptor
32029 /* This type should be jit_actions_t, but we use uint32_t
32030 to be explicit about the bitwidth. */
32031 uint32_t action_flag;
32032 struct jit_code_entry *relevant_entry;
32033 struct jit_code_entry *first_entry;
32036 /* GDB puts a breakpoint in this function. */
32037 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32039 /* Make sure to specify the version statically, because the
32040 debugger may check the version before we can set it. */
32041 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32044 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32045 modifications to this global data properly, which can easily be done by putting
32046 a global mutex around modifications to these structures.
32048 @node Registering Code
32049 @section Registering Code
32051 To register code with @value{GDBN}, the JIT should follow this protocol:
32055 Generate an object file in memory with symbols and other desired debug
32056 information. The file must include the virtual addresses of the sections.
32059 Create a code entry for the file, which gives the start and size of the symbol
32063 Add it to the linked list in the JIT descriptor.
32066 Point the relevant_entry field of the descriptor at the entry.
32069 Set @code{action_flag} to @code{JIT_REGISTER} and call
32070 @code{__jit_debug_register_code}.
32073 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32074 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32075 new code. However, the linked list must still be maintained in order to allow
32076 @value{GDBN} to attach to a running process and still find the symbol files.
32078 @node Unregistering Code
32079 @section Unregistering Code
32081 If code is freed, then the JIT should use the following protocol:
32085 Remove the code entry corresponding to the code from the linked list.
32088 Point the @code{relevant_entry} field of the descriptor at the code entry.
32091 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32092 @code{__jit_debug_register_code}.
32095 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32096 and the JIT will leak the memory used for the associated symbol files.
32098 @node Custom Debug Info
32099 @section Custom Debug Info
32100 @cindex custom JIT debug info
32101 @cindex JIT debug info reader
32103 Generating debug information in platform-native file formats (like ELF
32104 or COFF) may be an overkill for JIT compilers; especially if all the
32105 debug info is used for is displaying a meaningful backtrace. The
32106 issue can be resolved by having the JIT writers decide on a debug info
32107 format and also provide a reader that parses the debug info generated
32108 by the JIT compiler. This section gives a brief overview on writing
32109 such a parser. More specific details can be found in the source file
32110 @file{gdb/jit-reader.in}, which is also installed as a header at
32111 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32113 The reader is implemented as a shared object (so this functionality is
32114 not available on platforms which don't allow loading shared objects at
32115 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32116 @code{jit-reader-unload} are provided, to be used to load and unload
32117 the readers from a preconfigured directory. Once loaded, the shared
32118 object is used the parse the debug information emitted by the JIT
32122 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32123 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32126 @node Using JIT Debug Info Readers
32127 @subsection Using JIT Debug Info Readers
32128 @kindex jit-reader-load
32129 @kindex jit-reader-unload
32131 Readers can be loaded and unloaded using the @code{jit-reader-load}
32132 and @code{jit-reader-unload} commands.
32135 @item jit-reader-load @var{reader-name}
32136 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32137 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32138 @var{libdir} is the system library directory, usually
32139 @file{/usr/local/lib}. Only one reader can be active at a time;
32140 trying to load a second reader when one is already loaded will result
32141 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32142 first unloading the current one using @code{jit-reader-load} and then
32143 invoking @code{jit-reader-load}.
32145 @item jit-reader-unload
32146 Unload the currently loaded JIT reader.
32150 @node Writing JIT Debug Info Readers
32151 @subsection Writing JIT Debug Info Readers
32152 @cindex writing JIT debug info readers
32154 As mentioned, a reader is essentially a shared object conforming to a
32155 certain ABI. This ABI is described in @file{jit-reader.h}.
32157 @file{jit-reader.h} defines the structures, macros and functions
32158 required to write a reader. It is installed (along with
32159 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32160 the system include directory.
32162 Readers need to be released under a GPL compatible license. A reader
32163 can be declared as released under such a license by placing the macro
32164 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32166 The entry point for readers is the symbol @code{gdb_init_reader},
32167 which is expected to be a function with the prototype
32169 @findex gdb_init_reader
32171 extern struct gdb_reader_funcs *gdb_init_reader (void);
32174 @cindex @code{struct gdb_reader_funcs}
32176 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32177 functions. These functions are executed to read the debug info
32178 generated by the JIT compiler (@code{read}), to unwind stack frames
32179 (@code{unwind}) and to create canonical frame IDs
32180 (@code{get_Frame_id}). It also has a callback that is called when the
32181 reader is being unloaded (@code{destroy}). The struct looks like this
32184 struct gdb_reader_funcs
32186 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32187 int reader_version;
32189 /* For use by the reader. */
32192 gdb_read_debug_info *read;
32193 gdb_unwind_frame *unwind;
32194 gdb_get_frame_id *get_frame_id;
32195 gdb_destroy_reader *destroy;
32199 @cindex @code{struct gdb_symbol_callbacks}
32200 @cindex @code{struct gdb_unwind_callbacks}
32202 The callbacks are provided with another set of callbacks by
32203 @value{GDBN} to do their job. For @code{read}, these callbacks are
32204 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32205 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32206 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32207 files and new symbol tables inside those object files. @code{struct
32208 gdb_unwind_callbacks} has callbacks to read registers off the current
32209 frame and to write out the values of the registers in the previous
32210 frame. Both have a callback (@code{target_read}) to read bytes off the
32211 target's address space.
32214 @chapter Reporting Bugs in @value{GDBN}
32215 @cindex bugs in @value{GDBN}
32216 @cindex reporting bugs in @value{GDBN}
32218 Your bug reports play an essential role in making @value{GDBN} reliable.
32220 Reporting a bug may help you by bringing a solution to your problem, or it
32221 may not. But in any case the principal function of a bug report is to help
32222 the entire community by making the next version of @value{GDBN} work better. Bug
32223 reports are your contribution to the maintenance of @value{GDBN}.
32225 In order for a bug report to serve its purpose, you must include the
32226 information that enables us to fix the bug.
32229 * Bug Criteria:: Have you found a bug?
32230 * Bug Reporting:: How to report bugs
32234 @section Have You Found a Bug?
32235 @cindex bug criteria
32237 If you are not sure whether you have found a bug, here are some guidelines:
32240 @cindex fatal signal
32241 @cindex debugger crash
32242 @cindex crash of debugger
32244 If the debugger gets a fatal signal, for any input whatever, that is a
32245 @value{GDBN} bug. Reliable debuggers never crash.
32247 @cindex error on valid input
32249 If @value{GDBN} produces an error message for valid input, that is a
32250 bug. (Note that if you're cross debugging, the problem may also be
32251 somewhere in the connection to the target.)
32253 @cindex invalid input
32255 If @value{GDBN} does not produce an error message for invalid input,
32256 that is a bug. However, you should note that your idea of
32257 ``invalid input'' might be our idea of ``an extension'' or ``support
32258 for traditional practice''.
32261 If you are an experienced user of debugging tools, your suggestions
32262 for improvement of @value{GDBN} are welcome in any case.
32265 @node Bug Reporting
32266 @section How to Report Bugs
32267 @cindex bug reports
32268 @cindex @value{GDBN} bugs, reporting
32270 A number of companies and individuals offer support for @sc{gnu} products.
32271 If you obtained @value{GDBN} from a support organization, we recommend you
32272 contact that organization first.
32274 You can find contact information for many support companies and
32275 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32277 @c should add a web page ref...
32280 @ifset BUGURL_DEFAULT
32281 In any event, we also recommend that you submit bug reports for
32282 @value{GDBN}. The preferred method is to submit them directly using
32283 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32284 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32287 @strong{Do not send bug reports to @samp{info-gdb}, or to
32288 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32289 not want to receive bug reports. Those that do have arranged to receive
32292 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32293 serves as a repeater. The mailing list and the newsgroup carry exactly
32294 the same messages. Often people think of posting bug reports to the
32295 newsgroup instead of mailing them. This appears to work, but it has one
32296 problem which can be crucial: a newsgroup posting often lacks a mail
32297 path back to the sender. Thus, if we need to ask for more information,
32298 we may be unable to reach you. For this reason, it is better to send
32299 bug reports to the mailing list.
32301 @ifclear BUGURL_DEFAULT
32302 In any event, we also recommend that you submit bug reports for
32303 @value{GDBN} to @value{BUGURL}.
32307 The fundamental principle of reporting bugs usefully is this:
32308 @strong{report all the facts}. If you are not sure whether to state a
32309 fact or leave it out, state it!
32311 Often people omit facts because they think they know what causes the
32312 problem and assume that some details do not matter. Thus, you might
32313 assume that the name of the variable you use in an example does not matter.
32314 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32315 stray memory reference which happens to fetch from the location where that
32316 name is stored in memory; perhaps, if the name were different, the contents
32317 of that location would fool the debugger into doing the right thing despite
32318 the bug. Play it safe and give a specific, complete example. That is the
32319 easiest thing for you to do, and the most helpful.
32321 Keep in mind that the purpose of a bug report is to enable us to fix the
32322 bug. It may be that the bug has been reported previously, but neither
32323 you nor we can know that unless your bug report is complete and
32326 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32327 bell?'' Those bug reports are useless, and we urge everyone to
32328 @emph{refuse to respond to them} except to chide the sender to report
32331 To enable us to fix the bug, you should include all these things:
32335 The version of @value{GDBN}. @value{GDBN} announces it if you start
32336 with no arguments; you can also print it at any time using @code{show
32339 Without this, we will not know whether there is any point in looking for
32340 the bug in the current version of @value{GDBN}.
32343 The type of machine you are using, and the operating system name and
32347 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32348 ``@value{GCC}--2.8.1''.
32351 What compiler (and its version) was used to compile the program you are
32352 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32353 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32354 to get this information; for other compilers, see the documentation for
32358 The command arguments you gave the compiler to compile your example and
32359 observe the bug. For example, did you use @samp{-O}? To guarantee
32360 you will not omit something important, list them all. A copy of the
32361 Makefile (or the output from make) is sufficient.
32363 If we were to try to guess the arguments, we would probably guess wrong
32364 and then we might not encounter the bug.
32367 A complete input script, and all necessary source files, that will
32371 A description of what behavior you observe that you believe is
32372 incorrect. For example, ``It gets a fatal signal.''
32374 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32375 will certainly notice it. But if the bug is incorrect output, we might
32376 not notice unless it is glaringly wrong. You might as well not give us
32377 a chance to make a mistake.
32379 Even if the problem you experience is a fatal signal, you should still
32380 say so explicitly. Suppose something strange is going on, such as, your
32381 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32382 the C library on your system. (This has happened!) Your copy might
32383 crash and ours would not. If you told us to expect a crash, then when
32384 ours fails to crash, we would know that the bug was not happening for
32385 us. If you had not told us to expect a crash, then we would not be able
32386 to draw any conclusion from our observations.
32389 @cindex recording a session script
32390 To collect all this information, you can use a session recording program
32391 such as @command{script}, which is available on many Unix systems.
32392 Just run your @value{GDBN} session inside @command{script} and then
32393 include the @file{typescript} file with your bug report.
32395 Another way to record a @value{GDBN} session is to run @value{GDBN}
32396 inside Emacs and then save the entire buffer to a file.
32399 If you wish to suggest changes to the @value{GDBN} source, send us context
32400 diffs. If you even discuss something in the @value{GDBN} source, refer to
32401 it by context, not by line number.
32403 The line numbers in our development sources will not match those in your
32404 sources. Your line numbers would convey no useful information to us.
32408 Here are some things that are not necessary:
32412 A description of the envelope of the bug.
32414 Often people who encounter a bug spend a lot of time investigating
32415 which changes to the input file will make the bug go away and which
32416 changes will not affect it.
32418 This is often time consuming and not very useful, because the way we
32419 will find the bug is by running a single example under the debugger
32420 with breakpoints, not by pure deduction from a series of examples.
32421 We recommend that you save your time for something else.
32423 Of course, if you can find a simpler example to report @emph{instead}
32424 of the original one, that is a convenience for us. Errors in the
32425 output will be easier to spot, running under the debugger will take
32426 less time, and so on.
32428 However, simplification is not vital; if you do not want to do this,
32429 report the bug anyway and send us the entire test case you used.
32432 A patch for the bug.
32434 A patch for the bug does help us if it is a good one. But do not omit
32435 the necessary information, such as the test case, on the assumption that
32436 a patch is all we need. We might see problems with your patch and decide
32437 to fix the problem another way, or we might not understand it at all.
32439 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32440 construct an example that will make the program follow a certain path
32441 through the code. If you do not send us the example, we will not be able
32442 to construct one, so we will not be able to verify that the bug is fixed.
32444 And if we cannot understand what bug you are trying to fix, or why your
32445 patch should be an improvement, we will not install it. A test case will
32446 help us to understand.
32449 A guess about what the bug is or what it depends on.
32451 Such guesses are usually wrong. Even we cannot guess right about such
32452 things without first using the debugger to find the facts.
32455 @c The readline documentation is distributed with the readline code
32456 @c and consists of the two following files:
32459 @c Use -I with makeinfo to point to the appropriate directory,
32460 @c environment var TEXINPUTS with TeX.
32461 @ifclear SYSTEM_READLINE
32462 @include rluser.texi
32463 @include hsuser.texi
32467 @appendix In Memoriam
32469 The @value{GDBN} project mourns the loss of the following long-time
32474 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32475 to Free Software in general. Outside of @value{GDBN}, he was known in
32476 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32478 @item Michael Snyder
32479 Michael was one of the Global Maintainers of the @value{GDBN} project,
32480 with contributions recorded as early as 1996, until 2011. In addition
32481 to his day to day participation, he was a large driving force behind
32482 adding Reverse Debugging to @value{GDBN}.
32485 Beyond their technical contributions to the project, they were also
32486 enjoyable members of the Free Software Community. We will miss them.
32488 @node Formatting Documentation
32489 @appendix Formatting Documentation
32491 @cindex @value{GDBN} reference card
32492 @cindex reference card
32493 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32494 for printing with PostScript or Ghostscript, in the @file{gdb}
32495 subdirectory of the main source directory@footnote{In
32496 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32497 release.}. If you can use PostScript or Ghostscript with your printer,
32498 you can print the reference card immediately with @file{refcard.ps}.
32500 The release also includes the source for the reference card. You
32501 can format it, using @TeX{}, by typing:
32507 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32508 mode on US ``letter'' size paper;
32509 that is, on a sheet 11 inches wide by 8.5 inches
32510 high. You will need to specify this form of printing as an option to
32511 your @sc{dvi} output program.
32513 @cindex documentation
32515 All the documentation for @value{GDBN} comes as part of the machine-readable
32516 distribution. The documentation is written in Texinfo format, which is
32517 a documentation system that uses a single source file to produce both
32518 on-line information and a printed manual. You can use one of the Info
32519 formatting commands to create the on-line version of the documentation
32520 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32522 @value{GDBN} includes an already formatted copy of the on-line Info
32523 version of this manual in the @file{gdb} subdirectory. The main Info
32524 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32525 subordinate files matching @samp{gdb.info*} in the same directory. If
32526 necessary, you can print out these files, or read them with any editor;
32527 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32528 Emacs or the standalone @code{info} program, available as part of the
32529 @sc{gnu} Texinfo distribution.
32531 If you want to format these Info files yourself, you need one of the
32532 Info formatting programs, such as @code{texinfo-format-buffer} or
32535 If you have @code{makeinfo} installed, and are in the top level
32536 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32537 version @value{GDBVN}), you can make the Info file by typing:
32544 If you want to typeset and print copies of this manual, you need @TeX{},
32545 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32546 Texinfo definitions file.
32548 @TeX{} is a typesetting program; it does not print files directly, but
32549 produces output files called @sc{dvi} files. To print a typeset
32550 document, you need a program to print @sc{dvi} files. If your system
32551 has @TeX{} installed, chances are it has such a program. The precise
32552 command to use depends on your system; @kbd{lpr -d} is common; another
32553 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32554 require a file name without any extension or a @samp{.dvi} extension.
32556 @TeX{} also requires a macro definitions file called
32557 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32558 written in Texinfo format. On its own, @TeX{} cannot either read or
32559 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32560 and is located in the @file{gdb-@var{version-number}/texinfo}
32563 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32564 typeset and print this manual. First switch to the @file{gdb}
32565 subdirectory of the main source directory (for example, to
32566 @file{gdb-@value{GDBVN}/gdb}) and type:
32572 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32574 @node Installing GDB
32575 @appendix Installing @value{GDBN}
32576 @cindex installation
32579 * Requirements:: Requirements for building @value{GDBN}
32580 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32581 * Separate Objdir:: Compiling @value{GDBN} in another directory
32582 * Config Names:: Specifying names for hosts and targets
32583 * Configure Options:: Summary of options for configure
32584 * System-wide configuration:: Having a system-wide init file
32588 @section Requirements for Building @value{GDBN}
32589 @cindex building @value{GDBN}, requirements for
32591 Building @value{GDBN} requires various tools and packages to be available.
32592 Other packages will be used only if they are found.
32594 @heading Tools/Packages Necessary for Building @value{GDBN}
32596 @item ISO C90 compiler
32597 @value{GDBN} is written in ISO C90. It should be buildable with any
32598 working C90 compiler, e.g.@: GCC.
32602 @heading Tools/Packages Optional for Building @value{GDBN}
32606 @value{GDBN} can use the Expat XML parsing library. This library may be
32607 included with your operating system distribution; if it is not, you
32608 can get the latest version from @url{http://expat.sourceforge.net}.
32609 The @file{configure} script will search for this library in several
32610 standard locations; if it is installed in an unusual path, you can
32611 use the @option{--with-libexpat-prefix} option to specify its location.
32617 Remote protocol memory maps (@pxref{Memory Map Format})
32619 Target descriptions (@pxref{Target Descriptions})
32621 Remote shared library lists (@xref{Library List Format},
32622 or alternatively @pxref{Library List Format for SVR4 Targets})
32624 MS-Windows shared libraries (@pxref{Shared Libraries})
32626 Traceframe info (@pxref{Traceframe Info Format})
32630 @cindex compressed debug sections
32631 @value{GDBN} will use the @samp{zlib} library, if available, to read
32632 compressed debug sections. Some linkers, such as GNU gold, are capable
32633 of producing binaries with compressed debug sections. If @value{GDBN}
32634 is compiled with @samp{zlib}, it will be able to read the debug
32635 information in such binaries.
32637 The @samp{zlib} library is likely included with your operating system
32638 distribution; if it is not, you can get the latest version from
32639 @url{http://zlib.net}.
32642 @value{GDBN}'s features related to character sets (@pxref{Character
32643 Sets}) require a functioning @code{iconv} implementation. If you are
32644 on a GNU system, then this is provided by the GNU C Library. Some
32645 other systems also provide a working @code{iconv}.
32647 If @value{GDBN} is using the @code{iconv} program which is installed
32648 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32649 This is done with @option{--with-iconv-bin} which specifies the
32650 directory that contains the @code{iconv} program.
32652 On systems without @code{iconv}, you can install GNU Libiconv. If you
32653 have previously installed Libiconv, you can use the
32654 @option{--with-libiconv-prefix} option to configure.
32656 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32657 arrange to build Libiconv if a directory named @file{libiconv} appears
32658 in the top-most source directory. If Libiconv is built this way, and
32659 if the operating system does not provide a suitable @code{iconv}
32660 implementation, then the just-built library will automatically be used
32661 by @value{GDBN}. One easy way to set this up is to download GNU
32662 Libiconv, unpack it, and then rename the directory holding the
32663 Libiconv source code to @samp{libiconv}.
32666 @node Running Configure
32667 @section Invoking the @value{GDBN} @file{configure} Script
32668 @cindex configuring @value{GDBN}
32669 @value{GDBN} comes with a @file{configure} script that automates the process
32670 of preparing @value{GDBN} for installation; you can then use @code{make} to
32671 build the @code{gdb} program.
32673 @c irrelevant in info file; it's as current as the code it lives with.
32674 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32675 look at the @file{README} file in the sources; we may have improved the
32676 installation procedures since publishing this manual.}
32679 The @value{GDBN} distribution includes all the source code you need for
32680 @value{GDBN} in a single directory, whose name is usually composed by
32681 appending the version number to @samp{gdb}.
32683 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32684 @file{gdb-@value{GDBVN}} directory. That directory contains:
32687 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32688 script for configuring @value{GDBN} and all its supporting libraries
32690 @item gdb-@value{GDBVN}/gdb
32691 the source specific to @value{GDBN} itself
32693 @item gdb-@value{GDBVN}/bfd
32694 source for the Binary File Descriptor library
32696 @item gdb-@value{GDBVN}/include
32697 @sc{gnu} include files
32699 @item gdb-@value{GDBVN}/libiberty
32700 source for the @samp{-liberty} free software library
32702 @item gdb-@value{GDBVN}/opcodes
32703 source for the library of opcode tables and disassemblers
32705 @item gdb-@value{GDBVN}/readline
32706 source for the @sc{gnu} command-line interface
32708 @item gdb-@value{GDBVN}/glob
32709 source for the @sc{gnu} filename pattern-matching subroutine
32711 @item gdb-@value{GDBVN}/mmalloc
32712 source for the @sc{gnu} memory-mapped malloc package
32715 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32716 from the @file{gdb-@var{version-number}} source directory, which in
32717 this example is the @file{gdb-@value{GDBVN}} directory.
32719 First switch to the @file{gdb-@var{version-number}} source directory
32720 if you are not already in it; then run @file{configure}. Pass the
32721 identifier for the platform on which @value{GDBN} will run as an
32727 cd gdb-@value{GDBVN}
32728 ./configure @var{host}
32733 where @var{host} is an identifier such as @samp{sun4} or
32734 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32735 (You can often leave off @var{host}; @file{configure} tries to guess the
32736 correct value by examining your system.)
32738 Running @samp{configure @var{host}} and then running @code{make} builds the
32739 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32740 libraries, then @code{gdb} itself. The configured source files, and the
32741 binaries, are left in the corresponding source directories.
32744 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32745 system does not recognize this automatically when you run a different
32746 shell, you may need to run @code{sh} on it explicitly:
32749 sh configure @var{host}
32752 If you run @file{configure} from a directory that contains source
32753 directories for multiple libraries or programs, such as the
32754 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32756 creates configuration files for every directory level underneath (unless
32757 you tell it not to, with the @samp{--norecursion} option).
32759 You should run the @file{configure} script from the top directory in the
32760 source tree, the @file{gdb-@var{version-number}} directory. If you run
32761 @file{configure} from one of the subdirectories, you will configure only
32762 that subdirectory. That is usually not what you want. In particular,
32763 if you run the first @file{configure} from the @file{gdb} subdirectory
32764 of the @file{gdb-@var{version-number}} directory, you will omit the
32765 configuration of @file{bfd}, @file{readline}, and other sibling
32766 directories of the @file{gdb} subdirectory. This leads to build errors
32767 about missing include files such as @file{bfd/bfd.h}.
32769 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32770 However, you should make sure that the shell on your path (named by
32771 the @samp{SHELL} environment variable) is publicly readable. Remember
32772 that @value{GDBN} uses the shell to start your program---some systems refuse to
32773 let @value{GDBN} debug child processes whose programs are not readable.
32775 @node Separate Objdir
32776 @section Compiling @value{GDBN} in Another Directory
32778 If you want to run @value{GDBN} versions for several host or target machines,
32779 you need a different @code{gdb} compiled for each combination of
32780 host and target. @file{configure} is designed to make this easy by
32781 allowing you to generate each configuration in a separate subdirectory,
32782 rather than in the source directory. If your @code{make} program
32783 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32784 @code{make} in each of these directories builds the @code{gdb}
32785 program specified there.
32787 To build @code{gdb} in a separate directory, run @file{configure}
32788 with the @samp{--srcdir} option to specify where to find the source.
32789 (You also need to specify a path to find @file{configure}
32790 itself from your working directory. If the path to @file{configure}
32791 would be the same as the argument to @samp{--srcdir}, you can leave out
32792 the @samp{--srcdir} option; it is assumed.)
32794 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32795 separate directory for a Sun 4 like this:
32799 cd gdb-@value{GDBVN}
32802 ../gdb-@value{GDBVN}/configure sun4
32807 When @file{configure} builds a configuration using a remote source
32808 directory, it creates a tree for the binaries with the same structure
32809 (and using the same names) as the tree under the source directory. In
32810 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32811 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32812 @file{gdb-sun4/gdb}.
32814 Make sure that your path to the @file{configure} script has just one
32815 instance of @file{gdb} in it. If your path to @file{configure} looks
32816 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32817 one subdirectory of @value{GDBN}, not the whole package. This leads to
32818 build errors about missing include files such as @file{bfd/bfd.h}.
32820 One popular reason to build several @value{GDBN} configurations in separate
32821 directories is to configure @value{GDBN} for cross-compiling (where
32822 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32823 programs that run on another machine---the @dfn{target}).
32824 You specify a cross-debugging target by
32825 giving the @samp{--target=@var{target}} option to @file{configure}.
32827 When you run @code{make} to build a program or library, you must run
32828 it in a configured directory---whatever directory you were in when you
32829 called @file{configure} (or one of its subdirectories).
32831 The @code{Makefile} that @file{configure} generates in each source
32832 directory also runs recursively. If you type @code{make} in a source
32833 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32834 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32835 will build all the required libraries, and then build GDB.
32837 When you have multiple hosts or targets configured in separate
32838 directories, you can run @code{make} on them in parallel (for example,
32839 if they are NFS-mounted on each of the hosts); they will not interfere
32843 @section Specifying Names for Hosts and Targets
32845 The specifications used for hosts and targets in the @file{configure}
32846 script are based on a three-part naming scheme, but some short predefined
32847 aliases are also supported. The full naming scheme encodes three pieces
32848 of information in the following pattern:
32851 @var{architecture}-@var{vendor}-@var{os}
32854 For example, you can use the alias @code{sun4} as a @var{host} argument,
32855 or as the value for @var{target} in a @code{--target=@var{target}}
32856 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32858 The @file{configure} script accompanying @value{GDBN} does not provide
32859 any query facility to list all supported host and target names or
32860 aliases. @file{configure} calls the Bourne shell script
32861 @code{config.sub} to map abbreviations to full names; you can read the
32862 script, if you wish, or you can use it to test your guesses on
32863 abbreviations---for example:
32866 % sh config.sub i386-linux
32868 % sh config.sub alpha-linux
32869 alpha-unknown-linux-gnu
32870 % sh config.sub hp9k700
32872 % sh config.sub sun4
32873 sparc-sun-sunos4.1.1
32874 % sh config.sub sun3
32875 m68k-sun-sunos4.1.1
32876 % sh config.sub i986v
32877 Invalid configuration `i986v': machine `i986v' not recognized
32881 @code{config.sub} is also distributed in the @value{GDBN} source
32882 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32884 @node Configure Options
32885 @section @file{configure} Options
32887 Here is a summary of the @file{configure} options and arguments that
32888 are most often useful for building @value{GDBN}. @file{configure} also has
32889 several other options not listed here. @inforef{What Configure
32890 Does,,configure.info}, for a full explanation of @file{configure}.
32893 configure @r{[}--help@r{]}
32894 @r{[}--prefix=@var{dir}@r{]}
32895 @r{[}--exec-prefix=@var{dir}@r{]}
32896 @r{[}--srcdir=@var{dirname}@r{]}
32897 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32898 @r{[}--target=@var{target}@r{]}
32903 You may introduce options with a single @samp{-} rather than
32904 @samp{--} if you prefer; but you may abbreviate option names if you use
32909 Display a quick summary of how to invoke @file{configure}.
32911 @item --prefix=@var{dir}
32912 Configure the source to install programs and files under directory
32915 @item --exec-prefix=@var{dir}
32916 Configure the source to install programs under directory
32919 @c avoid splitting the warning from the explanation:
32921 @item --srcdir=@var{dirname}
32922 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32923 @code{make} that implements the @code{VPATH} feature.}@*
32924 Use this option to make configurations in directories separate from the
32925 @value{GDBN} source directories. Among other things, you can use this to
32926 build (or maintain) several configurations simultaneously, in separate
32927 directories. @file{configure} writes configuration-specific files in
32928 the current directory, but arranges for them to use the source in the
32929 directory @var{dirname}. @file{configure} creates directories under
32930 the working directory in parallel to the source directories below
32933 @item --norecursion
32934 Configure only the directory level where @file{configure} is executed; do not
32935 propagate configuration to subdirectories.
32937 @item --target=@var{target}
32938 Configure @value{GDBN} for cross-debugging programs running on the specified
32939 @var{target}. Without this option, @value{GDBN} is configured to debug
32940 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32942 There is no convenient way to generate a list of all available targets.
32944 @item @var{host} @dots{}
32945 Configure @value{GDBN} to run on the specified @var{host}.
32947 There is no convenient way to generate a list of all available hosts.
32950 There are many other options available as well, but they are generally
32951 needed for special purposes only.
32953 @node System-wide configuration
32954 @section System-wide configuration and settings
32955 @cindex system-wide init file
32957 @value{GDBN} can be configured to have a system-wide init file;
32958 this file will be read and executed at startup (@pxref{Startup, , What
32959 @value{GDBN} does during startup}).
32961 Here is the corresponding configure option:
32964 @item --with-system-gdbinit=@var{file}
32965 Specify that the default location of the system-wide init file is
32969 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32970 it may be subject to relocation. Two possible cases:
32974 If the default location of this init file contains @file{$prefix},
32975 it will be subject to relocation. Suppose that the configure options
32976 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32977 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32978 init file is looked for as @file{$install/etc/gdbinit} instead of
32979 @file{$prefix/etc/gdbinit}.
32982 By contrast, if the default location does not contain the prefix,
32983 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32984 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32985 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32986 wherever @value{GDBN} is installed.
32989 @node Maintenance Commands
32990 @appendix Maintenance Commands
32991 @cindex maintenance commands
32992 @cindex internal commands
32994 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32995 includes a number of commands intended for @value{GDBN} developers,
32996 that are not documented elsewhere in this manual. These commands are
32997 provided here for reference. (For commands that turn on debugging
32998 messages, see @ref{Debugging Output}.)
33001 @kindex maint agent
33002 @kindex maint agent-eval
33003 @item maint agent @var{expression}
33004 @itemx maint agent-eval @var{expression}
33005 Translate the given @var{expression} into remote agent bytecodes.
33006 This command is useful for debugging the Agent Expression mechanism
33007 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33008 expression useful for data collection, such as by tracepoints, while
33009 @samp{maint agent-eval} produces an expression that evaluates directly
33010 to a result. For instance, a collection expression for @code{globa +
33011 globb} will include bytecodes to record four bytes of memory at each
33012 of the addresses of @code{globa} and @code{globb}, while discarding
33013 the result of the addition, while an evaluation expression will do the
33014 addition and return the sum.
33016 @kindex maint info breakpoints
33017 @item @anchor{maint info breakpoints}maint info breakpoints
33018 Using the same format as @samp{info breakpoints}, display both the
33019 breakpoints you've set explicitly, and those @value{GDBN} is using for
33020 internal purposes. Internal breakpoints are shown with negative
33021 breakpoint numbers. The type column identifies what kind of breakpoint
33026 Normal, explicitly set breakpoint.
33029 Normal, explicitly set watchpoint.
33032 Internal breakpoint, used to handle correctly stepping through
33033 @code{longjmp} calls.
33035 @item longjmp resume
33036 Internal breakpoint at the target of a @code{longjmp}.
33039 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33042 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33045 Shared library events.
33049 @kindex set displaced-stepping
33050 @kindex show displaced-stepping
33051 @cindex displaced stepping support
33052 @cindex out-of-line single-stepping
33053 @item set displaced-stepping
33054 @itemx show displaced-stepping
33055 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33056 if the target supports it. Displaced stepping is a way to single-step
33057 over breakpoints without removing them from the inferior, by executing
33058 an out-of-line copy of the instruction that was originally at the
33059 breakpoint location. It is also known as out-of-line single-stepping.
33062 @item set displaced-stepping on
33063 If the target architecture supports it, @value{GDBN} will use
33064 displaced stepping to step over breakpoints.
33066 @item set displaced-stepping off
33067 @value{GDBN} will not use displaced stepping to step over breakpoints,
33068 even if such is supported by the target architecture.
33070 @cindex non-stop mode, and @samp{set displaced-stepping}
33071 @item set displaced-stepping auto
33072 This is the default mode. @value{GDBN} will use displaced stepping
33073 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33074 architecture supports displaced stepping.
33077 @kindex maint check-symtabs
33078 @item maint check-symtabs
33079 Check the consistency of psymtabs and symtabs.
33081 @kindex maint cplus first_component
33082 @item maint cplus first_component @var{name}
33083 Print the first C@t{++} class/namespace component of @var{name}.
33085 @kindex maint cplus namespace
33086 @item maint cplus namespace
33087 Print the list of possible C@t{++} namespaces.
33089 @kindex maint demangle
33090 @item maint demangle @var{name}
33091 Demangle a C@t{++} or Objective-C mangled @var{name}.
33093 @kindex maint deprecate
33094 @kindex maint undeprecate
33095 @cindex deprecated commands
33096 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33097 @itemx maint undeprecate @var{command}
33098 Deprecate or undeprecate the named @var{command}. Deprecated commands
33099 cause @value{GDBN} to issue a warning when you use them. The optional
33100 argument @var{replacement} says which newer command should be used in
33101 favor of the deprecated one; if it is given, @value{GDBN} will mention
33102 the replacement as part of the warning.
33104 @kindex maint dump-me
33105 @item maint dump-me
33106 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33107 Cause a fatal signal in the debugger and force it to dump its core.
33108 This is supported only on systems which support aborting a program
33109 with the @code{SIGQUIT} signal.
33111 @kindex maint internal-error
33112 @kindex maint internal-warning
33113 @item maint internal-error @r{[}@var{message-text}@r{]}
33114 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33115 Cause @value{GDBN} to call the internal function @code{internal_error}
33116 or @code{internal_warning} and hence behave as though an internal error
33117 or internal warning has been detected. In addition to reporting the
33118 internal problem, these functions give the user the opportunity to
33119 either quit @value{GDBN} or create a core file of the current
33120 @value{GDBN} session.
33122 These commands take an optional parameter @var{message-text} that is
33123 used as the text of the error or warning message.
33125 Here's an example of using @code{internal-error}:
33128 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33129 @dots{}/maint.c:121: internal-error: testing, 1, 2
33130 A problem internal to GDB has been detected. Further
33131 debugging may prove unreliable.
33132 Quit this debugging session? (y or n) @kbd{n}
33133 Create a core file? (y or n) @kbd{n}
33137 @cindex @value{GDBN} internal error
33138 @cindex internal errors, control of @value{GDBN} behavior
33140 @kindex maint set internal-error
33141 @kindex maint show internal-error
33142 @kindex maint set internal-warning
33143 @kindex maint show internal-warning
33144 @item maint set internal-error @var{action} [ask|yes|no]
33145 @itemx maint show internal-error @var{action}
33146 @itemx maint set internal-warning @var{action} [ask|yes|no]
33147 @itemx maint show internal-warning @var{action}
33148 When @value{GDBN} reports an internal problem (error or warning) it
33149 gives the user the opportunity to both quit @value{GDBN} and create a
33150 core file of the current @value{GDBN} session. These commands let you
33151 override the default behaviour for each particular @var{action},
33152 described in the table below.
33156 You can specify that @value{GDBN} should always (yes) or never (no)
33157 quit. The default is to ask the user what to do.
33160 You can specify that @value{GDBN} should always (yes) or never (no)
33161 create a core file. The default is to ask the user what to do.
33164 @kindex maint packet
33165 @item maint packet @var{text}
33166 If @value{GDBN} is talking to an inferior via the serial protocol,
33167 then this command sends the string @var{text} to the inferior, and
33168 displays the response packet. @value{GDBN} supplies the initial
33169 @samp{$} character, the terminating @samp{#} character, and the
33172 @kindex maint print architecture
33173 @item maint print architecture @r{[}@var{file}@r{]}
33174 Print the entire architecture configuration. The optional argument
33175 @var{file} names the file where the output goes.
33177 @kindex maint print c-tdesc
33178 @item maint print c-tdesc
33179 Print the current target description (@pxref{Target Descriptions}) as
33180 a C source file. The created source file can be used in @value{GDBN}
33181 when an XML parser is not available to parse the description.
33183 @kindex maint print dummy-frames
33184 @item maint print dummy-frames
33185 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33188 (@value{GDBP}) @kbd{b add}
33190 (@value{GDBP}) @kbd{print add(2,3)}
33191 Breakpoint 2, add (a=2, b=3) at @dots{}
33193 The program being debugged stopped while in a function called from GDB.
33195 (@value{GDBP}) @kbd{maint print dummy-frames}
33196 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33197 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33198 call_lo=0x01014000 call_hi=0x01014001
33202 Takes an optional file parameter.
33204 @kindex maint print registers
33205 @kindex maint print raw-registers
33206 @kindex maint print cooked-registers
33207 @kindex maint print register-groups
33208 @kindex maint print remote-registers
33209 @item maint print registers @r{[}@var{file}@r{]}
33210 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33211 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33212 @itemx maint print register-groups @r{[}@var{file}@r{]}
33213 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33214 Print @value{GDBN}'s internal register data structures.
33216 The command @code{maint print raw-registers} includes the contents of
33217 the raw register cache; the command @code{maint print
33218 cooked-registers} includes the (cooked) value of all registers,
33219 including registers which aren't available on the target nor visible
33220 to user; the command @code{maint print register-groups} includes the
33221 groups that each register is a member of; and the command @code{maint
33222 print remote-registers} includes the remote target's register numbers
33223 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33224 @value{GDBN} Internals}.
33226 These commands take an optional parameter, a file name to which to
33227 write the information.
33229 @kindex maint print reggroups
33230 @item maint print reggroups @r{[}@var{file}@r{]}
33231 Print @value{GDBN}'s internal register group data structures. The
33232 optional argument @var{file} tells to what file to write the
33235 The register groups info looks like this:
33238 (@value{GDBP}) @kbd{maint print reggroups}
33251 This command forces @value{GDBN} to flush its internal register cache.
33253 @kindex maint print objfiles
33254 @cindex info for known object files
33255 @item maint print objfiles
33256 Print a dump of all known object files. For each object file, this
33257 command prints its name, address in memory, and all of its psymtabs
33260 @kindex maint print section-scripts
33261 @cindex info for known .debug_gdb_scripts-loaded scripts
33262 @item maint print section-scripts [@var{regexp}]
33263 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33264 If @var{regexp} is specified, only print scripts loaded by object files
33265 matching @var{regexp}.
33266 For each script, this command prints its name as specified in the objfile,
33267 and the full path if known.
33268 @xref{.debug_gdb_scripts section}.
33270 @kindex maint print statistics
33271 @cindex bcache statistics
33272 @item maint print statistics
33273 This command prints, for each object file in the program, various data
33274 about that object file followed by the byte cache (@dfn{bcache})
33275 statistics for the object file. The objfile data includes the number
33276 of minimal, partial, full, and stabs symbols, the number of types
33277 defined by the objfile, the number of as yet unexpanded psym tables,
33278 the number of line tables and string tables, and the amount of memory
33279 used by the various tables. The bcache statistics include the counts,
33280 sizes, and counts of duplicates of all and unique objects, max,
33281 average, and median entry size, total memory used and its overhead and
33282 savings, and various measures of the hash table size and chain
33285 @kindex maint print target-stack
33286 @cindex target stack description
33287 @item maint print target-stack
33288 A @dfn{target} is an interface between the debugger and a particular
33289 kind of file or process. Targets can be stacked in @dfn{strata},
33290 so that more than one target can potentially respond to a request.
33291 In particular, memory accesses will walk down the stack of targets
33292 until they find a target that is interested in handling that particular
33295 This command prints a short description of each layer that was pushed on
33296 the @dfn{target stack}, starting from the top layer down to the bottom one.
33298 @kindex maint print type
33299 @cindex type chain of a data type
33300 @item maint print type @var{expr}
33301 Print the type chain for a type specified by @var{expr}. The argument
33302 can be either a type name or a symbol. If it is a symbol, the type of
33303 that symbol is described. The type chain produced by this command is
33304 a recursive definition of the data type as stored in @value{GDBN}'s
33305 data structures, including its flags and contained types.
33307 @kindex maint set dwarf2 always-disassemble
33308 @kindex maint show dwarf2 always-disassemble
33309 @item maint set dwarf2 always-disassemble
33310 @item maint show dwarf2 always-disassemble
33311 Control the behavior of @code{info address} when using DWARF debugging
33314 The default is @code{off}, which means that @value{GDBN} should try to
33315 describe a variable's location in an easily readable format. When
33316 @code{on}, @value{GDBN} will instead display the DWARF location
33317 expression in an assembly-like format. Note that some locations are
33318 too complex for @value{GDBN} to describe simply; in this case you will
33319 always see the disassembly form.
33321 Here is an example of the resulting disassembly:
33324 (gdb) info addr argc
33325 Symbol "argc" is a complex DWARF expression:
33329 For more information on these expressions, see
33330 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33332 @kindex maint set dwarf2 max-cache-age
33333 @kindex maint show dwarf2 max-cache-age
33334 @item maint set dwarf2 max-cache-age
33335 @itemx maint show dwarf2 max-cache-age
33336 Control the DWARF 2 compilation unit cache.
33338 @cindex DWARF 2 compilation units cache
33339 In object files with inter-compilation-unit references, such as those
33340 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33341 reader needs to frequently refer to previously read compilation units.
33342 This setting controls how long a compilation unit will remain in the
33343 cache if it is not referenced. A higher limit means that cached
33344 compilation units will be stored in memory longer, and more total
33345 memory will be used. Setting it to zero disables caching, which will
33346 slow down @value{GDBN} startup, but reduce memory consumption.
33348 @kindex maint set profile
33349 @kindex maint show profile
33350 @cindex profiling GDB
33351 @item maint set profile
33352 @itemx maint show profile
33353 Control profiling of @value{GDBN}.
33355 Profiling will be disabled until you use the @samp{maint set profile}
33356 command to enable it. When you enable profiling, the system will begin
33357 collecting timing and execution count data; when you disable profiling or
33358 exit @value{GDBN}, the results will be written to a log file. Remember that
33359 if you use profiling, @value{GDBN} will overwrite the profiling log file
33360 (often called @file{gmon.out}). If you have a record of important profiling
33361 data in a @file{gmon.out} file, be sure to move it to a safe location.
33363 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33364 compiled with the @samp{-pg} compiler option.
33366 @kindex maint set show-debug-regs
33367 @kindex maint show show-debug-regs
33368 @cindex hardware debug registers
33369 @item maint set show-debug-regs
33370 @itemx maint show show-debug-regs
33371 Control whether to show variables that mirror the hardware debug
33372 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33373 enabled, the debug registers values are shown when @value{GDBN} inserts or
33374 removes a hardware breakpoint or watchpoint, and when the inferior
33375 triggers a hardware-assisted breakpoint or watchpoint.
33377 @kindex maint set show-all-tib
33378 @kindex maint show show-all-tib
33379 @item maint set show-all-tib
33380 @itemx maint show show-all-tib
33381 Control whether to show all non zero areas within a 1k block starting
33382 at thread local base, when using the @samp{info w32 thread-information-block}
33385 @kindex maint space
33386 @cindex memory used by commands
33388 Control whether to display memory usage for each command. If set to a
33389 nonzero value, @value{GDBN} will display how much memory each command
33390 took, following the command's own output. This can also be requested
33391 by invoking @value{GDBN} with the @option{--statistics} command-line
33392 switch (@pxref{Mode Options}).
33395 @cindex time of command execution
33397 Control whether to display the execution time of @value{GDBN} for each command.
33398 If set to a nonzero value, @value{GDBN} will display how much time it
33399 took to execute each command, following the command's own output.
33400 Both CPU time and wallclock time are printed.
33401 Printing both is useful when trying to determine whether the cost is
33402 CPU or, e.g., disk/network, latency.
33403 Note that the CPU time printed is for @value{GDBN} only, it does not include
33404 the execution time of the inferior because there's no mechanism currently
33405 to compute how much time was spent by @value{GDBN} and how much time was
33406 spent by the program been debugged.
33407 This can also be requested by invoking @value{GDBN} with the
33408 @option{--statistics} command-line switch (@pxref{Mode Options}).
33410 @kindex maint translate-address
33411 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33412 Find the symbol stored at the location specified by the address
33413 @var{addr} and an optional section name @var{section}. If found,
33414 @value{GDBN} prints the name of the closest symbol and an offset from
33415 the symbol's location to the specified address. This is similar to
33416 the @code{info address} command (@pxref{Symbols}), except that this
33417 command also allows to find symbols in other sections.
33419 If section was not specified, the section in which the symbol was found
33420 is also printed. For dynamically linked executables, the name of
33421 executable or shared library containing the symbol is printed as well.
33425 The following command is useful for non-interactive invocations of
33426 @value{GDBN}, such as in the test suite.
33429 @item set watchdog @var{nsec}
33430 @kindex set watchdog
33431 @cindex watchdog timer
33432 @cindex timeout for commands
33433 Set the maximum number of seconds @value{GDBN} will wait for the
33434 target operation to finish. If this time expires, @value{GDBN}
33435 reports and error and the command is aborted.
33437 @item show watchdog
33438 Show the current setting of the target wait timeout.
33441 @node Remote Protocol
33442 @appendix @value{GDBN} Remote Serial Protocol
33447 * Stop Reply Packets::
33448 * General Query Packets::
33449 * Architecture-Specific Protocol Details::
33450 * Tracepoint Packets::
33451 * Host I/O Packets::
33453 * Notification Packets::
33454 * Remote Non-Stop::
33455 * Packet Acknowledgment::
33457 * File-I/O Remote Protocol Extension::
33458 * Library List Format::
33459 * Library List Format for SVR4 Targets::
33460 * Memory Map Format::
33461 * Thread List Format::
33462 * Traceframe Info Format::
33468 There may be occasions when you need to know something about the
33469 protocol---for example, if there is only one serial port to your target
33470 machine, you might want your program to do something special if it
33471 recognizes a packet meant for @value{GDBN}.
33473 In the examples below, @samp{->} and @samp{<-} are used to indicate
33474 transmitted and received data, respectively.
33476 @cindex protocol, @value{GDBN} remote serial
33477 @cindex serial protocol, @value{GDBN} remote
33478 @cindex remote serial protocol
33479 All @value{GDBN} commands and responses (other than acknowledgments
33480 and notifications, see @ref{Notification Packets}) are sent as a
33481 @var{packet}. A @var{packet} is introduced with the character
33482 @samp{$}, the actual @var{packet-data}, and the terminating character
33483 @samp{#} followed by a two-digit @var{checksum}:
33486 @code{$}@var{packet-data}@code{#}@var{checksum}
33490 @cindex checksum, for @value{GDBN} remote
33492 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33493 characters between the leading @samp{$} and the trailing @samp{#} (an
33494 eight bit unsigned checksum).
33496 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33497 specification also included an optional two-digit @var{sequence-id}:
33500 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33503 @cindex sequence-id, for @value{GDBN} remote
33505 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33506 has never output @var{sequence-id}s. Stubs that handle packets added
33507 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33509 When either the host or the target machine receives a packet, the first
33510 response expected is an acknowledgment: either @samp{+} (to indicate
33511 the package was received correctly) or @samp{-} (to request
33515 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33520 The @samp{+}/@samp{-} acknowledgments can be disabled
33521 once a connection is established.
33522 @xref{Packet Acknowledgment}, for details.
33524 The host (@value{GDBN}) sends @var{command}s, and the target (the
33525 debugging stub incorporated in your program) sends a @var{response}. In
33526 the case of step and continue @var{command}s, the response is only sent
33527 when the operation has completed, and the target has again stopped all
33528 threads in all attached processes. This is the default all-stop mode
33529 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33530 execution mode; see @ref{Remote Non-Stop}, for details.
33532 @var{packet-data} consists of a sequence of characters with the
33533 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33536 @cindex remote protocol, field separator
33537 Fields within the packet should be separated using @samp{,} @samp{;} or
33538 @samp{:}. Except where otherwise noted all numbers are represented in
33539 @sc{hex} with leading zeros suppressed.
33541 Implementors should note that prior to @value{GDBN} 5.0, the character
33542 @samp{:} could not appear as the third character in a packet (as it
33543 would potentially conflict with the @var{sequence-id}).
33545 @cindex remote protocol, binary data
33546 @anchor{Binary Data}
33547 Binary data in most packets is encoded either as two hexadecimal
33548 digits per byte of binary data. This allowed the traditional remote
33549 protocol to work over connections which were only seven-bit clean.
33550 Some packets designed more recently assume an eight-bit clean
33551 connection, and use a more efficient encoding to send and receive
33554 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33555 as an escape character. Any escaped byte is transmitted as the escape
33556 character followed by the original character XORed with @code{0x20}.
33557 For example, the byte @code{0x7d} would be transmitted as the two
33558 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33559 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33560 @samp{@}}) must always be escaped. Responses sent by the stub
33561 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33562 is not interpreted as the start of a run-length encoded sequence
33565 Response @var{data} can be run-length encoded to save space.
33566 Run-length encoding replaces runs of identical characters with one
33567 instance of the repeated character, followed by a @samp{*} and a
33568 repeat count. The repeat count is itself sent encoded, to avoid
33569 binary characters in @var{data}: a value of @var{n} is sent as
33570 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33571 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33572 code 32) for a repeat count of 3. (This is because run-length
33573 encoding starts to win for counts 3 or more.) Thus, for example,
33574 @samp{0* } is a run-length encoding of ``0000'': the space character
33575 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33578 The printable characters @samp{#} and @samp{$} or with a numeric value
33579 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33580 seven repeats (@samp{$}) can be expanded using a repeat count of only
33581 five (@samp{"}). For example, @samp{00000000} can be encoded as
33584 The error response returned for some packets includes a two character
33585 error number. That number is not well defined.
33587 @cindex empty response, for unsupported packets
33588 For any @var{command} not supported by the stub, an empty response
33589 (@samp{$#00}) should be returned. That way it is possible to extend the
33590 protocol. A newer @value{GDBN} can tell if a packet is supported based
33593 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33594 commands for register access, and the @samp{m} and @samp{M} commands
33595 for memory access. Stubs that only control single-threaded targets
33596 can implement run control with the @samp{c} (continue), and @samp{s}
33597 (step) commands. Stubs that support multi-threading targets should
33598 support the @samp{vCont} command. All other commands are optional.
33603 The following table provides a complete list of all currently defined
33604 @var{command}s and their corresponding response @var{data}.
33605 @xref{File-I/O Remote Protocol Extension}, for details about the File
33606 I/O extension of the remote protocol.
33608 Each packet's description has a template showing the packet's overall
33609 syntax, followed by an explanation of the packet's meaning. We
33610 include spaces in some of the templates for clarity; these are not
33611 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33612 separate its components. For example, a template like @samp{foo
33613 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33614 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33615 @var{baz}. @value{GDBN} does not transmit a space character between the
33616 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33619 @cindex @var{thread-id}, in remote protocol
33620 @anchor{thread-id syntax}
33621 Several packets and replies include a @var{thread-id} field to identify
33622 a thread. Normally these are positive numbers with a target-specific
33623 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33624 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33627 In addition, the remote protocol supports a multiprocess feature in
33628 which the @var{thread-id} syntax is extended to optionally include both
33629 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33630 The @var{pid} (process) and @var{tid} (thread) components each have the
33631 format described above: a positive number with target-specific
33632 interpretation formatted as a big-endian hex string, literal @samp{-1}
33633 to indicate all processes or threads (respectively), or @samp{0} to
33634 indicate an arbitrary process or thread. Specifying just a process, as
33635 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33636 error to specify all processes but a specific thread, such as
33637 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33638 for those packets and replies explicitly documented to include a process
33639 ID, rather than a @var{thread-id}.
33641 The multiprocess @var{thread-id} syntax extensions are only used if both
33642 @value{GDBN} and the stub report support for the @samp{multiprocess}
33643 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33646 Note that all packet forms beginning with an upper- or lower-case
33647 letter, other than those described here, are reserved for future use.
33649 Here are the packet descriptions.
33654 @cindex @samp{!} packet
33655 @anchor{extended mode}
33656 Enable extended mode. In extended mode, the remote server is made
33657 persistent. The @samp{R} packet is used to restart the program being
33663 The remote target both supports and has enabled extended mode.
33667 @cindex @samp{?} packet
33668 Indicate the reason the target halted. The reply is the same as for
33669 step and continue. This packet has a special interpretation when the
33670 target is in non-stop mode; see @ref{Remote Non-Stop}.
33673 @xref{Stop Reply Packets}, for the reply specifications.
33675 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33676 @cindex @samp{A} packet
33677 Initialized @code{argv[]} array passed into program. @var{arglen}
33678 specifies the number of bytes in the hex encoded byte stream
33679 @var{arg}. See @code{gdbserver} for more details.
33684 The arguments were set.
33690 @cindex @samp{b} packet
33691 (Don't use this packet; its behavior is not well-defined.)
33692 Change the serial line speed to @var{baud}.
33694 JTC: @emph{When does the transport layer state change? When it's
33695 received, or after the ACK is transmitted. In either case, there are
33696 problems if the command or the acknowledgment packet is dropped.}
33698 Stan: @emph{If people really wanted to add something like this, and get
33699 it working for the first time, they ought to modify ser-unix.c to send
33700 some kind of out-of-band message to a specially-setup stub and have the
33701 switch happen "in between" packets, so that from remote protocol's point
33702 of view, nothing actually happened.}
33704 @item B @var{addr},@var{mode}
33705 @cindex @samp{B} packet
33706 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33707 breakpoint at @var{addr}.
33709 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33710 (@pxref{insert breakpoint or watchpoint packet}).
33712 @cindex @samp{bc} packet
33715 Backward continue. Execute the target system in reverse. No parameter.
33716 @xref{Reverse Execution}, for more information.
33719 @xref{Stop Reply Packets}, for the reply specifications.
33721 @cindex @samp{bs} packet
33724 Backward single step. Execute one instruction in reverse. No parameter.
33725 @xref{Reverse Execution}, for more information.
33728 @xref{Stop Reply Packets}, for the reply specifications.
33730 @item c @r{[}@var{addr}@r{]}
33731 @cindex @samp{c} packet
33732 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33733 resume at current address.
33735 This packet is deprecated for multi-threading support. @xref{vCont
33739 @xref{Stop Reply Packets}, for the reply specifications.
33741 @item C @var{sig}@r{[};@var{addr}@r{]}
33742 @cindex @samp{C} packet
33743 Continue with signal @var{sig} (hex signal number). If
33744 @samp{;@var{addr}} is omitted, resume at same address.
33746 This packet is deprecated for multi-threading support. @xref{vCont
33750 @xref{Stop Reply Packets}, for the reply specifications.
33753 @cindex @samp{d} packet
33756 Don't use this packet; instead, define a general set packet
33757 (@pxref{General Query Packets}).
33761 @cindex @samp{D} packet
33762 The first form of the packet is used to detach @value{GDBN} from the
33763 remote system. It is sent to the remote target
33764 before @value{GDBN} disconnects via the @code{detach} command.
33766 The second form, including a process ID, is used when multiprocess
33767 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33768 detach only a specific process. The @var{pid} is specified as a
33769 big-endian hex string.
33779 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33780 @cindex @samp{F} packet
33781 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33782 This is part of the File-I/O protocol extension. @xref{File-I/O
33783 Remote Protocol Extension}, for the specification.
33786 @anchor{read registers packet}
33787 @cindex @samp{g} packet
33788 Read general registers.
33792 @item @var{XX@dots{}}
33793 Each byte of register data is described by two hex digits. The bytes
33794 with the register are transmitted in target byte order. The size of
33795 each register and their position within the @samp{g} packet are
33796 determined by the @value{GDBN} internal gdbarch functions
33797 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33798 specification of several standard @samp{g} packets is specified below.
33800 When reading registers from a trace frame (@pxref{Analyze Collected
33801 Data,,Using the Collected Data}), the stub may also return a string of
33802 literal @samp{x}'s in place of the register data digits, to indicate
33803 that the corresponding register has not been collected, thus its value
33804 is unavailable. For example, for an architecture with 4 registers of
33805 4 bytes each, the following reply indicates to @value{GDBN} that
33806 registers 0 and 2 have not been collected, while registers 1 and 3
33807 have been collected, and both have zero value:
33811 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33818 @item G @var{XX@dots{}}
33819 @cindex @samp{G} packet
33820 Write general registers. @xref{read registers packet}, for a
33821 description of the @var{XX@dots{}} data.
33831 @item H @var{op} @var{thread-id}
33832 @cindex @samp{H} packet
33833 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33834 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33835 it should be @samp{c} for step and continue operations (note that this
33836 is deprecated, supporting the @samp{vCont} command is a better
33837 option), @samp{g} for other operations. The thread designator
33838 @var{thread-id} has the format and interpretation described in
33839 @ref{thread-id syntax}.
33850 @c 'H': How restrictive (or permissive) is the thread model. If a
33851 @c thread is selected and stopped, are other threads allowed
33852 @c to continue to execute? As I mentioned above, I think the
33853 @c semantics of each command when a thread is selected must be
33854 @c described. For example:
33856 @c 'g': If the stub supports threads and a specific thread is
33857 @c selected, returns the register block from that thread;
33858 @c otherwise returns current registers.
33860 @c 'G' If the stub supports threads and a specific thread is
33861 @c selected, sets the registers of the register block of
33862 @c that thread; otherwise sets current registers.
33864 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33865 @anchor{cycle step packet}
33866 @cindex @samp{i} packet
33867 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33868 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33869 step starting at that address.
33872 @cindex @samp{I} packet
33873 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33877 @cindex @samp{k} packet
33880 FIXME: @emph{There is no description of how to operate when a specific
33881 thread context has been selected (i.e.@: does 'k' kill only that
33884 @item m @var{addr},@var{length}
33885 @cindex @samp{m} packet
33886 Read @var{length} bytes of memory starting at address @var{addr}.
33887 Note that @var{addr} may not be aligned to any particular boundary.
33889 The stub need not use any particular size or alignment when gathering
33890 data from memory for the response; even if @var{addr} is word-aligned
33891 and @var{length} is a multiple of the word size, the stub is free to
33892 use byte accesses, or not. For this reason, this packet may not be
33893 suitable for accessing memory-mapped I/O devices.
33894 @cindex alignment of remote memory accesses
33895 @cindex size of remote memory accesses
33896 @cindex memory, alignment and size of remote accesses
33900 @item @var{XX@dots{}}
33901 Memory contents; each byte is transmitted as a two-digit hexadecimal
33902 number. The reply may contain fewer bytes than requested if the
33903 server was able to read only part of the region of memory.
33908 @item M @var{addr},@var{length}:@var{XX@dots{}}
33909 @cindex @samp{M} packet
33910 Write @var{length} bytes of memory starting at address @var{addr}.
33911 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33912 hexadecimal number.
33919 for an error (this includes the case where only part of the data was
33924 @cindex @samp{p} packet
33925 Read the value of register @var{n}; @var{n} is in hex.
33926 @xref{read registers packet}, for a description of how the returned
33927 register value is encoded.
33931 @item @var{XX@dots{}}
33932 the register's value
33936 Indicating an unrecognized @var{query}.
33939 @item P @var{n@dots{}}=@var{r@dots{}}
33940 @anchor{write register packet}
33941 @cindex @samp{P} packet
33942 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33943 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33944 digits for each byte in the register (target byte order).
33954 @item q @var{name} @var{params}@dots{}
33955 @itemx Q @var{name} @var{params}@dots{}
33956 @cindex @samp{q} packet
33957 @cindex @samp{Q} packet
33958 General query (@samp{q}) and set (@samp{Q}). These packets are
33959 described fully in @ref{General Query Packets}.
33962 @cindex @samp{r} packet
33963 Reset the entire system.
33965 Don't use this packet; use the @samp{R} packet instead.
33968 @cindex @samp{R} packet
33969 Restart the program being debugged. @var{XX}, while needed, is ignored.
33970 This packet is only available in extended mode (@pxref{extended mode}).
33972 The @samp{R} packet has no reply.
33974 @item s @r{[}@var{addr}@r{]}
33975 @cindex @samp{s} packet
33976 Single step. @var{addr} is the address at which to resume. If
33977 @var{addr} is omitted, resume at same address.
33979 This packet is deprecated for multi-threading support. @xref{vCont
33983 @xref{Stop Reply Packets}, for the reply specifications.
33985 @item S @var{sig}@r{[};@var{addr}@r{]}
33986 @anchor{step with signal packet}
33987 @cindex @samp{S} packet
33988 Step with signal. This is analogous to the @samp{C} packet, but
33989 requests a single-step, rather than a normal resumption of execution.
33991 This packet is deprecated for multi-threading support. @xref{vCont
33995 @xref{Stop Reply Packets}, for the reply specifications.
33997 @item t @var{addr}:@var{PP},@var{MM}
33998 @cindex @samp{t} packet
33999 Search backwards starting at address @var{addr} for a match with pattern
34000 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34001 @var{addr} must be at least 3 digits.
34003 @item T @var{thread-id}
34004 @cindex @samp{T} packet
34005 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34010 thread is still alive
34016 Packets starting with @samp{v} are identified by a multi-letter name,
34017 up to the first @samp{;} or @samp{?} (or the end of the packet).
34019 @item vAttach;@var{pid}
34020 @cindex @samp{vAttach} packet
34021 Attach to a new process with the specified process ID @var{pid}.
34022 The process ID is a
34023 hexadecimal integer identifying the process. In all-stop mode, all
34024 threads in the attached process are stopped; in non-stop mode, it may be
34025 attached without being stopped if that is supported by the target.
34027 @c In non-stop mode, on a successful vAttach, the stub should set the
34028 @c current thread to a thread of the newly-attached process. After
34029 @c attaching, GDB queries for the attached process's thread ID with qC.
34030 @c Also note that, from a user perspective, whether or not the
34031 @c target is stopped on attach in non-stop mode depends on whether you
34032 @c use the foreground or background version of the attach command, not
34033 @c on what vAttach does; GDB does the right thing with respect to either
34034 @c stopping or restarting threads.
34036 This packet is only available in extended mode (@pxref{extended mode}).
34042 @item @r{Any stop packet}
34043 for success in all-stop mode (@pxref{Stop Reply Packets})
34045 for success in non-stop mode (@pxref{Remote Non-Stop})
34048 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34049 @cindex @samp{vCont} packet
34050 @anchor{vCont packet}
34051 Resume the inferior, specifying different actions for each thread.
34052 If an action is specified with no @var{thread-id}, then it is applied to any
34053 threads that don't have a specific action specified; if no default action is
34054 specified then other threads should remain stopped in all-stop mode and
34055 in their current state in non-stop mode.
34056 Specifying multiple
34057 default actions is an error; specifying no actions is also an error.
34058 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34060 Currently supported actions are:
34066 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34070 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34075 The optional argument @var{addr} normally associated with the
34076 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34077 not supported in @samp{vCont}.
34079 The @samp{t} action is only relevant in non-stop mode
34080 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34081 A stop reply should be generated for any affected thread not already stopped.
34082 When a thread is stopped by means of a @samp{t} action,
34083 the corresponding stop reply should indicate that the thread has stopped with
34084 signal @samp{0}, regardless of whether the target uses some other signal
34085 as an implementation detail.
34087 The stub must support @samp{vCont} if it reports support for
34088 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34089 this case @samp{vCont} actions can be specified to apply to all threads
34090 in a process by using the @samp{p@var{pid}.-1} form of the
34094 @xref{Stop Reply Packets}, for the reply specifications.
34097 @cindex @samp{vCont?} packet
34098 Request a list of actions supported by the @samp{vCont} packet.
34102 @item vCont@r{[};@var{action}@dots{}@r{]}
34103 The @samp{vCont} packet is supported. Each @var{action} is a supported
34104 command in the @samp{vCont} packet.
34106 The @samp{vCont} packet is not supported.
34109 @item vFile:@var{operation}:@var{parameter}@dots{}
34110 @cindex @samp{vFile} packet
34111 Perform a file operation on the target system. For details,
34112 see @ref{Host I/O Packets}.
34114 @item vFlashErase:@var{addr},@var{length}
34115 @cindex @samp{vFlashErase} packet
34116 Direct the stub to erase @var{length} bytes of flash starting at
34117 @var{addr}. The region may enclose any number of flash blocks, but
34118 its start and end must fall on block boundaries, as indicated by the
34119 flash block size appearing in the memory map (@pxref{Memory Map
34120 Format}). @value{GDBN} groups flash memory programming operations
34121 together, and sends a @samp{vFlashDone} request after each group; the
34122 stub is allowed to delay erase operation until the @samp{vFlashDone}
34123 packet is received.
34133 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34134 @cindex @samp{vFlashWrite} packet
34135 Direct the stub to write data to flash address @var{addr}. The data
34136 is passed in binary form using the same encoding as for the @samp{X}
34137 packet (@pxref{Binary Data}). The memory ranges specified by
34138 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34139 not overlap, and must appear in order of increasing addresses
34140 (although @samp{vFlashErase} packets for higher addresses may already
34141 have been received; the ordering is guaranteed only between
34142 @samp{vFlashWrite} packets). If a packet writes to an address that was
34143 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34144 target-specific method, the results are unpredictable.
34152 for vFlashWrite addressing non-flash memory
34158 @cindex @samp{vFlashDone} packet
34159 Indicate to the stub that flash programming operation is finished.
34160 The stub is permitted to delay or batch the effects of a group of
34161 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34162 @samp{vFlashDone} packet is received. The contents of the affected
34163 regions of flash memory are unpredictable until the @samp{vFlashDone}
34164 request is completed.
34166 @item vKill;@var{pid}
34167 @cindex @samp{vKill} packet
34168 Kill the process with the specified process ID. @var{pid} is a
34169 hexadecimal integer identifying the process. This packet is used in
34170 preference to @samp{k} when multiprocess protocol extensions are
34171 supported; see @ref{multiprocess extensions}.
34181 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34182 @cindex @samp{vRun} packet
34183 Run the program @var{filename}, passing it each @var{argument} on its
34184 command line. The file and arguments are hex-encoded strings. If
34185 @var{filename} is an empty string, the stub may use a default program
34186 (e.g.@: the last program run). The program is created in the stopped
34189 @c FIXME: What about non-stop mode?
34191 This packet is only available in extended mode (@pxref{extended mode}).
34197 @item @r{Any stop packet}
34198 for success (@pxref{Stop Reply Packets})
34202 @anchor{vStopped packet}
34203 @cindex @samp{vStopped} packet
34205 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34206 reply and prompt for the stub to report another one.
34210 @item @r{Any stop packet}
34211 if there is another unreported stop event (@pxref{Stop Reply Packets})
34213 if there are no unreported stop events
34216 @item X @var{addr},@var{length}:@var{XX@dots{}}
34218 @cindex @samp{X} packet
34219 Write data to memory, where the data is transmitted in binary.
34220 @var{addr} is address, @var{length} is number of bytes,
34221 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34231 @item z @var{type},@var{addr},@var{kind}
34232 @itemx Z @var{type},@var{addr},@var{kind}
34233 @anchor{insert breakpoint or watchpoint packet}
34234 @cindex @samp{z} packet
34235 @cindex @samp{Z} packets
34236 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34237 watchpoint starting at address @var{address} of kind @var{kind}.
34239 Each breakpoint and watchpoint packet @var{type} is documented
34242 @emph{Implementation notes: A remote target shall return an empty string
34243 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34244 remote target shall support either both or neither of a given
34245 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34246 avoid potential problems with duplicate packets, the operations should
34247 be implemented in an idempotent way.}
34249 @item z0,@var{addr},@var{kind}
34250 @itemx Z0,@var{addr},@var{kind}
34251 @cindex @samp{z0} packet
34252 @cindex @samp{Z0} packet
34253 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34254 @var{addr} of type @var{kind}.
34256 A memory breakpoint is implemented by replacing the instruction at
34257 @var{addr} with a software breakpoint or trap instruction. The
34258 @var{kind} is target-specific and typically indicates the size of
34259 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34260 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34261 architectures have additional meanings for @var{kind};
34262 see @ref{Architecture-Specific Protocol Details}.
34264 @emph{Implementation note: It is possible for a target to copy or move
34265 code that contains memory breakpoints (e.g., when implementing
34266 overlays). The behavior of this packet, in the presence of such a
34267 target, is not defined.}
34279 @item z1,@var{addr},@var{kind}
34280 @itemx Z1,@var{addr},@var{kind}
34281 @cindex @samp{z1} packet
34282 @cindex @samp{Z1} packet
34283 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34284 address @var{addr}.
34286 A hardware breakpoint is implemented using a mechanism that is not
34287 dependant on being able to modify the target's memory. @var{kind}
34288 has the same meaning as in @samp{Z0} packets.
34290 @emph{Implementation note: A hardware breakpoint is not affected by code
34303 @item z2,@var{addr},@var{kind}
34304 @itemx Z2,@var{addr},@var{kind}
34305 @cindex @samp{z2} packet
34306 @cindex @samp{Z2} packet
34307 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34308 @var{kind} is interpreted as the number of bytes to watch.
34320 @item z3,@var{addr},@var{kind}
34321 @itemx Z3,@var{addr},@var{kind}
34322 @cindex @samp{z3} packet
34323 @cindex @samp{Z3} packet
34324 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34325 @var{kind} is interpreted as the number of bytes to watch.
34337 @item z4,@var{addr},@var{kind}
34338 @itemx Z4,@var{addr},@var{kind}
34339 @cindex @samp{z4} packet
34340 @cindex @samp{Z4} packet
34341 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34342 @var{kind} is interpreted as the number of bytes to watch.
34356 @node Stop Reply Packets
34357 @section Stop Reply Packets
34358 @cindex stop reply packets
34360 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34361 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34362 receive any of the below as a reply. Except for @samp{?}
34363 and @samp{vStopped}, that reply is only returned
34364 when the target halts. In the below the exact meaning of @dfn{signal
34365 number} is defined by the header @file{include/gdb/signals.h} in the
34366 @value{GDBN} source code.
34368 As in the description of request packets, we include spaces in the
34369 reply templates for clarity; these are not part of the reply packet's
34370 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34376 The program received signal number @var{AA} (a two-digit hexadecimal
34377 number). This is equivalent to a @samp{T} response with no
34378 @var{n}:@var{r} pairs.
34380 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34381 @cindex @samp{T} packet reply
34382 The program received signal number @var{AA} (a two-digit hexadecimal
34383 number). This is equivalent to an @samp{S} response, except that the
34384 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34385 and other information directly in the stop reply packet, reducing
34386 round-trip latency. Single-step and breakpoint traps are reported
34387 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34391 If @var{n} is a hexadecimal number, it is a register number, and the
34392 corresponding @var{r} gives that register's value. @var{r} is a
34393 series of bytes in target byte order, with each byte given by a
34394 two-digit hex number.
34397 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34398 the stopped thread, as specified in @ref{thread-id syntax}.
34401 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34402 the core on which the stop event was detected.
34405 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34406 specific event that stopped the target. The currently defined stop
34407 reasons are listed below. @var{aa} should be @samp{05}, the trap
34408 signal. At most one stop reason should be present.
34411 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34412 and go on to the next; this allows us to extend the protocol in the
34416 The currently defined stop reasons are:
34422 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34425 @cindex shared library events, remote reply
34427 The packet indicates that the loaded libraries have changed.
34428 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34429 list of loaded libraries. @var{r} is ignored.
34431 @cindex replay log events, remote reply
34433 The packet indicates that the target cannot continue replaying
34434 logged execution events, because it has reached the end (or the
34435 beginning when executing backward) of the log. The value of @var{r}
34436 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34437 for more information.
34441 @itemx W @var{AA} ; process:@var{pid}
34442 The process exited, and @var{AA} is the exit status. This is only
34443 applicable to certain targets.
34445 The second form of the response, including the process ID of the exited
34446 process, can be used only when @value{GDBN} has reported support for
34447 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34448 The @var{pid} is formatted as a big-endian hex string.
34451 @itemx X @var{AA} ; process:@var{pid}
34452 The process terminated with signal @var{AA}.
34454 The second form of the response, including the process ID of the
34455 terminated process, can be used only when @value{GDBN} has reported
34456 support for multiprocess protocol extensions; see @ref{multiprocess
34457 extensions}. The @var{pid} is formatted as a big-endian hex string.
34459 @item O @var{XX}@dots{}
34460 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34461 written as the program's console output. This can happen at any time
34462 while the program is running and the debugger should continue to wait
34463 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34465 @item F @var{call-id},@var{parameter}@dots{}
34466 @var{call-id} is the identifier which says which host system call should
34467 be called. This is just the name of the function. Translation into the
34468 correct system call is only applicable as it's defined in @value{GDBN}.
34469 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34472 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34473 this very system call.
34475 The target replies with this packet when it expects @value{GDBN} to
34476 call a host system call on behalf of the target. @value{GDBN} replies
34477 with an appropriate @samp{F} packet and keeps up waiting for the next
34478 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34479 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34480 Protocol Extension}, for more details.
34484 @node General Query Packets
34485 @section General Query Packets
34486 @cindex remote query requests
34488 Packets starting with @samp{q} are @dfn{general query packets};
34489 packets starting with @samp{Q} are @dfn{general set packets}. General
34490 query and set packets are a semi-unified form for retrieving and
34491 sending information to and from the stub.
34493 The initial letter of a query or set packet is followed by a name
34494 indicating what sort of thing the packet applies to. For example,
34495 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34496 definitions with the stub. These packet names follow some
34501 The name must not contain commas, colons or semicolons.
34503 Most @value{GDBN} query and set packets have a leading upper case
34506 The names of custom vendor packets should use a company prefix, in
34507 lower case, followed by a period. For example, packets designed at
34508 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34509 foos) or @samp{Qacme.bar} (for setting bars).
34512 The name of a query or set packet should be separated from any
34513 parameters by a @samp{:}; the parameters themselves should be
34514 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34515 full packet name, and check for a separator or the end of the packet,
34516 in case two packet names share a common prefix. New packets should not begin
34517 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34518 packets predate these conventions, and have arguments without any terminator
34519 for the packet name; we suspect they are in widespread use in places that
34520 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34521 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34524 Like the descriptions of the other packets, each description here
34525 has a template showing the packet's overall syntax, followed by an
34526 explanation of the packet's meaning. We include spaces in some of the
34527 templates for clarity; these are not part of the packet's syntax. No
34528 @value{GDBN} packet uses spaces to separate its components.
34530 Here are the currently defined query and set packets:
34534 @item QAllow:@var{op}:@var{val}@dots{}
34535 @cindex @samp{QAllow} packet
34536 Specify which operations @value{GDBN} expects to request of the
34537 target, as a semicolon-separated list of operation name and value
34538 pairs. Possible values for @var{op} include @samp{WriteReg},
34539 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34540 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34541 indicating that @value{GDBN} will not request the operation, or 1,
34542 indicating that it may. (The target can then use this to set up its
34543 own internals optimally, for instance if the debugger never expects to
34544 insert breakpoints, it may not need to install its own trap handler.)
34547 @cindex current thread, remote request
34548 @cindex @samp{qC} packet
34549 Return the current thread ID.
34553 @item QC @var{thread-id}
34554 Where @var{thread-id} is a thread ID as documented in
34555 @ref{thread-id syntax}.
34556 @item @r{(anything else)}
34557 Any other reply implies the old thread ID.
34560 @item qCRC:@var{addr},@var{length}
34561 @cindex CRC of memory block, remote request
34562 @cindex @samp{qCRC} packet
34563 Compute the CRC checksum of a block of memory using CRC-32 defined in
34564 IEEE 802.3. The CRC is computed byte at a time, taking the most
34565 significant bit of each byte first. The initial pattern code
34566 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34568 @emph{Note:} This is the same CRC used in validating separate debug
34569 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34570 Files}). However the algorithm is slightly different. When validating
34571 separate debug files, the CRC is computed taking the @emph{least}
34572 significant bit of each byte first, and the final result is inverted to
34573 detect trailing zeros.
34578 An error (such as memory fault)
34579 @item C @var{crc32}
34580 The specified memory region's checksum is @var{crc32}.
34583 @item QDisableRandomization:@var{value}
34584 @cindex disable address space randomization, remote request
34585 @cindex @samp{QDisableRandomization} packet
34586 Some target operating systems will randomize the virtual address space
34587 of the inferior process as a security feature, but provide a feature
34588 to disable such randomization, e.g.@: to allow for a more deterministic
34589 debugging experience. On such systems, this packet with a @var{value}
34590 of 1 directs the target to disable address space randomization for
34591 processes subsequently started via @samp{vRun} packets, while a packet
34592 with a @var{value} of 0 tells the target to enable address space
34595 This packet is only available in extended mode (@pxref{extended mode}).
34600 The request succeeded.
34603 An error occurred. @var{nn} are hex digits.
34606 An empty reply indicates that @samp{QDisableRandomization} is not supported
34610 This packet is not probed by default; the remote stub must request it,
34611 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34612 This should only be done on targets that actually support disabling
34613 address space randomization.
34616 @itemx qsThreadInfo
34617 @cindex list active threads, remote request
34618 @cindex @samp{qfThreadInfo} packet
34619 @cindex @samp{qsThreadInfo} packet
34620 Obtain a list of all active thread IDs from the target (OS). Since there
34621 may be too many active threads to fit into one reply packet, this query
34622 works iteratively: it may require more than one query/reply sequence to
34623 obtain the entire list of threads. The first query of the sequence will
34624 be the @samp{qfThreadInfo} query; subsequent queries in the
34625 sequence will be the @samp{qsThreadInfo} query.
34627 NOTE: This packet replaces the @samp{qL} query (see below).
34631 @item m @var{thread-id}
34633 @item m @var{thread-id},@var{thread-id}@dots{}
34634 a comma-separated list of thread IDs
34636 (lower case letter @samp{L}) denotes end of list.
34639 In response to each query, the target will reply with a list of one or
34640 more thread IDs, separated by commas.
34641 @value{GDBN} will respond to each reply with a request for more thread
34642 ids (using the @samp{qs} form of the query), until the target responds
34643 with @samp{l} (lower-case ell, for @dfn{last}).
34644 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34647 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34648 @cindex get thread-local storage address, remote request
34649 @cindex @samp{qGetTLSAddr} packet
34650 Fetch the address associated with thread local storage specified
34651 by @var{thread-id}, @var{offset}, and @var{lm}.
34653 @var{thread-id} is the thread ID associated with the
34654 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34656 @var{offset} is the (big endian, hex encoded) offset associated with the
34657 thread local variable. (This offset is obtained from the debug
34658 information associated with the variable.)
34660 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34661 load module associated with the thread local storage. For example,
34662 a @sc{gnu}/Linux system will pass the link map address of the shared
34663 object associated with the thread local storage under consideration.
34664 Other operating environments may choose to represent the load module
34665 differently, so the precise meaning of this parameter will vary.
34669 @item @var{XX}@dots{}
34670 Hex encoded (big endian) bytes representing the address of the thread
34671 local storage requested.
34674 An error occurred. @var{nn} are hex digits.
34677 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34680 @item qGetTIBAddr:@var{thread-id}
34681 @cindex get thread information block address
34682 @cindex @samp{qGetTIBAddr} packet
34683 Fetch address of the Windows OS specific Thread Information Block.
34685 @var{thread-id} is the thread ID associated with the thread.
34689 @item @var{XX}@dots{}
34690 Hex encoded (big endian) bytes representing the linear address of the
34691 thread information block.
34694 An error occured. This means that either the thread was not found, or the
34695 address could not be retrieved.
34698 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34701 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34702 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34703 digit) is one to indicate the first query and zero to indicate a
34704 subsequent query; @var{threadcount} (two hex digits) is the maximum
34705 number of threads the response packet can contain; and @var{nextthread}
34706 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34707 returned in the response as @var{argthread}.
34709 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34713 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34714 Where: @var{count} (two hex digits) is the number of threads being
34715 returned; @var{done} (one hex digit) is zero to indicate more threads
34716 and one indicates no further threads; @var{argthreadid} (eight hex
34717 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34718 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34719 digits). See @code{remote.c:parse_threadlist_response()}.
34723 @cindex section offsets, remote request
34724 @cindex @samp{qOffsets} packet
34725 Get section offsets that the target used when relocating the downloaded
34730 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34731 Relocate the @code{Text} section by @var{xxx} from its original address.
34732 Relocate the @code{Data} section by @var{yyy} from its original address.
34733 If the object file format provides segment information (e.g.@: @sc{elf}
34734 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34735 segments by the supplied offsets.
34737 @emph{Note: while a @code{Bss} offset may be included in the response,
34738 @value{GDBN} ignores this and instead applies the @code{Data} offset
34739 to the @code{Bss} section.}
34741 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34742 Relocate the first segment of the object file, which conventionally
34743 contains program code, to a starting address of @var{xxx}. If
34744 @samp{DataSeg} is specified, relocate the second segment, which
34745 conventionally contains modifiable data, to a starting address of
34746 @var{yyy}. @value{GDBN} will report an error if the object file
34747 does not contain segment information, or does not contain at least
34748 as many segments as mentioned in the reply. Extra segments are
34749 kept at fixed offsets relative to the last relocated segment.
34752 @item qP @var{mode} @var{thread-id}
34753 @cindex thread information, remote request
34754 @cindex @samp{qP} packet
34755 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34756 encoded 32 bit mode; @var{thread-id} is a thread ID
34757 (@pxref{thread-id syntax}).
34759 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34762 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34766 @cindex non-stop mode, remote request
34767 @cindex @samp{QNonStop} packet
34769 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34770 @xref{Remote Non-Stop}, for more information.
34775 The request succeeded.
34778 An error occurred. @var{nn} are hex digits.
34781 An empty reply indicates that @samp{QNonStop} is not supported by
34785 This packet is not probed by default; the remote stub must request it,
34786 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34787 Use of this packet is controlled by the @code{set non-stop} command;
34788 @pxref{Non-Stop Mode}.
34790 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34791 @cindex pass signals to inferior, remote request
34792 @cindex @samp{QPassSignals} packet
34793 @anchor{QPassSignals}
34794 Each listed @var{signal} should be passed directly to the inferior process.
34795 Signals are numbered identically to continue packets and stop replies
34796 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34797 strictly greater than the previous item. These signals do not need to stop
34798 the inferior, or be reported to @value{GDBN}. All other signals should be
34799 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34800 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34801 new list. This packet improves performance when using @samp{handle
34802 @var{signal} nostop noprint pass}.
34807 The request succeeded.
34810 An error occurred. @var{nn} are hex digits.
34813 An empty reply indicates that @samp{QPassSignals} is not supported by
34817 Use of this packet is controlled by the @code{set remote pass-signals}
34818 command (@pxref{Remote Configuration, set remote pass-signals}).
34819 This packet is not probed by default; the remote stub must request it,
34820 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34822 @item qRcmd,@var{command}
34823 @cindex execute remote command, remote request
34824 @cindex @samp{qRcmd} packet
34825 @var{command} (hex encoded) is passed to the local interpreter for
34826 execution. Invalid commands should be reported using the output
34827 string. Before the final result packet, the target may also respond
34828 with a number of intermediate @samp{O@var{output}} console output
34829 packets. @emph{Implementors should note that providing access to a
34830 stubs's interpreter may have security implications}.
34835 A command response with no output.
34837 A command response with the hex encoded output string @var{OUTPUT}.
34839 Indicate a badly formed request.
34841 An empty reply indicates that @samp{qRcmd} is not recognized.
34844 (Note that the @code{qRcmd} packet's name is separated from the
34845 command by a @samp{,}, not a @samp{:}, contrary to the naming
34846 conventions above. Please don't use this packet as a model for new
34849 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34850 @cindex searching memory, in remote debugging
34851 @cindex @samp{qSearch:memory} packet
34852 @anchor{qSearch memory}
34853 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34854 @var{address} and @var{length} are encoded in hex.
34855 @var{search-pattern} is a sequence of bytes, hex encoded.
34860 The pattern was not found.
34862 The pattern was found at @var{address}.
34864 A badly formed request or an error was encountered while searching memory.
34866 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34869 @item QStartNoAckMode
34870 @cindex @samp{QStartNoAckMode} packet
34871 @anchor{QStartNoAckMode}
34872 Request that the remote stub disable the normal @samp{+}/@samp{-}
34873 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34878 The stub has switched to no-acknowledgment mode.
34879 @value{GDBN} acknowledges this reponse,
34880 but neither the stub nor @value{GDBN} shall send or expect further
34881 @samp{+}/@samp{-} acknowledgments in the current connection.
34883 An empty reply indicates that the stub does not support no-acknowledgment mode.
34886 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34887 @cindex supported packets, remote query
34888 @cindex features of the remote protocol
34889 @cindex @samp{qSupported} packet
34890 @anchor{qSupported}
34891 Tell the remote stub about features supported by @value{GDBN}, and
34892 query the stub for features it supports. This packet allows
34893 @value{GDBN} and the remote stub to take advantage of each others'
34894 features. @samp{qSupported} also consolidates multiple feature probes
34895 at startup, to improve @value{GDBN} performance---a single larger
34896 packet performs better than multiple smaller probe packets on
34897 high-latency links. Some features may enable behavior which must not
34898 be on by default, e.g.@: because it would confuse older clients or
34899 stubs. Other features may describe packets which could be
34900 automatically probed for, but are not. These features must be
34901 reported before @value{GDBN} will use them. This ``default
34902 unsupported'' behavior is not appropriate for all packets, but it
34903 helps to keep the initial connection time under control with new
34904 versions of @value{GDBN} which support increasing numbers of packets.
34908 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34909 The stub supports or does not support each returned @var{stubfeature},
34910 depending on the form of each @var{stubfeature} (see below for the
34913 An empty reply indicates that @samp{qSupported} is not recognized,
34914 or that no features needed to be reported to @value{GDBN}.
34917 The allowed forms for each feature (either a @var{gdbfeature} in the
34918 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34922 @item @var{name}=@var{value}
34923 The remote protocol feature @var{name} is supported, and associated
34924 with the specified @var{value}. The format of @var{value} depends
34925 on the feature, but it must not include a semicolon.
34927 The remote protocol feature @var{name} is supported, and does not
34928 need an associated value.
34930 The remote protocol feature @var{name} is not supported.
34932 The remote protocol feature @var{name} may be supported, and
34933 @value{GDBN} should auto-detect support in some other way when it is
34934 needed. This form will not be used for @var{gdbfeature} notifications,
34935 but may be used for @var{stubfeature} responses.
34938 Whenever the stub receives a @samp{qSupported} request, the
34939 supplied set of @value{GDBN} features should override any previous
34940 request. This allows @value{GDBN} to put the stub in a known
34941 state, even if the stub had previously been communicating with
34942 a different version of @value{GDBN}.
34944 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34949 This feature indicates whether @value{GDBN} supports multiprocess
34950 extensions to the remote protocol. @value{GDBN} does not use such
34951 extensions unless the stub also reports that it supports them by
34952 including @samp{multiprocess+} in its @samp{qSupported} reply.
34953 @xref{multiprocess extensions}, for details.
34956 This feature indicates that @value{GDBN} supports the XML target
34957 description. If the stub sees @samp{xmlRegisters=} with target
34958 specific strings separated by a comma, it will report register
34962 This feature indicates whether @value{GDBN} supports the
34963 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34964 instruction reply packet}).
34967 Stubs should ignore any unknown values for
34968 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34969 packet supports receiving packets of unlimited length (earlier
34970 versions of @value{GDBN} may reject overly long responses). Additional values
34971 for @var{gdbfeature} may be defined in the future to let the stub take
34972 advantage of new features in @value{GDBN}, e.g.@: incompatible
34973 improvements in the remote protocol---the @samp{multiprocess} feature is
34974 an example of such a feature. The stub's reply should be independent
34975 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34976 describes all the features it supports, and then the stub replies with
34977 all the features it supports.
34979 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34980 responses, as long as each response uses one of the standard forms.
34982 Some features are flags. A stub which supports a flag feature
34983 should respond with a @samp{+} form response. Other features
34984 require values, and the stub should respond with an @samp{=}
34987 Each feature has a default value, which @value{GDBN} will use if
34988 @samp{qSupported} is not available or if the feature is not mentioned
34989 in the @samp{qSupported} response. The default values are fixed; a
34990 stub is free to omit any feature responses that match the defaults.
34992 Not all features can be probed, but for those which can, the probing
34993 mechanism is useful: in some cases, a stub's internal
34994 architecture may not allow the protocol layer to know some information
34995 about the underlying target in advance. This is especially common in
34996 stubs which may be configured for multiple targets.
34998 These are the currently defined stub features and their properties:
35000 @multitable @columnfractions 0.35 0.2 0.12 0.2
35001 @c NOTE: The first row should be @headitem, but we do not yet require
35002 @c a new enough version of Texinfo (4.7) to use @headitem.
35004 @tab Value Required
35008 @item @samp{PacketSize}
35013 @item @samp{qXfer:auxv:read}
35018 @item @samp{qXfer:features:read}
35023 @item @samp{qXfer:libraries:read}
35028 @item @samp{qXfer:memory-map:read}
35033 @item @samp{qXfer:sdata:read}
35038 @item @samp{qXfer:spu:read}
35043 @item @samp{qXfer:spu:write}
35048 @item @samp{qXfer:siginfo:read}
35053 @item @samp{qXfer:siginfo:write}
35058 @item @samp{qXfer:threads:read}
35063 @item @samp{qXfer:traceframe-info:read}
35068 @item @samp{qXfer:fdpic:read}
35073 @item @samp{QNonStop}
35078 @item @samp{QPassSignals}
35083 @item @samp{QStartNoAckMode}
35088 @item @samp{multiprocess}
35093 @item @samp{ConditionalTracepoints}
35098 @item @samp{ReverseContinue}
35103 @item @samp{ReverseStep}
35108 @item @samp{TracepointSource}
35113 @item @samp{QAllow}
35118 @item @samp{QDisableRandomization}
35123 @item @samp{EnableDisableTracepoints}
35128 @item @samp{tracenz}
35135 These are the currently defined stub features, in more detail:
35138 @cindex packet size, remote protocol
35139 @item PacketSize=@var{bytes}
35140 The remote stub can accept packets up to at least @var{bytes} in
35141 length. @value{GDBN} will send packets up to this size for bulk
35142 transfers, and will never send larger packets. This is a limit on the
35143 data characters in the packet, including the frame and checksum.
35144 There is no trailing NUL byte in a remote protocol packet; if the stub
35145 stores packets in a NUL-terminated format, it should allow an extra
35146 byte in its buffer for the NUL. If this stub feature is not supported,
35147 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35149 @item qXfer:auxv:read
35150 The remote stub understands the @samp{qXfer:auxv:read} packet
35151 (@pxref{qXfer auxiliary vector read}).
35153 @item qXfer:features:read
35154 The remote stub understands the @samp{qXfer:features:read} packet
35155 (@pxref{qXfer target description read}).
35157 @item qXfer:libraries:read
35158 The remote stub understands the @samp{qXfer:libraries:read} packet
35159 (@pxref{qXfer library list read}).
35161 @item qXfer:libraries-svr4:read
35162 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35163 (@pxref{qXfer svr4 library list read}).
35165 @item qXfer:memory-map:read
35166 The remote stub understands the @samp{qXfer:memory-map:read} packet
35167 (@pxref{qXfer memory map read}).
35169 @item qXfer:sdata:read
35170 The remote stub understands the @samp{qXfer:sdata:read} packet
35171 (@pxref{qXfer sdata read}).
35173 @item qXfer:spu:read
35174 The remote stub understands the @samp{qXfer:spu:read} packet
35175 (@pxref{qXfer spu read}).
35177 @item qXfer:spu:write
35178 The remote stub understands the @samp{qXfer:spu:write} packet
35179 (@pxref{qXfer spu write}).
35181 @item qXfer:siginfo:read
35182 The remote stub understands the @samp{qXfer:siginfo:read} packet
35183 (@pxref{qXfer siginfo read}).
35185 @item qXfer:siginfo:write
35186 The remote stub understands the @samp{qXfer:siginfo:write} packet
35187 (@pxref{qXfer siginfo write}).
35189 @item qXfer:threads:read
35190 The remote stub understands the @samp{qXfer:threads:read} packet
35191 (@pxref{qXfer threads read}).
35193 @item qXfer:traceframe-info:read
35194 The remote stub understands the @samp{qXfer:traceframe-info:read}
35195 packet (@pxref{qXfer traceframe info read}).
35197 @item qXfer:fdpic:read
35198 The remote stub understands the @samp{qXfer:fdpic:read}
35199 packet (@pxref{qXfer fdpic loadmap read}).
35202 The remote stub understands the @samp{QNonStop} packet
35203 (@pxref{QNonStop}).
35206 The remote stub understands the @samp{QPassSignals} packet
35207 (@pxref{QPassSignals}).
35209 @item QStartNoAckMode
35210 The remote stub understands the @samp{QStartNoAckMode} packet and
35211 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35214 @anchor{multiprocess extensions}
35215 @cindex multiprocess extensions, in remote protocol
35216 The remote stub understands the multiprocess extensions to the remote
35217 protocol syntax. The multiprocess extensions affect the syntax of
35218 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35219 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35220 replies. Note that reporting this feature indicates support for the
35221 syntactic extensions only, not that the stub necessarily supports
35222 debugging of more than one process at a time. The stub must not use
35223 multiprocess extensions in packet replies unless @value{GDBN} has also
35224 indicated it supports them in its @samp{qSupported} request.
35226 @item qXfer:osdata:read
35227 The remote stub understands the @samp{qXfer:osdata:read} packet
35228 ((@pxref{qXfer osdata read}).
35230 @item ConditionalTracepoints
35231 The remote stub accepts and implements conditional expressions defined
35232 for tracepoints (@pxref{Tracepoint Conditions}).
35234 @item ReverseContinue
35235 The remote stub accepts and implements the reverse continue packet
35239 The remote stub accepts and implements the reverse step packet
35242 @item TracepointSource
35243 The remote stub understands the @samp{QTDPsrc} packet that supplies
35244 the source form of tracepoint definitions.
35247 The remote stub understands the @samp{QAllow} packet.
35249 @item QDisableRandomization
35250 The remote stub understands the @samp{QDisableRandomization} packet.
35252 @item StaticTracepoint
35253 @cindex static tracepoints, in remote protocol
35254 The remote stub supports static tracepoints.
35256 @item InstallInTrace
35257 @anchor{install tracepoint in tracing}
35258 The remote stub supports installing tracepoint in tracing.
35260 @item EnableDisableTracepoints
35261 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35262 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35263 to be enabled and disabled while a trace experiment is running.
35266 @cindex string tracing, in remote protocol
35267 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35268 See @ref{Bytecode Descriptions} for details about the bytecode.
35273 @cindex symbol lookup, remote request
35274 @cindex @samp{qSymbol} packet
35275 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35276 requests. Accept requests from the target for the values of symbols.
35281 The target does not need to look up any (more) symbols.
35282 @item qSymbol:@var{sym_name}
35283 The target requests the value of symbol @var{sym_name} (hex encoded).
35284 @value{GDBN} may provide the value by using the
35285 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35289 @item qSymbol:@var{sym_value}:@var{sym_name}
35290 Set the value of @var{sym_name} to @var{sym_value}.
35292 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35293 target has previously requested.
35295 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35296 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35302 The target does not need to look up any (more) symbols.
35303 @item qSymbol:@var{sym_name}
35304 The target requests the value of a new symbol @var{sym_name} (hex
35305 encoded). @value{GDBN} will continue to supply the values of symbols
35306 (if available), until the target ceases to request them.
35311 @item QTDisconnected
35318 @itemx qTMinFTPILen
35320 @xref{Tracepoint Packets}.
35322 @item qThreadExtraInfo,@var{thread-id}
35323 @cindex thread attributes info, remote request
35324 @cindex @samp{qThreadExtraInfo} packet
35325 Obtain a printable string description of a thread's attributes from
35326 the target OS. @var{thread-id} is a thread ID;
35327 see @ref{thread-id syntax}. This
35328 string may contain anything that the target OS thinks is interesting
35329 for @value{GDBN} to tell the user about the thread. The string is
35330 displayed in @value{GDBN}'s @code{info threads} display. Some
35331 examples of possible thread extra info strings are @samp{Runnable}, or
35332 @samp{Blocked on Mutex}.
35336 @item @var{XX}@dots{}
35337 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35338 comprising the printable string containing the extra information about
35339 the thread's attributes.
35342 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35343 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35344 conventions above. Please don't use this packet as a model for new
35363 @xref{Tracepoint Packets}.
35365 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35366 @cindex read special object, remote request
35367 @cindex @samp{qXfer} packet
35368 @anchor{qXfer read}
35369 Read uninterpreted bytes from the target's special data area
35370 identified by the keyword @var{object}. Request @var{length} bytes
35371 starting at @var{offset} bytes into the data. The content and
35372 encoding of @var{annex} is specific to @var{object}; it can supply
35373 additional details about what data to access.
35375 Here are the specific requests of this form defined so far. All
35376 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35377 formats, listed below.
35380 @item qXfer:auxv:read::@var{offset},@var{length}
35381 @anchor{qXfer auxiliary vector read}
35382 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35383 auxiliary vector}. Note @var{annex} must be empty.
35385 This packet is not probed by default; the remote stub must request it,
35386 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35388 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35389 @anchor{qXfer target description read}
35390 Access the @dfn{target description}. @xref{Target Descriptions}. The
35391 annex specifies which XML document to access. The main description is
35392 always loaded from the @samp{target.xml} annex.
35394 This packet is not probed by default; the remote stub must request it,
35395 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35397 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35398 @anchor{qXfer library list read}
35399 Access the target's list of loaded libraries. @xref{Library List Format}.
35400 The annex part of the generic @samp{qXfer} packet must be empty
35401 (@pxref{qXfer read}).
35403 Targets which maintain a list of libraries in the program's memory do
35404 not need to implement this packet; it is designed for platforms where
35405 the operating system manages the list of loaded libraries.
35407 This packet is not probed by default; the remote stub must request it,
35408 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35410 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35411 @anchor{qXfer svr4 library list read}
35412 Access the target's list of loaded libraries when the target is an SVR4
35413 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35414 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35416 This packet is optional for better performance on SVR4 targets.
35417 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35419 This packet is not probed by default; the remote stub must request it,
35420 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35422 @item qXfer:memory-map:read::@var{offset},@var{length}
35423 @anchor{qXfer memory map read}
35424 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35425 annex part of the generic @samp{qXfer} packet must be empty
35426 (@pxref{qXfer read}).
35428 This packet is not probed by default; the remote stub must request it,
35429 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35431 @item qXfer:sdata:read::@var{offset},@var{length}
35432 @anchor{qXfer sdata read}
35434 Read contents of the extra collected static tracepoint marker
35435 information. The annex part of the generic @samp{qXfer} packet must
35436 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35439 This packet is not probed by default; the remote stub must request it,
35440 by supplying an appropriate @samp{qSupported} response
35441 (@pxref{qSupported}).
35443 @item qXfer:siginfo:read::@var{offset},@var{length}
35444 @anchor{qXfer siginfo read}
35445 Read contents of the extra signal information on the target
35446 system. The annex part of the generic @samp{qXfer} packet must be
35447 empty (@pxref{qXfer read}).
35449 This packet is not probed by default; the remote stub must request it,
35450 by supplying an appropriate @samp{qSupported} response
35451 (@pxref{qSupported}).
35453 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35454 @anchor{qXfer spu read}
35455 Read contents of an @code{spufs} file on the target system. The
35456 annex specifies which file to read; it must be of the form
35457 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35458 in the target process, and @var{name} identifes the @code{spufs} file
35459 in that context to be accessed.
35461 This packet is not probed by default; the remote stub must request it,
35462 by supplying an appropriate @samp{qSupported} response
35463 (@pxref{qSupported}).
35465 @item qXfer:threads:read::@var{offset},@var{length}
35466 @anchor{qXfer threads read}
35467 Access the list of threads on target. @xref{Thread List Format}. The
35468 annex part of the generic @samp{qXfer} packet must be empty
35469 (@pxref{qXfer read}).
35471 This packet is not probed by default; the remote stub must request it,
35472 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35474 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35475 @anchor{qXfer traceframe info read}
35477 Return a description of the current traceframe's contents.
35478 @xref{Traceframe Info Format}. The annex part of the generic
35479 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35481 This packet is not probed by default; the remote stub must request it,
35482 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35484 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35485 @anchor{qXfer fdpic loadmap read}
35486 Read contents of @code{loadmap}s on the target system. The
35487 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35488 executable @code{loadmap} or interpreter @code{loadmap} to read.
35490 This packet is not probed by default; the remote stub must request it,
35491 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35493 @item qXfer:osdata:read::@var{offset},@var{length}
35494 @anchor{qXfer osdata read}
35495 Access the target's @dfn{operating system information}.
35496 @xref{Operating System Information}.
35503 Data @var{data} (@pxref{Binary Data}) has been read from the
35504 target. There may be more data at a higher address (although
35505 it is permitted to return @samp{m} even for the last valid
35506 block of data, as long as at least one byte of data was read).
35507 @var{data} may have fewer bytes than the @var{length} in the
35511 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35512 There is no more data to be read. @var{data} may have fewer bytes
35513 than the @var{length} in the request.
35516 The @var{offset} in the request is at the end of the data.
35517 There is no more data to be read.
35520 The request was malformed, or @var{annex} was invalid.
35523 The offset was invalid, or there was an error encountered reading the data.
35524 @var{nn} is a hex-encoded @code{errno} value.
35527 An empty reply indicates the @var{object} string was not recognized by
35528 the stub, or that the object does not support reading.
35531 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35532 @cindex write data into object, remote request
35533 @anchor{qXfer write}
35534 Write uninterpreted bytes into the target's special data area
35535 identified by the keyword @var{object}, starting at @var{offset} bytes
35536 into the data. @var{data}@dots{} is the binary-encoded data
35537 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35538 is specific to @var{object}; it can supply additional details about what data
35541 Here are the specific requests of this form defined so far. All
35542 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35543 formats, listed below.
35546 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35547 @anchor{qXfer siginfo write}
35548 Write @var{data} to the extra signal information on the target system.
35549 The annex part of the generic @samp{qXfer} packet must be
35550 empty (@pxref{qXfer write}).
35552 This packet is not probed by default; the remote stub must request it,
35553 by supplying an appropriate @samp{qSupported} response
35554 (@pxref{qSupported}).
35556 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35557 @anchor{qXfer spu write}
35558 Write @var{data} to an @code{spufs} file on the target system. The
35559 annex specifies which file to write; it must be of the form
35560 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35561 in the target process, and @var{name} identifes the @code{spufs} file
35562 in that context to be accessed.
35564 This packet is not probed by default; the remote stub must request it,
35565 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35571 @var{nn} (hex encoded) is the number of bytes written.
35572 This may be fewer bytes than supplied in the request.
35575 The request was malformed, or @var{annex} was invalid.
35578 The offset was invalid, or there was an error encountered writing the data.
35579 @var{nn} is a hex-encoded @code{errno} value.
35582 An empty reply indicates the @var{object} string was not
35583 recognized by the stub, or that the object does not support writing.
35586 @item qXfer:@var{object}:@var{operation}:@dots{}
35587 Requests of this form may be added in the future. When a stub does
35588 not recognize the @var{object} keyword, or its support for
35589 @var{object} does not recognize the @var{operation} keyword, the stub
35590 must respond with an empty packet.
35592 @item qAttached:@var{pid}
35593 @cindex query attached, remote request
35594 @cindex @samp{qAttached} packet
35595 Return an indication of whether the remote server attached to an
35596 existing process or created a new process. When the multiprocess
35597 protocol extensions are supported (@pxref{multiprocess extensions}),
35598 @var{pid} is an integer in hexadecimal format identifying the target
35599 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35600 the query packet will be simplified as @samp{qAttached}.
35602 This query is used, for example, to know whether the remote process
35603 should be detached or killed when a @value{GDBN} session is ended with
35604 the @code{quit} command.
35609 The remote server attached to an existing process.
35611 The remote server created a new process.
35613 A badly formed request or an error was encountered.
35618 @node Architecture-Specific Protocol Details
35619 @section Architecture-Specific Protocol Details
35621 This section describes how the remote protocol is applied to specific
35622 target architectures. Also see @ref{Standard Target Features}, for
35623 details of XML target descriptions for each architecture.
35627 @subsubsection Breakpoint Kinds
35629 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35634 16-bit Thumb mode breakpoint.
35637 32-bit Thumb mode (Thumb-2) breakpoint.
35640 32-bit ARM mode breakpoint.
35646 @subsubsection Register Packet Format
35648 The following @code{g}/@code{G} packets have previously been defined.
35649 In the below, some thirty-two bit registers are transferred as
35650 sixty-four bits. Those registers should be zero/sign extended (which?)
35651 to fill the space allocated. Register bytes are transferred in target
35652 byte order. The two nibbles within a register byte are transferred
35653 most-significant - least-significant.
35659 All registers are transferred as thirty-two bit quantities in the order:
35660 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35661 registers; fsr; fir; fp.
35665 All registers are transferred as sixty-four bit quantities (including
35666 thirty-two bit registers such as @code{sr}). The ordering is the same
35671 @node Tracepoint Packets
35672 @section Tracepoint Packets
35673 @cindex tracepoint packets
35674 @cindex packets, tracepoint
35676 Here we describe the packets @value{GDBN} uses to implement
35677 tracepoints (@pxref{Tracepoints}).
35681 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35682 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35683 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35684 the tracepoint is disabled. @var{step} is the tracepoint's step
35685 count, and @var{pass} is its pass count. If an @samp{F} is present,
35686 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35687 the number of bytes that the target should copy elsewhere to make room
35688 for the tracepoint. If an @samp{X} is present, it introduces a
35689 tracepoint condition, which consists of a hexadecimal length, followed
35690 by a comma and hex-encoded bytes, in a manner similar to action
35691 encodings as described below. If the trailing @samp{-} is present,
35692 further @samp{QTDP} packets will follow to specify this tracepoint's
35698 The packet was understood and carried out.
35700 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35702 The packet was not recognized.
35705 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35706 Define actions to be taken when a tracepoint is hit. @var{n} and
35707 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35708 this tracepoint. This packet may only be sent immediately after
35709 another @samp{QTDP} packet that ended with a @samp{-}. If the
35710 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35711 specifying more actions for this tracepoint.
35713 In the series of action packets for a given tracepoint, at most one
35714 can have an @samp{S} before its first @var{action}. If such a packet
35715 is sent, it and the following packets define ``while-stepping''
35716 actions. Any prior packets define ordinary actions --- that is, those
35717 taken when the tracepoint is first hit. If no action packet has an
35718 @samp{S}, then all the packets in the series specify ordinary
35719 tracepoint actions.
35721 The @samp{@var{action}@dots{}} portion of the packet is a series of
35722 actions, concatenated without separators. Each action has one of the
35728 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35729 a hexadecimal number whose @var{i}'th bit is set if register number
35730 @var{i} should be collected. (The least significant bit is numbered
35731 zero.) Note that @var{mask} may be any number of digits long; it may
35732 not fit in a 32-bit word.
35734 @item M @var{basereg},@var{offset},@var{len}
35735 Collect @var{len} bytes of memory starting at the address in register
35736 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35737 @samp{-1}, then the range has a fixed address: @var{offset} is the
35738 address of the lowest byte to collect. The @var{basereg},
35739 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35740 values (the @samp{-1} value for @var{basereg} is a special case).
35742 @item X @var{len},@var{expr}
35743 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35744 it directs. @var{expr} is an agent expression, as described in
35745 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35746 two-digit hex number in the packet; @var{len} is the number of bytes
35747 in the expression (and thus one-half the number of hex digits in the
35752 Any number of actions may be packed together in a single @samp{QTDP}
35753 packet, as long as the packet does not exceed the maximum packet
35754 length (400 bytes, for many stubs). There may be only one @samp{R}
35755 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35756 actions. Any registers referred to by @samp{M} and @samp{X} actions
35757 must be collected by a preceding @samp{R} action. (The
35758 ``while-stepping'' actions are treated as if they were attached to a
35759 separate tracepoint, as far as these restrictions are concerned.)
35764 The packet was understood and carried out.
35766 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35768 The packet was not recognized.
35771 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35772 @cindex @samp{QTDPsrc} packet
35773 Specify a source string of tracepoint @var{n} at address @var{addr}.
35774 This is useful to get accurate reproduction of the tracepoints
35775 originally downloaded at the beginning of the trace run. @var{type}
35776 is the name of the tracepoint part, such as @samp{cond} for the
35777 tracepoint's conditional expression (see below for a list of types), while
35778 @var{bytes} is the string, encoded in hexadecimal.
35780 @var{start} is the offset of the @var{bytes} within the overall source
35781 string, while @var{slen} is the total length of the source string.
35782 This is intended for handling source strings that are longer than will
35783 fit in a single packet.
35784 @c Add detailed example when this info is moved into a dedicated
35785 @c tracepoint descriptions section.
35787 The available string types are @samp{at} for the location,
35788 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35789 @value{GDBN} sends a separate packet for each command in the action
35790 list, in the same order in which the commands are stored in the list.
35792 The target does not need to do anything with source strings except
35793 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35796 Although this packet is optional, and @value{GDBN} will only send it
35797 if the target replies with @samp{TracepointSource} @xref{General
35798 Query Packets}, it makes both disconnected tracing and trace files
35799 much easier to use. Otherwise the user must be careful that the
35800 tracepoints in effect while looking at trace frames are identical to
35801 the ones in effect during the trace run; even a small discrepancy
35802 could cause @samp{tdump} not to work, or a particular trace frame not
35805 @item QTDV:@var{n}:@var{value}
35806 @cindex define trace state variable, remote request
35807 @cindex @samp{QTDV} packet
35808 Create a new trace state variable, number @var{n}, with an initial
35809 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35810 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35811 the option of not using this packet for initial values of zero; the
35812 target should simply create the trace state variables as they are
35813 mentioned in expressions.
35815 @item QTFrame:@var{n}
35816 Select the @var{n}'th tracepoint frame from the buffer, and use the
35817 register and memory contents recorded there to answer subsequent
35818 request packets from @value{GDBN}.
35820 A successful reply from the stub indicates that the stub has found the
35821 requested frame. The response is a series of parts, concatenated
35822 without separators, describing the frame we selected. Each part has
35823 one of the following forms:
35827 The selected frame is number @var{n} in the trace frame buffer;
35828 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35829 was no frame matching the criteria in the request packet.
35832 The selected trace frame records a hit of tracepoint number @var{t};
35833 @var{t} is a hexadecimal number.
35837 @item QTFrame:pc:@var{addr}
35838 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35839 currently selected frame whose PC is @var{addr};
35840 @var{addr} is a hexadecimal number.
35842 @item QTFrame:tdp:@var{t}
35843 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35844 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35845 is a hexadecimal number.
35847 @item QTFrame:range:@var{start}:@var{end}
35848 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35849 currently selected frame whose PC is between @var{start} (inclusive)
35850 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35853 @item QTFrame:outside:@var{start}:@var{end}
35854 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35855 frame @emph{outside} the given range of addresses (exclusive).
35858 This packet requests the minimum length of instruction at which a fast
35859 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35860 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35861 it depends on the target system being able to create trampolines in
35862 the first 64K of memory, which might or might not be possible for that
35863 system. So the reply to this packet will be 4 if it is able to
35870 The minimum instruction length is currently unknown.
35872 The minimum instruction length is @var{length}, where @var{length} is greater
35873 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35874 that a fast tracepoint may be placed on any instruction regardless of size.
35876 An error has occurred.
35878 An empty reply indicates that the request is not supported by the stub.
35882 Begin the tracepoint experiment. Begin collecting data from
35883 tracepoint hits in the trace frame buffer. This packet supports the
35884 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35885 instruction reply packet}).
35888 End the tracepoint experiment. Stop collecting trace frames.
35890 @item QTEnable:@var{n}:@var{addr}
35892 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35893 experiment. If the tracepoint was previously disabled, then collection
35894 of data from it will resume.
35896 @item QTDisable:@var{n}:@var{addr}
35898 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35899 experiment. No more data will be collected from the tracepoint unless
35900 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35903 Clear the table of tracepoints, and empty the trace frame buffer.
35905 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35906 Establish the given ranges of memory as ``transparent''. The stub
35907 will answer requests for these ranges from memory's current contents,
35908 if they were not collected as part of the tracepoint hit.
35910 @value{GDBN} uses this to mark read-only regions of memory, like those
35911 containing program code. Since these areas never change, they should
35912 still have the same contents they did when the tracepoint was hit, so
35913 there's no reason for the stub to refuse to provide their contents.
35915 @item QTDisconnected:@var{value}
35916 Set the choice to what to do with the tracing run when @value{GDBN}
35917 disconnects from the target. A @var{value} of 1 directs the target to
35918 continue the tracing run, while 0 tells the target to stop tracing if
35919 @value{GDBN} is no longer in the picture.
35922 Ask the stub if there is a trace experiment running right now.
35924 The reply has the form:
35928 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35929 @var{running} is a single digit @code{1} if the trace is presently
35930 running, or @code{0} if not. It is followed by semicolon-separated
35931 optional fields that an agent may use to report additional status.
35935 If the trace is not running, the agent may report any of several
35936 explanations as one of the optional fields:
35941 No trace has been run yet.
35943 @item tstop[:@var{text}]:0
35944 The trace was stopped by a user-originated stop command. The optional
35945 @var{text} field is a user-supplied string supplied as part of the
35946 stop command (for instance, an explanation of why the trace was
35947 stopped manually). It is hex-encoded.
35950 The trace stopped because the trace buffer filled up.
35952 @item tdisconnected:0
35953 The trace stopped because @value{GDBN} disconnected from the target.
35955 @item tpasscount:@var{tpnum}
35956 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35958 @item terror:@var{text}:@var{tpnum}
35959 The trace stopped because tracepoint @var{tpnum} had an error. The
35960 string @var{text} is available to describe the nature of the error
35961 (for instance, a divide by zero in the condition expression).
35962 @var{text} is hex encoded.
35965 The trace stopped for some other reason.
35969 Additional optional fields supply statistical and other information.
35970 Although not required, they are extremely useful for users monitoring
35971 the progress of a trace run. If a trace has stopped, and these
35972 numbers are reported, they must reflect the state of the just-stopped
35977 @item tframes:@var{n}
35978 The number of trace frames in the buffer.
35980 @item tcreated:@var{n}
35981 The total number of trace frames created during the run. This may
35982 be larger than the trace frame count, if the buffer is circular.
35984 @item tsize:@var{n}
35985 The total size of the trace buffer, in bytes.
35987 @item tfree:@var{n}
35988 The number of bytes still unused in the buffer.
35990 @item circular:@var{n}
35991 The value of the circular trace buffer flag. @code{1} means that the
35992 trace buffer is circular and old trace frames will be discarded if
35993 necessary to make room, @code{0} means that the trace buffer is linear
35996 @item disconn:@var{n}
35997 The value of the disconnected tracing flag. @code{1} means that
35998 tracing will continue after @value{GDBN} disconnects, @code{0} means
35999 that the trace run will stop.
36003 @item qTP:@var{tp}:@var{addr}
36004 @cindex tracepoint status, remote request
36005 @cindex @samp{qTP} packet
36006 Ask the stub for the current state of tracepoint number @var{tp} at
36007 address @var{addr}.
36011 @item V@var{hits}:@var{usage}
36012 The tracepoint has been hit @var{hits} times so far during the trace
36013 run, and accounts for @var{usage} in the trace buffer. Note that
36014 @code{while-stepping} steps are not counted as separate hits, but the
36015 steps' space consumption is added into the usage number.
36019 @item qTV:@var{var}
36020 @cindex trace state variable value, remote request
36021 @cindex @samp{qTV} packet
36022 Ask the stub for the value of the trace state variable number @var{var}.
36027 The value of the variable is @var{value}. This will be the current
36028 value of the variable if the user is examining a running target, or a
36029 saved value if the variable was collected in the trace frame that the
36030 user is looking at. Note that multiple requests may result in
36031 different reply values, such as when requesting values while the
36032 program is running.
36035 The value of the variable is unknown. This would occur, for example,
36036 if the user is examining a trace frame in which the requested variable
36042 These packets request data about tracepoints that are being used by
36043 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36044 of data, and multiple @code{qTsP} to get additional pieces. Replies
36045 to these packets generally take the form of the @code{QTDP} packets
36046 that define tracepoints. (FIXME add detailed syntax)
36050 These packets request data about trace state variables that are on the
36051 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36052 and multiple @code{qTsV} to get additional variables. Replies to
36053 these packets follow the syntax of the @code{QTDV} packets that define
36054 trace state variables.
36058 These packets request data about static tracepoint markers that exist
36059 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36060 first piece of data, and multiple @code{qTsSTM} to get additional
36061 pieces. Replies to these packets take the following form:
36065 @item m @var{address}:@var{id}:@var{extra}
36067 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36068 a comma-separated list of markers
36070 (lower case letter @samp{L}) denotes end of list.
36072 An error occurred. @var{nn} are hex digits.
36074 An empty reply indicates that the request is not supported by the
36078 @var{address} is encoded in hex.
36079 @var{id} and @var{extra} are strings encoded in hex.
36081 In response to each query, the target will reply with a list of one or
36082 more markers, separated by commas. @value{GDBN} will respond to each
36083 reply with a request for more markers (using the @samp{qs} form of the
36084 query), until the target responds with @samp{l} (lower-case ell, for
36087 @item qTSTMat:@var{address}
36088 This packets requests data about static tracepoint markers in the
36089 target program at @var{address}. Replies to this packet follow the
36090 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36091 tracepoint markers.
36093 @item QTSave:@var{filename}
36094 This packet directs the target to save trace data to the file name
36095 @var{filename} in the target's filesystem. @var{filename} is encoded
36096 as a hex string; the interpretation of the file name (relative vs
36097 absolute, wild cards, etc) is up to the target.
36099 @item qTBuffer:@var{offset},@var{len}
36100 Return up to @var{len} bytes of the current contents of trace buffer,
36101 starting at @var{offset}. The trace buffer is treated as if it were
36102 a contiguous collection of traceframes, as per the trace file format.
36103 The reply consists as many hex-encoded bytes as the target can deliver
36104 in a packet; it is not an error to return fewer than were asked for.
36105 A reply consisting of just @code{l} indicates that no bytes are
36108 @item QTBuffer:circular:@var{value}
36109 This packet directs the target to use a circular trace buffer if
36110 @var{value} is 1, or a linear buffer if the value is 0.
36112 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36113 This packet adds optional textual notes to the trace run. Allowable
36114 types include @code{user}, @code{notes}, and @code{tstop}, the
36115 @var{text} fields are arbitrary strings, hex-encoded.
36119 @subsection Relocate instruction reply packet
36120 When installing fast tracepoints in memory, the target may need to
36121 relocate the instruction currently at the tracepoint address to a
36122 different address in memory. For most instructions, a simple copy is
36123 enough, but, for example, call instructions that implicitly push the
36124 return address on the stack, and relative branches or other
36125 PC-relative instructions require offset adjustment, so that the effect
36126 of executing the instruction at a different address is the same as if
36127 it had executed in the original location.
36129 In response to several of the tracepoint packets, the target may also
36130 respond with a number of intermediate @samp{qRelocInsn} request
36131 packets before the final result packet, to have @value{GDBN} handle
36132 this relocation operation. If a packet supports this mechanism, its
36133 documentation will explicitly say so. See for example the above
36134 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36135 format of the request is:
36138 @item qRelocInsn:@var{from};@var{to}
36140 This requests @value{GDBN} to copy instruction at address @var{from}
36141 to address @var{to}, possibly adjusted so that executing the
36142 instruction at @var{to} has the same effect as executing it at
36143 @var{from}. @value{GDBN} writes the adjusted instruction to target
36144 memory starting at @var{to}.
36149 @item qRelocInsn:@var{adjusted_size}
36150 Informs the stub the relocation is complete. @var{adjusted_size} is
36151 the length in bytes of resulting relocated instruction sequence.
36153 A badly formed request was detected, or an error was encountered while
36154 relocating the instruction.
36157 @node Host I/O Packets
36158 @section Host I/O Packets
36159 @cindex Host I/O, remote protocol
36160 @cindex file transfer, remote protocol
36162 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36163 operations on the far side of a remote link. For example, Host I/O is
36164 used to upload and download files to a remote target with its own
36165 filesystem. Host I/O uses the same constant values and data structure
36166 layout as the target-initiated File-I/O protocol. However, the
36167 Host I/O packets are structured differently. The target-initiated
36168 protocol relies on target memory to store parameters and buffers.
36169 Host I/O requests are initiated by @value{GDBN}, and the
36170 target's memory is not involved. @xref{File-I/O Remote Protocol
36171 Extension}, for more details on the target-initiated protocol.
36173 The Host I/O request packets all encode a single operation along with
36174 its arguments. They have this format:
36178 @item vFile:@var{operation}: @var{parameter}@dots{}
36179 @var{operation} is the name of the particular request; the target
36180 should compare the entire packet name up to the second colon when checking
36181 for a supported operation. The format of @var{parameter} depends on
36182 the operation. Numbers are always passed in hexadecimal. Negative
36183 numbers have an explicit minus sign (i.e.@: two's complement is not
36184 used). Strings (e.g.@: filenames) are encoded as a series of
36185 hexadecimal bytes. The last argument to a system call may be a
36186 buffer of escaped binary data (@pxref{Binary Data}).
36190 The valid responses to Host I/O packets are:
36194 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36195 @var{result} is the integer value returned by this operation, usually
36196 non-negative for success and -1 for errors. If an error has occured,
36197 @var{errno} will be included in the result. @var{errno} will have a
36198 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36199 operations which return data, @var{attachment} supplies the data as a
36200 binary buffer. Binary buffers in response packets are escaped in the
36201 normal way (@pxref{Binary Data}). See the individual packet
36202 documentation for the interpretation of @var{result} and
36206 An empty response indicates that this operation is not recognized.
36210 These are the supported Host I/O operations:
36213 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36214 Open a file at @var{pathname} and return a file descriptor for it, or
36215 return -1 if an error occurs. @var{pathname} is a string,
36216 @var{flags} is an integer indicating a mask of open flags
36217 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36218 of mode bits to use if the file is created (@pxref{mode_t Values}).
36219 @xref{open}, for details of the open flags and mode values.
36221 @item vFile:close: @var{fd}
36222 Close the open file corresponding to @var{fd} and return 0, or
36223 -1 if an error occurs.
36225 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36226 Read data from the open file corresponding to @var{fd}. Up to
36227 @var{count} bytes will be read from the file, starting at @var{offset}
36228 relative to the start of the file. The target may read fewer bytes;
36229 common reasons include packet size limits and an end-of-file
36230 condition. The number of bytes read is returned. Zero should only be
36231 returned for a successful read at the end of the file, or if
36232 @var{count} was zero.
36234 The data read should be returned as a binary attachment on success.
36235 If zero bytes were read, the response should include an empty binary
36236 attachment (i.e.@: a trailing semicolon). The return value is the
36237 number of target bytes read; the binary attachment may be longer if
36238 some characters were escaped.
36240 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36241 Write @var{data} (a binary buffer) to the open file corresponding
36242 to @var{fd}. Start the write at @var{offset} from the start of the
36243 file. Unlike many @code{write} system calls, there is no
36244 separate @var{count} argument; the length of @var{data} in the
36245 packet is used. @samp{vFile:write} returns the number of bytes written,
36246 which may be shorter than the length of @var{data}, or -1 if an
36249 @item vFile:unlink: @var{pathname}
36250 Delete the file at @var{pathname} on the target. Return 0,
36251 or -1 if an error occurs. @var{pathname} is a string.
36253 @item vFile:readlink: @var{filename}
36254 Read value of symbolic link @var{filename} on the target. Return
36255 the number of bytes read, or -1 if an error occurs.
36257 The data read should be returned as a binary attachment on success.
36258 If zero bytes were read, the response should include an empty binary
36259 attachment (i.e.@: a trailing semicolon). The return value is the
36260 number of target bytes read; the binary attachment may be longer if
36261 some characters were escaped.
36266 @section Interrupts
36267 @cindex interrupts (remote protocol)
36269 When a program on the remote target is running, @value{GDBN} may
36270 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36271 a @code{BREAK} followed by @code{g},
36272 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36274 The precise meaning of @code{BREAK} is defined by the transport
36275 mechanism and may, in fact, be undefined. @value{GDBN} does not
36276 currently define a @code{BREAK} mechanism for any of the network
36277 interfaces except for TCP, in which case @value{GDBN} sends the
36278 @code{telnet} BREAK sequence.
36280 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36281 transport mechanisms. It is represented by sending the single byte
36282 @code{0x03} without any of the usual packet overhead described in
36283 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36284 transmitted as part of a packet, it is considered to be packet data
36285 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36286 (@pxref{X packet}), used for binary downloads, may include an unescaped
36287 @code{0x03} as part of its packet.
36289 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36290 When Linux kernel receives this sequence from serial port,
36291 it stops execution and connects to gdb.
36293 Stubs are not required to recognize these interrupt mechanisms and the
36294 precise meaning associated with receipt of the interrupt is
36295 implementation defined. If the target supports debugging of multiple
36296 threads and/or processes, it should attempt to interrupt all
36297 currently-executing threads and processes.
36298 If the stub is successful at interrupting the
36299 running program, it should send one of the stop
36300 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36301 of successfully stopping the program in all-stop mode, and a stop reply
36302 for each stopped thread in non-stop mode.
36303 Interrupts received while the
36304 program is stopped are discarded.
36306 @node Notification Packets
36307 @section Notification Packets
36308 @cindex notification packets
36309 @cindex packets, notification
36311 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36312 packets that require no acknowledgment. Both the GDB and the stub
36313 may send notifications (although the only notifications defined at
36314 present are sent by the stub). Notifications carry information
36315 without incurring the round-trip latency of an acknowledgment, and so
36316 are useful for low-impact communications where occasional packet loss
36319 A notification packet has the form @samp{% @var{data} #
36320 @var{checksum}}, where @var{data} is the content of the notification,
36321 and @var{checksum} is a checksum of @var{data}, computed and formatted
36322 as for ordinary @value{GDBN} packets. A notification's @var{data}
36323 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36324 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36325 to acknowledge the notification's receipt or to report its corruption.
36327 Every notification's @var{data} begins with a name, which contains no
36328 colon characters, followed by a colon character.
36330 Recipients should silently ignore corrupted notifications and
36331 notifications they do not understand. Recipients should restart
36332 timeout periods on receipt of a well-formed notification, whether or
36333 not they understand it.
36335 Senders should only send the notifications described here when this
36336 protocol description specifies that they are permitted. In the
36337 future, we may extend the protocol to permit existing notifications in
36338 new contexts; this rule helps older senders avoid confusing newer
36341 (Older versions of @value{GDBN} ignore bytes received until they see
36342 the @samp{$} byte that begins an ordinary packet, so new stubs may
36343 transmit notifications without fear of confusing older clients. There
36344 are no notifications defined for @value{GDBN} to send at the moment, but we
36345 assume that most older stubs would ignore them, as well.)
36347 The following notification packets from the stub to @value{GDBN} are
36351 @item Stop: @var{reply}
36352 Report an asynchronous stop event in non-stop mode.
36353 The @var{reply} has the form of a stop reply, as
36354 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36355 for information on how these notifications are acknowledged by
36359 @node Remote Non-Stop
36360 @section Remote Protocol Support for Non-Stop Mode
36362 @value{GDBN}'s remote protocol supports non-stop debugging of
36363 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36364 supports non-stop mode, it should report that to @value{GDBN} by including
36365 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36367 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36368 establishing a new connection with the stub. Entering non-stop mode
36369 does not alter the state of any currently-running threads, but targets
36370 must stop all threads in any already-attached processes when entering
36371 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36372 probe the target state after a mode change.
36374 In non-stop mode, when an attached process encounters an event that
36375 would otherwise be reported with a stop reply, it uses the
36376 asynchronous notification mechanism (@pxref{Notification Packets}) to
36377 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36378 in all processes are stopped when a stop reply is sent, in non-stop
36379 mode only the thread reporting the stop event is stopped. That is,
36380 when reporting a @samp{S} or @samp{T} response to indicate completion
36381 of a step operation, hitting a breakpoint, or a fault, only the
36382 affected thread is stopped; any other still-running threads continue
36383 to run. When reporting a @samp{W} or @samp{X} response, all running
36384 threads belonging to other attached processes continue to run.
36386 Only one stop reply notification at a time may be pending; if
36387 additional stop events occur before @value{GDBN} has acknowledged the
36388 previous notification, they must be queued by the stub for later
36389 synchronous transmission in response to @samp{vStopped} packets from
36390 @value{GDBN}. Because the notification mechanism is unreliable,
36391 the stub is permitted to resend a stop reply notification
36392 if it believes @value{GDBN} may not have received it. @value{GDBN}
36393 ignores additional stop reply notifications received before it has
36394 finished processing a previous notification and the stub has completed
36395 sending any queued stop events.
36397 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36398 notification at any time. Specifically, they may appear when
36399 @value{GDBN} is not otherwise reading input from the stub, or when
36400 @value{GDBN} is expecting to read a normal synchronous response or a
36401 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36402 Notification packets are distinct from any other communication from
36403 the stub so there is no ambiguity.
36405 After receiving a stop reply notification, @value{GDBN} shall
36406 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36407 as a regular, synchronous request to the stub. Such acknowledgment
36408 is not required to happen immediately, as @value{GDBN} is permitted to
36409 send other, unrelated packets to the stub first, which the stub should
36412 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36413 stop events to report to @value{GDBN}, it shall respond by sending a
36414 normal stop reply response. @value{GDBN} shall then send another
36415 @samp{vStopped} packet to solicit further responses; again, it is
36416 permitted to send other, unrelated packets as well which the stub
36417 should process normally.
36419 If the stub receives a @samp{vStopped} packet and there are no
36420 additional stop events to report, the stub shall return an @samp{OK}
36421 response. At this point, if further stop events occur, the stub shall
36422 send a new stop reply notification, @value{GDBN} shall accept the
36423 notification, and the process shall be repeated.
36425 In non-stop mode, the target shall respond to the @samp{?} packet as
36426 follows. First, any incomplete stop reply notification/@samp{vStopped}
36427 sequence in progress is abandoned. The target must begin a new
36428 sequence reporting stop events for all stopped threads, whether or not
36429 it has previously reported those events to @value{GDBN}. The first
36430 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36431 subsequent stop replies are sent as responses to @samp{vStopped} packets
36432 using the mechanism described above. The target must not send
36433 asynchronous stop reply notifications until the sequence is complete.
36434 If all threads are running when the target receives the @samp{?} packet,
36435 or if the target is not attached to any process, it shall respond
36438 @node Packet Acknowledgment
36439 @section Packet Acknowledgment
36441 @cindex acknowledgment, for @value{GDBN} remote
36442 @cindex packet acknowledgment, for @value{GDBN} remote
36443 By default, when either the host or the target machine receives a packet,
36444 the first response expected is an acknowledgment: either @samp{+} (to indicate
36445 the package was received correctly) or @samp{-} (to request retransmission).
36446 This mechanism allows the @value{GDBN} remote protocol to operate over
36447 unreliable transport mechanisms, such as a serial line.
36449 In cases where the transport mechanism is itself reliable (such as a pipe or
36450 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36451 It may be desirable to disable them in that case to reduce communication
36452 overhead, or for other reasons. This can be accomplished by means of the
36453 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36455 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36456 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36457 and response format still includes the normal checksum, as described in
36458 @ref{Overview}, but the checksum may be ignored by the receiver.
36460 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36461 no-acknowledgment mode, it should report that to @value{GDBN}
36462 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36463 @pxref{qSupported}.
36464 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36465 disabled via the @code{set remote noack-packet off} command
36466 (@pxref{Remote Configuration}),
36467 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36468 Only then may the stub actually turn off packet acknowledgments.
36469 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36470 response, which can be safely ignored by the stub.
36472 Note that @code{set remote noack-packet} command only affects negotiation
36473 between @value{GDBN} and the stub when subsequent connections are made;
36474 it does not affect the protocol acknowledgment state for any current
36476 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36477 new connection is established,
36478 there is also no protocol request to re-enable the acknowledgments
36479 for the current connection, once disabled.
36484 Example sequence of a target being re-started. Notice how the restart
36485 does not get any direct output:
36490 @emph{target restarts}
36493 <- @code{T001:1234123412341234}
36497 Example sequence of a target being stepped by a single instruction:
36500 -> @code{G1445@dots{}}
36505 <- @code{T001:1234123412341234}
36509 <- @code{1455@dots{}}
36513 @node File-I/O Remote Protocol Extension
36514 @section File-I/O Remote Protocol Extension
36515 @cindex File-I/O remote protocol extension
36518 * File-I/O Overview::
36519 * Protocol Basics::
36520 * The F Request Packet::
36521 * The F Reply Packet::
36522 * The Ctrl-C Message::
36524 * List of Supported Calls::
36525 * Protocol-specific Representation of Datatypes::
36527 * File-I/O Examples::
36530 @node File-I/O Overview
36531 @subsection File-I/O Overview
36532 @cindex file-i/o overview
36534 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36535 target to use the host's file system and console I/O to perform various
36536 system calls. System calls on the target system are translated into a
36537 remote protocol packet to the host system, which then performs the needed
36538 actions and returns a response packet to the target system.
36539 This simulates file system operations even on targets that lack file systems.
36541 The protocol is defined to be independent of both the host and target systems.
36542 It uses its own internal representation of datatypes and values. Both
36543 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36544 translating the system-dependent value representations into the internal
36545 protocol representations when data is transmitted.
36547 The communication is synchronous. A system call is possible only when
36548 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36549 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36550 the target is stopped to allow deterministic access to the target's
36551 memory. Therefore File-I/O is not interruptible by target signals. On
36552 the other hand, it is possible to interrupt File-I/O by a user interrupt
36553 (@samp{Ctrl-C}) within @value{GDBN}.
36555 The target's request to perform a host system call does not finish
36556 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36557 after finishing the system call, the target returns to continuing the
36558 previous activity (continue, step). No additional continue or step
36559 request from @value{GDBN} is required.
36562 (@value{GDBP}) continue
36563 <- target requests 'system call X'
36564 target is stopped, @value{GDBN} executes system call
36565 -> @value{GDBN} returns result
36566 ... target continues, @value{GDBN} returns to wait for the target
36567 <- target hits breakpoint and sends a Txx packet
36570 The protocol only supports I/O on the console and to regular files on
36571 the host file system. Character or block special devices, pipes,
36572 named pipes, sockets or any other communication method on the host
36573 system are not supported by this protocol.
36575 File I/O is not supported in non-stop mode.
36577 @node Protocol Basics
36578 @subsection Protocol Basics
36579 @cindex protocol basics, file-i/o
36581 The File-I/O protocol uses the @code{F} packet as the request as well
36582 as reply packet. Since a File-I/O system call can only occur when
36583 @value{GDBN} is waiting for a response from the continuing or stepping target,
36584 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36585 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36586 This @code{F} packet contains all information needed to allow @value{GDBN}
36587 to call the appropriate host system call:
36591 A unique identifier for the requested system call.
36594 All parameters to the system call. Pointers are given as addresses
36595 in the target memory address space. Pointers to strings are given as
36596 pointer/length pair. Numerical values are given as they are.
36597 Numerical control flags are given in a protocol-specific representation.
36601 At this point, @value{GDBN} has to perform the following actions.
36605 If the parameters include pointer values to data needed as input to a
36606 system call, @value{GDBN} requests this data from the target with a
36607 standard @code{m} packet request. This additional communication has to be
36608 expected by the target implementation and is handled as any other @code{m}
36612 @value{GDBN} translates all value from protocol representation to host
36613 representation as needed. Datatypes are coerced into the host types.
36616 @value{GDBN} calls the system call.
36619 It then coerces datatypes back to protocol representation.
36622 If the system call is expected to return data in buffer space specified
36623 by pointer parameters to the call, the data is transmitted to the
36624 target using a @code{M} or @code{X} packet. This packet has to be expected
36625 by the target implementation and is handled as any other @code{M} or @code{X}
36630 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36631 necessary information for the target to continue. This at least contains
36638 @code{errno}, if has been changed by the system call.
36645 After having done the needed type and value coercion, the target continues
36646 the latest continue or step action.
36648 @node The F Request Packet
36649 @subsection The @code{F} Request Packet
36650 @cindex file-i/o request packet
36651 @cindex @code{F} request packet
36653 The @code{F} request packet has the following format:
36656 @item F@var{call-id},@var{parameter@dots{}}
36658 @var{call-id} is the identifier to indicate the host system call to be called.
36659 This is just the name of the function.
36661 @var{parameter@dots{}} are the parameters to the system call.
36662 Parameters are hexadecimal integer values, either the actual values in case
36663 of scalar datatypes, pointers to target buffer space in case of compound
36664 datatypes and unspecified memory areas, or pointer/length pairs in case
36665 of string parameters. These are appended to the @var{call-id} as a
36666 comma-delimited list. All values are transmitted in ASCII
36667 string representation, pointer/length pairs separated by a slash.
36673 @node The F Reply Packet
36674 @subsection The @code{F} Reply Packet
36675 @cindex file-i/o reply packet
36676 @cindex @code{F} reply packet
36678 The @code{F} reply packet has the following format:
36682 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36684 @var{retcode} is the return code of the system call as hexadecimal value.
36686 @var{errno} is the @code{errno} set by the call, in protocol-specific
36688 This parameter can be omitted if the call was successful.
36690 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36691 case, @var{errno} must be sent as well, even if the call was successful.
36692 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36699 or, if the call was interrupted before the host call has been performed:
36706 assuming 4 is the protocol-specific representation of @code{EINTR}.
36711 @node The Ctrl-C Message
36712 @subsection The @samp{Ctrl-C} Message
36713 @cindex ctrl-c message, in file-i/o protocol
36715 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36716 reply packet (@pxref{The F Reply Packet}),
36717 the target should behave as if it had
36718 gotten a break message. The meaning for the target is ``system call
36719 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36720 (as with a break message) and return to @value{GDBN} with a @code{T02}
36723 It's important for the target to know in which
36724 state the system call was interrupted. There are two possible cases:
36728 The system call hasn't been performed on the host yet.
36731 The system call on the host has been finished.
36735 These two states can be distinguished by the target by the value of the
36736 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36737 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36738 on POSIX systems. In any other case, the target may presume that the
36739 system call has been finished --- successfully or not --- and should behave
36740 as if the break message arrived right after the system call.
36742 @value{GDBN} must behave reliably. If the system call has not been called
36743 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36744 @code{errno} in the packet. If the system call on the host has been finished
36745 before the user requests a break, the full action must be finished by
36746 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36747 The @code{F} packet may only be sent when either nothing has happened
36748 or the full action has been completed.
36751 @subsection Console I/O
36752 @cindex console i/o as part of file-i/o
36754 By default and if not explicitly closed by the target system, the file
36755 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36756 on the @value{GDBN} console is handled as any other file output operation
36757 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36758 by @value{GDBN} so that after the target read request from file descriptor
36759 0 all following typing is buffered until either one of the following
36764 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36766 system call is treated as finished.
36769 The user presses @key{RET}. This is treated as end of input with a trailing
36773 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36774 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36778 If the user has typed more characters than fit in the buffer given to
36779 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36780 either another @code{read(0, @dots{})} is requested by the target, or debugging
36781 is stopped at the user's request.
36784 @node List of Supported Calls
36785 @subsection List of Supported Calls
36786 @cindex list of supported file-i/o calls
36803 @unnumberedsubsubsec open
36804 @cindex open, file-i/o system call
36809 int open(const char *pathname, int flags);
36810 int open(const char *pathname, int flags, mode_t mode);
36814 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36817 @var{flags} is the bitwise @code{OR} of the following values:
36821 If the file does not exist it will be created. The host
36822 rules apply as far as file ownership and time stamps
36826 When used with @code{O_CREAT}, if the file already exists it is
36827 an error and open() fails.
36830 If the file already exists and the open mode allows
36831 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36832 truncated to zero length.
36835 The file is opened in append mode.
36838 The file is opened for reading only.
36841 The file is opened for writing only.
36844 The file is opened for reading and writing.
36848 Other bits are silently ignored.
36852 @var{mode} is the bitwise @code{OR} of the following values:
36856 User has read permission.
36859 User has write permission.
36862 Group has read permission.
36865 Group has write permission.
36868 Others have read permission.
36871 Others have write permission.
36875 Other bits are silently ignored.
36878 @item Return value:
36879 @code{open} returns the new file descriptor or -1 if an error
36886 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36889 @var{pathname} refers to a directory.
36892 The requested access is not allowed.
36895 @var{pathname} was too long.
36898 A directory component in @var{pathname} does not exist.
36901 @var{pathname} refers to a device, pipe, named pipe or socket.
36904 @var{pathname} refers to a file on a read-only filesystem and
36905 write access was requested.
36908 @var{pathname} is an invalid pointer value.
36911 No space on device to create the file.
36914 The process already has the maximum number of files open.
36917 The limit on the total number of files open on the system
36921 The call was interrupted by the user.
36927 @unnumberedsubsubsec close
36928 @cindex close, file-i/o system call
36937 @samp{Fclose,@var{fd}}
36939 @item Return value:
36940 @code{close} returns zero on success, or -1 if an error occurred.
36946 @var{fd} isn't a valid open file descriptor.
36949 The call was interrupted by the user.
36955 @unnumberedsubsubsec read
36956 @cindex read, file-i/o system call
36961 int read(int fd, void *buf, unsigned int count);
36965 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36967 @item Return value:
36968 On success, the number of bytes read is returned.
36969 Zero indicates end of file. If count is zero, read
36970 returns zero as well. On error, -1 is returned.
36976 @var{fd} is not a valid file descriptor or is not open for
36980 @var{bufptr} is an invalid pointer value.
36983 The call was interrupted by the user.
36989 @unnumberedsubsubsec write
36990 @cindex write, file-i/o system call
36995 int write(int fd, const void *buf, unsigned int count);
36999 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37001 @item Return value:
37002 On success, the number of bytes written are returned.
37003 Zero indicates nothing was written. On error, -1
37010 @var{fd} is not a valid file descriptor or is not open for
37014 @var{bufptr} is an invalid pointer value.
37017 An attempt was made to write a file that exceeds the
37018 host-specific maximum file size allowed.
37021 No space on device to write the data.
37024 The call was interrupted by the user.
37030 @unnumberedsubsubsec lseek
37031 @cindex lseek, file-i/o system call
37036 long lseek (int fd, long offset, int flag);
37040 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37042 @var{flag} is one of:
37046 The offset is set to @var{offset} bytes.
37049 The offset is set to its current location plus @var{offset}
37053 The offset is set to the size of the file plus @var{offset}
37057 @item Return value:
37058 On success, the resulting unsigned offset in bytes from
37059 the beginning of the file is returned. Otherwise, a
37060 value of -1 is returned.
37066 @var{fd} is not a valid open file descriptor.
37069 @var{fd} is associated with the @value{GDBN} console.
37072 @var{flag} is not a proper value.
37075 The call was interrupted by the user.
37081 @unnumberedsubsubsec rename
37082 @cindex rename, file-i/o system call
37087 int rename(const char *oldpath, const char *newpath);
37091 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37093 @item Return value:
37094 On success, zero is returned. On error, -1 is returned.
37100 @var{newpath} is an existing directory, but @var{oldpath} is not a
37104 @var{newpath} is a non-empty directory.
37107 @var{oldpath} or @var{newpath} is a directory that is in use by some
37111 An attempt was made to make a directory a subdirectory
37115 A component used as a directory in @var{oldpath} or new
37116 path is not a directory. Or @var{oldpath} is a directory
37117 and @var{newpath} exists but is not a directory.
37120 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37123 No access to the file or the path of the file.
37127 @var{oldpath} or @var{newpath} was too long.
37130 A directory component in @var{oldpath} or @var{newpath} does not exist.
37133 The file is on a read-only filesystem.
37136 The device containing the file has no room for the new
37140 The call was interrupted by the user.
37146 @unnumberedsubsubsec unlink
37147 @cindex unlink, file-i/o system call
37152 int unlink(const char *pathname);
37156 @samp{Funlink,@var{pathnameptr}/@var{len}}
37158 @item Return value:
37159 On success, zero is returned. On error, -1 is returned.
37165 No access to the file or the path of the file.
37168 The system does not allow unlinking of directories.
37171 The file @var{pathname} cannot be unlinked because it's
37172 being used by another process.
37175 @var{pathnameptr} is an invalid pointer value.
37178 @var{pathname} was too long.
37181 A directory component in @var{pathname} does not exist.
37184 A component of the path is not a directory.
37187 The file is on a read-only filesystem.
37190 The call was interrupted by the user.
37196 @unnumberedsubsubsec stat/fstat
37197 @cindex fstat, file-i/o system call
37198 @cindex stat, file-i/o system call
37203 int stat(const char *pathname, struct stat *buf);
37204 int fstat(int fd, struct stat *buf);
37208 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37209 @samp{Ffstat,@var{fd},@var{bufptr}}
37211 @item Return value:
37212 On success, zero is returned. On error, -1 is returned.
37218 @var{fd} is not a valid open file.
37221 A directory component in @var{pathname} does not exist or the
37222 path is an empty string.
37225 A component of the path is not a directory.
37228 @var{pathnameptr} is an invalid pointer value.
37231 No access to the file or the path of the file.
37234 @var{pathname} was too long.
37237 The call was interrupted by the user.
37243 @unnumberedsubsubsec gettimeofday
37244 @cindex gettimeofday, file-i/o system call
37249 int gettimeofday(struct timeval *tv, void *tz);
37253 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37255 @item Return value:
37256 On success, 0 is returned, -1 otherwise.
37262 @var{tz} is a non-NULL pointer.
37265 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37271 @unnumberedsubsubsec isatty
37272 @cindex isatty, file-i/o system call
37277 int isatty(int fd);
37281 @samp{Fisatty,@var{fd}}
37283 @item Return value:
37284 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37290 The call was interrupted by the user.
37295 Note that the @code{isatty} call is treated as a special case: it returns
37296 1 to the target if the file descriptor is attached
37297 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37298 would require implementing @code{ioctl} and would be more complex than
37303 @unnumberedsubsubsec system
37304 @cindex system, file-i/o system call
37309 int system(const char *command);
37313 @samp{Fsystem,@var{commandptr}/@var{len}}
37315 @item Return value:
37316 If @var{len} is zero, the return value indicates whether a shell is
37317 available. A zero return value indicates a shell is not available.
37318 For non-zero @var{len}, the value returned is -1 on error and the
37319 return status of the command otherwise. Only the exit status of the
37320 command is returned, which is extracted from the host's @code{system}
37321 return value by calling @code{WEXITSTATUS(retval)}. In case
37322 @file{/bin/sh} could not be executed, 127 is returned.
37328 The call was interrupted by the user.
37333 @value{GDBN} takes over the full task of calling the necessary host calls
37334 to perform the @code{system} call. The return value of @code{system} on
37335 the host is simplified before it's returned
37336 to the target. Any termination signal information from the child process
37337 is discarded, and the return value consists
37338 entirely of the exit status of the called command.
37340 Due to security concerns, the @code{system} call is by default refused
37341 by @value{GDBN}. The user has to allow this call explicitly with the
37342 @code{set remote system-call-allowed 1} command.
37345 @item set remote system-call-allowed
37346 @kindex set remote system-call-allowed
37347 Control whether to allow the @code{system} calls in the File I/O
37348 protocol for the remote target. The default is zero (disabled).
37350 @item show remote system-call-allowed
37351 @kindex show remote system-call-allowed
37352 Show whether the @code{system} calls are allowed in the File I/O
37356 @node Protocol-specific Representation of Datatypes
37357 @subsection Protocol-specific Representation of Datatypes
37358 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37361 * Integral Datatypes::
37363 * Memory Transfer::
37368 @node Integral Datatypes
37369 @unnumberedsubsubsec Integral Datatypes
37370 @cindex integral datatypes, in file-i/o protocol
37372 The integral datatypes used in the system calls are @code{int},
37373 @code{unsigned int}, @code{long}, @code{unsigned long},
37374 @code{mode_t}, and @code{time_t}.
37376 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37377 implemented as 32 bit values in this protocol.
37379 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37381 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37382 in @file{limits.h}) to allow range checking on host and target.
37384 @code{time_t} datatypes are defined as seconds since the Epoch.
37386 All integral datatypes transferred as part of a memory read or write of a
37387 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37390 @node Pointer Values
37391 @unnumberedsubsubsec Pointer Values
37392 @cindex pointer values, in file-i/o protocol
37394 Pointers to target data are transmitted as they are. An exception
37395 is made for pointers to buffers for which the length isn't
37396 transmitted as part of the function call, namely strings. Strings
37397 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37404 which is a pointer to data of length 18 bytes at position 0x1aaf.
37405 The length is defined as the full string length in bytes, including
37406 the trailing null byte. For example, the string @code{"hello world"}
37407 at address 0x123456 is transmitted as
37413 @node Memory Transfer
37414 @unnumberedsubsubsec Memory Transfer
37415 @cindex memory transfer, in file-i/o protocol
37417 Structured data which is transferred using a memory read or write (for
37418 example, a @code{struct stat}) is expected to be in a protocol-specific format
37419 with all scalar multibyte datatypes being big endian. Translation to
37420 this representation needs to be done both by the target before the @code{F}
37421 packet is sent, and by @value{GDBN} before
37422 it transfers memory to the target. Transferred pointers to structured
37423 data should point to the already-coerced data at any time.
37427 @unnumberedsubsubsec struct stat
37428 @cindex struct stat, in file-i/o protocol
37430 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37431 is defined as follows:
37435 unsigned int st_dev; /* device */
37436 unsigned int st_ino; /* inode */
37437 mode_t st_mode; /* protection */
37438 unsigned int st_nlink; /* number of hard links */
37439 unsigned int st_uid; /* user ID of owner */
37440 unsigned int st_gid; /* group ID of owner */
37441 unsigned int st_rdev; /* device type (if inode device) */
37442 unsigned long st_size; /* total size, in bytes */
37443 unsigned long st_blksize; /* blocksize for filesystem I/O */
37444 unsigned long st_blocks; /* number of blocks allocated */
37445 time_t st_atime; /* time of last access */
37446 time_t st_mtime; /* time of last modification */
37447 time_t st_ctime; /* time of last change */
37451 The integral datatypes conform to the definitions given in the
37452 appropriate section (see @ref{Integral Datatypes}, for details) so this
37453 structure is of size 64 bytes.
37455 The values of several fields have a restricted meaning and/or
37461 A value of 0 represents a file, 1 the console.
37464 No valid meaning for the target. Transmitted unchanged.
37467 Valid mode bits are described in @ref{Constants}. Any other
37468 bits have currently no meaning for the target.
37473 No valid meaning for the target. Transmitted unchanged.
37478 These values have a host and file system dependent
37479 accuracy. Especially on Windows hosts, the file system may not
37480 support exact timing values.
37483 The target gets a @code{struct stat} of the above representation and is
37484 responsible for coercing it to the target representation before
37487 Note that due to size differences between the host, target, and protocol
37488 representations of @code{struct stat} members, these members could eventually
37489 get truncated on the target.
37491 @node struct timeval
37492 @unnumberedsubsubsec struct timeval
37493 @cindex struct timeval, in file-i/o protocol
37495 The buffer of type @code{struct timeval} used by the File-I/O protocol
37496 is defined as follows:
37500 time_t tv_sec; /* second */
37501 long tv_usec; /* microsecond */
37505 The integral datatypes conform to the definitions given in the
37506 appropriate section (see @ref{Integral Datatypes}, for details) so this
37507 structure is of size 8 bytes.
37510 @subsection Constants
37511 @cindex constants, in file-i/o protocol
37513 The following values are used for the constants inside of the
37514 protocol. @value{GDBN} and target are responsible for translating these
37515 values before and after the call as needed.
37526 @unnumberedsubsubsec Open Flags
37527 @cindex open flags, in file-i/o protocol
37529 All values are given in hexadecimal representation.
37541 @node mode_t Values
37542 @unnumberedsubsubsec mode_t Values
37543 @cindex mode_t values, in file-i/o protocol
37545 All values are given in octal representation.
37562 @unnumberedsubsubsec Errno Values
37563 @cindex errno values, in file-i/o protocol
37565 All values are given in decimal representation.
37590 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37591 any error value not in the list of supported error numbers.
37594 @unnumberedsubsubsec Lseek Flags
37595 @cindex lseek flags, in file-i/o protocol
37604 @unnumberedsubsubsec Limits
37605 @cindex limits, in file-i/o protocol
37607 All values are given in decimal representation.
37610 INT_MIN -2147483648
37612 UINT_MAX 4294967295
37613 LONG_MIN -9223372036854775808
37614 LONG_MAX 9223372036854775807
37615 ULONG_MAX 18446744073709551615
37618 @node File-I/O Examples
37619 @subsection File-I/O Examples
37620 @cindex file-i/o examples
37622 Example sequence of a write call, file descriptor 3, buffer is at target
37623 address 0x1234, 6 bytes should be written:
37626 <- @code{Fwrite,3,1234,6}
37627 @emph{request memory read from target}
37630 @emph{return "6 bytes written"}
37634 Example sequence of a read call, file descriptor 3, buffer is at target
37635 address 0x1234, 6 bytes should be read:
37638 <- @code{Fread,3,1234,6}
37639 @emph{request memory write to target}
37640 -> @code{X1234,6:XXXXXX}
37641 @emph{return "6 bytes read"}
37645 Example sequence of a read call, call fails on the host due to invalid
37646 file descriptor (@code{EBADF}):
37649 <- @code{Fread,3,1234,6}
37653 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37657 <- @code{Fread,3,1234,6}
37662 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37666 <- @code{Fread,3,1234,6}
37667 -> @code{X1234,6:XXXXXX}
37671 @node Library List Format
37672 @section Library List Format
37673 @cindex library list format, remote protocol
37675 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37676 same process as your application to manage libraries. In this case,
37677 @value{GDBN} can use the loader's symbol table and normal memory
37678 operations to maintain a list of shared libraries. On other
37679 platforms, the operating system manages loaded libraries.
37680 @value{GDBN} can not retrieve the list of currently loaded libraries
37681 through memory operations, so it uses the @samp{qXfer:libraries:read}
37682 packet (@pxref{qXfer library list read}) instead. The remote stub
37683 queries the target's operating system and reports which libraries
37686 The @samp{qXfer:libraries:read} packet returns an XML document which
37687 lists loaded libraries and their offsets. Each library has an
37688 associated name and one or more segment or section base addresses,
37689 which report where the library was loaded in memory.
37691 For the common case of libraries that are fully linked binaries, the
37692 library should have a list of segments. If the target supports
37693 dynamic linking of a relocatable object file, its library XML element
37694 should instead include a list of allocated sections. The segment or
37695 section bases are start addresses, not relocation offsets; they do not
37696 depend on the library's link-time base addresses.
37698 @value{GDBN} must be linked with the Expat library to support XML
37699 library lists. @xref{Expat}.
37701 A simple memory map, with one loaded library relocated by a single
37702 offset, looks like this:
37706 <library name="/lib/libc.so.6">
37707 <segment address="0x10000000"/>
37712 Another simple memory map, with one loaded library with three
37713 allocated sections (.text, .data, .bss), looks like this:
37717 <library name="sharedlib.o">
37718 <section address="0x10000000"/>
37719 <section address="0x20000000"/>
37720 <section address="0x30000000"/>
37725 The format of a library list is described by this DTD:
37728 <!-- library-list: Root element with versioning -->
37729 <!ELEMENT library-list (library)*>
37730 <!ATTLIST library-list version CDATA #FIXED "1.0">
37731 <!ELEMENT library (segment*, section*)>
37732 <!ATTLIST library name CDATA #REQUIRED>
37733 <!ELEMENT segment EMPTY>
37734 <!ATTLIST segment address CDATA #REQUIRED>
37735 <!ELEMENT section EMPTY>
37736 <!ATTLIST section address CDATA #REQUIRED>
37739 In addition, segments and section descriptors cannot be mixed within a
37740 single library element, and you must supply at least one segment or
37741 section for each library.
37743 @node Library List Format for SVR4 Targets
37744 @section Library List Format for SVR4 Targets
37745 @cindex library list format, remote protocol
37747 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37748 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37749 shared libraries. Still a special library list provided by this packet is
37750 more efficient for the @value{GDBN} remote protocol.
37752 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37753 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37754 target, the following parameters are reported:
37758 @code{name}, the absolute file name from the @code{l_name} field of
37759 @code{struct link_map}.
37761 @code{lm} with address of @code{struct link_map} used for TLS
37762 (Thread Local Storage) access.
37764 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37765 @code{struct link_map}. For prelinked libraries this is not an absolute
37766 memory address. It is a displacement of absolute memory address against
37767 address the file was prelinked to during the library load.
37769 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37772 Additionally the single @code{main-lm} attribute specifies address of
37773 @code{struct link_map} used for the main executable. This parameter is used
37774 for TLS access and its presence is optional.
37776 @value{GDBN} must be linked with the Expat library to support XML
37777 SVR4 library lists. @xref{Expat}.
37779 A simple memory map, with two loaded libraries (which do not use prelink),
37783 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37784 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37786 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37788 </library-list-svr>
37791 The format of an SVR4 library list is described by this DTD:
37794 <!-- library-list-svr4: Root element with versioning -->
37795 <!ELEMENT library-list-svr4 (library)*>
37796 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37797 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37798 <!ELEMENT library EMPTY>
37799 <!ATTLIST library name CDATA #REQUIRED>
37800 <!ATTLIST library lm CDATA #REQUIRED>
37801 <!ATTLIST library l_addr CDATA #REQUIRED>
37802 <!ATTLIST library l_ld CDATA #REQUIRED>
37805 @node Memory Map Format
37806 @section Memory Map Format
37807 @cindex memory map format
37809 To be able to write into flash memory, @value{GDBN} needs to obtain a
37810 memory map from the target. This section describes the format of the
37813 The memory map is obtained using the @samp{qXfer:memory-map:read}
37814 (@pxref{qXfer memory map read}) packet and is an XML document that
37815 lists memory regions.
37817 @value{GDBN} must be linked with the Expat library to support XML
37818 memory maps. @xref{Expat}.
37820 The top-level structure of the document is shown below:
37823 <?xml version="1.0"?>
37824 <!DOCTYPE memory-map
37825 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37826 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37832 Each region can be either:
37837 A region of RAM starting at @var{addr} and extending for @var{length}
37841 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37846 A region of read-only memory:
37849 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37854 A region of flash memory, with erasure blocks @var{blocksize}
37858 <memory type="flash" start="@var{addr}" length="@var{length}">
37859 <property name="blocksize">@var{blocksize}</property>
37865 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37866 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37867 packets to write to addresses in such ranges.
37869 The formal DTD for memory map format is given below:
37872 <!-- ................................................... -->
37873 <!-- Memory Map XML DTD ................................ -->
37874 <!-- File: memory-map.dtd .............................. -->
37875 <!-- .................................... .............. -->
37876 <!-- memory-map.dtd -->
37877 <!-- memory-map: Root element with versioning -->
37878 <!ELEMENT memory-map (memory | property)>
37879 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37880 <!ELEMENT memory (property)>
37881 <!-- memory: Specifies a memory region,
37882 and its type, or device. -->
37883 <!ATTLIST memory type CDATA #REQUIRED
37884 start CDATA #REQUIRED
37885 length CDATA #REQUIRED
37886 device CDATA #IMPLIED>
37887 <!-- property: Generic attribute tag -->
37888 <!ELEMENT property (#PCDATA | property)*>
37889 <!ATTLIST property name CDATA #REQUIRED>
37892 @node Thread List Format
37893 @section Thread List Format
37894 @cindex thread list format
37896 To efficiently update the list of threads and their attributes,
37897 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37898 (@pxref{qXfer threads read}) and obtains the XML document with
37899 the following structure:
37902 <?xml version="1.0"?>
37904 <thread id="id" core="0">
37905 ... description ...
37910 Each @samp{thread} element must have the @samp{id} attribute that
37911 identifies the thread (@pxref{thread-id syntax}). The
37912 @samp{core} attribute, if present, specifies which processor core
37913 the thread was last executing on. The content of the of @samp{thread}
37914 element is interpreted as human-readable auxilliary information.
37916 @node Traceframe Info Format
37917 @section Traceframe Info Format
37918 @cindex traceframe info format
37920 To be able to know which objects in the inferior can be examined when
37921 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37922 memory ranges, registers and trace state variables that have been
37923 collected in a traceframe.
37925 This list is obtained using the @samp{qXfer:traceframe-info:read}
37926 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37928 @value{GDBN} must be linked with the Expat library to support XML
37929 traceframe info discovery. @xref{Expat}.
37931 The top-level structure of the document is shown below:
37934 <?xml version="1.0"?>
37935 <!DOCTYPE traceframe-info
37936 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37937 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37943 Each traceframe block can be either:
37948 A region of collected memory starting at @var{addr} and extending for
37949 @var{length} bytes from there:
37952 <memory start="@var{addr}" length="@var{length}"/>
37957 The formal DTD for the traceframe info format is given below:
37960 <!ELEMENT traceframe-info (memory)* >
37961 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37963 <!ELEMENT memory EMPTY>
37964 <!ATTLIST memory start CDATA #REQUIRED
37965 length CDATA #REQUIRED>
37968 @include agentexpr.texi
37970 @node Target Descriptions
37971 @appendix Target Descriptions
37972 @cindex target descriptions
37974 One of the challenges of using @value{GDBN} to debug embedded systems
37975 is that there are so many minor variants of each processor
37976 architecture in use. It is common practice for vendors to start with
37977 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37978 and then make changes to adapt it to a particular market niche. Some
37979 architectures have hundreds of variants, available from dozens of
37980 vendors. This leads to a number of problems:
37984 With so many different customized processors, it is difficult for
37985 the @value{GDBN} maintainers to keep up with the changes.
37987 Since individual variants may have short lifetimes or limited
37988 audiences, it may not be worthwhile to carry information about every
37989 variant in the @value{GDBN} source tree.
37991 When @value{GDBN} does support the architecture of the embedded system
37992 at hand, the task of finding the correct architecture name to give the
37993 @command{set architecture} command can be error-prone.
37996 To address these problems, the @value{GDBN} remote protocol allows a
37997 target system to not only identify itself to @value{GDBN}, but to
37998 actually describe its own features. This lets @value{GDBN} support
37999 processor variants it has never seen before --- to the extent that the
38000 descriptions are accurate, and that @value{GDBN} understands them.
38002 @value{GDBN} must be linked with the Expat library to support XML
38003 target descriptions. @xref{Expat}.
38006 * Retrieving Descriptions:: How descriptions are fetched from a target.
38007 * Target Description Format:: The contents of a target description.
38008 * Predefined Target Types:: Standard types available for target
38010 * Standard Target Features:: Features @value{GDBN} knows about.
38013 @node Retrieving Descriptions
38014 @section Retrieving Descriptions
38016 Target descriptions can be read from the target automatically, or
38017 specified by the user manually. The default behavior is to read the
38018 description from the target. @value{GDBN} retrieves it via the remote
38019 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38020 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38021 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38022 XML document, of the form described in @ref{Target Description
38025 Alternatively, you can specify a file to read for the target description.
38026 If a file is set, the target will not be queried. The commands to
38027 specify a file are:
38030 @cindex set tdesc filename
38031 @item set tdesc filename @var{path}
38032 Read the target description from @var{path}.
38034 @cindex unset tdesc filename
38035 @item unset tdesc filename
38036 Do not read the XML target description from a file. @value{GDBN}
38037 will use the description supplied by the current target.
38039 @cindex show tdesc filename
38040 @item show tdesc filename
38041 Show the filename to read for a target description, if any.
38045 @node Target Description Format
38046 @section Target Description Format
38047 @cindex target descriptions, XML format
38049 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38050 document which complies with the Document Type Definition provided in
38051 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38052 means you can use generally available tools like @command{xmllint} to
38053 check that your feature descriptions are well-formed and valid.
38054 However, to help people unfamiliar with XML write descriptions for
38055 their targets, we also describe the grammar here.
38057 Target descriptions can identify the architecture of the remote target
38058 and (for some architectures) provide information about custom register
38059 sets. They can also identify the OS ABI of the remote target.
38060 @value{GDBN} can use this information to autoconfigure for your
38061 target, or to warn you if you connect to an unsupported target.
38063 Here is a simple target description:
38066 <target version="1.0">
38067 <architecture>i386:x86-64</architecture>
38072 This minimal description only says that the target uses
38073 the x86-64 architecture.
38075 A target description has the following overall form, with [ ] marking
38076 optional elements and @dots{} marking repeatable elements. The elements
38077 are explained further below.
38080 <?xml version="1.0"?>
38081 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38082 <target version="1.0">
38083 @r{[}@var{architecture}@r{]}
38084 @r{[}@var{osabi}@r{]}
38085 @r{[}@var{compatible}@r{]}
38086 @r{[}@var{feature}@dots{}@r{]}
38091 The description is generally insensitive to whitespace and line
38092 breaks, under the usual common-sense rules. The XML version
38093 declaration and document type declaration can generally be omitted
38094 (@value{GDBN} does not require them), but specifying them may be
38095 useful for XML validation tools. The @samp{version} attribute for
38096 @samp{<target>} may also be omitted, but we recommend
38097 including it; if future versions of @value{GDBN} use an incompatible
38098 revision of @file{gdb-target.dtd}, they will detect and report
38099 the version mismatch.
38101 @subsection Inclusion
38102 @cindex target descriptions, inclusion
38105 @cindex <xi:include>
38108 It can sometimes be valuable to split a target description up into
38109 several different annexes, either for organizational purposes, or to
38110 share files between different possible target descriptions. You can
38111 divide a description into multiple files by replacing any element of
38112 the target description with an inclusion directive of the form:
38115 <xi:include href="@var{document}"/>
38119 When @value{GDBN} encounters an element of this form, it will retrieve
38120 the named XML @var{document}, and replace the inclusion directive with
38121 the contents of that document. If the current description was read
38122 using @samp{qXfer}, then so will be the included document;
38123 @var{document} will be interpreted as the name of an annex. If the
38124 current description was read from a file, @value{GDBN} will look for
38125 @var{document} as a file in the same directory where it found the
38126 original description.
38128 @subsection Architecture
38129 @cindex <architecture>
38131 An @samp{<architecture>} element has this form:
38134 <architecture>@var{arch}</architecture>
38137 @var{arch} is one of the architectures from the set accepted by
38138 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38141 @cindex @code{<osabi>}
38143 This optional field was introduced in @value{GDBN} version 7.0.
38144 Previous versions of @value{GDBN} ignore it.
38146 An @samp{<osabi>} element has this form:
38149 <osabi>@var{abi-name}</osabi>
38152 @var{abi-name} is an OS ABI name from the same selection accepted by
38153 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38155 @subsection Compatible Architecture
38156 @cindex @code{<compatible>}
38158 This optional field was introduced in @value{GDBN} version 7.0.
38159 Previous versions of @value{GDBN} ignore it.
38161 A @samp{<compatible>} element has this form:
38164 <compatible>@var{arch}</compatible>
38167 @var{arch} is one of the architectures from the set accepted by
38168 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38170 A @samp{<compatible>} element is used to specify that the target
38171 is able to run binaries in some other than the main target architecture
38172 given by the @samp{<architecture>} element. For example, on the
38173 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38174 or @code{powerpc:common64}, but the system is able to run binaries
38175 in the @code{spu} architecture as well. The way to describe this
38176 capability with @samp{<compatible>} is as follows:
38179 <architecture>powerpc:common</architecture>
38180 <compatible>spu</compatible>
38183 @subsection Features
38186 Each @samp{<feature>} describes some logical portion of the target
38187 system. Features are currently used to describe available CPU
38188 registers and the types of their contents. A @samp{<feature>} element
38192 <feature name="@var{name}">
38193 @r{[}@var{type}@dots{}@r{]}
38199 Each feature's name should be unique within the description. The name
38200 of a feature does not matter unless @value{GDBN} has some special
38201 knowledge of the contents of that feature; if it does, the feature
38202 should have its standard name. @xref{Standard Target Features}.
38206 Any register's value is a collection of bits which @value{GDBN} must
38207 interpret. The default interpretation is a two's complement integer,
38208 but other types can be requested by name in the register description.
38209 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38210 Target Types}), and the description can define additional composite types.
38212 Each type element must have an @samp{id} attribute, which gives
38213 a unique (within the containing @samp{<feature>}) name to the type.
38214 Types must be defined before they are used.
38217 Some targets offer vector registers, which can be treated as arrays
38218 of scalar elements. These types are written as @samp{<vector>} elements,
38219 specifying the array element type, @var{type}, and the number of elements,
38223 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38227 If a register's value is usefully viewed in multiple ways, define it
38228 with a union type containing the useful representations. The
38229 @samp{<union>} element contains one or more @samp{<field>} elements,
38230 each of which has a @var{name} and a @var{type}:
38233 <union id="@var{id}">
38234 <field name="@var{name}" type="@var{type}"/>
38240 If a register's value is composed from several separate values, define
38241 it with a structure type. There are two forms of the @samp{<struct>}
38242 element; a @samp{<struct>} element must either contain only bitfields
38243 or contain no bitfields. If the structure contains only bitfields,
38244 its total size in bytes must be specified, each bitfield must have an
38245 explicit start and end, and bitfields are automatically assigned an
38246 integer type. The field's @var{start} should be less than or
38247 equal to its @var{end}, and zero represents the least significant bit.
38250 <struct id="@var{id}" size="@var{size}">
38251 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38256 If the structure contains no bitfields, then each field has an
38257 explicit type, and no implicit padding is added.
38260 <struct id="@var{id}">
38261 <field name="@var{name}" type="@var{type}"/>
38267 If a register's value is a series of single-bit flags, define it with
38268 a flags type. The @samp{<flags>} element has an explicit @var{size}
38269 and contains one or more @samp{<field>} elements. Each field has a
38270 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38274 <flags id="@var{id}" size="@var{size}">
38275 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38280 @subsection Registers
38283 Each register is represented as an element with this form:
38286 <reg name="@var{name}"
38287 bitsize="@var{size}"
38288 @r{[}regnum="@var{num}"@r{]}
38289 @r{[}save-restore="@var{save-restore}"@r{]}
38290 @r{[}type="@var{type}"@r{]}
38291 @r{[}group="@var{group}"@r{]}/>
38295 The components are as follows:
38300 The register's name; it must be unique within the target description.
38303 The register's size, in bits.
38306 The register's number. If omitted, a register's number is one greater
38307 than that of the previous register (either in the current feature or in
38308 a preceding feature); the first register in the target description
38309 defaults to zero. This register number is used to read or write
38310 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38311 packets, and registers appear in the @code{g} and @code{G} packets
38312 in order of increasing register number.
38315 Whether the register should be preserved across inferior function
38316 calls; this must be either @code{yes} or @code{no}. The default is
38317 @code{yes}, which is appropriate for most registers except for
38318 some system control registers; this is not related to the target's
38322 The type of the register. @var{type} may be a predefined type, a type
38323 defined in the current feature, or one of the special types @code{int}
38324 and @code{float}. @code{int} is an integer type of the correct size
38325 for @var{bitsize}, and @code{float} is a floating point type (in the
38326 architecture's normal floating point format) of the correct size for
38327 @var{bitsize}. The default is @code{int}.
38330 The register group to which this register belongs. @var{group} must
38331 be either @code{general}, @code{float}, or @code{vector}. If no
38332 @var{group} is specified, @value{GDBN} will not display the register
38333 in @code{info registers}.
38337 @node Predefined Target Types
38338 @section Predefined Target Types
38339 @cindex target descriptions, predefined types
38341 Type definitions in the self-description can build up composite types
38342 from basic building blocks, but can not define fundamental types. Instead,
38343 standard identifiers are provided by @value{GDBN} for the fundamental
38344 types. The currently supported types are:
38353 Signed integer types holding the specified number of bits.
38360 Unsigned integer types holding the specified number of bits.
38364 Pointers to unspecified code and data. The program counter and
38365 any dedicated return address register may be marked as code
38366 pointers; printing a code pointer converts it into a symbolic
38367 address. The stack pointer and any dedicated address registers
38368 may be marked as data pointers.
38371 Single precision IEEE floating point.
38374 Double precision IEEE floating point.
38377 The 12-byte extended precision format used by ARM FPA registers.
38380 The 10-byte extended precision format used by x87 registers.
38383 32bit @sc{eflags} register used by x86.
38386 32bit @sc{mxcsr} register used by x86.
38390 @node Standard Target Features
38391 @section Standard Target Features
38392 @cindex target descriptions, standard features
38394 A target description must contain either no registers or all the
38395 target's registers. If the description contains no registers, then
38396 @value{GDBN} will assume a default register layout, selected based on
38397 the architecture. If the description contains any registers, the
38398 default layout will not be used; the standard registers must be
38399 described in the target description, in such a way that @value{GDBN}
38400 can recognize them.
38402 This is accomplished by giving specific names to feature elements
38403 which contain standard registers. @value{GDBN} will look for features
38404 with those names and verify that they contain the expected registers;
38405 if any known feature is missing required registers, or if any required
38406 feature is missing, @value{GDBN} will reject the target
38407 description. You can add additional registers to any of the
38408 standard features --- @value{GDBN} will display them just as if
38409 they were added to an unrecognized feature.
38411 This section lists the known features and their expected contents.
38412 Sample XML documents for these features are included in the
38413 @value{GDBN} source tree, in the directory @file{gdb/features}.
38415 Names recognized by @value{GDBN} should include the name of the
38416 company or organization which selected the name, and the overall
38417 architecture to which the feature applies; so e.g.@: the feature
38418 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38420 The names of registers are not case sensitive for the purpose
38421 of recognizing standard features, but @value{GDBN} will only display
38422 registers using the capitalization used in the description.
38429 * PowerPC Features::
38435 @subsection ARM Features
38436 @cindex target descriptions, ARM features
38438 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38440 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38441 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38443 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38444 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38445 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38448 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38449 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38451 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38452 it should contain at least registers @samp{wR0} through @samp{wR15} and
38453 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38454 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38456 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38457 should contain at least registers @samp{d0} through @samp{d15}. If
38458 they are present, @samp{d16} through @samp{d31} should also be included.
38459 @value{GDBN} will synthesize the single-precision registers from
38460 halves of the double-precision registers.
38462 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38463 need to contain registers; it instructs @value{GDBN} to display the
38464 VFP double-precision registers as vectors and to synthesize the
38465 quad-precision registers from pairs of double-precision registers.
38466 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38467 be present and include 32 double-precision registers.
38469 @node i386 Features
38470 @subsection i386 Features
38471 @cindex target descriptions, i386 features
38473 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38474 targets. It should describe the following registers:
38478 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38480 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38482 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38483 @samp{fs}, @samp{gs}
38485 @samp{st0} through @samp{st7}
38487 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38488 @samp{foseg}, @samp{fooff} and @samp{fop}
38491 The register sets may be different, depending on the target.
38493 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38494 describe registers:
38498 @samp{xmm0} through @samp{xmm7} for i386
38500 @samp{xmm0} through @samp{xmm15} for amd64
38505 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38506 @samp{org.gnu.gdb.i386.sse} feature. It should
38507 describe the upper 128 bits of @sc{ymm} registers:
38511 @samp{ymm0h} through @samp{ymm7h} for i386
38513 @samp{ymm0h} through @samp{ymm15h} for amd64
38516 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38517 describe a single register, @samp{orig_eax}.
38519 @node MIPS Features
38520 @subsection MIPS Features
38521 @cindex target descriptions, MIPS features
38523 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38524 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38525 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38528 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38529 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38530 registers. They may be 32-bit or 64-bit depending on the target.
38532 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38533 it may be optional in a future version of @value{GDBN}. It should
38534 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38535 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38537 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38538 contain a single register, @samp{restart}, which is used by the
38539 Linux kernel to control restartable syscalls.
38541 @node M68K Features
38542 @subsection M68K Features
38543 @cindex target descriptions, M68K features
38546 @item @samp{org.gnu.gdb.m68k.core}
38547 @itemx @samp{org.gnu.gdb.coldfire.core}
38548 @itemx @samp{org.gnu.gdb.fido.core}
38549 One of those features must be always present.
38550 The feature that is present determines which flavor of m68k is
38551 used. The feature that is present should contain registers
38552 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38553 @samp{sp}, @samp{ps} and @samp{pc}.
38555 @item @samp{org.gnu.gdb.coldfire.fp}
38556 This feature is optional. If present, it should contain registers
38557 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38561 @node PowerPC Features
38562 @subsection PowerPC Features
38563 @cindex target descriptions, PowerPC features
38565 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38566 targets. It should contain registers @samp{r0} through @samp{r31},
38567 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38568 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38570 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38571 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38573 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38574 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38577 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38578 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38579 will combine these registers with the floating point registers
38580 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38581 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38582 through @samp{vs63}, the set of vector registers for POWER7.
38584 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38585 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38586 @samp{spefscr}. SPE targets should provide 32-bit registers in
38587 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38588 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38589 these to present registers @samp{ev0} through @samp{ev31} to the
38592 @node TIC6x Features
38593 @subsection TMS320C6x Features
38594 @cindex target descriptions, TIC6x features
38595 @cindex target descriptions, TMS320C6x features
38596 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38597 targets. It should contain registers @samp{A0} through @samp{A15},
38598 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38600 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38601 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38602 through @samp{B31}.
38604 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38605 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38607 @node Operating System Information
38608 @appendix Operating System Information
38609 @cindex operating system information
38615 Users of @value{GDBN} often wish to obtain information about the state of
38616 the operating system running on the target---for example the list of
38617 processes, or the list of open files. This section describes the
38618 mechanism that makes it possible. This mechanism is similar to the
38619 target features mechanism (@pxref{Target Descriptions}), but focuses
38620 on a different aspect of target.
38622 Operating system information is retrived from the target via the
38623 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38624 read}). The object name in the request should be @samp{osdata}, and
38625 the @var{annex} identifies the data to be fetched.
38628 @appendixsection Process list
38629 @cindex operating system information, process list
38631 When requesting the process list, the @var{annex} field in the
38632 @samp{qXfer} request should be @samp{processes}. The returned data is
38633 an XML document. The formal syntax of this document is defined in
38634 @file{gdb/features/osdata.dtd}.
38636 An example document is:
38639 <?xml version="1.0"?>
38640 <!DOCTYPE target SYSTEM "osdata.dtd">
38641 <osdata type="processes">
38643 <column name="pid">1</column>
38644 <column name="user">root</column>
38645 <column name="command">/sbin/init</column>
38646 <column name="cores">1,2,3</column>
38651 Each item should include a column whose name is @samp{pid}. The value
38652 of that column should identify the process on the target. The
38653 @samp{user} and @samp{command} columns are optional, and will be
38654 displayed by @value{GDBN}. The @samp{cores} column, if present,
38655 should contain a comma-separated list of cores that this process
38656 is running on. Target may provide additional columns,
38657 which @value{GDBN} currently ignores.
38659 @node Trace File Format
38660 @appendix Trace File Format
38661 @cindex trace file format
38663 The trace file comes in three parts: a header, a textual description
38664 section, and a trace frame section with binary data.
38666 The header has the form @code{\x7fTRACE0\n}. The first byte is
38667 @code{0x7f} so as to indicate that the file contains binary data,
38668 while the @code{0} is a version number that may have different values
38671 The description section consists of multiple lines of @sc{ascii} text
38672 separated by newline characters (@code{0xa}). The lines may include a
38673 variety of optional descriptive or context-setting information, such
38674 as tracepoint definitions or register set size. @value{GDBN} will
38675 ignore any line that it does not recognize. An empty line marks the end
38678 @c FIXME add some specific types of data
38680 The trace frame section consists of a number of consecutive frames.
38681 Each frame begins with a two-byte tracepoint number, followed by a
38682 four-byte size giving the amount of data in the frame. The data in
38683 the frame consists of a number of blocks, each introduced by a
38684 character indicating its type (at least register, memory, and trace
38685 state variable). The data in this section is raw binary, not a
38686 hexadecimal or other encoding; its endianness matches the target's
38689 @c FIXME bi-arch may require endianness/arch info in description section
38692 @item R @var{bytes}
38693 Register block. The number and ordering of bytes matches that of a
38694 @code{g} packet in the remote protocol. Note that these are the
38695 actual bytes, in target order and @value{GDBN} register order, not a
38696 hexadecimal encoding.
38698 @item M @var{address} @var{length} @var{bytes}...
38699 Memory block. This is a contiguous block of memory, at the 8-byte
38700 address @var{address}, with a 2-byte length @var{length}, followed by
38701 @var{length} bytes.
38703 @item V @var{number} @var{value}
38704 Trace state variable block. This records the 8-byte signed value
38705 @var{value} of trace state variable numbered @var{number}.
38709 Future enhancements of the trace file format may include additional types
38712 @node Index Section Format
38713 @appendix @code{.gdb_index} section format
38714 @cindex .gdb_index section format
38715 @cindex index section format
38717 This section documents the index section that is created by @code{save
38718 gdb-index} (@pxref{Index Files}). The index section is
38719 DWARF-specific; some knowledge of DWARF is assumed in this
38722 The mapped index file format is designed to be directly
38723 @code{mmap}able on any architecture. In most cases, a datum is
38724 represented using a little-endian 32-bit integer value, called an
38725 @code{offset_type}. Big endian machines must byte-swap the values
38726 before using them. Exceptions to this rule are noted. The data is
38727 laid out such that alignment is always respected.
38729 A mapped index consists of several areas, laid out in order.
38733 The file header. This is a sequence of values, of @code{offset_type}
38734 unless otherwise noted:
38738 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38739 Version 4 differs by its hashing function.
38742 The offset, from the start of the file, of the CU list.
38745 The offset, from the start of the file, of the types CU list. Note
38746 that this area can be empty, in which case this offset will be equal
38747 to the next offset.
38750 The offset, from the start of the file, of the address area.
38753 The offset, from the start of the file, of the symbol table.
38756 The offset, from the start of the file, of the constant pool.
38760 The CU list. This is a sequence of pairs of 64-bit little-endian
38761 values, sorted by the CU offset. The first element in each pair is
38762 the offset of a CU in the @code{.debug_info} section. The second
38763 element in each pair is the length of that CU. References to a CU
38764 elsewhere in the map are done using a CU index, which is just the
38765 0-based index into this table. Note that if there are type CUs, then
38766 conceptually CUs and type CUs form a single list for the purposes of
38770 The types CU list. This is a sequence of triplets of 64-bit
38771 little-endian values. In a triplet, the first value is the CU offset,
38772 the second value is the type offset in the CU, and the third value is
38773 the type signature. The types CU list is not sorted.
38776 The address area. The address area consists of a sequence of address
38777 entries. Each address entry has three elements:
38781 The low address. This is a 64-bit little-endian value.
38784 The high address. This is a 64-bit little-endian value. Like
38785 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38788 The CU index. This is an @code{offset_type} value.
38792 The symbol table. This is an open-addressed hash table. The size of
38793 the hash table is always a power of 2.
38795 Each slot in the hash table consists of a pair of @code{offset_type}
38796 values. The first value is the offset of the symbol's name in the
38797 constant pool. The second value is the offset of the CU vector in the
38800 If both values are 0, then this slot in the hash table is empty. This
38801 is ok because while 0 is a valid constant pool index, it cannot be a
38802 valid index for both a string and a CU vector.
38804 The hash value for a table entry is computed by applying an
38805 iterative hash function to the symbol's name. Starting with an
38806 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38807 the string is incorporated into the hash using the formula depending on the
38812 The formula is @code{r = r * 67 + c - 113}.
38815 The formula is @code{r = r * 67 + tolower (c) - 113}.
38818 The terminating @samp{\0} is not incorporated into the hash.
38820 The step size used in the hash table is computed via
38821 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38822 value, and @samp{size} is the size of the hash table. The step size
38823 is used to find the next candidate slot when handling a hash
38826 The names of C@t{++} symbols in the hash table are canonicalized. We
38827 don't currently have a simple description of the canonicalization
38828 algorithm; if you intend to create new index sections, you must read
38832 The constant pool. This is simply a bunch of bytes. It is organized
38833 so that alignment is correct: CU vectors are stored first, followed by
38836 A CU vector in the constant pool is a sequence of @code{offset_type}
38837 values. The first value is the number of CU indices in the vector.
38838 Each subsequent value is the index of a CU in the CU list. This
38839 element in the hash table is used to indicate which CUs define the
38842 A string in the constant pool is zero-terminated.
38847 @node GNU Free Documentation License
38848 @appendix GNU Free Documentation License
38857 % I think something like @colophon should be in texinfo. In the
38859 \long\def\colophon{\hbox to0pt{}\vfill
38860 \centerline{The body of this manual is set in}
38861 \centerline{\fontname\tenrm,}
38862 \centerline{with headings in {\bf\fontname\tenbf}}
38863 \centerline{and examples in {\tt\fontname\tentt}.}
38864 \centerline{{\it\fontname\tenit\/},}
38865 \centerline{{\bf\fontname\tenbf}, and}
38866 \centerline{{\sl\fontname\tensl\/}}
38867 \centerline{are used for emphasis.}\vfill}
38869 % Blame: doc@cygnus.com, 1991.