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 @value{GDBN} allows you to set any number of breakpoints at the same place in
3511 your program. There is nothing silly or meaningless about this. When
3512 the breakpoints are conditional, this is even useful
3513 (@pxref{Conditions, ,Break Conditions}).
3515 @cindex multiple locations, breakpoints
3516 @cindex breakpoints, multiple locations
3517 It is possible that a breakpoint corresponds to several locations
3518 in your program. Examples of this situation are:
3522 Multiple functions in the program may have the same name.
3525 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3526 instances of the function body, used in different cases.
3529 For a C@t{++} template function, a given line in the function can
3530 correspond to any number of instantiations.
3533 For an inlined function, a given source line can correspond to
3534 several places where that function is inlined.
3537 In all those cases, @value{GDBN} will insert a breakpoint at all
3538 the relevant locations.
3540 A breakpoint with multiple locations is displayed in the breakpoint
3541 table using several rows---one header row, followed by one row for
3542 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3543 address column. The rows for individual locations contain the actual
3544 addresses for locations, and show the functions to which those
3545 locations belong. The number column for a location is of the form
3546 @var{breakpoint-number}.@var{location-number}.
3551 Num Type Disp Enb Address What
3552 1 breakpoint keep y <MULTIPLE>
3554 breakpoint already hit 1 time
3555 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3556 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3559 Each location can be individually enabled or disabled by passing
3560 @var{breakpoint-number}.@var{location-number} as argument to the
3561 @code{enable} and @code{disable} commands. Note that you cannot
3562 delete the individual locations from the list, you can only delete the
3563 entire list of locations that belong to their parent breakpoint (with
3564 the @kbd{delete @var{num}} command, where @var{num} is the number of
3565 the parent breakpoint, 1 in the above example). Disabling or enabling
3566 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3567 that belong to that breakpoint.
3569 @cindex pending breakpoints
3570 It's quite common to have a breakpoint inside a shared library.
3571 Shared libraries can be loaded and unloaded explicitly,
3572 and possibly repeatedly, as the program is executed. To support
3573 this use case, @value{GDBN} updates breakpoint locations whenever
3574 any shared library is loaded or unloaded. Typically, you would
3575 set a breakpoint in a shared library at the beginning of your
3576 debugging session, when the library is not loaded, and when the
3577 symbols from the library are not available. When you try to set
3578 breakpoint, @value{GDBN} will ask you if you want to set
3579 a so called @dfn{pending breakpoint}---breakpoint whose address
3580 is not yet resolved.
3582 After the program is run, whenever a new shared library is loaded,
3583 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3584 shared library contains the symbol or line referred to by some
3585 pending breakpoint, that breakpoint is resolved and becomes an
3586 ordinary breakpoint. When a library is unloaded, all breakpoints
3587 that refer to its symbols or source lines become pending again.
3589 This logic works for breakpoints with multiple locations, too. For
3590 example, if you have a breakpoint in a C@t{++} template function, and
3591 a newly loaded shared library has an instantiation of that template,
3592 a new location is added to the list of locations for the breakpoint.
3594 Except for having unresolved address, pending breakpoints do not
3595 differ from regular breakpoints. You can set conditions or commands,
3596 enable and disable them and perform other breakpoint operations.
3598 @value{GDBN} provides some additional commands for controlling what
3599 happens when the @samp{break} command cannot resolve breakpoint
3600 address specification to an address:
3602 @kindex set breakpoint pending
3603 @kindex show breakpoint pending
3605 @item set breakpoint pending auto
3606 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3607 location, it queries you whether a pending breakpoint should be created.
3609 @item set breakpoint pending on
3610 This indicates that an unrecognized breakpoint location should automatically
3611 result in a pending breakpoint being created.
3613 @item set breakpoint pending off
3614 This indicates that pending breakpoints are not to be created. Any
3615 unrecognized breakpoint location results in an error. This setting does
3616 not affect any pending breakpoints previously created.
3618 @item show breakpoint pending
3619 Show the current behavior setting for creating pending breakpoints.
3622 The settings above only affect the @code{break} command and its
3623 variants. Once breakpoint is set, it will be automatically updated
3624 as shared libraries are loaded and unloaded.
3626 @cindex automatic hardware breakpoints
3627 For some targets, @value{GDBN} can automatically decide if hardware or
3628 software breakpoints should be used, depending on whether the
3629 breakpoint address is read-only or read-write. This applies to
3630 breakpoints set with the @code{break} command as well as to internal
3631 breakpoints set by commands like @code{next} and @code{finish}. For
3632 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3635 You can control this automatic behaviour with the following commands::
3637 @kindex set breakpoint auto-hw
3638 @kindex show breakpoint auto-hw
3640 @item set breakpoint auto-hw on
3641 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3642 will try to use the target memory map to decide if software or hardware
3643 breakpoint must be used.
3645 @item set breakpoint auto-hw off
3646 This indicates @value{GDBN} should not automatically select breakpoint
3647 type. If the target provides a memory map, @value{GDBN} will warn when
3648 trying to set software breakpoint at a read-only address.
3651 @value{GDBN} normally implements breakpoints by replacing the program code
3652 at the breakpoint address with a special instruction, which, when
3653 executed, given control to the debugger. By default, the program
3654 code is so modified only when the program is resumed. As soon as
3655 the program stops, @value{GDBN} restores the original instructions. This
3656 behaviour guards against leaving breakpoints inserted in the
3657 target should gdb abrubptly disconnect. However, with slow remote
3658 targets, inserting and removing breakpoint can reduce the performance.
3659 This behavior can be controlled with the following commands::
3661 @kindex set breakpoint always-inserted
3662 @kindex show breakpoint always-inserted
3664 @item set breakpoint always-inserted off
3665 All breakpoints, including newly added by the user, are inserted in
3666 the target only when the target is resumed. All breakpoints are
3667 removed from the target when it stops.
3669 @item set breakpoint always-inserted on
3670 Causes all breakpoints to be inserted in the target at all times. If
3671 the user adds a new breakpoint, or changes an existing breakpoint, the
3672 breakpoints in the target are updated immediately. A breakpoint is
3673 removed from the target only when breakpoint itself is removed.
3675 @cindex non-stop mode, and @code{breakpoint always-inserted}
3676 @item set breakpoint always-inserted auto
3677 This is the default mode. If @value{GDBN} is controlling the inferior
3678 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3679 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3680 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3681 @code{breakpoint always-inserted} mode is off.
3684 @cindex negative breakpoint numbers
3685 @cindex internal @value{GDBN} breakpoints
3686 @value{GDBN} itself sometimes sets breakpoints in your program for
3687 special purposes, such as proper handling of @code{longjmp} (in C
3688 programs). These internal breakpoints are assigned negative numbers,
3689 starting with @code{-1}; @samp{info breakpoints} does not display them.
3690 You can see these breakpoints with the @value{GDBN} maintenance command
3691 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3694 @node Set Watchpoints
3695 @subsection Setting Watchpoints
3697 @cindex setting watchpoints
3698 You can use a watchpoint to stop execution whenever the value of an
3699 expression changes, without having to predict a particular place where
3700 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3701 The expression may be as simple as the value of a single variable, or
3702 as complex as many variables combined by operators. Examples include:
3706 A reference to the value of a single variable.
3709 An address cast to an appropriate data type. For example,
3710 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3711 address (assuming an @code{int} occupies 4 bytes).
3714 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3715 expression can use any operators valid in the program's native
3716 language (@pxref{Languages}).
3719 You can set a watchpoint on an expression even if the expression can
3720 not be evaluated yet. For instance, you can set a watchpoint on
3721 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3722 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3723 the expression produces a valid value. If the expression becomes
3724 valid in some other way than changing a variable (e.g.@: if the memory
3725 pointed to by @samp{*global_ptr} becomes readable as the result of a
3726 @code{malloc} call), @value{GDBN} may not stop until the next time
3727 the expression changes.
3729 @cindex software watchpoints
3730 @cindex hardware watchpoints
3731 Depending on your system, watchpoints may be implemented in software or
3732 hardware. @value{GDBN} does software watchpointing by single-stepping your
3733 program and testing the variable's value each time, which is hundreds of
3734 times slower than normal execution. (But this may still be worth it, to
3735 catch errors where you have no clue what part of your program is the
3738 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3739 x86-based targets, @value{GDBN} includes support for hardware
3740 watchpoints, which do not slow down the running of your program.
3744 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3745 Set a watchpoint for an expression. @value{GDBN} will break when the
3746 expression @var{expr} is written into by the program and its value
3747 changes. The simplest (and the most popular) use of this command is
3748 to watch the value of a single variable:
3751 (@value{GDBP}) watch foo
3754 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3755 argument, @value{GDBN} breaks only when the thread identified by
3756 @var{threadnum} changes the value of @var{expr}. If any other threads
3757 change the value of @var{expr}, @value{GDBN} will not break. Note
3758 that watchpoints restricted to a single thread in this way only work
3759 with Hardware Watchpoints.
3761 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3762 (see below). The @code{-location} argument tells @value{GDBN} to
3763 instead watch the memory referred to by @var{expr}. In this case,
3764 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3765 and watch the memory at that address. The type of the result is used
3766 to determine the size of the watched memory. If the expression's
3767 result does not have an address, then @value{GDBN} will print an
3770 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3771 of masked watchpoints, if the current architecture supports this
3772 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3773 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3774 to an address to watch. The mask specifies that some bits of an address
3775 (the bits which are reset in the mask) should be ignored when matching
3776 the address accessed by the inferior against the watchpoint address.
3777 Thus, a masked watchpoint watches many addresses simultaneously---those
3778 addresses whose unmasked bits are identical to the unmasked bits in the
3779 watchpoint address. The @code{mask} argument implies @code{-location}.
3783 (@value{GDBP}) watch foo mask 0xffff00ff
3784 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3788 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when the value of @var{expr} is read
3793 @item awatch @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 @var{expr} is either read from
3795 or written into by the program.
3797 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3798 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3799 This command prints a list of watchpoints, using the same format as
3800 @code{info break} (@pxref{Set Breaks}).
3803 If you watch for a change in a numerically entered address you need to
3804 dereference it, as the address itself is just a constant number which will
3805 never change. @value{GDBN} refuses to create a watchpoint that watches
3806 a never-changing value:
3809 (@value{GDBP}) watch 0x600850
3810 Cannot watch constant value 0x600850.
3811 (@value{GDBP}) watch *(int *) 0x600850
3812 Watchpoint 1: *(int *) 6293584
3815 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3816 watchpoints execute very quickly, and the debugger reports a change in
3817 value at the exact instruction where the change occurs. If @value{GDBN}
3818 cannot set a hardware watchpoint, it sets a software watchpoint, which
3819 executes more slowly and reports the change in value at the next
3820 @emph{statement}, not the instruction, after the change occurs.
3822 @cindex use only software watchpoints
3823 You can force @value{GDBN} to use only software watchpoints with the
3824 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3825 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3826 the underlying system supports them. (Note that hardware-assisted
3827 watchpoints that were set @emph{before} setting
3828 @code{can-use-hw-watchpoints} to zero will still use the hardware
3829 mechanism of watching expression values.)
3832 @item set can-use-hw-watchpoints
3833 @kindex set can-use-hw-watchpoints
3834 Set whether or not to use hardware watchpoints.
3836 @item show can-use-hw-watchpoints
3837 @kindex show can-use-hw-watchpoints
3838 Show the current mode of using hardware watchpoints.
3841 For remote targets, you can restrict the number of hardware
3842 watchpoints @value{GDBN} will use, see @ref{set remote
3843 hardware-breakpoint-limit}.
3845 When you issue the @code{watch} command, @value{GDBN} reports
3848 Hardware watchpoint @var{num}: @var{expr}
3852 if it was able to set a hardware watchpoint.
3854 Currently, the @code{awatch} and @code{rwatch} commands can only set
3855 hardware watchpoints, because accesses to data that don't change the
3856 value of the watched expression cannot be detected without examining
3857 every instruction as it is being executed, and @value{GDBN} does not do
3858 that currently. If @value{GDBN} finds that it is unable to set a
3859 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3860 will print a message like this:
3863 Expression cannot be implemented with read/access watchpoint.
3866 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3867 data type of the watched expression is wider than what a hardware
3868 watchpoint on the target machine can handle. For example, some systems
3869 can only watch regions that are up to 4 bytes wide; on such systems you
3870 cannot set hardware watchpoints for an expression that yields a
3871 double-precision floating-point number (which is typically 8 bytes
3872 wide). As a work-around, it might be possible to break the large region
3873 into a series of smaller ones and watch them with separate watchpoints.
3875 If you set too many hardware watchpoints, @value{GDBN} might be unable
3876 to insert all of them when you resume the execution of your program.
3877 Since the precise number of active watchpoints is unknown until such
3878 time as the program is about to be resumed, @value{GDBN} might not be
3879 able to warn you about this when you set the watchpoints, and the
3880 warning will be printed only when the program is resumed:
3883 Hardware watchpoint @var{num}: Could not insert watchpoint
3887 If this happens, delete or disable some of the watchpoints.
3889 Watching complex expressions that reference many variables can also
3890 exhaust the resources available for hardware-assisted watchpoints.
3891 That's because @value{GDBN} needs to watch every variable in the
3892 expression with separately allocated resources.
3894 If you call a function interactively using @code{print} or @code{call},
3895 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3896 kind of breakpoint or the call completes.
3898 @value{GDBN} automatically deletes watchpoints that watch local
3899 (automatic) variables, or expressions that involve such variables, when
3900 they go out of scope, that is, when the execution leaves the block in
3901 which these variables were defined. In particular, when the program
3902 being debugged terminates, @emph{all} local variables go out of scope,
3903 and so only watchpoints that watch global variables remain set. If you
3904 rerun the program, you will need to set all such watchpoints again. One
3905 way of doing that would be to set a code breakpoint at the entry to the
3906 @code{main} function and when it breaks, set all the watchpoints.
3908 @cindex watchpoints and threads
3909 @cindex threads and watchpoints
3910 In multi-threaded programs, watchpoints will detect changes to the
3911 watched expression from every thread.
3914 @emph{Warning:} In multi-threaded programs, software watchpoints
3915 have only limited usefulness. If @value{GDBN} creates a software
3916 watchpoint, it can only watch the value of an expression @emph{in a
3917 single thread}. If you are confident that the expression can only
3918 change due to the current thread's activity (and if you are also
3919 confident that no other thread can become current), then you can use
3920 software watchpoints as usual. However, @value{GDBN} may not notice
3921 when a non-current thread's activity changes the expression. (Hardware
3922 watchpoints, in contrast, watch an expression in all threads.)
3925 @xref{set remote hardware-watchpoint-limit}.
3927 @node Set Catchpoints
3928 @subsection Setting Catchpoints
3929 @cindex catchpoints, setting
3930 @cindex exception handlers
3931 @cindex event handling
3933 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3934 kinds of program events, such as C@t{++} exceptions or the loading of a
3935 shared library. Use the @code{catch} command to set a catchpoint.
3939 @item catch @var{event}
3940 Stop when @var{event} occurs. @var{event} can be any of the following:
3943 @cindex stop on C@t{++} exceptions
3944 The throwing of a C@t{++} exception.
3947 The catching of a C@t{++} exception.
3950 @cindex Ada exception catching
3951 @cindex catch Ada exceptions
3952 An Ada exception being raised. If an exception name is specified
3953 at the end of the command (eg @code{catch exception Program_Error}),
3954 the debugger will stop only when this specific exception is raised.
3955 Otherwise, the debugger stops execution when any Ada exception is raised.
3957 When inserting an exception catchpoint on a user-defined exception whose
3958 name is identical to one of the exceptions defined by the language, the
3959 fully qualified name must be used as the exception name. Otherwise,
3960 @value{GDBN} will assume that it should stop on the pre-defined exception
3961 rather than the user-defined one. For instance, assuming an exception
3962 called @code{Constraint_Error} is defined in package @code{Pck}, then
3963 the command to use to catch such exceptions is @kbd{catch exception
3964 Pck.Constraint_Error}.
3966 @item exception unhandled
3967 An exception that was raised but is not handled by the program.
3970 A failed Ada assertion.
3973 @cindex break on fork/exec
3974 A call to @code{exec}. This is currently only available for HP-UX
3978 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3979 @cindex break on a system call.
3980 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3981 syscall is a mechanism for application programs to request a service
3982 from the operating system (OS) or one of the OS system services.
3983 @value{GDBN} can catch some or all of the syscalls issued by the
3984 debuggee, and show the related information for each syscall. If no
3985 argument is specified, calls to and returns from all system calls
3988 @var{name} can be any system call name that is valid for the
3989 underlying OS. Just what syscalls are valid depends on the OS. On
3990 GNU and Unix systems, you can find the full list of valid syscall
3991 names on @file{/usr/include/asm/unistd.h}.
3993 @c For MS-Windows, the syscall names and the corresponding numbers
3994 @c can be found, e.g., on this URL:
3995 @c http://www.metasploit.com/users/opcode/syscalls.html
3996 @c but we don't support Windows syscalls yet.
3998 Normally, @value{GDBN} knows in advance which syscalls are valid for
3999 each OS, so you can use the @value{GDBN} command-line completion
4000 facilities (@pxref{Completion,, command completion}) to list the
4003 You may also specify the system call numerically. A syscall's
4004 number is the value passed to the OS's syscall dispatcher to
4005 identify the requested service. When you specify the syscall by its
4006 name, @value{GDBN} uses its database of syscalls to convert the name
4007 into the corresponding numeric code, but using the number directly
4008 may be useful if @value{GDBN}'s database does not have the complete
4009 list of syscalls on your system (e.g., because @value{GDBN} lags
4010 behind the OS upgrades).
4012 The example below illustrates how this command works if you don't provide
4016 (@value{GDBP}) catch syscall
4017 Catchpoint 1 (syscall)
4019 Starting program: /tmp/catch-syscall
4021 Catchpoint 1 (call to syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Catchpoint 1 (returned from syscall 'close'), \
4027 0xffffe424 in __kernel_vsyscall ()
4031 Here is an example of catching a system call by name:
4034 (@value{GDBP}) catch syscall chroot
4035 Catchpoint 1 (syscall 'chroot' [61])
4037 Starting program: /tmp/catch-syscall
4039 Catchpoint 1 (call to syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 Catchpoint 1 (returned from syscall 'chroot'), \
4045 0xffffe424 in __kernel_vsyscall ()
4049 An example of specifying a system call numerically. In the case
4050 below, the syscall number has a corresponding entry in the XML
4051 file, so @value{GDBN} finds its name and prints it:
4054 (@value{GDBP}) catch syscall 252
4055 Catchpoint 1 (syscall(s) 'exit_group')
4057 Starting program: /tmp/catch-syscall
4059 Catchpoint 1 (call to syscall 'exit_group'), \
4060 0xffffe424 in __kernel_vsyscall ()
4064 Program exited normally.
4068 However, there can be situations when there is no corresponding name
4069 in XML file for that syscall number. In this case, @value{GDBN} prints
4070 a warning message saying that it was not able to find the syscall name,
4071 but the catchpoint will be set anyway. See the example below:
4074 (@value{GDBP}) catch syscall 764
4075 warning: The number '764' does not represent a known syscall.
4076 Catchpoint 2 (syscall 764)
4080 If you configure @value{GDBN} using the @samp{--without-expat} option,
4081 it will not be able to display syscall names. Also, if your
4082 architecture does not have an XML file describing its system calls,
4083 you will not be able to see the syscall names. It is important to
4084 notice that these two features are used for accessing the syscall
4085 name database. In either case, you will see a warning like this:
4088 (@value{GDBP}) catch syscall
4089 warning: Could not open "syscalls/i386-linux.xml"
4090 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4091 GDB will not be able to display syscall names.
4092 Catchpoint 1 (syscall)
4096 Of course, the file name will change depending on your architecture and system.
4098 Still using the example above, you can also try to catch a syscall by its
4099 number. In this case, you would see something like:
4102 (@value{GDBP}) catch syscall 252
4103 Catchpoint 1 (syscall(s) 252)
4106 Again, in this case @value{GDBN} would not be able to display syscall's names.
4109 A call to @code{fork}. This is currently only available for HP-UX
4113 A call to @code{vfork}. This is currently only available for HP-UX
4118 @item tcatch @var{event}
4119 Set a catchpoint that is enabled only for one stop. The catchpoint is
4120 automatically deleted after the first time the event is caught.
4124 Use the @code{info break} command to list the current catchpoints.
4126 There are currently some limitations to C@t{++} exception handling
4127 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4131 If you call a function interactively, @value{GDBN} normally returns
4132 control to you when the function has finished executing. If the call
4133 raises an exception, however, the call may bypass the mechanism that
4134 returns control to you and cause your program either to abort or to
4135 simply continue running until it hits a breakpoint, catches a signal
4136 that @value{GDBN} is listening for, or exits. This is the case even if
4137 you set a catchpoint for the exception; catchpoints on exceptions are
4138 disabled within interactive calls.
4141 You cannot raise an exception interactively.
4144 You cannot install an exception handler interactively.
4147 @cindex raise exceptions
4148 Sometimes @code{catch} is not the best way to debug exception handling:
4149 if you need to know exactly where an exception is raised, it is better to
4150 stop @emph{before} the exception handler is called, since that way you
4151 can see the stack before any unwinding takes place. If you set a
4152 breakpoint in an exception handler instead, it may not be easy to find
4153 out where the exception was raised.
4155 To stop just before an exception handler is called, you need some
4156 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4157 raised by calling a library function named @code{__raise_exception}
4158 which has the following ANSI C interface:
4161 /* @var{addr} is where the exception identifier is stored.
4162 @var{id} is the exception identifier. */
4163 void __raise_exception (void **addr, void *id);
4167 To make the debugger catch all exceptions before any stack
4168 unwinding takes place, set a breakpoint on @code{__raise_exception}
4169 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4171 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4172 that depends on the value of @var{id}, you can stop your program when
4173 a specific exception is raised. You can use multiple conditional
4174 breakpoints to stop your program when any of a number of exceptions are
4179 @subsection Deleting Breakpoints
4181 @cindex clearing breakpoints, watchpoints, catchpoints
4182 @cindex deleting breakpoints, watchpoints, catchpoints
4183 It is often necessary to eliminate a breakpoint, watchpoint, or
4184 catchpoint once it has done its job and you no longer want your program
4185 to stop there. This is called @dfn{deleting} the breakpoint. A
4186 breakpoint that has been deleted no longer exists; it is forgotten.
4188 With the @code{clear} command you can delete breakpoints according to
4189 where they are in your program. With the @code{delete} command you can
4190 delete individual breakpoints, watchpoints, or catchpoints by specifying
4191 their breakpoint numbers.
4193 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4194 automatically ignores breakpoints on the first instruction to be executed
4195 when you continue execution without changing the execution address.
4200 Delete any breakpoints at the next instruction to be executed in the
4201 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4202 the innermost frame is selected, this is a good way to delete a
4203 breakpoint where your program just stopped.
4205 @item clear @var{location}
4206 Delete any breakpoints set at the specified @var{location}.
4207 @xref{Specify Location}, for the various forms of @var{location}; the
4208 most useful ones are listed below:
4211 @item clear @var{function}
4212 @itemx clear @var{filename}:@var{function}
4213 Delete any breakpoints set at entry to the named @var{function}.
4215 @item clear @var{linenum}
4216 @itemx clear @var{filename}:@var{linenum}
4217 Delete any breakpoints set at or within the code of the specified
4218 @var{linenum} of the specified @var{filename}.
4221 @cindex delete breakpoints
4223 @kindex d @r{(@code{delete})}
4224 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4225 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4226 ranges specified as arguments. If no argument is specified, delete all
4227 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4228 confirm off}). You can abbreviate this command as @code{d}.
4232 @subsection Disabling Breakpoints
4234 @cindex enable/disable a breakpoint
4235 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4236 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4237 it had been deleted, but remembers the information on the breakpoint so
4238 that you can @dfn{enable} it again later.
4240 You disable and enable breakpoints, watchpoints, and catchpoints with
4241 the @code{enable} and @code{disable} commands, optionally specifying
4242 one or more breakpoint numbers as arguments. Use @code{info break} to
4243 print a list of all breakpoints, watchpoints, and catchpoints if you
4244 do not know which numbers to use.
4246 Disabling and enabling a breakpoint that has multiple locations
4247 affects all of its locations.
4249 A breakpoint, watchpoint, or catchpoint can have any of four different
4250 states of enablement:
4254 Enabled. The breakpoint stops your program. A breakpoint set
4255 with the @code{break} command starts out in this state.
4257 Disabled. The breakpoint has no effect on your program.
4259 Enabled once. The breakpoint stops your program, but then becomes
4262 Enabled for deletion. The breakpoint stops your program, but
4263 immediately after it does so it is deleted permanently. A breakpoint
4264 set with the @code{tbreak} command starts out in this state.
4267 You can use the following commands to enable or disable breakpoints,
4268 watchpoints, and catchpoints:
4272 @kindex dis @r{(@code{disable})}
4273 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4274 Disable the specified breakpoints---or all breakpoints, if none are
4275 listed. A disabled breakpoint has no effect but is not forgotten. All
4276 options such as ignore-counts, conditions and commands are remembered in
4277 case the breakpoint is enabled again later. You may abbreviate
4278 @code{disable} as @code{dis}.
4281 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4282 Enable the specified breakpoints (or all defined breakpoints). They
4283 become effective once again in stopping your program.
4285 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4286 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4287 of these breakpoints immediately after stopping your program.
4289 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4290 Enable the specified breakpoints to work once, then die. @value{GDBN}
4291 deletes any of these breakpoints as soon as your program stops there.
4292 Breakpoints set by the @code{tbreak} command start out in this state.
4295 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4296 @c confusing: tbreak is also initially enabled.
4297 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4298 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4299 subsequently, they become disabled or enabled only when you use one of
4300 the commands above. (The command @code{until} can set and delete a
4301 breakpoint of its own, but it does not change the state of your other
4302 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4306 @subsection Break Conditions
4307 @cindex conditional breakpoints
4308 @cindex breakpoint conditions
4310 @c FIXME what is scope of break condition expr? Context where wanted?
4311 @c in particular for a watchpoint?
4312 The simplest sort of breakpoint breaks every time your program reaches a
4313 specified place. You can also specify a @dfn{condition} for a
4314 breakpoint. A condition is just a Boolean expression in your
4315 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4316 a condition evaluates the expression each time your program reaches it,
4317 and your program stops only if the condition is @emph{true}.
4319 This is the converse of using assertions for program validation; in that
4320 situation, you want to stop when the assertion is violated---that is,
4321 when the condition is false. In C, if you want to test an assertion expressed
4322 by the condition @var{assert}, you should set the condition
4323 @samp{! @var{assert}} on the appropriate breakpoint.
4325 Conditions are also accepted for watchpoints; you may not need them,
4326 since a watchpoint is inspecting the value of an expression anyhow---but
4327 it might be simpler, say, to just set a watchpoint on a variable name,
4328 and specify a condition that tests whether the new value is an interesting
4331 Break conditions can have side effects, and may even call functions in
4332 your program. This can be useful, for example, to activate functions
4333 that log program progress, or to use your own print functions to
4334 format special data structures. The effects are completely predictable
4335 unless there is another enabled breakpoint at the same address. (In
4336 that case, @value{GDBN} might see the other breakpoint first and stop your
4337 program without checking the condition of this one.) Note that
4338 breakpoint commands are usually more convenient and flexible than break
4340 purpose of performing side effects when a breakpoint is reached
4341 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4343 Break conditions can be specified when a breakpoint is set, by using
4344 @samp{if} in the arguments to the @code{break} command. @xref{Set
4345 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4346 with the @code{condition} command.
4348 You can also use the @code{if} keyword with the @code{watch} command.
4349 The @code{catch} command does not recognize the @code{if} keyword;
4350 @code{condition} is the only way to impose a further condition on a
4355 @item condition @var{bnum} @var{expression}
4356 Specify @var{expression} as the break condition for breakpoint,
4357 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4358 breakpoint @var{bnum} stops your program only if the value of
4359 @var{expression} is true (nonzero, in C). When you use
4360 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4361 syntactic correctness, and to determine whether symbols in it have
4362 referents in the context of your breakpoint. If @var{expression} uses
4363 symbols not referenced in the context of the breakpoint, @value{GDBN}
4364 prints an error message:
4367 No symbol "foo" in current context.
4372 not actually evaluate @var{expression} at the time the @code{condition}
4373 command (or a command that sets a breakpoint with a condition, like
4374 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4376 @item condition @var{bnum}
4377 Remove the condition from breakpoint number @var{bnum}. It becomes
4378 an ordinary unconditional breakpoint.
4381 @cindex ignore count (of breakpoint)
4382 A special case of a breakpoint condition is to stop only when the
4383 breakpoint has been reached a certain number of times. This is so
4384 useful that there is a special way to do it, using the @dfn{ignore
4385 count} of the breakpoint. Every breakpoint has an ignore count, which
4386 is an integer. Most of the time, the ignore count is zero, and
4387 therefore has no effect. But if your program reaches a breakpoint whose
4388 ignore count is positive, then instead of stopping, it just decrements
4389 the ignore count by one and continues. As a result, if the ignore count
4390 value is @var{n}, the breakpoint does not stop the next @var{n} times
4391 your program reaches it.
4395 @item ignore @var{bnum} @var{count}
4396 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4397 The next @var{count} times the breakpoint is reached, your program's
4398 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4401 To make the breakpoint stop the next time it is reached, specify
4404 When you use @code{continue} to resume execution of your program from a
4405 breakpoint, you can specify an ignore count directly as an argument to
4406 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4407 Stepping,,Continuing and Stepping}.
4409 If a breakpoint has a positive ignore count and a condition, the
4410 condition is not checked. Once the ignore count reaches zero,
4411 @value{GDBN} resumes checking the condition.
4413 You could achieve the effect of the ignore count with a condition such
4414 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4415 is decremented each time. @xref{Convenience Vars, ,Convenience
4419 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4422 @node Break Commands
4423 @subsection Breakpoint Command Lists
4425 @cindex breakpoint commands
4426 You can give any breakpoint (or watchpoint or catchpoint) a series of
4427 commands to execute when your program stops due to that breakpoint. For
4428 example, you might want to print the values of certain expressions, or
4429 enable other breakpoints.
4433 @kindex end@r{ (breakpoint commands)}
4434 @item commands @r{[}@var{range}@dots{}@r{]}
4435 @itemx @dots{} @var{command-list} @dots{}
4437 Specify a list of commands for the given breakpoints. The commands
4438 themselves appear on the following lines. Type a line containing just
4439 @code{end} to terminate the commands.
4441 To remove all commands from a breakpoint, type @code{commands} and
4442 follow it immediately with @code{end}; that is, give no commands.
4444 With no argument, @code{commands} refers to the last breakpoint,
4445 watchpoint, or catchpoint set (not to the breakpoint most recently
4446 encountered). If the most recent breakpoints were set with a single
4447 command, then the @code{commands} will apply to all the breakpoints
4448 set by that command. This applies to breakpoints set by
4449 @code{rbreak}, and also applies when a single @code{break} command
4450 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4454 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4455 disabled within a @var{command-list}.
4457 You can use breakpoint commands to start your program up again. Simply
4458 use the @code{continue} command, or @code{step}, or any other command
4459 that resumes execution.
4461 Any other commands in the command list, after a command that resumes
4462 execution, are ignored. This is because any time you resume execution
4463 (even with a simple @code{next} or @code{step}), you may encounter
4464 another breakpoint---which could have its own command list, leading to
4465 ambiguities about which list to execute.
4468 If the first command you specify in a command list is @code{silent}, the
4469 usual message about stopping at a breakpoint is not printed. This may
4470 be desirable for breakpoints that are to print a specific message and
4471 then continue. If none of the remaining commands print anything, you
4472 see no sign that the breakpoint was reached. @code{silent} is
4473 meaningful only at the beginning of a breakpoint command list.
4475 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4476 print precisely controlled output, and are often useful in silent
4477 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4479 For example, here is how you could use breakpoint commands to print the
4480 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4486 printf "x is %d\n",x
4491 One application for breakpoint commands is to compensate for one bug so
4492 you can test for another. Put a breakpoint just after the erroneous line
4493 of code, give it a condition to detect the case in which something
4494 erroneous has been done, and give it commands to assign correct values
4495 to any variables that need them. End with the @code{continue} command
4496 so that your program does not stop, and start with the @code{silent}
4497 command so that no output is produced. Here is an example:
4508 @node Save Breakpoints
4509 @subsection How to save breakpoints to a file
4511 To save breakpoint definitions to a file use the @w{@code{save
4512 breakpoints}} command.
4515 @kindex save breakpoints
4516 @cindex save breakpoints to a file for future sessions
4517 @item save breakpoints [@var{filename}]
4518 This command saves all current breakpoint definitions together with
4519 their commands and ignore counts, into a file @file{@var{filename}}
4520 suitable for use in a later debugging session. This includes all
4521 types of breakpoints (breakpoints, watchpoints, catchpoints,
4522 tracepoints). To read the saved breakpoint definitions, use the
4523 @code{source} command (@pxref{Command Files}). Note that watchpoints
4524 with expressions involving local variables may fail to be recreated
4525 because it may not be possible to access the context where the
4526 watchpoint is valid anymore. Because the saved breakpoint definitions
4527 are simply a sequence of @value{GDBN} commands that recreate the
4528 breakpoints, you can edit the file in your favorite editing program,
4529 and remove the breakpoint definitions you're not interested in, or
4530 that can no longer be recreated.
4533 @c @ifclear BARETARGET
4534 @node Error in Breakpoints
4535 @subsection ``Cannot insert breakpoints''
4537 If you request too many active hardware-assisted breakpoints and
4538 watchpoints, you will see this error message:
4540 @c FIXME: the precise wording of this message may change; the relevant
4541 @c source change is not committed yet (Sep 3, 1999).
4543 Stopped; cannot insert breakpoints.
4544 You may have requested too many hardware breakpoints and watchpoints.
4548 This message is printed when you attempt to resume the program, since
4549 only then @value{GDBN} knows exactly how many hardware breakpoints and
4550 watchpoints it needs to insert.
4552 When this message is printed, you need to disable or remove some of the
4553 hardware-assisted breakpoints and watchpoints, and then continue.
4555 @node Breakpoint-related Warnings
4556 @subsection ``Breakpoint address adjusted...''
4557 @cindex breakpoint address adjusted
4559 Some processor architectures place constraints on the addresses at
4560 which breakpoints may be placed. For architectures thus constrained,
4561 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4562 with the constraints dictated by the architecture.
4564 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4565 a VLIW architecture in which a number of RISC-like instructions may be
4566 bundled together for parallel execution. The FR-V architecture
4567 constrains the location of a breakpoint instruction within such a
4568 bundle to the instruction with the lowest address. @value{GDBN}
4569 honors this constraint by adjusting a breakpoint's address to the
4570 first in the bundle.
4572 It is not uncommon for optimized code to have bundles which contain
4573 instructions from different source statements, thus it may happen that
4574 a breakpoint's address will be adjusted from one source statement to
4575 another. Since this adjustment may significantly alter @value{GDBN}'s
4576 breakpoint related behavior from what the user expects, a warning is
4577 printed when the breakpoint is first set and also when the breakpoint
4580 A warning like the one below is printed when setting a breakpoint
4581 that's been subject to address adjustment:
4584 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4587 Such warnings are printed both for user settable and @value{GDBN}'s
4588 internal breakpoints. If you see one of these warnings, you should
4589 verify that a breakpoint set at the adjusted address will have the
4590 desired affect. If not, the breakpoint in question may be removed and
4591 other breakpoints may be set which will have the desired behavior.
4592 E.g., it may be sufficient to place the breakpoint at a later
4593 instruction. A conditional breakpoint may also be useful in some
4594 cases to prevent the breakpoint from triggering too often.
4596 @value{GDBN} will also issue a warning when stopping at one of these
4597 adjusted breakpoints:
4600 warning: Breakpoint 1 address previously adjusted from 0x00010414
4604 When this warning is encountered, it may be too late to take remedial
4605 action except in cases where the breakpoint is hit earlier or more
4606 frequently than expected.
4608 @node Continuing and Stepping
4609 @section Continuing and Stepping
4613 @cindex resuming execution
4614 @dfn{Continuing} means resuming program execution until your program
4615 completes normally. In contrast, @dfn{stepping} means executing just
4616 one more ``step'' of your program, where ``step'' may mean either one
4617 line of source code, or one machine instruction (depending on what
4618 particular command you use). Either when continuing or when stepping,
4619 your program may stop even sooner, due to a breakpoint or a signal. (If
4620 it stops due to a signal, you may want to use @code{handle}, or use
4621 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4625 @kindex c @r{(@code{continue})}
4626 @kindex fg @r{(resume foreground execution)}
4627 @item continue @r{[}@var{ignore-count}@r{]}
4628 @itemx c @r{[}@var{ignore-count}@r{]}
4629 @itemx fg @r{[}@var{ignore-count}@r{]}
4630 Resume program execution, at the address where your program last stopped;
4631 any breakpoints set at that address are bypassed. The optional argument
4632 @var{ignore-count} allows you to specify a further number of times to
4633 ignore a breakpoint at this location; its effect is like that of
4634 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4636 The argument @var{ignore-count} is meaningful only when your program
4637 stopped due to a breakpoint. At other times, the argument to
4638 @code{continue} is ignored.
4640 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4641 debugged program is deemed to be the foreground program) are provided
4642 purely for convenience, and have exactly the same behavior as
4646 To resume execution at a different place, you can use @code{return}
4647 (@pxref{Returning, ,Returning from a Function}) to go back to the
4648 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4649 Different Address}) to go to an arbitrary location in your program.
4651 A typical technique for using stepping is to set a breakpoint
4652 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4653 beginning of the function or the section of your program where a problem
4654 is believed to lie, run your program until it stops at that breakpoint,
4655 and then step through the suspect area, examining the variables that are
4656 interesting, until you see the problem happen.
4660 @kindex s @r{(@code{step})}
4662 Continue running your program until control reaches a different source
4663 line, then stop it and return control to @value{GDBN}. This command is
4664 abbreviated @code{s}.
4667 @c "without debugging information" is imprecise; actually "without line
4668 @c numbers in the debugging information". (gcc -g1 has debugging info but
4669 @c not line numbers). But it seems complex to try to make that
4670 @c distinction here.
4671 @emph{Warning:} If you use the @code{step} command while control is
4672 within a function that was compiled without debugging information,
4673 execution proceeds until control reaches a function that does have
4674 debugging information. Likewise, it will not step into a function which
4675 is compiled without debugging information. To step through functions
4676 without debugging information, use the @code{stepi} command, described
4680 The @code{step} command only stops at the first instruction of a source
4681 line. This prevents the multiple stops that could otherwise occur in
4682 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4683 to stop if a function that has debugging information is called within
4684 the line. In other words, @code{step} @emph{steps inside} any functions
4685 called within the line.
4687 Also, the @code{step} command only enters a function if there is line
4688 number information for the function. Otherwise it acts like the
4689 @code{next} command. This avoids problems when using @code{cc -gl}
4690 on MIPS machines. Previously, @code{step} entered subroutines if there
4691 was any debugging information about the routine.
4693 @item step @var{count}
4694 Continue running as in @code{step}, but do so @var{count} times. If a
4695 breakpoint is reached, or a signal not related to stepping occurs before
4696 @var{count} steps, stepping stops right away.
4699 @kindex n @r{(@code{next})}
4700 @item next @r{[}@var{count}@r{]}
4701 Continue to the next source line in the current (innermost) stack frame.
4702 This is similar to @code{step}, but function calls that appear within
4703 the line of code are executed without stopping. Execution stops when
4704 control reaches a different line of code at the original stack level
4705 that was executing when you gave the @code{next} command. This command
4706 is abbreviated @code{n}.
4708 An argument @var{count} is a repeat count, as for @code{step}.
4711 @c FIX ME!! Do we delete this, or is there a way it fits in with
4712 @c the following paragraph? --- Vctoria
4714 @c @code{next} within a function that lacks debugging information acts like
4715 @c @code{step}, but any function calls appearing within the code of the
4716 @c function are executed without stopping.
4718 The @code{next} command only stops at the first instruction of a
4719 source line. This prevents multiple stops that could otherwise occur in
4720 @code{switch} statements, @code{for} loops, etc.
4722 @kindex set step-mode
4724 @cindex functions without line info, and stepping
4725 @cindex stepping into functions with no line info
4726 @itemx set step-mode on
4727 The @code{set step-mode on} command causes the @code{step} command to
4728 stop at the first instruction of a function which contains no debug line
4729 information rather than stepping over it.
4731 This is useful in cases where you may be interested in inspecting the
4732 machine instructions of a function which has no symbolic info and do not
4733 want @value{GDBN} to automatically skip over this function.
4735 @item set step-mode off
4736 Causes the @code{step} command to step over any functions which contains no
4737 debug information. This is the default.
4739 @item show step-mode
4740 Show whether @value{GDBN} will stop in or step over functions without
4741 source line debug information.
4744 @kindex fin @r{(@code{finish})}
4746 Continue running until just after function in the selected stack frame
4747 returns. Print the returned value (if any). This command can be
4748 abbreviated as @code{fin}.
4750 Contrast this with the @code{return} command (@pxref{Returning,
4751 ,Returning from a Function}).
4754 @kindex u @r{(@code{until})}
4755 @cindex run until specified location
4758 Continue running until a source line past the current line, in the
4759 current stack frame, is reached. This command is used to avoid single
4760 stepping through a loop more than once. It is like the @code{next}
4761 command, except that when @code{until} encounters a jump, it
4762 automatically continues execution until the program counter is greater
4763 than the address of the jump.
4765 This means that when you reach the end of a loop after single stepping
4766 though it, @code{until} makes your program continue execution until it
4767 exits the loop. In contrast, a @code{next} command at the end of a loop
4768 simply steps back to the beginning of the loop, which forces you to step
4769 through the next iteration.
4771 @code{until} always stops your program if it attempts to exit the current
4774 @code{until} may produce somewhat counterintuitive results if the order
4775 of machine code does not match the order of the source lines. For
4776 example, in the following excerpt from a debugging session, the @code{f}
4777 (@code{frame}) command shows that execution is stopped at line
4778 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4782 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4784 (@value{GDBP}) until
4785 195 for ( ; argc > 0; NEXTARG) @{
4788 This happened because, for execution efficiency, the compiler had
4789 generated code for the loop closure test at the end, rather than the
4790 start, of the loop---even though the test in a C @code{for}-loop is
4791 written before the body of the loop. The @code{until} command appeared
4792 to step back to the beginning of the loop when it advanced to this
4793 expression; however, it has not really gone to an earlier
4794 statement---not in terms of the actual machine code.
4796 @code{until} with no argument works by means of single
4797 instruction stepping, and hence is slower than @code{until} with an
4800 @item until @var{location}
4801 @itemx u @var{location}
4802 Continue running your program until either the specified location is
4803 reached, or the current stack frame returns. @var{location} is any of
4804 the forms described in @ref{Specify Location}.
4805 This form of the command uses temporary breakpoints, and
4806 hence is quicker than @code{until} without an argument. The specified
4807 location is actually reached only if it is in the current frame. This
4808 implies that @code{until} can be used to skip over recursive function
4809 invocations. For instance in the code below, if the current location is
4810 line @code{96}, issuing @code{until 99} will execute the program up to
4811 line @code{99} in the same invocation of factorial, i.e., after the inner
4812 invocations have returned.
4815 94 int factorial (int value)
4817 96 if (value > 1) @{
4818 97 value *= factorial (value - 1);
4825 @kindex advance @var{location}
4826 @itemx advance @var{location}
4827 Continue running the program up to the given @var{location}. An argument is
4828 required, which should be of one of the forms described in
4829 @ref{Specify Location}.
4830 Execution will also stop upon exit from the current stack
4831 frame. This command is similar to @code{until}, but @code{advance} will
4832 not skip over recursive function calls, and the target location doesn't
4833 have to be in the same frame as the current one.
4837 @kindex si @r{(@code{stepi})}
4839 @itemx stepi @var{arg}
4841 Execute one machine instruction, then stop and return to the debugger.
4843 It is often useful to do @samp{display/i $pc} when stepping by machine
4844 instructions. This makes @value{GDBN} automatically display the next
4845 instruction to be executed, each time your program stops. @xref{Auto
4846 Display,, Automatic Display}.
4848 An argument is a repeat count, as in @code{step}.
4852 @kindex ni @r{(@code{nexti})}
4854 @itemx nexti @var{arg}
4856 Execute one machine instruction, but if it is a function call,
4857 proceed until the function returns.
4859 An argument is a repeat count, as in @code{next}.
4862 @node Skipping Over Functions and Files
4863 @section Skipping Over Functions and Files
4864 @cindex skipping over functions and files
4866 The program you are debugging may contain some functions which are
4867 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4868 skip a function or all functions in a file when stepping.
4870 For example, consider the following C function:
4881 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4882 are not interested in stepping through @code{boring}. If you run @code{step}
4883 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4884 step over both @code{foo} and @code{boring}!
4886 One solution is to @code{step} into @code{boring} and use the @code{finish}
4887 command to immediately exit it. But this can become tedious if @code{boring}
4888 is called from many places.
4890 A more flexible solution is to execute @kbd{skip boring}. This instructs
4891 @value{GDBN} never to step into @code{boring}. Now when you execute
4892 @code{step} at line 103, you'll step over @code{boring} and directly into
4895 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4896 example, @code{skip file boring.c}.
4899 @kindex skip function
4900 @item skip @r{[}@var{linespec}@r{]}
4901 @itemx skip function @r{[}@var{linespec}@r{]}
4902 After running this command, the function named by @var{linespec} or the
4903 function containing the line named by @var{linespec} will be skipped over when
4904 stepping. @xref{Specify Location}.
4906 If you do not specify @var{linespec}, the function you're currently debugging
4909 (If you have a function called @code{file} that you want to skip, use
4910 @kbd{skip function file}.)
4913 @item skip file @r{[}@var{filename}@r{]}
4914 After running this command, any function whose source lives in @var{filename}
4915 will be skipped over when stepping.
4917 If you do not specify @var{filename}, functions whose source lives in the file
4918 you're currently debugging will be skipped.
4921 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4922 These are the commands for managing your list of skips:
4926 @item info skip @r{[}@var{range}@r{]}
4927 Print details about the specified skip(s). If @var{range} is not specified,
4928 print a table with details about all functions and files marked for skipping.
4929 @code{info skip} prints the following information about each skip:
4933 A number identifying this skip.
4935 The type of this skip, either @samp{function} or @samp{file}.
4936 @item Enabled or Disabled
4937 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4939 For function skips, this column indicates the address in memory of the function
4940 being skipped. If you've set a function skip on a function which has not yet
4941 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4942 which has the function is loaded, @code{info skip} will show the function's
4945 For file skips, this field contains the filename being skipped. For functions
4946 skips, this field contains the function name and its line number in the file
4947 where it is defined.
4951 @item skip delete @r{[}@var{range}@r{]}
4952 Delete the specified skip(s). If @var{range} is not specified, delete all
4956 @item skip enable @r{[}@var{range}@r{]}
4957 Enable the specified skip(s). If @var{range} is not specified, enable all
4960 @kindex skip disable
4961 @item skip disable @r{[}@var{range}@r{]}
4962 Disable the specified skip(s). If @var{range} is not specified, disable all
4971 A signal is an asynchronous event that can happen in a program. The
4972 operating system defines the possible kinds of signals, and gives each
4973 kind a name and a number. For example, in Unix @code{SIGINT} is the
4974 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4975 @code{SIGSEGV} is the signal a program gets from referencing a place in
4976 memory far away from all the areas in use; @code{SIGALRM} occurs when
4977 the alarm clock timer goes off (which happens only if your program has
4978 requested an alarm).
4980 @cindex fatal signals
4981 Some signals, including @code{SIGALRM}, are a normal part of the
4982 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4983 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4984 program has not specified in advance some other way to handle the signal.
4985 @code{SIGINT} does not indicate an error in your program, but it is normally
4986 fatal so it can carry out the purpose of the interrupt: to kill the program.
4988 @value{GDBN} has the ability to detect any occurrence of a signal in your
4989 program. You can tell @value{GDBN} in advance what to do for each kind of
4992 @cindex handling signals
4993 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4994 @code{SIGALRM} be silently passed to your program
4995 (so as not to interfere with their role in the program's functioning)
4996 but to stop your program immediately whenever an error signal happens.
4997 You can change these settings with the @code{handle} command.
5000 @kindex info signals
5004 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5005 handle each one. You can use this to see the signal numbers of all
5006 the defined types of signals.
5008 @item info signals @var{sig}
5009 Similar, but print information only about the specified signal number.
5011 @code{info handle} is an alias for @code{info signals}.
5014 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5015 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5016 can be the number of a signal or its name (with or without the
5017 @samp{SIG} at the beginning); a list of signal numbers of the form
5018 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5019 known signals. Optional arguments @var{keywords}, described below,
5020 say what change to make.
5024 The keywords allowed by the @code{handle} command can be abbreviated.
5025 Their full names are:
5029 @value{GDBN} should not stop your program when this signal happens. It may
5030 still print a message telling you that the signal has come in.
5033 @value{GDBN} should stop your program when this signal happens. This implies
5034 the @code{print} keyword as well.
5037 @value{GDBN} should print a message when this signal happens.
5040 @value{GDBN} should not mention the occurrence of the signal at all. This
5041 implies the @code{nostop} keyword as well.
5045 @value{GDBN} should allow your program to see this signal; your program
5046 can handle the signal, or else it may terminate if the signal is fatal
5047 and not handled. @code{pass} and @code{noignore} are synonyms.
5051 @value{GDBN} should not allow your program to see this signal.
5052 @code{nopass} and @code{ignore} are synonyms.
5056 When a signal stops your program, the signal is not visible to the
5058 continue. Your program sees the signal then, if @code{pass} is in
5059 effect for the signal in question @emph{at that time}. In other words,
5060 after @value{GDBN} reports a signal, you can use the @code{handle}
5061 command with @code{pass} or @code{nopass} to control whether your
5062 program sees that signal when you continue.
5064 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5065 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5066 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5069 You can also use the @code{signal} command to prevent your program from
5070 seeing a signal, or cause it to see a signal it normally would not see,
5071 or to give it any signal at any time. For example, if your program stopped
5072 due to some sort of memory reference error, you might store correct
5073 values into the erroneous variables and continue, hoping to see more
5074 execution; but your program would probably terminate immediately as
5075 a result of the fatal signal once it saw the signal. To prevent this,
5076 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5079 @cindex extra signal information
5080 @anchor{extra signal information}
5082 On some targets, @value{GDBN} can inspect extra signal information
5083 associated with the intercepted signal, before it is actually
5084 delivered to the program being debugged. This information is exported
5085 by the convenience variable @code{$_siginfo}, and consists of data
5086 that is passed by the kernel to the signal handler at the time of the
5087 receipt of a signal. The data type of the information itself is
5088 target dependent. You can see the data type using the @code{ptype
5089 $_siginfo} command. On Unix systems, it typically corresponds to the
5090 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5093 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5094 referenced address that raised a segmentation fault.
5098 (@value{GDBP}) continue
5099 Program received signal SIGSEGV, Segmentation fault.
5100 0x0000000000400766 in main ()
5102 (@value{GDBP}) ptype $_siginfo
5109 struct @{...@} _kill;
5110 struct @{...@} _timer;
5112 struct @{...@} _sigchld;
5113 struct @{...@} _sigfault;
5114 struct @{...@} _sigpoll;
5117 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5121 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5122 $1 = (void *) 0x7ffff7ff7000
5126 Depending on target support, @code{$_siginfo} may also be writable.
5129 @section Stopping and Starting Multi-thread Programs
5131 @cindex stopped threads
5132 @cindex threads, stopped
5134 @cindex continuing threads
5135 @cindex threads, continuing
5137 @value{GDBN} supports debugging programs with multiple threads
5138 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5139 are two modes of controlling execution of your program within the
5140 debugger. In the default mode, referred to as @dfn{all-stop mode},
5141 when any thread in your program stops (for example, at a breakpoint
5142 or while being stepped), all other threads in the program are also stopped by
5143 @value{GDBN}. On some targets, @value{GDBN} also supports
5144 @dfn{non-stop mode}, in which other threads can continue to run freely while
5145 you examine the stopped thread in the debugger.
5148 * All-Stop Mode:: All threads stop when GDB takes control
5149 * Non-Stop Mode:: Other threads continue to execute
5150 * Background Execution:: Running your program asynchronously
5151 * Thread-Specific Breakpoints:: Controlling breakpoints
5152 * Interrupted System Calls:: GDB may interfere with system calls
5153 * Observer Mode:: GDB does not alter program behavior
5157 @subsection All-Stop Mode
5159 @cindex all-stop mode
5161 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5162 @emph{all} threads of execution stop, not just the current thread. This
5163 allows you to examine the overall state of the program, including
5164 switching between threads, without worrying that things may change
5167 Conversely, whenever you restart the program, @emph{all} threads start
5168 executing. @emph{This is true even when single-stepping} with commands
5169 like @code{step} or @code{next}.
5171 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5172 Since thread scheduling is up to your debugging target's operating
5173 system (not controlled by @value{GDBN}), other threads may
5174 execute more than one statement while the current thread completes a
5175 single step. Moreover, in general other threads stop in the middle of a
5176 statement, rather than at a clean statement boundary, when the program
5179 You might even find your program stopped in another thread after
5180 continuing or even single-stepping. This happens whenever some other
5181 thread runs into a breakpoint, a signal, or an exception before the
5182 first thread completes whatever you requested.
5184 @cindex automatic thread selection
5185 @cindex switching threads automatically
5186 @cindex threads, automatic switching
5187 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5188 signal, it automatically selects the thread where that breakpoint or
5189 signal happened. @value{GDBN} alerts you to the context switch with a
5190 message such as @samp{[Switching to Thread @var{n}]} to identify the
5193 On some OSes, you can modify @value{GDBN}'s default behavior by
5194 locking the OS scheduler to allow only a single thread to run.
5197 @item set scheduler-locking @var{mode}
5198 @cindex scheduler locking mode
5199 @cindex lock scheduler
5200 Set the scheduler locking mode. If it is @code{off}, then there is no
5201 locking and any thread may run at any time. If @code{on}, then only the
5202 current thread may run when the inferior is resumed. The @code{step}
5203 mode optimizes for single-stepping; it prevents other threads
5204 from preempting the current thread while you are stepping, so that
5205 the focus of debugging does not change unexpectedly.
5206 Other threads only rarely (or never) get a chance to run
5207 when you step. They are more likely to run when you @samp{next} over a
5208 function call, and they are completely free to run when you use commands
5209 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5210 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5211 the current thread away from the thread that you are debugging.
5213 @item show scheduler-locking
5214 Display the current scheduler locking mode.
5217 @cindex resume threads of multiple processes simultaneously
5218 By default, when you issue one of the execution commands such as
5219 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5220 threads of the current inferior to run. For example, if @value{GDBN}
5221 is attached to two inferiors, each with two threads, the
5222 @code{continue} command resumes only the two threads of the current
5223 inferior. This is useful, for example, when you debug a program that
5224 forks and you want to hold the parent stopped (so that, for instance,
5225 it doesn't run to exit), while you debug the child. In other
5226 situations, you may not be interested in inspecting the current state
5227 of any of the processes @value{GDBN} is attached to, and you may want
5228 to resume them all until some breakpoint is hit. In the latter case,
5229 you can instruct @value{GDBN} to allow all threads of all the
5230 inferiors to run with the @w{@code{set schedule-multiple}} command.
5233 @kindex set schedule-multiple
5234 @item set schedule-multiple
5235 Set the mode for allowing threads of multiple processes to be resumed
5236 when an execution command is issued. When @code{on}, all threads of
5237 all processes are allowed to run. When @code{off}, only the threads
5238 of the current process are resumed. The default is @code{off}. The
5239 @code{scheduler-locking} mode takes precedence when set to @code{on},
5240 or while you are stepping and set to @code{step}.
5242 @item show schedule-multiple
5243 Display the current mode for resuming the execution of threads of
5248 @subsection Non-Stop Mode
5250 @cindex non-stop mode
5252 @c This section is really only a place-holder, and needs to be expanded
5253 @c with more details.
5255 For some multi-threaded targets, @value{GDBN} supports an optional
5256 mode of operation in which you can examine stopped program threads in
5257 the debugger while other threads continue to execute freely. This
5258 minimizes intrusion when debugging live systems, such as programs
5259 where some threads have real-time constraints or must continue to
5260 respond to external events. This is referred to as @dfn{non-stop} mode.
5262 In non-stop mode, when a thread stops to report a debugging event,
5263 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5264 threads as well, in contrast to the all-stop mode behavior. Additionally,
5265 execution commands such as @code{continue} and @code{step} apply by default
5266 only to the current thread in non-stop mode, rather than all threads as
5267 in all-stop mode. This allows you to control threads explicitly in
5268 ways that are not possible in all-stop mode --- for example, stepping
5269 one thread while allowing others to run freely, stepping
5270 one thread while holding all others stopped, or stepping several threads
5271 independently and simultaneously.
5273 To enter non-stop mode, use this sequence of commands before you run
5274 or attach to your program:
5277 # Enable the async interface.
5280 # If using the CLI, pagination breaks non-stop.
5283 # Finally, turn it on!
5287 You can use these commands to manipulate the non-stop mode setting:
5290 @kindex set non-stop
5291 @item set non-stop on
5292 Enable selection of non-stop mode.
5293 @item set non-stop off
5294 Disable selection of non-stop mode.
5295 @kindex show non-stop
5297 Show the current non-stop enablement setting.
5300 Note these commands only reflect whether non-stop mode is enabled,
5301 not whether the currently-executing program is being run in non-stop mode.
5302 In particular, the @code{set non-stop} preference is only consulted when
5303 @value{GDBN} starts or connects to the target program, and it is generally
5304 not possible to switch modes once debugging has started. Furthermore,
5305 since not all targets support non-stop mode, even when you have enabled
5306 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5309 In non-stop mode, all execution commands apply only to the current thread
5310 by default. That is, @code{continue} only continues one thread.
5311 To continue all threads, issue @code{continue -a} or @code{c -a}.
5313 You can use @value{GDBN}'s background execution commands
5314 (@pxref{Background Execution}) to run some threads in the background
5315 while you continue to examine or step others from @value{GDBN}.
5316 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5317 always executed asynchronously in non-stop mode.
5319 Suspending execution is done with the @code{interrupt} command when
5320 running in the background, or @kbd{Ctrl-c} during foreground execution.
5321 In all-stop mode, this stops the whole process;
5322 but in non-stop mode the interrupt applies only to the current thread.
5323 To stop the whole program, use @code{interrupt -a}.
5325 Other execution commands do not currently support the @code{-a} option.
5327 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5328 that thread current, as it does in all-stop mode. This is because the
5329 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5330 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5331 changed to a different thread just as you entered a command to operate on the
5332 previously current thread.
5334 @node Background Execution
5335 @subsection Background Execution
5337 @cindex foreground execution
5338 @cindex background execution
5339 @cindex asynchronous execution
5340 @cindex execution, foreground, background and asynchronous
5342 @value{GDBN}'s execution commands have two variants: the normal
5343 foreground (synchronous) behavior, and a background
5344 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5345 the program to report that some thread has stopped before prompting for
5346 another command. In background execution, @value{GDBN} immediately gives
5347 a command prompt so that you can issue other commands while your program runs.
5349 You need to explicitly enable asynchronous mode before you can use
5350 background execution commands. You can use these commands to
5351 manipulate the asynchronous mode setting:
5354 @kindex set target-async
5355 @item set target-async on
5356 Enable asynchronous mode.
5357 @item set target-async off
5358 Disable asynchronous mode.
5359 @kindex show target-async
5360 @item show target-async
5361 Show the current target-async setting.
5364 If the target doesn't support async mode, @value{GDBN} issues an error
5365 message if you attempt to use the background execution commands.
5367 To specify background execution, add a @code{&} to the command. For example,
5368 the background form of the @code{continue} command is @code{continue&}, or
5369 just @code{c&}. The execution commands that accept background execution
5375 @xref{Starting, , Starting your Program}.
5379 @xref{Attach, , Debugging an Already-running Process}.
5383 @xref{Continuing and Stepping, step}.
5387 @xref{Continuing and Stepping, stepi}.
5391 @xref{Continuing and Stepping, next}.
5395 @xref{Continuing and Stepping, nexti}.
5399 @xref{Continuing and Stepping, continue}.
5403 @xref{Continuing and Stepping, finish}.
5407 @xref{Continuing and Stepping, until}.
5411 Background execution is especially useful in conjunction with non-stop
5412 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5413 However, you can also use these commands in the normal all-stop mode with
5414 the restriction that you cannot issue another execution command until the
5415 previous one finishes. Examples of commands that are valid in all-stop
5416 mode while the program is running include @code{help} and @code{info break}.
5418 You can interrupt your program while it is running in the background by
5419 using the @code{interrupt} command.
5426 Suspend execution of the running program. In all-stop mode,
5427 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5428 only the current thread. To stop the whole program in non-stop mode,
5429 use @code{interrupt -a}.
5432 @node Thread-Specific Breakpoints
5433 @subsection Thread-Specific Breakpoints
5435 When your program has multiple threads (@pxref{Threads,, Debugging
5436 Programs with Multiple Threads}), you can choose whether to set
5437 breakpoints on all threads, or on a particular thread.
5440 @cindex breakpoints and threads
5441 @cindex thread breakpoints
5442 @kindex break @dots{} thread @var{threadno}
5443 @item break @var{linespec} thread @var{threadno}
5444 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5445 @var{linespec} specifies source lines; there are several ways of
5446 writing them (@pxref{Specify Location}), but the effect is always to
5447 specify some source line.
5449 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5450 to specify that you only want @value{GDBN} to stop the program when a
5451 particular thread reaches this breakpoint. @var{threadno} is one of the
5452 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5453 column of the @samp{info threads} display.
5455 If you do not specify @samp{thread @var{threadno}} when you set a
5456 breakpoint, the breakpoint applies to @emph{all} threads of your
5459 You can use the @code{thread} qualifier on conditional breakpoints as
5460 well; in this case, place @samp{thread @var{threadno}} before or
5461 after the breakpoint condition, like this:
5464 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5469 @node Interrupted System Calls
5470 @subsection Interrupted System Calls
5472 @cindex thread breakpoints and system calls
5473 @cindex system calls and thread breakpoints
5474 @cindex premature return from system calls
5475 There is an unfortunate side effect when using @value{GDBN} to debug
5476 multi-threaded programs. If one thread stops for a
5477 breakpoint, or for some other reason, and another thread is blocked in a
5478 system call, then the system call may return prematurely. This is a
5479 consequence of the interaction between multiple threads and the signals
5480 that @value{GDBN} uses to implement breakpoints and other events that
5483 To handle this problem, your program should check the return value of
5484 each system call and react appropriately. This is good programming
5487 For example, do not write code like this:
5493 The call to @code{sleep} will return early if a different thread stops
5494 at a breakpoint or for some other reason.
5496 Instead, write this:
5501 unslept = sleep (unslept);
5504 A system call is allowed to return early, so the system is still
5505 conforming to its specification. But @value{GDBN} does cause your
5506 multi-threaded program to behave differently than it would without
5509 Also, @value{GDBN} uses internal breakpoints in the thread library to
5510 monitor certain events such as thread creation and thread destruction.
5511 When such an event happens, a system call in another thread may return
5512 prematurely, even though your program does not appear to stop.
5515 @subsection Observer Mode
5517 If you want to build on non-stop mode and observe program behavior
5518 without any chance of disruption by @value{GDBN}, you can set
5519 variables to disable all of the debugger's attempts to modify state,
5520 whether by writing memory, inserting breakpoints, etc. These operate
5521 at a low level, intercepting operations from all commands.
5523 When all of these are set to @code{off}, then @value{GDBN} is said to
5524 be @dfn{observer mode}. As a convenience, the variable
5525 @code{observer} can be set to disable these, plus enable non-stop
5528 Note that @value{GDBN} will not prevent you from making nonsensical
5529 combinations of these settings. For instance, if you have enabled
5530 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5531 then breakpoints that work by writing trap instructions into the code
5532 stream will still not be able to be placed.
5537 @item set observer on
5538 @itemx set observer off
5539 When set to @code{on}, this disables all the permission variables
5540 below (except for @code{insert-fast-tracepoints}), plus enables
5541 non-stop debugging. Setting this to @code{off} switches back to
5542 normal debugging, though remaining in non-stop mode.
5545 Show whether observer mode is on or off.
5547 @kindex may-write-registers
5548 @item set may-write-registers on
5549 @itemx set may-write-registers off
5550 This controls whether @value{GDBN} will attempt to alter the values of
5551 registers, such as with assignment expressions in @code{print}, or the
5552 @code{jump} command. It defaults to @code{on}.
5554 @item show may-write-registers
5555 Show the current permission to write registers.
5557 @kindex may-write-memory
5558 @item set may-write-memory on
5559 @itemx set may-write-memory off
5560 This controls whether @value{GDBN} will attempt to alter the contents
5561 of memory, such as with assignment expressions in @code{print}. It
5562 defaults to @code{on}.
5564 @item show may-write-memory
5565 Show the current permission to write memory.
5567 @kindex may-insert-breakpoints
5568 @item set may-insert-breakpoints on
5569 @itemx set may-insert-breakpoints off
5570 This controls whether @value{GDBN} will attempt to insert breakpoints.
5571 This affects all breakpoints, including internal breakpoints defined
5572 by @value{GDBN}. It defaults to @code{on}.
5574 @item show may-insert-breakpoints
5575 Show the current permission to insert breakpoints.
5577 @kindex may-insert-tracepoints
5578 @item set may-insert-tracepoints on
5579 @itemx set may-insert-tracepoints off
5580 This controls whether @value{GDBN} will attempt to insert (regular)
5581 tracepoints at the beginning of a tracing experiment. It affects only
5582 non-fast tracepoints, fast tracepoints being under the control of
5583 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5585 @item show may-insert-tracepoints
5586 Show the current permission to insert tracepoints.
5588 @kindex may-insert-fast-tracepoints
5589 @item set may-insert-fast-tracepoints on
5590 @itemx set may-insert-fast-tracepoints off
5591 This controls whether @value{GDBN} will attempt to insert fast
5592 tracepoints at the beginning of a tracing experiment. It affects only
5593 fast tracepoints, regular (non-fast) tracepoints being under the
5594 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5596 @item show may-insert-fast-tracepoints
5597 Show the current permission to insert fast tracepoints.
5599 @kindex may-interrupt
5600 @item set may-interrupt on
5601 @itemx set may-interrupt off
5602 This controls whether @value{GDBN} will attempt to interrupt or stop
5603 program execution. When this variable is @code{off}, the
5604 @code{interrupt} command will have no effect, nor will
5605 @kbd{Ctrl-c}. It defaults to @code{on}.
5607 @item show may-interrupt
5608 Show the current permission to interrupt or stop the program.
5612 @node Reverse Execution
5613 @chapter Running programs backward
5614 @cindex reverse execution
5615 @cindex running programs backward
5617 When you are debugging a program, it is not unusual to realize that
5618 you have gone too far, and some event of interest has already happened.
5619 If the target environment supports it, @value{GDBN} can allow you to
5620 ``rewind'' the program by running it backward.
5622 A target environment that supports reverse execution should be able
5623 to ``undo'' the changes in machine state that have taken place as the
5624 program was executing normally. Variables, registers etc.@: should
5625 revert to their previous values. Obviously this requires a great
5626 deal of sophistication on the part of the target environment; not
5627 all target environments can support reverse execution.
5629 When a program is executed in reverse, the instructions that
5630 have most recently been executed are ``un-executed'', in reverse
5631 order. The program counter runs backward, following the previous
5632 thread of execution in reverse. As each instruction is ``un-executed'',
5633 the values of memory and/or registers that were changed by that
5634 instruction are reverted to their previous states. After executing
5635 a piece of source code in reverse, all side effects of that code
5636 should be ``undone'', and all variables should be returned to their
5637 prior values@footnote{
5638 Note that some side effects are easier to undo than others. For instance,
5639 memory and registers are relatively easy, but device I/O is hard. Some
5640 targets may be able undo things like device I/O, and some may not.
5642 The contract between @value{GDBN} and the reverse executing target
5643 requires only that the target do something reasonable when
5644 @value{GDBN} tells it to execute backwards, and then report the
5645 results back to @value{GDBN}. Whatever the target reports back to
5646 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5647 assumes that the memory and registers that the target reports are in a
5648 consistant state, but @value{GDBN} accepts whatever it is given.
5651 If you are debugging in a target environment that supports
5652 reverse execution, @value{GDBN} provides the following commands.
5655 @kindex reverse-continue
5656 @kindex rc @r{(@code{reverse-continue})}
5657 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5658 @itemx rc @r{[}@var{ignore-count}@r{]}
5659 Beginning at the point where your program last stopped, start executing
5660 in reverse. Reverse execution will stop for breakpoints and synchronous
5661 exceptions (signals), just like normal execution. Behavior of
5662 asynchronous signals depends on the target environment.
5664 @kindex reverse-step
5665 @kindex rs @r{(@code{step})}
5666 @item reverse-step @r{[}@var{count}@r{]}
5667 Run the program backward until control reaches the start of a
5668 different source line; then stop it, and return control to @value{GDBN}.
5670 Like the @code{step} command, @code{reverse-step} will only stop
5671 at the beginning of a source line. It ``un-executes'' the previously
5672 executed source line. If the previous source line included calls to
5673 debuggable functions, @code{reverse-step} will step (backward) into
5674 the called function, stopping at the beginning of the @emph{last}
5675 statement in the called function (typically a return statement).
5677 Also, as with the @code{step} command, if non-debuggable functions are
5678 called, @code{reverse-step} will run thru them backward without stopping.
5680 @kindex reverse-stepi
5681 @kindex rsi @r{(@code{reverse-stepi})}
5682 @item reverse-stepi @r{[}@var{count}@r{]}
5683 Reverse-execute one machine instruction. Note that the instruction
5684 to be reverse-executed is @emph{not} the one pointed to by the program
5685 counter, but the instruction executed prior to that one. For instance,
5686 if the last instruction was a jump, @code{reverse-stepi} will take you
5687 back from the destination of the jump to the jump instruction itself.
5689 @kindex reverse-next
5690 @kindex rn @r{(@code{reverse-next})}
5691 @item reverse-next @r{[}@var{count}@r{]}
5692 Run backward to the beginning of the previous line executed in
5693 the current (innermost) stack frame. If the line contains function
5694 calls, they will be ``un-executed'' without stopping. Starting from
5695 the first line of a function, @code{reverse-next} will take you back
5696 to the caller of that function, @emph{before} the function was called,
5697 just as the normal @code{next} command would take you from the last
5698 line of a function back to its return to its caller
5699 @footnote{Unless the code is too heavily optimized.}.
5701 @kindex reverse-nexti
5702 @kindex rni @r{(@code{reverse-nexti})}
5703 @item reverse-nexti @r{[}@var{count}@r{]}
5704 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5705 in reverse, except that called functions are ``un-executed'' atomically.
5706 That is, if the previously executed instruction was a return from
5707 another function, @code{reverse-nexti} will continue to execute
5708 in reverse until the call to that function (from the current stack
5711 @kindex reverse-finish
5712 @item reverse-finish
5713 Just as the @code{finish} command takes you to the point where the
5714 current function returns, @code{reverse-finish} takes you to the point
5715 where it was called. Instead of ending up at the end of the current
5716 function invocation, you end up at the beginning.
5718 @kindex set exec-direction
5719 @item set exec-direction
5720 Set the direction of target execution.
5721 @itemx set exec-direction reverse
5722 @cindex execute forward or backward in time
5723 @value{GDBN} will perform all execution commands in reverse, until the
5724 exec-direction mode is changed to ``forward''. Affected commands include
5725 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5726 command cannot be used in reverse mode.
5727 @item set exec-direction forward
5728 @value{GDBN} will perform all execution commands in the normal fashion.
5729 This is the default.
5733 @node Process Record and Replay
5734 @chapter Recording Inferior's Execution and Replaying It
5735 @cindex process record and replay
5736 @cindex recording inferior's execution and replaying it
5738 On some platforms, @value{GDBN} provides a special @dfn{process record
5739 and replay} target that can record a log of the process execution, and
5740 replay it later with both forward and reverse execution commands.
5743 When this target is in use, if the execution log includes the record
5744 for the next instruction, @value{GDBN} will debug in @dfn{replay
5745 mode}. In the replay mode, the inferior does not really execute code
5746 instructions. Instead, all the events that normally happen during
5747 code execution are taken from the execution log. While code is not
5748 really executed in replay mode, the values of registers (including the
5749 program counter register) and the memory of the inferior are still
5750 changed as they normally would. Their contents are taken from the
5754 If the record for the next instruction is not in the execution log,
5755 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5756 inferior executes normally, and @value{GDBN} records the execution log
5759 The process record and replay target supports reverse execution
5760 (@pxref{Reverse Execution}), even if the platform on which the
5761 inferior runs does not. However, the reverse execution is limited in
5762 this case by the range of the instructions recorded in the execution
5763 log. In other words, reverse execution on platforms that don't
5764 support it directly can only be done in the replay mode.
5766 When debugging in the reverse direction, @value{GDBN} will work in
5767 replay mode as long as the execution log includes the record for the
5768 previous instruction; otherwise, it will work in record mode, if the
5769 platform supports reverse execution, or stop if not.
5771 For architecture environments that support process record and replay,
5772 @value{GDBN} provides the following commands:
5775 @kindex target record
5779 This command starts the process record and replay target. The process
5780 record and replay target can only debug a process that is already
5781 running. Therefore, you need first to start the process with the
5782 @kbd{run} or @kbd{start} commands, and then start the recording with
5783 the @kbd{target record} command.
5785 Both @code{record} and @code{rec} are aliases of @code{target record}.
5787 @cindex displaced stepping, and process record and replay
5788 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5789 will be automatically disabled when process record and replay target
5790 is started. That's because the process record and replay target
5791 doesn't support displaced stepping.
5793 @cindex non-stop mode, and process record and replay
5794 @cindex asynchronous execution, and process record and replay
5795 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5796 the asynchronous execution mode (@pxref{Background Execution}), the
5797 process record and replay target cannot be started because it doesn't
5798 support these two modes.
5803 Stop the process record and replay target. When process record and
5804 replay target stops, the entire execution log will be deleted and the
5805 inferior will either be terminated, or will remain in its final state.
5807 When you stop the process record and replay target in record mode (at
5808 the end of the execution log), the inferior will be stopped at the
5809 next instruction that would have been recorded. In other words, if
5810 you record for a while and then stop recording, the inferior process
5811 will be left in the same state as if the recording never happened.
5813 On the other hand, if the process record and replay target is stopped
5814 while in replay mode (that is, not at the end of the execution log,
5815 but at some earlier point), the inferior process will become ``live''
5816 at that earlier state, and it will then be possible to continue the
5817 usual ``live'' debugging of the process from that state.
5819 When the inferior process exits, or @value{GDBN} detaches from it,
5820 process record and replay target will automatically stop itself.
5823 @item record save @var{filename}
5824 Save the execution log to a file @file{@var{filename}}.
5825 Default filename is @file{gdb_record.@var{process_id}}, where
5826 @var{process_id} is the process ID of the inferior.
5828 @kindex record restore
5829 @item record restore @var{filename}
5830 Restore the execution log from a file @file{@var{filename}}.
5831 File must have been created with @code{record save}.
5833 @kindex set record insn-number-max
5834 @item set record insn-number-max @var{limit}
5835 Set the limit of instructions to be recorded. Default value is 200000.
5837 If @var{limit} is a positive number, then @value{GDBN} will start
5838 deleting instructions from the log once the number of the record
5839 instructions becomes greater than @var{limit}. For every new recorded
5840 instruction, @value{GDBN} will delete the earliest recorded
5841 instruction to keep the number of recorded instructions at the limit.
5842 (Since deleting recorded instructions loses information, @value{GDBN}
5843 lets you control what happens when the limit is reached, by means of
5844 the @code{stop-at-limit} option, described below.)
5846 If @var{limit} is zero, @value{GDBN} will never delete recorded
5847 instructions from the execution log. The number of recorded
5848 instructions is unlimited in this case.
5850 @kindex show record insn-number-max
5851 @item show record insn-number-max
5852 Show the limit of instructions to be recorded.
5854 @kindex set record stop-at-limit
5855 @item set record stop-at-limit
5856 Control the behavior when the number of recorded instructions reaches
5857 the limit. If ON (the default), @value{GDBN} will stop when the limit
5858 is reached for the first time and ask you whether you want to stop the
5859 inferior or continue running it and recording the execution log. If
5860 you decide to continue recording, each new recorded instruction will
5861 cause the oldest one to be deleted.
5863 If this option is OFF, @value{GDBN} will automatically delete the
5864 oldest record to make room for each new one, without asking.
5866 @kindex show record stop-at-limit
5867 @item show record stop-at-limit
5868 Show the current setting of @code{stop-at-limit}.
5870 @kindex set record memory-query
5871 @item set record memory-query
5872 Control the behavior when @value{GDBN} is unable to record memory
5873 changes caused by an instruction. If ON, @value{GDBN} will query
5874 whether to stop the inferior in that case.
5876 If this option is OFF (the default), @value{GDBN} will automatically
5877 ignore the effect of such instructions on memory. Later, when
5878 @value{GDBN} replays this execution log, it will mark the log of this
5879 instruction as not accessible, and it will not affect the replay
5882 @kindex show record memory-query
5883 @item show record memory-query
5884 Show the current setting of @code{memory-query}.
5888 Show various statistics about the state of process record and its
5889 in-memory execution log buffer, including:
5893 Whether in record mode or replay mode.
5895 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5897 Highest recorded instruction number.
5899 Current instruction about to be replayed (if in replay mode).
5901 Number of instructions contained in the execution log.
5903 Maximum number of instructions that may be contained in the execution log.
5906 @kindex record delete
5909 When record target runs in replay mode (``in the past''), delete the
5910 subsequent execution log and begin to record a new execution log starting
5911 from the current address. This means you will abandon the previously
5912 recorded ``future'' and begin recording a new ``future''.
5917 @chapter Examining the Stack
5919 When your program has stopped, the first thing you need to know is where it
5920 stopped and how it got there.
5923 Each time your program performs a function call, information about the call
5925 That information includes the location of the call in your program,
5926 the arguments of the call,
5927 and the local variables of the function being called.
5928 The information is saved in a block of data called a @dfn{stack frame}.
5929 The stack frames are allocated in a region of memory called the @dfn{call
5932 When your program stops, the @value{GDBN} commands for examining the
5933 stack allow you to see all of this information.
5935 @cindex selected frame
5936 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5937 @value{GDBN} commands refer implicitly to the selected frame. In
5938 particular, whenever you ask @value{GDBN} for the value of a variable in
5939 your program, the value is found in the selected frame. There are
5940 special @value{GDBN} commands to select whichever frame you are
5941 interested in. @xref{Selection, ,Selecting a Frame}.
5943 When your program stops, @value{GDBN} automatically selects the
5944 currently executing frame and describes it briefly, similar to the
5945 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5948 * Frames:: Stack frames
5949 * Backtrace:: Backtraces
5950 * Selection:: Selecting a frame
5951 * Frame Info:: Information on a frame
5956 @section Stack Frames
5958 @cindex frame, definition
5960 The call stack is divided up into contiguous pieces called @dfn{stack
5961 frames}, or @dfn{frames} for short; each frame is the data associated
5962 with one call to one function. The frame contains the arguments given
5963 to the function, the function's local variables, and the address at
5964 which the function is executing.
5966 @cindex initial frame
5967 @cindex outermost frame
5968 @cindex innermost frame
5969 When your program is started, the stack has only one frame, that of the
5970 function @code{main}. This is called the @dfn{initial} frame or the
5971 @dfn{outermost} frame. Each time a function is called, a new frame is
5972 made. Each time a function returns, the frame for that function invocation
5973 is eliminated. If a function is recursive, there can be many frames for
5974 the same function. The frame for the function in which execution is
5975 actually occurring is called the @dfn{innermost} frame. This is the most
5976 recently created of all the stack frames that still exist.
5978 @cindex frame pointer
5979 Inside your program, stack frames are identified by their addresses. A
5980 stack frame consists of many bytes, each of which has its own address; each
5981 kind of computer has a convention for choosing one byte whose
5982 address serves as the address of the frame. Usually this address is kept
5983 in a register called the @dfn{frame pointer register}
5984 (@pxref{Registers, $fp}) while execution is going on in that frame.
5986 @cindex frame number
5987 @value{GDBN} assigns numbers to all existing stack frames, starting with
5988 zero for the innermost frame, one for the frame that called it,
5989 and so on upward. These numbers do not really exist in your program;
5990 they are assigned by @value{GDBN} to give you a way of designating stack
5991 frames in @value{GDBN} commands.
5993 @c The -fomit-frame-pointer below perennially causes hbox overflow
5994 @c underflow problems.
5995 @cindex frameless execution
5996 Some compilers provide a way to compile functions so that they operate
5997 without stack frames. (For example, the @value{NGCC} option
5999 @samp{-fomit-frame-pointer}
6001 generates functions without a frame.)
6002 This is occasionally done with heavily used library functions to save
6003 the frame setup time. @value{GDBN} has limited facilities for dealing
6004 with these function invocations. If the innermost function invocation
6005 has no stack frame, @value{GDBN} nevertheless regards it as though
6006 it had a separate frame, which is numbered zero as usual, allowing
6007 correct tracing of the function call chain. However, @value{GDBN} has
6008 no provision for frameless functions elsewhere in the stack.
6011 @kindex frame@r{, command}
6012 @cindex current stack frame
6013 @item frame @var{args}
6014 The @code{frame} command allows you to move from one stack frame to another,
6015 and to print the stack frame you select. @var{args} may be either the
6016 address of the frame or the stack frame number. Without an argument,
6017 @code{frame} prints the current stack frame.
6019 @kindex select-frame
6020 @cindex selecting frame silently
6022 The @code{select-frame} command allows you to move from one stack frame
6023 to another without printing the frame. This is the silent version of
6031 @cindex call stack traces
6032 A backtrace is a summary of how your program got where it is. It shows one
6033 line per frame, for many frames, starting with the currently executing
6034 frame (frame zero), followed by its caller (frame one), and on up the
6039 @kindex bt @r{(@code{backtrace})}
6042 Print a backtrace of the entire stack: one line per frame for all
6043 frames in the stack.
6045 You can stop the backtrace at any time by typing the system interrupt
6046 character, normally @kbd{Ctrl-c}.
6048 @item backtrace @var{n}
6050 Similar, but print only the innermost @var{n} frames.
6052 @item backtrace -@var{n}
6054 Similar, but print only the outermost @var{n} frames.
6056 @item backtrace full
6058 @itemx bt full @var{n}
6059 @itemx bt full -@var{n}
6060 Print the values of the local variables also. @var{n} specifies the
6061 number of frames to print, as described above.
6066 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6067 are additional aliases for @code{backtrace}.
6069 @cindex multiple threads, backtrace
6070 In a multi-threaded program, @value{GDBN} by default shows the
6071 backtrace only for the current thread. To display the backtrace for
6072 several or all of the threads, use the command @code{thread apply}
6073 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6074 apply all backtrace}, @value{GDBN} will display the backtrace for all
6075 the threads; this is handy when you debug a core dump of a
6076 multi-threaded program.
6078 Each line in the backtrace shows the frame number and the function name.
6079 The program counter value is also shown---unless you use @code{set
6080 print address off}. The backtrace also shows the source file name and
6081 line number, as well as the arguments to the function. The program
6082 counter value is omitted if it is at the beginning of the code for that
6085 Here is an example of a backtrace. It was made with the command
6086 @samp{bt 3}, so it shows the innermost three frames.
6090 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6092 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6093 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6095 (More stack frames follow...)
6100 The display for frame zero does not begin with a program counter
6101 value, indicating that your program has stopped at the beginning of the
6102 code for line @code{993} of @code{builtin.c}.
6105 The value of parameter @code{data} in frame 1 has been replaced by
6106 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6107 only if it is a scalar (integer, pointer, enumeration, etc). See command
6108 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6109 on how to configure the way function parameter values are printed.
6111 @cindex optimized out, in backtrace
6112 @cindex function call arguments, optimized out
6113 If your program was compiled with optimizations, some compilers will
6114 optimize away arguments passed to functions if those arguments are
6115 never used after the call. Such optimizations generate code that
6116 passes arguments through registers, but doesn't store those arguments
6117 in the stack frame. @value{GDBN} has no way of displaying such
6118 arguments in stack frames other than the innermost one. Here's what
6119 such a backtrace might look like:
6123 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6125 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6126 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6128 (More stack frames follow...)
6133 The values of arguments that were not saved in their stack frames are
6134 shown as @samp{<optimized out>}.
6136 If you need to display the values of such optimized-out arguments,
6137 either deduce that from other variables whose values depend on the one
6138 you are interested in, or recompile without optimizations.
6140 @cindex backtrace beyond @code{main} function
6141 @cindex program entry point
6142 @cindex startup code, and backtrace
6143 Most programs have a standard user entry point---a place where system
6144 libraries and startup code transition into user code. For C this is
6145 @code{main}@footnote{
6146 Note that embedded programs (the so-called ``free-standing''
6147 environment) are not required to have a @code{main} function as the
6148 entry point. They could even have multiple entry points.}.
6149 When @value{GDBN} finds the entry function in a backtrace
6150 it will terminate the backtrace, to avoid tracing into highly
6151 system-specific (and generally uninteresting) code.
6153 If you need to examine the startup code, or limit the number of levels
6154 in a backtrace, you can change this behavior:
6157 @item set backtrace past-main
6158 @itemx set backtrace past-main on
6159 @kindex set backtrace
6160 Backtraces will continue past the user entry point.
6162 @item set backtrace past-main off
6163 Backtraces will stop when they encounter the user entry point. This is the
6166 @item show backtrace past-main
6167 @kindex show backtrace
6168 Display the current user entry point backtrace policy.
6170 @item set backtrace past-entry
6171 @itemx set backtrace past-entry on
6172 Backtraces will continue past the internal entry point of an application.
6173 This entry point is encoded by the linker when the application is built,
6174 and is likely before the user entry point @code{main} (or equivalent) is called.
6176 @item set backtrace past-entry off
6177 Backtraces will stop when they encounter the internal entry point of an
6178 application. This is the default.
6180 @item show backtrace past-entry
6181 Display the current internal entry point backtrace policy.
6183 @item set backtrace limit @var{n}
6184 @itemx set backtrace limit 0
6185 @cindex backtrace limit
6186 Limit the backtrace to @var{n} levels. A value of zero means
6189 @item show backtrace limit
6190 Display the current limit on backtrace levels.
6194 @section Selecting a Frame
6196 Most commands for examining the stack and other data in your program work on
6197 whichever stack frame is selected at the moment. Here are the commands for
6198 selecting a stack frame; all of them finish by printing a brief description
6199 of the stack frame just selected.
6202 @kindex frame@r{, selecting}
6203 @kindex f @r{(@code{frame})}
6206 Select frame number @var{n}. Recall that frame zero is the innermost
6207 (currently executing) frame, frame one is the frame that called the
6208 innermost one, and so on. The highest-numbered frame is the one for
6211 @item frame @var{addr}
6213 Select the frame at address @var{addr}. This is useful mainly if the
6214 chaining of stack frames has been damaged by a bug, making it
6215 impossible for @value{GDBN} to assign numbers properly to all frames. In
6216 addition, this can be useful when your program has multiple stacks and
6217 switches between them.
6219 On the SPARC architecture, @code{frame} needs two addresses to
6220 select an arbitrary frame: a frame pointer and a stack pointer.
6222 On the MIPS and Alpha architecture, it needs two addresses: a stack
6223 pointer and a program counter.
6225 On the 29k architecture, it needs three addresses: a register stack
6226 pointer, a program counter, and a memory stack pointer.
6230 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6231 advances toward the outermost frame, to higher frame numbers, to frames
6232 that have existed longer. @var{n} defaults to one.
6235 @kindex do @r{(@code{down})}
6237 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6238 advances toward the innermost frame, to lower frame numbers, to frames
6239 that were created more recently. @var{n} defaults to one. You may
6240 abbreviate @code{down} as @code{do}.
6243 All of these commands end by printing two lines of output describing the
6244 frame. The first line shows the frame number, the function name, the
6245 arguments, and the source file and line number of execution in that
6246 frame. The second line shows the text of that source line.
6254 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6256 10 read_input_file (argv[i]);
6260 After such a printout, the @code{list} command with no arguments
6261 prints ten lines centered on the point of execution in the frame.
6262 You can also edit the program at the point of execution with your favorite
6263 editing program by typing @code{edit}.
6264 @xref{List, ,Printing Source Lines},
6268 @kindex down-silently
6270 @item up-silently @var{n}
6271 @itemx down-silently @var{n}
6272 These two commands are variants of @code{up} and @code{down},
6273 respectively; they differ in that they do their work silently, without
6274 causing display of the new frame. They are intended primarily for use
6275 in @value{GDBN} command scripts, where the output might be unnecessary and
6280 @section Information About a Frame
6282 There are several other commands to print information about the selected
6288 When used without any argument, this command does not change which
6289 frame is selected, but prints a brief description of the currently
6290 selected stack frame. It can be abbreviated @code{f}. With an
6291 argument, this command is used to select a stack frame.
6292 @xref{Selection, ,Selecting a Frame}.
6295 @kindex info f @r{(@code{info frame})}
6298 This command prints a verbose description of the selected stack frame,
6303 the address of the frame
6305 the address of the next frame down (called by this frame)
6307 the address of the next frame up (caller of this frame)
6309 the language in which the source code corresponding to this frame is written
6311 the address of the frame's arguments
6313 the address of the frame's local variables
6315 the program counter saved in it (the address of execution in the caller frame)
6317 which registers were saved in the frame
6320 @noindent The verbose description is useful when
6321 something has gone wrong that has made the stack format fail to fit
6322 the usual conventions.
6324 @item info frame @var{addr}
6325 @itemx info f @var{addr}
6326 Print a verbose description of the frame at address @var{addr}, without
6327 selecting that frame. The selected frame remains unchanged by this
6328 command. This requires the same kind of address (more than one for some
6329 architectures) that you specify in the @code{frame} command.
6330 @xref{Selection, ,Selecting a Frame}.
6334 Print the arguments of the selected frame, each on a separate line.
6338 Print the local variables of the selected frame, each on a separate
6339 line. These are all variables (declared either static or automatic)
6340 accessible at the point of execution of the selected frame.
6343 @cindex catch exceptions, list active handlers
6344 @cindex exception handlers, how to list
6346 Print a list of all the exception handlers that are active in the
6347 current stack frame at the current point of execution. To see other
6348 exception handlers, visit the associated frame (using the @code{up},
6349 @code{down}, or @code{frame} commands); then type @code{info catch}.
6350 @xref{Set Catchpoints, , Setting Catchpoints}.
6356 @chapter Examining Source Files
6358 @value{GDBN} can print parts of your program's source, since the debugging
6359 information recorded in the program tells @value{GDBN} what source files were
6360 used to build it. When your program stops, @value{GDBN} spontaneously prints
6361 the line where it stopped. Likewise, when you select a stack frame
6362 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6363 execution in that frame has stopped. You can print other portions of
6364 source files by explicit command.
6366 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6367 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6368 @value{GDBN} under @sc{gnu} Emacs}.
6371 * List:: Printing source lines
6372 * Specify Location:: How to specify code locations
6373 * Edit:: Editing source files
6374 * Search:: Searching source files
6375 * Source Path:: Specifying source directories
6376 * Machine Code:: Source and machine code
6380 @section Printing Source Lines
6383 @kindex l @r{(@code{list})}
6384 To print lines from a source file, use the @code{list} command
6385 (abbreviated @code{l}). By default, ten lines are printed.
6386 There are several ways to specify what part of the file you want to
6387 print; see @ref{Specify Location}, for the full list.
6389 Here are the forms of the @code{list} command most commonly used:
6392 @item list @var{linenum}
6393 Print lines centered around line number @var{linenum} in the
6394 current source file.
6396 @item list @var{function}
6397 Print lines centered around the beginning of function
6401 Print more lines. If the last lines printed were printed with a
6402 @code{list} command, this prints lines following the last lines
6403 printed; however, if the last line printed was a solitary line printed
6404 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6405 Stack}), this prints lines centered around that line.
6408 Print lines just before the lines last printed.
6411 @cindex @code{list}, how many lines to display
6412 By default, @value{GDBN} prints ten source lines with any of these forms of
6413 the @code{list} command. You can change this using @code{set listsize}:
6416 @kindex set listsize
6417 @item set listsize @var{count}
6418 Make the @code{list} command display @var{count} source lines (unless
6419 the @code{list} argument explicitly specifies some other number).
6421 @kindex show listsize
6423 Display the number of lines that @code{list} prints.
6426 Repeating a @code{list} command with @key{RET} discards the argument,
6427 so it is equivalent to typing just @code{list}. This is more useful
6428 than listing the same lines again. An exception is made for an
6429 argument of @samp{-}; that argument is preserved in repetition so that
6430 each repetition moves up in the source file.
6432 In general, the @code{list} command expects you to supply zero, one or two
6433 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6434 of writing them (@pxref{Specify Location}), but the effect is always
6435 to specify some source line.
6437 Here is a complete description of the possible arguments for @code{list}:
6440 @item list @var{linespec}
6441 Print lines centered around the line specified by @var{linespec}.
6443 @item list @var{first},@var{last}
6444 Print lines from @var{first} to @var{last}. Both arguments are
6445 linespecs. When a @code{list} command has two linespecs, and the
6446 source file of the second linespec is omitted, this refers to
6447 the same source file as the first linespec.
6449 @item list ,@var{last}
6450 Print lines ending with @var{last}.
6452 @item list @var{first},
6453 Print lines starting with @var{first}.
6456 Print lines just after the lines last printed.
6459 Print lines just before the lines last printed.
6462 As described in the preceding table.
6465 @node Specify Location
6466 @section Specifying a Location
6467 @cindex specifying location
6470 Several @value{GDBN} commands accept arguments that specify a location
6471 of your program's code. Since @value{GDBN} is a source-level
6472 debugger, a location usually specifies some line in the source code;
6473 for that reason, locations are also known as @dfn{linespecs}.
6475 Here are all the different ways of specifying a code location that
6476 @value{GDBN} understands:
6480 Specifies the line number @var{linenum} of the current source file.
6483 @itemx +@var{offset}
6484 Specifies the line @var{offset} lines before or after the @dfn{current
6485 line}. For the @code{list} command, the current line is the last one
6486 printed; for the breakpoint commands, this is the line at which
6487 execution stopped in the currently selected @dfn{stack frame}
6488 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6489 used as the second of the two linespecs in a @code{list} command,
6490 this specifies the line @var{offset} lines up or down from the first
6493 @item @var{filename}:@var{linenum}
6494 Specifies the line @var{linenum} in the source file @var{filename}.
6496 @item @var{function}
6497 Specifies the line that begins the body of the function @var{function}.
6498 For example, in C, this is the line with the open brace.
6500 @item @var{function}:@var{label}
6501 Specifies the line where @var{label} appears in @var{function}.
6503 @item @var{filename}:@var{function}
6504 Specifies the line that begins the body of the function @var{function}
6505 in the file @var{filename}. You only need the file name with a
6506 function name to avoid ambiguity when there are identically named
6507 functions in different source files.
6510 Specifies the line at which the label named @var{label} appears.
6511 @value{GDBN} searches for the label in the function corresponding to
6512 the currently selected stack frame. If there is no current selected
6513 stack frame (for instance, if the inferior is not running), then
6514 @value{GDBN} will not search for a label.
6516 @item *@var{address}
6517 Specifies the program address @var{address}. For line-oriented
6518 commands, such as @code{list} and @code{edit}, this specifies a source
6519 line that contains @var{address}. For @code{break} and other
6520 breakpoint oriented commands, this can be used to set breakpoints in
6521 parts of your program which do not have debugging information or
6524 Here @var{address} may be any expression valid in the current working
6525 language (@pxref{Languages, working language}) that specifies a code
6526 address. In addition, as a convenience, @value{GDBN} extends the
6527 semantics of expressions used in locations to cover the situations
6528 that frequently happen during debugging. Here are the various forms
6532 @item @var{expression}
6533 Any expression valid in the current working language.
6535 @item @var{funcaddr}
6536 An address of a function or procedure derived from its name. In C,
6537 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6538 simply the function's name @var{function} (and actually a special case
6539 of a valid expression). In Pascal and Modula-2, this is
6540 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6541 (although the Pascal form also works).
6543 This form specifies the address of the function's first instruction,
6544 before the stack frame and arguments have been set up.
6546 @item '@var{filename}'::@var{funcaddr}
6547 Like @var{funcaddr} above, but also specifies the name of the source
6548 file explicitly. This is useful if the name of the function does not
6549 specify the function unambiguously, e.g., if there are several
6550 functions with identical names in different source files.
6557 @section Editing Source Files
6558 @cindex editing source files
6561 @kindex e @r{(@code{edit})}
6562 To edit the lines in a source file, use the @code{edit} command.
6563 The editing program of your choice
6564 is invoked with the current line set to
6565 the active line in the program.
6566 Alternatively, there are several ways to specify what part of the file you
6567 want to print if you want to see other parts of the program:
6570 @item edit @var{location}
6571 Edit the source file specified by @code{location}. Editing starts at
6572 that @var{location}, e.g., at the specified source line of the
6573 specified file. @xref{Specify Location}, for all the possible forms
6574 of the @var{location} argument; here are the forms of the @code{edit}
6575 command most commonly used:
6578 @item edit @var{number}
6579 Edit the current source file with @var{number} as the active line number.
6581 @item edit @var{function}
6582 Edit the file containing @var{function} at the beginning of its definition.
6587 @subsection Choosing your Editor
6588 You can customize @value{GDBN} to use any editor you want
6590 The only restriction is that your editor (say @code{ex}), recognizes the
6591 following command-line syntax:
6593 ex +@var{number} file
6595 The optional numeric value +@var{number} specifies the number of the line in
6596 the file where to start editing.}.
6597 By default, it is @file{@value{EDITOR}}, but you can change this
6598 by setting the environment variable @code{EDITOR} before using
6599 @value{GDBN}. For example, to configure @value{GDBN} to use the
6600 @code{vi} editor, you could use these commands with the @code{sh} shell:
6606 or in the @code{csh} shell,
6608 setenv EDITOR /usr/bin/vi
6613 @section Searching Source Files
6614 @cindex searching source files
6616 There are two commands for searching through the current source file for a
6621 @kindex forward-search
6622 @item forward-search @var{regexp}
6623 @itemx search @var{regexp}
6624 The command @samp{forward-search @var{regexp}} checks each line,
6625 starting with the one following the last line listed, for a match for
6626 @var{regexp}. It lists the line that is found. You can use the
6627 synonym @samp{search @var{regexp}} or abbreviate the command name as
6630 @kindex reverse-search
6631 @item reverse-search @var{regexp}
6632 The command @samp{reverse-search @var{regexp}} checks each line, starting
6633 with the one before the last line listed and going backward, for a match
6634 for @var{regexp}. It lists the line that is found. You can abbreviate
6635 this command as @code{rev}.
6639 @section Specifying Source Directories
6642 @cindex directories for source files
6643 Executable programs sometimes do not record the directories of the source
6644 files from which they were compiled, just the names. Even when they do,
6645 the directories could be moved between the compilation and your debugging
6646 session. @value{GDBN} has a list of directories to search for source files;
6647 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6648 it tries all the directories in the list, in the order they are present
6649 in the list, until it finds a file with the desired name.
6651 For example, suppose an executable references the file
6652 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6653 @file{/mnt/cross}. The file is first looked up literally; if this
6654 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6655 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6656 message is printed. @value{GDBN} does not look up the parts of the
6657 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6658 Likewise, the subdirectories of the source path are not searched: if
6659 the source path is @file{/mnt/cross}, and the binary refers to
6660 @file{foo.c}, @value{GDBN} would not find it under
6661 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6663 Plain file names, relative file names with leading directories, file
6664 names containing dots, etc.@: are all treated as described above; for
6665 instance, if the source path is @file{/mnt/cross}, and the source file
6666 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6667 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6668 that---@file{/mnt/cross/foo.c}.
6670 Note that the executable search path is @emph{not} used to locate the
6673 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6674 any information it has cached about where source files are found and where
6675 each line is in the file.
6679 When you start @value{GDBN}, its source path includes only @samp{cdir}
6680 and @samp{cwd}, in that order.
6681 To add other directories, use the @code{directory} command.
6683 The search path is used to find both program source files and @value{GDBN}
6684 script files (read using the @samp{-command} option and @samp{source} command).
6686 In addition to the source path, @value{GDBN} provides a set of commands
6687 that manage a list of source path substitution rules. A @dfn{substitution
6688 rule} specifies how to rewrite source directories stored in the program's
6689 debug information in case the sources were moved to a different
6690 directory between compilation and debugging. A rule is made of
6691 two strings, the first specifying what needs to be rewritten in
6692 the path, and the second specifying how it should be rewritten.
6693 In @ref{set substitute-path}, we name these two parts @var{from} and
6694 @var{to} respectively. @value{GDBN} does a simple string replacement
6695 of @var{from} with @var{to} at the start of the directory part of the
6696 source file name, and uses that result instead of the original file
6697 name to look up the sources.
6699 Using the previous example, suppose the @file{foo-1.0} tree has been
6700 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6701 @value{GDBN} to replace @file{/usr/src} in all source path names with
6702 @file{/mnt/cross}. The first lookup will then be
6703 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6704 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6705 substitution rule, use the @code{set substitute-path} command
6706 (@pxref{set substitute-path}).
6708 To avoid unexpected substitution results, a rule is applied only if the
6709 @var{from} part of the directory name ends at a directory separator.
6710 For instance, a rule substituting @file{/usr/source} into
6711 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6712 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6713 is applied only at the beginning of the directory name, this rule will
6714 not be applied to @file{/root/usr/source/baz.c} either.
6716 In many cases, you can achieve the same result using the @code{directory}
6717 command. However, @code{set substitute-path} can be more efficient in
6718 the case where the sources are organized in a complex tree with multiple
6719 subdirectories. With the @code{directory} command, you need to add each
6720 subdirectory of your project. If you moved the entire tree while
6721 preserving its internal organization, then @code{set substitute-path}
6722 allows you to direct the debugger to all the sources with one single
6725 @code{set substitute-path} is also more than just a shortcut command.
6726 The source path is only used if the file at the original location no
6727 longer exists. On the other hand, @code{set substitute-path} modifies
6728 the debugger behavior to look at the rewritten location instead. So, if
6729 for any reason a source file that is not relevant to your executable is
6730 located at the original location, a substitution rule is the only
6731 method available to point @value{GDBN} at the new location.
6733 @cindex @samp{--with-relocated-sources}
6734 @cindex default source path substitution
6735 You can configure a default source path substitution rule by
6736 configuring @value{GDBN} with the
6737 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6738 should be the name of a directory under @value{GDBN}'s configured
6739 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6740 directory names in debug information under @var{dir} will be adjusted
6741 automatically if the installed @value{GDBN} is moved to a new
6742 location. This is useful if @value{GDBN}, libraries or executables
6743 with debug information and corresponding source code are being moved
6747 @item directory @var{dirname} @dots{}
6748 @item dir @var{dirname} @dots{}
6749 Add directory @var{dirname} to the front of the source path. Several
6750 directory names may be given to this command, separated by @samp{:}
6751 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6752 part of absolute file names) or
6753 whitespace. You may specify a directory that is already in the source
6754 path; this moves it forward, so @value{GDBN} searches it sooner.
6758 @vindex $cdir@r{, convenience variable}
6759 @vindex $cwd@r{, convenience variable}
6760 @cindex compilation directory
6761 @cindex current directory
6762 @cindex working directory
6763 @cindex directory, current
6764 @cindex directory, compilation
6765 You can use the string @samp{$cdir} to refer to the compilation
6766 directory (if one is recorded), and @samp{$cwd} to refer to the current
6767 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6768 tracks the current working directory as it changes during your @value{GDBN}
6769 session, while the latter is immediately expanded to the current
6770 directory at the time you add an entry to the source path.
6773 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6775 @c RET-repeat for @code{directory} is explicitly disabled, but since
6776 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6778 @item set directories @var{path-list}
6779 @kindex set directories
6780 Set the source path to @var{path-list}.
6781 @samp{$cdir:$cwd} are added if missing.
6783 @item show directories
6784 @kindex show directories
6785 Print the source path: show which directories it contains.
6787 @anchor{set substitute-path}
6788 @item set substitute-path @var{from} @var{to}
6789 @kindex set substitute-path
6790 Define a source path substitution rule, and add it at the end of the
6791 current list of existing substitution rules. If a rule with the same
6792 @var{from} was already defined, then the old rule is also deleted.
6794 For example, if the file @file{/foo/bar/baz.c} was moved to
6795 @file{/mnt/cross/baz.c}, then the command
6798 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6802 will tell @value{GDBN} to replace @samp{/usr/src} with
6803 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6804 @file{baz.c} even though it was moved.
6806 In the case when more than one substitution rule have been defined,
6807 the rules are evaluated one by one in the order where they have been
6808 defined. The first one matching, if any, is selected to perform
6811 For instance, if we had entered the following commands:
6814 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6815 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6819 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6820 @file{/mnt/include/defs.h} by using the first rule. However, it would
6821 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6822 @file{/mnt/src/lib/foo.c}.
6825 @item unset substitute-path [path]
6826 @kindex unset substitute-path
6827 If a path is specified, search the current list of substitution rules
6828 for a rule that would rewrite that path. Delete that rule if found.
6829 A warning is emitted by the debugger if no rule could be found.
6831 If no path is specified, then all substitution rules are deleted.
6833 @item show substitute-path [path]
6834 @kindex show substitute-path
6835 If a path is specified, then print the source path substitution rule
6836 which would rewrite that path, if any.
6838 If no path is specified, then print all existing source path substitution
6843 If your source path is cluttered with directories that are no longer of
6844 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6845 versions of source. You can correct the situation as follows:
6849 Use @code{directory} with no argument to reset the source path to its default value.
6852 Use @code{directory} with suitable arguments to reinstall the
6853 directories you want in the source path. You can add all the
6854 directories in one command.
6858 @section Source and Machine Code
6859 @cindex source line and its code address
6861 You can use the command @code{info line} to map source lines to program
6862 addresses (and vice versa), and the command @code{disassemble} to display
6863 a range of addresses as machine instructions. You can use the command
6864 @code{set disassemble-next-line} to set whether to disassemble next
6865 source line when execution stops. When run under @sc{gnu} Emacs
6866 mode, the @code{info line} command causes the arrow to point to the
6867 line specified. Also, @code{info line} prints addresses in symbolic form as
6872 @item info line @var{linespec}
6873 Print the starting and ending addresses of the compiled code for
6874 source line @var{linespec}. You can specify source lines in any of
6875 the ways documented in @ref{Specify Location}.
6878 For example, we can use @code{info line} to discover the location of
6879 the object code for the first line of function
6880 @code{m4_changequote}:
6882 @c FIXME: I think this example should also show the addresses in
6883 @c symbolic form, as they usually would be displayed.
6885 (@value{GDBP}) info line m4_changequote
6886 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6890 @cindex code address and its source line
6891 We can also inquire (using @code{*@var{addr}} as the form for
6892 @var{linespec}) what source line covers a particular address:
6894 (@value{GDBP}) info line *0x63ff
6895 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6898 @cindex @code{$_} and @code{info line}
6899 @cindex @code{x} command, default address
6900 @kindex x@r{(examine), and} info line
6901 After @code{info line}, the default address for the @code{x} command
6902 is changed to the starting address of the line, so that @samp{x/i} is
6903 sufficient to begin examining the machine code (@pxref{Memory,
6904 ,Examining Memory}). Also, this address is saved as the value of the
6905 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6910 @cindex assembly instructions
6911 @cindex instructions, assembly
6912 @cindex machine instructions
6913 @cindex listing machine instructions
6915 @itemx disassemble /m
6916 @itemx disassemble /r
6917 This specialized command dumps a range of memory as machine
6918 instructions. It can also print mixed source+disassembly by specifying
6919 the @code{/m} modifier and print the raw instructions in hex as well as
6920 in symbolic form by specifying the @code{/r}.
6921 The default memory range is the function surrounding the
6922 program counter of the selected frame. A single argument to this
6923 command is a program counter value; @value{GDBN} dumps the function
6924 surrounding this value. When two arguments are given, they should
6925 be separated by a comma, possibly surrounded by whitespace. The
6926 arguments specify a range of addresses to dump, in one of two forms:
6929 @item @var{start},@var{end}
6930 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6931 @item @var{start},+@var{length}
6932 the addresses from @var{start} (inclusive) to
6933 @code{@var{start}+@var{length}} (exclusive).
6937 When 2 arguments are specified, the name of the function is also
6938 printed (since there could be several functions in the given range).
6940 The argument(s) can be any expression yielding a numeric value, such as
6941 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6943 If the range of memory being disassembled contains current program counter,
6944 the instruction at that location is shown with a @code{=>} marker.
6947 The following example shows the disassembly of a range of addresses of
6948 HP PA-RISC 2.0 code:
6951 (@value{GDBP}) disas 0x32c4, 0x32e4
6952 Dump of assembler code from 0x32c4 to 0x32e4:
6953 0x32c4 <main+204>: addil 0,dp
6954 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6955 0x32cc <main+212>: ldil 0x3000,r31
6956 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6957 0x32d4 <main+220>: ldo 0(r31),rp
6958 0x32d8 <main+224>: addil -0x800,dp
6959 0x32dc <main+228>: ldo 0x588(r1),r26
6960 0x32e0 <main+232>: ldil 0x3000,r31
6961 End of assembler dump.
6964 Here is an example showing mixed source+assembly for Intel x86, when the
6965 program is stopped just after function prologue:
6968 (@value{GDBP}) disas /m main
6969 Dump of assembler code for function main:
6971 0x08048330 <+0>: push %ebp
6972 0x08048331 <+1>: mov %esp,%ebp
6973 0x08048333 <+3>: sub $0x8,%esp
6974 0x08048336 <+6>: and $0xfffffff0,%esp
6975 0x08048339 <+9>: sub $0x10,%esp
6977 6 printf ("Hello.\n");
6978 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6979 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6983 0x08048348 <+24>: mov $0x0,%eax
6984 0x0804834d <+29>: leave
6985 0x0804834e <+30>: ret
6987 End of assembler dump.
6990 Here is another example showing raw instructions in hex for AMD x86-64,
6993 (gdb) disas /r 0x400281,+10
6994 Dump of assembler code from 0x400281 to 0x40028b:
6995 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6996 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6997 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6998 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6999 End of assembler dump.
7002 Some architectures have more than one commonly-used set of instruction
7003 mnemonics or other syntax.
7005 For programs that were dynamically linked and use shared libraries,
7006 instructions that call functions or branch to locations in the shared
7007 libraries might show a seemingly bogus location---it's actually a
7008 location of the relocation table. On some architectures, @value{GDBN}
7009 might be able to resolve these to actual function names.
7012 @kindex set disassembly-flavor
7013 @cindex Intel disassembly flavor
7014 @cindex AT&T disassembly flavor
7015 @item set disassembly-flavor @var{instruction-set}
7016 Select the instruction set to use when disassembling the
7017 program via the @code{disassemble} or @code{x/i} commands.
7019 Currently this command is only defined for the Intel x86 family. You
7020 can set @var{instruction-set} to either @code{intel} or @code{att}.
7021 The default is @code{att}, the AT&T flavor used by default by Unix
7022 assemblers for x86-based targets.
7024 @kindex show disassembly-flavor
7025 @item show disassembly-flavor
7026 Show the current setting of the disassembly flavor.
7030 @kindex set disassemble-next-line
7031 @kindex show disassemble-next-line
7032 @item set disassemble-next-line
7033 @itemx show disassemble-next-line
7034 Control whether or not @value{GDBN} will disassemble the next source
7035 line or instruction when execution stops. If ON, @value{GDBN} will
7036 display disassembly of the next source line when execution of the
7037 program being debugged stops. This is @emph{in addition} to
7038 displaying the source line itself, which @value{GDBN} always does if
7039 possible. If the next source line cannot be displayed for some reason
7040 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7041 info in the debug info), @value{GDBN} will display disassembly of the
7042 next @emph{instruction} instead of showing the next source line. If
7043 AUTO, @value{GDBN} will display disassembly of next instruction only
7044 if the source line cannot be displayed. This setting causes
7045 @value{GDBN} to display some feedback when you step through a function
7046 with no line info or whose source file is unavailable. The default is
7047 OFF, which means never display the disassembly of the next line or
7053 @chapter Examining Data
7055 @cindex printing data
7056 @cindex examining data
7059 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7060 @c document because it is nonstandard... Under Epoch it displays in a
7061 @c different window or something like that.
7062 The usual way to examine data in your program is with the @code{print}
7063 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7064 evaluates and prints the value of an expression of the language your
7065 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7066 Different Languages}). It may also print the expression using a
7067 Python-based pretty-printer (@pxref{Pretty Printing}).
7070 @item print @var{expr}
7071 @itemx print /@var{f} @var{expr}
7072 @var{expr} is an expression (in the source language). By default the
7073 value of @var{expr} is printed in a format appropriate to its data type;
7074 you can choose a different format by specifying @samp{/@var{f}}, where
7075 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7079 @itemx print /@var{f}
7080 @cindex reprint the last value
7081 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7082 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7083 conveniently inspect the same value in an alternative format.
7086 A more low-level way of examining data is with the @code{x} command.
7087 It examines data in memory at a specified address and prints it in a
7088 specified format. @xref{Memory, ,Examining Memory}.
7090 If you are interested in information about types, or about how the
7091 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7092 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7096 * Expressions:: Expressions
7097 * Ambiguous Expressions:: Ambiguous Expressions
7098 * Variables:: Program variables
7099 * Arrays:: Artificial arrays
7100 * Output Formats:: Output formats
7101 * Memory:: Examining memory
7102 * Auto Display:: Automatic display
7103 * Print Settings:: Print settings
7104 * Pretty Printing:: Python pretty printing
7105 * Value History:: Value history
7106 * Convenience Vars:: Convenience variables
7107 * Registers:: Registers
7108 * Floating Point Hardware:: Floating point hardware
7109 * Vector Unit:: Vector Unit
7110 * OS Information:: Auxiliary data provided by operating system
7111 * Memory Region Attributes:: Memory region attributes
7112 * Dump/Restore Files:: Copy between memory and a file
7113 * Core File Generation:: Cause a program dump its core
7114 * Character Sets:: Debugging programs that use a different
7115 character set than GDB does
7116 * Caching Remote Data:: Data caching for remote targets
7117 * Searching Memory:: Searching memory for a sequence of bytes
7121 @section Expressions
7124 @code{print} and many other @value{GDBN} commands accept an expression and
7125 compute its value. Any kind of constant, variable or operator defined
7126 by the programming language you are using is valid in an expression in
7127 @value{GDBN}. This includes conditional expressions, function calls,
7128 casts, and string constants. It also includes preprocessor macros, if
7129 you compiled your program to include this information; see
7132 @cindex arrays in expressions
7133 @value{GDBN} supports array constants in expressions input by
7134 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7135 you can use the command @code{print @{1, 2, 3@}} to create an array
7136 of three integers. If you pass an array to a function or assign it
7137 to a program variable, @value{GDBN} copies the array to memory that
7138 is @code{malloc}ed in the target program.
7140 Because C is so widespread, most of the expressions shown in examples in
7141 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7142 Languages}, for information on how to use expressions in other
7145 In this section, we discuss operators that you can use in @value{GDBN}
7146 expressions regardless of your programming language.
7148 @cindex casts, in expressions
7149 Casts are supported in all languages, not just in C, because it is so
7150 useful to cast a number into a pointer in order to examine a structure
7151 at that address in memory.
7152 @c FIXME: casts supported---Mod2 true?
7154 @value{GDBN} supports these operators, in addition to those common
7155 to programming languages:
7159 @samp{@@} is a binary operator for treating parts of memory as arrays.
7160 @xref{Arrays, ,Artificial Arrays}, for more information.
7163 @samp{::} allows you to specify a variable in terms of the file or
7164 function where it is defined. @xref{Variables, ,Program Variables}.
7166 @cindex @{@var{type}@}
7167 @cindex type casting memory
7168 @cindex memory, viewing as typed object
7169 @cindex casts, to view memory
7170 @item @{@var{type}@} @var{addr}
7171 Refers to an object of type @var{type} stored at address @var{addr} in
7172 memory. @var{addr} may be any expression whose value is an integer or
7173 pointer (but parentheses are required around binary operators, just as in
7174 a cast). This construct is allowed regardless of what kind of data is
7175 normally supposed to reside at @var{addr}.
7178 @node Ambiguous Expressions
7179 @section Ambiguous Expressions
7180 @cindex ambiguous expressions
7182 Expressions can sometimes contain some ambiguous elements. For instance,
7183 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7184 a single function name to be defined several times, for application in
7185 different contexts. This is called @dfn{overloading}. Another example
7186 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7187 templates and is typically instantiated several times, resulting in
7188 the same function name being defined in different contexts.
7190 In some cases and depending on the language, it is possible to adjust
7191 the expression to remove the ambiguity. For instance in C@t{++}, you
7192 can specify the signature of the function you want to break on, as in
7193 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7194 qualified name of your function often makes the expression unambiguous
7197 When an ambiguity that needs to be resolved is detected, the debugger
7198 has the capability to display a menu of numbered choices for each
7199 possibility, and then waits for the selection with the prompt @samp{>}.
7200 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7201 aborts the current command. If the command in which the expression was
7202 used allows more than one choice to be selected, the next option in the
7203 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7206 For example, the following session excerpt shows an attempt to set a
7207 breakpoint at the overloaded symbol @code{String::after}.
7208 We choose three particular definitions of that function name:
7210 @c FIXME! This is likely to change to show arg type lists, at least
7213 (@value{GDBP}) b String::after
7216 [2] file:String.cc; line number:867
7217 [3] file:String.cc; line number:860
7218 [4] file:String.cc; line number:875
7219 [5] file:String.cc; line number:853
7220 [6] file:String.cc; line number:846
7221 [7] file:String.cc; line number:735
7223 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7224 Breakpoint 2 at 0xb344: file String.cc, line 875.
7225 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7226 Multiple breakpoints were set.
7227 Use the "delete" command to delete unwanted
7234 @kindex set multiple-symbols
7235 @item set multiple-symbols @var{mode}
7236 @cindex multiple-symbols menu
7238 This option allows you to adjust the debugger behavior when an expression
7241 By default, @var{mode} is set to @code{all}. If the command with which
7242 the expression is used allows more than one choice, then @value{GDBN}
7243 automatically selects all possible choices. For instance, inserting
7244 a breakpoint on a function using an ambiguous name results in a breakpoint
7245 inserted on each possible match. However, if a unique choice must be made,
7246 then @value{GDBN} uses the menu to help you disambiguate the expression.
7247 For instance, printing the address of an overloaded function will result
7248 in the use of the menu.
7250 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7251 when an ambiguity is detected.
7253 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7254 an error due to the ambiguity and the command is aborted.
7256 @kindex show multiple-symbols
7257 @item show multiple-symbols
7258 Show the current value of the @code{multiple-symbols} setting.
7262 @section Program Variables
7264 The most common kind of expression to use is the name of a variable
7267 Variables in expressions are understood in the selected stack frame
7268 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7272 global (or file-static)
7279 visible according to the scope rules of the
7280 programming language from the point of execution in that frame
7283 @noindent This means that in the function
7298 you can examine and use the variable @code{a} whenever your program is
7299 executing within the function @code{foo}, but you can only use or
7300 examine the variable @code{b} while your program is executing inside
7301 the block where @code{b} is declared.
7303 @cindex variable name conflict
7304 There is an exception: you can refer to a variable or function whose
7305 scope is a single source file even if the current execution point is not
7306 in this file. But it is possible to have more than one such variable or
7307 function with the same name (in different source files). If that
7308 happens, referring to that name has unpredictable effects. If you wish,
7309 you can specify a static variable in a particular function or file by
7310 using the colon-colon (@code{::}) notation:
7312 @cindex colon-colon, context for variables/functions
7314 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7315 @cindex @code{::}, context for variables/functions
7318 @var{file}::@var{variable}
7319 @var{function}::@var{variable}
7323 Here @var{file} or @var{function} is the name of the context for the
7324 static @var{variable}. In the case of file names, you can use quotes to
7325 make sure @value{GDBN} parses the file name as a single word---for example,
7326 to print a global value of @code{x} defined in @file{f2.c}:
7329 (@value{GDBP}) p 'f2.c'::x
7332 The @code{::} notation is normally used for referring to
7333 static variables, since you typically disambiguate uses of local variables
7334 in functions by selecting the appropriate frame and using the
7335 simple name of the variable. However, you may also use this notation
7336 to refer to local variables in frames enclosing the selected frame:
7345 process (a); /* Stop here */
7356 For example, if there is a breakpoint at the commented line,
7357 here is what you might see
7358 when the program stops after executing the call @code{bar(0)}:
7363 (@value{GDBP}) p bar::a
7366 #2 0x080483d0 in foo (a=5) at foobar.c:12
7369 (@value{GDBP}) p bar::a
7373 @cindex C@t{++} scope resolution
7374 These uses of @samp{::} are very rarely in conflict with the very similar
7375 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7376 scope resolution operator in @value{GDBN} expressions.
7377 @c FIXME: Um, so what happens in one of those rare cases where it's in
7380 @cindex wrong values
7381 @cindex variable values, wrong
7382 @cindex function entry/exit, wrong values of variables
7383 @cindex optimized code, wrong values of variables
7385 @emph{Warning:} Occasionally, a local variable may appear to have the
7386 wrong value at certain points in a function---just after entry to a new
7387 scope, and just before exit.
7389 You may see this problem when you are stepping by machine instructions.
7390 This is because, on most machines, it takes more than one instruction to
7391 set up a stack frame (including local variable definitions); if you are
7392 stepping by machine instructions, variables may appear to have the wrong
7393 values until the stack frame is completely built. On exit, it usually
7394 also takes more than one machine instruction to destroy a stack frame;
7395 after you begin stepping through that group of instructions, local
7396 variable definitions may be gone.
7398 This may also happen when the compiler does significant optimizations.
7399 To be sure of always seeing accurate values, turn off all optimization
7402 @cindex ``No symbol "foo" in current context''
7403 Another possible effect of compiler optimizations is to optimize
7404 unused variables out of existence, or assign variables to registers (as
7405 opposed to memory addresses). Depending on the support for such cases
7406 offered by the debug info format used by the compiler, @value{GDBN}
7407 might not be able to display values for such local variables. If that
7408 happens, @value{GDBN} will print a message like this:
7411 No symbol "foo" in current context.
7414 To solve such problems, either recompile without optimizations, or use a
7415 different debug info format, if the compiler supports several such
7416 formats. @xref{Compilation}, for more information on choosing compiler
7417 options. @xref{C, ,C and C@t{++}}, for more information about debug
7418 info formats that are best suited to C@t{++} programs.
7420 If you ask to print an object whose contents are unknown to
7421 @value{GDBN}, e.g., because its data type is not completely specified
7422 by the debug information, @value{GDBN} will say @samp{<incomplete
7423 type>}. @xref{Symbols, incomplete type}, for more about this.
7425 If you append @kbd{@@entry} string to a function parameter name you get its
7426 value at the time the function got called. If the value is not available an
7427 error message is printed. Entry values are available only with some compilers.
7428 Entry values are normally also printed at the function parameter list according
7429 to @ref{set print entry-values}.
7432 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7438 (gdb) print i@@entry
7442 Strings are identified as arrays of @code{char} values without specified
7443 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7444 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7445 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7446 defines literal string type @code{"char"} as @code{char} without a sign.
7451 signed char var1[] = "A";
7454 You get during debugging
7459 $2 = @{65 'A', 0 '\0'@}
7463 @section Artificial Arrays
7465 @cindex artificial array
7467 @kindex @@@r{, referencing memory as an array}
7468 It is often useful to print out several successive objects of the
7469 same type in memory; a section of an array, or an array of
7470 dynamically determined size for which only a pointer exists in the
7473 You can do this by referring to a contiguous span of memory as an
7474 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7475 operand of @samp{@@} should be the first element of the desired array
7476 and be an individual object. The right operand should be the desired length
7477 of the array. The result is an array value whose elements are all of
7478 the type of the left argument. The first element is actually the left
7479 argument; the second element comes from bytes of memory immediately
7480 following those that hold the first element, and so on. Here is an
7481 example. If a program says
7484 int *array = (int *) malloc (len * sizeof (int));
7488 you can print the contents of @code{array} with
7494 The left operand of @samp{@@} must reside in memory. Array values made
7495 with @samp{@@} in this way behave just like other arrays in terms of
7496 subscripting, and are coerced to pointers when used in expressions.
7497 Artificial arrays most often appear in expressions via the value history
7498 (@pxref{Value History, ,Value History}), after printing one out.
7500 Another way to create an artificial array is to use a cast.
7501 This re-interprets a value as if it were an array.
7502 The value need not be in memory:
7504 (@value{GDBP}) p/x (short[2])0x12345678
7505 $1 = @{0x1234, 0x5678@}
7508 As a convenience, if you leave the array length out (as in
7509 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7510 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7512 (@value{GDBP}) p/x (short[])0x12345678
7513 $2 = @{0x1234, 0x5678@}
7516 Sometimes the artificial array mechanism is not quite enough; in
7517 moderately complex data structures, the elements of interest may not
7518 actually be adjacent---for example, if you are interested in the values
7519 of pointers in an array. One useful work-around in this situation is
7520 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7521 Variables}) as a counter in an expression that prints the first
7522 interesting value, and then repeat that expression via @key{RET}. For
7523 instance, suppose you have an array @code{dtab} of pointers to
7524 structures, and you are interested in the values of a field @code{fv}
7525 in each structure. Here is an example of what you might type:
7535 @node Output Formats
7536 @section Output Formats
7538 @cindex formatted output
7539 @cindex output formats
7540 By default, @value{GDBN} prints a value according to its data type. Sometimes
7541 this is not what you want. For example, you might want to print a number
7542 in hex, or a pointer in decimal. Or you might want to view data in memory
7543 at a certain address as a character string or as an instruction. To do
7544 these things, specify an @dfn{output format} when you print a value.
7546 The simplest use of output formats is to say how to print a value
7547 already computed. This is done by starting the arguments of the
7548 @code{print} command with a slash and a format letter. The format
7549 letters supported are:
7553 Regard the bits of the value as an integer, and print the integer in
7557 Print as integer in signed decimal.
7560 Print as integer in unsigned decimal.
7563 Print as integer in octal.
7566 Print as integer in binary. The letter @samp{t} stands for ``two''.
7567 @footnote{@samp{b} cannot be used because these format letters are also
7568 used with the @code{x} command, where @samp{b} stands for ``byte'';
7569 see @ref{Memory,,Examining Memory}.}
7572 @cindex unknown address, locating
7573 @cindex locate address
7574 Print as an address, both absolute in hexadecimal and as an offset from
7575 the nearest preceding symbol. You can use this format used to discover
7576 where (in what function) an unknown address is located:
7579 (@value{GDBP}) p/a 0x54320
7580 $3 = 0x54320 <_initialize_vx+396>
7584 The command @code{info symbol 0x54320} yields similar results.
7585 @xref{Symbols, info symbol}.
7588 Regard as an integer and print it as a character constant. This
7589 prints both the numerical value and its character representation. The
7590 character representation is replaced with the octal escape @samp{\nnn}
7591 for characters outside the 7-bit @sc{ascii} range.
7593 Without this format, @value{GDBN} displays @code{char},
7594 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7595 constants. Single-byte members of vectors are displayed as integer
7599 Regard the bits of the value as a floating point number and print
7600 using typical floating point syntax.
7603 @cindex printing strings
7604 @cindex printing byte arrays
7605 Regard as a string, if possible. With this format, pointers to single-byte
7606 data are displayed as null-terminated strings and arrays of single-byte data
7607 are displayed as fixed-length strings. Other values are displayed in their
7610 Without this format, @value{GDBN} displays pointers to and arrays of
7611 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7612 strings. Single-byte members of a vector are displayed as an integer
7616 @cindex raw printing
7617 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7618 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7619 Printing}). This typically results in a higher-level display of the
7620 value's contents. The @samp{r} format bypasses any Python
7621 pretty-printer which might exist.
7624 For example, to print the program counter in hex (@pxref{Registers}), type
7631 Note that no space is required before the slash; this is because command
7632 names in @value{GDBN} cannot contain a slash.
7634 To reprint the last value in the value history with a different format,
7635 you can use the @code{print} command with just a format and no
7636 expression. For example, @samp{p/x} reprints the last value in hex.
7639 @section Examining Memory
7641 You can use the command @code{x} (for ``examine'') to examine memory in
7642 any of several formats, independently of your program's data types.
7644 @cindex examining memory
7646 @kindex x @r{(examine memory)}
7647 @item x/@var{nfu} @var{addr}
7650 Use the @code{x} command to examine memory.
7653 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7654 much memory to display and how to format it; @var{addr} is an
7655 expression giving the address where you want to start displaying memory.
7656 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7657 Several commands set convenient defaults for @var{addr}.
7660 @item @var{n}, the repeat count
7661 The repeat count is a decimal integer; the default is 1. It specifies
7662 how much memory (counting by units @var{u}) to display.
7663 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7666 @item @var{f}, the display format
7667 The display format is one of the formats used by @code{print}
7668 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7669 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7670 The default is @samp{x} (hexadecimal) initially. The default changes
7671 each time you use either @code{x} or @code{print}.
7673 @item @var{u}, the unit size
7674 The unit size is any of
7680 Halfwords (two bytes).
7682 Words (four bytes). This is the initial default.
7684 Giant words (eight bytes).
7687 Each time you specify a unit size with @code{x}, that size becomes the
7688 default unit the next time you use @code{x}. For the @samp{i} format,
7689 the unit size is ignored and is normally not written. For the @samp{s} format,
7690 the unit size defaults to @samp{b}, unless it is explicitly given.
7691 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7692 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7693 Note that the results depend on the programming language of the
7694 current compilation unit. If the language is C, the @samp{s}
7695 modifier will use the UTF-16 encoding while @samp{w} will use
7696 UTF-32. The encoding is set by the programming language and cannot
7699 @item @var{addr}, starting display address
7700 @var{addr} is the address where you want @value{GDBN} to begin displaying
7701 memory. The expression need not have a pointer value (though it may);
7702 it is always interpreted as an integer address of a byte of memory.
7703 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7704 @var{addr} is usually just after the last address examined---but several
7705 other commands also set the default address: @code{info breakpoints} (to
7706 the address of the last breakpoint listed), @code{info line} (to the
7707 starting address of a line), and @code{print} (if you use it to display
7708 a value from memory).
7711 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7712 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7713 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7714 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7715 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7717 Since the letters indicating unit sizes are all distinct from the
7718 letters specifying output formats, you do not have to remember whether
7719 unit size or format comes first; either order works. The output
7720 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7721 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7723 Even though the unit size @var{u} is ignored for the formats @samp{s}
7724 and @samp{i}, you might still want to use a count @var{n}; for example,
7725 @samp{3i} specifies that you want to see three machine instructions,
7726 including any operands. For convenience, especially when used with
7727 the @code{display} command, the @samp{i} format also prints branch delay
7728 slot instructions, if any, beyond the count specified, which immediately
7729 follow the last instruction that is within the count. The command
7730 @code{disassemble} gives an alternative way of inspecting machine
7731 instructions; see @ref{Machine Code,,Source and Machine Code}.
7733 All the defaults for the arguments to @code{x} are designed to make it
7734 easy to continue scanning memory with minimal specifications each time
7735 you use @code{x}. For example, after you have inspected three machine
7736 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7737 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7738 the repeat count @var{n} is used again; the other arguments default as
7739 for successive uses of @code{x}.
7741 When examining machine instructions, the instruction at current program
7742 counter is shown with a @code{=>} marker. For example:
7745 (@value{GDBP}) x/5i $pc-6
7746 0x804837f <main+11>: mov %esp,%ebp
7747 0x8048381 <main+13>: push %ecx
7748 0x8048382 <main+14>: sub $0x4,%esp
7749 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7750 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7753 @cindex @code{$_}, @code{$__}, and value history
7754 The addresses and contents printed by the @code{x} command are not saved
7755 in the value history because there is often too much of them and they
7756 would get in the way. Instead, @value{GDBN} makes these values available for
7757 subsequent use in expressions as values of the convenience variables
7758 @code{$_} and @code{$__}. After an @code{x} command, the last address
7759 examined is available for use in expressions in the convenience variable
7760 @code{$_}. The contents of that address, as examined, are available in
7761 the convenience variable @code{$__}.
7763 If the @code{x} command has a repeat count, the address and contents saved
7764 are from the last memory unit printed; this is not the same as the last
7765 address printed if several units were printed on the last line of output.
7767 @cindex remote memory comparison
7768 @cindex verify remote memory image
7769 When you are debugging a program running on a remote target machine
7770 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7771 remote machine's memory against the executable file you downloaded to
7772 the target. The @code{compare-sections} command is provided for such
7776 @kindex compare-sections
7777 @item compare-sections @r{[}@var{section-name}@r{]}
7778 Compare the data of a loadable section @var{section-name} in the
7779 executable file of the program being debugged with the same section in
7780 the remote machine's memory, and report any mismatches. With no
7781 arguments, compares all loadable sections. This command's
7782 availability depends on the target's support for the @code{"qCRC"}
7787 @section Automatic Display
7788 @cindex automatic display
7789 @cindex display of expressions
7791 If you find that you want to print the value of an expression frequently
7792 (to see how it changes), you might want to add it to the @dfn{automatic
7793 display list} so that @value{GDBN} prints its value each time your program stops.
7794 Each expression added to the list is given a number to identify it;
7795 to remove an expression from the list, you specify that number.
7796 The automatic display looks like this:
7800 3: bar[5] = (struct hack *) 0x3804
7804 This display shows item numbers, expressions and their current values. As with
7805 displays you request manually using @code{x} or @code{print}, you can
7806 specify the output format you prefer; in fact, @code{display} decides
7807 whether to use @code{print} or @code{x} depending your format
7808 specification---it uses @code{x} if you specify either the @samp{i}
7809 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7813 @item display @var{expr}
7814 Add the expression @var{expr} to the list of expressions to display
7815 each time your program stops. @xref{Expressions, ,Expressions}.
7817 @code{display} does not repeat if you press @key{RET} again after using it.
7819 @item display/@var{fmt} @var{expr}
7820 For @var{fmt} specifying only a display format and not a size or
7821 count, add the expression @var{expr} to the auto-display list but
7822 arrange to display it each time in the specified format @var{fmt}.
7823 @xref{Output Formats,,Output Formats}.
7825 @item display/@var{fmt} @var{addr}
7826 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7827 number of units, add the expression @var{addr} as a memory address to
7828 be examined each time your program stops. Examining means in effect
7829 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7832 For example, @samp{display/i $pc} can be helpful, to see the machine
7833 instruction about to be executed each time execution stops (@samp{$pc}
7834 is a common name for the program counter; @pxref{Registers, ,Registers}).
7837 @kindex delete display
7839 @item undisplay @var{dnums}@dots{}
7840 @itemx delete display @var{dnums}@dots{}
7841 Remove items from the list of expressions to display. Specify the
7842 numbers of the displays that you want affected with the command
7843 argument @var{dnums}. It can be a single display number, one of the
7844 numbers shown in the first field of the @samp{info display} display;
7845 or it could be a range of display numbers, as in @code{2-4}.
7847 @code{undisplay} does not repeat if you press @key{RET} after using it.
7848 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7850 @kindex disable display
7851 @item disable display @var{dnums}@dots{}
7852 Disable the display of item numbers @var{dnums}. A disabled display
7853 item is not printed automatically, but is not forgotten. It may be
7854 enabled again later. Specify the numbers of the displays that you
7855 want affected with the command argument @var{dnums}. It can be a
7856 single display number, one of the numbers shown in the first field of
7857 the @samp{info display} display; or it could be a range of display
7858 numbers, as in @code{2-4}.
7860 @kindex enable display
7861 @item enable display @var{dnums}@dots{}
7862 Enable display of item numbers @var{dnums}. It becomes effective once
7863 again in auto display of its expression, until you specify otherwise.
7864 Specify the numbers of the displays that you want affected with the
7865 command argument @var{dnums}. It can be a single display number, one
7866 of the numbers shown in the first field of the @samp{info display}
7867 display; or it could be a range of display numbers, as in @code{2-4}.
7870 Display the current values of the expressions on the list, just as is
7871 done when your program stops.
7873 @kindex info display
7875 Print the list of expressions previously set up to display
7876 automatically, each one with its item number, but without showing the
7877 values. This includes disabled expressions, which are marked as such.
7878 It also includes expressions which would not be displayed right now
7879 because they refer to automatic variables not currently available.
7882 @cindex display disabled out of scope
7883 If a display expression refers to local variables, then it does not make
7884 sense outside the lexical context for which it was set up. Such an
7885 expression is disabled when execution enters a context where one of its
7886 variables is not defined. For example, if you give the command
7887 @code{display last_char} while inside a function with an argument
7888 @code{last_char}, @value{GDBN} displays this argument while your program
7889 continues to stop inside that function. When it stops elsewhere---where
7890 there is no variable @code{last_char}---the display is disabled
7891 automatically. The next time your program stops where @code{last_char}
7892 is meaningful, you can enable the display expression once again.
7894 @node Print Settings
7895 @section Print Settings
7897 @cindex format options
7898 @cindex print settings
7899 @value{GDBN} provides the following ways to control how arrays, structures,
7900 and symbols are printed.
7903 These settings are useful for debugging programs in any language:
7907 @item set print address
7908 @itemx set print address on
7909 @cindex print/don't print memory addresses
7910 @value{GDBN} prints memory addresses showing the location of stack
7911 traces, structure values, pointer values, breakpoints, and so forth,
7912 even when it also displays the contents of those addresses. The default
7913 is @code{on}. For example, this is what a stack frame display looks like with
7914 @code{set print address on}:
7919 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7921 530 if (lquote != def_lquote)
7925 @item set print address off
7926 Do not print addresses when displaying their contents. For example,
7927 this is the same stack frame displayed with @code{set print address off}:
7931 (@value{GDBP}) set print addr off
7933 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7934 530 if (lquote != def_lquote)
7938 You can use @samp{set print address off} to eliminate all machine
7939 dependent displays from the @value{GDBN} interface. For example, with
7940 @code{print address off}, you should get the same text for backtraces on
7941 all machines---whether or not they involve pointer arguments.
7944 @item show print address
7945 Show whether or not addresses are to be printed.
7948 When @value{GDBN} prints a symbolic address, it normally prints the
7949 closest earlier symbol plus an offset. If that symbol does not uniquely
7950 identify the address (for example, it is a name whose scope is a single
7951 source file), you may need to clarify. One way to do this is with
7952 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7953 you can set @value{GDBN} to print the source file and line number when
7954 it prints a symbolic address:
7957 @item set print symbol-filename on
7958 @cindex source file and line of a symbol
7959 @cindex symbol, source file and line
7960 Tell @value{GDBN} to print the source file name and line number of a
7961 symbol in the symbolic form of an address.
7963 @item set print symbol-filename off
7964 Do not print source file name and line number of a symbol. This is the
7967 @item show print symbol-filename
7968 Show whether or not @value{GDBN} will print the source file name and
7969 line number of a symbol in the symbolic form of an address.
7972 Another situation where it is helpful to show symbol filenames and line
7973 numbers is when disassembling code; @value{GDBN} shows you the line
7974 number and source file that corresponds to each instruction.
7976 Also, you may wish to see the symbolic form only if the address being
7977 printed is reasonably close to the closest earlier symbol:
7980 @item set print max-symbolic-offset @var{max-offset}
7981 @cindex maximum value for offset of closest symbol
7982 Tell @value{GDBN} to only display the symbolic form of an address if the
7983 offset between the closest earlier symbol and the address is less than
7984 @var{max-offset}. The default is 0, which tells @value{GDBN}
7985 to always print the symbolic form of an address if any symbol precedes it.
7987 @item show print max-symbolic-offset
7988 Ask how large the maximum offset is that @value{GDBN} prints in a
7992 @cindex wild pointer, interpreting
7993 @cindex pointer, finding referent
7994 If you have a pointer and you are not sure where it points, try
7995 @samp{set print symbol-filename on}. Then you can determine the name
7996 and source file location of the variable where it points, using
7997 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7998 For example, here @value{GDBN} shows that a variable @code{ptt} points
7999 at another variable @code{t}, defined in @file{hi2.c}:
8002 (@value{GDBP}) set print symbol-filename on
8003 (@value{GDBP}) p/a ptt
8004 $4 = 0xe008 <t in hi2.c>
8008 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8009 does not show the symbol name and filename of the referent, even with
8010 the appropriate @code{set print} options turned on.
8013 Other settings control how different kinds of objects are printed:
8016 @item set print array
8017 @itemx set print array on
8018 @cindex pretty print arrays
8019 Pretty print arrays. This format is more convenient to read,
8020 but uses more space. The default is off.
8022 @item set print array off
8023 Return to compressed format for arrays.
8025 @item show print array
8026 Show whether compressed or pretty format is selected for displaying
8029 @cindex print array indexes
8030 @item set print array-indexes
8031 @itemx set print array-indexes on
8032 Print the index of each element when displaying arrays. May be more
8033 convenient to locate a given element in the array or quickly find the
8034 index of a given element in that printed array. The default is off.
8036 @item set print array-indexes off
8037 Stop printing element indexes when displaying arrays.
8039 @item show print array-indexes
8040 Show whether the index of each element is printed when displaying
8043 @item set print elements @var{number-of-elements}
8044 @cindex number of array elements to print
8045 @cindex limit on number of printed array elements
8046 Set a limit on how many elements of an array @value{GDBN} will print.
8047 If @value{GDBN} is printing a large array, it stops printing after it has
8048 printed the number of elements set by the @code{set print elements} command.
8049 This limit also applies to the display of strings.
8050 When @value{GDBN} starts, this limit is set to 200.
8051 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8053 @item show print elements
8054 Display the number of elements of a large array that @value{GDBN} will print.
8055 If the number is 0, then the printing is unlimited.
8057 @item set print frame-arguments @var{value}
8058 @kindex set print frame-arguments
8059 @cindex printing frame argument values
8060 @cindex print all frame argument values
8061 @cindex print frame argument values for scalars only
8062 @cindex do not print frame argument values
8063 This command allows to control how the values of arguments are printed
8064 when the debugger prints a frame (@pxref{Frames}). The possible
8069 The values of all arguments are printed.
8072 Print the value of an argument only if it is a scalar. The value of more
8073 complex arguments such as arrays, structures, unions, etc, is replaced
8074 by @code{@dots{}}. This is the default. Here is an example where
8075 only scalar arguments are shown:
8078 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8083 None of the argument values are printed. Instead, the value of each argument
8084 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8087 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8092 By default, only scalar arguments are printed. This command can be used
8093 to configure the debugger to print the value of all arguments, regardless
8094 of their type. However, it is often advantageous to not print the value
8095 of more complex parameters. For instance, it reduces the amount of
8096 information printed in each frame, making the backtrace more readable.
8097 Also, it improves performance when displaying Ada frames, because
8098 the computation of large arguments can sometimes be CPU-intensive,
8099 especially in large applications. Setting @code{print frame-arguments}
8100 to @code{scalars} (the default) or @code{none} avoids this computation,
8101 thus speeding up the display of each Ada frame.
8103 @item show print frame-arguments
8104 Show how the value of arguments should be displayed when printing a frame.
8106 @anchor{set print entry-values}
8107 @item set print entry-values @var{value}
8108 @kindex set print entry-values
8109 Set printing of frame argument values at function entry. In some cases
8110 @value{GDBN} can determine the value of function argument which was passed by
8111 the function caller, even if the value was modified inside the called function
8112 and therefore is different. With optimized code, the current value could be
8113 unavailable, but the entry value may still be known.
8115 The default value is @code{default} (see below for its description). Older
8116 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8117 this feature will behave in the @code{default} setting the same way as with the
8120 This functionality is currently supported only by DWARF 2 debugging format and
8121 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8122 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8125 The @var{value} parameter can be one of the following:
8129 Print only actual parameter values, never print values from function entry
8133 #0 different (val=6)
8134 #0 lost (val=<optimized out>)
8136 #0 invalid (val=<optimized out>)
8140 Print only parameter values from function entry point. The actual parameter
8141 values are never printed.
8143 #0 equal (val@@entry=5)
8144 #0 different (val@@entry=5)
8145 #0 lost (val@@entry=5)
8146 #0 born (val@@entry=<optimized out>)
8147 #0 invalid (val@@entry=<optimized out>)
8151 Print only parameter values from function entry point. If value from function
8152 entry point is not known while the actual value is known, print the actual
8153 value for such parameter.
8155 #0 equal (val@@entry=5)
8156 #0 different (val@@entry=5)
8157 #0 lost (val@@entry=5)
8159 #0 invalid (val@@entry=<optimized out>)
8163 Print actual parameter values. If actual parameter value is not known while
8164 value from function entry point is known, print the entry point value for such
8168 #0 different (val=6)
8169 #0 lost (val@@entry=5)
8171 #0 invalid (val=<optimized out>)
8175 Always print both the actual parameter value and its value from function entry
8176 point, even if values of one or both are not available due to compiler
8179 #0 equal (val=5, val@@entry=5)
8180 #0 different (val=6, val@@entry=5)
8181 #0 lost (val=<optimized out>, val@@entry=5)
8182 #0 born (val=10, val@@entry=<optimized out>)
8183 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8187 Print the actual parameter value if it is known and also its value from
8188 function entry point if it is known. If neither is known, print for the actual
8189 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8190 values are known and identical, print the shortened
8191 @code{param=param@@entry=VALUE} notation.
8193 #0 equal (val=val@@entry=5)
8194 #0 different (val=6, val@@entry=5)
8195 #0 lost (val@@entry=5)
8197 #0 invalid (val=<optimized out>)
8201 Always print the actual parameter value. Print also its value from function
8202 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8203 if both values are known and identical, print the shortened
8204 @code{param=param@@entry=VALUE} notation.
8206 #0 equal (val=val@@entry=5)
8207 #0 different (val=6, val@@entry=5)
8208 #0 lost (val=<optimized out>, val@@entry=5)
8210 #0 invalid (val=<optimized out>)
8214 For analysis messages on possible failures of frame argument values at function
8215 entry resolution see @ref{set debug entry-values}.
8217 @item show print entry-values
8218 Show the method being used for printing of frame argument values at function
8221 @item set print repeats
8222 @cindex repeated array elements
8223 Set the threshold for suppressing display of repeated array
8224 elements. When the number of consecutive identical elements of an
8225 array exceeds the threshold, @value{GDBN} prints the string
8226 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8227 identical repetitions, instead of displaying the identical elements
8228 themselves. Setting the threshold to zero will cause all elements to
8229 be individually printed. The default threshold is 10.
8231 @item show print repeats
8232 Display the current threshold for printing repeated identical
8235 @item set print null-stop
8236 @cindex @sc{null} elements in arrays
8237 Cause @value{GDBN} to stop printing the characters of an array when the first
8238 @sc{null} is encountered. This is useful when large arrays actually
8239 contain only short strings.
8242 @item show print null-stop
8243 Show whether @value{GDBN} stops printing an array on the first
8244 @sc{null} character.
8246 @item set print pretty on
8247 @cindex print structures in indented form
8248 @cindex indentation in structure display
8249 Cause @value{GDBN} to print structures in an indented format with one member
8250 per line, like this:
8265 @item set print pretty off
8266 Cause @value{GDBN} to print structures in a compact format, like this:
8270 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8271 meat = 0x54 "Pork"@}
8276 This is the default format.
8278 @item show print pretty
8279 Show which format @value{GDBN} is using to print structures.
8281 @item set print sevenbit-strings on
8282 @cindex eight-bit characters in strings
8283 @cindex octal escapes in strings
8284 Print using only seven-bit characters; if this option is set,
8285 @value{GDBN} displays any eight-bit characters (in strings or
8286 character values) using the notation @code{\}@var{nnn}. This setting is
8287 best if you are working in English (@sc{ascii}) and you use the
8288 high-order bit of characters as a marker or ``meta'' bit.
8290 @item set print sevenbit-strings off
8291 Print full eight-bit characters. This allows the use of more
8292 international character sets, and is the default.
8294 @item show print sevenbit-strings
8295 Show whether or not @value{GDBN} is printing only seven-bit characters.
8297 @item set print union on
8298 @cindex unions in structures, printing
8299 Tell @value{GDBN} to print unions which are contained in structures
8300 and other unions. This is the default setting.
8302 @item set print union off
8303 Tell @value{GDBN} not to print unions which are contained in
8304 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8307 @item show print union
8308 Ask @value{GDBN} whether or not it will print unions which are contained in
8309 structures and other unions.
8311 For example, given the declarations
8314 typedef enum @{Tree, Bug@} Species;
8315 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8316 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8327 struct thing foo = @{Tree, @{Acorn@}@};
8331 with @code{set print union on} in effect @samp{p foo} would print
8334 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8338 and with @code{set print union off} in effect it would print
8341 $1 = @{it = Tree, form = @{...@}@}
8345 @code{set print union} affects programs written in C-like languages
8351 These settings are of interest when debugging C@t{++} programs:
8354 @cindex demangling C@t{++} names
8355 @item set print demangle
8356 @itemx set print demangle on
8357 Print C@t{++} names in their source form rather than in the encoded
8358 (``mangled'') form passed to the assembler and linker for type-safe
8359 linkage. The default is on.
8361 @item show print demangle
8362 Show whether C@t{++} names are printed in mangled or demangled form.
8364 @item set print asm-demangle
8365 @itemx set print asm-demangle on
8366 Print C@t{++} names in their source form rather than their mangled form, even
8367 in assembler code printouts such as instruction disassemblies.
8370 @item show print asm-demangle
8371 Show whether C@t{++} names in assembly listings are printed in mangled
8374 @cindex C@t{++} symbol decoding style
8375 @cindex symbol decoding style, C@t{++}
8376 @kindex set demangle-style
8377 @item set demangle-style @var{style}
8378 Choose among several encoding schemes used by different compilers to
8379 represent C@t{++} names. The choices for @var{style} are currently:
8383 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8386 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8387 This is the default.
8390 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8393 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8396 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8397 @strong{Warning:} this setting alone is not sufficient to allow
8398 debugging @code{cfront}-generated executables. @value{GDBN} would
8399 require further enhancement to permit that.
8402 If you omit @var{style}, you will see a list of possible formats.
8404 @item show demangle-style
8405 Display the encoding style currently in use for decoding C@t{++} symbols.
8407 @item set print object
8408 @itemx set print object on
8409 @cindex derived type of an object, printing
8410 @cindex display derived types
8411 When displaying a pointer to an object, identify the @emph{actual}
8412 (derived) type of the object rather than the @emph{declared} type, using
8413 the virtual function table. Note that the virtual function table is
8414 required---this feature can only work for objects that have run-time
8415 type identification; a single virtual method in the object's declared
8418 @item set print object off
8419 Display only the declared type of objects, without reference to the
8420 virtual function table. This is the default setting.
8422 @item show print object
8423 Show whether actual, or declared, object types are displayed.
8425 @item set print static-members
8426 @itemx set print static-members on
8427 @cindex static members of C@t{++} objects
8428 Print static members when displaying a C@t{++} object. The default is on.
8430 @item set print static-members off
8431 Do not print static members when displaying a C@t{++} object.
8433 @item show print static-members
8434 Show whether C@t{++} static members are printed or not.
8436 @item set print pascal_static-members
8437 @itemx set print pascal_static-members on
8438 @cindex static members of Pascal objects
8439 @cindex Pascal objects, static members display
8440 Print static members when displaying a Pascal object. The default is on.
8442 @item set print pascal_static-members off
8443 Do not print static members when displaying a Pascal object.
8445 @item show print pascal_static-members
8446 Show whether Pascal static members are printed or not.
8448 @c These don't work with HP ANSI C++ yet.
8449 @item set print vtbl
8450 @itemx set print vtbl on
8451 @cindex pretty print C@t{++} virtual function tables
8452 @cindex virtual functions (C@t{++}) display
8453 @cindex VTBL display
8454 Pretty print C@t{++} virtual function tables. The default is off.
8455 (The @code{vtbl} commands do not work on programs compiled with the HP
8456 ANSI C@t{++} compiler (@code{aCC}).)
8458 @item set print vtbl off
8459 Do not pretty print C@t{++} virtual function tables.
8461 @item show print vtbl
8462 Show whether C@t{++} virtual function tables are pretty printed, or not.
8465 @node Pretty Printing
8466 @section Pretty Printing
8468 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8469 Python code. It greatly simplifies the display of complex objects. This
8470 mechanism works for both MI and the CLI.
8473 * Pretty-Printer Introduction:: Introduction to pretty-printers
8474 * Pretty-Printer Example:: An example pretty-printer
8475 * Pretty-Printer Commands:: Pretty-printer commands
8478 @node Pretty-Printer Introduction
8479 @subsection Pretty-Printer Introduction
8481 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8482 registered for the value. If there is then @value{GDBN} invokes the
8483 pretty-printer to print the value. Otherwise the value is printed normally.
8485 Pretty-printers are normally named. This makes them easy to manage.
8486 The @samp{info pretty-printer} command will list all the installed
8487 pretty-printers with their names.
8488 If a pretty-printer can handle multiple data types, then its
8489 @dfn{subprinters} are the printers for the individual data types.
8490 Each such subprinter has its own name.
8491 The format of the name is @var{printer-name};@var{subprinter-name}.
8493 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8494 Typically they are automatically loaded and registered when the corresponding
8495 debug information is loaded, thus making them available without having to
8496 do anything special.
8498 There are three places where a pretty-printer can be registered.
8502 Pretty-printers registered globally are available when debugging
8506 Pretty-printers registered with a program space are available only
8507 when debugging that program.
8508 @xref{Progspaces In Python}, for more details on program spaces in Python.
8511 Pretty-printers registered with an objfile are loaded and unloaded
8512 with the corresponding objfile (e.g., shared library).
8513 @xref{Objfiles In Python}, for more details on objfiles in Python.
8516 @xref{Selecting Pretty-Printers}, for further information on how
8517 pretty-printers are selected,
8519 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8522 @node Pretty-Printer Example
8523 @subsection Pretty-Printer Example
8525 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8528 (@value{GDBP}) print s
8530 static npos = 4294967295,
8532 <std::allocator<char>> = @{
8533 <__gnu_cxx::new_allocator<char>> = @{
8534 <No data fields>@}, <No data fields>
8536 members of std::basic_string<char, std::char_traits<char>,
8537 std::allocator<char> >::_Alloc_hider:
8538 _M_p = 0x804a014 "abcd"
8543 With a pretty-printer for @code{std::string} only the contents are printed:
8546 (@value{GDBP}) print s
8550 @node Pretty-Printer Commands
8551 @subsection Pretty-Printer Commands
8552 @cindex pretty-printer commands
8555 @kindex info pretty-printer
8556 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8557 Print the list of installed pretty-printers.
8558 This includes disabled pretty-printers, which are marked as such.
8560 @var{object-regexp} is a regular expression matching the objects
8561 whose pretty-printers to list.
8562 Objects can be @code{global}, the program space's file
8563 (@pxref{Progspaces In Python}),
8564 and the object files within that program space (@pxref{Objfiles In Python}).
8565 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8566 looks up a printer from these three objects.
8568 @var{name-regexp} is a regular expression matching the name of the printers
8571 @kindex disable pretty-printer
8572 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8573 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8574 A disabled pretty-printer is not forgotten, it may be enabled again later.
8576 @kindex enable pretty-printer
8577 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8578 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8583 Suppose we have three pretty-printers installed: one from library1.so
8584 named @code{foo} that prints objects of type @code{foo}, and
8585 another from library2.so named @code{bar} that prints two types of objects,
8586 @code{bar1} and @code{bar2}.
8589 (gdb) info pretty-printer
8596 (gdb) info pretty-printer library2
8601 (gdb) disable pretty-printer library1
8603 2 of 3 printers enabled
8604 (gdb) info pretty-printer
8611 (gdb) disable pretty-printer library2 bar:bar1
8613 1 of 3 printers enabled
8614 (gdb) info pretty-printer library2
8621 (gdb) disable pretty-printer library2 bar
8623 0 of 3 printers enabled
8624 (gdb) info pretty-printer library2
8633 Note that for @code{bar} the entire printer can be disabled,
8634 as can each individual subprinter.
8637 @section Value History
8639 @cindex value history
8640 @cindex history of values printed by @value{GDBN}
8641 Values printed by the @code{print} command are saved in the @value{GDBN}
8642 @dfn{value history}. This allows you to refer to them in other expressions.
8643 Values are kept until the symbol table is re-read or discarded
8644 (for example with the @code{file} or @code{symbol-file} commands).
8645 When the symbol table changes, the value history is discarded,
8646 since the values may contain pointers back to the types defined in the
8651 @cindex history number
8652 The values printed are given @dfn{history numbers} by which you can
8653 refer to them. These are successive integers starting with one.
8654 @code{print} shows you the history number assigned to a value by
8655 printing @samp{$@var{num} = } before the value; here @var{num} is the
8658 To refer to any previous value, use @samp{$} followed by the value's
8659 history number. The way @code{print} labels its output is designed to
8660 remind you of this. Just @code{$} refers to the most recent value in
8661 the history, and @code{$$} refers to the value before that.
8662 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8663 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8664 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8666 For example, suppose you have just printed a pointer to a structure and
8667 want to see the contents of the structure. It suffices to type
8673 If you have a chain of structures where the component @code{next} points
8674 to the next one, you can print the contents of the next one with this:
8681 You can print successive links in the chain by repeating this
8682 command---which you can do by just typing @key{RET}.
8684 Note that the history records values, not expressions. If the value of
8685 @code{x} is 4 and you type these commands:
8693 then the value recorded in the value history by the @code{print} command
8694 remains 4 even though the value of @code{x} has changed.
8699 Print the last ten values in the value history, with their item numbers.
8700 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8701 values} does not change the history.
8703 @item show values @var{n}
8704 Print ten history values centered on history item number @var{n}.
8707 Print ten history values just after the values last printed. If no more
8708 values are available, @code{show values +} produces no display.
8711 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8712 same effect as @samp{show values +}.
8714 @node Convenience Vars
8715 @section Convenience Variables
8717 @cindex convenience variables
8718 @cindex user-defined variables
8719 @value{GDBN} provides @dfn{convenience variables} that you can use within
8720 @value{GDBN} to hold on to a value and refer to it later. These variables
8721 exist entirely within @value{GDBN}; they are not part of your program, and
8722 setting a convenience variable has no direct effect on further execution
8723 of your program. That is why you can use them freely.
8725 Convenience variables are prefixed with @samp{$}. Any name preceded by
8726 @samp{$} can be used for a convenience variable, unless it is one of
8727 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8728 (Value history references, in contrast, are @emph{numbers} preceded
8729 by @samp{$}. @xref{Value History, ,Value History}.)
8731 You can save a value in a convenience variable with an assignment
8732 expression, just as you would set a variable in your program.
8736 set $foo = *object_ptr
8740 would save in @code{$foo} the value contained in the object pointed to by
8743 Using a convenience variable for the first time creates it, but its
8744 value is @code{void} until you assign a new value. You can alter the
8745 value with another assignment at any time.
8747 Convenience variables have no fixed types. You can assign a convenience
8748 variable any type of value, including structures and arrays, even if
8749 that variable already has a value of a different type. The convenience
8750 variable, when used as an expression, has the type of its current value.
8753 @kindex show convenience
8754 @cindex show all user variables
8755 @item show convenience
8756 Print a list of convenience variables used so far, and their values.
8757 Abbreviated @code{show conv}.
8759 @kindex init-if-undefined
8760 @cindex convenience variables, initializing
8761 @item init-if-undefined $@var{variable} = @var{expression}
8762 Set a convenience variable if it has not already been set. This is useful
8763 for user-defined commands that keep some state. It is similar, in concept,
8764 to using local static variables with initializers in C (except that
8765 convenience variables are global). It can also be used to allow users to
8766 override default values used in a command script.
8768 If the variable is already defined then the expression is not evaluated so
8769 any side-effects do not occur.
8772 One of the ways to use a convenience variable is as a counter to be
8773 incremented or a pointer to be advanced. For example, to print
8774 a field from successive elements of an array of structures:
8778 print bar[$i++]->contents
8782 Repeat that command by typing @key{RET}.
8784 Some convenience variables are created automatically by @value{GDBN} and given
8785 values likely to be useful.
8788 @vindex $_@r{, convenience variable}
8790 The variable @code{$_} is automatically set by the @code{x} command to
8791 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8792 commands which provide a default address for @code{x} to examine also
8793 set @code{$_} to that address; these commands include @code{info line}
8794 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8795 except when set by the @code{x} command, in which case it is a pointer
8796 to the type of @code{$__}.
8798 @vindex $__@r{, convenience variable}
8800 The variable @code{$__} is automatically set by the @code{x} command
8801 to the value found in the last address examined. Its type is chosen
8802 to match the format in which the data was printed.
8805 @vindex $_exitcode@r{, convenience variable}
8806 The variable @code{$_exitcode} is automatically set to the exit code when
8807 the program being debugged terminates.
8810 @vindex $_sdata@r{, inspect, convenience variable}
8811 The variable @code{$_sdata} contains extra collected static tracepoint
8812 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8813 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8814 if extra static tracepoint data has not been collected.
8817 @vindex $_siginfo@r{, convenience variable}
8818 The variable @code{$_siginfo} contains extra signal information
8819 (@pxref{extra signal information}). Note that @code{$_siginfo}
8820 could be empty, if the application has not yet received any signals.
8821 For example, it will be empty before you execute the @code{run} command.
8824 @vindex $_tlb@r{, convenience variable}
8825 The variable @code{$_tlb} is automatically set when debugging
8826 applications running on MS-Windows in native mode or connected to
8827 gdbserver that supports the @code{qGetTIBAddr} request.
8828 @xref{General Query Packets}.
8829 This variable contains the address of the thread information block.
8833 On HP-UX systems, if you refer to a function or variable name that
8834 begins with a dollar sign, @value{GDBN} searches for a user or system
8835 name first, before it searches for a convenience variable.
8837 @cindex convenience functions
8838 @value{GDBN} also supplies some @dfn{convenience functions}. These
8839 have a syntax similar to convenience variables. A convenience
8840 function can be used in an expression just like an ordinary function;
8841 however, a convenience function is implemented internally to
8846 @kindex help function
8847 @cindex show all convenience functions
8848 Print a list of all convenience functions.
8855 You can refer to machine register contents, in expressions, as variables
8856 with names starting with @samp{$}. The names of registers are different
8857 for each machine; use @code{info registers} to see the names used on
8861 @kindex info registers
8862 @item info registers
8863 Print the names and values of all registers except floating-point
8864 and vector registers (in the selected stack frame).
8866 @kindex info all-registers
8867 @cindex floating point registers
8868 @item info all-registers
8869 Print the names and values of all registers, including floating-point
8870 and vector registers (in the selected stack frame).
8872 @item info registers @var{regname} @dots{}
8873 Print the @dfn{relativized} value of each specified register @var{regname}.
8874 As discussed in detail below, register values are normally relative to
8875 the selected stack frame. @var{regname} may be any register name valid on
8876 the machine you are using, with or without the initial @samp{$}.
8879 @cindex stack pointer register
8880 @cindex program counter register
8881 @cindex process status register
8882 @cindex frame pointer register
8883 @cindex standard registers
8884 @value{GDBN} has four ``standard'' register names that are available (in
8885 expressions) on most machines---whenever they do not conflict with an
8886 architecture's canonical mnemonics for registers. The register names
8887 @code{$pc} and @code{$sp} are used for the program counter register and
8888 the stack pointer. @code{$fp} is used for a register that contains a
8889 pointer to the current stack frame, and @code{$ps} is used for a
8890 register that contains the processor status. For example,
8891 you could print the program counter in hex with
8898 or print the instruction to be executed next with
8905 or add four to the stack pointer@footnote{This is a way of removing
8906 one word from the stack, on machines where stacks grow downward in
8907 memory (most machines, nowadays). This assumes that the innermost
8908 stack frame is selected; setting @code{$sp} is not allowed when other
8909 stack frames are selected. To pop entire frames off the stack,
8910 regardless of machine architecture, use @code{return};
8911 see @ref{Returning, ,Returning from a Function}.} with
8917 Whenever possible, these four standard register names are available on
8918 your machine even though the machine has different canonical mnemonics,
8919 so long as there is no conflict. The @code{info registers} command
8920 shows the canonical names. For example, on the SPARC, @code{info
8921 registers} displays the processor status register as @code{$psr} but you
8922 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8923 is an alias for the @sc{eflags} register.
8925 @value{GDBN} always considers the contents of an ordinary register as an
8926 integer when the register is examined in this way. Some machines have
8927 special registers which can hold nothing but floating point; these
8928 registers are considered to have floating point values. There is no way
8929 to refer to the contents of an ordinary register as floating point value
8930 (although you can @emph{print} it as a floating point value with
8931 @samp{print/f $@var{regname}}).
8933 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8934 means that the data format in which the register contents are saved by
8935 the operating system is not the same one that your program normally
8936 sees. For example, the registers of the 68881 floating point
8937 coprocessor are always saved in ``extended'' (raw) format, but all C
8938 programs expect to work with ``double'' (virtual) format. In such
8939 cases, @value{GDBN} normally works with the virtual format only (the format
8940 that makes sense for your program), but the @code{info registers} command
8941 prints the data in both formats.
8943 @cindex SSE registers (x86)
8944 @cindex MMX registers (x86)
8945 Some machines have special registers whose contents can be interpreted
8946 in several different ways. For example, modern x86-based machines
8947 have SSE and MMX registers that can hold several values packed
8948 together in several different formats. @value{GDBN} refers to such
8949 registers in @code{struct} notation:
8952 (@value{GDBP}) print $xmm1
8954 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8955 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8956 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8957 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8958 v4_int32 = @{0, 20657912, 11, 13@},
8959 v2_int64 = @{88725056443645952, 55834574859@},
8960 uint128 = 0x0000000d0000000b013b36f800000000
8965 To set values of such registers, you need to tell @value{GDBN} which
8966 view of the register you wish to change, as if you were assigning
8967 value to a @code{struct} member:
8970 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8973 Normally, register values are relative to the selected stack frame
8974 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8975 value that the register would contain if all stack frames farther in
8976 were exited and their saved registers restored. In order to see the
8977 true contents of hardware registers, you must select the innermost
8978 frame (with @samp{frame 0}).
8980 However, @value{GDBN} must deduce where registers are saved, from the machine
8981 code generated by your compiler. If some registers are not saved, or if
8982 @value{GDBN} is unable to locate the saved registers, the selected stack
8983 frame makes no difference.
8985 @node Floating Point Hardware
8986 @section Floating Point Hardware
8987 @cindex floating point
8989 Depending on the configuration, @value{GDBN} may be able to give
8990 you more information about the status of the floating point hardware.
8995 Display hardware-dependent information about the floating
8996 point unit. The exact contents and layout vary depending on the
8997 floating point chip. Currently, @samp{info float} is supported on
8998 the ARM and x86 machines.
9002 @section Vector Unit
9005 Depending on the configuration, @value{GDBN} may be able to give you
9006 more information about the status of the vector unit.
9011 Display information about the vector unit. The exact contents and
9012 layout vary depending on the hardware.
9015 @node OS Information
9016 @section Operating System Auxiliary Information
9017 @cindex OS information
9019 @value{GDBN} provides interfaces to useful OS facilities that can help
9020 you debug your program.
9022 @cindex @code{ptrace} system call
9023 @cindex @code{struct user} contents
9024 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9025 machines), it interfaces with the inferior via the @code{ptrace}
9026 system call. The operating system creates a special sata structure,
9027 called @code{struct user}, for this interface. You can use the
9028 command @code{info udot} to display the contents of this data
9034 Display the contents of the @code{struct user} maintained by the OS
9035 kernel for the program being debugged. @value{GDBN} displays the
9036 contents of @code{struct user} as a list of hex numbers, similar to
9037 the @code{examine} command.
9040 @cindex auxiliary vector
9041 @cindex vector, auxiliary
9042 Some operating systems supply an @dfn{auxiliary vector} to programs at
9043 startup. This is akin to the arguments and environment that you
9044 specify for a program, but contains a system-dependent variety of
9045 binary values that tell system libraries important details about the
9046 hardware, operating system, and process. Each value's purpose is
9047 identified by an integer tag; the meanings are well-known but system-specific.
9048 Depending on the configuration and operating system facilities,
9049 @value{GDBN} may be able to show you this information. For remote
9050 targets, this functionality may further depend on the remote stub's
9051 support of the @samp{qXfer:auxv:read} packet, see
9052 @ref{qXfer auxiliary vector read}.
9057 Display the auxiliary vector of the inferior, which can be either a
9058 live process or a core dump file. @value{GDBN} prints each tag value
9059 numerically, and also shows names and text descriptions for recognized
9060 tags. Some values in the vector are numbers, some bit masks, and some
9061 pointers to strings or other data. @value{GDBN} displays each value in the
9062 most appropriate form for a recognized tag, and in hexadecimal for
9063 an unrecognized tag.
9066 On some targets, @value{GDBN} can access operating-system-specific information
9067 and display it to user, without interpretation. For remote targets,
9068 this functionality depends on the remote stub's support of the
9069 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9074 List the types of OS information available for the target. If the
9075 target does not return a list of possible types, this command will
9078 @kindex info os processes
9079 @item info os processes
9080 Display the list of processes on the target. For each process,
9081 @value{GDBN} prints the process identifier, the name of the user, and
9082 the command corresponding to the process.
9085 @node Memory Region Attributes
9086 @section Memory Region Attributes
9087 @cindex memory region attributes
9089 @dfn{Memory region attributes} allow you to describe special handling
9090 required by regions of your target's memory. @value{GDBN} uses
9091 attributes to determine whether to allow certain types of memory
9092 accesses; whether to use specific width accesses; and whether to cache
9093 target memory. By default the description of memory regions is
9094 fetched from the target (if the current target supports this), but the
9095 user can override the fetched regions.
9097 Defined memory regions can be individually enabled and disabled. When a
9098 memory region is disabled, @value{GDBN} uses the default attributes when
9099 accessing memory in that region. Similarly, if no memory regions have
9100 been defined, @value{GDBN} uses the default attributes when accessing
9103 When a memory region is defined, it is given a number to identify it;
9104 to enable, disable, or remove a memory region, you specify that number.
9108 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9109 Define a memory region bounded by @var{lower} and @var{upper} with
9110 attributes @var{attributes}@dots{}, and add it to the list of regions
9111 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9112 case: it is treated as the target's maximum memory address.
9113 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9116 Discard any user changes to the memory regions and use target-supplied
9117 regions, if available, or no regions if the target does not support.
9120 @item delete mem @var{nums}@dots{}
9121 Remove memory regions @var{nums}@dots{} from the list of regions
9122 monitored by @value{GDBN}.
9125 @item disable mem @var{nums}@dots{}
9126 Disable monitoring of memory regions @var{nums}@dots{}.
9127 A disabled memory region is not forgotten.
9128 It may be enabled again later.
9131 @item enable mem @var{nums}@dots{}
9132 Enable monitoring of memory regions @var{nums}@dots{}.
9136 Print a table of all defined memory regions, with the following columns
9140 @item Memory Region Number
9141 @item Enabled or Disabled.
9142 Enabled memory regions are marked with @samp{y}.
9143 Disabled memory regions are marked with @samp{n}.
9146 The address defining the inclusive lower bound of the memory region.
9149 The address defining the exclusive upper bound of the memory region.
9152 The list of attributes set for this memory region.
9157 @subsection Attributes
9159 @subsubsection Memory Access Mode
9160 The access mode attributes set whether @value{GDBN} may make read or
9161 write accesses to a memory region.
9163 While these attributes prevent @value{GDBN} from performing invalid
9164 memory accesses, they do nothing to prevent the target system, I/O DMA,
9165 etc.@: from accessing memory.
9169 Memory is read only.
9171 Memory is write only.
9173 Memory is read/write. This is the default.
9176 @subsubsection Memory Access Size
9177 The access size attribute tells @value{GDBN} to use specific sized
9178 accesses in the memory region. Often memory mapped device registers
9179 require specific sized accesses. If no access size attribute is
9180 specified, @value{GDBN} may use accesses of any size.
9184 Use 8 bit memory accesses.
9186 Use 16 bit memory accesses.
9188 Use 32 bit memory accesses.
9190 Use 64 bit memory accesses.
9193 @c @subsubsection Hardware/Software Breakpoints
9194 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9195 @c will use hardware or software breakpoints for the internal breakpoints
9196 @c used by the step, next, finish, until, etc. commands.
9200 @c Always use hardware breakpoints
9201 @c @item swbreak (default)
9204 @subsubsection Data Cache
9205 The data cache attributes set whether @value{GDBN} will cache target
9206 memory. While this generally improves performance by reducing debug
9207 protocol overhead, it can lead to incorrect results because @value{GDBN}
9208 does not know about volatile variables or memory mapped device
9213 Enable @value{GDBN} to cache target memory.
9215 Disable @value{GDBN} from caching target memory. This is the default.
9218 @subsection Memory Access Checking
9219 @value{GDBN} can be instructed to refuse accesses to memory that is
9220 not explicitly described. This can be useful if accessing such
9221 regions has undesired effects for a specific target, or to provide
9222 better error checking. The following commands control this behaviour.
9225 @kindex set mem inaccessible-by-default
9226 @item set mem inaccessible-by-default [on|off]
9227 If @code{on} is specified, make @value{GDBN} treat memory not
9228 explicitly described by the memory ranges as non-existent and refuse accesses
9229 to such memory. The checks are only performed if there's at least one
9230 memory range defined. If @code{off} is specified, make @value{GDBN}
9231 treat the memory not explicitly described by the memory ranges as RAM.
9232 The default value is @code{on}.
9233 @kindex show mem inaccessible-by-default
9234 @item show mem inaccessible-by-default
9235 Show the current handling of accesses to unknown memory.
9239 @c @subsubsection Memory Write Verification
9240 @c The memory write verification attributes set whether @value{GDBN}
9241 @c will re-reads data after each write to verify the write was successful.
9245 @c @item noverify (default)
9248 @node Dump/Restore Files
9249 @section Copy Between Memory and a File
9250 @cindex dump/restore files
9251 @cindex append data to a file
9252 @cindex dump data to a file
9253 @cindex restore data from a file
9255 You can use the commands @code{dump}, @code{append}, and
9256 @code{restore} to copy data between target memory and a file. The
9257 @code{dump} and @code{append} commands write data to a file, and the
9258 @code{restore} command reads data from a file back into the inferior's
9259 memory. Files may be in binary, Motorola S-record, Intel hex, or
9260 Tektronix Hex format; however, @value{GDBN} can only append to binary
9266 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9267 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9268 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9269 or the value of @var{expr}, to @var{filename} in the given format.
9271 The @var{format} parameter may be any one of:
9278 Motorola S-record format.
9280 Tektronix Hex format.
9283 @value{GDBN} uses the same definitions of these formats as the
9284 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9285 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9289 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9290 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9291 Append the contents of memory from @var{start_addr} to @var{end_addr},
9292 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9293 (@value{GDBN} can only append data to files in raw binary form.)
9296 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9297 Restore the contents of file @var{filename} into memory. The
9298 @code{restore} command can automatically recognize any known @sc{bfd}
9299 file format, except for raw binary. To restore a raw binary file you
9300 must specify the optional keyword @code{binary} after the filename.
9302 If @var{bias} is non-zero, its value will be added to the addresses
9303 contained in the file. Binary files always start at address zero, so
9304 they will be restored at address @var{bias}. Other bfd files have
9305 a built-in location; they will be restored at offset @var{bias}
9308 If @var{start} and/or @var{end} are non-zero, then only data between
9309 file offset @var{start} and file offset @var{end} will be restored.
9310 These offsets are relative to the addresses in the file, before
9311 the @var{bias} argument is applied.
9315 @node Core File Generation
9316 @section How to Produce a Core File from Your Program
9317 @cindex dump core from inferior
9319 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9320 image of a running process and its process status (register values
9321 etc.). Its primary use is post-mortem debugging of a program that
9322 crashed while it ran outside a debugger. A program that crashes
9323 automatically produces a core file, unless this feature is disabled by
9324 the user. @xref{Files}, for information on invoking @value{GDBN} in
9325 the post-mortem debugging mode.
9327 Occasionally, you may wish to produce a core file of the program you
9328 are debugging in order to preserve a snapshot of its state.
9329 @value{GDBN} has a special command for that.
9333 @kindex generate-core-file
9334 @item generate-core-file [@var{file}]
9335 @itemx gcore [@var{file}]
9336 Produce a core dump of the inferior process. The optional argument
9337 @var{file} specifies the file name where to put the core dump. If not
9338 specified, the file name defaults to @file{core.@var{pid}}, where
9339 @var{pid} is the inferior process ID.
9341 Note that this command is implemented only for some systems (as of
9342 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9345 @node Character Sets
9346 @section Character Sets
9347 @cindex character sets
9349 @cindex translating between character sets
9350 @cindex host character set
9351 @cindex target character set
9353 If the program you are debugging uses a different character set to
9354 represent characters and strings than the one @value{GDBN} uses itself,
9355 @value{GDBN} can automatically translate between the character sets for
9356 you. The character set @value{GDBN} uses we call the @dfn{host
9357 character set}; the one the inferior program uses we call the
9358 @dfn{target character set}.
9360 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9361 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9362 remote protocol (@pxref{Remote Debugging}) to debug a program
9363 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9364 then the host character set is Latin-1, and the target character set is
9365 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9366 target-charset EBCDIC-US}, then @value{GDBN} translates between
9367 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9368 character and string literals in expressions.
9370 @value{GDBN} has no way to automatically recognize which character set
9371 the inferior program uses; you must tell it, using the @code{set
9372 target-charset} command, described below.
9374 Here are the commands for controlling @value{GDBN}'s character set
9378 @item set target-charset @var{charset}
9379 @kindex set target-charset
9380 Set the current target character set to @var{charset}. To display the
9381 list of supported target character sets, type
9382 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9384 @item set host-charset @var{charset}
9385 @kindex set host-charset
9386 Set the current host character set to @var{charset}.
9388 By default, @value{GDBN} uses a host character set appropriate to the
9389 system it is running on; you can override that default using the
9390 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9391 automatically determine the appropriate host character set. In this
9392 case, @value{GDBN} uses @samp{UTF-8}.
9394 @value{GDBN} can only use certain character sets as its host character
9395 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9396 @value{GDBN} will list the host character sets it supports.
9398 @item set charset @var{charset}
9400 Set the current host and target character sets to @var{charset}. As
9401 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9402 @value{GDBN} will list the names of the character sets that can be used
9403 for both host and target.
9406 @kindex show charset
9407 Show the names of the current host and target character sets.
9409 @item show host-charset
9410 @kindex show host-charset
9411 Show the name of the current host character set.
9413 @item show target-charset
9414 @kindex show target-charset
9415 Show the name of the current target character set.
9417 @item set target-wide-charset @var{charset}
9418 @kindex set target-wide-charset
9419 Set the current target's wide character set to @var{charset}. This is
9420 the character set used by the target's @code{wchar_t} type. To
9421 display the list of supported wide character sets, type
9422 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9424 @item show target-wide-charset
9425 @kindex show target-wide-charset
9426 Show the name of the current target's wide character set.
9429 Here is an example of @value{GDBN}'s character set support in action.
9430 Assume that the following source code has been placed in the file
9431 @file{charset-test.c}:
9437 = @{72, 101, 108, 108, 111, 44, 32, 119,
9438 111, 114, 108, 100, 33, 10, 0@};
9439 char ibm1047_hello[]
9440 = @{200, 133, 147, 147, 150, 107, 64, 166,
9441 150, 153, 147, 132, 90, 37, 0@};
9445 printf ("Hello, world!\n");
9449 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9450 containing the string @samp{Hello, world!} followed by a newline,
9451 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9453 We compile the program, and invoke the debugger on it:
9456 $ gcc -g charset-test.c -o charset-test
9457 $ gdb -nw charset-test
9458 GNU gdb 2001-12-19-cvs
9459 Copyright 2001 Free Software Foundation, Inc.
9464 We can use the @code{show charset} command to see what character sets
9465 @value{GDBN} is currently using to interpret and display characters and
9469 (@value{GDBP}) show charset
9470 The current host and target character set is `ISO-8859-1'.
9474 For the sake of printing this manual, let's use @sc{ascii} as our
9475 initial character set:
9477 (@value{GDBP}) set charset ASCII
9478 (@value{GDBP}) show charset
9479 The current host and target character set is `ASCII'.
9483 Let's assume that @sc{ascii} is indeed the correct character set for our
9484 host system --- in other words, let's assume that if @value{GDBN} prints
9485 characters using the @sc{ascii} character set, our terminal will display
9486 them properly. Since our current target character set is also
9487 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9490 (@value{GDBP}) print ascii_hello
9491 $1 = 0x401698 "Hello, world!\n"
9492 (@value{GDBP}) print ascii_hello[0]
9497 @value{GDBN} uses the target character set for character and string
9498 literals you use in expressions:
9501 (@value{GDBP}) print '+'
9506 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9509 @value{GDBN} relies on the user to tell it which character set the
9510 target program uses. If we print @code{ibm1047_hello} while our target
9511 character set is still @sc{ascii}, we get jibberish:
9514 (@value{GDBP}) print ibm1047_hello
9515 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9516 (@value{GDBP}) print ibm1047_hello[0]
9521 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9522 @value{GDBN} tells us the character sets it supports:
9525 (@value{GDBP}) set target-charset
9526 ASCII EBCDIC-US IBM1047 ISO-8859-1
9527 (@value{GDBP}) set target-charset
9530 We can select @sc{ibm1047} as our target character set, and examine the
9531 program's strings again. Now the @sc{ascii} string is wrong, but
9532 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9533 target character set, @sc{ibm1047}, to the host character set,
9534 @sc{ascii}, and they display correctly:
9537 (@value{GDBP}) set target-charset IBM1047
9538 (@value{GDBP}) show charset
9539 The current host character set is `ASCII'.
9540 The current target character set is `IBM1047'.
9541 (@value{GDBP}) print ascii_hello
9542 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9543 (@value{GDBP}) print ascii_hello[0]
9545 (@value{GDBP}) print ibm1047_hello
9546 $8 = 0x4016a8 "Hello, world!\n"
9547 (@value{GDBP}) print ibm1047_hello[0]
9552 As above, @value{GDBN} uses the target character set for character and
9553 string literals you use in expressions:
9556 (@value{GDBP}) print '+'
9561 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9564 @node Caching Remote Data
9565 @section Caching Data of Remote Targets
9566 @cindex caching data of remote targets
9568 @value{GDBN} caches data exchanged between the debugger and a
9569 remote target (@pxref{Remote Debugging}). Such caching generally improves
9570 performance, because it reduces the overhead of the remote protocol by
9571 bundling memory reads and writes into large chunks. Unfortunately, simply
9572 caching everything would lead to incorrect results, since @value{GDBN}
9573 does not necessarily know anything about volatile values, memory-mapped I/O
9574 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9575 memory can be changed @emph{while} a gdb command is executing.
9576 Therefore, by default, @value{GDBN} only caches data
9577 known to be on the stack@footnote{In non-stop mode, it is moderately
9578 rare for a running thread to modify the stack of a stopped thread
9579 in a way that would interfere with a backtrace, and caching of
9580 stack reads provides a significant speed up of remote backtraces.}.
9581 Other regions of memory can be explicitly marked as
9582 cacheable; see @pxref{Memory Region Attributes}.
9585 @kindex set remotecache
9586 @item set remotecache on
9587 @itemx set remotecache off
9588 This option no longer does anything; it exists for compatibility
9591 @kindex show remotecache
9592 @item show remotecache
9593 Show the current state of the obsolete remotecache flag.
9595 @kindex set stack-cache
9596 @item set stack-cache on
9597 @itemx set stack-cache off
9598 Enable or disable caching of stack accesses. When @code{ON}, use
9599 caching. By default, this option is @code{ON}.
9601 @kindex show stack-cache
9602 @item show stack-cache
9603 Show the current state of data caching for memory accesses.
9606 @item info dcache @r{[}line@r{]}
9607 Print the information about the data cache performance. The
9608 information displayed includes the dcache width and depth, and for
9609 each cache line, its number, address, and how many times it was
9610 referenced. This command is useful for debugging the data cache
9613 If a line number is specified, the contents of that line will be
9616 @item set dcache size @var{size}
9618 @kindex set dcache size
9619 Set maximum number of entries in dcache (dcache depth above).
9621 @item set dcache line-size @var{line-size}
9622 @cindex dcache line-size
9623 @kindex set dcache line-size
9624 Set number of bytes each dcache entry caches (dcache width above).
9625 Must be a power of 2.
9627 @item show dcache size
9628 @kindex show dcache size
9629 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9631 @item show dcache line-size
9632 @kindex show dcache line-size
9633 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9637 @node Searching Memory
9638 @section Search Memory
9639 @cindex searching memory
9641 Memory can be searched for a particular sequence of bytes with the
9642 @code{find} command.
9646 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9647 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9648 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9649 etc. The search begins at address @var{start_addr} and continues for either
9650 @var{len} bytes or through to @var{end_addr} inclusive.
9653 @var{s} and @var{n} are optional parameters.
9654 They may be specified in either order, apart or together.
9657 @item @var{s}, search query size
9658 The size of each search query value.
9664 halfwords (two bytes)
9668 giant words (eight bytes)
9671 All values are interpreted in the current language.
9672 This means, for example, that if the current source language is C/C@t{++}
9673 then searching for the string ``hello'' includes the trailing '\0'.
9675 If the value size is not specified, it is taken from the
9676 value's type in the current language.
9677 This is useful when one wants to specify the search
9678 pattern as a mixture of types.
9679 Note that this means, for example, that in the case of C-like languages
9680 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9681 which is typically four bytes.
9683 @item @var{n}, maximum number of finds
9684 The maximum number of matches to print. The default is to print all finds.
9687 You can use strings as search values. Quote them with double-quotes
9689 The string value is copied into the search pattern byte by byte,
9690 regardless of the endianness of the target and the size specification.
9692 The address of each match found is printed as well as a count of the
9693 number of matches found.
9695 The address of the last value found is stored in convenience variable
9697 A count of the number of matches is stored in @samp{$numfound}.
9699 For example, if stopped at the @code{printf} in this function:
9705 static char hello[] = "hello-hello";
9706 static struct @{ char c; short s; int i; @}
9707 __attribute__ ((packed)) mixed
9708 = @{ 'c', 0x1234, 0x87654321 @};
9709 printf ("%s\n", hello);
9714 you get during debugging:
9717 (gdb) find &hello[0], +sizeof(hello), "hello"
9718 0x804956d <hello.1620+6>
9720 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9721 0x8049567 <hello.1620>
9722 0x804956d <hello.1620+6>
9724 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9725 0x8049567 <hello.1620>
9727 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9728 0x8049560 <mixed.1625>
9730 (gdb) print $numfound
9733 $2 = (void *) 0x8049560
9736 @node Optimized Code
9737 @chapter Debugging Optimized Code
9738 @cindex optimized code, debugging
9739 @cindex debugging optimized code
9741 Almost all compilers support optimization. With optimization
9742 disabled, the compiler generates assembly code that corresponds
9743 directly to your source code, in a simplistic way. As the compiler
9744 applies more powerful optimizations, the generated assembly code
9745 diverges from your original source code. With help from debugging
9746 information generated by the compiler, @value{GDBN} can map from
9747 the running program back to constructs from your original source.
9749 @value{GDBN} is more accurate with optimization disabled. If you
9750 can recompile without optimization, it is easier to follow the
9751 progress of your program during debugging. But, there are many cases
9752 where you may need to debug an optimized version.
9754 When you debug a program compiled with @samp{-g -O}, remember that the
9755 optimizer has rearranged your code; the debugger shows you what is
9756 really there. Do not be too surprised when the execution path does not
9757 exactly match your source file! An extreme example: if you define a
9758 variable, but never use it, @value{GDBN} never sees that
9759 variable---because the compiler optimizes it out of existence.
9761 Some things do not work as well with @samp{-g -O} as with just
9762 @samp{-g}, particularly on machines with instruction scheduling. If in
9763 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9764 please report it to us as a bug (including a test case!).
9765 @xref{Variables}, for more information about debugging optimized code.
9768 * Inline Functions:: How @value{GDBN} presents inlining
9769 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9772 @node Inline Functions
9773 @section Inline Functions
9774 @cindex inline functions, debugging
9776 @dfn{Inlining} is an optimization that inserts a copy of the function
9777 body directly at each call site, instead of jumping to a shared
9778 routine. @value{GDBN} displays inlined functions just like
9779 non-inlined functions. They appear in backtraces. You can view their
9780 arguments and local variables, step into them with @code{step}, skip
9781 them with @code{next}, and escape from them with @code{finish}.
9782 You can check whether a function was inlined by using the
9783 @code{info frame} command.
9785 For @value{GDBN} to support inlined functions, the compiler must
9786 record information about inlining in the debug information ---
9787 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9788 other compilers do also. @value{GDBN} only supports inlined functions
9789 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9790 do not emit two required attributes (@samp{DW_AT_call_file} and
9791 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9792 function calls with earlier versions of @value{NGCC}. It instead
9793 displays the arguments and local variables of inlined functions as
9794 local variables in the caller.
9796 The body of an inlined function is directly included at its call site;
9797 unlike a non-inlined function, there are no instructions devoted to
9798 the call. @value{GDBN} still pretends that the call site and the
9799 start of the inlined function are different instructions. Stepping to
9800 the call site shows the call site, and then stepping again shows
9801 the first line of the inlined function, even though no additional
9802 instructions are executed.
9804 This makes source-level debugging much clearer; you can see both the
9805 context of the call and then the effect of the call. Only stepping by
9806 a single instruction using @code{stepi} or @code{nexti} does not do
9807 this; single instruction steps always show the inlined body.
9809 There are some ways that @value{GDBN} does not pretend that inlined
9810 function calls are the same as normal calls:
9814 You cannot set breakpoints on inlined functions. @value{GDBN}
9815 either reports that there is no symbol with that name, or else sets the
9816 breakpoint only on non-inlined copies of the function. This limitation
9817 will be removed in a future version of @value{GDBN}; until then,
9818 set a breakpoint by line number on the first line of the inlined
9822 Setting breakpoints at the call site of an inlined function may not
9823 work, because the call site does not contain any code. @value{GDBN}
9824 may incorrectly move the breakpoint to the next line of the enclosing
9825 function, after the call. This limitation will be removed in a future
9826 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9827 or inside the inlined function instead.
9830 @value{GDBN} cannot locate the return value of inlined calls after
9831 using the @code{finish} command. This is a limitation of compiler-generated
9832 debugging information; after @code{finish}, you can step to the next line
9833 and print a variable where your program stored the return value.
9837 @node Tail Call Frames
9838 @section Tail Call Frames
9839 @cindex tail call frames, debugging
9841 Function @code{B} can call function @code{C} in its very last statement. In
9842 unoptimized compilation the call of @code{C} is immediately followed by return
9843 instruction at the end of @code{B} code. Optimizing compiler may replace the
9844 call and return in function @code{B} into one jump to function @code{C}
9845 instead. Such use of a jump instruction is called @dfn{tail call}.
9847 During execution of function @code{C}, there will be no indication in the
9848 function call stack frames that it was tail-called from @code{B}. If function
9849 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9850 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9851 some cases @value{GDBN} can determine that @code{C} was tail-called from
9852 @code{B}, and it will then create fictitious call frame for that, with the
9853 return address set up as if @code{B} called @code{C} normally.
9855 This functionality is currently supported only by DWARF 2 debugging format and
9856 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9857 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9860 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9861 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9865 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9867 Stack level 1, frame at 0x7fffffffda30:
9868 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9869 tail call frame, caller of frame at 0x7fffffffda30
9870 source language c++.
9871 Arglist at unknown address.
9872 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9875 The detection of all the possible code path executions can find them ambiguous.
9876 There is no execution history stored (possible @ref{Reverse Execution} is never
9877 used for this purpose) and the last known caller could have reached the known
9878 callee by multiple different jump sequences. In such case @value{GDBN} still
9879 tries to show at least all the unambiguous top tail callers and all the
9880 unambiguous bottom tail calees, if any.
9883 @anchor{set debug entry-values}
9884 @item set debug entry-values
9885 @kindex set debug entry-values
9886 When set to on, enables printing of analysis messages for both frame argument
9887 values at function entry and tail calls. It will show all the possible valid
9888 tail calls code paths it has considered. It will also print the intersection
9889 of them with the final unambiguous (possibly partial or even empty) code path
9892 @item show debug entry-values
9893 @kindex show debug entry-values
9894 Show the current state of analysis messages printing for both frame argument
9895 values at function entry and tail calls.
9898 The analysis messages for tail calls can for example show why the virtual tail
9899 call frame for function @code{c} has not been recognized (due to the indirect
9900 reference by variable @code{x}):
9903 static void __attribute__((noinline, noclone)) c (void);
9904 void (*x) (void) = c;
9905 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9906 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9907 int main (void) @{ x (); return 0; @}
9909 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9910 DW_TAG_GNU_call_site 0x40039a in main
9912 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9915 #1 0x000000000040039a in main () at t.c:5
9918 Another possibility is an ambiguous virtual tail call frames resolution:
9922 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9923 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9924 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9925 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9926 static void __attribute__((noinline, noclone)) b (void)
9927 @{ if (i) c (); else e (); @}
9928 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9929 int main (void) @{ a (); return 0; @}
9931 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9932 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9933 tailcall: reduced: 0x4004d2(a) |
9936 #1 0x00000000004004d2 in a () at t.c:8
9937 #2 0x0000000000400395 in main () at t.c:9
9940 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9941 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9943 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9944 @ifset HAVE_MAKEINFO_CLICK
9946 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9947 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9949 @ifclear HAVE_MAKEINFO_CLICK
9951 @set CALLSEQ1B @value{CALLSEQ1A}
9952 @set CALLSEQ2B @value{CALLSEQ2A}
9955 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9956 The code can have possible execution paths @value{CALLSEQ1B} or
9957 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9959 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9960 has found. It then finds another possible calling sequcen - that one is
9961 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9962 printed as the @code{reduced:} calling sequence. That one could have many
9963 futher @code{compare:} and @code{reduced:} statements as long as there remain
9964 any non-ambiguous sequence entries.
9966 For the frame of function @code{b} in both cases there are different possible
9967 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9968 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9969 therefore this one is displayed to the user while the ambiguous frames are
9972 There can be also reasons why printing of frame argument values at function
9977 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9978 static void __attribute__((noinline, noclone)) a (int i);
9979 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9980 static void __attribute__((noinline, noclone)) a (int i)
9981 @{ if (i) b (i - 1); else c (0); @}
9982 int main (void) @{ a (5); return 0; @}
9985 #0 c (i=i@@entry=0) at t.c:2
9986 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9987 function "a" at 0x400420 can call itself via tail calls
9988 i=<optimized out>) at t.c:6
9989 #2 0x000000000040036e in main () at t.c:7
9992 @value{GDBN} cannot find out from the inferior state if and how many times did
9993 function @code{a} call itself (via function @code{b}) as these calls would be
9994 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9995 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9996 prints @code{<optimized out>} instead.
9999 @chapter C Preprocessor Macros
10001 Some languages, such as C and C@t{++}, provide a way to define and invoke
10002 ``preprocessor macros'' which expand into strings of tokens.
10003 @value{GDBN} can evaluate expressions containing macro invocations, show
10004 the result of macro expansion, and show a macro's definition, including
10005 where it was defined.
10007 You may need to compile your program specially to provide @value{GDBN}
10008 with information about preprocessor macros. Most compilers do not
10009 include macros in their debugging information, even when you compile
10010 with the @option{-g} flag. @xref{Compilation}.
10012 A program may define a macro at one point, remove that definition later,
10013 and then provide a different definition after that. Thus, at different
10014 points in the program, a macro may have different definitions, or have
10015 no definition at all. If there is a current stack frame, @value{GDBN}
10016 uses the macros in scope at that frame's source code line. Otherwise,
10017 @value{GDBN} uses the macros in scope at the current listing location;
10020 Whenever @value{GDBN} evaluates an expression, it always expands any
10021 macro invocations present in the expression. @value{GDBN} also provides
10022 the following commands for working with macros explicitly.
10026 @kindex macro expand
10027 @cindex macro expansion, showing the results of preprocessor
10028 @cindex preprocessor macro expansion, showing the results of
10029 @cindex expanding preprocessor macros
10030 @item macro expand @var{expression}
10031 @itemx macro exp @var{expression}
10032 Show the results of expanding all preprocessor macro invocations in
10033 @var{expression}. Since @value{GDBN} simply expands macros, but does
10034 not parse the result, @var{expression} need not be a valid expression;
10035 it can be any string of tokens.
10038 @item macro expand-once @var{expression}
10039 @itemx macro exp1 @var{expression}
10040 @cindex expand macro once
10041 @i{(This command is not yet implemented.)} Show the results of
10042 expanding those preprocessor macro invocations that appear explicitly in
10043 @var{expression}. Macro invocations appearing in that expansion are
10044 left unchanged. This command allows you to see the effect of a
10045 particular macro more clearly, without being confused by further
10046 expansions. Since @value{GDBN} simply expands macros, but does not
10047 parse the result, @var{expression} need not be a valid expression; it
10048 can be any string of tokens.
10051 @cindex macro definition, showing
10052 @cindex definition of a macro, showing
10053 @cindex macros, from debug info
10054 @item info macro [-a|-all] [--] @var{macro}
10055 Show the current definition or all definitions of the named @var{macro},
10056 and describe the source location or compiler command-line where that
10057 definition was established. The optional double dash is to signify the end of
10058 argument processing and the beginning of @var{macro} for non C-like macros where
10059 the macro may begin with a hyphen.
10061 @kindex info macros
10062 @item info macros @var{linespec}
10063 Show all macro definitions that are in effect at the location specified
10064 by @var{linespec}, and describe the source location or compiler
10065 command-line where those definitions were established.
10067 @kindex macro define
10068 @cindex user-defined macros
10069 @cindex defining macros interactively
10070 @cindex macros, user-defined
10071 @item macro define @var{macro} @var{replacement-list}
10072 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10073 Introduce a definition for a preprocessor macro named @var{macro},
10074 invocations of which are replaced by the tokens given in
10075 @var{replacement-list}. The first form of this command defines an
10076 ``object-like'' macro, which takes no arguments; the second form
10077 defines a ``function-like'' macro, which takes the arguments given in
10080 A definition introduced by this command is in scope in every
10081 expression evaluated in @value{GDBN}, until it is removed with the
10082 @code{macro undef} command, described below. The definition overrides
10083 all definitions for @var{macro} present in the program being debugged,
10084 as well as any previous user-supplied definition.
10086 @kindex macro undef
10087 @item macro undef @var{macro}
10088 Remove any user-supplied definition for the macro named @var{macro}.
10089 This command only affects definitions provided with the @code{macro
10090 define} command, described above; it cannot remove definitions present
10091 in the program being debugged.
10095 List all the macros defined using the @code{macro define} command.
10098 @cindex macros, example of debugging with
10099 Here is a transcript showing the above commands in action. First, we
10100 show our source files:
10105 #include "sample.h"
10108 #define ADD(x) (M + x)
10113 printf ("Hello, world!\n");
10115 printf ("We're so creative.\n");
10117 printf ("Goodbye, world!\n");
10124 Now, we compile the program using the @sc{gnu} C compiler,
10125 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10126 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10127 and @option{-gdwarf-4}; we recommend always choosing the most recent
10128 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10129 includes information about preprocessor macros in the debugging
10133 $ gcc -gdwarf-2 -g3 sample.c -o sample
10137 Now, we start @value{GDBN} on our sample program:
10141 GNU gdb 2002-05-06-cvs
10142 Copyright 2002 Free Software Foundation, Inc.
10143 GDB is free software, @dots{}
10147 We can expand macros and examine their definitions, even when the
10148 program is not running. @value{GDBN} uses the current listing position
10149 to decide which macro definitions are in scope:
10152 (@value{GDBP}) list main
10155 5 #define ADD(x) (M + x)
10160 10 printf ("Hello, world!\n");
10162 12 printf ("We're so creative.\n");
10163 (@value{GDBP}) info macro ADD
10164 Defined at /home/jimb/gdb/macros/play/sample.c:5
10165 #define ADD(x) (M + x)
10166 (@value{GDBP}) info macro Q
10167 Defined at /home/jimb/gdb/macros/play/sample.h:1
10168 included at /home/jimb/gdb/macros/play/sample.c:2
10170 (@value{GDBP}) macro expand ADD(1)
10171 expands to: (42 + 1)
10172 (@value{GDBP}) macro expand-once ADD(1)
10173 expands to: once (M + 1)
10177 In the example above, note that @code{macro expand-once} expands only
10178 the macro invocation explicit in the original text --- the invocation of
10179 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10180 which was introduced by @code{ADD}.
10182 Once the program is running, @value{GDBN} uses the macro definitions in
10183 force at the source line of the current stack frame:
10186 (@value{GDBP}) break main
10187 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10189 Starting program: /home/jimb/gdb/macros/play/sample
10191 Breakpoint 1, main () at sample.c:10
10192 10 printf ("Hello, world!\n");
10196 At line 10, the definition of the macro @code{N} at line 9 is in force:
10199 (@value{GDBP}) info macro N
10200 Defined at /home/jimb/gdb/macros/play/sample.c:9
10202 (@value{GDBP}) macro expand N Q M
10203 expands to: 28 < 42
10204 (@value{GDBP}) print N Q M
10209 As we step over directives that remove @code{N}'s definition, and then
10210 give it a new definition, @value{GDBN} finds the definition (or lack
10211 thereof) in force at each point:
10214 (@value{GDBP}) next
10216 12 printf ("We're so creative.\n");
10217 (@value{GDBP}) info macro N
10218 The symbol `N' has no definition as a C/C++ preprocessor macro
10219 at /home/jimb/gdb/macros/play/sample.c:12
10220 (@value{GDBP}) next
10222 14 printf ("Goodbye, world!\n");
10223 (@value{GDBP}) info macro N
10224 Defined at /home/jimb/gdb/macros/play/sample.c:13
10226 (@value{GDBP}) macro expand N Q M
10227 expands to: 1729 < 42
10228 (@value{GDBP}) print N Q M
10233 In addition to source files, macros can be defined on the compilation command
10234 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10235 such a way, @value{GDBN} displays the location of their definition as line zero
10236 of the source file submitted to the compiler.
10239 (@value{GDBP}) info macro __STDC__
10240 Defined at /home/jimb/gdb/macros/play/sample.c:0
10247 @chapter Tracepoints
10248 @c This chapter is based on the documentation written by Michael
10249 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10251 @cindex tracepoints
10252 In some applications, it is not feasible for the debugger to interrupt
10253 the program's execution long enough for the developer to learn
10254 anything helpful about its behavior. If the program's correctness
10255 depends on its real-time behavior, delays introduced by a debugger
10256 might cause the program to change its behavior drastically, or perhaps
10257 fail, even when the code itself is correct. It is useful to be able
10258 to observe the program's behavior without interrupting it.
10260 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10261 specify locations in the program, called @dfn{tracepoints}, and
10262 arbitrary expressions to evaluate when those tracepoints are reached.
10263 Later, using the @code{tfind} command, you can examine the values
10264 those expressions had when the program hit the tracepoints. The
10265 expressions may also denote objects in memory---structures or arrays,
10266 for example---whose values @value{GDBN} should record; while visiting
10267 a particular tracepoint, you may inspect those objects as if they were
10268 in memory at that moment. However, because @value{GDBN} records these
10269 values without interacting with you, it can do so quickly and
10270 unobtrusively, hopefully not disturbing the program's behavior.
10272 The tracepoint facility is currently available only for remote
10273 targets. @xref{Targets}. In addition, your remote target must know
10274 how to collect trace data. This functionality is implemented in the
10275 remote stub; however, none of the stubs distributed with @value{GDBN}
10276 support tracepoints as of this writing. The format of the remote
10277 packets used to implement tracepoints are described in @ref{Tracepoint
10280 It is also possible to get trace data from a file, in a manner reminiscent
10281 of corefiles; you specify the filename, and use @code{tfind} to search
10282 through the file. @xref{Trace Files}, for more details.
10284 This chapter describes the tracepoint commands and features.
10287 * Set Tracepoints::
10288 * Analyze Collected Data::
10289 * Tracepoint Variables::
10293 @node Set Tracepoints
10294 @section Commands to Set Tracepoints
10296 Before running such a @dfn{trace experiment}, an arbitrary number of
10297 tracepoints can be set. A tracepoint is actually a special type of
10298 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10299 standard breakpoint commands. For instance, as with breakpoints,
10300 tracepoint numbers are successive integers starting from one, and many
10301 of the commands associated with tracepoints take the tracepoint number
10302 as their argument, to identify which tracepoint to work on.
10304 For each tracepoint, you can specify, in advance, some arbitrary set
10305 of data that you want the target to collect in the trace buffer when
10306 it hits that tracepoint. The collected data can include registers,
10307 local variables, or global data. Later, you can use @value{GDBN}
10308 commands to examine the values these data had at the time the
10309 tracepoint was hit.
10311 Tracepoints do not support every breakpoint feature. Ignore counts on
10312 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10313 commands when they are hit. Tracepoints may not be thread-specific
10316 @cindex fast tracepoints
10317 Some targets may support @dfn{fast tracepoints}, which are inserted in
10318 a different way (such as with a jump instead of a trap), that is
10319 faster but possibly restricted in where they may be installed.
10321 @cindex static tracepoints
10322 @cindex markers, static tracepoints
10323 @cindex probing markers, static tracepoints
10324 Regular and fast tracepoints are dynamic tracing facilities, meaning
10325 that they can be used to insert tracepoints at (almost) any location
10326 in the target. Some targets may also support controlling @dfn{static
10327 tracepoints} from @value{GDBN}. With static tracing, a set of
10328 instrumentation points, also known as @dfn{markers}, are embedded in
10329 the target program, and can be activated or deactivated by name or
10330 address. These are usually placed at locations which facilitate
10331 investigating what the target is actually doing. @value{GDBN}'s
10332 support for static tracing includes being able to list instrumentation
10333 points, and attach them with @value{GDBN} defined high level
10334 tracepoints that expose the whole range of convenience of
10335 @value{GDBN}'s tracepoints support. Namely, support for collecting
10336 registers values and values of global or local (to the instrumentation
10337 point) variables; tracepoint conditions and trace state variables.
10338 The act of installing a @value{GDBN} static tracepoint on an
10339 instrumentation point, or marker, is referred to as @dfn{probing} a
10340 static tracepoint marker.
10342 @code{gdbserver} supports tracepoints on some target systems.
10343 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10345 This section describes commands to set tracepoints and associated
10346 conditions and actions.
10349 * Create and Delete Tracepoints::
10350 * Enable and Disable Tracepoints::
10351 * Tracepoint Passcounts::
10352 * Tracepoint Conditions::
10353 * Trace State Variables::
10354 * Tracepoint Actions::
10355 * Listing Tracepoints::
10356 * Listing Static Tracepoint Markers::
10357 * Starting and Stopping Trace Experiments::
10358 * Tracepoint Restrictions::
10361 @node Create and Delete Tracepoints
10362 @subsection Create and Delete Tracepoints
10365 @cindex set tracepoint
10367 @item trace @var{location}
10368 The @code{trace} command is very similar to the @code{break} command.
10369 Its argument @var{location} can be a source line, a function name, or
10370 an address in the target program. @xref{Specify Location}. The
10371 @code{trace} command defines a tracepoint, which is a point in the
10372 target program where the debugger will briefly stop, collect some
10373 data, and then allow the program to continue. Setting a tracepoint or
10374 changing its actions takes effect immediately if the remote stub
10375 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10377 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10378 these changes don't take effect until the next @code{tstart}
10379 command, and once a trace experiment is running, further changes will
10380 not have any effect until the next trace experiment starts. In addition,
10381 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10382 address is not yet resolved. (This is similar to pending breakpoints.)
10383 Pending tracepoints are not downloaded to the target and not installed
10384 until they are resolved. The resolution of pending tracepoints requires
10385 @value{GDBN} support---when debugging with the remote target, and
10386 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10387 tracing}), pending tracepoints can not be resolved (and downloaded to
10388 the remote stub) while @value{GDBN} is disconnected.
10390 Here are some examples of using the @code{trace} command:
10393 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10395 (@value{GDBP}) @b{trace +2} // 2 lines forward
10397 (@value{GDBP}) @b{trace my_function} // first source line of function
10399 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10401 (@value{GDBP}) @b{trace *0x2117c4} // an address
10405 You can abbreviate @code{trace} as @code{tr}.
10407 @item trace @var{location} if @var{cond}
10408 Set a tracepoint with condition @var{cond}; evaluate the expression
10409 @var{cond} each time the tracepoint is reached, and collect data only
10410 if the value is nonzero---that is, if @var{cond} evaluates as true.
10411 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10412 information on tracepoint conditions.
10414 @item ftrace @var{location} [ if @var{cond} ]
10415 @cindex set fast tracepoint
10416 @cindex fast tracepoints, setting
10418 The @code{ftrace} command sets a fast tracepoint. For targets that
10419 support them, fast tracepoints will use a more efficient but possibly
10420 less general technique to trigger data collection, such as a jump
10421 instruction instead of a trap, or some sort of hardware support. It
10422 may not be possible to create a fast tracepoint at the desired
10423 location, in which case the command will exit with an explanatory
10426 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10429 On 32-bit x86-architecture systems, fast tracepoints normally need to
10430 be placed at an instruction that is 5 bytes or longer, but can be
10431 placed at 4-byte instructions if the low 64K of memory of the target
10432 program is available to install trampolines. Some Unix-type systems,
10433 such as @sc{gnu}/Linux, exclude low addresses from the program's
10434 address space; but for instance with the Linux kernel it is possible
10435 to let @value{GDBN} use this area by doing a @command{sysctl} command
10436 to set the @code{mmap_min_addr} kernel parameter, as in
10439 sudo sysctl -w vm.mmap_min_addr=32768
10443 which sets the low address to 32K, which leaves plenty of room for
10444 trampolines. The minimum address should be set to a page boundary.
10446 @item strace @var{location} [ if @var{cond} ]
10447 @cindex set static tracepoint
10448 @cindex static tracepoints, setting
10449 @cindex probe static tracepoint marker
10451 The @code{strace} command sets a static tracepoint. For targets that
10452 support it, setting a static tracepoint probes a static
10453 instrumentation point, or marker, found at @var{location}. It may not
10454 be possible to set a static tracepoint at the desired location, in
10455 which case the command will exit with an explanatory message.
10457 @value{GDBN} handles arguments to @code{strace} exactly as for
10458 @code{trace}, with the addition that the user can also specify
10459 @code{-m @var{marker}} as @var{location}. This probes the marker
10460 identified by the @var{marker} string identifier. This identifier
10461 depends on the static tracepoint backend library your program is
10462 using. You can find all the marker identifiers in the @samp{ID} field
10463 of the @code{info static-tracepoint-markers} command output.
10464 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10465 Markers}. For example, in the following small program using the UST
10471 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10476 the marker id is composed of joining the first two arguments to the
10477 @code{trace_mark} call with a slash, which translates to:
10480 (@value{GDBP}) info static-tracepoint-markers
10481 Cnt Enb ID Address What
10482 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10488 so you may probe the marker above with:
10491 (@value{GDBP}) strace -m ust/bar33
10494 Static tracepoints accept an extra collect action --- @code{collect
10495 $_sdata}. This collects arbitrary user data passed in the probe point
10496 call to the tracing library. In the UST example above, you'll see
10497 that the third argument to @code{trace_mark} is a printf-like format
10498 string. The user data is then the result of running that formating
10499 string against the following arguments. Note that @code{info
10500 static-tracepoint-markers} command output lists that format string in
10501 the @samp{Data:} field.
10503 You can inspect this data when analyzing the trace buffer, by printing
10504 the $_sdata variable like any other variable available to
10505 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10508 @cindex last tracepoint number
10509 @cindex recent tracepoint number
10510 @cindex tracepoint number
10511 The convenience variable @code{$tpnum} records the tracepoint number
10512 of the most recently set tracepoint.
10514 @kindex delete tracepoint
10515 @cindex tracepoint deletion
10516 @item delete tracepoint @r{[}@var{num}@r{]}
10517 Permanently delete one or more tracepoints. With no argument, the
10518 default is to delete all tracepoints. Note that the regular
10519 @code{delete} command can remove tracepoints also.
10524 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10526 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10530 You can abbreviate this command as @code{del tr}.
10533 @node Enable and Disable Tracepoints
10534 @subsection Enable and Disable Tracepoints
10536 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10539 @kindex disable tracepoint
10540 @item disable tracepoint @r{[}@var{num}@r{]}
10541 Disable tracepoint @var{num}, or all tracepoints if no argument
10542 @var{num} is given. A disabled tracepoint will have no effect during
10543 a trace experiment, but it is not forgotten. You can re-enable
10544 a disabled tracepoint using the @code{enable tracepoint} command.
10545 If the command is issued during a trace experiment and the debug target
10546 has support for disabling tracepoints during a trace experiment, then the
10547 change will be effective immediately. Otherwise, it will be applied to the
10548 next trace experiment.
10550 @kindex enable tracepoint
10551 @item enable tracepoint @r{[}@var{num}@r{]}
10552 Enable tracepoint @var{num}, or all tracepoints. If this command is
10553 issued during a trace experiment and the debug target supports enabling
10554 tracepoints during a trace experiment, then the enabled tracepoints will
10555 become effective immediately. Otherwise, they will become effective the
10556 next time a trace experiment is run.
10559 @node Tracepoint Passcounts
10560 @subsection Tracepoint Passcounts
10564 @cindex tracepoint pass count
10565 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10566 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10567 automatically stop a trace experiment. If a tracepoint's passcount is
10568 @var{n}, then the trace experiment will be automatically stopped on
10569 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10570 @var{num} is not specified, the @code{passcount} command sets the
10571 passcount of the most recently defined tracepoint. If no passcount is
10572 given, the trace experiment will run until stopped explicitly by the
10578 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10579 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10581 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10582 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10583 (@value{GDBP}) @b{trace foo}
10584 (@value{GDBP}) @b{pass 3}
10585 (@value{GDBP}) @b{trace bar}
10586 (@value{GDBP}) @b{pass 2}
10587 (@value{GDBP}) @b{trace baz}
10588 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10589 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10590 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10591 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10595 @node Tracepoint Conditions
10596 @subsection Tracepoint Conditions
10597 @cindex conditional tracepoints
10598 @cindex tracepoint conditions
10600 The simplest sort of tracepoint collects data every time your program
10601 reaches a specified place. You can also specify a @dfn{condition} for
10602 a tracepoint. A condition is just a Boolean expression in your
10603 programming language (@pxref{Expressions, ,Expressions}). A
10604 tracepoint with a condition evaluates the expression each time your
10605 program reaches it, and data collection happens only if the condition
10608 Tracepoint conditions can be specified when a tracepoint is set, by
10609 using @samp{if} in the arguments to the @code{trace} command.
10610 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10611 also be set or changed at any time with the @code{condition} command,
10612 just as with breakpoints.
10614 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10615 the conditional expression itself. Instead, @value{GDBN} encodes the
10616 expression into an agent expression (@pxref{Agent Expressions})
10617 suitable for execution on the target, independently of @value{GDBN}.
10618 Global variables become raw memory locations, locals become stack
10619 accesses, and so forth.
10621 For instance, suppose you have a function that is usually called
10622 frequently, but should not be called after an error has occurred. You
10623 could use the following tracepoint command to collect data about calls
10624 of that function that happen while the error code is propagating
10625 through the program; an unconditional tracepoint could end up
10626 collecting thousands of useless trace frames that you would have to
10630 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10633 @node Trace State Variables
10634 @subsection Trace State Variables
10635 @cindex trace state variables
10637 A @dfn{trace state variable} is a special type of variable that is
10638 created and managed by target-side code. The syntax is the same as
10639 that for GDB's convenience variables (a string prefixed with ``$''),
10640 but they are stored on the target. They must be created explicitly,
10641 using a @code{tvariable} command. They are always 64-bit signed
10644 Trace state variables are remembered by @value{GDBN}, and downloaded
10645 to the target along with tracepoint information when the trace
10646 experiment starts. There are no intrinsic limits on the number of
10647 trace state variables, beyond memory limitations of the target.
10649 @cindex convenience variables, and trace state variables
10650 Although trace state variables are managed by the target, you can use
10651 them in print commands and expressions as if they were convenience
10652 variables; @value{GDBN} will get the current value from the target
10653 while the trace experiment is running. Trace state variables share
10654 the same namespace as other ``$'' variables, which means that you
10655 cannot have trace state variables with names like @code{$23} or
10656 @code{$pc}, nor can you have a trace state variable and a convenience
10657 variable with the same name.
10661 @item tvariable $@var{name} [ = @var{expression} ]
10663 The @code{tvariable} command creates a new trace state variable named
10664 @code{$@var{name}}, and optionally gives it an initial value of
10665 @var{expression}. @var{expression} is evaluated when this command is
10666 entered; the result will be converted to an integer if possible,
10667 otherwise @value{GDBN} will report an error. A subsequent
10668 @code{tvariable} command specifying the same name does not create a
10669 variable, but instead assigns the supplied initial value to the
10670 existing variable of that name, overwriting any previous initial
10671 value. The default initial value is 0.
10673 @item info tvariables
10674 @kindex info tvariables
10675 List all the trace state variables along with their initial values.
10676 Their current values may also be displayed, if the trace experiment is
10679 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10680 @kindex delete tvariable
10681 Delete the given trace state variables, or all of them if no arguments
10686 @node Tracepoint Actions
10687 @subsection Tracepoint Action Lists
10691 @cindex tracepoint actions
10692 @item actions @r{[}@var{num}@r{]}
10693 This command will prompt for a list of actions to be taken when the
10694 tracepoint is hit. If the tracepoint number @var{num} is not
10695 specified, this command sets the actions for the one that was most
10696 recently defined (so that you can define a tracepoint and then say
10697 @code{actions} without bothering about its number). You specify the
10698 actions themselves on the following lines, one action at a time, and
10699 terminate the actions list with a line containing just @code{end}. So
10700 far, the only defined actions are @code{collect}, @code{teval}, and
10701 @code{while-stepping}.
10703 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10704 Commands, ,Breakpoint Command Lists}), except that only the defined
10705 actions are allowed; any other @value{GDBN} command is rejected.
10707 @cindex remove actions from a tracepoint
10708 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10709 and follow it immediately with @samp{end}.
10712 (@value{GDBP}) @b{collect @var{data}} // collect some data
10714 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10716 (@value{GDBP}) @b{end} // signals the end of actions.
10719 In the following example, the action list begins with @code{collect}
10720 commands indicating the things to be collected when the tracepoint is
10721 hit. Then, in order to single-step and collect additional data
10722 following the tracepoint, a @code{while-stepping} command is used,
10723 followed by the list of things to be collected after each step in a
10724 sequence of single steps. The @code{while-stepping} command is
10725 terminated by its own separate @code{end} command. Lastly, the action
10726 list is terminated by an @code{end} command.
10729 (@value{GDBP}) @b{trace foo}
10730 (@value{GDBP}) @b{actions}
10731 Enter actions for tracepoint 1, one per line:
10734 > while-stepping 12
10735 > collect $pc, arr[i]
10740 @kindex collect @r{(tracepoints)}
10741 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10742 Collect values of the given expressions when the tracepoint is hit.
10743 This command accepts a comma-separated list of any valid expressions.
10744 In addition to global, static, or local variables, the following
10745 special arguments are supported:
10749 Collect all registers.
10752 Collect all function arguments.
10755 Collect all local variables.
10758 Collect the return address. This is helpful if you want to see more
10762 @vindex $_sdata@r{, collect}
10763 Collect static tracepoint marker specific data. Only available for
10764 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10765 Lists}. On the UST static tracepoints library backend, an
10766 instrumentation point resembles a @code{printf} function call. The
10767 tracing library is able to collect user specified data formatted to a
10768 character string using the format provided by the programmer that
10769 instrumented the program. Other backends have similar mechanisms.
10770 Here's an example of a UST marker call:
10773 const char master_name[] = "$your_name";
10774 trace_mark(channel1, marker1, "hello %s", master_name)
10777 In this case, collecting @code{$_sdata} collects the string
10778 @samp{hello $yourname}. When analyzing the trace buffer, you can
10779 inspect @samp{$_sdata} like any other variable available to
10783 You can give several consecutive @code{collect} commands, each one
10784 with a single argument, or one @code{collect} command with several
10785 arguments separated by commas; the effect is the same.
10787 The optional @var{mods} changes the usual handling of the arguments.
10788 @code{s} requests that pointers to chars be handled as strings, in
10789 particular collecting the contents of the memory being pointed at, up
10790 to the first zero. The upper bound is by default the value of the
10791 @code{print elements} variable; if @code{s} is followed by a decimal
10792 number, that is the upper bound instead. So for instance
10793 @samp{collect/s25 mystr} collects as many as 25 characters at
10796 The command @code{info scope} (@pxref{Symbols, info scope}) is
10797 particularly useful for figuring out what data to collect.
10799 @kindex teval @r{(tracepoints)}
10800 @item teval @var{expr1}, @var{expr2}, @dots{}
10801 Evaluate the given expressions when the tracepoint is hit. This
10802 command accepts a comma-separated list of expressions. The results
10803 are discarded, so this is mainly useful for assigning values to trace
10804 state variables (@pxref{Trace State Variables}) without adding those
10805 values to the trace buffer, as would be the case if the @code{collect}
10808 @kindex while-stepping @r{(tracepoints)}
10809 @item while-stepping @var{n}
10810 Perform @var{n} single-step instruction traces after the tracepoint,
10811 collecting new data after each step. The @code{while-stepping}
10812 command is followed by the list of what to collect while stepping
10813 (followed by its own @code{end} command):
10816 > while-stepping 12
10817 > collect $regs, myglobal
10823 Note that @code{$pc} is not automatically collected by
10824 @code{while-stepping}; you need to explicitly collect that register if
10825 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10828 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10829 @kindex set default-collect
10830 @cindex default collection action
10831 This variable is a list of expressions to collect at each tracepoint
10832 hit. It is effectively an additional @code{collect} action prepended
10833 to every tracepoint action list. The expressions are parsed
10834 individually for each tracepoint, so for instance a variable named
10835 @code{xyz} may be interpreted as a global for one tracepoint, and a
10836 local for another, as appropriate to the tracepoint's location.
10838 @item show default-collect
10839 @kindex show default-collect
10840 Show the list of expressions that are collected by default at each
10845 @node Listing Tracepoints
10846 @subsection Listing Tracepoints
10849 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10850 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10851 @cindex information about tracepoints
10852 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10853 Display information about the tracepoint @var{num}. If you don't
10854 specify a tracepoint number, displays information about all the
10855 tracepoints defined so far. The format is similar to that used for
10856 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10857 command, simply restricting itself to tracepoints.
10859 A tracepoint's listing may include additional information specific to
10864 its passcount as given by the @code{passcount @var{n}} command
10868 (@value{GDBP}) @b{info trace}
10869 Num Type Disp Enb Address What
10870 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10872 collect globfoo, $regs
10881 This command can be abbreviated @code{info tp}.
10884 @node Listing Static Tracepoint Markers
10885 @subsection Listing Static Tracepoint Markers
10888 @kindex info static-tracepoint-markers
10889 @cindex information about static tracepoint markers
10890 @item info static-tracepoint-markers
10891 Display information about all static tracepoint markers defined in the
10894 For each marker, the following columns are printed:
10898 An incrementing counter, output to help readability. This is not a
10901 The marker ID, as reported by the target.
10902 @item Enabled or Disabled
10903 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10904 that are not enabled.
10906 Where the marker is in your program, as a memory address.
10908 Where the marker is in the source for your program, as a file and line
10909 number. If the debug information included in the program does not
10910 allow @value{GDBN} to locate the source of the marker, this column
10911 will be left blank.
10915 In addition, the following information may be printed for each marker:
10919 User data passed to the tracing library by the marker call. In the
10920 UST backend, this is the format string passed as argument to the
10922 @item Static tracepoints probing the marker
10923 The list of static tracepoints attached to the marker.
10927 (@value{GDBP}) info static-tracepoint-markers
10928 Cnt ID Enb Address What
10929 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10930 Data: number1 %d number2 %d
10931 Probed by static tracepoints: #2
10932 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10938 @node Starting and Stopping Trace Experiments
10939 @subsection Starting and Stopping Trace Experiments
10942 @kindex tstart [ @var{notes} ]
10943 @cindex start a new trace experiment
10944 @cindex collected data discarded
10946 This command starts the trace experiment, and begins collecting data.
10947 It has the side effect of discarding all the data collected in the
10948 trace buffer during the previous trace experiment. If any arguments
10949 are supplied, they are taken as a note and stored with the trace
10950 experiment's state. The notes may be arbitrary text, and are
10951 especially useful with disconnected tracing in a multi-user context;
10952 the notes can explain what the trace is doing, supply user contact
10953 information, and so forth.
10955 @kindex tstop [ @var{notes} ]
10956 @cindex stop a running trace experiment
10958 This command stops the trace experiment. If any arguments are
10959 supplied, they are recorded with the experiment as a note. This is
10960 useful if you are stopping a trace started by someone else, for
10961 instance if the trace is interfering with the system's behavior and
10962 needs to be stopped quickly.
10964 @strong{Note}: a trace experiment and data collection may stop
10965 automatically if any tracepoint's passcount is reached
10966 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10969 @cindex status of trace data collection
10970 @cindex trace experiment, status of
10972 This command displays the status of the current trace data
10976 Here is an example of the commands we described so far:
10979 (@value{GDBP}) @b{trace gdb_c_test}
10980 (@value{GDBP}) @b{actions}
10981 Enter actions for tracepoint #1, one per line.
10982 > collect $regs,$locals,$args
10983 > while-stepping 11
10987 (@value{GDBP}) @b{tstart}
10988 [time passes @dots{}]
10989 (@value{GDBP}) @b{tstop}
10992 @anchor{disconnected tracing}
10993 @cindex disconnected tracing
10994 You can choose to continue running the trace experiment even if
10995 @value{GDBN} disconnects from the target, voluntarily or
10996 involuntarily. For commands such as @code{detach}, the debugger will
10997 ask what you want to do with the trace. But for unexpected
10998 terminations (@value{GDBN} crash, network outage), it would be
10999 unfortunate to lose hard-won trace data, so the variable
11000 @code{disconnected-tracing} lets you decide whether the trace should
11001 continue running without @value{GDBN}.
11004 @item set disconnected-tracing on
11005 @itemx set disconnected-tracing off
11006 @kindex set disconnected-tracing
11007 Choose whether a tracing run should continue to run if @value{GDBN}
11008 has disconnected from the target. Note that @code{detach} or
11009 @code{quit} will ask you directly what to do about a running trace no
11010 matter what this variable's setting, so the variable is mainly useful
11011 for handling unexpected situations, such as loss of the network.
11013 @item show disconnected-tracing
11014 @kindex show disconnected-tracing
11015 Show the current choice for disconnected tracing.
11019 When you reconnect to the target, the trace experiment may or may not
11020 still be running; it might have filled the trace buffer in the
11021 meantime, or stopped for one of the other reasons. If it is running,
11022 it will continue after reconnection.
11024 Upon reconnection, the target will upload information about the
11025 tracepoints in effect. @value{GDBN} will then compare that
11026 information to the set of tracepoints currently defined, and attempt
11027 to match them up, allowing for the possibility that the numbers may
11028 have changed due to creation and deletion in the meantime. If one of
11029 the target's tracepoints does not match any in @value{GDBN}, the
11030 debugger will create a new tracepoint, so that you have a number with
11031 which to specify that tracepoint. This matching-up process is
11032 necessarily heuristic, and it may result in useless tracepoints being
11033 created; you may simply delete them if they are of no use.
11035 @cindex circular trace buffer
11036 If your target agent supports a @dfn{circular trace buffer}, then you
11037 can run a trace experiment indefinitely without filling the trace
11038 buffer; when space runs out, the agent deletes already-collected trace
11039 frames, oldest first, until there is enough room to continue
11040 collecting. This is especially useful if your tracepoints are being
11041 hit too often, and your trace gets terminated prematurely because the
11042 buffer is full. To ask for a circular trace buffer, simply set
11043 @samp{circular-trace-buffer} to on. You can set this at any time,
11044 including during tracing; if the agent can do it, it will change
11045 buffer handling on the fly, otherwise it will not take effect until
11049 @item set circular-trace-buffer on
11050 @itemx set circular-trace-buffer off
11051 @kindex set circular-trace-buffer
11052 Choose whether a tracing run should use a linear or circular buffer
11053 for trace data. A linear buffer will not lose any trace data, but may
11054 fill up prematurely, while a circular buffer will discard old trace
11055 data, but it will have always room for the latest tracepoint hits.
11057 @item show circular-trace-buffer
11058 @kindex show circular-trace-buffer
11059 Show the current choice for the trace buffer. Note that this may not
11060 match the agent's current buffer handling, nor is it guaranteed to
11061 match the setting that might have been in effect during a past run,
11062 for instance if you are looking at frames from a trace file.
11067 @item set trace-user @var{text}
11068 @kindex set trace-user
11070 @item show trace-user
11071 @kindex show trace-user
11073 @item set trace-notes @var{text}
11074 @kindex set trace-notes
11075 Set the trace run's notes.
11077 @item show trace-notes
11078 @kindex show trace-notes
11079 Show the trace run's notes.
11081 @item set trace-stop-notes @var{text}
11082 @kindex set trace-stop-notes
11083 Set the trace run's stop notes. The handling of the note is as for
11084 @code{tstop} arguments; the set command is convenient way to fix a
11085 stop note that is mistaken or incomplete.
11087 @item show trace-stop-notes
11088 @kindex show trace-stop-notes
11089 Show the trace run's stop notes.
11093 @node Tracepoint Restrictions
11094 @subsection Tracepoint Restrictions
11096 @cindex tracepoint restrictions
11097 There are a number of restrictions on the use of tracepoints. As
11098 described above, tracepoint data gathering occurs on the target
11099 without interaction from @value{GDBN}. Thus the full capabilities of
11100 the debugger are not available during data gathering, and then at data
11101 examination time, you will be limited by only having what was
11102 collected. The following items describe some common problems, but it
11103 is not exhaustive, and you may run into additional difficulties not
11109 Tracepoint expressions are intended to gather objects (lvalues). Thus
11110 the full flexibility of GDB's expression evaluator is not available.
11111 You cannot call functions, cast objects to aggregate types, access
11112 convenience variables or modify values (except by assignment to trace
11113 state variables). Some language features may implicitly call
11114 functions (for instance Objective-C fields with accessors), and therefore
11115 cannot be collected either.
11118 Collection of local variables, either individually or in bulk with
11119 @code{$locals} or @code{$args}, during @code{while-stepping} may
11120 behave erratically. The stepping action may enter a new scope (for
11121 instance by stepping into a function), or the location of the variable
11122 may change (for instance it is loaded into a register). The
11123 tracepoint data recorded uses the location information for the
11124 variables that is correct for the tracepoint location. When the
11125 tracepoint is created, it is not possible, in general, to determine
11126 where the steps of a @code{while-stepping} sequence will advance the
11127 program---particularly if a conditional branch is stepped.
11130 Collection of an incompletely-initialized or partially-destroyed object
11131 may result in something that @value{GDBN} cannot display, or displays
11132 in a misleading way.
11135 When @value{GDBN} displays a pointer to character it automatically
11136 dereferences the pointer to also display characters of the string
11137 being pointed to. However, collecting the pointer during tracing does
11138 not automatically collect the string. You need to explicitly
11139 dereference the pointer and provide size information if you want to
11140 collect not only the pointer, but the memory pointed to. For example,
11141 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11145 It is not possible to collect a complete stack backtrace at a
11146 tracepoint. Instead, you may collect the registers and a few hundred
11147 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11148 (adjust to use the name of the actual stack pointer register on your
11149 target architecture, and the amount of stack you wish to capture).
11150 Then the @code{backtrace} command will show a partial backtrace when
11151 using a trace frame. The number of stack frames that can be examined
11152 depends on the sizes of the frames in the collected stack. Note that
11153 if you ask for a block so large that it goes past the bottom of the
11154 stack, the target agent may report an error trying to read from an
11158 If you do not collect registers at a tracepoint, @value{GDBN} can
11159 infer that the value of @code{$pc} must be the same as the address of
11160 the tracepoint and use that when you are looking at a trace frame
11161 for that tracepoint. However, this cannot work if the tracepoint has
11162 multiple locations (for instance if it was set in a function that was
11163 inlined), or if it has a @code{while-stepping} loop. In those cases
11164 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11169 @node Analyze Collected Data
11170 @section Using the Collected Data
11172 After the tracepoint experiment ends, you use @value{GDBN} commands
11173 for examining the trace data. The basic idea is that each tracepoint
11174 collects a trace @dfn{snapshot} every time it is hit and another
11175 snapshot every time it single-steps. All these snapshots are
11176 consecutively numbered from zero and go into a buffer, and you can
11177 examine them later. The way you examine them is to @dfn{focus} on a
11178 specific trace snapshot. When the remote stub is focused on a trace
11179 snapshot, it will respond to all @value{GDBN} requests for memory and
11180 registers by reading from the buffer which belongs to that snapshot,
11181 rather than from @emph{real} memory or registers of the program being
11182 debugged. This means that @strong{all} @value{GDBN} commands
11183 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11184 behave as if we were currently debugging the program state as it was
11185 when the tracepoint occurred. Any requests for data that are not in
11186 the buffer will fail.
11189 * tfind:: How to select a trace snapshot
11190 * tdump:: How to display all data for a snapshot
11191 * save tracepoints:: How to save tracepoints for a future run
11195 @subsection @code{tfind @var{n}}
11198 @cindex select trace snapshot
11199 @cindex find trace snapshot
11200 The basic command for selecting a trace snapshot from the buffer is
11201 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11202 counting from zero. If no argument @var{n} is given, the next
11203 snapshot is selected.
11205 Here are the various forms of using the @code{tfind} command.
11209 Find the first snapshot in the buffer. This is a synonym for
11210 @code{tfind 0} (since 0 is the number of the first snapshot).
11213 Stop debugging trace snapshots, resume @emph{live} debugging.
11216 Same as @samp{tfind none}.
11219 No argument means find the next trace snapshot.
11222 Find the previous trace snapshot before the current one. This permits
11223 retracing earlier steps.
11225 @item tfind tracepoint @var{num}
11226 Find the next snapshot associated with tracepoint @var{num}. Search
11227 proceeds forward from the last examined trace snapshot. If no
11228 argument @var{num} is given, it means find the next snapshot collected
11229 for the same tracepoint as the current snapshot.
11231 @item tfind pc @var{addr}
11232 Find the next snapshot associated with the value @var{addr} of the
11233 program counter. Search proceeds forward from the last examined trace
11234 snapshot. If no argument @var{addr} is given, it means find the next
11235 snapshot with the same value of PC as the current snapshot.
11237 @item tfind outside @var{addr1}, @var{addr2}
11238 Find the next snapshot whose PC is outside the given range of
11239 addresses (exclusive).
11241 @item tfind range @var{addr1}, @var{addr2}
11242 Find the next snapshot whose PC is between @var{addr1} and
11243 @var{addr2} (inclusive).
11245 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11246 Find the next snapshot associated with the source line @var{n}. If
11247 the optional argument @var{file} is given, refer to line @var{n} in
11248 that source file. Search proceeds forward from the last examined
11249 trace snapshot. If no argument @var{n} is given, it means find the
11250 next line other than the one currently being examined; thus saying
11251 @code{tfind line} repeatedly can appear to have the same effect as
11252 stepping from line to line in a @emph{live} debugging session.
11255 The default arguments for the @code{tfind} commands are specifically
11256 designed to make it easy to scan through the trace buffer. For
11257 instance, @code{tfind} with no argument selects the next trace
11258 snapshot, and @code{tfind -} with no argument selects the previous
11259 trace snapshot. So, by giving one @code{tfind} command, and then
11260 simply hitting @key{RET} repeatedly you can examine all the trace
11261 snapshots in order. Or, by saying @code{tfind -} and then hitting
11262 @key{RET} repeatedly you can examine the snapshots in reverse order.
11263 The @code{tfind line} command with no argument selects the snapshot
11264 for the next source line executed. The @code{tfind pc} command with
11265 no argument selects the next snapshot with the same program counter
11266 (PC) as the current frame. The @code{tfind tracepoint} command with
11267 no argument selects the next trace snapshot collected by the same
11268 tracepoint as the current one.
11270 In addition to letting you scan through the trace buffer manually,
11271 these commands make it easy to construct @value{GDBN} scripts that
11272 scan through the trace buffer and print out whatever collected data
11273 you are interested in. Thus, if we want to examine the PC, FP, and SP
11274 registers from each trace frame in the buffer, we can say this:
11277 (@value{GDBP}) @b{tfind start}
11278 (@value{GDBP}) @b{while ($trace_frame != -1)}
11279 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11280 $trace_frame, $pc, $sp, $fp
11284 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11285 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11286 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11287 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11288 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11289 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11290 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11291 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11292 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11293 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11294 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11297 Or, if we want to examine the variable @code{X} at each source line in
11301 (@value{GDBP}) @b{tfind start}
11302 (@value{GDBP}) @b{while ($trace_frame != -1)}
11303 > printf "Frame %d, X == %d\n", $trace_frame, X
11313 @subsection @code{tdump}
11315 @cindex dump all data collected at tracepoint
11316 @cindex tracepoint data, display
11318 This command takes no arguments. It prints all the data collected at
11319 the current trace snapshot.
11322 (@value{GDBP}) @b{trace 444}
11323 (@value{GDBP}) @b{actions}
11324 Enter actions for tracepoint #2, one per line:
11325 > collect $regs, $locals, $args, gdb_long_test
11328 (@value{GDBP}) @b{tstart}
11330 (@value{GDBP}) @b{tfind line 444}
11331 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11333 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11335 (@value{GDBP}) @b{tdump}
11336 Data collected at tracepoint 2, trace frame 1:
11337 d0 0xc4aa0085 -995491707
11341 d4 0x71aea3d 119204413
11344 d7 0x380035 3670069
11345 a0 0x19e24a 1696330
11346 a1 0x3000668 50333288
11348 a3 0x322000 3284992
11349 a4 0x3000698 50333336
11350 a5 0x1ad3cc 1758156
11351 fp 0x30bf3c 0x30bf3c
11352 sp 0x30bf34 0x30bf34
11354 pc 0x20b2c8 0x20b2c8
11358 p = 0x20e5b4 "gdb-test"
11365 gdb_long_test = 17 '\021'
11370 @code{tdump} works by scanning the tracepoint's current collection
11371 actions and printing the value of each expression listed. So
11372 @code{tdump} can fail, if after a run, you change the tracepoint's
11373 actions to mention variables that were not collected during the run.
11375 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11376 uses the collected value of @code{$pc} to distinguish between trace
11377 frames that were collected at the tracepoint hit, and frames that were
11378 collected while stepping. This allows it to correctly choose whether
11379 to display the basic list of collections, or the collections from the
11380 body of the while-stepping loop. However, if @code{$pc} was not collected,
11381 then @code{tdump} will always attempt to dump using the basic collection
11382 list, and may fail if a while-stepping frame does not include all the
11383 same data that is collected at the tracepoint hit.
11384 @c This is getting pretty arcane, example would be good.
11386 @node save tracepoints
11387 @subsection @code{save tracepoints @var{filename}}
11388 @kindex save tracepoints
11389 @kindex save-tracepoints
11390 @cindex save tracepoints for future sessions
11392 This command saves all current tracepoint definitions together with
11393 their actions and passcounts, into a file @file{@var{filename}}
11394 suitable for use in a later debugging session. To read the saved
11395 tracepoint definitions, use the @code{source} command (@pxref{Command
11396 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11397 alias for @w{@code{save tracepoints}}
11399 @node Tracepoint Variables
11400 @section Convenience Variables for Tracepoints
11401 @cindex tracepoint variables
11402 @cindex convenience variables for tracepoints
11405 @vindex $trace_frame
11406 @item (int) $trace_frame
11407 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11408 snapshot is selected.
11410 @vindex $tracepoint
11411 @item (int) $tracepoint
11412 The tracepoint for the current trace snapshot.
11414 @vindex $trace_line
11415 @item (int) $trace_line
11416 The line number for the current trace snapshot.
11418 @vindex $trace_file
11419 @item (char []) $trace_file
11420 The source file for the current trace snapshot.
11422 @vindex $trace_func
11423 @item (char []) $trace_func
11424 The name of the function containing @code{$tracepoint}.
11427 Note: @code{$trace_file} is not suitable for use in @code{printf},
11428 use @code{output} instead.
11430 Here's a simple example of using these convenience variables for
11431 stepping through all the trace snapshots and printing some of their
11432 data. Note that these are not the same as trace state variables,
11433 which are managed by the target.
11436 (@value{GDBP}) @b{tfind start}
11438 (@value{GDBP}) @b{while $trace_frame != -1}
11439 > output $trace_file
11440 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11446 @section Using Trace Files
11447 @cindex trace files
11449 In some situations, the target running a trace experiment may no
11450 longer be available; perhaps it crashed, or the hardware was needed
11451 for a different activity. To handle these cases, you can arrange to
11452 dump the trace data into a file, and later use that file as a source
11453 of trace data, via the @code{target tfile} command.
11458 @item tsave [ -r ] @var{filename}
11459 Save the trace data to @var{filename}. By default, this command
11460 assumes that @var{filename} refers to the host filesystem, so if
11461 necessary @value{GDBN} will copy raw trace data up from the target and
11462 then save it. If the target supports it, you can also supply the
11463 optional argument @code{-r} (``remote'') to direct the target to save
11464 the data directly into @var{filename} in its own filesystem, which may be
11465 more efficient if the trace buffer is very large. (Note, however, that
11466 @code{target tfile} can only read from files accessible to the host.)
11468 @kindex target tfile
11470 @item target tfile @var{filename}
11471 Use the file named @var{filename} as a source of trace data. Commands
11472 that examine data work as they do with a live target, but it is not
11473 possible to run any new trace experiments. @code{tstatus} will report
11474 the state of the trace run at the moment the data was saved, as well
11475 as the current trace frame you are examining. @var{filename} must be
11476 on a filesystem accessible to the host.
11481 @chapter Debugging Programs That Use Overlays
11484 If your program is too large to fit completely in your target system's
11485 memory, you can sometimes use @dfn{overlays} to work around this
11486 problem. @value{GDBN} provides some support for debugging programs that
11490 * How Overlays Work:: A general explanation of overlays.
11491 * Overlay Commands:: Managing overlays in @value{GDBN}.
11492 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11493 mapped by asking the inferior.
11494 * Overlay Sample Program:: A sample program using overlays.
11497 @node How Overlays Work
11498 @section How Overlays Work
11499 @cindex mapped overlays
11500 @cindex unmapped overlays
11501 @cindex load address, overlay's
11502 @cindex mapped address
11503 @cindex overlay area
11505 Suppose you have a computer whose instruction address space is only 64
11506 kilobytes long, but which has much more memory which can be accessed by
11507 other means: special instructions, segment registers, or memory
11508 management hardware, for example. Suppose further that you want to
11509 adapt a program which is larger than 64 kilobytes to run on this system.
11511 One solution is to identify modules of your program which are relatively
11512 independent, and need not call each other directly; call these modules
11513 @dfn{overlays}. Separate the overlays from the main program, and place
11514 their machine code in the larger memory. Place your main program in
11515 instruction memory, but leave at least enough space there to hold the
11516 largest overlay as well.
11518 Now, to call a function located in an overlay, you must first copy that
11519 overlay's machine code from the large memory into the space set aside
11520 for it in the instruction memory, and then jump to its entry point
11523 @c NB: In the below the mapped area's size is greater or equal to the
11524 @c size of all overlays. This is intentional to remind the developer
11525 @c that overlays don't necessarily need to be the same size.
11529 Data Instruction Larger
11530 Address Space Address Space Address Space
11531 +-----------+ +-----------+ +-----------+
11533 +-----------+ +-----------+ +-----------+<-- overlay 1
11534 | program | | main | .----| overlay 1 | load address
11535 | variables | | program | | +-----------+
11536 | and heap | | | | | |
11537 +-----------+ | | | +-----------+<-- overlay 2
11538 | | +-----------+ | | | load address
11539 +-----------+ | | | .-| overlay 2 |
11541 mapped --->+-----------+ | | +-----------+
11542 address | | | | | |
11543 | overlay | <-' | | |
11544 | area | <---' +-----------+<-- overlay 3
11545 | | <---. | | load address
11546 +-----------+ `--| overlay 3 |
11553 @anchor{A code overlay}A code overlay
11557 The diagram (@pxref{A code overlay}) shows a system with separate data
11558 and instruction address spaces. To map an overlay, the program copies
11559 its code from the larger address space to the instruction address space.
11560 Since the overlays shown here all use the same mapped address, only one
11561 may be mapped at a time. For a system with a single address space for
11562 data and instructions, the diagram would be similar, except that the
11563 program variables and heap would share an address space with the main
11564 program and the overlay area.
11566 An overlay loaded into instruction memory and ready for use is called a
11567 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11568 instruction memory. An overlay not present (or only partially present)
11569 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11570 is its address in the larger memory. The mapped address is also called
11571 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11572 called the @dfn{load memory address}, or @dfn{LMA}.
11574 Unfortunately, overlays are not a completely transparent way to adapt a
11575 program to limited instruction memory. They introduce a new set of
11576 global constraints you must keep in mind as you design your program:
11581 Before calling or returning to a function in an overlay, your program
11582 must make sure that overlay is actually mapped. Otherwise, the call or
11583 return will transfer control to the right address, but in the wrong
11584 overlay, and your program will probably crash.
11587 If the process of mapping an overlay is expensive on your system, you
11588 will need to choose your overlays carefully to minimize their effect on
11589 your program's performance.
11592 The executable file you load onto your system must contain each
11593 overlay's instructions, appearing at the overlay's load address, not its
11594 mapped address. However, each overlay's instructions must be relocated
11595 and its symbols defined as if the overlay were at its mapped address.
11596 You can use GNU linker scripts to specify different load and relocation
11597 addresses for pieces of your program; see @ref{Overlay Description,,,
11598 ld.info, Using ld: the GNU linker}.
11601 The procedure for loading executable files onto your system must be able
11602 to load their contents into the larger address space as well as the
11603 instruction and data spaces.
11607 The overlay system described above is rather simple, and could be
11608 improved in many ways:
11613 If your system has suitable bank switch registers or memory management
11614 hardware, you could use those facilities to make an overlay's load area
11615 contents simply appear at their mapped address in instruction space.
11616 This would probably be faster than copying the overlay to its mapped
11617 area in the usual way.
11620 If your overlays are small enough, you could set aside more than one
11621 overlay area, and have more than one overlay mapped at a time.
11624 You can use overlays to manage data, as well as instructions. In
11625 general, data overlays are even less transparent to your design than
11626 code overlays: whereas code overlays only require care when you call or
11627 return to functions, data overlays require care every time you access
11628 the data. Also, if you change the contents of a data overlay, you
11629 must copy its contents back out to its load address before you can copy a
11630 different data overlay into the same mapped area.
11635 @node Overlay Commands
11636 @section Overlay Commands
11638 To use @value{GDBN}'s overlay support, each overlay in your program must
11639 correspond to a separate section of the executable file. The section's
11640 virtual memory address and load memory address must be the overlay's
11641 mapped and load addresses. Identifying overlays with sections allows
11642 @value{GDBN} to determine the appropriate address of a function or
11643 variable, depending on whether the overlay is mapped or not.
11645 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11646 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11651 Disable @value{GDBN}'s overlay support. When overlay support is
11652 disabled, @value{GDBN} assumes that all functions and variables are
11653 always present at their mapped addresses. By default, @value{GDBN}'s
11654 overlay support is disabled.
11656 @item overlay manual
11657 @cindex manual overlay debugging
11658 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11659 relies on you to tell it which overlays are mapped, and which are not,
11660 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11661 commands described below.
11663 @item overlay map-overlay @var{overlay}
11664 @itemx overlay map @var{overlay}
11665 @cindex map an overlay
11666 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11667 be the name of the object file section containing the overlay. When an
11668 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11669 functions and variables at their mapped addresses. @value{GDBN} assumes
11670 that any other overlays whose mapped ranges overlap that of
11671 @var{overlay} are now unmapped.
11673 @item overlay unmap-overlay @var{overlay}
11674 @itemx overlay unmap @var{overlay}
11675 @cindex unmap an overlay
11676 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11677 must be the name of the object file section containing the overlay.
11678 When an overlay is unmapped, @value{GDBN} assumes it can find the
11679 overlay's functions and variables at their load addresses.
11682 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11683 consults a data structure the overlay manager maintains in the inferior
11684 to see which overlays are mapped. For details, see @ref{Automatic
11685 Overlay Debugging}.
11687 @item overlay load-target
11688 @itemx overlay load
11689 @cindex reloading the overlay table
11690 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11691 re-reads the table @value{GDBN} automatically each time the inferior
11692 stops, so this command should only be necessary if you have changed the
11693 overlay mapping yourself using @value{GDBN}. This command is only
11694 useful when using automatic overlay debugging.
11696 @item overlay list-overlays
11697 @itemx overlay list
11698 @cindex listing mapped overlays
11699 Display a list of the overlays currently mapped, along with their mapped
11700 addresses, load addresses, and sizes.
11704 Normally, when @value{GDBN} prints a code address, it includes the name
11705 of the function the address falls in:
11708 (@value{GDBP}) print main
11709 $3 = @{int ()@} 0x11a0 <main>
11712 When overlay debugging is enabled, @value{GDBN} recognizes code in
11713 unmapped overlays, and prints the names of unmapped functions with
11714 asterisks around them. For example, if @code{foo} is a function in an
11715 unmapped overlay, @value{GDBN} prints it this way:
11718 (@value{GDBP}) overlay list
11719 No sections are mapped.
11720 (@value{GDBP}) print foo
11721 $5 = @{int (int)@} 0x100000 <*foo*>
11724 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11728 (@value{GDBP}) overlay list
11729 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11730 mapped at 0x1016 - 0x104a
11731 (@value{GDBP}) print foo
11732 $6 = @{int (int)@} 0x1016 <foo>
11735 When overlay debugging is enabled, @value{GDBN} can find the correct
11736 address for functions and variables in an overlay, whether or not the
11737 overlay is mapped. This allows most @value{GDBN} commands, like
11738 @code{break} and @code{disassemble}, to work normally, even on unmapped
11739 code. However, @value{GDBN}'s breakpoint support has some limitations:
11743 @cindex breakpoints in overlays
11744 @cindex overlays, setting breakpoints in
11745 You can set breakpoints in functions in unmapped overlays, as long as
11746 @value{GDBN} can write to the overlay at its load address.
11748 @value{GDBN} can not set hardware or simulator-based breakpoints in
11749 unmapped overlays. However, if you set a breakpoint at the end of your
11750 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11751 you are using manual overlay management), @value{GDBN} will re-set its
11752 breakpoints properly.
11756 @node Automatic Overlay Debugging
11757 @section Automatic Overlay Debugging
11758 @cindex automatic overlay debugging
11760 @value{GDBN} can automatically track which overlays are mapped and which
11761 are not, given some simple co-operation from the overlay manager in the
11762 inferior. If you enable automatic overlay debugging with the
11763 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11764 looks in the inferior's memory for certain variables describing the
11765 current state of the overlays.
11767 Here are the variables your overlay manager must define to support
11768 @value{GDBN}'s automatic overlay debugging:
11772 @item @code{_ovly_table}:
11773 This variable must be an array of the following structures:
11778 /* The overlay's mapped address. */
11781 /* The size of the overlay, in bytes. */
11782 unsigned long size;
11784 /* The overlay's load address. */
11787 /* Non-zero if the overlay is currently mapped;
11789 unsigned long mapped;
11793 @item @code{_novlys}:
11794 This variable must be a four-byte signed integer, holding the total
11795 number of elements in @code{_ovly_table}.
11799 To decide whether a particular overlay is mapped or not, @value{GDBN}
11800 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11801 @code{lma} members equal the VMA and LMA of the overlay's section in the
11802 executable file. When @value{GDBN} finds a matching entry, it consults
11803 the entry's @code{mapped} member to determine whether the overlay is
11806 In addition, your overlay manager may define a function called
11807 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11808 will silently set a breakpoint there. If the overlay manager then
11809 calls this function whenever it has changed the overlay table, this
11810 will enable @value{GDBN} to accurately keep track of which overlays
11811 are in program memory, and update any breakpoints that may be set
11812 in overlays. This will allow breakpoints to work even if the
11813 overlays are kept in ROM or other non-writable memory while they
11814 are not being executed.
11816 @node Overlay Sample Program
11817 @section Overlay Sample Program
11818 @cindex overlay example program
11820 When linking a program which uses overlays, you must place the overlays
11821 at their load addresses, while relocating them to run at their mapped
11822 addresses. To do this, you must write a linker script (@pxref{Overlay
11823 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11824 since linker scripts are specific to a particular host system, target
11825 architecture, and target memory layout, this manual cannot provide
11826 portable sample code demonstrating @value{GDBN}'s overlay support.
11828 However, the @value{GDBN} source distribution does contain an overlaid
11829 program, with linker scripts for a few systems, as part of its test
11830 suite. The program consists of the following files from
11831 @file{gdb/testsuite/gdb.base}:
11835 The main program file.
11837 A simple overlay manager, used by @file{overlays.c}.
11842 Overlay modules, loaded and used by @file{overlays.c}.
11845 Linker scripts for linking the test program on the @code{d10v-elf}
11846 and @code{m32r-elf} targets.
11849 You can build the test program using the @code{d10v-elf} GCC
11850 cross-compiler like this:
11853 $ d10v-elf-gcc -g -c overlays.c
11854 $ d10v-elf-gcc -g -c ovlymgr.c
11855 $ d10v-elf-gcc -g -c foo.c
11856 $ d10v-elf-gcc -g -c bar.c
11857 $ d10v-elf-gcc -g -c baz.c
11858 $ d10v-elf-gcc -g -c grbx.c
11859 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11860 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11863 The build process is identical for any other architecture, except that
11864 you must substitute the appropriate compiler and linker script for the
11865 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11869 @chapter Using @value{GDBN} with Different Languages
11872 Although programming languages generally have common aspects, they are
11873 rarely expressed in the same manner. For instance, in ANSI C,
11874 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11875 Modula-2, it is accomplished by @code{p^}. Values can also be
11876 represented (and displayed) differently. Hex numbers in C appear as
11877 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11879 @cindex working language
11880 Language-specific information is built into @value{GDBN} for some languages,
11881 allowing you to express operations like the above in your program's
11882 native language, and allowing @value{GDBN} to output values in a manner
11883 consistent with the syntax of your program's native language. The
11884 language you use to build expressions is called the @dfn{working
11888 * Setting:: Switching between source languages
11889 * Show:: Displaying the language
11890 * Checks:: Type and range checks
11891 * Supported Languages:: Supported languages
11892 * Unsupported Languages:: Unsupported languages
11896 @section Switching Between Source Languages
11898 There are two ways to control the working language---either have @value{GDBN}
11899 set it automatically, or select it manually yourself. You can use the
11900 @code{set language} command for either purpose. On startup, @value{GDBN}
11901 defaults to setting the language automatically. The working language is
11902 used to determine how expressions you type are interpreted, how values
11905 In addition to the working language, every source file that
11906 @value{GDBN} knows about has its own working language. For some object
11907 file formats, the compiler might indicate which language a particular
11908 source file is in. However, most of the time @value{GDBN} infers the
11909 language from the name of the file. The language of a source file
11910 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11911 show each frame appropriately for its own language. There is no way to
11912 set the language of a source file from within @value{GDBN}, but you can
11913 set the language associated with a filename extension. @xref{Show, ,
11914 Displaying the Language}.
11916 This is most commonly a problem when you use a program, such
11917 as @code{cfront} or @code{f2c}, that generates C but is written in
11918 another language. In that case, make the
11919 program use @code{#line} directives in its C output; that way
11920 @value{GDBN} will know the correct language of the source code of the original
11921 program, and will display that source code, not the generated C code.
11924 * Filenames:: Filename extensions and languages.
11925 * Manually:: Setting the working language manually
11926 * Automatically:: Having @value{GDBN} infer the source language
11930 @subsection List of Filename Extensions and Languages
11932 If a source file name ends in one of the following extensions, then
11933 @value{GDBN} infers that its language is the one indicated.
11951 C@t{++} source file
11957 Objective-C source file
11961 Fortran source file
11964 Modula-2 source file
11968 Assembler source file. This actually behaves almost like C, but
11969 @value{GDBN} does not skip over function prologues when stepping.
11972 In addition, you may set the language associated with a filename
11973 extension. @xref{Show, , Displaying the Language}.
11976 @subsection Setting the Working Language
11978 If you allow @value{GDBN} to set the language automatically,
11979 expressions are interpreted the same way in your debugging session and
11982 @kindex set language
11983 If you wish, you may set the language manually. To do this, issue the
11984 command @samp{set language @var{lang}}, where @var{lang} is the name of
11985 a language, such as
11986 @code{c} or @code{modula-2}.
11987 For a list of the supported languages, type @samp{set language}.
11989 Setting the language manually prevents @value{GDBN} from updating the working
11990 language automatically. This can lead to confusion if you try
11991 to debug a program when the working language is not the same as the
11992 source language, when an expression is acceptable to both
11993 languages---but means different things. For instance, if the current
11994 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12002 might not have the effect you intended. In C, this means to add
12003 @code{b} and @code{c} and place the result in @code{a}. The result
12004 printed would be the value of @code{a}. In Modula-2, this means to compare
12005 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12007 @node Automatically
12008 @subsection Having @value{GDBN} Infer the Source Language
12010 To have @value{GDBN} set the working language automatically, use
12011 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12012 then infers the working language. That is, when your program stops in a
12013 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12014 working language to the language recorded for the function in that
12015 frame. If the language for a frame is unknown (that is, if the function
12016 or block corresponding to the frame was defined in a source file that
12017 does not have a recognized extension), the current working language is
12018 not changed, and @value{GDBN} issues a warning.
12020 This may not seem necessary for most programs, which are written
12021 entirely in one source language. However, program modules and libraries
12022 written in one source language can be used by a main program written in
12023 a different source language. Using @samp{set language auto} in this
12024 case frees you from having to set the working language manually.
12027 @section Displaying the Language
12029 The following commands help you find out which language is the
12030 working language, and also what language source files were written in.
12033 @item show language
12034 @kindex show language
12035 Display the current working language. This is the
12036 language you can use with commands such as @code{print} to
12037 build and compute expressions that may involve variables in your program.
12040 @kindex info frame@r{, show the source language}
12041 Display the source language for this frame. This language becomes the
12042 working language if you use an identifier from this frame.
12043 @xref{Frame Info, ,Information about a Frame}, to identify the other
12044 information listed here.
12047 @kindex info source@r{, show the source language}
12048 Display the source language of this source file.
12049 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12050 information listed here.
12053 In unusual circumstances, you may have source files with extensions
12054 not in the standard list. You can then set the extension associated
12055 with a language explicitly:
12058 @item set extension-language @var{ext} @var{language}
12059 @kindex set extension-language
12060 Tell @value{GDBN} that source files with extension @var{ext} are to be
12061 assumed as written in the source language @var{language}.
12063 @item info extensions
12064 @kindex info extensions
12065 List all the filename extensions and the associated languages.
12069 @section Type and Range Checking
12072 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12073 checking are included, but they do not yet have any effect. This
12074 section documents the intended facilities.
12076 @c FIXME remove warning when type/range code added
12078 Some languages are designed to guard you against making seemingly common
12079 errors through a series of compile- and run-time checks. These include
12080 checking the type of arguments to functions and operators, and making
12081 sure mathematical overflows are caught at run time. Checks such as
12082 these help to ensure a program's correctness once it has been compiled
12083 by eliminating type mismatches, and providing active checks for range
12084 errors when your program is running.
12086 @value{GDBN} can check for conditions like the above if you wish.
12087 Although @value{GDBN} does not check the statements in your program,
12088 it can check expressions entered directly into @value{GDBN} for
12089 evaluation via the @code{print} command, for example. As with the
12090 working language, @value{GDBN} can also decide whether or not to check
12091 automatically based on your program's source language.
12092 @xref{Supported Languages, ,Supported Languages}, for the default
12093 settings of supported languages.
12096 * Type Checking:: An overview of type checking
12097 * Range Checking:: An overview of range checking
12100 @cindex type checking
12101 @cindex checks, type
12102 @node Type Checking
12103 @subsection An Overview of Type Checking
12105 Some languages, such as Modula-2, are strongly typed, meaning that the
12106 arguments to operators and functions have to be of the correct type,
12107 otherwise an error occurs. These checks prevent type mismatch
12108 errors from ever causing any run-time problems. For example,
12116 The second example fails because the @code{CARDINAL} 1 is not
12117 type-compatible with the @code{REAL} 2.3.
12119 For the expressions you use in @value{GDBN} commands, you can tell the
12120 @value{GDBN} type checker to skip checking;
12121 to treat any mismatches as errors and abandon the expression;
12122 or to only issue warnings when type mismatches occur,
12123 but evaluate the expression anyway. When you choose the last of
12124 these, @value{GDBN} evaluates expressions like the second example above, but
12125 also issues a warning.
12127 Even if you turn type checking off, there may be other reasons
12128 related to type that prevent @value{GDBN} from evaluating an expression.
12129 For instance, @value{GDBN} does not know how to add an @code{int} and
12130 a @code{struct foo}. These particular type errors have nothing to do
12131 with the language in use, and usually arise from expressions, such as
12132 the one described above, which make little sense to evaluate anyway.
12134 Each language defines to what degree it is strict about type. For
12135 instance, both Modula-2 and C require the arguments to arithmetical
12136 operators to be numbers. In C, enumerated types and pointers can be
12137 represented as numbers, so that they are valid arguments to mathematical
12138 operators. @xref{Supported Languages, ,Supported Languages}, for further
12139 details on specific languages.
12141 @value{GDBN} provides some additional commands for controlling the type checker:
12143 @kindex set check type
12144 @kindex show check type
12146 @item set check type auto
12147 Set type checking on or off based on the current working language.
12148 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12151 @item set check type on
12152 @itemx set check type off
12153 Set type checking on or off, overriding the default setting for the
12154 current working language. Issue a warning if the setting does not
12155 match the language default. If any type mismatches occur in
12156 evaluating an expression while type checking is on, @value{GDBN} prints a
12157 message and aborts evaluation of the expression.
12159 @item set check type warn
12160 Cause the type checker to issue warnings, but to always attempt to
12161 evaluate the expression. Evaluating the expression may still
12162 be impossible for other reasons. For example, @value{GDBN} cannot add
12163 numbers and structures.
12166 Show the current setting of the type checker, and whether or not @value{GDBN}
12167 is setting it automatically.
12170 @cindex range checking
12171 @cindex checks, range
12172 @node Range Checking
12173 @subsection An Overview of Range Checking
12175 In some languages (such as Modula-2), it is an error to exceed the
12176 bounds of a type; this is enforced with run-time checks. Such range
12177 checking is meant to ensure program correctness by making sure
12178 computations do not overflow, or indices on an array element access do
12179 not exceed the bounds of the array.
12181 For expressions you use in @value{GDBN} commands, you can tell
12182 @value{GDBN} to treat range errors in one of three ways: ignore them,
12183 always treat them as errors and abandon the expression, or issue
12184 warnings but evaluate the expression anyway.
12186 A range error can result from numerical overflow, from exceeding an
12187 array index bound, or when you type a constant that is not a member
12188 of any type. Some languages, however, do not treat overflows as an
12189 error. In many implementations of C, mathematical overflow causes the
12190 result to ``wrap around'' to lower values---for example, if @var{m} is
12191 the largest integer value, and @var{s} is the smallest, then
12194 @var{m} + 1 @result{} @var{s}
12197 This, too, is specific to individual languages, and in some cases
12198 specific to individual compilers or machines. @xref{Supported Languages, ,
12199 Supported Languages}, for further details on specific languages.
12201 @value{GDBN} provides some additional commands for controlling the range checker:
12203 @kindex set check range
12204 @kindex show check range
12206 @item set check range auto
12207 Set range checking on or off based on the current working language.
12208 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12211 @item set check range on
12212 @itemx set check range off
12213 Set range checking on or off, overriding the default setting for the
12214 current working language. A warning is issued if the setting does not
12215 match the language default. If a range error occurs and range checking is on,
12216 then a message is printed and evaluation of the expression is aborted.
12218 @item set check range warn
12219 Output messages when the @value{GDBN} range checker detects a range error,
12220 but attempt to evaluate the expression anyway. Evaluating the
12221 expression may still be impossible for other reasons, such as accessing
12222 memory that the process does not own (a typical example from many Unix
12226 Show the current setting of the range checker, and whether or not it is
12227 being set automatically by @value{GDBN}.
12230 @node Supported Languages
12231 @section Supported Languages
12233 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12234 assembly, Modula-2, and Ada.
12235 @c This is false ...
12236 Some @value{GDBN} features may be used in expressions regardless of the
12237 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12238 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12239 ,Expressions}) can be used with the constructs of any supported
12242 The following sections detail to what degree each source language is
12243 supported by @value{GDBN}. These sections are not meant to be language
12244 tutorials or references, but serve only as a reference guide to what the
12245 @value{GDBN} expression parser accepts, and what input and output
12246 formats should look like for different languages. There are many good
12247 books written on each of these languages; please look to these for a
12248 language reference or tutorial.
12251 * C:: C and C@t{++}
12253 * Objective-C:: Objective-C
12254 * OpenCL C:: OpenCL C
12255 * Fortran:: Fortran
12257 * Modula-2:: Modula-2
12262 @subsection C and C@t{++}
12264 @cindex C and C@t{++}
12265 @cindex expressions in C or C@t{++}
12267 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12268 to both languages. Whenever this is the case, we discuss those languages
12272 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12273 @cindex @sc{gnu} C@t{++}
12274 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12275 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12276 effectively, you must compile your C@t{++} programs with a supported
12277 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12278 compiler (@code{aCC}).
12281 * C Operators:: C and C@t{++} operators
12282 * C Constants:: C and C@t{++} constants
12283 * C Plus Plus Expressions:: C@t{++} expressions
12284 * C Defaults:: Default settings for C and C@t{++}
12285 * C Checks:: C and C@t{++} type and range checks
12286 * Debugging C:: @value{GDBN} and C
12287 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12288 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12292 @subsubsection C and C@t{++} Operators
12294 @cindex C and C@t{++} operators
12296 Operators must be defined on values of specific types. For instance,
12297 @code{+} is defined on numbers, but not on structures. Operators are
12298 often defined on groups of types.
12300 For the purposes of C and C@t{++}, the following definitions hold:
12305 @emph{Integral types} include @code{int} with any of its storage-class
12306 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12309 @emph{Floating-point types} include @code{float}, @code{double}, and
12310 @code{long double} (if supported by the target platform).
12313 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12316 @emph{Scalar types} include all of the above.
12321 The following operators are supported. They are listed here
12322 in order of increasing precedence:
12326 The comma or sequencing operator. Expressions in a comma-separated list
12327 are evaluated from left to right, with the result of the entire
12328 expression being the last expression evaluated.
12331 Assignment. The value of an assignment expression is the value
12332 assigned. Defined on scalar types.
12335 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12336 and translated to @w{@code{@var{a} = @var{a op b}}}.
12337 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12338 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12339 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12342 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12343 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12347 Logical @sc{or}. Defined on integral types.
12350 Logical @sc{and}. Defined on integral types.
12353 Bitwise @sc{or}. Defined on integral types.
12356 Bitwise exclusive-@sc{or}. Defined on integral types.
12359 Bitwise @sc{and}. Defined on integral types.
12362 Equality and inequality. Defined on scalar types. The value of these
12363 expressions is 0 for false and non-zero for true.
12365 @item <@r{, }>@r{, }<=@r{, }>=
12366 Less than, greater than, less than or equal, greater than or equal.
12367 Defined on scalar types. The value of these expressions is 0 for false
12368 and non-zero for true.
12371 left shift, and right shift. Defined on integral types.
12374 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12377 Addition and subtraction. Defined on integral types, floating-point types and
12380 @item *@r{, }/@r{, }%
12381 Multiplication, division, and modulus. Multiplication and division are
12382 defined on integral and floating-point types. Modulus is defined on
12386 Increment and decrement. When appearing before a variable, the
12387 operation is performed before the variable is used in an expression;
12388 when appearing after it, the variable's value is used before the
12389 operation takes place.
12392 Pointer dereferencing. Defined on pointer types. Same precedence as
12396 Address operator. Defined on variables. Same precedence as @code{++}.
12398 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12399 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12400 to examine the address
12401 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12405 Negative. Defined on integral and floating-point types. Same
12406 precedence as @code{++}.
12409 Logical negation. Defined on integral types. Same precedence as
12413 Bitwise complement operator. Defined on integral types. Same precedence as
12418 Structure member, and pointer-to-structure member. For convenience,
12419 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12420 pointer based on the stored type information.
12421 Defined on @code{struct} and @code{union} data.
12424 Dereferences of pointers to members.
12427 Array indexing. @code{@var{a}[@var{i}]} is defined as
12428 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12431 Function parameter list. Same precedence as @code{->}.
12434 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12435 and @code{class} types.
12438 Doubled colons also represent the @value{GDBN} scope operator
12439 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12443 If an operator is redefined in the user code, @value{GDBN} usually
12444 attempts to invoke the redefined version instead of using the operator's
12445 predefined meaning.
12448 @subsubsection C and C@t{++} Constants
12450 @cindex C and C@t{++} constants
12452 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12457 Integer constants are a sequence of digits. Octal constants are
12458 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12459 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12460 @samp{l}, specifying that the constant should be treated as a
12464 Floating point constants are a sequence of digits, followed by a decimal
12465 point, followed by a sequence of digits, and optionally followed by an
12466 exponent. An exponent is of the form:
12467 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12468 sequence of digits. The @samp{+} is optional for positive exponents.
12469 A floating-point constant may also end with a letter @samp{f} or
12470 @samp{F}, specifying that the constant should be treated as being of
12471 the @code{float} (as opposed to the default @code{double}) type; or with
12472 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12476 Enumerated constants consist of enumerated identifiers, or their
12477 integral equivalents.
12480 Character constants are a single character surrounded by single quotes
12481 (@code{'}), or a number---the ordinal value of the corresponding character
12482 (usually its @sc{ascii} value). Within quotes, the single character may
12483 be represented by a letter or by @dfn{escape sequences}, which are of
12484 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12485 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12486 @samp{@var{x}} is a predefined special character---for example,
12487 @samp{\n} for newline.
12489 Wide character constants can be written by prefixing a character
12490 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12491 form of @samp{x}. The target wide character set is used when
12492 computing the value of this constant (@pxref{Character Sets}).
12495 String constants are a sequence of character constants surrounded by
12496 double quotes (@code{"}). Any valid character constant (as described
12497 above) may appear. Double quotes within the string must be preceded by
12498 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12501 Wide string constants can be written by prefixing a string constant
12502 with @samp{L}, as in C. The target wide character set is used when
12503 computing the value of this constant (@pxref{Character Sets}).
12506 Pointer constants are an integral value. You can also write pointers
12507 to constants using the C operator @samp{&}.
12510 Array constants are comma-separated lists surrounded by braces @samp{@{}
12511 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12512 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12513 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12516 @node C Plus Plus Expressions
12517 @subsubsection C@t{++} Expressions
12519 @cindex expressions in C@t{++}
12520 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12522 @cindex debugging C@t{++} programs
12523 @cindex C@t{++} compilers
12524 @cindex debug formats and C@t{++}
12525 @cindex @value{NGCC} and C@t{++}
12527 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12528 the proper compiler and the proper debug format. Currently,
12529 @value{GDBN} works best when debugging C@t{++} code that is compiled
12530 with the most recent version of @value{NGCC} possible. The DWARF
12531 debugging format is preferred; @value{NGCC} defaults to this on most
12532 popular platforms. Other compilers and/or debug formats are likely to
12533 work badly or not at all when using @value{GDBN} to debug C@t{++}
12534 code. @xref{Compilation}.
12539 @cindex member functions
12541 Member function calls are allowed; you can use expressions like
12544 count = aml->GetOriginal(x, y)
12547 @vindex this@r{, inside C@t{++} member functions}
12548 @cindex namespace in C@t{++}
12550 While a member function is active (in the selected stack frame), your
12551 expressions have the same namespace available as the member function;
12552 that is, @value{GDBN} allows implicit references to the class instance
12553 pointer @code{this} following the same rules as C@t{++}. @code{using}
12554 declarations in the current scope are also respected by @value{GDBN}.
12556 @cindex call overloaded functions
12557 @cindex overloaded functions, calling
12558 @cindex type conversions in C@t{++}
12560 You can call overloaded functions; @value{GDBN} resolves the function
12561 call to the right definition, with some restrictions. @value{GDBN} does not
12562 perform overload resolution involving user-defined type conversions,
12563 calls to constructors, or instantiations of templates that do not exist
12564 in the program. It also cannot handle ellipsis argument lists or
12567 It does perform integral conversions and promotions, floating-point
12568 promotions, arithmetic conversions, pointer conversions, conversions of
12569 class objects to base classes, and standard conversions such as those of
12570 functions or arrays to pointers; it requires an exact match on the
12571 number of function arguments.
12573 Overload resolution is always performed, unless you have specified
12574 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12575 ,@value{GDBN} Features for C@t{++}}.
12577 You must specify @code{set overload-resolution off} in order to use an
12578 explicit function signature to call an overloaded function, as in
12580 p 'foo(char,int)'('x', 13)
12583 The @value{GDBN} command-completion facility can simplify this;
12584 see @ref{Completion, ,Command Completion}.
12586 @cindex reference declarations
12588 @value{GDBN} understands variables declared as C@t{++} references; you can use
12589 them in expressions just as you do in C@t{++} source---they are automatically
12592 In the parameter list shown when @value{GDBN} displays a frame, the values of
12593 reference variables are not displayed (unlike other variables); this
12594 avoids clutter, since references are often used for large structures.
12595 The @emph{address} of a reference variable is always shown, unless
12596 you have specified @samp{set print address off}.
12599 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12600 expressions can use it just as expressions in your program do. Since
12601 one scope may be defined in another, you can use @code{::} repeatedly if
12602 necessary, for example in an expression like
12603 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12604 resolving name scope by reference to source files, in both C and C@t{++}
12605 debugging (@pxref{Variables, ,Program Variables}).
12608 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12613 @subsubsection C and C@t{++} Defaults
12615 @cindex C and C@t{++} defaults
12617 If you allow @value{GDBN} to set type and range checking automatically, they
12618 both default to @code{off} whenever the working language changes to
12619 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12620 selects the working language.
12622 If you allow @value{GDBN} to set the language automatically, it
12623 recognizes source files whose names end with @file{.c}, @file{.C}, or
12624 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12625 these files, it sets the working language to C or C@t{++}.
12626 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12627 for further details.
12629 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12630 @c unimplemented. If (b) changes, it might make sense to let this node
12631 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12634 @subsubsection C and C@t{++} Type and Range Checks
12636 @cindex C and C@t{++} checks
12638 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12639 is not used. However, if you turn type checking on, @value{GDBN}
12640 considers two variables type equivalent if:
12644 The two variables are structured and have the same structure, union, or
12648 The two variables have the same type name, or types that have been
12649 declared equivalent through @code{typedef}.
12652 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12655 The two @code{struct}, @code{union}, or @code{enum} variables are
12656 declared in the same declaration. (Note: this may not be true for all C
12661 Range checking, if turned on, is done on mathematical operations. Array
12662 indices are not checked, since they are often used to index a pointer
12663 that is not itself an array.
12666 @subsubsection @value{GDBN} and C
12668 The @code{set print union} and @code{show print union} commands apply to
12669 the @code{union} type. When set to @samp{on}, any @code{union} that is
12670 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12671 appears as @samp{@{...@}}.
12673 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12674 with pointers and a memory allocation function. @xref{Expressions,
12677 @node Debugging C Plus Plus
12678 @subsubsection @value{GDBN} Features for C@t{++}
12680 @cindex commands for C@t{++}
12682 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12683 designed specifically for use with C@t{++}. Here is a summary:
12686 @cindex break in overloaded functions
12687 @item @r{breakpoint menus}
12688 When you want a breakpoint in a function whose name is overloaded,
12689 @value{GDBN} has the capability to display a menu of possible breakpoint
12690 locations to help you specify which function definition you want.
12691 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12693 @cindex overloading in C@t{++}
12694 @item rbreak @var{regex}
12695 Setting breakpoints using regular expressions is helpful for setting
12696 breakpoints on overloaded functions that are not members of any special
12698 @xref{Set Breaks, ,Setting Breakpoints}.
12700 @cindex C@t{++} exception handling
12703 Debug C@t{++} exception handling using these commands. @xref{Set
12704 Catchpoints, , Setting Catchpoints}.
12706 @cindex inheritance
12707 @item ptype @var{typename}
12708 Print inheritance relationships as well as other information for type
12710 @xref{Symbols, ,Examining the Symbol Table}.
12712 @cindex C@t{++} symbol display
12713 @item set print demangle
12714 @itemx show print demangle
12715 @itemx set print asm-demangle
12716 @itemx show print asm-demangle
12717 Control whether C@t{++} symbols display in their source form, both when
12718 displaying code as C@t{++} source and when displaying disassemblies.
12719 @xref{Print Settings, ,Print Settings}.
12721 @item set print object
12722 @itemx show print object
12723 Choose whether to print derived (actual) or declared types of objects.
12724 @xref{Print Settings, ,Print Settings}.
12726 @item set print vtbl
12727 @itemx show print vtbl
12728 Control the format for printing virtual function tables.
12729 @xref{Print Settings, ,Print Settings}.
12730 (The @code{vtbl} commands do not work on programs compiled with the HP
12731 ANSI C@t{++} compiler (@code{aCC}).)
12733 @kindex set overload-resolution
12734 @cindex overloaded functions, overload resolution
12735 @item set overload-resolution on
12736 Enable overload resolution for C@t{++} expression evaluation. The default
12737 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12738 and searches for a function whose signature matches the argument types,
12739 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12740 Expressions, ,C@t{++} Expressions}, for details).
12741 If it cannot find a match, it emits a message.
12743 @item set overload-resolution off
12744 Disable overload resolution for C@t{++} expression evaluation. For
12745 overloaded functions that are not class member functions, @value{GDBN}
12746 chooses the first function of the specified name that it finds in the
12747 symbol table, whether or not its arguments are of the correct type. For
12748 overloaded functions that are class member functions, @value{GDBN}
12749 searches for a function whose signature @emph{exactly} matches the
12752 @kindex show overload-resolution
12753 @item show overload-resolution
12754 Show the current setting of overload resolution.
12756 @item @r{Overloaded symbol names}
12757 You can specify a particular definition of an overloaded symbol, using
12758 the same notation that is used to declare such symbols in C@t{++}: type
12759 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12760 also use the @value{GDBN} command-line word completion facilities to list the
12761 available choices, or to finish the type list for you.
12762 @xref{Completion,, Command Completion}, for details on how to do this.
12765 @node Decimal Floating Point
12766 @subsubsection Decimal Floating Point format
12767 @cindex decimal floating point format
12769 @value{GDBN} can examine, set and perform computations with numbers in
12770 decimal floating point format, which in the C language correspond to the
12771 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12772 specified by the extension to support decimal floating-point arithmetic.
12774 There are two encodings in use, depending on the architecture: BID (Binary
12775 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12776 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12779 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12780 to manipulate decimal floating point numbers, it is not possible to convert
12781 (using a cast, for example) integers wider than 32-bit to decimal float.
12783 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12784 point computations, error checking in decimal float operations ignores
12785 underflow, overflow and divide by zero exceptions.
12787 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12788 to inspect @code{_Decimal128} values stored in floating point registers.
12789 See @ref{PowerPC,,PowerPC} for more details.
12795 @value{GDBN} can be used to debug programs written in D and compiled with
12796 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12797 specific feature --- dynamic arrays.
12800 @subsection Objective-C
12802 @cindex Objective-C
12803 This section provides information about some commands and command
12804 options that are useful for debugging Objective-C code. See also
12805 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12806 few more commands specific to Objective-C support.
12809 * Method Names in Commands::
12810 * The Print Command with Objective-C::
12813 @node Method Names in Commands
12814 @subsubsection Method Names in Commands
12816 The following commands have been extended to accept Objective-C method
12817 names as line specifications:
12819 @kindex clear@r{, and Objective-C}
12820 @kindex break@r{, and Objective-C}
12821 @kindex info line@r{, and Objective-C}
12822 @kindex jump@r{, and Objective-C}
12823 @kindex list@r{, and Objective-C}
12827 @item @code{info line}
12832 A fully qualified Objective-C method name is specified as
12835 -[@var{Class} @var{methodName}]
12838 where the minus sign is used to indicate an instance method and a
12839 plus sign (not shown) is used to indicate a class method. The class
12840 name @var{Class} and method name @var{methodName} are enclosed in
12841 brackets, similar to the way messages are specified in Objective-C
12842 source code. For example, to set a breakpoint at the @code{create}
12843 instance method of class @code{Fruit} in the program currently being
12847 break -[Fruit create]
12850 To list ten program lines around the @code{initialize} class method,
12854 list +[NSText initialize]
12857 In the current version of @value{GDBN}, the plus or minus sign is
12858 required. In future versions of @value{GDBN}, the plus or minus
12859 sign will be optional, but you can use it to narrow the search. It
12860 is also possible to specify just a method name:
12866 You must specify the complete method name, including any colons. If
12867 your program's source files contain more than one @code{create} method,
12868 you'll be presented with a numbered list of classes that implement that
12869 method. Indicate your choice by number, or type @samp{0} to exit if
12872 As another example, to clear a breakpoint established at the
12873 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12876 clear -[NSWindow makeKeyAndOrderFront:]
12879 @node The Print Command with Objective-C
12880 @subsubsection The Print Command With Objective-C
12881 @cindex Objective-C, print objects
12882 @kindex print-object
12883 @kindex po @r{(@code{print-object})}
12885 The print command has also been extended to accept methods. For example:
12888 print -[@var{object} hash]
12891 @cindex print an Objective-C object description
12892 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12894 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12895 and print the result. Also, an additional command has been added,
12896 @code{print-object} or @code{po} for short, which is meant to print
12897 the description of an object. However, this command may only work
12898 with certain Objective-C libraries that have a particular hook
12899 function, @code{_NSPrintForDebugger}, defined.
12902 @subsection OpenCL C
12905 This section provides information about @value{GDBN}s OpenCL C support.
12908 * OpenCL C Datatypes::
12909 * OpenCL C Expressions::
12910 * OpenCL C Operators::
12913 @node OpenCL C Datatypes
12914 @subsubsection OpenCL C Datatypes
12916 @cindex OpenCL C Datatypes
12917 @value{GDBN} supports the builtin scalar and vector datatypes specified
12918 by OpenCL 1.1. In addition the half- and double-precision floating point
12919 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12920 extensions are also known to @value{GDBN}.
12922 @node OpenCL C Expressions
12923 @subsubsection OpenCL C Expressions
12925 @cindex OpenCL C Expressions
12926 @value{GDBN} supports accesses to vector components including the access as
12927 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12928 supported by @value{GDBN} can be used as well.
12930 @node OpenCL C Operators
12931 @subsubsection OpenCL C Operators
12933 @cindex OpenCL C Operators
12934 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12938 @subsection Fortran
12939 @cindex Fortran-specific support in @value{GDBN}
12941 @value{GDBN} can be used to debug programs written in Fortran, but it
12942 currently supports only the features of Fortran 77 language.
12944 @cindex trailing underscore, in Fortran symbols
12945 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12946 among them) append an underscore to the names of variables and
12947 functions. When you debug programs compiled by those compilers, you
12948 will need to refer to variables and functions with a trailing
12952 * Fortran Operators:: Fortran operators and expressions
12953 * Fortran Defaults:: Default settings for Fortran
12954 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12957 @node Fortran Operators
12958 @subsubsection Fortran Operators and Expressions
12960 @cindex Fortran operators and expressions
12962 Operators must be defined on values of specific types. For instance,
12963 @code{+} is defined on numbers, but not on characters or other non-
12964 arithmetic types. Operators are often defined on groups of types.
12968 The exponentiation operator. It raises the first operand to the power
12972 The range operator. Normally used in the form of array(low:high) to
12973 represent a section of array.
12976 The access component operator. Normally used to access elements in derived
12977 types. Also suitable for unions. As unions aren't part of regular Fortran,
12978 this can only happen when accessing a register that uses a gdbarch-defined
12982 @node Fortran Defaults
12983 @subsubsection Fortran Defaults
12985 @cindex Fortran Defaults
12987 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12988 default uses case-insensitive matches for Fortran symbols. You can
12989 change that with the @samp{set case-insensitive} command, see
12990 @ref{Symbols}, for the details.
12992 @node Special Fortran Commands
12993 @subsubsection Special Fortran Commands
12995 @cindex Special Fortran commands
12997 @value{GDBN} has some commands to support Fortran-specific features,
12998 such as displaying common blocks.
13001 @cindex @code{COMMON} blocks, Fortran
13002 @kindex info common
13003 @item info common @r{[}@var{common-name}@r{]}
13004 This command prints the values contained in the Fortran @code{COMMON}
13005 block whose name is @var{common-name}. With no argument, the names of
13006 all @code{COMMON} blocks visible at the current program location are
13013 @cindex Pascal support in @value{GDBN}, limitations
13014 Debugging Pascal programs which use sets, subranges, file variables, or
13015 nested functions does not currently work. @value{GDBN} does not support
13016 entering expressions, printing values, or similar features using Pascal
13019 The Pascal-specific command @code{set print pascal_static-members}
13020 controls whether static members of Pascal objects are displayed.
13021 @xref{Print Settings, pascal_static-members}.
13024 @subsection Modula-2
13026 @cindex Modula-2, @value{GDBN} support
13028 The extensions made to @value{GDBN} to support Modula-2 only support
13029 output from the @sc{gnu} Modula-2 compiler (which is currently being
13030 developed). Other Modula-2 compilers are not currently supported, and
13031 attempting to debug executables produced by them is most likely
13032 to give an error as @value{GDBN} reads in the executable's symbol
13035 @cindex expressions in Modula-2
13037 * M2 Operators:: Built-in operators
13038 * Built-In Func/Proc:: Built-in functions and procedures
13039 * M2 Constants:: Modula-2 constants
13040 * M2 Types:: Modula-2 types
13041 * M2 Defaults:: Default settings for Modula-2
13042 * Deviations:: Deviations from standard Modula-2
13043 * M2 Checks:: Modula-2 type and range checks
13044 * M2 Scope:: The scope operators @code{::} and @code{.}
13045 * GDB/M2:: @value{GDBN} and Modula-2
13049 @subsubsection Operators
13050 @cindex Modula-2 operators
13052 Operators must be defined on values of specific types. For instance,
13053 @code{+} is defined on numbers, but not on structures. Operators are
13054 often defined on groups of types. For the purposes of Modula-2, the
13055 following definitions hold:
13060 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13064 @emph{Character types} consist of @code{CHAR} and its subranges.
13067 @emph{Floating-point types} consist of @code{REAL}.
13070 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13074 @emph{Scalar types} consist of all of the above.
13077 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13080 @emph{Boolean types} consist of @code{BOOLEAN}.
13084 The following operators are supported, and appear in order of
13085 increasing precedence:
13089 Function argument or array index separator.
13092 Assignment. The value of @var{var} @code{:=} @var{value} is
13096 Less than, greater than on integral, floating-point, or enumerated
13100 Less than or equal to, greater than or equal to
13101 on integral, floating-point and enumerated types, or set inclusion on
13102 set types. Same precedence as @code{<}.
13104 @item =@r{, }<>@r{, }#
13105 Equality and two ways of expressing inequality, valid on scalar types.
13106 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13107 available for inequality, since @code{#} conflicts with the script
13111 Set membership. Defined on set types and the types of their members.
13112 Same precedence as @code{<}.
13115 Boolean disjunction. Defined on boolean types.
13118 Boolean conjunction. Defined on boolean types.
13121 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13124 Addition and subtraction on integral and floating-point types, or union
13125 and difference on set types.
13128 Multiplication on integral and floating-point types, or set intersection
13132 Division on floating-point types, or symmetric set difference on set
13133 types. Same precedence as @code{*}.
13136 Integer division and remainder. Defined on integral types. Same
13137 precedence as @code{*}.
13140 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13143 Pointer dereferencing. Defined on pointer types.
13146 Boolean negation. Defined on boolean types. Same precedence as
13150 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13151 precedence as @code{^}.
13154 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13157 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13161 @value{GDBN} and Modula-2 scope operators.
13165 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13166 treats the use of the operator @code{IN}, or the use of operators
13167 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13168 @code{<=}, and @code{>=} on sets as an error.
13172 @node Built-In Func/Proc
13173 @subsubsection Built-in Functions and Procedures
13174 @cindex Modula-2 built-ins
13176 Modula-2 also makes available several built-in procedures and functions.
13177 In describing these, the following metavariables are used:
13182 represents an @code{ARRAY} variable.
13185 represents a @code{CHAR} constant or variable.
13188 represents a variable or constant of integral type.
13191 represents an identifier that belongs to a set. Generally used in the
13192 same function with the metavariable @var{s}. The type of @var{s} should
13193 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13196 represents a variable or constant of integral or floating-point type.
13199 represents a variable or constant of floating-point type.
13205 represents a variable.
13208 represents a variable or constant of one of many types. See the
13209 explanation of the function for details.
13212 All Modula-2 built-in procedures also return a result, described below.
13216 Returns the absolute value of @var{n}.
13219 If @var{c} is a lower case letter, it returns its upper case
13220 equivalent, otherwise it returns its argument.
13223 Returns the character whose ordinal value is @var{i}.
13226 Decrements the value in the variable @var{v} by one. Returns the new value.
13228 @item DEC(@var{v},@var{i})
13229 Decrements the value in the variable @var{v} by @var{i}. Returns the
13232 @item EXCL(@var{m},@var{s})
13233 Removes the element @var{m} from the set @var{s}. Returns the new
13236 @item FLOAT(@var{i})
13237 Returns the floating point equivalent of the integer @var{i}.
13239 @item HIGH(@var{a})
13240 Returns the index of the last member of @var{a}.
13243 Increments the value in the variable @var{v} by one. Returns the new value.
13245 @item INC(@var{v},@var{i})
13246 Increments the value in the variable @var{v} by @var{i}. Returns the
13249 @item INCL(@var{m},@var{s})
13250 Adds the element @var{m} to the set @var{s} if it is not already
13251 there. Returns the new set.
13254 Returns the maximum value of the type @var{t}.
13257 Returns the minimum value of the type @var{t}.
13260 Returns boolean TRUE if @var{i} is an odd number.
13263 Returns the ordinal value of its argument. For example, the ordinal
13264 value of a character is its @sc{ascii} value (on machines supporting the
13265 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13266 integral, character and enumerated types.
13268 @item SIZE(@var{x})
13269 Returns the size of its argument. @var{x} can be a variable or a type.
13271 @item TRUNC(@var{r})
13272 Returns the integral part of @var{r}.
13274 @item TSIZE(@var{x})
13275 Returns the size of its argument. @var{x} can be a variable or a type.
13277 @item VAL(@var{t},@var{i})
13278 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13282 @emph{Warning:} Sets and their operations are not yet supported, so
13283 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13287 @cindex Modula-2 constants
13289 @subsubsection Constants
13291 @value{GDBN} allows you to express the constants of Modula-2 in the following
13297 Integer constants are simply a sequence of digits. When used in an
13298 expression, a constant is interpreted to be type-compatible with the
13299 rest of the expression. Hexadecimal integers are specified by a
13300 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13303 Floating point constants appear as a sequence of digits, followed by a
13304 decimal point and another sequence of digits. An optional exponent can
13305 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13306 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13307 digits of the floating point constant must be valid decimal (base 10)
13311 Character constants consist of a single character enclosed by a pair of
13312 like quotes, either single (@code{'}) or double (@code{"}). They may
13313 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13314 followed by a @samp{C}.
13317 String constants consist of a sequence of characters enclosed by a
13318 pair of like quotes, either single (@code{'}) or double (@code{"}).
13319 Escape sequences in the style of C are also allowed. @xref{C
13320 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13324 Enumerated constants consist of an enumerated identifier.
13327 Boolean constants consist of the identifiers @code{TRUE} and
13331 Pointer constants consist of integral values only.
13334 Set constants are not yet supported.
13338 @subsubsection Modula-2 Types
13339 @cindex Modula-2 types
13341 Currently @value{GDBN} can print the following data types in Modula-2
13342 syntax: array types, record types, set types, pointer types, procedure
13343 types, enumerated types, subrange types and base types. You can also
13344 print the contents of variables declared using these type.
13345 This section gives a number of simple source code examples together with
13346 sample @value{GDBN} sessions.
13348 The first example contains the following section of code:
13357 and you can request @value{GDBN} to interrogate the type and value of
13358 @code{r} and @code{s}.
13361 (@value{GDBP}) print s
13363 (@value{GDBP}) ptype s
13365 (@value{GDBP}) print r
13367 (@value{GDBP}) ptype r
13372 Likewise if your source code declares @code{s} as:
13376 s: SET ['A'..'Z'] ;
13380 then you may query the type of @code{s} by:
13383 (@value{GDBP}) ptype s
13384 type = SET ['A'..'Z']
13388 Note that at present you cannot interactively manipulate set
13389 expressions using the debugger.
13391 The following example shows how you might declare an array in Modula-2
13392 and how you can interact with @value{GDBN} to print its type and contents:
13396 s: ARRAY [-10..10] OF CHAR ;
13400 (@value{GDBP}) ptype s
13401 ARRAY [-10..10] OF CHAR
13404 Note that the array handling is not yet complete and although the type
13405 is printed correctly, expression handling still assumes that all
13406 arrays have a lower bound of zero and not @code{-10} as in the example
13409 Here are some more type related Modula-2 examples:
13413 colour = (blue, red, yellow, green) ;
13414 t = [blue..yellow] ;
13422 The @value{GDBN} interaction shows how you can query the data type
13423 and value of a variable.
13426 (@value{GDBP}) print s
13428 (@value{GDBP}) ptype t
13429 type = [blue..yellow]
13433 In this example a Modula-2 array is declared and its contents
13434 displayed. Observe that the contents are written in the same way as
13435 their @code{C} counterparts.
13439 s: ARRAY [1..5] OF CARDINAL ;
13445 (@value{GDBP}) print s
13446 $1 = @{1, 0, 0, 0, 0@}
13447 (@value{GDBP}) ptype s
13448 type = ARRAY [1..5] OF CARDINAL
13451 The Modula-2 language interface to @value{GDBN} also understands
13452 pointer types as shown in this example:
13456 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13463 and you can request that @value{GDBN} describes the type of @code{s}.
13466 (@value{GDBP}) ptype s
13467 type = POINTER TO ARRAY [1..5] OF CARDINAL
13470 @value{GDBN} handles compound types as we can see in this example.
13471 Here we combine array types, record types, pointer types and subrange
13482 myarray = ARRAY myrange OF CARDINAL ;
13483 myrange = [-2..2] ;
13485 s: POINTER TO ARRAY myrange OF foo ;
13489 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13493 (@value{GDBP}) ptype s
13494 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13497 f3 : ARRAY [-2..2] OF CARDINAL;
13502 @subsubsection Modula-2 Defaults
13503 @cindex Modula-2 defaults
13505 If type and range checking are set automatically by @value{GDBN}, they
13506 both default to @code{on} whenever the working language changes to
13507 Modula-2. This happens regardless of whether you or @value{GDBN}
13508 selected the working language.
13510 If you allow @value{GDBN} to set the language automatically, then entering
13511 code compiled from a file whose name ends with @file{.mod} sets the
13512 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13513 Infer the Source Language}, for further details.
13516 @subsubsection Deviations from Standard Modula-2
13517 @cindex Modula-2, deviations from
13519 A few changes have been made to make Modula-2 programs easier to debug.
13520 This is done primarily via loosening its type strictness:
13524 Unlike in standard Modula-2, pointer constants can be formed by
13525 integers. This allows you to modify pointer variables during
13526 debugging. (In standard Modula-2, the actual address contained in a
13527 pointer variable is hidden from you; it can only be modified
13528 through direct assignment to another pointer variable or expression that
13529 returned a pointer.)
13532 C escape sequences can be used in strings and characters to represent
13533 non-printable characters. @value{GDBN} prints out strings with these
13534 escape sequences embedded. Single non-printable characters are
13535 printed using the @samp{CHR(@var{nnn})} format.
13538 The assignment operator (@code{:=}) returns the value of its right-hand
13542 All built-in procedures both modify @emph{and} return their argument.
13546 @subsubsection Modula-2 Type and Range Checks
13547 @cindex Modula-2 checks
13550 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13553 @c FIXME remove warning when type/range checks added
13555 @value{GDBN} considers two Modula-2 variables type equivalent if:
13559 They are of types that have been declared equivalent via a @code{TYPE
13560 @var{t1} = @var{t2}} statement
13563 They have been declared on the same line. (Note: This is true of the
13564 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13567 As long as type checking is enabled, any attempt to combine variables
13568 whose types are not equivalent is an error.
13570 Range checking is done on all mathematical operations, assignment, array
13571 index bounds, and all built-in functions and procedures.
13574 @subsubsection The Scope Operators @code{::} and @code{.}
13576 @cindex @code{.}, Modula-2 scope operator
13577 @cindex colon, doubled as scope operator
13579 @vindex colon-colon@r{, in Modula-2}
13580 @c Info cannot handle :: but TeX can.
13583 @vindex ::@r{, in Modula-2}
13586 There are a few subtle differences between the Modula-2 scope operator
13587 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13592 @var{module} . @var{id}
13593 @var{scope} :: @var{id}
13597 where @var{scope} is the name of a module or a procedure,
13598 @var{module} the name of a module, and @var{id} is any declared
13599 identifier within your program, except another module.
13601 Using the @code{::} operator makes @value{GDBN} search the scope
13602 specified by @var{scope} for the identifier @var{id}. If it is not
13603 found in the specified scope, then @value{GDBN} searches all scopes
13604 enclosing the one specified by @var{scope}.
13606 Using the @code{.} operator makes @value{GDBN} search the current scope for
13607 the identifier specified by @var{id} that was imported from the
13608 definition module specified by @var{module}. With this operator, it is
13609 an error if the identifier @var{id} was not imported from definition
13610 module @var{module}, or if @var{id} is not an identifier in
13614 @subsubsection @value{GDBN} and Modula-2
13616 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13617 Five subcommands of @code{set print} and @code{show print} apply
13618 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13619 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13620 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13621 analogue in Modula-2.
13623 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13624 with any language, is not useful with Modula-2. Its
13625 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13626 created in Modula-2 as they can in C or C@t{++}. However, because an
13627 address can be specified by an integral constant, the construct
13628 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13630 @cindex @code{#} in Modula-2
13631 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13632 interpreted as the beginning of a comment. Use @code{<>} instead.
13638 The extensions made to @value{GDBN} for Ada only support
13639 output from the @sc{gnu} Ada (GNAT) compiler.
13640 Other Ada compilers are not currently supported, and
13641 attempting to debug executables produced by them is most likely
13645 @cindex expressions in Ada
13647 * Ada Mode Intro:: General remarks on the Ada syntax
13648 and semantics supported by Ada mode
13650 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13651 * Additions to Ada:: Extensions of the Ada expression syntax.
13652 * Stopping Before Main Program:: Debugging the program during elaboration.
13653 * Ada Tasks:: Listing and setting breakpoints in tasks.
13654 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13655 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13657 * Ada Glitches:: Known peculiarities of Ada mode.
13660 @node Ada Mode Intro
13661 @subsubsection Introduction
13662 @cindex Ada mode, general
13664 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13665 syntax, with some extensions.
13666 The philosophy behind the design of this subset is
13670 That @value{GDBN} should provide basic literals and access to operations for
13671 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13672 leaving more sophisticated computations to subprograms written into the
13673 program (which therefore may be called from @value{GDBN}).
13676 That type safety and strict adherence to Ada language restrictions
13677 are not particularly important to the @value{GDBN} user.
13680 That brevity is important to the @value{GDBN} user.
13683 Thus, for brevity, the debugger acts as if all names declared in
13684 user-written packages are directly visible, even if they are not visible
13685 according to Ada rules, thus making it unnecessary to fully qualify most
13686 names with their packages, regardless of context. Where this causes
13687 ambiguity, @value{GDBN} asks the user's intent.
13689 The debugger will start in Ada mode if it detects an Ada main program.
13690 As for other languages, it will enter Ada mode when stopped in a program that
13691 was translated from an Ada source file.
13693 While in Ada mode, you may use `@t{--}' for comments. This is useful
13694 mostly for documenting command files. The standard @value{GDBN} comment
13695 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13696 middle (to allow based literals).
13698 The debugger supports limited overloading. Given a subprogram call in which
13699 the function symbol has multiple definitions, it will use the number of
13700 actual parameters and some information about their types to attempt to narrow
13701 the set of definitions. It also makes very limited use of context, preferring
13702 procedures to functions in the context of the @code{call} command, and
13703 functions to procedures elsewhere.
13705 @node Omissions from Ada
13706 @subsubsection Omissions from Ada
13707 @cindex Ada, omissions from
13709 Here are the notable omissions from the subset:
13713 Only a subset of the attributes are supported:
13717 @t{'First}, @t{'Last}, and @t{'Length}
13718 on array objects (not on types and subtypes).
13721 @t{'Min} and @t{'Max}.
13724 @t{'Pos} and @t{'Val}.
13730 @t{'Range} on array objects (not subtypes), but only as the right
13731 operand of the membership (@code{in}) operator.
13734 @t{'Access}, @t{'Unchecked_Access}, and
13735 @t{'Unrestricted_Access} (a GNAT extension).
13743 @code{Characters.Latin_1} are not available and
13744 concatenation is not implemented. Thus, escape characters in strings are
13745 not currently available.
13748 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13749 equality of representations. They will generally work correctly
13750 for strings and arrays whose elements have integer or enumeration types.
13751 They may not work correctly for arrays whose element
13752 types have user-defined equality, for arrays of real values
13753 (in particular, IEEE-conformant floating point, because of negative
13754 zeroes and NaNs), and for arrays whose elements contain unused bits with
13755 indeterminate values.
13758 The other component-by-component array operations (@code{and}, @code{or},
13759 @code{xor}, @code{not}, and relational tests other than equality)
13760 are not implemented.
13763 @cindex array aggregates (Ada)
13764 @cindex record aggregates (Ada)
13765 @cindex aggregates (Ada)
13766 There is limited support for array and record aggregates. They are
13767 permitted only on the right sides of assignments, as in these examples:
13770 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13771 (@value{GDBP}) set An_Array := (1, others => 0)
13772 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13773 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13774 (@value{GDBP}) set A_Record := (1, "Peter", True);
13775 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13779 discriminant's value by assigning an aggregate has an
13780 undefined effect if that discriminant is used within the record.
13781 However, you can first modify discriminants by directly assigning to
13782 them (which normally would not be allowed in Ada), and then performing an
13783 aggregate assignment. For example, given a variable @code{A_Rec}
13784 declared to have a type such as:
13787 type Rec (Len : Small_Integer := 0) is record
13789 Vals : IntArray (1 .. Len);
13793 you can assign a value with a different size of @code{Vals} with two
13797 (@value{GDBP}) set A_Rec.Len := 4
13798 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13801 As this example also illustrates, @value{GDBN} is very loose about the usual
13802 rules concerning aggregates. You may leave out some of the
13803 components of an array or record aggregate (such as the @code{Len}
13804 component in the assignment to @code{A_Rec} above); they will retain their
13805 original values upon assignment. You may freely use dynamic values as
13806 indices in component associations. You may even use overlapping or
13807 redundant component associations, although which component values are
13808 assigned in such cases is not defined.
13811 Calls to dispatching subprograms are not implemented.
13814 The overloading algorithm is much more limited (i.e., less selective)
13815 than that of real Ada. It makes only limited use of the context in
13816 which a subexpression appears to resolve its meaning, and it is much
13817 looser in its rules for allowing type matches. As a result, some
13818 function calls will be ambiguous, and the user will be asked to choose
13819 the proper resolution.
13822 The @code{new} operator is not implemented.
13825 Entry calls are not implemented.
13828 Aside from printing, arithmetic operations on the native VAX floating-point
13829 formats are not supported.
13832 It is not possible to slice a packed array.
13835 The names @code{True} and @code{False}, when not part of a qualified name,
13836 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13838 Should your program
13839 redefine these names in a package or procedure (at best a dubious practice),
13840 you will have to use fully qualified names to access their new definitions.
13843 @node Additions to Ada
13844 @subsubsection Additions to Ada
13845 @cindex Ada, deviations from
13847 As it does for other languages, @value{GDBN} makes certain generic
13848 extensions to Ada (@pxref{Expressions}):
13852 If the expression @var{E} is a variable residing in memory (typically
13853 a local variable or array element) and @var{N} is a positive integer,
13854 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13855 @var{N}-1 adjacent variables following it in memory as an array. In
13856 Ada, this operator is generally not necessary, since its prime use is
13857 in displaying parts of an array, and slicing will usually do this in
13858 Ada. However, there are occasional uses when debugging programs in
13859 which certain debugging information has been optimized away.
13862 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13863 appears in function or file @var{B}.'' When @var{B} is a file name,
13864 you must typically surround it in single quotes.
13867 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13868 @var{type} that appears at address @var{addr}.''
13871 A name starting with @samp{$} is a convenience variable
13872 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13875 In addition, @value{GDBN} provides a few other shortcuts and outright
13876 additions specific to Ada:
13880 The assignment statement is allowed as an expression, returning
13881 its right-hand operand as its value. Thus, you may enter
13884 (@value{GDBP}) set x := y + 3
13885 (@value{GDBP}) print A(tmp := y + 1)
13889 The semicolon is allowed as an ``operator,'' returning as its value
13890 the value of its right-hand operand.
13891 This allows, for example,
13892 complex conditional breaks:
13895 (@value{GDBP}) break f
13896 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13900 Rather than use catenation and symbolic character names to introduce special
13901 characters into strings, one may instead use a special bracket notation,
13902 which is also used to print strings. A sequence of characters of the form
13903 @samp{["@var{XX}"]} within a string or character literal denotes the
13904 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13905 sequence of characters @samp{["""]} also denotes a single quotation mark
13906 in strings. For example,
13908 "One line.["0a"]Next line.["0a"]"
13911 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13915 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13916 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13920 (@value{GDBP}) print 'max(x, y)
13924 When printing arrays, @value{GDBN} uses positional notation when the
13925 array has a lower bound of 1, and uses a modified named notation otherwise.
13926 For example, a one-dimensional array of three integers with a lower bound
13927 of 3 might print as
13934 That is, in contrast to valid Ada, only the first component has a @code{=>}
13938 You may abbreviate attributes in expressions with any unique,
13939 multi-character subsequence of
13940 their names (an exact match gets preference).
13941 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13942 in place of @t{a'length}.
13945 @cindex quoting Ada internal identifiers
13946 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13947 to lower case. The GNAT compiler uses upper-case characters for
13948 some of its internal identifiers, which are normally of no interest to users.
13949 For the rare occasions when you actually have to look at them,
13950 enclose them in angle brackets to avoid the lower-case mapping.
13953 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13957 Printing an object of class-wide type or dereferencing an
13958 access-to-class-wide value will display all the components of the object's
13959 specific type (as indicated by its run-time tag). Likewise, component
13960 selection on such a value will operate on the specific type of the
13965 @node Stopping Before Main Program
13966 @subsubsection Stopping at the Very Beginning
13968 @cindex breakpointing Ada elaboration code
13969 It is sometimes necessary to debug the program during elaboration, and
13970 before reaching the main procedure.
13971 As defined in the Ada Reference
13972 Manual, the elaboration code is invoked from a procedure called
13973 @code{adainit}. To run your program up to the beginning of
13974 elaboration, simply use the following two commands:
13975 @code{tbreak adainit} and @code{run}.
13978 @subsubsection Extensions for Ada Tasks
13979 @cindex Ada, tasking
13981 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13982 @value{GDBN} provides the following task-related commands:
13987 This command shows a list of current Ada tasks, as in the following example:
13994 (@value{GDBP}) info tasks
13995 ID TID P-ID Pri State Name
13996 1 8088000 0 15 Child Activation Wait main_task
13997 2 80a4000 1 15 Accept Statement b
13998 3 809a800 1 15 Child Activation Wait a
13999 * 4 80ae800 3 15 Runnable c
14004 In this listing, the asterisk before the last task indicates it to be the
14005 task currently being inspected.
14009 Represents @value{GDBN}'s internal task number.
14015 The parent's task ID (@value{GDBN}'s internal task number).
14018 The base priority of the task.
14021 Current state of the task.
14025 The task has been created but has not been activated. It cannot be
14029 The task is not blocked for any reason known to Ada. (It may be waiting
14030 for a mutex, though.) It is conceptually "executing" in normal mode.
14033 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14034 that were waiting on terminate alternatives have been awakened and have
14035 terminated themselves.
14037 @item Child Activation Wait
14038 The task is waiting for created tasks to complete activation.
14040 @item Accept Statement
14041 The task is waiting on an accept or selective wait statement.
14043 @item Waiting on entry call
14044 The task is waiting on an entry call.
14046 @item Async Select Wait
14047 The task is waiting to start the abortable part of an asynchronous
14051 The task is waiting on a select statement with only a delay
14054 @item Child Termination Wait
14055 The task is sleeping having completed a master within itself, and is
14056 waiting for the tasks dependent on that master to become terminated or
14057 waiting on a terminate Phase.
14059 @item Wait Child in Term Alt
14060 The task is sleeping waiting for tasks on terminate alternatives to
14061 finish terminating.
14063 @item Accepting RV with @var{taskno}
14064 The task is accepting a rendez-vous with the task @var{taskno}.
14068 Name of the task in the program.
14072 @kindex info task @var{taskno}
14073 @item info task @var{taskno}
14074 This command shows detailled informations on the specified task, as in
14075 the following example:
14080 (@value{GDBP}) info tasks
14081 ID TID P-ID Pri State Name
14082 1 8077880 0 15 Child Activation Wait main_task
14083 * 2 807c468 1 15 Runnable task_1
14084 (@value{GDBP}) info task 2
14085 Ada Task: 0x807c468
14088 Parent: 1 (main_task)
14094 @kindex task@r{ (Ada)}
14095 @cindex current Ada task ID
14096 This command prints the ID of the current task.
14102 (@value{GDBP}) info tasks
14103 ID TID P-ID Pri State Name
14104 1 8077870 0 15 Child Activation Wait main_task
14105 * 2 807c458 1 15 Runnable t
14106 (@value{GDBP}) task
14107 [Current task is 2]
14110 @item task @var{taskno}
14111 @cindex Ada task switching
14112 This command is like the @code{thread @var{threadno}}
14113 command (@pxref{Threads}). It switches the context of debugging
14114 from the current task to the given task.
14120 (@value{GDBP}) info tasks
14121 ID TID P-ID Pri State Name
14122 1 8077870 0 15 Child Activation Wait main_task
14123 * 2 807c458 1 15 Runnable t
14124 (@value{GDBP}) task 1
14125 [Switching to task 1]
14126 #0 0x8067726 in pthread_cond_wait ()
14128 #0 0x8067726 in pthread_cond_wait ()
14129 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14130 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14131 #3 0x806153e in system.tasking.stages.activate_tasks ()
14132 #4 0x804aacc in un () at un.adb:5
14135 @item break @var{linespec} task @var{taskno}
14136 @itemx break @var{linespec} task @var{taskno} if @dots{}
14137 @cindex breakpoints and tasks, in Ada
14138 @cindex task breakpoints, in Ada
14139 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14140 These commands are like the @code{break @dots{} thread @dots{}}
14141 command (@pxref{Thread Stops}).
14142 @var{linespec} specifies source lines, as described
14143 in @ref{Specify Location}.
14145 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14146 to specify that you only want @value{GDBN} to stop the program when a
14147 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14148 numeric task identifiers assigned by @value{GDBN}, shown in the first
14149 column of the @samp{info tasks} display.
14151 If you do not specify @samp{task @var{taskno}} when you set a
14152 breakpoint, the breakpoint applies to @emph{all} tasks of your
14155 You can use the @code{task} qualifier on conditional breakpoints as
14156 well; in this case, place @samp{task @var{taskno}} before the
14157 breakpoint condition (before the @code{if}).
14165 (@value{GDBP}) info tasks
14166 ID TID P-ID Pri State Name
14167 1 140022020 0 15 Child Activation Wait main_task
14168 2 140045060 1 15 Accept/Select Wait t2
14169 3 140044840 1 15 Runnable t1
14170 * 4 140056040 1 15 Runnable t3
14171 (@value{GDBP}) b 15 task 2
14172 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14173 (@value{GDBP}) cont
14178 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14180 (@value{GDBP}) info tasks
14181 ID TID P-ID Pri State Name
14182 1 140022020 0 15 Child Activation Wait main_task
14183 * 2 140045060 1 15 Runnable t2
14184 3 140044840 1 15 Runnable t1
14185 4 140056040 1 15 Delay Sleep t3
14189 @node Ada Tasks and Core Files
14190 @subsubsection Tasking Support when Debugging Core Files
14191 @cindex Ada tasking and core file debugging
14193 When inspecting a core file, as opposed to debugging a live program,
14194 tasking support may be limited or even unavailable, depending on
14195 the platform being used.
14196 For instance, on x86-linux, the list of tasks is available, but task
14197 switching is not supported. On Tru64, however, task switching will work
14200 On certain platforms, including Tru64, the debugger needs to perform some
14201 memory writes in order to provide Ada tasking support. When inspecting
14202 a core file, this means that the core file must be opened with read-write
14203 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14204 Under these circumstances, you should make a backup copy of the core
14205 file before inspecting it with @value{GDBN}.
14207 @node Ravenscar Profile
14208 @subsubsection Tasking Support when using the Ravenscar Profile
14209 @cindex Ravenscar Profile
14211 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14212 specifically designed for systems with safety-critical real-time
14216 @kindex set ravenscar task-switching on
14217 @cindex task switching with program using Ravenscar Profile
14218 @item set ravenscar task-switching on
14219 Allows task switching when debugging a program that uses the Ravenscar
14220 Profile. This is the default.
14222 @kindex set ravenscar task-switching off
14223 @item set ravenscar task-switching off
14224 Turn off task switching when debugging a program that uses the Ravenscar
14225 Profile. This is mostly intended to disable the code that adds support
14226 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14227 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14228 To be effective, this command should be run before the program is started.
14230 @kindex show ravenscar task-switching
14231 @item show ravenscar task-switching
14232 Show whether it is possible to switch from task to task in a program
14233 using the Ravenscar Profile.
14238 @subsubsection Known Peculiarities of Ada Mode
14239 @cindex Ada, problems
14241 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14242 we know of several problems with and limitations of Ada mode in
14244 some of which will be fixed with planned future releases of the debugger
14245 and the GNU Ada compiler.
14249 Static constants that the compiler chooses not to materialize as objects in
14250 storage are invisible to the debugger.
14253 Named parameter associations in function argument lists are ignored (the
14254 argument lists are treated as positional).
14257 Many useful library packages are currently invisible to the debugger.
14260 Fixed-point arithmetic, conversions, input, and output is carried out using
14261 floating-point arithmetic, and may give results that only approximate those on
14265 The GNAT compiler never generates the prefix @code{Standard} for any of
14266 the standard symbols defined by the Ada language. @value{GDBN} knows about
14267 this: it will strip the prefix from names when you use it, and will never
14268 look for a name you have so qualified among local symbols, nor match against
14269 symbols in other packages or subprograms. If you have
14270 defined entities anywhere in your program other than parameters and
14271 local variables whose simple names match names in @code{Standard},
14272 GNAT's lack of qualification here can cause confusion. When this happens,
14273 you can usually resolve the confusion
14274 by qualifying the problematic names with package
14275 @code{Standard} explicitly.
14278 Older versions of the compiler sometimes generate erroneous debugging
14279 information, resulting in the debugger incorrectly printing the value
14280 of affected entities. In some cases, the debugger is able to work
14281 around an issue automatically. In other cases, the debugger is able
14282 to work around the issue, but the work-around has to be specifically
14285 @kindex set ada trust-PAD-over-XVS
14286 @kindex show ada trust-PAD-over-XVS
14289 @item set ada trust-PAD-over-XVS on
14290 Configure GDB to strictly follow the GNAT encoding when computing the
14291 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14292 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14293 a complete description of the encoding used by the GNAT compiler).
14294 This is the default.
14296 @item set ada trust-PAD-over-XVS off
14297 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14298 sometimes prints the wrong value for certain entities, changing @code{ada
14299 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14300 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14301 @code{off}, but this incurs a slight performance penalty, so it is
14302 recommended to leave this setting to @code{on} unless necessary.
14306 @node Unsupported Languages
14307 @section Unsupported Languages
14309 @cindex unsupported languages
14310 @cindex minimal language
14311 In addition to the other fully-supported programming languages,
14312 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14313 It does not represent a real programming language, but provides a set
14314 of capabilities close to what the C or assembly languages provide.
14315 This should allow most simple operations to be performed while debugging
14316 an application that uses a language currently not supported by @value{GDBN}.
14318 If the language is set to @code{auto}, @value{GDBN} will automatically
14319 select this language if the current frame corresponds to an unsupported
14323 @chapter Examining the Symbol Table
14325 The commands described in this chapter allow you to inquire about the
14326 symbols (names of variables, functions and types) defined in your
14327 program. This information is inherent in the text of your program and
14328 does not change as your program executes. @value{GDBN} finds it in your
14329 program's symbol table, in the file indicated when you started @value{GDBN}
14330 (@pxref{File Options, ,Choosing Files}), or by one of the
14331 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14333 @cindex symbol names
14334 @cindex names of symbols
14335 @cindex quoting names
14336 Occasionally, you may need to refer to symbols that contain unusual
14337 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14338 most frequent case is in referring to static variables in other
14339 source files (@pxref{Variables,,Program Variables}). File names
14340 are recorded in object files as debugging symbols, but @value{GDBN} would
14341 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14342 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14343 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14350 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14353 @cindex case-insensitive symbol names
14354 @cindex case sensitivity in symbol names
14355 @kindex set case-sensitive
14356 @item set case-sensitive on
14357 @itemx set case-sensitive off
14358 @itemx set case-sensitive auto
14359 Normally, when @value{GDBN} looks up symbols, it matches their names
14360 with case sensitivity determined by the current source language.
14361 Occasionally, you may wish to control that. The command @code{set
14362 case-sensitive} lets you do that by specifying @code{on} for
14363 case-sensitive matches or @code{off} for case-insensitive ones. If
14364 you specify @code{auto}, case sensitivity is reset to the default
14365 suitable for the source language. The default is case-sensitive
14366 matches for all languages except for Fortran, for which the default is
14367 case-insensitive matches.
14369 @kindex show case-sensitive
14370 @item show case-sensitive
14371 This command shows the current setting of case sensitivity for symbols
14374 @kindex info address
14375 @cindex address of a symbol
14376 @item info address @var{symbol}
14377 Describe where the data for @var{symbol} is stored. For a register
14378 variable, this says which register it is kept in. For a non-register
14379 local variable, this prints the stack-frame offset at which the variable
14382 Note the contrast with @samp{print &@var{symbol}}, which does not work
14383 at all for a register variable, and for a stack local variable prints
14384 the exact address of the current instantiation of the variable.
14386 @kindex info symbol
14387 @cindex symbol from address
14388 @cindex closest symbol and offset for an address
14389 @item info symbol @var{addr}
14390 Print the name of a symbol which is stored at the address @var{addr}.
14391 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14392 nearest symbol and an offset from it:
14395 (@value{GDBP}) info symbol 0x54320
14396 _initialize_vx + 396 in section .text
14400 This is the opposite of the @code{info address} command. You can use
14401 it to find out the name of a variable or a function given its address.
14403 For dynamically linked executables, the name of executable or shared
14404 library containing the symbol is also printed:
14407 (@value{GDBP}) info symbol 0x400225
14408 _start + 5 in section .text of /tmp/a.out
14409 (@value{GDBP}) info symbol 0x2aaaac2811cf
14410 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14414 @item whatis [@var{arg}]
14415 Print the data type of @var{arg}, which can be either an expression
14416 or a name of a data type. With no argument, print the data type of
14417 @code{$}, the last value in the value history.
14419 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14420 is not actually evaluated, and any side-effecting operations (such as
14421 assignments or function calls) inside it do not take place.
14423 If @var{arg} is a variable or an expression, @code{whatis} prints its
14424 literal type as it is used in the source code. If the type was
14425 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14426 the data type underlying the @code{typedef}. If the type of the
14427 variable or the expression is a compound data type, such as
14428 @code{struct} or @code{class}, @code{whatis} never prints their
14429 fields or methods. It just prints the @code{struct}/@code{class}
14430 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14431 such a compound data type, use @code{ptype}.
14433 If @var{arg} is a type name that was defined using @code{typedef},
14434 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14435 Unrolling means that @code{whatis} will show the underlying type used
14436 in the @code{typedef} declaration of @var{arg}. However, if that
14437 underlying type is also a @code{typedef}, @code{whatis} will not
14440 For C code, the type names may also have the form @samp{class
14441 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14442 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14445 @item ptype [@var{arg}]
14446 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14447 detailed description of the type, instead of just the name of the type.
14448 @xref{Expressions, ,Expressions}.
14450 Contrary to @code{whatis}, @code{ptype} always unrolls any
14451 @code{typedef}s in its argument declaration, whether the argument is
14452 a variable, expression, or a data type. This means that @code{ptype}
14453 of a variable or an expression will not print literally its type as
14454 present in the source code---use @code{whatis} for that. @code{typedef}s at
14455 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14456 fields, methods and inner @code{class typedef}s of @code{struct}s,
14457 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14459 For example, for this variable declaration:
14462 typedef double real_t;
14463 struct complex @{ real_t real; double imag; @};
14464 typedef struct complex complex_t;
14466 real_t *real_pointer_var;
14470 the two commands give this output:
14474 (@value{GDBP}) whatis var
14476 (@value{GDBP}) ptype var
14477 type = struct complex @{
14481 (@value{GDBP}) whatis complex_t
14482 type = struct complex
14483 (@value{GDBP}) whatis struct complex
14484 type = struct complex
14485 (@value{GDBP}) ptype struct complex
14486 type = struct complex @{
14490 (@value{GDBP}) whatis real_pointer_var
14492 (@value{GDBP}) ptype real_pointer_var
14498 As with @code{whatis}, using @code{ptype} without an argument refers to
14499 the type of @code{$}, the last value in the value history.
14501 @cindex incomplete type
14502 Sometimes, programs use opaque data types or incomplete specifications
14503 of complex data structure. If the debug information included in the
14504 program does not allow @value{GDBN} to display a full declaration of
14505 the data type, it will say @samp{<incomplete type>}. For example,
14506 given these declarations:
14510 struct foo *fooptr;
14514 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14517 (@value{GDBP}) ptype foo
14518 $1 = <incomplete type>
14522 ``Incomplete type'' is C terminology for data types that are not
14523 completely specified.
14526 @item info types @var{regexp}
14528 Print a brief description of all types whose names match the regular
14529 expression @var{regexp} (or all types in your program, if you supply
14530 no argument). Each complete typename is matched as though it were a
14531 complete line; thus, @samp{i type value} gives information on all
14532 types in your program whose names include the string @code{value}, but
14533 @samp{i type ^value$} gives information only on types whose complete
14534 name is @code{value}.
14536 This command differs from @code{ptype} in two ways: first, like
14537 @code{whatis}, it does not print a detailed description; second, it
14538 lists all source files where a type is defined.
14541 @cindex local variables
14542 @item info scope @var{location}
14543 List all the variables local to a particular scope. This command
14544 accepts a @var{location} argument---a function name, a source line, or
14545 an address preceded by a @samp{*}, and prints all the variables local
14546 to the scope defined by that location. (@xref{Specify Location}, for
14547 details about supported forms of @var{location}.) For example:
14550 (@value{GDBP}) @b{info scope command_line_handler}
14551 Scope for command_line_handler:
14552 Symbol rl is an argument at stack/frame offset 8, length 4.
14553 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14554 Symbol linelength is in static storage at address 0x150a1c, length 4.
14555 Symbol p is a local variable in register $esi, length 4.
14556 Symbol p1 is a local variable in register $ebx, length 4.
14557 Symbol nline is a local variable in register $edx, length 4.
14558 Symbol repeat is a local variable at frame offset -8, length 4.
14562 This command is especially useful for determining what data to collect
14563 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14566 @kindex info source
14568 Show information about the current source file---that is, the source file for
14569 the function containing the current point of execution:
14572 the name of the source file, and the directory containing it,
14574 the directory it was compiled in,
14576 its length, in lines,
14578 which programming language it is written in,
14580 whether the executable includes debugging information for that file, and
14581 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14583 whether the debugging information includes information about
14584 preprocessor macros.
14588 @kindex info sources
14590 Print the names of all source files in your program for which there is
14591 debugging information, organized into two lists: files whose symbols
14592 have already been read, and files whose symbols will be read when needed.
14594 @kindex info functions
14595 @item info functions
14596 Print the names and data types of all defined functions.
14598 @item info functions @var{regexp}
14599 Print the names and data types of all defined functions
14600 whose names contain a match for regular expression @var{regexp}.
14601 Thus, @samp{info fun step} finds all functions whose names
14602 include @code{step}; @samp{info fun ^step} finds those whose names
14603 start with @code{step}. If a function name contains characters
14604 that conflict with the regular expression language (e.g.@:
14605 @samp{operator*()}), they may be quoted with a backslash.
14607 @kindex info variables
14608 @item info variables
14609 Print the names and data types of all variables that are defined
14610 outside of functions (i.e.@: excluding local variables).
14612 @item info variables @var{regexp}
14613 Print the names and data types of all variables (except for local
14614 variables) whose names contain a match for regular expression
14617 @kindex info classes
14618 @cindex Objective-C, classes and selectors
14620 @itemx info classes @var{regexp}
14621 Display all Objective-C classes in your program, or
14622 (with the @var{regexp} argument) all those matching a particular regular
14625 @kindex info selectors
14626 @item info selectors
14627 @itemx info selectors @var{regexp}
14628 Display all Objective-C selectors in your program, or
14629 (with the @var{regexp} argument) all those matching a particular regular
14633 This was never implemented.
14634 @kindex info methods
14636 @itemx info methods @var{regexp}
14637 The @code{info methods} command permits the user to examine all defined
14638 methods within C@t{++} program, or (with the @var{regexp} argument) a
14639 specific set of methods found in the various C@t{++} classes. Many
14640 C@t{++} classes provide a large number of methods. Thus, the output
14641 from the @code{ptype} command can be overwhelming and hard to use. The
14642 @code{info-methods} command filters the methods, printing only those
14643 which match the regular-expression @var{regexp}.
14646 @cindex reloading symbols
14647 Some systems allow individual object files that make up your program to
14648 be replaced without stopping and restarting your program. For example,
14649 in VxWorks you can simply recompile a defective object file and keep on
14650 running. If you are running on one of these systems, you can allow
14651 @value{GDBN} to reload the symbols for automatically relinked modules:
14654 @kindex set symbol-reloading
14655 @item set symbol-reloading on
14656 Replace symbol definitions for the corresponding source file when an
14657 object file with a particular name is seen again.
14659 @item set symbol-reloading off
14660 Do not replace symbol definitions when encountering object files of the
14661 same name more than once. This is the default state; if you are not
14662 running on a system that permits automatic relinking of modules, you
14663 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14664 may discard symbols when linking large programs, that may contain
14665 several modules (from different directories or libraries) with the same
14668 @kindex show symbol-reloading
14669 @item show symbol-reloading
14670 Show the current @code{on} or @code{off} setting.
14673 @cindex opaque data types
14674 @kindex set opaque-type-resolution
14675 @item set opaque-type-resolution on
14676 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14677 declared as a pointer to a @code{struct}, @code{class}, or
14678 @code{union}---for example, @code{struct MyType *}---that is used in one
14679 source file although the full declaration of @code{struct MyType} is in
14680 another source file. The default is on.
14682 A change in the setting of this subcommand will not take effect until
14683 the next time symbols for a file are loaded.
14685 @item set opaque-type-resolution off
14686 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14687 is printed as follows:
14689 @{<no data fields>@}
14692 @kindex show opaque-type-resolution
14693 @item show opaque-type-resolution
14694 Show whether opaque types are resolved or not.
14696 @kindex maint print symbols
14697 @cindex symbol dump
14698 @kindex maint print psymbols
14699 @cindex partial symbol dump
14700 @item maint print symbols @var{filename}
14701 @itemx maint print psymbols @var{filename}
14702 @itemx maint print msymbols @var{filename}
14703 Write a dump of debugging symbol data into the file @var{filename}.
14704 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14705 symbols with debugging data are included. If you use @samp{maint print
14706 symbols}, @value{GDBN} includes all the symbols for which it has already
14707 collected full details: that is, @var{filename} reflects symbols for
14708 only those files whose symbols @value{GDBN} has read. You can use the
14709 command @code{info sources} to find out which files these are. If you
14710 use @samp{maint print psymbols} instead, the dump shows information about
14711 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14712 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14713 @samp{maint print msymbols} dumps just the minimal symbol information
14714 required for each object file from which @value{GDBN} has read some symbols.
14715 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14716 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14718 @kindex maint info symtabs
14719 @kindex maint info psymtabs
14720 @cindex listing @value{GDBN}'s internal symbol tables
14721 @cindex symbol tables, listing @value{GDBN}'s internal
14722 @cindex full symbol tables, listing @value{GDBN}'s internal
14723 @cindex partial symbol tables, listing @value{GDBN}'s internal
14724 @item maint info symtabs @r{[} @var{regexp} @r{]}
14725 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14727 List the @code{struct symtab} or @code{struct partial_symtab}
14728 structures whose names match @var{regexp}. If @var{regexp} is not
14729 given, list them all. The output includes expressions which you can
14730 copy into a @value{GDBN} debugging this one to examine a particular
14731 structure in more detail. For example:
14734 (@value{GDBP}) maint info psymtabs dwarf2read
14735 @{ objfile /home/gnu/build/gdb/gdb
14736 ((struct objfile *) 0x82e69d0)
14737 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14738 ((struct partial_symtab *) 0x8474b10)
14741 text addresses 0x814d3c8 -- 0x8158074
14742 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14743 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14744 dependencies (none)
14747 (@value{GDBP}) maint info symtabs
14751 We see that there is one partial symbol table whose filename contains
14752 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14753 and we see that @value{GDBN} has not read in any symtabs yet at all.
14754 If we set a breakpoint on a function, that will cause @value{GDBN} to
14755 read the symtab for the compilation unit containing that function:
14758 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14759 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14761 (@value{GDBP}) maint info symtabs
14762 @{ objfile /home/gnu/build/gdb/gdb
14763 ((struct objfile *) 0x82e69d0)
14764 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14765 ((struct symtab *) 0x86c1f38)
14768 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14769 linetable ((struct linetable *) 0x8370fa0)
14770 debugformat DWARF 2
14779 @chapter Altering Execution
14781 Once you think you have found an error in your program, you might want to
14782 find out for certain whether correcting the apparent error would lead to
14783 correct results in the rest of the run. You can find the answer by
14784 experiment, using the @value{GDBN} features for altering execution of the
14787 For example, you can store new values into variables or memory
14788 locations, give your program a signal, restart it at a different
14789 address, or even return prematurely from a function.
14792 * Assignment:: Assignment to variables
14793 * Jumping:: Continuing at a different address
14794 * Signaling:: Giving your program a signal
14795 * Returning:: Returning from a function
14796 * Calling:: Calling your program's functions
14797 * Patching:: Patching your program
14801 @section Assignment to Variables
14804 @cindex setting variables
14805 To alter the value of a variable, evaluate an assignment expression.
14806 @xref{Expressions, ,Expressions}. For example,
14813 stores the value 4 into the variable @code{x}, and then prints the
14814 value of the assignment expression (which is 4).
14815 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14816 information on operators in supported languages.
14818 @kindex set variable
14819 @cindex variables, setting
14820 If you are not interested in seeing the value of the assignment, use the
14821 @code{set} command instead of the @code{print} command. @code{set} is
14822 really the same as @code{print} except that the expression's value is
14823 not printed and is not put in the value history (@pxref{Value History,
14824 ,Value History}). The expression is evaluated only for its effects.
14826 If the beginning of the argument string of the @code{set} command
14827 appears identical to a @code{set} subcommand, use the @code{set
14828 variable} command instead of just @code{set}. This command is identical
14829 to @code{set} except for its lack of subcommands. For example, if your
14830 program has a variable @code{width}, you get an error if you try to set
14831 a new value with just @samp{set width=13}, because @value{GDBN} has the
14832 command @code{set width}:
14835 (@value{GDBP}) whatis width
14837 (@value{GDBP}) p width
14839 (@value{GDBP}) set width=47
14840 Invalid syntax in expression.
14844 The invalid expression, of course, is @samp{=47}. In
14845 order to actually set the program's variable @code{width}, use
14848 (@value{GDBP}) set var width=47
14851 Because the @code{set} command has many subcommands that can conflict
14852 with the names of program variables, it is a good idea to use the
14853 @code{set variable} command instead of just @code{set}. For example, if
14854 your program has a variable @code{g}, you run into problems if you try
14855 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14856 the command @code{set gnutarget}, abbreviated @code{set g}:
14860 (@value{GDBP}) whatis g
14864 (@value{GDBP}) set g=4
14868 The program being debugged has been started already.
14869 Start it from the beginning? (y or n) y
14870 Starting program: /home/smith/cc_progs/a.out
14871 "/home/smith/cc_progs/a.out": can't open to read symbols:
14872 Invalid bfd target.
14873 (@value{GDBP}) show g
14874 The current BFD target is "=4".
14879 The program variable @code{g} did not change, and you silently set the
14880 @code{gnutarget} to an invalid value. In order to set the variable
14884 (@value{GDBP}) set var g=4
14887 @value{GDBN} allows more implicit conversions in assignments than C; you can
14888 freely store an integer value into a pointer variable or vice versa,
14889 and you can convert any structure to any other structure that is the
14890 same length or shorter.
14891 @comment FIXME: how do structs align/pad in these conversions?
14892 @comment /doc@cygnus.com 18dec1990
14894 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14895 construct to generate a value of specified type at a specified address
14896 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14897 to memory location @code{0x83040} as an integer (which implies a certain size
14898 and representation in memory), and
14901 set @{int@}0x83040 = 4
14905 stores the value 4 into that memory location.
14908 @section Continuing at a Different Address
14910 Ordinarily, when you continue your program, you do so at the place where
14911 it stopped, with the @code{continue} command. You can instead continue at
14912 an address of your own choosing, with the following commands:
14916 @item jump @var{linespec}
14917 @itemx jump @var{location}
14918 Resume execution at line @var{linespec} or at address given by
14919 @var{location}. Execution stops again immediately if there is a
14920 breakpoint there. @xref{Specify Location}, for a description of the
14921 different forms of @var{linespec} and @var{location}. It is common
14922 practice to use the @code{tbreak} command in conjunction with
14923 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14925 The @code{jump} command does not change the current stack frame, or
14926 the stack pointer, or the contents of any memory location or any
14927 register other than the program counter. If line @var{linespec} is in
14928 a different function from the one currently executing, the results may
14929 be bizarre if the two functions expect different patterns of arguments or
14930 of local variables. For this reason, the @code{jump} command requests
14931 confirmation if the specified line is not in the function currently
14932 executing. However, even bizarre results are predictable if you are
14933 well acquainted with the machine-language code of your program.
14936 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14937 On many systems, you can get much the same effect as the @code{jump}
14938 command by storing a new value into the register @code{$pc}. The
14939 difference is that this does not start your program running; it only
14940 changes the address of where it @emph{will} run when you continue. For
14948 makes the next @code{continue} command or stepping command execute at
14949 address @code{0x485}, rather than at the address where your program stopped.
14950 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14952 The most common occasion to use the @code{jump} command is to back
14953 up---perhaps with more breakpoints set---over a portion of a program
14954 that has already executed, in order to examine its execution in more
14959 @section Giving your Program a Signal
14960 @cindex deliver a signal to a program
14964 @item signal @var{signal}
14965 Resume execution where your program stopped, but immediately give it the
14966 signal @var{signal}. @var{signal} can be the name or the number of a
14967 signal. For example, on many systems @code{signal 2} and @code{signal
14968 SIGINT} are both ways of sending an interrupt signal.
14970 Alternatively, if @var{signal} is zero, continue execution without
14971 giving a signal. This is useful when your program stopped on account of
14972 a signal and would ordinary see the signal when resumed with the
14973 @code{continue} command; @samp{signal 0} causes it to resume without a
14976 @code{signal} does not repeat when you press @key{RET} a second time
14977 after executing the command.
14981 Invoking the @code{signal} command is not the same as invoking the
14982 @code{kill} utility from the shell. Sending a signal with @code{kill}
14983 causes @value{GDBN} to decide what to do with the signal depending on
14984 the signal handling tables (@pxref{Signals}). The @code{signal} command
14985 passes the signal directly to your program.
14989 @section Returning from a Function
14992 @cindex returning from a function
14995 @itemx return @var{expression}
14996 You can cancel execution of a function call with the @code{return}
14997 command. If you give an
14998 @var{expression} argument, its value is used as the function's return
15002 When you use @code{return}, @value{GDBN} discards the selected stack frame
15003 (and all frames within it). You can think of this as making the
15004 discarded frame return prematurely. If you wish to specify a value to
15005 be returned, give that value as the argument to @code{return}.
15007 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15008 Frame}), and any other frames inside of it, leaving its caller as the
15009 innermost remaining frame. That frame becomes selected. The
15010 specified value is stored in the registers used for returning values
15013 The @code{return} command does not resume execution; it leaves the
15014 program stopped in the state that would exist if the function had just
15015 returned. In contrast, the @code{finish} command (@pxref{Continuing
15016 and Stepping, ,Continuing and Stepping}) resumes execution until the
15017 selected stack frame returns naturally.
15019 @value{GDBN} needs to know how the @var{expression} argument should be set for
15020 the inferior. The concrete registers assignment depends on the OS ABI and the
15021 type being returned by the selected stack frame. For example it is common for
15022 OS ABI to return floating point values in FPU registers while integer values in
15023 CPU registers. Still some ABIs return even floating point values in CPU
15024 registers. Larger integer widths (such as @code{long long int}) also have
15025 specific placement rules. @value{GDBN} already knows the OS ABI from its
15026 current target so it needs to find out also the type being returned to make the
15027 assignment into the right register(s).
15029 Normally, the selected stack frame has debug info. @value{GDBN} will always
15030 use the debug info instead of the implicit type of @var{expression} when the
15031 debug info is available. For example, if you type @kbd{return -1}, and the
15032 function in the current stack frame is declared to return a @code{long long
15033 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15034 into a @code{long long int}:
15037 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15039 (@value{GDBP}) return -1
15040 Make func return now? (y or n) y
15041 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15042 43 printf ("result=%lld\n", func ());
15046 However, if the selected stack frame does not have a debug info, e.g., if the
15047 function was compiled without debug info, @value{GDBN} has to find out the type
15048 to return from user. Specifying a different type by mistake may set the value
15049 in different inferior registers than the caller code expects. For example,
15050 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15051 of a @code{long long int} result for a debug info less function (on 32-bit
15052 architectures). Therefore the user is required to specify the return type by
15053 an appropriate cast explicitly:
15056 Breakpoint 2, 0x0040050b in func ()
15057 (@value{GDBP}) return -1
15058 Return value type not available for selected stack frame.
15059 Please use an explicit cast of the value to return.
15060 (@value{GDBP}) return (long long int) -1
15061 Make selected stack frame return now? (y or n) y
15062 #0 0x00400526 in main ()
15067 @section Calling Program Functions
15070 @cindex calling functions
15071 @cindex inferior functions, calling
15072 @item print @var{expr}
15073 Evaluate the expression @var{expr} and display the resulting value.
15074 @var{expr} may include calls to functions in the program being
15078 @item call @var{expr}
15079 Evaluate the expression @var{expr} without displaying @code{void}
15082 You can use this variant of the @code{print} command if you want to
15083 execute a function from your program that does not return anything
15084 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15085 with @code{void} returned values that @value{GDBN} will otherwise
15086 print. If the result is not void, it is printed and saved in the
15090 It is possible for the function you call via the @code{print} or
15091 @code{call} command to generate a signal (e.g., if there's a bug in
15092 the function, or if you passed it incorrect arguments). What happens
15093 in that case is controlled by the @code{set unwindonsignal} command.
15095 Similarly, with a C@t{++} program it is possible for the function you
15096 call via the @code{print} or @code{call} command to generate an
15097 exception that is not handled due to the constraints of the dummy
15098 frame. In this case, any exception that is raised in the frame, but has
15099 an out-of-frame exception handler will not be found. GDB builds a
15100 dummy-frame for the inferior function call, and the unwinder cannot
15101 seek for exception handlers outside of this dummy-frame. What happens
15102 in that case is controlled by the
15103 @code{set unwind-on-terminating-exception} command.
15106 @item set unwindonsignal
15107 @kindex set unwindonsignal
15108 @cindex unwind stack in called functions
15109 @cindex call dummy stack unwinding
15110 Set unwinding of the stack if a signal is received while in a function
15111 that @value{GDBN} called in the program being debugged. If set to on,
15112 @value{GDBN} unwinds the stack it created for the call and restores
15113 the context to what it was before the call. If set to off (the
15114 default), @value{GDBN} stops in the frame where the signal was
15117 @item show unwindonsignal
15118 @kindex show unwindonsignal
15119 Show the current setting of stack unwinding in the functions called by
15122 @item set unwind-on-terminating-exception
15123 @kindex set unwind-on-terminating-exception
15124 @cindex unwind stack in called functions with unhandled exceptions
15125 @cindex call dummy stack unwinding on unhandled exception.
15126 Set unwinding of the stack if a C@t{++} exception is raised, but left
15127 unhandled while in a function that @value{GDBN} called in the program being
15128 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15129 it created for the call and restores the context to what it was before
15130 the call. If set to off, @value{GDBN} the exception is delivered to
15131 the default C@t{++} exception handler and the inferior terminated.
15133 @item show unwind-on-terminating-exception
15134 @kindex show unwind-on-terminating-exception
15135 Show the current setting of stack unwinding in the functions called by
15140 @cindex weak alias functions
15141 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15142 for another function. In such case, @value{GDBN} might not pick up
15143 the type information, including the types of the function arguments,
15144 which causes @value{GDBN} to call the inferior function incorrectly.
15145 As a result, the called function will function erroneously and may
15146 even crash. A solution to that is to use the name of the aliased
15150 @section Patching Programs
15152 @cindex patching binaries
15153 @cindex writing into executables
15154 @cindex writing into corefiles
15156 By default, @value{GDBN} opens the file containing your program's
15157 executable code (or the corefile) read-only. This prevents accidental
15158 alterations to machine code; but it also prevents you from intentionally
15159 patching your program's binary.
15161 If you'd like to be able to patch the binary, you can specify that
15162 explicitly with the @code{set write} command. For example, you might
15163 want to turn on internal debugging flags, or even to make emergency
15169 @itemx set write off
15170 If you specify @samp{set write on}, @value{GDBN} opens executable and
15171 core files for both reading and writing; if you specify @kbd{set write
15172 off} (the default), @value{GDBN} opens them read-only.
15174 If you have already loaded a file, you must load it again (using the
15175 @code{exec-file} or @code{core-file} command) after changing @code{set
15176 write}, for your new setting to take effect.
15180 Display whether executable files and core files are opened for writing
15181 as well as reading.
15185 @chapter @value{GDBN} Files
15187 @value{GDBN} needs to know the file name of the program to be debugged,
15188 both in order to read its symbol table and in order to start your
15189 program. To debug a core dump of a previous run, you must also tell
15190 @value{GDBN} the name of the core dump file.
15193 * Files:: Commands to specify files
15194 * Separate Debug Files:: Debugging information in separate files
15195 * Index Files:: Index files speed up GDB
15196 * Symbol Errors:: Errors reading symbol files
15197 * Data Files:: GDB data files
15201 @section Commands to Specify Files
15203 @cindex symbol table
15204 @cindex core dump file
15206 You may want to specify executable and core dump file names. The usual
15207 way to do this is at start-up time, using the arguments to
15208 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15209 Out of @value{GDBN}}).
15211 Occasionally it is necessary to change to a different file during a
15212 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15213 specify a file you want to use. Or you are debugging a remote target
15214 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15215 Program}). In these situations the @value{GDBN} commands to specify
15216 new files are useful.
15219 @cindex executable file
15221 @item file @var{filename}
15222 Use @var{filename} as the program to be debugged. It is read for its
15223 symbols and for the contents of pure memory. It is also the program
15224 executed when you use the @code{run} command. If you do not specify a
15225 directory and the file is not found in the @value{GDBN} working directory,
15226 @value{GDBN} uses the environment variable @code{PATH} as a list of
15227 directories to search, just as the shell does when looking for a program
15228 to run. You can change the value of this variable, for both @value{GDBN}
15229 and your program, using the @code{path} command.
15231 @cindex unlinked object files
15232 @cindex patching object files
15233 You can load unlinked object @file{.o} files into @value{GDBN} using
15234 the @code{file} command. You will not be able to ``run'' an object
15235 file, but you can disassemble functions and inspect variables. Also,
15236 if the underlying BFD functionality supports it, you could use
15237 @kbd{gdb -write} to patch object files using this technique. Note
15238 that @value{GDBN} can neither interpret nor modify relocations in this
15239 case, so branches and some initialized variables will appear to go to
15240 the wrong place. But this feature is still handy from time to time.
15243 @code{file} with no argument makes @value{GDBN} discard any information it
15244 has on both executable file and the symbol table.
15247 @item exec-file @r{[} @var{filename} @r{]}
15248 Specify that the program to be run (but not the symbol table) is found
15249 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15250 if necessary to locate your program. Omitting @var{filename} means to
15251 discard information on the executable file.
15253 @kindex symbol-file
15254 @item symbol-file @r{[} @var{filename} @r{]}
15255 Read symbol table information from file @var{filename}. @code{PATH} is
15256 searched when necessary. Use the @code{file} command to get both symbol
15257 table and program to run from the same file.
15259 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15260 program's symbol table.
15262 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15263 some breakpoints and auto-display expressions. This is because they may
15264 contain pointers to the internal data recording symbols and data types,
15265 which are part of the old symbol table data being discarded inside
15268 @code{symbol-file} does not repeat if you press @key{RET} again after
15271 When @value{GDBN} is configured for a particular environment, it
15272 understands debugging information in whatever format is the standard
15273 generated for that environment; you may use either a @sc{gnu} compiler, or
15274 other compilers that adhere to the local conventions.
15275 Best results are usually obtained from @sc{gnu} compilers; for example,
15276 using @code{@value{NGCC}} you can generate debugging information for
15279 For most kinds of object files, with the exception of old SVR3 systems
15280 using COFF, the @code{symbol-file} command does not normally read the
15281 symbol table in full right away. Instead, it scans the symbol table
15282 quickly to find which source files and which symbols are present. The
15283 details are read later, one source file at a time, as they are needed.
15285 The purpose of this two-stage reading strategy is to make @value{GDBN}
15286 start up faster. For the most part, it is invisible except for
15287 occasional pauses while the symbol table details for a particular source
15288 file are being read. (The @code{set verbose} command can turn these
15289 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15290 Warnings and Messages}.)
15292 We have not implemented the two-stage strategy for COFF yet. When the
15293 symbol table is stored in COFF format, @code{symbol-file} reads the
15294 symbol table data in full right away. Note that ``stabs-in-COFF''
15295 still does the two-stage strategy, since the debug info is actually
15299 @cindex reading symbols immediately
15300 @cindex symbols, reading immediately
15301 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15302 @itemx file @r{[} -readnow @r{]} @var{filename}
15303 You can override the @value{GDBN} two-stage strategy for reading symbol
15304 tables by using the @samp{-readnow} option with any of the commands that
15305 load symbol table information, if you want to be sure @value{GDBN} has the
15306 entire symbol table available.
15308 @c FIXME: for now no mention of directories, since this seems to be in
15309 @c flux. 13mar1992 status is that in theory GDB would look either in
15310 @c current dir or in same dir as myprog; but issues like competing
15311 @c GDB's, or clutter in system dirs, mean that in practice right now
15312 @c only current dir is used. FFish says maybe a special GDB hierarchy
15313 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15317 @item core-file @r{[}@var{filename}@r{]}
15319 Specify the whereabouts of a core dump file to be used as the ``contents
15320 of memory''. Traditionally, core files contain only some parts of the
15321 address space of the process that generated them; @value{GDBN} can access the
15322 executable file itself for other parts.
15324 @code{core-file} with no argument specifies that no core file is
15327 Note that the core file is ignored when your program is actually running
15328 under @value{GDBN}. So, if you have been running your program and you
15329 wish to debug a core file instead, you must kill the subprocess in which
15330 the program is running. To do this, use the @code{kill} command
15331 (@pxref{Kill Process, ,Killing the Child Process}).
15333 @kindex add-symbol-file
15334 @cindex dynamic linking
15335 @item add-symbol-file @var{filename} @var{address}
15336 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15337 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15338 The @code{add-symbol-file} command reads additional symbol table
15339 information from the file @var{filename}. You would use this command
15340 when @var{filename} has been dynamically loaded (by some other means)
15341 into the program that is running. @var{address} should be the memory
15342 address at which the file has been loaded; @value{GDBN} cannot figure
15343 this out for itself. You can additionally specify an arbitrary number
15344 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15345 section name and base address for that section. You can specify any
15346 @var{address} as an expression.
15348 The symbol table of the file @var{filename} is added to the symbol table
15349 originally read with the @code{symbol-file} command. You can use the
15350 @code{add-symbol-file} command any number of times; the new symbol data
15351 thus read keeps adding to the old. To discard all old symbol data
15352 instead, use the @code{symbol-file} command without any arguments.
15354 @cindex relocatable object files, reading symbols from
15355 @cindex object files, relocatable, reading symbols from
15356 @cindex reading symbols from relocatable object files
15357 @cindex symbols, reading from relocatable object files
15358 @cindex @file{.o} files, reading symbols from
15359 Although @var{filename} is typically a shared library file, an
15360 executable file, or some other object file which has been fully
15361 relocated for loading into a process, you can also load symbolic
15362 information from relocatable @file{.o} files, as long as:
15366 the file's symbolic information refers only to linker symbols defined in
15367 that file, not to symbols defined by other object files,
15369 every section the file's symbolic information refers to has actually
15370 been loaded into the inferior, as it appears in the file, and
15372 you can determine the address at which every section was loaded, and
15373 provide these to the @code{add-symbol-file} command.
15377 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15378 relocatable files into an already running program; such systems
15379 typically make the requirements above easy to meet. However, it's
15380 important to recognize that many native systems use complex link
15381 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15382 assembly, for example) that make the requirements difficult to meet. In
15383 general, one cannot assume that using @code{add-symbol-file} to read a
15384 relocatable object file's symbolic information will have the same effect
15385 as linking the relocatable object file into the program in the normal
15388 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15390 @kindex add-symbol-file-from-memory
15391 @cindex @code{syscall DSO}
15392 @cindex load symbols from memory
15393 @item add-symbol-file-from-memory @var{address}
15394 Load symbols from the given @var{address} in a dynamically loaded
15395 object file whose image is mapped directly into the inferior's memory.
15396 For example, the Linux kernel maps a @code{syscall DSO} into each
15397 process's address space; this DSO provides kernel-specific code for
15398 some system calls. The argument can be any expression whose
15399 evaluation yields the address of the file's shared object file header.
15400 For this command to work, you must have used @code{symbol-file} or
15401 @code{exec-file} commands in advance.
15403 @kindex add-shared-symbol-files
15405 @item add-shared-symbol-files @var{library-file}
15406 @itemx assf @var{library-file}
15407 The @code{add-shared-symbol-files} command can currently be used only
15408 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15409 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15410 @value{GDBN} automatically looks for shared libraries, however if
15411 @value{GDBN} does not find yours, you can invoke
15412 @code{add-shared-symbol-files}. It takes one argument: the shared
15413 library's file name. @code{assf} is a shorthand alias for
15414 @code{add-shared-symbol-files}.
15417 @item section @var{section} @var{addr}
15418 The @code{section} command changes the base address of the named
15419 @var{section} of the exec file to @var{addr}. This can be used if the
15420 exec file does not contain section addresses, (such as in the
15421 @code{a.out} format), or when the addresses specified in the file
15422 itself are wrong. Each section must be changed separately. The
15423 @code{info files} command, described below, lists all the sections and
15427 @kindex info target
15430 @code{info files} and @code{info target} are synonymous; both print the
15431 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15432 including the names of the executable and core dump files currently in
15433 use by @value{GDBN}, and the files from which symbols were loaded. The
15434 command @code{help target} lists all possible targets rather than
15437 @kindex maint info sections
15438 @item maint info sections
15439 Another command that can give you extra information about program sections
15440 is @code{maint info sections}. In addition to the section information
15441 displayed by @code{info files}, this command displays the flags and file
15442 offset of each section in the executable and core dump files. In addition,
15443 @code{maint info sections} provides the following command options (which
15444 may be arbitrarily combined):
15448 Display sections for all loaded object files, including shared libraries.
15449 @item @var{sections}
15450 Display info only for named @var{sections}.
15451 @item @var{section-flags}
15452 Display info only for sections for which @var{section-flags} are true.
15453 The section flags that @value{GDBN} currently knows about are:
15456 Section will have space allocated in the process when loaded.
15457 Set for all sections except those containing debug information.
15459 Section will be loaded from the file into the child process memory.
15460 Set for pre-initialized code and data, clear for @code{.bss} sections.
15462 Section needs to be relocated before loading.
15464 Section cannot be modified by the child process.
15466 Section contains executable code only.
15468 Section contains data only (no executable code).
15470 Section will reside in ROM.
15472 Section contains data for constructor/destructor lists.
15474 Section is not empty.
15476 An instruction to the linker to not output the section.
15477 @item COFF_SHARED_LIBRARY
15478 A notification to the linker that the section contains
15479 COFF shared library information.
15481 Section contains common symbols.
15484 @kindex set trust-readonly-sections
15485 @cindex read-only sections
15486 @item set trust-readonly-sections on
15487 Tell @value{GDBN} that readonly sections in your object file
15488 really are read-only (i.e.@: that their contents will not change).
15489 In that case, @value{GDBN} can fetch values from these sections
15490 out of the object file, rather than from the target program.
15491 For some targets (notably embedded ones), this can be a significant
15492 enhancement to debugging performance.
15494 The default is off.
15496 @item set trust-readonly-sections off
15497 Tell @value{GDBN} not to trust readonly sections. This means that
15498 the contents of the section might change while the program is running,
15499 and must therefore be fetched from the target when needed.
15501 @item show trust-readonly-sections
15502 Show the current setting of trusting readonly sections.
15505 All file-specifying commands allow both absolute and relative file names
15506 as arguments. @value{GDBN} always converts the file name to an absolute file
15507 name and remembers it that way.
15509 @cindex shared libraries
15510 @anchor{Shared Libraries}
15511 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15512 and IBM RS/6000 AIX shared libraries.
15514 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15515 shared libraries. @xref{Expat}.
15517 @value{GDBN} automatically loads symbol definitions from shared libraries
15518 when you use the @code{run} command, or when you examine a core file.
15519 (Before you issue the @code{run} command, @value{GDBN} does not understand
15520 references to a function in a shared library, however---unless you are
15521 debugging a core file).
15523 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15524 automatically loads the symbols at the time of the @code{shl_load} call.
15526 @c FIXME: some @value{GDBN} release may permit some refs to undef
15527 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15528 @c FIXME...lib; check this from time to time when updating manual
15530 There are times, however, when you may wish to not automatically load
15531 symbol definitions from shared libraries, such as when they are
15532 particularly large or there are many of them.
15534 To control the automatic loading of shared library symbols, use the
15538 @kindex set auto-solib-add
15539 @item set auto-solib-add @var{mode}
15540 If @var{mode} is @code{on}, symbols from all shared object libraries
15541 will be loaded automatically when the inferior begins execution, you
15542 attach to an independently started inferior, or when the dynamic linker
15543 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15544 is @code{off}, symbols must be loaded manually, using the
15545 @code{sharedlibrary} command. The default value is @code{on}.
15547 @cindex memory used for symbol tables
15548 If your program uses lots of shared libraries with debug info that
15549 takes large amounts of memory, you can decrease the @value{GDBN}
15550 memory footprint by preventing it from automatically loading the
15551 symbols from shared libraries. To that end, type @kbd{set
15552 auto-solib-add off} before running the inferior, then load each
15553 library whose debug symbols you do need with @kbd{sharedlibrary
15554 @var{regexp}}, where @var{regexp} is a regular expression that matches
15555 the libraries whose symbols you want to be loaded.
15557 @kindex show auto-solib-add
15558 @item show auto-solib-add
15559 Display the current autoloading mode.
15562 @cindex load shared library
15563 To explicitly load shared library symbols, use the @code{sharedlibrary}
15567 @kindex info sharedlibrary
15569 @item info share @var{regex}
15570 @itemx info sharedlibrary @var{regex}
15571 Print the names of the shared libraries which are currently loaded
15572 that match @var{regex}. If @var{regex} is omitted then print
15573 all shared libraries that are loaded.
15575 @kindex sharedlibrary
15577 @item sharedlibrary @var{regex}
15578 @itemx share @var{regex}
15579 Load shared object library symbols for files matching a
15580 Unix regular expression.
15581 As with files loaded automatically, it only loads shared libraries
15582 required by your program for a core file or after typing @code{run}. If
15583 @var{regex} is omitted all shared libraries required by your program are
15586 @item nosharedlibrary
15587 @kindex nosharedlibrary
15588 @cindex unload symbols from shared libraries
15589 Unload all shared object library symbols. This discards all symbols
15590 that have been loaded from all shared libraries. Symbols from shared
15591 libraries that were loaded by explicit user requests are not
15595 Sometimes you may wish that @value{GDBN} stops and gives you control
15596 when any of shared library events happen. Use the @code{set
15597 stop-on-solib-events} command for this:
15600 @item set stop-on-solib-events
15601 @kindex set stop-on-solib-events
15602 This command controls whether @value{GDBN} should give you control
15603 when the dynamic linker notifies it about some shared library event.
15604 The most common event of interest is loading or unloading of a new
15607 @item show stop-on-solib-events
15608 @kindex show stop-on-solib-events
15609 Show whether @value{GDBN} stops and gives you control when shared
15610 library events happen.
15613 Shared libraries are also supported in many cross or remote debugging
15614 configurations. @value{GDBN} needs to have access to the target's libraries;
15615 this can be accomplished either by providing copies of the libraries
15616 on the host system, or by asking @value{GDBN} to automatically retrieve the
15617 libraries from the target. If copies of the target libraries are
15618 provided, they need to be the same as the target libraries, although the
15619 copies on the target can be stripped as long as the copies on the host are
15622 @cindex where to look for shared libraries
15623 For remote debugging, you need to tell @value{GDBN} where the target
15624 libraries are, so that it can load the correct copies---otherwise, it
15625 may try to load the host's libraries. @value{GDBN} has two variables
15626 to specify the search directories for target libraries.
15629 @cindex prefix for shared library file names
15630 @cindex system root, alternate
15631 @kindex set solib-absolute-prefix
15632 @kindex set sysroot
15633 @item set sysroot @var{path}
15634 Use @var{path} as the system root for the program being debugged. Any
15635 absolute shared library paths will be prefixed with @var{path}; many
15636 runtime loaders store the absolute paths to the shared library in the
15637 target program's memory. If you use @code{set sysroot} to find shared
15638 libraries, they need to be laid out in the same way that they are on
15639 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15642 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15643 retrieve the target libraries from the remote system. This is only
15644 supported when using a remote target that supports the @code{remote get}
15645 command (@pxref{File Transfer,,Sending files to a remote system}).
15646 The part of @var{path} following the initial @file{remote:}
15647 (if present) is used as system root prefix on the remote file system.
15648 @footnote{If you want to specify a local system root using a directory
15649 that happens to be named @file{remote:}, you need to use some equivalent
15650 variant of the name like @file{./remote:}.}
15652 For targets with an MS-DOS based filesystem, such as MS-Windows and
15653 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15654 absolute file name with @var{path}. But first, on Unix hosts,
15655 @value{GDBN} converts all backslash directory separators into forward
15656 slashes, because the backslash is not a directory separator on Unix:
15659 c:\foo\bar.dll @result{} c:/foo/bar.dll
15662 Then, @value{GDBN} attempts prefixing the target file name with
15663 @var{path}, and looks for the resulting file name in the host file
15667 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15670 If that does not find the shared library, @value{GDBN} tries removing
15671 the @samp{:} character from the drive spec, both for convenience, and,
15672 for the case of the host file system not supporting file names with
15676 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15679 This makes it possible to have a system root that mirrors a target
15680 with more than one drive. E.g., you may want to setup your local
15681 copies of the target system shared libraries like so (note @samp{c} vs
15685 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15686 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15687 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15691 and point the system root at @file{/path/to/sysroot}, so that
15692 @value{GDBN} can find the correct copies of both
15693 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15695 If that still does not find the shared library, @value{GDBN} tries
15696 removing the whole drive spec from the target file name:
15699 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15702 This last lookup makes it possible to not care about the drive name,
15703 if you don't want or need to.
15705 The @code{set solib-absolute-prefix} command is an alias for @code{set
15708 @cindex default system root
15709 @cindex @samp{--with-sysroot}
15710 You can set the default system root by using the configure-time
15711 @samp{--with-sysroot} option. If the system root is inside
15712 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15713 @samp{--exec-prefix}), then the default system root will be updated
15714 automatically if the installed @value{GDBN} is moved to a new
15717 @kindex show sysroot
15719 Display the current shared library prefix.
15721 @kindex set solib-search-path
15722 @item set solib-search-path @var{path}
15723 If this variable is set, @var{path} is a colon-separated list of
15724 directories to search for shared libraries. @samp{solib-search-path}
15725 is used after @samp{sysroot} fails to locate the library, or if the
15726 path to the library is relative instead of absolute. If you want to
15727 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15728 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15729 finding your host's libraries. @samp{sysroot} is preferred; setting
15730 it to a nonexistent directory may interfere with automatic loading
15731 of shared library symbols.
15733 @kindex show solib-search-path
15734 @item show solib-search-path
15735 Display the current shared library search path.
15737 @cindex DOS file-name semantics of file names.
15738 @kindex set target-file-system-kind (unix|dos-based|auto)
15739 @kindex show target-file-system-kind
15740 @item set target-file-system-kind @var{kind}
15741 Set assumed file system kind for target reported file names.
15743 Shared library file names as reported by the target system may not
15744 make sense as is on the system @value{GDBN} is running on. For
15745 example, when remote debugging a target that has MS-DOS based file
15746 system semantics, from a Unix host, the target may be reporting to
15747 @value{GDBN} a list of loaded shared libraries with file names such as
15748 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15749 drive letters, so the @samp{c:\} prefix is not normally understood as
15750 indicating an absolute file name, and neither is the backslash
15751 normally considered a directory separator character. In that case,
15752 the native file system would interpret this whole absolute file name
15753 as a relative file name with no directory components. This would make
15754 it impossible to point @value{GDBN} at a copy of the remote target's
15755 shared libraries on the host using @code{set sysroot}, and impractical
15756 with @code{set solib-search-path}. Setting
15757 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15758 to interpret such file names similarly to how the target would, and to
15759 map them to file names valid on @value{GDBN}'s native file system
15760 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15761 to one of the supported file system kinds. In that case, @value{GDBN}
15762 tries to determine the appropriate file system variant based on the
15763 current target's operating system (@pxref{ABI, ,Configuring the
15764 Current ABI}). The supported file system settings are:
15768 Instruct @value{GDBN} to assume the target file system is of Unix
15769 kind. Only file names starting the forward slash (@samp{/}) character
15770 are considered absolute, and the directory separator character is also
15774 Instruct @value{GDBN} to assume the target file system is DOS based.
15775 File names starting with either a forward slash, or a drive letter
15776 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15777 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15778 considered directory separators.
15781 Instruct @value{GDBN} to use the file system kind associated with the
15782 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15783 This is the default.
15787 @cindex file name canonicalization
15788 @cindex base name differences
15789 When processing file names provided by the user, @value{GDBN}
15790 frequently needs to compare them to the file names recorded in the
15791 program's debug info. Normally, @value{GDBN} compares just the
15792 @dfn{base names} of the files as strings, which is reasonably fast
15793 even for very large programs. (The base name of a file is the last
15794 portion of its name, after stripping all the leading directories.)
15795 This shortcut in comparison is based upon the assumption that files
15796 cannot have more than one base name. This is usually true, but
15797 references to files that use symlinks or similar filesystem
15798 facilities violate that assumption. If your program records files
15799 using such facilities, or if you provide file names to @value{GDBN}
15800 using symlinks etc., you can set @code{basenames-may-differ} to
15801 @code{true} to instruct @value{GDBN} to completely canonicalize each
15802 pair of file names it needs to compare. This will make file-name
15803 comparisons accurate, but at a price of a significant slowdown.
15806 @item set basenames-may-differ
15807 @kindex set basenames-may-differ
15808 Set whether a source file may have multiple base names.
15810 @item show basenames-may-differ
15811 @kindex show basenames-may-differ
15812 Show whether a source file may have multiple base names.
15815 @node Separate Debug Files
15816 @section Debugging Information in Separate Files
15817 @cindex separate debugging information files
15818 @cindex debugging information in separate files
15819 @cindex @file{.debug} subdirectories
15820 @cindex debugging information directory, global
15821 @cindex global debugging information directory
15822 @cindex build ID, and separate debugging files
15823 @cindex @file{.build-id} directory
15825 @value{GDBN} allows you to put a program's debugging information in a
15826 file separate from the executable itself, in a way that allows
15827 @value{GDBN} to find and load the debugging information automatically.
15828 Since debugging information can be very large---sometimes larger
15829 than the executable code itself---some systems distribute debugging
15830 information for their executables in separate files, which users can
15831 install only when they need to debug a problem.
15833 @value{GDBN} supports two ways of specifying the separate debug info
15838 The executable contains a @dfn{debug link} that specifies the name of
15839 the separate debug info file. The separate debug file's name is
15840 usually @file{@var{executable}.debug}, where @var{executable} is the
15841 name of the corresponding executable file without leading directories
15842 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15843 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15844 checksum for the debug file, which @value{GDBN} uses to validate that
15845 the executable and the debug file came from the same build.
15848 The executable contains a @dfn{build ID}, a unique bit string that is
15849 also present in the corresponding debug info file. (This is supported
15850 only on some operating systems, notably those which use the ELF format
15851 for binary files and the @sc{gnu} Binutils.) For more details about
15852 this feature, see the description of the @option{--build-id}
15853 command-line option in @ref{Options, , Command Line Options, ld.info,
15854 The GNU Linker}. The debug info file's name is not specified
15855 explicitly by the build ID, but can be computed from the build ID, see
15859 Depending on the way the debug info file is specified, @value{GDBN}
15860 uses two different methods of looking for the debug file:
15864 For the ``debug link'' method, @value{GDBN} looks up the named file in
15865 the directory of the executable file, then in a subdirectory of that
15866 directory named @file{.debug}, and finally under the global debug
15867 directory, in a subdirectory whose name is identical to the leading
15868 directories of the executable's absolute file name.
15871 For the ``build ID'' method, @value{GDBN} looks in the
15872 @file{.build-id} subdirectory of the global debug directory for a file
15873 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15874 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15875 are the rest of the bit string. (Real build ID strings are 32 or more
15876 hex characters, not 10.)
15879 So, for example, suppose you ask @value{GDBN} to debug
15880 @file{/usr/bin/ls}, which has a debug link that specifies the
15881 file @file{ls.debug}, and a build ID whose value in hex is
15882 @code{abcdef1234}. If the global debug directory is
15883 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15884 debug information files, in the indicated order:
15888 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15890 @file{/usr/bin/ls.debug}
15892 @file{/usr/bin/.debug/ls.debug}
15894 @file{/usr/lib/debug/usr/bin/ls.debug}.
15897 You can set the global debugging info directory's name, and view the
15898 name @value{GDBN} is currently using.
15902 @kindex set debug-file-directory
15903 @item set debug-file-directory @var{directories}
15904 Set the directories which @value{GDBN} searches for separate debugging
15905 information files to @var{directory}. Multiple directory components can be set
15906 concatenating them by a directory separator.
15908 @kindex show debug-file-directory
15909 @item show debug-file-directory
15910 Show the directories @value{GDBN} searches for separate debugging
15915 @cindex @code{.gnu_debuglink} sections
15916 @cindex debug link sections
15917 A debug link is a special section of the executable file named
15918 @code{.gnu_debuglink}. The section must contain:
15922 A filename, with any leading directory components removed, followed by
15925 zero to three bytes of padding, as needed to reach the next four-byte
15926 boundary within the section, and
15928 a four-byte CRC checksum, stored in the same endianness used for the
15929 executable file itself. The checksum is computed on the debugging
15930 information file's full contents by the function given below, passing
15931 zero as the @var{crc} argument.
15934 Any executable file format can carry a debug link, as long as it can
15935 contain a section named @code{.gnu_debuglink} with the contents
15938 @cindex @code{.note.gnu.build-id} sections
15939 @cindex build ID sections
15940 The build ID is a special section in the executable file (and in other
15941 ELF binary files that @value{GDBN} may consider). This section is
15942 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15943 It contains unique identification for the built files---the ID remains
15944 the same across multiple builds of the same build tree. The default
15945 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15946 content for the build ID string. The same section with an identical
15947 value is present in the original built binary with symbols, in its
15948 stripped variant, and in the separate debugging information file.
15950 The debugging information file itself should be an ordinary
15951 executable, containing a full set of linker symbols, sections, and
15952 debugging information. The sections of the debugging information file
15953 should have the same names, addresses, and sizes as the original file,
15954 but they need not contain any data---much like a @code{.bss} section
15955 in an ordinary executable.
15957 The @sc{gnu} binary utilities (Binutils) package includes the
15958 @samp{objcopy} utility that can produce
15959 the separated executable / debugging information file pairs using the
15960 following commands:
15963 @kbd{objcopy --only-keep-debug foo foo.debug}
15968 These commands remove the debugging
15969 information from the executable file @file{foo} and place it in the file
15970 @file{foo.debug}. You can use the first, second or both methods to link the
15975 The debug link method needs the following additional command to also leave
15976 behind a debug link in @file{foo}:
15979 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15982 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15983 a version of the @code{strip} command such that the command @kbd{strip foo -f
15984 foo.debug} has the same functionality as the two @code{objcopy} commands and
15985 the @code{ln -s} command above, together.
15988 Build ID gets embedded into the main executable using @code{ld --build-id} or
15989 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15990 compatibility fixes for debug files separation are present in @sc{gnu} binary
15991 utilities (Binutils) package since version 2.18.
15996 @cindex CRC algorithm definition
15997 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15998 IEEE 802.3 using the polynomial:
16000 @c TexInfo requires naked braces for multi-digit exponents for Tex
16001 @c output, but this causes HTML output to barf. HTML has to be set using
16002 @c raw commands. So we end up having to specify this equation in 2
16007 <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>
16008 + <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
16014 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16015 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16019 The function is computed byte at a time, taking the least
16020 significant bit of each byte first. The initial pattern
16021 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16022 the final result is inverted to ensure trailing zeros also affect the
16025 @emph{Note:} This is the same CRC polynomial as used in handling the
16026 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16027 , @value{GDBN} Remote Serial Protocol}). However in the
16028 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16029 significant bit first, and the result is not inverted, so trailing
16030 zeros have no effect on the CRC value.
16032 To complete the description, we show below the code of the function
16033 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16034 initially supplied @code{crc} argument means that an initial call to
16035 this function passing in zero will start computing the CRC using
16038 @kindex gnu_debuglink_crc32
16041 gnu_debuglink_crc32 (unsigned long crc,
16042 unsigned char *buf, size_t len)
16044 static const unsigned long crc32_table[256] =
16046 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16047 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16048 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16049 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16050 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16051 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16052 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16053 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16054 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16055 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16056 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16057 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16058 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16059 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16060 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16061 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16062 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16063 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16064 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16065 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16066 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16067 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16068 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16069 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16070 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16071 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16072 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16073 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16074 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16075 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16076 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16077 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16078 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16079 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16080 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16081 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16082 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16083 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16084 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16085 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16086 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16087 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16088 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16089 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16090 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16091 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16092 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16093 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16094 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16095 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16096 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16099 unsigned char *end;
16101 crc = ~crc & 0xffffffff;
16102 for (end = buf + len; buf < end; ++buf)
16103 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16104 return ~crc & 0xffffffff;
16109 This computation does not apply to the ``build ID'' method.
16113 @section Index Files Speed Up @value{GDBN}
16114 @cindex index files
16115 @cindex @samp{.gdb_index} section
16117 When @value{GDBN} finds a symbol file, it scans the symbols in the
16118 file in order to construct an internal symbol table. This lets most
16119 @value{GDBN} operations work quickly---at the cost of a delay early
16120 on. For large programs, this delay can be quite lengthy, so
16121 @value{GDBN} provides a way to build an index, which speeds up
16124 The index is stored as a section in the symbol file. @value{GDBN} can
16125 write the index to a file, then you can put it into the symbol file
16126 using @command{objcopy}.
16128 To create an index file, use the @code{save gdb-index} command:
16131 @item save gdb-index @var{directory}
16132 @kindex save gdb-index
16133 Create an index file for each symbol file currently known by
16134 @value{GDBN}. Each file is named after its corresponding symbol file,
16135 with @samp{.gdb-index} appended, and is written into the given
16139 Once you have created an index file you can merge it into your symbol
16140 file, here named @file{symfile}, using @command{objcopy}:
16143 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16144 --set-section-flags .gdb_index=readonly symfile symfile
16147 There are currently some limitation on indices. They only work when
16148 for DWARF debugging information, not stabs. And, they do not
16149 currently work for programs using Ada.
16151 @node Symbol Errors
16152 @section Errors Reading Symbol Files
16154 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16155 such as symbol types it does not recognize, or known bugs in compiler
16156 output. By default, @value{GDBN} does not notify you of such problems, since
16157 they are relatively common and primarily of interest to people
16158 debugging compilers. If you are interested in seeing information
16159 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16160 only one message about each such type of problem, no matter how many
16161 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16162 to see how many times the problems occur, with the @code{set
16163 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16166 The messages currently printed, and their meanings, include:
16169 @item inner block not inside outer block in @var{symbol}
16171 The symbol information shows where symbol scopes begin and end
16172 (such as at the start of a function or a block of statements). This
16173 error indicates that an inner scope block is not fully contained
16174 in its outer scope blocks.
16176 @value{GDBN} circumvents the problem by treating the inner block as if it had
16177 the same scope as the outer block. In the error message, @var{symbol}
16178 may be shown as ``@code{(don't know)}'' if the outer block is not a
16181 @item block at @var{address} out of order
16183 The symbol information for symbol scope blocks should occur in
16184 order of increasing addresses. This error indicates that it does not
16187 @value{GDBN} does not circumvent this problem, and has trouble
16188 locating symbols in the source file whose symbols it is reading. (You
16189 can often determine what source file is affected by specifying
16190 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16193 @item bad block start address patched
16195 The symbol information for a symbol scope block has a start address
16196 smaller than the address of the preceding source line. This is known
16197 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16199 @value{GDBN} circumvents the problem by treating the symbol scope block as
16200 starting on the previous source line.
16202 @item bad string table offset in symbol @var{n}
16205 Symbol number @var{n} contains a pointer into the string table which is
16206 larger than the size of the string table.
16208 @value{GDBN} circumvents the problem by considering the symbol to have the
16209 name @code{foo}, which may cause other problems if many symbols end up
16212 @item unknown symbol type @code{0x@var{nn}}
16214 The symbol information contains new data types that @value{GDBN} does
16215 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16216 uncomprehended information, in hexadecimal.
16218 @value{GDBN} circumvents the error by ignoring this symbol information.
16219 This usually allows you to debug your program, though certain symbols
16220 are not accessible. If you encounter such a problem and feel like
16221 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16222 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16223 and examine @code{*bufp} to see the symbol.
16225 @item stub type has NULL name
16227 @value{GDBN} could not find the full definition for a struct or class.
16229 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16230 The symbol information for a C@t{++} member function is missing some
16231 information that recent versions of the compiler should have output for
16234 @item info mismatch between compiler and debugger
16236 @value{GDBN} could not parse a type specification output by the compiler.
16241 @section GDB Data Files
16243 @cindex prefix for data files
16244 @value{GDBN} will sometimes read an auxiliary data file. These files
16245 are kept in a directory known as the @dfn{data directory}.
16247 You can set the data directory's name, and view the name @value{GDBN}
16248 is currently using.
16251 @kindex set data-directory
16252 @item set data-directory @var{directory}
16253 Set the directory which @value{GDBN} searches for auxiliary data files
16254 to @var{directory}.
16256 @kindex show data-directory
16257 @item show data-directory
16258 Show the directory @value{GDBN} searches for auxiliary data files.
16261 @cindex default data directory
16262 @cindex @samp{--with-gdb-datadir}
16263 You can set the default data directory by using the configure-time
16264 @samp{--with-gdb-datadir} option. If the data directory is inside
16265 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16266 @samp{--exec-prefix}), then the default data directory will be updated
16267 automatically if the installed @value{GDBN} is moved to a new
16270 The data directory may also be specified with the
16271 @code{--data-directory} command line option.
16272 @xref{Mode Options}.
16275 @chapter Specifying a Debugging Target
16277 @cindex debugging target
16278 A @dfn{target} is the execution environment occupied by your program.
16280 Often, @value{GDBN} runs in the same host environment as your program;
16281 in that case, the debugging target is specified as a side effect when
16282 you use the @code{file} or @code{core} commands. When you need more
16283 flexibility---for example, running @value{GDBN} on a physically separate
16284 host, or controlling a standalone system over a serial port or a
16285 realtime system over a TCP/IP connection---you can use the @code{target}
16286 command to specify one of the target types configured for @value{GDBN}
16287 (@pxref{Target Commands, ,Commands for Managing Targets}).
16289 @cindex target architecture
16290 It is possible to build @value{GDBN} for several different @dfn{target
16291 architectures}. When @value{GDBN} is built like that, you can choose
16292 one of the available architectures with the @kbd{set architecture}
16296 @kindex set architecture
16297 @kindex show architecture
16298 @item set architecture @var{arch}
16299 This command sets the current target architecture to @var{arch}. The
16300 value of @var{arch} can be @code{"auto"}, in addition to one of the
16301 supported architectures.
16303 @item show architecture
16304 Show the current target architecture.
16306 @item set processor
16308 @kindex set processor
16309 @kindex show processor
16310 These are alias commands for, respectively, @code{set architecture}
16311 and @code{show architecture}.
16315 * Active Targets:: Active targets
16316 * Target Commands:: Commands for managing targets
16317 * Byte Order:: Choosing target byte order
16320 @node Active Targets
16321 @section Active Targets
16323 @cindex stacking targets
16324 @cindex active targets
16325 @cindex multiple targets
16327 There are multiple classes of targets such as: processes, executable files or
16328 recording sessions. Core files belong to the process class, making core file
16329 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16330 on multiple active targets, one in each class. This allows you to (for
16331 example) start a process and inspect its activity, while still having access to
16332 the executable file after the process finishes. Or if you start process
16333 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16334 presented a virtual layer of the recording target, while the process target
16335 remains stopped at the chronologically last point of the process execution.
16337 Use the @code{core-file} and @code{exec-file} commands to select a new core
16338 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16339 specify as a target a process that is already running, use the @code{attach}
16340 command (@pxref{Attach, ,Debugging an Already-running Process}).
16342 @node Target Commands
16343 @section Commands for Managing Targets
16346 @item target @var{type} @var{parameters}
16347 Connects the @value{GDBN} host environment to a target machine or
16348 process. A target is typically a protocol for talking to debugging
16349 facilities. You use the argument @var{type} to specify the type or
16350 protocol of the target machine.
16352 Further @var{parameters} are interpreted by the target protocol, but
16353 typically include things like device names or host names to connect
16354 with, process numbers, and baud rates.
16356 The @code{target} command does not repeat if you press @key{RET} again
16357 after executing the command.
16359 @kindex help target
16361 Displays the names of all targets available. To display targets
16362 currently selected, use either @code{info target} or @code{info files}
16363 (@pxref{Files, ,Commands to Specify Files}).
16365 @item help target @var{name}
16366 Describe a particular target, including any parameters necessary to
16369 @kindex set gnutarget
16370 @item set gnutarget @var{args}
16371 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16372 knows whether it is reading an @dfn{executable},
16373 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16374 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16375 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16378 @emph{Warning:} To specify a file format with @code{set gnutarget},
16379 you must know the actual BFD name.
16383 @xref{Files, , Commands to Specify Files}.
16385 @kindex show gnutarget
16386 @item show gnutarget
16387 Use the @code{show gnutarget} command to display what file format
16388 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16389 @value{GDBN} will determine the file format for each file automatically,
16390 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16393 @cindex common targets
16394 Here are some common targets (available, or not, depending on the GDB
16399 @item target exec @var{program}
16400 @cindex executable file target
16401 An executable file. @samp{target exec @var{program}} is the same as
16402 @samp{exec-file @var{program}}.
16404 @item target core @var{filename}
16405 @cindex core dump file target
16406 A core dump file. @samp{target core @var{filename}} is the same as
16407 @samp{core-file @var{filename}}.
16409 @item target remote @var{medium}
16410 @cindex remote target
16411 A remote system connected to @value{GDBN} via a serial line or network
16412 connection. This command tells @value{GDBN} to use its own remote
16413 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16415 For example, if you have a board connected to @file{/dev/ttya} on the
16416 machine running @value{GDBN}, you could say:
16419 target remote /dev/ttya
16422 @code{target remote} supports the @code{load} command. This is only
16423 useful if you have some other way of getting the stub to the target
16424 system, and you can put it somewhere in memory where it won't get
16425 clobbered by the download.
16427 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16428 @cindex built-in simulator target
16429 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16437 works; however, you cannot assume that a specific memory map, device
16438 drivers, or even basic I/O is available, although some simulators do
16439 provide these. For info about any processor-specific simulator details,
16440 see the appropriate section in @ref{Embedded Processors, ,Embedded
16445 Some configurations may include these targets as well:
16449 @item target nrom @var{dev}
16450 @cindex NetROM ROM emulator target
16451 NetROM ROM emulator. This target only supports downloading.
16455 Different targets are available on different configurations of @value{GDBN};
16456 your configuration may have more or fewer targets.
16458 Many remote targets require you to download the executable's code once
16459 you've successfully established a connection. You may wish to control
16460 various aspects of this process.
16465 @kindex set hash@r{, for remote monitors}
16466 @cindex hash mark while downloading
16467 This command controls whether a hash mark @samp{#} is displayed while
16468 downloading a file to the remote monitor. If on, a hash mark is
16469 displayed after each S-record is successfully downloaded to the
16473 @kindex show hash@r{, for remote monitors}
16474 Show the current status of displaying the hash mark.
16476 @item set debug monitor
16477 @kindex set debug monitor
16478 @cindex display remote monitor communications
16479 Enable or disable display of communications messages between
16480 @value{GDBN} and the remote monitor.
16482 @item show debug monitor
16483 @kindex show debug monitor
16484 Show the current status of displaying communications between
16485 @value{GDBN} and the remote monitor.
16490 @kindex load @var{filename}
16491 @item load @var{filename}
16493 Depending on what remote debugging facilities are configured into
16494 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16495 is meant to make @var{filename} (an executable) available for debugging
16496 on the remote system---by downloading, or dynamic linking, for example.
16497 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16498 the @code{add-symbol-file} command.
16500 If your @value{GDBN} does not have a @code{load} command, attempting to
16501 execute it gets the error message ``@code{You can't do that when your
16502 target is @dots{}}''
16504 The file is loaded at whatever address is specified in the executable.
16505 For some object file formats, you can specify the load address when you
16506 link the program; for other formats, like a.out, the object file format
16507 specifies a fixed address.
16508 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16510 Depending on the remote side capabilities, @value{GDBN} may be able to
16511 load programs into flash memory.
16513 @code{load} does not repeat if you press @key{RET} again after using it.
16517 @section Choosing Target Byte Order
16519 @cindex choosing target byte order
16520 @cindex target byte order
16522 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16523 offer the ability to run either big-endian or little-endian byte
16524 orders. Usually the executable or symbol will include a bit to
16525 designate the endian-ness, and you will not need to worry about
16526 which to use. However, you may still find it useful to adjust
16527 @value{GDBN}'s idea of processor endian-ness manually.
16531 @item set endian big
16532 Instruct @value{GDBN} to assume the target is big-endian.
16534 @item set endian little
16535 Instruct @value{GDBN} to assume the target is little-endian.
16537 @item set endian auto
16538 Instruct @value{GDBN} to use the byte order associated with the
16542 Display @value{GDBN}'s current idea of the target byte order.
16546 Note that these commands merely adjust interpretation of symbolic
16547 data on the host, and that they have absolutely no effect on the
16551 @node Remote Debugging
16552 @chapter Debugging Remote Programs
16553 @cindex remote debugging
16555 If you are trying to debug a program running on a machine that cannot run
16556 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16557 For example, you might use remote debugging on an operating system kernel,
16558 or on a small system which does not have a general purpose operating system
16559 powerful enough to run a full-featured debugger.
16561 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16562 to make this work with particular debugging targets. In addition,
16563 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16564 but not specific to any particular target system) which you can use if you
16565 write the remote stubs---the code that runs on the remote system to
16566 communicate with @value{GDBN}.
16568 Other remote targets may be available in your
16569 configuration of @value{GDBN}; use @code{help target} to list them.
16572 * Connecting:: Connecting to a remote target
16573 * File Transfer:: Sending files to a remote system
16574 * Server:: Using the gdbserver program
16575 * Remote Configuration:: Remote configuration
16576 * Remote Stub:: Implementing a remote stub
16580 @section Connecting to a Remote Target
16582 On the @value{GDBN} host machine, you will need an unstripped copy of
16583 your program, since @value{GDBN} needs symbol and debugging information.
16584 Start up @value{GDBN} as usual, using the name of the local copy of your
16585 program as the first argument.
16587 @cindex @code{target remote}
16588 @value{GDBN} can communicate with the target over a serial line, or
16589 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16590 each case, @value{GDBN} uses the same protocol for debugging your
16591 program; only the medium carrying the debugging packets varies. The
16592 @code{target remote} command establishes a connection to the target.
16593 Its arguments indicate which medium to use:
16597 @item target remote @var{serial-device}
16598 @cindex serial line, @code{target remote}
16599 Use @var{serial-device} to communicate with the target. For example,
16600 to use a serial line connected to the device named @file{/dev/ttyb}:
16603 target remote /dev/ttyb
16606 If you're using a serial line, you may want to give @value{GDBN} the
16607 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16608 (@pxref{Remote Configuration, set remotebaud}) before the
16609 @code{target} command.
16611 @item target remote @code{@var{host}:@var{port}}
16612 @itemx target remote @code{tcp:@var{host}:@var{port}}
16613 @cindex @acronym{TCP} port, @code{target remote}
16614 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16615 The @var{host} may be either a host name or a numeric @acronym{IP}
16616 address; @var{port} must be a decimal number. The @var{host} could be
16617 the target machine itself, if it is directly connected to the net, or
16618 it might be a terminal server which in turn has a serial line to the
16621 For example, to connect to port 2828 on a terminal server named
16625 target remote manyfarms:2828
16628 If your remote target is actually running on the same machine as your
16629 debugger session (e.g.@: a simulator for your target running on the
16630 same host), you can omit the hostname. For example, to connect to
16631 port 1234 on your local machine:
16634 target remote :1234
16638 Note that the colon is still required here.
16640 @item target remote @code{udp:@var{host}:@var{port}}
16641 @cindex @acronym{UDP} port, @code{target remote}
16642 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16643 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16646 target remote udp:manyfarms:2828
16649 When using a @acronym{UDP} connection for remote debugging, you should
16650 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16651 can silently drop packets on busy or unreliable networks, which will
16652 cause havoc with your debugging session.
16654 @item target remote | @var{command}
16655 @cindex pipe, @code{target remote} to
16656 Run @var{command} in the background and communicate with it using a
16657 pipe. The @var{command} is a shell command, to be parsed and expanded
16658 by the system's command shell, @code{/bin/sh}; it should expect remote
16659 protocol packets on its standard input, and send replies on its
16660 standard output. You could use this to run a stand-alone simulator
16661 that speaks the remote debugging protocol, to make net connections
16662 using programs like @code{ssh}, or for other similar tricks.
16664 If @var{command} closes its standard output (perhaps by exiting),
16665 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16666 program has already exited, this will have no effect.)
16670 Once the connection has been established, you can use all the usual
16671 commands to examine and change data. The remote program is already
16672 running; you can use @kbd{step} and @kbd{continue}, and you do not
16673 need to use @kbd{run}.
16675 @cindex interrupting remote programs
16676 @cindex remote programs, interrupting
16677 Whenever @value{GDBN} is waiting for the remote program, if you type the
16678 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16679 program. This may or may not succeed, depending in part on the hardware
16680 and the serial drivers the remote system uses. If you type the
16681 interrupt character once again, @value{GDBN} displays this prompt:
16684 Interrupted while waiting for the program.
16685 Give up (and stop debugging it)? (y or n)
16688 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16689 (If you decide you want to try again later, you can use @samp{target
16690 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16691 goes back to waiting.
16694 @kindex detach (remote)
16696 When you have finished debugging the remote program, you can use the
16697 @code{detach} command to release it from @value{GDBN} control.
16698 Detaching from the target normally resumes its execution, but the results
16699 will depend on your particular remote stub. After the @code{detach}
16700 command, @value{GDBN} is free to connect to another target.
16704 The @code{disconnect} command behaves like @code{detach}, except that
16705 the target is generally not resumed. It will wait for @value{GDBN}
16706 (this instance or another one) to connect and continue debugging. After
16707 the @code{disconnect} command, @value{GDBN} is again free to connect to
16710 @cindex send command to remote monitor
16711 @cindex extend @value{GDBN} for remote targets
16712 @cindex add new commands for external monitor
16714 @item monitor @var{cmd}
16715 This command allows you to send arbitrary commands directly to the
16716 remote monitor. Since @value{GDBN} doesn't care about the commands it
16717 sends like this, this command is the way to extend @value{GDBN}---you
16718 can add new commands that only the external monitor will understand
16722 @node File Transfer
16723 @section Sending files to a remote system
16724 @cindex remote target, file transfer
16725 @cindex file transfer
16726 @cindex sending files to remote systems
16728 Some remote targets offer the ability to transfer files over the same
16729 connection used to communicate with @value{GDBN}. This is convenient
16730 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16731 running @code{gdbserver} over a network interface. For other targets,
16732 e.g.@: embedded devices with only a single serial port, this may be
16733 the only way to upload or download files.
16735 Not all remote targets support these commands.
16739 @item remote put @var{hostfile} @var{targetfile}
16740 Copy file @var{hostfile} from the host system (the machine running
16741 @value{GDBN}) to @var{targetfile} on the target system.
16744 @item remote get @var{targetfile} @var{hostfile}
16745 Copy file @var{targetfile} from the target system to @var{hostfile}
16746 on the host system.
16748 @kindex remote delete
16749 @item remote delete @var{targetfile}
16750 Delete @var{targetfile} from the target system.
16755 @section Using the @code{gdbserver} Program
16758 @cindex remote connection without stubs
16759 @code{gdbserver} is a control program for Unix-like systems, which
16760 allows you to connect your program with a remote @value{GDBN} via
16761 @code{target remote}---but without linking in the usual debugging stub.
16763 @code{gdbserver} is not a complete replacement for the debugging stubs,
16764 because it requires essentially the same operating-system facilities
16765 that @value{GDBN} itself does. In fact, a system that can run
16766 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16767 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16768 because it is a much smaller program than @value{GDBN} itself. It is
16769 also easier to port than all of @value{GDBN}, so you may be able to get
16770 started more quickly on a new system by using @code{gdbserver}.
16771 Finally, if you develop code for real-time systems, you may find that
16772 the tradeoffs involved in real-time operation make it more convenient to
16773 do as much development work as possible on another system, for example
16774 by cross-compiling. You can use @code{gdbserver} to make a similar
16775 choice for debugging.
16777 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16778 or a TCP connection, using the standard @value{GDBN} remote serial
16782 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16783 Do not run @code{gdbserver} connected to any public network; a
16784 @value{GDBN} connection to @code{gdbserver} provides access to the
16785 target system with the same privileges as the user running
16789 @subsection Running @code{gdbserver}
16790 @cindex arguments, to @code{gdbserver}
16791 @cindex @code{gdbserver}, command-line arguments
16793 Run @code{gdbserver} on the target system. You need a copy of the
16794 program you want to debug, including any libraries it requires.
16795 @code{gdbserver} does not need your program's symbol table, so you can
16796 strip the program if necessary to save space. @value{GDBN} on the host
16797 system does all the symbol handling.
16799 To use the server, you must tell it how to communicate with @value{GDBN};
16800 the name of your program; and the arguments for your program. The usual
16804 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16807 @var{comm} is either a device name (to use a serial line), or a TCP
16808 hostname and portnumber, or @code{-} or @code{stdio} to use
16809 stdin/stdout of @code{gdbserver}.
16810 For example, to debug Emacs with the argument
16811 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16815 target> gdbserver /dev/com1 emacs foo.txt
16818 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16821 To use a TCP connection instead of a serial line:
16824 target> gdbserver host:2345 emacs foo.txt
16827 The only difference from the previous example is the first argument,
16828 specifying that you are communicating with the host @value{GDBN} via
16829 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16830 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16831 (Currently, the @samp{host} part is ignored.) You can choose any number
16832 you want for the port number as long as it does not conflict with any
16833 TCP ports already in use on the target system (for example, @code{23} is
16834 reserved for @code{telnet}).@footnote{If you choose a port number that
16835 conflicts with another service, @code{gdbserver} prints an error message
16836 and exits.} You must use the same port number with the host @value{GDBN}
16837 @code{target remote} command.
16839 The @code{stdio} connection is useful when starting @code{gdbserver}
16843 (gdb) target remote | ssh -T hostname gdbserver - hello
16846 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16847 and we don't want escape-character handling. Ssh does this by default when
16848 a command is provided, the flag is provided to make it explicit.
16849 You could elide it if you want to.
16851 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16852 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16853 display through a pipe connected to gdbserver.
16854 Both @code{stdout} and @code{stderr} use the same pipe.
16856 @subsubsection Attaching to a Running Program
16857 @cindex attach to a program, @code{gdbserver}
16858 @cindex @option{--attach}, @code{gdbserver} option
16860 On some targets, @code{gdbserver} can also attach to running programs.
16861 This is accomplished via the @code{--attach} argument. The syntax is:
16864 target> gdbserver --attach @var{comm} @var{pid}
16867 @var{pid} is the process ID of a currently running process. It isn't necessary
16868 to point @code{gdbserver} at a binary for the running process.
16871 You can debug processes by name instead of process ID if your target has the
16872 @code{pidof} utility:
16875 target> gdbserver --attach @var{comm} `pidof @var{program}`
16878 In case more than one copy of @var{program} is running, or @var{program}
16879 has multiple threads, most versions of @code{pidof} support the
16880 @code{-s} option to only return the first process ID.
16882 @subsubsection Multi-Process Mode for @code{gdbserver}
16883 @cindex @code{gdbserver}, multiple processes
16884 @cindex multiple processes with @code{gdbserver}
16886 When you connect to @code{gdbserver} using @code{target remote},
16887 @code{gdbserver} debugs the specified program only once. When the
16888 program exits, or you detach from it, @value{GDBN} closes the connection
16889 and @code{gdbserver} exits.
16891 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16892 enters multi-process mode. When the debugged program exits, or you
16893 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16894 though no program is running. The @code{run} and @code{attach}
16895 commands instruct @code{gdbserver} to run or attach to a new program.
16896 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16897 remote exec-file}) to select the program to run. Command line
16898 arguments are supported, except for wildcard expansion and I/O
16899 redirection (@pxref{Arguments}).
16901 @cindex @option{--multi}, @code{gdbserver} option
16902 To start @code{gdbserver} without supplying an initial command to run
16903 or process ID to attach, use the @option{--multi} command line option.
16904 Then you can connect using @kbd{target extended-remote} and start
16905 the program you want to debug.
16907 In multi-process mode @code{gdbserver} does not automatically exit unless you
16908 use the option @option{--once}. You can terminate it by using
16909 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16910 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16911 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16912 @option{--multi} option to @code{gdbserver} has no influence on that.
16914 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16916 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16918 @code{gdbserver} normally terminates after all of its debugged processes have
16919 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16920 extended-remote}, @code{gdbserver} stays running even with no processes left.
16921 @value{GDBN} normally terminates the spawned debugged process on its exit,
16922 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16923 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16924 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16925 stays running even in the @kbd{target remote} mode.
16927 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16928 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16929 completeness, at most one @value{GDBN} can be connected at a time.
16931 @cindex @option{--once}, @code{gdbserver} option
16932 By default, @code{gdbserver} keeps the listening TCP port open, so that
16933 additional connections are possible. However, if you start @code{gdbserver}
16934 with the @option{--once} option, it will stop listening for any further
16935 connection attempts after connecting to the first @value{GDBN} session. This
16936 means no further connections to @code{gdbserver} will be possible after the
16937 first one. It also means @code{gdbserver} will terminate after the first
16938 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16939 connections and even in the @kbd{target extended-remote} mode. The
16940 @option{--once} option allows reusing the same port number for connecting to
16941 multiple instances of @code{gdbserver} running on the same host, since each
16942 instance closes its port after the first connection.
16944 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16946 @cindex @option{--debug}, @code{gdbserver} option
16947 The @option{--debug} option tells @code{gdbserver} to display extra
16948 status information about the debugging process.
16949 @cindex @option{--remote-debug}, @code{gdbserver} option
16950 The @option{--remote-debug} option tells @code{gdbserver} to display
16951 remote protocol debug output. These options are intended for
16952 @code{gdbserver} development and for bug reports to the developers.
16954 @cindex @option{--wrapper}, @code{gdbserver} option
16955 The @option{--wrapper} option specifies a wrapper to launch programs
16956 for debugging. The option should be followed by the name of the
16957 wrapper, then any command-line arguments to pass to the wrapper, then
16958 @kbd{--} indicating the end of the wrapper arguments.
16960 @code{gdbserver} runs the specified wrapper program with a combined
16961 command line including the wrapper arguments, then the name of the
16962 program to debug, then any arguments to the program. The wrapper
16963 runs until it executes your program, and then @value{GDBN} gains control.
16965 You can use any program that eventually calls @code{execve} with
16966 its arguments as a wrapper. Several standard Unix utilities do
16967 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16968 with @code{exec "$@@"} will also work.
16970 For example, you can use @code{env} to pass an environment variable to
16971 the debugged program, without setting the variable in @code{gdbserver}'s
16975 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16978 @subsection Connecting to @code{gdbserver}
16980 Run @value{GDBN} on the host system.
16982 First make sure you have the necessary symbol files. Load symbols for
16983 your application using the @code{file} command before you connect. Use
16984 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16985 was compiled with the correct sysroot using @code{--with-sysroot}).
16987 The symbol file and target libraries must exactly match the executable
16988 and libraries on the target, with one exception: the files on the host
16989 system should not be stripped, even if the files on the target system
16990 are. Mismatched or missing files will lead to confusing results
16991 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16992 files may also prevent @code{gdbserver} from debugging multi-threaded
16995 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16996 For TCP connections, you must start up @code{gdbserver} prior to using
16997 the @code{target remote} command. Otherwise you may get an error whose
16998 text depends on the host system, but which usually looks something like
16999 @samp{Connection refused}. Don't use the @code{load}
17000 command in @value{GDBN} when using @code{gdbserver}, since the program is
17001 already on the target.
17003 @subsection Monitor Commands for @code{gdbserver}
17004 @cindex monitor commands, for @code{gdbserver}
17005 @anchor{Monitor Commands for gdbserver}
17007 During a @value{GDBN} session using @code{gdbserver}, you can use the
17008 @code{monitor} command to send special requests to @code{gdbserver}.
17009 Here are the available commands.
17013 List the available monitor commands.
17015 @item monitor set debug 0
17016 @itemx monitor set debug 1
17017 Disable or enable general debugging messages.
17019 @item monitor set remote-debug 0
17020 @itemx monitor set remote-debug 1
17021 Disable or enable specific debugging messages associated with the remote
17022 protocol (@pxref{Remote Protocol}).
17024 @item monitor set libthread-db-search-path [PATH]
17025 @cindex gdbserver, search path for @code{libthread_db}
17026 When this command is issued, @var{path} is a colon-separated list of
17027 directories to search for @code{libthread_db} (@pxref{Threads,,set
17028 libthread-db-search-path}). If you omit @var{path},
17029 @samp{libthread-db-search-path} will be reset to its default value.
17031 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17032 not supported in @code{gdbserver}.
17035 Tell gdbserver to exit immediately. This command should be followed by
17036 @code{disconnect} to close the debugging session. @code{gdbserver} will
17037 detach from any attached processes and kill any processes it created.
17038 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17039 of a multi-process mode debug session.
17043 @subsection Tracepoints support in @code{gdbserver}
17044 @cindex tracepoints support in @code{gdbserver}
17046 On some targets, @code{gdbserver} supports tracepoints, fast
17047 tracepoints and static tracepoints.
17049 For fast or static tracepoints to work, a special library called the
17050 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17051 This library is built and distributed as an integral part of
17052 @code{gdbserver}. In addition, support for static tracepoints
17053 requires building the in-process agent library with static tracepoints
17054 support. At present, the UST (LTTng Userspace Tracer,
17055 @url{http://lttng.org/ust}) tracing engine is supported. This support
17056 is automatically available if UST development headers are found in the
17057 standard include path when @code{gdbserver} is built, or if
17058 @code{gdbserver} was explicitly configured using @option{--with-ust}
17059 to point at such headers. You can explicitly disable the support
17060 using @option{--with-ust=no}.
17062 There are several ways to load the in-process agent in your program:
17065 @item Specifying it as dependency at link time
17067 You can link your program dynamically with the in-process agent
17068 library. On most systems, this is accomplished by adding
17069 @code{-linproctrace} to the link command.
17071 @item Using the system's preloading mechanisms
17073 You can force loading the in-process agent at startup time by using
17074 your system's support for preloading shared libraries. Many Unixes
17075 support the concept of preloading user defined libraries. In most
17076 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17077 in the environment. See also the description of @code{gdbserver}'s
17078 @option{--wrapper} command line option.
17080 @item Using @value{GDBN} to force loading the agent at run time
17082 On some systems, you can force the inferior to load a shared library,
17083 by calling a dynamic loader function in the inferior that takes care
17084 of dynamically looking up and loading a shared library. On most Unix
17085 systems, the function is @code{dlopen}. You'll use the @code{call}
17086 command for that. For example:
17089 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17092 Note that on most Unix systems, for the @code{dlopen} function to be
17093 available, the program needs to be linked with @code{-ldl}.
17096 On systems that have a userspace dynamic loader, like most Unix
17097 systems, when you connect to @code{gdbserver} using @code{target
17098 remote}, you'll find that the program is stopped at the dynamic
17099 loader's entry point, and no shared library has been loaded in the
17100 program's address space yet, including the in-process agent. In that
17101 case, before being able to use any of the fast or static tracepoints
17102 features, you need to let the loader run and load the shared
17103 libraries. The simplest way to do that is to run the program to the
17104 main procedure. E.g., if debugging a C or C@t{++} program, start
17105 @code{gdbserver} like so:
17108 $ gdbserver :9999 myprogram
17111 Start GDB and connect to @code{gdbserver} like so, and run to main:
17115 (@value{GDBP}) target remote myhost:9999
17116 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17117 (@value{GDBP}) b main
17118 (@value{GDBP}) continue
17121 The in-process tracing agent library should now be loaded into the
17122 process; you can confirm it with the @code{info sharedlibrary}
17123 command, which will list @file{libinproctrace.so} as loaded in the
17124 process. You are now ready to install fast tracepoints, list static
17125 tracepoint markers, probe static tracepoints markers, and start
17128 @node Remote Configuration
17129 @section Remote Configuration
17132 @kindex show remote
17133 This section documents the configuration options available when
17134 debugging remote programs. For the options related to the File I/O
17135 extensions of the remote protocol, see @ref{system,
17136 system-call-allowed}.
17139 @item set remoteaddresssize @var{bits}
17140 @cindex address size for remote targets
17141 @cindex bits in remote address
17142 Set the maximum size of address in a memory packet to the specified
17143 number of bits. @value{GDBN} will mask off the address bits above
17144 that number, when it passes addresses to the remote target. The
17145 default value is the number of bits in the target's address.
17147 @item show remoteaddresssize
17148 Show the current value of remote address size in bits.
17150 @item set remotebaud @var{n}
17151 @cindex baud rate for remote targets
17152 Set the baud rate for the remote serial I/O to @var{n} baud. The
17153 value is used to set the speed of the serial port used for debugging
17156 @item show remotebaud
17157 Show the current speed of the remote connection.
17159 @item set remotebreak
17160 @cindex interrupt remote programs
17161 @cindex BREAK signal instead of Ctrl-C
17162 @anchor{set remotebreak}
17163 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17164 when you type @kbd{Ctrl-c} to interrupt the program running
17165 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17166 character instead. The default is off, since most remote systems
17167 expect to see @samp{Ctrl-C} as the interrupt signal.
17169 @item show remotebreak
17170 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17171 interrupt the remote program.
17173 @item set remoteflow on
17174 @itemx set remoteflow off
17175 @kindex set remoteflow
17176 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17177 on the serial port used to communicate to the remote target.
17179 @item show remoteflow
17180 @kindex show remoteflow
17181 Show the current setting of hardware flow control.
17183 @item set remotelogbase @var{base}
17184 Set the base (a.k.a.@: radix) of logging serial protocol
17185 communications to @var{base}. Supported values of @var{base} are:
17186 @code{ascii}, @code{octal}, and @code{hex}. The default is
17189 @item show remotelogbase
17190 Show the current setting of the radix for logging remote serial
17193 @item set remotelogfile @var{file}
17194 @cindex record serial communications on file
17195 Record remote serial communications on the named @var{file}. The
17196 default is not to record at all.
17198 @item show remotelogfile.
17199 Show the current setting of the file name on which to record the
17200 serial communications.
17202 @item set remotetimeout @var{num}
17203 @cindex timeout for serial communications
17204 @cindex remote timeout
17205 Set the timeout limit to wait for the remote target to respond to
17206 @var{num} seconds. The default is 2 seconds.
17208 @item show remotetimeout
17209 Show the current number of seconds to wait for the remote target
17212 @cindex limit hardware breakpoints and watchpoints
17213 @cindex remote target, limit break- and watchpoints
17214 @anchor{set remote hardware-watchpoint-limit}
17215 @anchor{set remote hardware-breakpoint-limit}
17216 @item set remote hardware-watchpoint-limit @var{limit}
17217 @itemx set remote hardware-breakpoint-limit @var{limit}
17218 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17219 watchpoints. A limit of -1, the default, is treated as unlimited.
17221 @cindex limit hardware watchpoints length
17222 @cindex remote target, limit watchpoints length
17223 @anchor{set remote hardware-watchpoint-length-limit}
17224 @item set remote hardware-watchpoint-length-limit @var{limit}
17225 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17226 a remote hardware watchpoint. A limit of -1, the default, is treated
17229 @item show remote hardware-watchpoint-length-limit
17230 Show the current limit (in bytes) of the maximum length of
17231 a remote hardware watchpoint.
17233 @item set remote exec-file @var{filename}
17234 @itemx show remote exec-file
17235 @anchor{set remote exec-file}
17236 @cindex executable file, for remote target
17237 Select the file used for @code{run} with @code{target
17238 extended-remote}. This should be set to a filename valid on the
17239 target system. If it is not set, the target will use a default
17240 filename (e.g.@: the last program run).
17242 @item set remote interrupt-sequence
17243 @cindex interrupt remote programs
17244 @cindex select Ctrl-C, BREAK or BREAK-g
17245 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17246 @samp{BREAK-g} as the
17247 sequence to the remote target in order to interrupt the execution.
17248 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17249 is high level of serial line for some certain time.
17250 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17251 It is @code{BREAK} signal followed by character @code{g}.
17253 @item show interrupt-sequence
17254 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17255 is sent by @value{GDBN} to interrupt the remote program.
17256 @code{BREAK-g} is BREAK signal followed by @code{g} and
17257 also known as Magic SysRq g.
17259 @item set remote interrupt-on-connect
17260 @cindex send interrupt-sequence on start
17261 Specify whether interrupt-sequence is sent to remote target when
17262 @value{GDBN} connects to it. This is mostly needed when you debug
17263 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17264 which is known as Magic SysRq g in order to connect @value{GDBN}.
17266 @item show interrupt-on-connect
17267 Show whether interrupt-sequence is sent
17268 to remote target when @value{GDBN} connects to it.
17272 @item set tcp auto-retry on
17273 @cindex auto-retry, for remote TCP target
17274 Enable auto-retry for remote TCP connections. This is useful if the remote
17275 debugging agent is launched in parallel with @value{GDBN}; there is a race
17276 condition because the agent may not become ready to accept the connection
17277 before @value{GDBN} attempts to connect. When auto-retry is
17278 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17279 to establish the connection using the timeout specified by
17280 @code{set tcp connect-timeout}.
17282 @item set tcp auto-retry off
17283 Do not auto-retry failed TCP connections.
17285 @item show tcp auto-retry
17286 Show the current auto-retry setting.
17288 @item set tcp connect-timeout @var{seconds}
17289 @cindex connection timeout, for remote TCP target
17290 @cindex timeout, for remote target connection
17291 Set the timeout for establishing a TCP connection to the remote target to
17292 @var{seconds}. The timeout affects both polling to retry failed connections
17293 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17294 that are merely slow to complete, and represents an approximate cumulative
17297 @item show tcp connect-timeout
17298 Show the current connection timeout setting.
17301 @cindex remote packets, enabling and disabling
17302 The @value{GDBN} remote protocol autodetects the packets supported by
17303 your debugging stub. If you need to override the autodetection, you
17304 can use these commands to enable or disable individual packets. Each
17305 packet can be set to @samp{on} (the remote target supports this
17306 packet), @samp{off} (the remote target does not support this packet),
17307 or @samp{auto} (detect remote target support for this packet). They
17308 all default to @samp{auto}. For more information about each packet,
17309 see @ref{Remote Protocol}.
17311 During normal use, you should not have to use any of these commands.
17312 If you do, that may be a bug in your remote debugging stub, or a bug
17313 in @value{GDBN}. You may want to report the problem to the
17314 @value{GDBN} developers.
17316 For each packet @var{name}, the command to enable or disable the
17317 packet is @code{set remote @var{name}-packet}. The available settings
17320 @multitable @columnfractions 0.28 0.32 0.25
17323 @tab Related Features
17325 @item @code{fetch-register}
17327 @tab @code{info registers}
17329 @item @code{set-register}
17333 @item @code{binary-download}
17335 @tab @code{load}, @code{set}
17337 @item @code{read-aux-vector}
17338 @tab @code{qXfer:auxv:read}
17339 @tab @code{info auxv}
17341 @item @code{symbol-lookup}
17342 @tab @code{qSymbol}
17343 @tab Detecting multiple threads
17345 @item @code{attach}
17346 @tab @code{vAttach}
17349 @item @code{verbose-resume}
17351 @tab Stepping or resuming multiple threads
17357 @item @code{software-breakpoint}
17361 @item @code{hardware-breakpoint}
17365 @item @code{write-watchpoint}
17369 @item @code{read-watchpoint}
17373 @item @code{access-watchpoint}
17377 @item @code{target-features}
17378 @tab @code{qXfer:features:read}
17379 @tab @code{set architecture}
17381 @item @code{library-info}
17382 @tab @code{qXfer:libraries:read}
17383 @tab @code{info sharedlibrary}
17385 @item @code{memory-map}
17386 @tab @code{qXfer:memory-map:read}
17387 @tab @code{info mem}
17389 @item @code{read-sdata-object}
17390 @tab @code{qXfer:sdata:read}
17391 @tab @code{print $_sdata}
17393 @item @code{read-spu-object}
17394 @tab @code{qXfer:spu:read}
17395 @tab @code{info spu}
17397 @item @code{write-spu-object}
17398 @tab @code{qXfer:spu:write}
17399 @tab @code{info spu}
17401 @item @code{read-siginfo-object}
17402 @tab @code{qXfer:siginfo:read}
17403 @tab @code{print $_siginfo}
17405 @item @code{write-siginfo-object}
17406 @tab @code{qXfer:siginfo:write}
17407 @tab @code{set $_siginfo}
17409 @item @code{threads}
17410 @tab @code{qXfer:threads:read}
17411 @tab @code{info threads}
17413 @item @code{get-thread-local-@*storage-address}
17414 @tab @code{qGetTLSAddr}
17415 @tab Displaying @code{__thread} variables
17417 @item @code{get-thread-information-block-address}
17418 @tab @code{qGetTIBAddr}
17419 @tab Display MS-Windows Thread Information Block.
17421 @item @code{search-memory}
17422 @tab @code{qSearch:memory}
17425 @item @code{supported-packets}
17426 @tab @code{qSupported}
17427 @tab Remote communications parameters
17429 @item @code{pass-signals}
17430 @tab @code{QPassSignals}
17431 @tab @code{handle @var{signal}}
17433 @item @code{hostio-close-packet}
17434 @tab @code{vFile:close}
17435 @tab @code{remote get}, @code{remote put}
17437 @item @code{hostio-open-packet}
17438 @tab @code{vFile:open}
17439 @tab @code{remote get}, @code{remote put}
17441 @item @code{hostio-pread-packet}
17442 @tab @code{vFile:pread}
17443 @tab @code{remote get}, @code{remote put}
17445 @item @code{hostio-pwrite-packet}
17446 @tab @code{vFile:pwrite}
17447 @tab @code{remote get}, @code{remote put}
17449 @item @code{hostio-unlink-packet}
17450 @tab @code{vFile:unlink}
17451 @tab @code{remote delete}
17453 @item @code{noack-packet}
17454 @tab @code{QStartNoAckMode}
17455 @tab Packet acknowledgment
17457 @item @code{osdata}
17458 @tab @code{qXfer:osdata:read}
17459 @tab @code{info os}
17461 @item @code{query-attached}
17462 @tab @code{qAttached}
17463 @tab Querying remote process attach state.
17465 @item @code{traceframe-info}
17466 @tab @code{qXfer:traceframe-info:read}
17467 @tab Traceframe info
17469 @item @code{install-in-trace}
17470 @tab @code{InstallInTrace}
17471 @tab Install tracepoint in tracing
17473 @item @code{disable-randomization}
17474 @tab @code{QDisableRandomization}
17475 @tab @code{set disable-randomization}
17479 @section Implementing a Remote Stub
17481 @cindex debugging stub, example
17482 @cindex remote stub, example
17483 @cindex stub example, remote debugging
17484 The stub files provided with @value{GDBN} implement the target side of the
17485 communication protocol, and the @value{GDBN} side is implemented in the
17486 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17487 these subroutines to communicate, and ignore the details. (If you're
17488 implementing your own stub file, you can still ignore the details: start
17489 with one of the existing stub files. @file{sparc-stub.c} is the best
17490 organized, and therefore the easiest to read.)
17492 @cindex remote serial debugging, overview
17493 To debug a program running on another machine (the debugging
17494 @dfn{target} machine), you must first arrange for all the usual
17495 prerequisites for the program to run by itself. For example, for a C
17500 A startup routine to set up the C runtime environment; these usually
17501 have a name like @file{crt0}. The startup routine may be supplied by
17502 your hardware supplier, or you may have to write your own.
17505 A C subroutine library to support your program's
17506 subroutine calls, notably managing input and output.
17509 A way of getting your program to the other machine---for example, a
17510 download program. These are often supplied by the hardware
17511 manufacturer, but you may have to write your own from hardware
17515 The next step is to arrange for your program to use a serial port to
17516 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17517 machine). In general terms, the scheme looks like this:
17521 @value{GDBN} already understands how to use this protocol; when everything
17522 else is set up, you can simply use the @samp{target remote} command
17523 (@pxref{Targets,,Specifying a Debugging Target}).
17525 @item On the target,
17526 you must link with your program a few special-purpose subroutines that
17527 implement the @value{GDBN} remote serial protocol. The file containing these
17528 subroutines is called a @dfn{debugging stub}.
17530 On certain remote targets, you can use an auxiliary program
17531 @code{gdbserver} instead of linking a stub into your program.
17532 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17535 The debugging stub is specific to the architecture of the remote
17536 machine; for example, use @file{sparc-stub.c} to debug programs on
17539 @cindex remote serial stub list
17540 These working remote stubs are distributed with @value{GDBN}:
17545 @cindex @file{i386-stub.c}
17548 For Intel 386 and compatible architectures.
17551 @cindex @file{m68k-stub.c}
17552 @cindex Motorola 680x0
17554 For Motorola 680x0 architectures.
17557 @cindex @file{sh-stub.c}
17560 For Renesas SH architectures.
17563 @cindex @file{sparc-stub.c}
17565 For @sc{sparc} architectures.
17567 @item sparcl-stub.c
17568 @cindex @file{sparcl-stub.c}
17571 For Fujitsu @sc{sparclite} architectures.
17575 The @file{README} file in the @value{GDBN} distribution may list other
17576 recently added stubs.
17579 * Stub Contents:: What the stub can do for you
17580 * Bootstrapping:: What you must do for the stub
17581 * Debug Session:: Putting it all together
17584 @node Stub Contents
17585 @subsection What the Stub Can Do for You
17587 @cindex remote serial stub
17588 The debugging stub for your architecture supplies these three
17592 @item set_debug_traps
17593 @findex set_debug_traps
17594 @cindex remote serial stub, initialization
17595 This routine arranges for @code{handle_exception} to run when your
17596 program stops. You must call this subroutine explicitly in your
17597 program's startup code.
17599 @item handle_exception
17600 @findex handle_exception
17601 @cindex remote serial stub, main routine
17602 This is the central workhorse, but your program never calls it
17603 explicitly---the setup code arranges for @code{handle_exception} to
17604 run when a trap is triggered.
17606 @code{handle_exception} takes control when your program stops during
17607 execution (for example, on a breakpoint), and mediates communications
17608 with @value{GDBN} on the host machine. This is where the communications
17609 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17610 representative on the target machine. It begins by sending summary
17611 information on the state of your program, then continues to execute,
17612 retrieving and transmitting any information @value{GDBN} needs, until you
17613 execute a @value{GDBN} command that makes your program resume; at that point,
17614 @code{handle_exception} returns control to your own code on the target
17618 @cindex @code{breakpoint} subroutine, remote
17619 Use this auxiliary subroutine to make your program contain a
17620 breakpoint. Depending on the particular situation, this may be the only
17621 way for @value{GDBN} to get control. For instance, if your target
17622 machine has some sort of interrupt button, you won't need to call this;
17623 pressing the interrupt button transfers control to
17624 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17625 simply receiving characters on the serial port may also trigger a trap;
17626 again, in that situation, you don't need to call @code{breakpoint} from
17627 your own program---simply running @samp{target remote} from the host
17628 @value{GDBN} session gets control.
17630 Call @code{breakpoint} if none of these is true, or if you simply want
17631 to make certain your program stops at a predetermined point for the
17632 start of your debugging session.
17635 @node Bootstrapping
17636 @subsection What You Must Do for the Stub
17638 @cindex remote stub, support routines
17639 The debugging stubs that come with @value{GDBN} are set up for a particular
17640 chip architecture, but they have no information about the rest of your
17641 debugging target machine.
17643 First of all you need to tell the stub how to communicate with the
17647 @item int getDebugChar()
17648 @findex getDebugChar
17649 Write this subroutine to read a single character from the serial port.
17650 It may be identical to @code{getchar} for your target system; a
17651 different name is used to allow you to distinguish the two if you wish.
17653 @item void putDebugChar(int)
17654 @findex putDebugChar
17655 Write this subroutine to write a single character to the serial port.
17656 It may be identical to @code{putchar} for your target system; a
17657 different name is used to allow you to distinguish the two if you wish.
17660 @cindex control C, and remote debugging
17661 @cindex interrupting remote targets
17662 If you want @value{GDBN} to be able to stop your program while it is
17663 running, you need to use an interrupt-driven serial driver, and arrange
17664 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17665 character). That is the character which @value{GDBN} uses to tell the
17666 remote system to stop.
17668 Getting the debugging target to return the proper status to @value{GDBN}
17669 probably requires changes to the standard stub; one quick and dirty way
17670 is to just execute a breakpoint instruction (the ``dirty'' part is that
17671 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17673 Other routines you need to supply are:
17676 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17677 @findex exceptionHandler
17678 Write this function to install @var{exception_address} in the exception
17679 handling tables. You need to do this because the stub does not have any
17680 way of knowing what the exception handling tables on your target system
17681 are like (for example, the processor's table might be in @sc{rom},
17682 containing entries which point to a table in @sc{ram}).
17683 @var{exception_number} is the exception number which should be changed;
17684 its meaning is architecture-dependent (for example, different numbers
17685 might represent divide by zero, misaligned access, etc). When this
17686 exception occurs, control should be transferred directly to
17687 @var{exception_address}, and the processor state (stack, registers,
17688 and so on) should be just as it is when a processor exception occurs. So if
17689 you want to use a jump instruction to reach @var{exception_address}, it
17690 should be a simple jump, not a jump to subroutine.
17692 For the 386, @var{exception_address} should be installed as an interrupt
17693 gate so that interrupts are masked while the handler runs. The gate
17694 should be at privilege level 0 (the most privileged level). The
17695 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17696 help from @code{exceptionHandler}.
17698 @item void flush_i_cache()
17699 @findex flush_i_cache
17700 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17701 instruction cache, if any, on your target machine. If there is no
17702 instruction cache, this subroutine may be a no-op.
17704 On target machines that have instruction caches, @value{GDBN} requires this
17705 function to make certain that the state of your program is stable.
17709 You must also make sure this library routine is available:
17712 @item void *memset(void *, int, int)
17714 This is the standard library function @code{memset} that sets an area of
17715 memory to a known value. If you have one of the free versions of
17716 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17717 either obtain it from your hardware manufacturer, or write your own.
17720 If you do not use the GNU C compiler, you may need other standard
17721 library subroutines as well; this varies from one stub to another,
17722 but in general the stubs are likely to use any of the common library
17723 subroutines which @code{@value{NGCC}} generates as inline code.
17726 @node Debug Session
17727 @subsection Putting it All Together
17729 @cindex remote serial debugging summary
17730 In summary, when your program is ready to debug, you must follow these
17735 Make sure you have defined the supporting low-level routines
17736 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17738 @code{getDebugChar}, @code{putDebugChar},
17739 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17743 Insert these lines in your program's startup code, before the main
17744 procedure is called:
17751 On some machines, when a breakpoint trap is raised, the hardware
17752 automatically makes the PC point to the instruction after the
17753 breakpoint. If your machine doesn't do that, you may need to adjust
17754 @code{handle_exception} to arrange for it to return to the instruction
17755 after the breakpoint on this first invocation, so that your program
17756 doesn't keep hitting the initial breakpoint instead of making
17760 For the 680x0 stub only, you need to provide a variable called
17761 @code{exceptionHook}. Normally you just use:
17764 void (*exceptionHook)() = 0;
17768 but if before calling @code{set_debug_traps}, you set it to point to a
17769 function in your program, that function is called when
17770 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17771 error). The function indicated by @code{exceptionHook} is called with
17772 one parameter: an @code{int} which is the exception number.
17775 Compile and link together: your program, the @value{GDBN} debugging stub for
17776 your target architecture, and the supporting subroutines.
17779 Make sure you have a serial connection between your target machine and
17780 the @value{GDBN} host, and identify the serial port on the host.
17783 @c The "remote" target now provides a `load' command, so we should
17784 @c document that. FIXME.
17785 Download your program to your target machine (or get it there by
17786 whatever means the manufacturer provides), and start it.
17789 Start @value{GDBN} on the host, and connect to the target
17790 (@pxref{Connecting,,Connecting to a Remote Target}).
17794 @node Configurations
17795 @chapter Configuration-Specific Information
17797 While nearly all @value{GDBN} commands are available for all native and
17798 cross versions of the debugger, there are some exceptions. This chapter
17799 describes things that are only available in certain configurations.
17801 There are three major categories of configurations: native
17802 configurations, where the host and target are the same, embedded
17803 operating system configurations, which are usually the same for several
17804 different processor architectures, and bare embedded processors, which
17805 are quite different from each other.
17810 * Embedded Processors::
17817 This section describes details specific to particular native
17822 * BSD libkvm Interface:: Debugging BSD kernel memory images
17823 * SVR4 Process Information:: SVR4 process information
17824 * DJGPP Native:: Features specific to the DJGPP port
17825 * Cygwin Native:: Features specific to the Cygwin port
17826 * Hurd Native:: Features specific to @sc{gnu} Hurd
17827 * Neutrino:: Features specific to QNX Neutrino
17828 * Darwin:: Features specific to Darwin
17834 On HP-UX systems, if you refer to a function or variable name that
17835 begins with a dollar sign, @value{GDBN} searches for a user or system
17836 name first, before it searches for a convenience variable.
17839 @node BSD libkvm Interface
17840 @subsection BSD libkvm Interface
17843 @cindex kernel memory image
17844 @cindex kernel crash dump
17846 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17847 interface that provides a uniform interface for accessing kernel virtual
17848 memory images, including live systems and crash dumps. @value{GDBN}
17849 uses this interface to allow you to debug live kernels and kernel crash
17850 dumps on many native BSD configurations. This is implemented as a
17851 special @code{kvm} debugging target. For debugging a live system, load
17852 the currently running kernel into @value{GDBN} and connect to the
17856 (@value{GDBP}) @b{target kvm}
17859 For debugging crash dumps, provide the file name of the crash dump as an
17863 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17866 Once connected to the @code{kvm} target, the following commands are
17872 Set current context from the @dfn{Process Control Block} (PCB) address.
17875 Set current context from proc address. This command isn't available on
17876 modern FreeBSD systems.
17879 @node SVR4 Process Information
17880 @subsection SVR4 Process Information
17882 @cindex examine process image
17883 @cindex process info via @file{/proc}
17885 Many versions of SVR4 and compatible systems provide a facility called
17886 @samp{/proc} that can be used to examine the image of a running
17887 process using file-system subroutines. If @value{GDBN} is configured
17888 for an operating system with this facility, the command @code{info
17889 proc} is available to report information about the process running
17890 your program, or about any process running on your system. @code{info
17891 proc} works only on SVR4 systems that include the @code{procfs} code.
17892 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17893 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17899 @itemx info proc @var{process-id}
17900 Summarize available information about any running process. If a
17901 process ID is specified by @var{process-id}, display information about
17902 that process; otherwise display information about the program being
17903 debugged. The summary includes the debugged process ID, the command
17904 line used to invoke it, its current working directory, and its
17905 executable file's absolute file name.
17907 On some systems, @var{process-id} can be of the form
17908 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17909 within a process. If the optional @var{pid} part is missing, it means
17910 a thread from the process being debugged (the leading @samp{/} still
17911 needs to be present, or else @value{GDBN} will interpret the number as
17912 a process ID rather than a thread ID).
17914 @item info proc mappings
17915 @cindex memory address space mappings
17916 Report the memory address space ranges accessible in the program, with
17917 information on whether the process has read, write, or execute access
17918 rights to each range. On @sc{gnu}/Linux systems, each memory range
17919 includes the object file which is mapped to that range, instead of the
17920 memory access rights to that range.
17922 @item info proc stat
17923 @itemx info proc status
17924 @cindex process detailed status information
17925 These subcommands are specific to @sc{gnu}/Linux systems. They show
17926 the process-related information, including the user ID and group ID;
17927 how many threads are there in the process; its virtual memory usage;
17928 the signals that are pending, blocked, and ignored; its TTY; its
17929 consumption of system and user time; its stack size; its @samp{nice}
17930 value; etc. For more information, see the @samp{proc} man page
17931 (type @kbd{man 5 proc} from your shell prompt).
17933 @item info proc all
17934 Show all the information about the process described under all of the
17935 above @code{info proc} subcommands.
17938 @comment These sub-options of 'info proc' were not included when
17939 @comment procfs.c was re-written. Keep their descriptions around
17940 @comment against the day when someone finds the time to put them back in.
17941 @kindex info proc times
17942 @item info proc times
17943 Starting time, user CPU time, and system CPU time for your program and
17946 @kindex info proc id
17948 Report on the process IDs related to your program: its own process ID,
17949 the ID of its parent, the process group ID, and the session ID.
17952 @item set procfs-trace
17953 @kindex set procfs-trace
17954 @cindex @code{procfs} API calls
17955 This command enables and disables tracing of @code{procfs} API calls.
17957 @item show procfs-trace
17958 @kindex show procfs-trace
17959 Show the current state of @code{procfs} API call tracing.
17961 @item set procfs-file @var{file}
17962 @kindex set procfs-file
17963 Tell @value{GDBN} to write @code{procfs} API trace to the named
17964 @var{file}. @value{GDBN} appends the trace info to the previous
17965 contents of the file. The default is to display the trace on the
17968 @item show procfs-file
17969 @kindex show procfs-file
17970 Show the file to which @code{procfs} API trace is written.
17972 @item proc-trace-entry
17973 @itemx proc-trace-exit
17974 @itemx proc-untrace-entry
17975 @itemx proc-untrace-exit
17976 @kindex proc-trace-entry
17977 @kindex proc-trace-exit
17978 @kindex proc-untrace-entry
17979 @kindex proc-untrace-exit
17980 These commands enable and disable tracing of entries into and exits
17981 from the @code{syscall} interface.
17984 @kindex info pidlist
17985 @cindex process list, QNX Neutrino
17986 For QNX Neutrino only, this command displays the list of all the
17987 processes and all the threads within each process.
17990 @kindex info meminfo
17991 @cindex mapinfo list, QNX Neutrino
17992 For QNX Neutrino only, this command displays the list of all mapinfos.
17996 @subsection Features for Debugging @sc{djgpp} Programs
17997 @cindex @sc{djgpp} debugging
17998 @cindex native @sc{djgpp} debugging
17999 @cindex MS-DOS-specific commands
18002 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18003 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18004 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18005 top of real-mode DOS systems and their emulations.
18007 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18008 defines a few commands specific to the @sc{djgpp} port. This
18009 subsection describes those commands.
18014 This is a prefix of @sc{djgpp}-specific commands which print
18015 information about the target system and important OS structures.
18018 @cindex MS-DOS system info
18019 @cindex free memory information (MS-DOS)
18020 @item info dos sysinfo
18021 This command displays assorted information about the underlying
18022 platform: the CPU type and features, the OS version and flavor, the
18023 DPMI version, and the available conventional and DPMI memory.
18028 @cindex segment descriptor tables
18029 @cindex descriptor tables display
18031 @itemx info dos ldt
18032 @itemx info dos idt
18033 These 3 commands display entries from, respectively, Global, Local,
18034 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18035 tables are data structures which store a descriptor for each segment
18036 that is currently in use. The segment's selector is an index into a
18037 descriptor table; the table entry for that index holds the
18038 descriptor's base address and limit, and its attributes and access
18041 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18042 segment (used for both data and the stack), and a DOS segment (which
18043 allows access to DOS/BIOS data structures and absolute addresses in
18044 conventional memory). However, the DPMI host will usually define
18045 additional segments in order to support the DPMI environment.
18047 @cindex garbled pointers
18048 These commands allow to display entries from the descriptor tables.
18049 Without an argument, all entries from the specified table are
18050 displayed. An argument, which should be an integer expression, means
18051 display a single entry whose index is given by the argument. For
18052 example, here's a convenient way to display information about the
18053 debugged program's data segment:
18056 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18057 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18061 This comes in handy when you want to see whether a pointer is outside
18062 the data segment's limit (i.e.@: @dfn{garbled}).
18064 @cindex page tables display (MS-DOS)
18066 @itemx info dos pte
18067 These two commands display entries from, respectively, the Page
18068 Directory and the Page Tables. Page Directories and Page Tables are
18069 data structures which control how virtual memory addresses are mapped
18070 into physical addresses. A Page Table includes an entry for every
18071 page of memory that is mapped into the program's address space; there
18072 may be several Page Tables, each one holding up to 4096 entries. A
18073 Page Directory has up to 4096 entries, one each for every Page Table
18074 that is currently in use.
18076 Without an argument, @kbd{info dos pde} displays the entire Page
18077 Directory, and @kbd{info dos pte} displays all the entries in all of
18078 the Page Tables. An argument, an integer expression, given to the
18079 @kbd{info dos pde} command means display only that entry from the Page
18080 Directory table. An argument given to the @kbd{info dos pte} command
18081 means display entries from a single Page Table, the one pointed to by
18082 the specified entry in the Page Directory.
18084 @cindex direct memory access (DMA) on MS-DOS
18085 These commands are useful when your program uses @dfn{DMA} (Direct
18086 Memory Access), which needs physical addresses to program the DMA
18089 These commands are supported only with some DPMI servers.
18091 @cindex physical address from linear address
18092 @item info dos address-pte @var{addr}
18093 This command displays the Page Table entry for a specified linear
18094 address. The argument @var{addr} is a linear address which should
18095 already have the appropriate segment's base address added to it,
18096 because this command accepts addresses which may belong to @emph{any}
18097 segment. For example, here's how to display the Page Table entry for
18098 the page where a variable @code{i} is stored:
18101 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18102 @exdent @code{Page Table entry for address 0x11a00d30:}
18103 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18107 This says that @code{i} is stored at offset @code{0xd30} from the page
18108 whose physical base address is @code{0x02698000}, and shows all the
18109 attributes of that page.
18111 Note that you must cast the addresses of variables to a @code{char *},
18112 since otherwise the value of @code{__djgpp_base_address}, the base
18113 address of all variables and functions in a @sc{djgpp} program, will
18114 be added using the rules of C pointer arithmetics: if @code{i} is
18115 declared an @code{int}, @value{GDBN} will add 4 times the value of
18116 @code{__djgpp_base_address} to the address of @code{i}.
18118 Here's another example, it displays the Page Table entry for the
18122 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18123 @exdent @code{Page Table entry for address 0x29110:}
18124 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18128 (The @code{+ 3} offset is because the transfer buffer's address is the
18129 3rd member of the @code{_go32_info_block} structure.) The output
18130 clearly shows that this DPMI server maps the addresses in conventional
18131 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18132 linear (@code{0x29110}) addresses are identical.
18134 This command is supported only with some DPMI servers.
18137 @cindex DOS serial data link, remote debugging
18138 In addition to native debugging, the DJGPP port supports remote
18139 debugging via a serial data link. The following commands are specific
18140 to remote serial debugging in the DJGPP port of @value{GDBN}.
18143 @kindex set com1base
18144 @kindex set com1irq
18145 @kindex set com2base
18146 @kindex set com2irq
18147 @kindex set com3base
18148 @kindex set com3irq
18149 @kindex set com4base
18150 @kindex set com4irq
18151 @item set com1base @var{addr}
18152 This command sets the base I/O port address of the @file{COM1} serial
18155 @item set com1irq @var{irq}
18156 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18157 for the @file{COM1} serial port.
18159 There are similar commands @samp{set com2base}, @samp{set com3irq},
18160 etc.@: for setting the port address and the @code{IRQ} lines for the
18163 @kindex show com1base
18164 @kindex show com1irq
18165 @kindex show com2base
18166 @kindex show com2irq
18167 @kindex show com3base
18168 @kindex show com3irq
18169 @kindex show com4base
18170 @kindex show com4irq
18171 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18172 display the current settings of the base address and the @code{IRQ}
18173 lines used by the COM ports.
18176 @kindex info serial
18177 @cindex DOS serial port status
18178 This command prints the status of the 4 DOS serial ports. For each
18179 port, it prints whether it's active or not, its I/O base address and
18180 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18181 counts of various errors encountered so far.
18185 @node Cygwin Native
18186 @subsection Features for Debugging MS Windows PE Executables
18187 @cindex MS Windows debugging
18188 @cindex native Cygwin debugging
18189 @cindex Cygwin-specific commands
18191 @value{GDBN} supports native debugging of MS Windows programs, including
18192 DLLs with and without symbolic debugging information.
18194 @cindex Ctrl-BREAK, MS-Windows
18195 @cindex interrupt debuggee on MS-Windows
18196 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18197 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18198 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18199 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18200 sequence, which can be used to interrupt the debuggee even if it
18203 There are various additional Cygwin-specific commands, described in
18204 this section. Working with DLLs that have no debugging symbols is
18205 described in @ref{Non-debug DLL Symbols}.
18210 This is a prefix of MS Windows-specific commands which print
18211 information about the target system and important OS structures.
18213 @item info w32 selector
18214 This command displays information returned by
18215 the Win32 API @code{GetThreadSelectorEntry} function.
18216 It takes an optional argument that is evaluated to
18217 a long value to give the information about this given selector.
18218 Without argument, this command displays information
18219 about the six segment registers.
18221 @item info w32 thread-information-block
18222 This command displays thread specific information stored in the
18223 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18224 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18228 This is a Cygwin-specific alias of @code{info shared}.
18230 @kindex dll-symbols
18232 This command loads symbols from a dll similarly to
18233 add-sym command but without the need to specify a base address.
18235 @kindex set cygwin-exceptions
18236 @cindex debugging the Cygwin DLL
18237 @cindex Cygwin DLL, debugging
18238 @item set cygwin-exceptions @var{mode}
18239 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18240 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18241 @value{GDBN} will delay recognition of exceptions, and may ignore some
18242 exceptions which seem to be caused by internal Cygwin DLL
18243 ``bookkeeping''. This option is meant primarily for debugging the
18244 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18245 @value{GDBN} users with false @code{SIGSEGV} signals.
18247 @kindex show cygwin-exceptions
18248 @item show cygwin-exceptions
18249 Displays whether @value{GDBN} will break on exceptions that happen
18250 inside the Cygwin DLL itself.
18252 @kindex set new-console
18253 @item set new-console @var{mode}
18254 If @var{mode} is @code{on} the debuggee will
18255 be started in a new console on next start.
18256 If @var{mode} is @code{off}, the debuggee will
18257 be started in the same console as the debugger.
18259 @kindex show new-console
18260 @item show new-console
18261 Displays whether a new console is used
18262 when the debuggee is started.
18264 @kindex set new-group
18265 @item set new-group @var{mode}
18266 This boolean value controls whether the debuggee should
18267 start a new group or stay in the same group as the debugger.
18268 This affects the way the Windows OS handles
18271 @kindex show new-group
18272 @item show new-group
18273 Displays current value of new-group boolean.
18275 @kindex set debugevents
18276 @item set debugevents
18277 This boolean value adds debug output concerning kernel events related
18278 to the debuggee seen by the debugger. This includes events that
18279 signal thread and process creation and exit, DLL loading and
18280 unloading, console interrupts, and debugging messages produced by the
18281 Windows @code{OutputDebugString} API call.
18283 @kindex set debugexec
18284 @item set debugexec
18285 This boolean value adds debug output concerning execute events
18286 (such as resume thread) seen by the debugger.
18288 @kindex set debugexceptions
18289 @item set debugexceptions
18290 This boolean value adds debug output concerning exceptions in the
18291 debuggee seen by the debugger.
18293 @kindex set debugmemory
18294 @item set debugmemory
18295 This boolean value adds debug output concerning debuggee memory reads
18296 and writes by the debugger.
18300 This boolean values specifies whether the debuggee is called
18301 via a shell or directly (default value is on).
18305 Displays if the debuggee will be started with a shell.
18310 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18313 @node Non-debug DLL Symbols
18314 @subsubsection Support for DLLs without Debugging Symbols
18315 @cindex DLLs with no debugging symbols
18316 @cindex Minimal symbols and DLLs
18318 Very often on windows, some of the DLLs that your program relies on do
18319 not include symbolic debugging information (for example,
18320 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18321 symbols in a DLL, it relies on the minimal amount of symbolic
18322 information contained in the DLL's export table. This section
18323 describes working with such symbols, known internally to @value{GDBN} as
18324 ``minimal symbols''.
18326 Note that before the debugged program has started execution, no DLLs
18327 will have been loaded. The easiest way around this problem is simply to
18328 start the program --- either by setting a breakpoint or letting the
18329 program run once to completion. It is also possible to force
18330 @value{GDBN} to load a particular DLL before starting the executable ---
18331 see the shared library information in @ref{Files}, or the
18332 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18333 explicitly loading symbols from a DLL with no debugging information will
18334 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18335 which may adversely affect symbol lookup performance.
18337 @subsubsection DLL Name Prefixes
18339 In keeping with the naming conventions used by the Microsoft debugging
18340 tools, DLL export symbols are made available with a prefix based on the
18341 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18342 also entered into the symbol table, so @code{CreateFileA} is often
18343 sufficient. In some cases there will be name clashes within a program
18344 (particularly if the executable itself includes full debugging symbols)
18345 necessitating the use of the fully qualified name when referring to the
18346 contents of the DLL. Use single-quotes around the name to avoid the
18347 exclamation mark (``!'') being interpreted as a language operator.
18349 Note that the internal name of the DLL may be all upper-case, even
18350 though the file name of the DLL is lower-case, or vice-versa. Since
18351 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18352 some confusion. If in doubt, try the @code{info functions} and
18353 @code{info variables} commands or even @code{maint print msymbols}
18354 (@pxref{Symbols}). Here's an example:
18357 (@value{GDBP}) info function CreateFileA
18358 All functions matching regular expression "CreateFileA":
18360 Non-debugging symbols:
18361 0x77e885f4 CreateFileA
18362 0x77e885f4 KERNEL32!CreateFileA
18366 (@value{GDBP}) info function !
18367 All functions matching regular expression "!":
18369 Non-debugging symbols:
18370 0x6100114c cygwin1!__assert
18371 0x61004034 cygwin1!_dll_crt0@@0
18372 0x61004240 cygwin1!dll_crt0(per_process *)
18376 @subsubsection Working with Minimal Symbols
18378 Symbols extracted from a DLL's export table do not contain very much
18379 type information. All that @value{GDBN} can do is guess whether a symbol
18380 refers to a function or variable depending on the linker section that
18381 contains the symbol. Also note that the actual contents of the memory
18382 contained in a DLL are not available unless the program is running. This
18383 means that you cannot examine the contents of a variable or disassemble
18384 a function within a DLL without a running program.
18386 Variables are generally treated as pointers and dereferenced
18387 automatically. For this reason, it is often necessary to prefix a
18388 variable name with the address-of operator (``&'') and provide explicit
18389 type information in the command. Here's an example of the type of
18393 (@value{GDBP}) print 'cygwin1!__argv'
18398 (@value{GDBP}) x 'cygwin1!__argv'
18399 0x10021610: "\230y\""
18402 And two possible solutions:
18405 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18406 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18410 (@value{GDBP}) x/2x &'cygwin1!__argv'
18411 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18412 (@value{GDBP}) x/x 0x10021608
18413 0x10021608: 0x0022fd98
18414 (@value{GDBP}) x/s 0x0022fd98
18415 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18418 Setting a break point within a DLL is possible even before the program
18419 starts execution. However, under these circumstances, @value{GDBN} can't
18420 examine the initial instructions of the function in order to skip the
18421 function's frame set-up code. You can work around this by using ``*&''
18422 to set the breakpoint at a raw memory address:
18425 (@value{GDBP}) break *&'python22!PyOS_Readline'
18426 Breakpoint 1 at 0x1e04eff0
18429 The author of these extensions is not entirely convinced that setting a
18430 break point within a shared DLL like @file{kernel32.dll} is completely
18434 @subsection Commands Specific to @sc{gnu} Hurd Systems
18435 @cindex @sc{gnu} Hurd debugging
18437 This subsection describes @value{GDBN} commands specific to the
18438 @sc{gnu} Hurd native debugging.
18443 @kindex set signals@r{, Hurd command}
18444 @kindex set sigs@r{, Hurd command}
18445 This command toggles the state of inferior signal interception by
18446 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18447 affected by this command. @code{sigs} is a shorthand alias for
18452 @kindex show signals@r{, Hurd command}
18453 @kindex show sigs@r{, Hurd command}
18454 Show the current state of intercepting inferior's signals.
18456 @item set signal-thread
18457 @itemx set sigthread
18458 @kindex set signal-thread
18459 @kindex set sigthread
18460 This command tells @value{GDBN} which thread is the @code{libc} signal
18461 thread. That thread is run when a signal is delivered to a running
18462 process. @code{set sigthread} is the shorthand alias of @code{set
18465 @item show signal-thread
18466 @itemx show sigthread
18467 @kindex show signal-thread
18468 @kindex show sigthread
18469 These two commands show which thread will run when the inferior is
18470 delivered a signal.
18473 @kindex set stopped@r{, Hurd command}
18474 This commands tells @value{GDBN} that the inferior process is stopped,
18475 as with the @code{SIGSTOP} signal. The stopped process can be
18476 continued by delivering a signal to it.
18479 @kindex show stopped@r{, Hurd command}
18480 This command shows whether @value{GDBN} thinks the debuggee is
18483 @item set exceptions
18484 @kindex set exceptions@r{, Hurd command}
18485 Use this command to turn off trapping of exceptions in the inferior.
18486 When exception trapping is off, neither breakpoints nor
18487 single-stepping will work. To restore the default, set exception
18490 @item show exceptions
18491 @kindex show exceptions@r{, Hurd command}
18492 Show the current state of trapping exceptions in the inferior.
18494 @item set task pause
18495 @kindex set task@r{, Hurd commands}
18496 @cindex task attributes (@sc{gnu} Hurd)
18497 @cindex pause current task (@sc{gnu} Hurd)
18498 This command toggles task suspension when @value{GDBN} has control.
18499 Setting it to on takes effect immediately, and the task is suspended
18500 whenever @value{GDBN} gets control. Setting it to off will take
18501 effect the next time the inferior is continued. If this option is set
18502 to off, you can use @code{set thread default pause on} or @code{set
18503 thread pause on} (see below) to pause individual threads.
18505 @item show task pause
18506 @kindex show task@r{, Hurd commands}
18507 Show the current state of task suspension.
18509 @item set task detach-suspend-count
18510 @cindex task suspend count
18511 @cindex detach from task, @sc{gnu} Hurd
18512 This command sets the suspend count the task will be left with when
18513 @value{GDBN} detaches from it.
18515 @item show task detach-suspend-count
18516 Show the suspend count the task will be left with when detaching.
18518 @item set task exception-port
18519 @itemx set task excp
18520 @cindex task exception port, @sc{gnu} Hurd
18521 This command sets the task exception port to which @value{GDBN} will
18522 forward exceptions. The argument should be the value of the @dfn{send
18523 rights} of the task. @code{set task excp} is a shorthand alias.
18525 @item set noninvasive
18526 @cindex noninvasive task options
18527 This command switches @value{GDBN} to a mode that is the least
18528 invasive as far as interfering with the inferior is concerned. This
18529 is the same as using @code{set task pause}, @code{set exceptions}, and
18530 @code{set signals} to values opposite to the defaults.
18532 @item info send-rights
18533 @itemx info receive-rights
18534 @itemx info port-rights
18535 @itemx info port-sets
18536 @itemx info dead-names
18539 @cindex send rights, @sc{gnu} Hurd
18540 @cindex receive rights, @sc{gnu} Hurd
18541 @cindex port rights, @sc{gnu} Hurd
18542 @cindex port sets, @sc{gnu} Hurd
18543 @cindex dead names, @sc{gnu} Hurd
18544 These commands display information about, respectively, send rights,
18545 receive rights, port rights, port sets, and dead names of a task.
18546 There are also shorthand aliases: @code{info ports} for @code{info
18547 port-rights} and @code{info psets} for @code{info port-sets}.
18549 @item set thread pause
18550 @kindex set thread@r{, Hurd command}
18551 @cindex thread properties, @sc{gnu} Hurd
18552 @cindex pause current thread (@sc{gnu} Hurd)
18553 This command toggles current thread suspension when @value{GDBN} has
18554 control. Setting it to on takes effect immediately, and the current
18555 thread is suspended whenever @value{GDBN} gets control. Setting it to
18556 off will take effect the next time the inferior is continued.
18557 Normally, this command has no effect, since when @value{GDBN} has
18558 control, the whole task is suspended. However, if you used @code{set
18559 task pause off} (see above), this command comes in handy to suspend
18560 only the current thread.
18562 @item show thread pause
18563 @kindex show thread@r{, Hurd command}
18564 This command shows the state of current thread suspension.
18566 @item set thread run
18567 This command sets whether the current thread is allowed to run.
18569 @item show thread run
18570 Show whether the current thread is allowed to run.
18572 @item set thread detach-suspend-count
18573 @cindex thread suspend count, @sc{gnu} Hurd
18574 @cindex detach from thread, @sc{gnu} Hurd
18575 This command sets the suspend count @value{GDBN} will leave on a
18576 thread when detaching. This number is relative to the suspend count
18577 found by @value{GDBN} when it notices the thread; use @code{set thread
18578 takeover-suspend-count} to force it to an absolute value.
18580 @item show thread detach-suspend-count
18581 Show the suspend count @value{GDBN} will leave on the thread when
18584 @item set thread exception-port
18585 @itemx set thread excp
18586 Set the thread exception port to which to forward exceptions. This
18587 overrides the port set by @code{set task exception-port} (see above).
18588 @code{set thread excp} is the shorthand alias.
18590 @item set thread takeover-suspend-count
18591 Normally, @value{GDBN}'s thread suspend counts are relative to the
18592 value @value{GDBN} finds when it notices each thread. This command
18593 changes the suspend counts to be absolute instead.
18595 @item set thread default
18596 @itemx show thread default
18597 @cindex thread default settings, @sc{gnu} Hurd
18598 Each of the above @code{set thread} commands has a @code{set thread
18599 default} counterpart (e.g., @code{set thread default pause}, @code{set
18600 thread default exception-port}, etc.). The @code{thread default}
18601 variety of commands sets the default thread properties for all
18602 threads; you can then change the properties of individual threads with
18603 the non-default commands.
18608 @subsection QNX Neutrino
18609 @cindex QNX Neutrino
18611 @value{GDBN} provides the following commands specific to the QNX
18615 @item set debug nto-debug
18616 @kindex set debug nto-debug
18617 When set to on, enables debugging messages specific to the QNX
18620 @item show debug nto-debug
18621 @kindex show debug nto-debug
18622 Show the current state of QNX Neutrino messages.
18629 @value{GDBN} provides the following commands specific to the Darwin target:
18632 @item set debug darwin @var{num}
18633 @kindex set debug darwin
18634 When set to a non zero value, enables debugging messages specific to
18635 the Darwin support. Higher values produce more verbose output.
18637 @item show debug darwin
18638 @kindex show debug darwin
18639 Show the current state of Darwin messages.
18641 @item set debug mach-o @var{num}
18642 @kindex set debug mach-o
18643 When set to a non zero value, enables debugging messages while
18644 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18645 file format used on Darwin for object and executable files.) Higher
18646 values produce more verbose output. This is a command to diagnose
18647 problems internal to @value{GDBN} and should not be needed in normal
18650 @item show debug mach-o
18651 @kindex show debug mach-o
18652 Show the current state of Mach-O file messages.
18654 @item set mach-exceptions on
18655 @itemx set mach-exceptions off
18656 @kindex set mach-exceptions
18657 On Darwin, faults are first reported as a Mach exception and are then
18658 mapped to a Posix signal. Use this command to turn on trapping of
18659 Mach exceptions in the inferior. This might be sometimes useful to
18660 better understand the cause of a fault. The default is off.
18662 @item show mach-exceptions
18663 @kindex show mach-exceptions
18664 Show the current state of exceptions trapping.
18669 @section Embedded Operating Systems
18671 This section describes configurations involving the debugging of
18672 embedded operating systems that are available for several different
18676 * VxWorks:: Using @value{GDBN} with VxWorks
18679 @value{GDBN} includes the ability to debug programs running on
18680 various real-time operating systems.
18683 @subsection Using @value{GDBN} with VxWorks
18689 @kindex target vxworks
18690 @item target vxworks @var{machinename}
18691 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18692 is the target system's machine name or IP address.
18696 On VxWorks, @code{load} links @var{filename} dynamically on the
18697 current target system as well as adding its symbols in @value{GDBN}.
18699 @value{GDBN} enables developers to spawn and debug tasks running on networked
18700 VxWorks targets from a Unix host. Already-running tasks spawned from
18701 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18702 both the Unix host and on the VxWorks target. The program
18703 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18704 installed with the name @code{vxgdb}, to distinguish it from a
18705 @value{GDBN} for debugging programs on the host itself.)
18708 @item VxWorks-timeout @var{args}
18709 @kindex vxworks-timeout
18710 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18711 This option is set by the user, and @var{args} represents the number of
18712 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18713 your VxWorks target is a slow software simulator or is on the far side
18714 of a thin network line.
18717 The following information on connecting to VxWorks was current when
18718 this manual was produced; newer releases of VxWorks may use revised
18721 @findex INCLUDE_RDB
18722 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18723 to include the remote debugging interface routines in the VxWorks
18724 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18725 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18726 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18727 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18728 information on configuring and remaking VxWorks, see the manufacturer's
18730 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18732 Once you have included @file{rdb.a} in your VxWorks system image and set
18733 your Unix execution search path to find @value{GDBN}, you are ready to
18734 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18735 @code{vxgdb}, depending on your installation).
18737 @value{GDBN} comes up showing the prompt:
18744 * VxWorks Connection:: Connecting to VxWorks
18745 * VxWorks Download:: VxWorks download
18746 * VxWorks Attach:: Running tasks
18749 @node VxWorks Connection
18750 @subsubsection Connecting to VxWorks
18752 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18753 network. To connect to a target whose host name is ``@code{tt}'', type:
18756 (vxgdb) target vxworks tt
18760 @value{GDBN} displays messages like these:
18763 Attaching remote machine across net...
18768 @value{GDBN} then attempts to read the symbol tables of any object modules
18769 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18770 these files by searching the directories listed in the command search
18771 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18772 to find an object file, it displays a message such as:
18775 prog.o: No such file or directory.
18778 When this happens, add the appropriate directory to the search path with
18779 the @value{GDBN} command @code{path}, and execute the @code{target}
18782 @node VxWorks Download
18783 @subsubsection VxWorks Download
18785 @cindex download to VxWorks
18786 If you have connected to the VxWorks target and you want to debug an
18787 object that has not yet been loaded, you can use the @value{GDBN}
18788 @code{load} command to download a file from Unix to VxWorks
18789 incrementally. The object file given as an argument to the @code{load}
18790 command is actually opened twice: first by the VxWorks target in order
18791 to download the code, then by @value{GDBN} in order to read the symbol
18792 table. This can lead to problems if the current working directories on
18793 the two systems differ. If both systems have NFS mounted the same
18794 filesystems, you can avoid these problems by using absolute paths.
18795 Otherwise, it is simplest to set the working directory on both systems
18796 to the directory in which the object file resides, and then to reference
18797 the file by its name, without any path. For instance, a program
18798 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18799 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18800 program, type this on VxWorks:
18803 -> cd "@var{vxpath}/vw/demo/rdb"
18807 Then, in @value{GDBN}, type:
18810 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18811 (vxgdb) load prog.o
18814 @value{GDBN} displays a response similar to this:
18817 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18820 You can also use the @code{load} command to reload an object module
18821 after editing and recompiling the corresponding source file. Note that
18822 this makes @value{GDBN} delete all currently-defined breakpoints,
18823 auto-displays, and convenience variables, and to clear the value
18824 history. (This is necessary in order to preserve the integrity of
18825 debugger's data structures that reference the target system's symbol
18828 @node VxWorks Attach
18829 @subsubsection Running Tasks
18831 @cindex running VxWorks tasks
18832 You can also attach to an existing task using the @code{attach} command as
18836 (vxgdb) attach @var{task}
18840 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18841 or suspended when you attach to it. Running tasks are suspended at
18842 the time of attachment.
18844 @node Embedded Processors
18845 @section Embedded Processors
18847 This section goes into details specific to particular embedded
18850 @cindex send command to simulator
18851 Whenever a specific embedded processor has a simulator, @value{GDBN}
18852 allows to send an arbitrary command to the simulator.
18855 @item sim @var{command}
18856 @kindex sim@r{, a command}
18857 Send an arbitrary @var{command} string to the simulator. Consult the
18858 documentation for the specific simulator in use for information about
18859 acceptable commands.
18865 * M32R/D:: Renesas M32R/D
18866 * M68K:: Motorola M68K
18867 * MicroBlaze:: Xilinx MicroBlaze
18868 * MIPS Embedded:: MIPS Embedded
18869 * OpenRISC 1000:: OpenRisc 1000
18870 * PA:: HP PA Embedded
18871 * PowerPC Embedded:: PowerPC Embedded
18872 * Sparclet:: Tsqware Sparclet
18873 * Sparclite:: Fujitsu Sparclite
18874 * Z8000:: Zilog Z8000
18877 * Super-H:: Renesas Super-H
18886 @item target rdi @var{dev}
18887 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18888 use this target to communicate with both boards running the Angel
18889 monitor, or with the EmbeddedICE JTAG debug device.
18892 @item target rdp @var{dev}
18897 @value{GDBN} provides the following ARM-specific commands:
18900 @item set arm disassembler
18902 This commands selects from a list of disassembly styles. The
18903 @code{"std"} style is the standard style.
18905 @item show arm disassembler
18907 Show the current disassembly style.
18909 @item set arm apcs32
18910 @cindex ARM 32-bit mode
18911 This command toggles ARM operation mode between 32-bit and 26-bit.
18913 @item show arm apcs32
18914 Display the current usage of the ARM 32-bit mode.
18916 @item set arm fpu @var{fputype}
18917 This command sets the ARM floating-point unit (FPU) type. The
18918 argument @var{fputype} can be one of these:
18922 Determine the FPU type by querying the OS ABI.
18924 Software FPU, with mixed-endian doubles on little-endian ARM
18927 GCC-compiled FPA co-processor.
18929 Software FPU with pure-endian doubles.
18935 Show the current type of the FPU.
18938 This command forces @value{GDBN} to use the specified ABI.
18941 Show the currently used ABI.
18943 @item set arm fallback-mode (arm|thumb|auto)
18944 @value{GDBN} uses the symbol table, when available, to determine
18945 whether instructions are ARM or Thumb. This command controls
18946 @value{GDBN}'s default behavior when the symbol table is not
18947 available. The default is @samp{auto}, which causes @value{GDBN} to
18948 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18951 @item show arm fallback-mode
18952 Show the current fallback instruction mode.
18954 @item set arm force-mode (arm|thumb|auto)
18955 This command overrides use of the symbol table to determine whether
18956 instructions are ARM or Thumb. The default is @samp{auto}, which
18957 causes @value{GDBN} to use the symbol table and then the setting
18958 of @samp{set arm fallback-mode}.
18960 @item show arm force-mode
18961 Show the current forced instruction mode.
18963 @item set debug arm
18964 Toggle whether to display ARM-specific debugging messages from the ARM
18965 target support subsystem.
18967 @item show debug arm
18968 Show whether ARM-specific debugging messages are enabled.
18971 The following commands are available when an ARM target is debugged
18972 using the RDI interface:
18975 @item rdilogfile @r{[}@var{file}@r{]}
18977 @cindex ADP (Angel Debugger Protocol) logging
18978 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18979 With an argument, sets the log file to the specified @var{file}. With
18980 no argument, show the current log file name. The default log file is
18983 @item rdilogenable @r{[}@var{arg}@r{]}
18984 @kindex rdilogenable
18985 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18986 enables logging, with an argument 0 or @code{"no"} disables it. With
18987 no arguments displays the current setting. When logging is enabled,
18988 ADP packets exchanged between @value{GDBN} and the RDI target device
18989 are logged to a file.
18991 @item set rdiromatzero
18992 @kindex set rdiromatzero
18993 @cindex ROM at zero address, RDI
18994 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18995 vector catching is disabled, so that zero address can be used. If off
18996 (the default), vector catching is enabled. For this command to take
18997 effect, it needs to be invoked prior to the @code{target rdi} command.
18999 @item show rdiromatzero
19000 @kindex show rdiromatzero
19001 Show the current setting of ROM at zero address.
19003 @item set rdiheartbeat
19004 @kindex set rdiheartbeat
19005 @cindex RDI heartbeat
19006 Enable or disable RDI heartbeat packets. It is not recommended to
19007 turn on this option, since it confuses ARM and EPI JTAG interface, as
19008 well as the Angel monitor.
19010 @item show rdiheartbeat
19011 @kindex show rdiheartbeat
19012 Show the setting of RDI heartbeat packets.
19016 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19017 The @value{GDBN} ARM simulator accepts the following optional arguments.
19020 @item --swi-support=@var{type}
19021 Tell the simulator which SWI interfaces to support.
19022 @var{type} may be a comma separated list of the following values.
19023 The default value is @code{all}.
19036 @subsection Renesas M32R/D and M32R/SDI
19039 @kindex target m32r
19040 @item target m32r @var{dev}
19041 Renesas M32R/D ROM monitor.
19043 @kindex target m32rsdi
19044 @item target m32rsdi @var{dev}
19045 Renesas M32R SDI server, connected via parallel port to the board.
19048 The following @value{GDBN} commands are specific to the M32R monitor:
19051 @item set download-path @var{path}
19052 @kindex set download-path
19053 @cindex find downloadable @sc{srec} files (M32R)
19054 Set the default path for finding downloadable @sc{srec} files.
19056 @item show download-path
19057 @kindex show download-path
19058 Show the default path for downloadable @sc{srec} files.
19060 @item set board-address @var{addr}
19061 @kindex set board-address
19062 @cindex M32-EVA target board address
19063 Set the IP address for the M32R-EVA target board.
19065 @item show board-address
19066 @kindex show board-address
19067 Show the current IP address of the target board.
19069 @item set server-address @var{addr}
19070 @kindex set server-address
19071 @cindex download server address (M32R)
19072 Set the IP address for the download server, which is the @value{GDBN}'s
19075 @item show server-address
19076 @kindex show server-address
19077 Display the IP address of the download server.
19079 @item upload @r{[}@var{file}@r{]}
19080 @kindex upload@r{, M32R}
19081 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19082 upload capability. If no @var{file} argument is given, the current
19083 executable file is uploaded.
19085 @item tload @r{[}@var{file}@r{]}
19086 @kindex tload@r{, M32R}
19087 Test the @code{upload} command.
19090 The following commands are available for M32R/SDI:
19095 @cindex reset SDI connection, M32R
19096 This command resets the SDI connection.
19100 This command shows the SDI connection status.
19103 @kindex debug_chaos
19104 @cindex M32R/Chaos debugging
19105 Instructs the remote that M32R/Chaos debugging is to be used.
19107 @item use_debug_dma
19108 @kindex use_debug_dma
19109 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19112 @kindex use_mon_code
19113 Instructs the remote to use the MON_CODE method of accessing memory.
19116 @kindex use_ib_break
19117 Instructs the remote to set breakpoints by IB break.
19119 @item use_dbt_break
19120 @kindex use_dbt_break
19121 Instructs the remote to set breakpoints by DBT.
19127 The Motorola m68k configuration includes ColdFire support, and a
19128 target command for the following ROM monitor.
19132 @kindex target dbug
19133 @item target dbug @var{dev}
19134 dBUG ROM monitor for Motorola ColdFire.
19139 @subsection MicroBlaze
19140 @cindex Xilinx MicroBlaze
19141 @cindex XMD, Xilinx Microprocessor Debugger
19143 The MicroBlaze is a soft-core processor supported on various Xilinx
19144 FPGAs, such as Spartan or Virtex series. Boards with these processors
19145 usually have JTAG ports which connect to a host system running the Xilinx
19146 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19147 This host system is used to download the configuration bitstream to
19148 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19149 communicates with the target board using the JTAG interface and
19150 presents a @code{gdbserver} interface to the board. By default
19151 @code{xmd} uses port @code{1234}. (While it is possible to change
19152 this default port, it requires the use of undocumented @code{xmd}
19153 commands. Contact Xilinx support if you need to do this.)
19155 Use these GDB commands to connect to the MicroBlaze target processor.
19158 @item target remote :1234
19159 Use this command to connect to the target if you are running @value{GDBN}
19160 on the same system as @code{xmd}.
19162 @item target remote @var{xmd-host}:1234
19163 Use this command to connect to the target if it is connected to @code{xmd}
19164 running on a different system named @var{xmd-host}.
19167 Use this command to download a program to the MicroBlaze target.
19169 @item set debug microblaze @var{n}
19170 Enable MicroBlaze-specific debugging messages if non-zero.
19172 @item show debug microblaze @var{n}
19173 Show MicroBlaze-specific debugging level.
19176 @node MIPS Embedded
19177 @subsection MIPS Embedded
19179 @cindex MIPS boards
19180 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19181 MIPS board attached to a serial line. This is available when
19182 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19185 Use these @value{GDBN} commands to specify the connection to your target board:
19188 @item target mips @var{port}
19189 @kindex target mips @var{port}
19190 To run a program on the board, start up @code{@value{GDBP}} with the
19191 name of your program as the argument. To connect to the board, use the
19192 command @samp{target mips @var{port}}, where @var{port} is the name of
19193 the serial port connected to the board. If the program has not already
19194 been downloaded to the board, you may use the @code{load} command to
19195 download it. You can then use all the usual @value{GDBN} commands.
19197 For example, this sequence connects to the target board through a serial
19198 port, and loads and runs a program called @var{prog} through the
19202 host$ @value{GDBP} @var{prog}
19203 @value{GDBN} is free software and @dots{}
19204 (@value{GDBP}) target mips /dev/ttyb
19205 (@value{GDBP}) load @var{prog}
19209 @item target mips @var{hostname}:@var{portnumber}
19210 On some @value{GDBN} host configurations, you can specify a TCP
19211 connection (for instance, to a serial line managed by a terminal
19212 concentrator) instead of a serial port, using the syntax
19213 @samp{@var{hostname}:@var{portnumber}}.
19215 @item target pmon @var{port}
19216 @kindex target pmon @var{port}
19219 @item target ddb @var{port}
19220 @kindex target ddb @var{port}
19221 NEC's DDB variant of PMON for Vr4300.
19223 @item target lsi @var{port}
19224 @kindex target lsi @var{port}
19225 LSI variant of PMON.
19227 @kindex target r3900
19228 @item target r3900 @var{dev}
19229 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19231 @kindex target array
19232 @item target array @var{dev}
19233 Array Tech LSI33K RAID controller board.
19239 @value{GDBN} also supports these special commands for MIPS targets:
19242 @item set mipsfpu double
19243 @itemx set mipsfpu single
19244 @itemx set mipsfpu none
19245 @itemx set mipsfpu auto
19246 @itemx show mipsfpu
19247 @kindex set mipsfpu
19248 @kindex show mipsfpu
19249 @cindex MIPS remote floating point
19250 @cindex floating point, MIPS remote
19251 If your target board does not support the MIPS floating point
19252 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19253 need this, you may wish to put the command in your @value{GDBN} init
19254 file). This tells @value{GDBN} how to find the return value of
19255 functions which return floating point values. It also allows
19256 @value{GDBN} to avoid saving the floating point registers when calling
19257 functions on the board. If you are using a floating point coprocessor
19258 with only single precision floating point support, as on the @sc{r4650}
19259 processor, use the command @samp{set mipsfpu single}. The default
19260 double precision floating point coprocessor may be selected using
19261 @samp{set mipsfpu double}.
19263 In previous versions the only choices were double precision or no
19264 floating point, so @samp{set mipsfpu on} will select double precision
19265 and @samp{set mipsfpu off} will select no floating point.
19267 As usual, you can inquire about the @code{mipsfpu} variable with
19268 @samp{show mipsfpu}.
19270 @item set timeout @var{seconds}
19271 @itemx set retransmit-timeout @var{seconds}
19272 @itemx show timeout
19273 @itemx show retransmit-timeout
19274 @cindex @code{timeout}, MIPS protocol
19275 @cindex @code{retransmit-timeout}, MIPS protocol
19276 @kindex set timeout
19277 @kindex show timeout
19278 @kindex set retransmit-timeout
19279 @kindex show retransmit-timeout
19280 You can control the timeout used while waiting for a packet, in the MIPS
19281 remote protocol, with the @code{set timeout @var{seconds}} command. The
19282 default is 5 seconds. Similarly, you can control the timeout used while
19283 waiting for an acknowledgment of a packet with the @code{set
19284 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19285 You can inspect both values with @code{show timeout} and @code{show
19286 retransmit-timeout}. (These commands are @emph{only} available when
19287 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19289 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19290 is waiting for your program to stop. In that case, @value{GDBN} waits
19291 forever because it has no way of knowing how long the program is going
19292 to run before stopping.
19294 @item set syn-garbage-limit @var{num}
19295 @kindex set syn-garbage-limit@r{, MIPS remote}
19296 @cindex synchronize with remote MIPS target
19297 Limit the maximum number of characters @value{GDBN} should ignore when
19298 it tries to synchronize with the remote target. The default is 10
19299 characters. Setting the limit to -1 means there's no limit.
19301 @item show syn-garbage-limit
19302 @kindex show syn-garbage-limit@r{, MIPS remote}
19303 Show the current limit on the number of characters to ignore when
19304 trying to synchronize with the remote system.
19306 @item set monitor-prompt @var{prompt}
19307 @kindex set monitor-prompt@r{, MIPS remote}
19308 @cindex remote monitor prompt
19309 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19310 remote monitor. The default depends on the target:
19320 @item show monitor-prompt
19321 @kindex show monitor-prompt@r{, MIPS remote}
19322 Show the current strings @value{GDBN} expects as the prompt from the
19325 @item set monitor-warnings
19326 @kindex set monitor-warnings@r{, MIPS remote}
19327 Enable or disable monitor warnings about hardware breakpoints. This
19328 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19329 display warning messages whose codes are returned by the @code{lsi}
19330 PMON monitor for breakpoint commands.
19332 @item show monitor-warnings
19333 @kindex show monitor-warnings@r{, MIPS remote}
19334 Show the current setting of printing monitor warnings.
19336 @item pmon @var{command}
19337 @kindex pmon@r{, MIPS remote}
19338 @cindex send PMON command
19339 This command allows sending an arbitrary @var{command} string to the
19340 monitor. The monitor must be in debug mode for this to work.
19343 @node OpenRISC 1000
19344 @subsection OpenRISC 1000
19345 @cindex OpenRISC 1000
19347 @cindex or1k boards
19348 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19349 about platform and commands.
19353 @kindex target jtag
19354 @item target jtag jtag://@var{host}:@var{port}
19356 Connects to remote JTAG server.
19357 JTAG remote server can be either an or1ksim or JTAG server,
19358 connected via parallel port to the board.
19360 Example: @code{target jtag jtag://localhost:9999}
19363 @item or1ksim @var{command}
19364 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19365 Simulator, proprietary commands can be executed.
19367 @kindex info or1k spr
19368 @item info or1k spr
19369 Displays spr groups.
19371 @item info or1k spr @var{group}
19372 @itemx info or1k spr @var{groupno}
19373 Displays register names in selected group.
19375 @item info or1k spr @var{group} @var{register}
19376 @itemx info or1k spr @var{register}
19377 @itemx info or1k spr @var{groupno} @var{registerno}
19378 @itemx info or1k spr @var{registerno}
19379 Shows information about specified spr register.
19382 @item spr @var{group} @var{register} @var{value}
19383 @itemx spr @var{register @var{value}}
19384 @itemx spr @var{groupno} @var{registerno @var{value}}
19385 @itemx spr @var{registerno @var{value}}
19386 Writes @var{value} to specified spr register.
19389 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19390 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19391 program execution and is thus much faster. Hardware breakpoints/watchpoint
19392 triggers can be set using:
19395 Load effective address/data
19397 Store effective address/data
19399 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19404 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19405 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19407 @code{htrace} commands:
19408 @cindex OpenRISC 1000 htrace
19411 @item hwatch @var{conditional}
19412 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19413 or Data. For example:
19415 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19417 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19421 Display information about current HW trace configuration.
19423 @item htrace trigger @var{conditional}
19424 Set starting criteria for HW trace.
19426 @item htrace qualifier @var{conditional}
19427 Set acquisition qualifier for HW trace.
19429 @item htrace stop @var{conditional}
19430 Set HW trace stopping criteria.
19432 @item htrace record [@var{data}]*
19433 Selects the data to be recorded, when qualifier is met and HW trace was
19436 @item htrace enable
19437 @itemx htrace disable
19438 Enables/disables the HW trace.
19440 @item htrace rewind [@var{filename}]
19441 Clears currently recorded trace data.
19443 If filename is specified, new trace file is made and any newly collected data
19444 will be written there.
19446 @item htrace print [@var{start} [@var{len}]]
19447 Prints trace buffer, using current record configuration.
19449 @item htrace mode continuous
19450 Set continuous trace mode.
19452 @item htrace mode suspend
19453 Set suspend trace mode.
19457 @node PowerPC Embedded
19458 @subsection PowerPC Embedded
19460 @cindex DVC register
19461 @value{GDBN} supports using the DVC (Data Value Compare) register to
19462 implement in hardware simple hardware watchpoint conditions of the form:
19465 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19466 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19469 The DVC register will be automatically used when @value{GDBN} detects
19470 such pattern in a condition expression, and the created watchpoint uses one
19471 debug register (either the @code{exact-watchpoints} option is on and the
19472 variable is scalar, or the variable has a length of one byte). This feature
19473 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19476 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19477 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19478 in which case watchpoints using only one debug register are created when
19479 watching variables of scalar types.
19481 You can create an artificial array to watch an arbitrary memory
19482 region using one of the following commands (@pxref{Expressions}):
19485 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19486 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19489 PowerPC embedded processors support masked watchpoints. See the discussion
19490 about the @code{mask} argument in @ref{Set Watchpoints}.
19492 @cindex ranged breakpoint
19493 PowerPC embedded processors support hardware accelerated
19494 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19495 the inferior whenever it executes an instruction at any address within
19496 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19497 use the @code{break-range} command.
19499 @value{GDBN} provides the following PowerPC-specific commands:
19502 @kindex break-range
19503 @item break-range @var{start-location}, @var{end-location}
19504 Set a breakpoint for an address range.
19505 @var{start-location} and @var{end-location} can specify a function name,
19506 a line number, an offset of lines from the current line or from the start
19507 location, or an address of an instruction (see @ref{Specify Location},
19508 for a list of all the possible ways to specify a @var{location}.)
19509 The breakpoint will stop execution of the inferior whenever it
19510 executes an instruction at any address within the specified range,
19511 (including @var{start-location} and @var{end-location}.)
19513 @kindex set powerpc
19514 @item set powerpc soft-float
19515 @itemx show powerpc soft-float
19516 Force @value{GDBN} to use (or not use) a software floating point calling
19517 convention. By default, @value{GDBN} selects the calling convention based
19518 on the selected architecture and the provided executable file.
19520 @item set powerpc vector-abi
19521 @itemx show powerpc vector-abi
19522 Force @value{GDBN} to use the specified calling convention for vector
19523 arguments and return values. The valid options are @samp{auto};
19524 @samp{generic}, to avoid vector registers even if they are present;
19525 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19526 registers. By default, @value{GDBN} selects the calling convention
19527 based on the selected architecture and the provided executable file.
19529 @item set powerpc exact-watchpoints
19530 @itemx show powerpc exact-watchpoints
19531 Allow @value{GDBN} to use only one debug register when watching a variable
19532 of scalar type, thus assuming that the variable is accessed through the
19533 address of its first byte.
19535 @kindex target dink32
19536 @item target dink32 @var{dev}
19537 DINK32 ROM monitor.
19539 @kindex target ppcbug
19540 @item target ppcbug @var{dev}
19541 @kindex target ppcbug1
19542 @item target ppcbug1 @var{dev}
19543 PPCBUG ROM monitor for PowerPC.
19546 @item target sds @var{dev}
19547 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19550 @cindex SDS protocol
19551 The following commands specific to the SDS protocol are supported
19555 @item set sdstimeout @var{nsec}
19556 @kindex set sdstimeout
19557 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19558 default is 2 seconds.
19560 @item show sdstimeout
19561 @kindex show sdstimeout
19562 Show the current value of the SDS timeout.
19564 @item sds @var{command}
19565 @kindex sds@r{, a command}
19566 Send the specified @var{command} string to the SDS monitor.
19571 @subsection HP PA Embedded
19575 @kindex target op50n
19576 @item target op50n @var{dev}
19577 OP50N monitor, running on an OKI HPPA board.
19579 @kindex target w89k
19580 @item target w89k @var{dev}
19581 W89K monitor, running on a Winbond HPPA board.
19586 @subsection Tsqware Sparclet
19590 @value{GDBN} enables developers to debug tasks running on
19591 Sparclet targets from a Unix host.
19592 @value{GDBN} uses code that runs on
19593 both the Unix host and on the Sparclet target. The program
19594 @code{@value{GDBP}} is installed and executed on the Unix host.
19597 @item remotetimeout @var{args}
19598 @kindex remotetimeout
19599 @value{GDBN} supports the option @code{remotetimeout}.
19600 This option is set by the user, and @var{args} represents the number of
19601 seconds @value{GDBN} waits for responses.
19604 @cindex compiling, on Sparclet
19605 When compiling for debugging, include the options @samp{-g} to get debug
19606 information and @samp{-Ttext} to relocate the program to where you wish to
19607 load it on the target. You may also want to add the options @samp{-n} or
19608 @samp{-N} in order to reduce the size of the sections. Example:
19611 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19614 You can use @code{objdump} to verify that the addresses are what you intended:
19617 sparclet-aout-objdump --headers --syms prog
19620 @cindex running, on Sparclet
19622 your Unix execution search path to find @value{GDBN}, you are ready to
19623 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19624 (or @code{sparclet-aout-gdb}, depending on your installation).
19626 @value{GDBN} comes up showing the prompt:
19633 * Sparclet File:: Setting the file to debug
19634 * Sparclet Connection:: Connecting to Sparclet
19635 * Sparclet Download:: Sparclet download
19636 * Sparclet Execution:: Running and debugging
19639 @node Sparclet File
19640 @subsubsection Setting File to Debug
19642 The @value{GDBN} command @code{file} lets you choose with program to debug.
19645 (gdbslet) file prog
19649 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19650 @value{GDBN} locates
19651 the file by searching the directories listed in the command search
19653 If the file was compiled with debug information (option @samp{-g}), source
19654 files will be searched as well.
19655 @value{GDBN} locates
19656 the source files by searching the directories listed in the directory search
19657 path (@pxref{Environment, ,Your Program's Environment}).
19659 to find a file, it displays a message such as:
19662 prog: No such file or directory.
19665 When this happens, add the appropriate directories to the search paths with
19666 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19667 @code{target} command again.
19669 @node Sparclet Connection
19670 @subsubsection Connecting to Sparclet
19672 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19673 To connect to a target on serial port ``@code{ttya}'', type:
19676 (gdbslet) target sparclet /dev/ttya
19677 Remote target sparclet connected to /dev/ttya
19678 main () at ../prog.c:3
19682 @value{GDBN} displays messages like these:
19688 @node Sparclet Download
19689 @subsubsection Sparclet Download
19691 @cindex download to Sparclet
19692 Once connected to the Sparclet target,
19693 you can use the @value{GDBN}
19694 @code{load} command to download the file from the host to the target.
19695 The file name and load offset should be given as arguments to the @code{load}
19697 Since the file format is aout, the program must be loaded to the starting
19698 address. You can use @code{objdump} to find out what this value is. The load
19699 offset is an offset which is added to the VMA (virtual memory address)
19700 of each of the file's sections.
19701 For instance, if the program
19702 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19703 and bss at 0x12010170, in @value{GDBN}, type:
19706 (gdbslet) load prog 0x12010000
19707 Loading section .text, size 0xdb0 vma 0x12010000
19710 If the code is loaded at a different address then what the program was linked
19711 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19712 to tell @value{GDBN} where to map the symbol table.
19714 @node Sparclet Execution
19715 @subsubsection Running and Debugging
19717 @cindex running and debugging Sparclet programs
19718 You can now begin debugging the task using @value{GDBN}'s execution control
19719 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19720 manual for the list of commands.
19724 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19726 Starting program: prog
19727 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19728 3 char *symarg = 0;
19730 4 char *execarg = "hello!";
19735 @subsection Fujitsu Sparclite
19739 @kindex target sparclite
19740 @item target sparclite @var{dev}
19741 Fujitsu sparclite boards, used only for the purpose of loading.
19742 You must use an additional command to debug the program.
19743 For example: target remote @var{dev} using @value{GDBN} standard
19749 @subsection Zilog Z8000
19752 @cindex simulator, Z8000
19753 @cindex Zilog Z8000 simulator
19755 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19758 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19759 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19760 segmented variant). The simulator recognizes which architecture is
19761 appropriate by inspecting the object code.
19764 @item target sim @var{args}
19766 @kindex target sim@r{, with Z8000}
19767 Debug programs on a simulated CPU. If the simulator supports setup
19768 options, specify them via @var{args}.
19772 After specifying this target, you can debug programs for the simulated
19773 CPU in the same style as programs for your host computer; use the
19774 @code{file} command to load a new program image, the @code{run} command
19775 to run your program, and so on.
19777 As well as making available all the usual machine registers
19778 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19779 additional items of information as specially named registers:
19784 Counts clock-ticks in the simulator.
19787 Counts instructions run in the simulator.
19790 Execution time in 60ths of a second.
19794 You can refer to these values in @value{GDBN} expressions with the usual
19795 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19796 conditional breakpoint that suspends only after at least 5000
19797 simulated clock ticks.
19800 @subsection Atmel AVR
19803 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19804 following AVR-specific commands:
19807 @item info io_registers
19808 @kindex info io_registers@r{, AVR}
19809 @cindex I/O registers (Atmel AVR)
19810 This command displays information about the AVR I/O registers. For
19811 each register, @value{GDBN} prints its number and value.
19818 When configured for debugging CRIS, @value{GDBN} provides the
19819 following CRIS-specific commands:
19822 @item set cris-version @var{ver}
19823 @cindex CRIS version
19824 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19825 The CRIS version affects register names and sizes. This command is useful in
19826 case autodetection of the CRIS version fails.
19828 @item show cris-version
19829 Show the current CRIS version.
19831 @item set cris-dwarf2-cfi
19832 @cindex DWARF-2 CFI and CRIS
19833 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19834 Change to @samp{off} when using @code{gcc-cris} whose version is below
19837 @item show cris-dwarf2-cfi
19838 Show the current state of using DWARF-2 CFI.
19840 @item set cris-mode @var{mode}
19842 Set the current CRIS mode to @var{mode}. It should only be changed when
19843 debugging in guru mode, in which case it should be set to
19844 @samp{guru} (the default is @samp{normal}).
19846 @item show cris-mode
19847 Show the current CRIS mode.
19851 @subsection Renesas Super-H
19854 For the Renesas Super-H processor, @value{GDBN} provides these
19859 @kindex regs@r{, Super-H}
19860 Show the values of all Super-H registers.
19862 @item set sh calling-convention @var{convention}
19863 @kindex set sh calling-convention
19864 Set the calling-convention used when calling functions from @value{GDBN}.
19865 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19866 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19867 convention. If the DWARF-2 information of the called function specifies
19868 that the function follows the Renesas calling convention, the function
19869 is called using the Renesas calling convention. If the calling convention
19870 is set to @samp{renesas}, the Renesas calling convention is always used,
19871 regardless of the DWARF-2 information. This can be used to override the
19872 default of @samp{gcc} if debug information is missing, or the compiler
19873 does not emit the DWARF-2 calling convention entry for a function.
19875 @item show sh calling-convention
19876 @kindex show sh calling-convention
19877 Show the current calling convention setting.
19882 @node Architectures
19883 @section Architectures
19885 This section describes characteristics of architectures that affect
19886 all uses of @value{GDBN} with the architecture, both native and cross.
19893 * HPPA:: HP PA architecture
19894 * SPU:: Cell Broadband Engine SPU architecture
19899 @subsection x86 Architecture-specific Issues
19902 @item set struct-convention @var{mode}
19903 @kindex set struct-convention
19904 @cindex struct return convention
19905 @cindex struct/union returned in registers
19906 Set the convention used by the inferior to return @code{struct}s and
19907 @code{union}s from functions to @var{mode}. Possible values of
19908 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19909 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19910 are returned on the stack, while @code{"reg"} means that a
19911 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19912 be returned in a register.
19914 @item show struct-convention
19915 @kindex show struct-convention
19916 Show the current setting of the convention to return @code{struct}s
19925 @kindex set rstack_high_address
19926 @cindex AMD 29K register stack
19927 @cindex register stack, AMD29K
19928 @item set rstack_high_address @var{address}
19929 On AMD 29000 family processors, registers are saved in a separate
19930 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19931 extent of this stack. Normally, @value{GDBN} just assumes that the
19932 stack is ``large enough''. This may result in @value{GDBN} referencing
19933 memory locations that do not exist. If necessary, you can get around
19934 this problem by specifying the ending address of the register stack with
19935 the @code{set rstack_high_address} command. The argument should be an
19936 address, which you probably want to precede with @samp{0x} to specify in
19939 @kindex show rstack_high_address
19940 @item show rstack_high_address
19941 Display the current limit of the register stack, on AMD 29000 family
19949 See the following section.
19954 @cindex stack on Alpha
19955 @cindex stack on MIPS
19956 @cindex Alpha stack
19958 Alpha- and MIPS-based computers use an unusual stack frame, which
19959 sometimes requires @value{GDBN} to search backward in the object code to
19960 find the beginning of a function.
19962 @cindex response time, MIPS debugging
19963 To improve response time (especially for embedded applications, where
19964 @value{GDBN} may be restricted to a slow serial line for this search)
19965 you may want to limit the size of this search, using one of these
19969 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19970 @item set heuristic-fence-post @var{limit}
19971 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19972 search for the beginning of a function. A value of @var{0} (the
19973 default) means there is no limit. However, except for @var{0}, the
19974 larger the limit the more bytes @code{heuristic-fence-post} must search
19975 and therefore the longer it takes to run. You should only need to use
19976 this command when debugging a stripped executable.
19978 @item show heuristic-fence-post
19979 Display the current limit.
19983 These commands are available @emph{only} when @value{GDBN} is configured
19984 for debugging programs on Alpha or MIPS processors.
19986 Several MIPS-specific commands are available when debugging MIPS
19990 @item set mips abi @var{arg}
19991 @kindex set mips abi
19992 @cindex set ABI for MIPS
19993 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19994 values of @var{arg} are:
19998 The default ABI associated with the current binary (this is the
20008 @item show mips abi
20009 @kindex show mips abi
20010 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20013 @itemx show mipsfpu
20014 @xref{MIPS Embedded, set mipsfpu}.
20016 @item set mips mask-address @var{arg}
20017 @kindex set mips mask-address
20018 @cindex MIPS addresses, masking
20019 This command determines whether the most-significant 32 bits of 64-bit
20020 MIPS addresses are masked off. The argument @var{arg} can be
20021 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20022 setting, which lets @value{GDBN} determine the correct value.
20024 @item show mips mask-address
20025 @kindex show mips mask-address
20026 Show whether the upper 32 bits of MIPS addresses are masked off or
20029 @item set remote-mips64-transfers-32bit-regs
20030 @kindex set remote-mips64-transfers-32bit-regs
20031 This command controls compatibility with 64-bit MIPS targets that
20032 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20033 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20034 and 64 bits for other registers, set this option to @samp{on}.
20036 @item show remote-mips64-transfers-32bit-regs
20037 @kindex show remote-mips64-transfers-32bit-regs
20038 Show the current setting of compatibility with older MIPS 64 targets.
20040 @item set debug mips
20041 @kindex set debug mips
20042 This command turns on and off debugging messages for the MIPS-specific
20043 target code in @value{GDBN}.
20045 @item show debug mips
20046 @kindex show debug mips
20047 Show the current setting of MIPS debugging messages.
20053 @cindex HPPA support
20055 When @value{GDBN} is debugging the HP PA architecture, it provides the
20056 following special commands:
20059 @item set debug hppa
20060 @kindex set debug hppa
20061 This command determines whether HPPA architecture-specific debugging
20062 messages are to be displayed.
20064 @item show debug hppa
20065 Show whether HPPA debugging messages are displayed.
20067 @item maint print unwind @var{address}
20068 @kindex maint print unwind@r{, HPPA}
20069 This command displays the contents of the unwind table entry at the
20070 given @var{address}.
20076 @subsection Cell Broadband Engine SPU architecture
20077 @cindex Cell Broadband Engine
20080 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20081 it provides the following special commands:
20084 @item info spu event
20086 Display SPU event facility status. Shows current event mask
20087 and pending event status.
20089 @item info spu signal
20090 Display SPU signal notification facility status. Shows pending
20091 signal-control word and signal notification mode of both signal
20092 notification channels.
20094 @item info spu mailbox
20095 Display SPU mailbox facility status. Shows all pending entries,
20096 in order of processing, in each of the SPU Write Outbound,
20097 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20100 Display MFC DMA status. Shows all pending commands in the MFC
20101 DMA queue. For each entry, opcode, tag, class IDs, effective
20102 and local store addresses and transfer size are shown.
20104 @item info spu proxydma
20105 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20106 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20107 and local store addresses and transfer size are shown.
20111 When @value{GDBN} is debugging a combined PowerPC/SPU application
20112 on the Cell Broadband Engine, it provides in addition the following
20116 @item set spu stop-on-load @var{arg}
20118 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20119 will give control to the user when a new SPE thread enters its @code{main}
20120 function. The default is @code{off}.
20122 @item show spu stop-on-load
20124 Show whether to stop for new SPE threads.
20126 @item set spu auto-flush-cache @var{arg}
20127 Set whether to automatically flush the software-managed cache. When set to
20128 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20129 cache to be flushed whenever SPE execution stops. This provides a consistent
20130 view of PowerPC memory that is accessed via the cache. If an application
20131 does not use the software-managed cache, this option has no effect.
20133 @item show spu auto-flush-cache
20134 Show whether to automatically flush the software-managed cache.
20139 @subsection PowerPC
20140 @cindex PowerPC architecture
20142 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20143 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20144 numbers stored in the floating point registers. These values must be stored
20145 in two consecutive registers, always starting at an even register like
20146 @code{f0} or @code{f2}.
20148 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20149 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20150 @code{f2} and @code{f3} for @code{$dl1} and so on.
20152 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20153 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20156 @node Controlling GDB
20157 @chapter Controlling @value{GDBN}
20159 You can alter the way @value{GDBN} interacts with you by using the
20160 @code{set} command. For commands controlling how @value{GDBN} displays
20161 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20166 * Editing:: Command editing
20167 * Command History:: Command history
20168 * Screen Size:: Screen size
20169 * Numbers:: Numbers
20170 * ABI:: Configuring the current ABI
20171 * Messages/Warnings:: Optional warnings and messages
20172 * Debugging Output:: Optional messages about internal happenings
20173 * Other Misc Settings:: Other Miscellaneous Settings
20181 @value{GDBN} indicates its readiness to read a command by printing a string
20182 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20183 can change the prompt string with the @code{set prompt} command. For
20184 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20185 the prompt in one of the @value{GDBN} sessions so that you can always tell
20186 which one you are talking to.
20188 @emph{Note:} @code{set prompt} does not add a space for you after the
20189 prompt you set. This allows you to set a prompt which ends in a space
20190 or a prompt that does not.
20194 @item set prompt @var{newprompt}
20195 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20197 @kindex show prompt
20199 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20202 Versions of @value{GDBN} that ship with Python scripting enabled have
20203 prompt extensions. The commands for interacting with these extensions
20207 @kindex set extended-prompt
20208 @item set extended-prompt @var{prompt}
20209 Set an extended prompt that allows for substitutions.
20210 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20211 substitution. Any escape sequences specified as part of the prompt
20212 string are replaced with the corresponding strings each time the prompt
20218 set extended-prompt Current working directory: \w (gdb)
20221 Note that when an extended-prompt is set, it takes control of the
20222 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20224 @kindex show extended-prompt
20225 @item show extended-prompt
20226 Prints the extended prompt. Any escape sequences specified as part of
20227 the prompt string with @code{set extended-prompt}, are replaced with the
20228 corresponding strings each time the prompt is displayed.
20232 @section Command Editing
20234 @cindex command line editing
20236 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20237 @sc{gnu} library provides consistent behavior for programs which provide a
20238 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20239 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20240 substitution, and a storage and recall of command history across
20241 debugging sessions.
20243 You may control the behavior of command line editing in @value{GDBN} with the
20244 command @code{set}.
20247 @kindex set editing
20250 @itemx set editing on
20251 Enable command line editing (enabled by default).
20253 @item set editing off
20254 Disable command line editing.
20256 @kindex show editing
20258 Show whether command line editing is enabled.
20261 @ifset SYSTEM_READLINE
20262 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20264 @ifclear SYSTEM_READLINE
20265 @xref{Command Line Editing},
20267 for more details about the Readline
20268 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20269 encouraged to read that chapter.
20271 @node Command History
20272 @section Command History
20273 @cindex command history
20275 @value{GDBN} can keep track of the commands you type during your
20276 debugging sessions, so that you can be certain of precisely what
20277 happened. Use these commands to manage the @value{GDBN} command
20280 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20281 package, to provide the history facility.
20282 @ifset SYSTEM_READLINE
20283 @xref{Using History Interactively, , , history, GNU History Library},
20285 @ifclear SYSTEM_READLINE
20286 @xref{Using History Interactively},
20288 for the detailed description of the History library.
20290 To issue a command to @value{GDBN} without affecting certain aspects of
20291 the state which is seen by users, prefix it with @samp{server }
20292 (@pxref{Server Prefix}). This
20293 means that this command will not affect the command history, nor will it
20294 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20295 pressed on a line by itself.
20297 @cindex @code{server}, command prefix
20298 The server prefix does not affect the recording of values into the value
20299 history; to print a value without recording it into the value history,
20300 use the @code{output} command instead of the @code{print} command.
20302 Here is the description of @value{GDBN} commands related to command
20306 @cindex history substitution
20307 @cindex history file
20308 @kindex set history filename
20309 @cindex @env{GDBHISTFILE}, environment variable
20310 @item set history filename @var{fname}
20311 Set the name of the @value{GDBN} command history file to @var{fname}.
20312 This is the file where @value{GDBN} reads an initial command history
20313 list, and where it writes the command history from this session when it
20314 exits. You can access this list through history expansion or through
20315 the history command editing characters listed below. This file defaults
20316 to the value of the environment variable @code{GDBHISTFILE}, or to
20317 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20320 @cindex save command history
20321 @kindex set history save
20322 @item set history save
20323 @itemx set history save on
20324 Record command history in a file, whose name may be specified with the
20325 @code{set history filename} command. By default, this option is disabled.
20327 @item set history save off
20328 Stop recording command history in a file.
20330 @cindex history size
20331 @kindex set history size
20332 @cindex @env{HISTSIZE}, environment variable
20333 @item set history size @var{size}
20334 Set the number of commands which @value{GDBN} keeps in its history list.
20335 This defaults to the value of the environment variable
20336 @code{HISTSIZE}, or to 256 if this variable is not set.
20339 History expansion assigns special meaning to the character @kbd{!}.
20340 @ifset SYSTEM_READLINE
20341 @xref{Event Designators, , , history, GNU History Library},
20343 @ifclear SYSTEM_READLINE
20344 @xref{Event Designators},
20348 @cindex history expansion, turn on/off
20349 Since @kbd{!} is also the logical not operator in C, history expansion
20350 is off by default. If you decide to enable history expansion with the
20351 @code{set history expansion on} command, you may sometimes need to
20352 follow @kbd{!} (when it is used as logical not, in an expression) with
20353 a space or a tab to prevent it from being expanded. The readline
20354 history facilities do not attempt substitution on the strings
20355 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20357 The commands to control history expansion are:
20360 @item set history expansion on
20361 @itemx set history expansion
20362 @kindex set history expansion
20363 Enable history expansion. History expansion is off by default.
20365 @item set history expansion off
20366 Disable history expansion.
20369 @kindex show history
20371 @itemx show history filename
20372 @itemx show history save
20373 @itemx show history size
20374 @itemx show history expansion
20375 These commands display the state of the @value{GDBN} history parameters.
20376 @code{show history} by itself displays all four states.
20381 @kindex show commands
20382 @cindex show last commands
20383 @cindex display command history
20384 @item show commands
20385 Display the last ten commands in the command history.
20387 @item show commands @var{n}
20388 Print ten commands centered on command number @var{n}.
20390 @item show commands +
20391 Print ten commands just after the commands last printed.
20395 @section Screen Size
20396 @cindex size of screen
20397 @cindex pauses in output
20399 Certain commands to @value{GDBN} may produce large amounts of
20400 information output to the screen. To help you read all of it,
20401 @value{GDBN} pauses and asks you for input at the end of each page of
20402 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20403 to discard the remaining output. Also, the screen width setting
20404 determines when to wrap lines of output. Depending on what is being
20405 printed, @value{GDBN} tries to break the line at a readable place,
20406 rather than simply letting it overflow onto the following line.
20408 Normally @value{GDBN} knows the size of the screen from the terminal
20409 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20410 together with the value of the @code{TERM} environment variable and the
20411 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20412 you can override it with the @code{set height} and @code{set
20419 @kindex show height
20420 @item set height @var{lpp}
20422 @itemx set width @var{cpl}
20424 These @code{set} commands specify a screen height of @var{lpp} lines and
20425 a screen width of @var{cpl} characters. The associated @code{show}
20426 commands display the current settings.
20428 If you specify a height of zero lines, @value{GDBN} does not pause during
20429 output no matter how long the output is. This is useful if output is to a
20430 file or to an editor buffer.
20432 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20433 from wrapping its output.
20435 @item set pagination on
20436 @itemx set pagination off
20437 @kindex set pagination
20438 Turn the output pagination on or off; the default is on. Turning
20439 pagination off is the alternative to @code{set height 0}. Note that
20440 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20441 Options, -batch}) also automatically disables pagination.
20443 @item show pagination
20444 @kindex show pagination
20445 Show the current pagination mode.
20450 @cindex number representation
20451 @cindex entering numbers
20453 You can always enter numbers in octal, decimal, or hexadecimal in
20454 @value{GDBN} by the usual conventions: octal numbers begin with
20455 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20456 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20457 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20458 10; likewise, the default display for numbers---when no particular
20459 format is specified---is base 10. You can change the default base for
20460 both input and output with the commands described below.
20463 @kindex set input-radix
20464 @item set input-radix @var{base}
20465 Set the default base for numeric input. Supported choices
20466 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20467 specified either unambiguously or using the current input radix; for
20471 set input-radix 012
20472 set input-radix 10.
20473 set input-radix 0xa
20477 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20478 leaves the input radix unchanged, no matter what it was, since
20479 @samp{10}, being without any leading or trailing signs of its base, is
20480 interpreted in the current radix. Thus, if the current radix is 16,
20481 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20484 @kindex set output-radix
20485 @item set output-radix @var{base}
20486 Set the default base for numeric display. Supported choices
20487 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20488 specified either unambiguously or using the current input radix.
20490 @kindex show input-radix
20491 @item show input-radix
20492 Display the current default base for numeric input.
20494 @kindex show output-radix
20495 @item show output-radix
20496 Display the current default base for numeric display.
20498 @item set radix @r{[}@var{base}@r{]}
20502 These commands set and show the default base for both input and output
20503 of numbers. @code{set radix} sets the radix of input and output to
20504 the same base; without an argument, it resets the radix back to its
20505 default value of 10.
20510 @section Configuring the Current ABI
20512 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20513 application automatically. However, sometimes you need to override its
20514 conclusions. Use these commands to manage @value{GDBN}'s view of the
20521 One @value{GDBN} configuration can debug binaries for multiple operating
20522 system targets, either via remote debugging or native emulation.
20523 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20524 but you can override its conclusion using the @code{set osabi} command.
20525 One example where this is useful is in debugging of binaries which use
20526 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20527 not have the same identifying marks that the standard C library for your
20532 Show the OS ABI currently in use.
20535 With no argument, show the list of registered available OS ABI's.
20537 @item set osabi @var{abi}
20538 Set the current OS ABI to @var{abi}.
20541 @cindex float promotion
20543 Generally, the way that an argument of type @code{float} is passed to a
20544 function depends on whether the function is prototyped. For a prototyped
20545 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20546 according to the architecture's convention for @code{float}. For unprototyped
20547 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20548 @code{double} and then passed.
20550 Unfortunately, some forms of debug information do not reliably indicate whether
20551 a function is prototyped. If @value{GDBN} calls a function that is not marked
20552 as prototyped, it consults @kbd{set coerce-float-to-double}.
20555 @kindex set coerce-float-to-double
20556 @item set coerce-float-to-double
20557 @itemx set coerce-float-to-double on
20558 Arguments of type @code{float} will be promoted to @code{double} when passed
20559 to an unprototyped function. This is the default setting.
20561 @item set coerce-float-to-double off
20562 Arguments of type @code{float} will be passed directly to unprototyped
20565 @kindex show coerce-float-to-double
20566 @item show coerce-float-to-double
20567 Show the current setting of promoting @code{float} to @code{double}.
20571 @kindex show cp-abi
20572 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20573 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20574 used to build your application. @value{GDBN} only fully supports
20575 programs with a single C@t{++} ABI; if your program contains code using
20576 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20577 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20578 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20579 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20580 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20581 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20586 Show the C@t{++} ABI currently in use.
20589 With no argument, show the list of supported C@t{++} ABI's.
20591 @item set cp-abi @var{abi}
20592 @itemx set cp-abi auto
20593 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20596 @node Messages/Warnings
20597 @section Optional Warnings and Messages
20599 @cindex verbose operation
20600 @cindex optional warnings
20601 By default, @value{GDBN} is silent about its inner workings. If you are
20602 running on a slow machine, you may want to use the @code{set verbose}
20603 command. This makes @value{GDBN} tell you when it does a lengthy
20604 internal operation, so you will not think it has crashed.
20606 Currently, the messages controlled by @code{set verbose} are those
20607 which announce that the symbol table for a source file is being read;
20608 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20611 @kindex set verbose
20612 @item set verbose on
20613 Enables @value{GDBN} output of certain informational messages.
20615 @item set verbose off
20616 Disables @value{GDBN} output of certain informational messages.
20618 @kindex show verbose
20620 Displays whether @code{set verbose} is on or off.
20623 By default, if @value{GDBN} encounters bugs in the symbol table of an
20624 object file, it is silent; but if you are debugging a compiler, you may
20625 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20630 @kindex set complaints
20631 @item set complaints @var{limit}
20632 Permits @value{GDBN} to output @var{limit} complaints about each type of
20633 unusual symbols before becoming silent about the problem. Set
20634 @var{limit} to zero to suppress all complaints; set it to a large number
20635 to prevent complaints from being suppressed.
20637 @kindex show complaints
20638 @item show complaints
20639 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20643 @anchor{confirmation requests}
20644 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20645 lot of stupid questions to confirm certain commands. For example, if
20646 you try to run a program which is already running:
20650 The program being debugged has been started already.
20651 Start it from the beginning? (y or n)
20654 If you are willing to unflinchingly face the consequences of your own
20655 commands, you can disable this ``feature'':
20659 @kindex set confirm
20661 @cindex confirmation
20662 @cindex stupid questions
20663 @item set confirm off
20664 Disables confirmation requests. Note that running @value{GDBN} with
20665 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20666 automatically disables confirmation requests.
20668 @item set confirm on
20669 Enables confirmation requests (the default).
20671 @kindex show confirm
20673 Displays state of confirmation requests.
20677 @cindex command tracing
20678 If you need to debug user-defined commands or sourced files you may find it
20679 useful to enable @dfn{command tracing}. In this mode each command will be
20680 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20681 quantity denoting the call depth of each command.
20684 @kindex set trace-commands
20685 @cindex command scripts, debugging
20686 @item set trace-commands on
20687 Enable command tracing.
20688 @item set trace-commands off
20689 Disable command tracing.
20690 @item show trace-commands
20691 Display the current state of command tracing.
20694 @node Debugging Output
20695 @section Optional Messages about Internal Happenings
20696 @cindex optional debugging messages
20698 @value{GDBN} has commands that enable optional debugging messages from
20699 various @value{GDBN} subsystems; normally these commands are of
20700 interest to @value{GDBN} maintainers, or when reporting a bug. This
20701 section documents those commands.
20704 @kindex set exec-done-display
20705 @item set exec-done-display
20706 Turns on or off the notification of asynchronous commands'
20707 completion. When on, @value{GDBN} will print a message when an
20708 asynchronous command finishes its execution. The default is off.
20709 @kindex show exec-done-display
20710 @item show exec-done-display
20711 Displays the current setting of asynchronous command completion
20714 @cindex gdbarch debugging info
20715 @cindex architecture debugging info
20716 @item set debug arch
20717 Turns on or off display of gdbarch debugging info. The default is off
20719 @item show debug arch
20720 Displays the current state of displaying gdbarch debugging info.
20721 @item set debug aix-thread
20722 @cindex AIX threads
20723 Display debugging messages about inner workings of the AIX thread
20725 @item show debug aix-thread
20726 Show the current state of AIX thread debugging info display.
20727 @item set debug check-physname
20729 Check the results of the ``physname'' computation. When reading DWARF
20730 debugging information for C@t{++}, @value{GDBN} attempts to compute
20731 each entity's name. @value{GDBN} can do this computation in two
20732 different ways, depending on exactly what information is present.
20733 When enabled, this setting causes @value{GDBN} to compute the names
20734 both ways and display any discrepancies.
20735 @item show debug check-physname
20736 Show the current state of ``physname'' checking.
20737 @item set debug dwarf2-die
20738 @cindex DWARF2 DIEs
20739 Dump DWARF2 DIEs after they are read in.
20740 The value is the number of nesting levels to print.
20741 A value of zero turns off the display.
20742 @item show debug dwarf2-die
20743 Show the current state of DWARF2 DIE debugging.
20744 @item set debug displaced
20745 @cindex displaced stepping debugging info
20746 Turns on or off display of @value{GDBN} debugging info for the
20747 displaced stepping support. The default is off.
20748 @item show debug displaced
20749 Displays the current state of displaying @value{GDBN} debugging info
20750 related to displaced stepping.
20751 @item set debug event
20752 @cindex event debugging info
20753 Turns on or off display of @value{GDBN} event debugging info. The
20755 @item show debug event
20756 Displays the current state of displaying @value{GDBN} event debugging
20758 @item set debug expression
20759 @cindex expression debugging info
20760 Turns on or off display of debugging info about @value{GDBN}
20761 expression parsing. The default is off.
20762 @item show debug expression
20763 Displays the current state of displaying debugging info about
20764 @value{GDBN} expression parsing.
20765 @item set debug frame
20766 @cindex frame debugging info
20767 Turns on or off display of @value{GDBN} frame debugging info. The
20769 @item show debug frame
20770 Displays the current state of displaying @value{GDBN} frame debugging
20772 @item set debug gnu-nat
20773 @cindex @sc{gnu}/Hurd debug messages
20774 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20775 @item show debug gnu-nat
20776 Show the current state of @sc{gnu}/Hurd debugging messages.
20777 @item set debug infrun
20778 @cindex inferior debugging info
20779 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20780 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20781 for implementing operations such as single-stepping the inferior.
20782 @item show debug infrun
20783 Displays the current state of @value{GDBN} inferior debugging.
20784 @item set debug jit
20785 @cindex just-in-time compilation, debugging messages
20786 Turns on or off debugging messages from JIT debug support.
20787 @item show debug jit
20788 Displays the current state of @value{GDBN} JIT debugging.
20789 @item set debug lin-lwp
20790 @cindex @sc{gnu}/Linux LWP debug messages
20791 @cindex Linux lightweight processes
20792 Turns on or off debugging messages from the Linux LWP debug support.
20793 @item show debug lin-lwp
20794 Show the current state of Linux LWP debugging messages.
20795 @item set debug observer
20796 @cindex observer debugging info
20797 Turns on or off display of @value{GDBN} observer debugging. This
20798 includes info such as the notification of observable events.
20799 @item show debug observer
20800 Displays the current state of observer debugging.
20801 @item set debug overload
20802 @cindex C@t{++} overload debugging info
20803 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20804 info. This includes info such as ranking of functions, etc. The default
20806 @item show debug overload
20807 Displays the current state of displaying @value{GDBN} C@t{++} overload
20809 @cindex expression parser, debugging info
20810 @cindex debug expression parser
20811 @item set debug parser
20812 Turns on or off the display of expression parser debugging output.
20813 Internally, this sets the @code{yydebug} variable in the expression
20814 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20815 details. The default is off.
20816 @item show debug parser
20817 Show the current state of expression parser debugging.
20818 @cindex packets, reporting on stdout
20819 @cindex serial connections, debugging
20820 @cindex debug remote protocol
20821 @cindex remote protocol debugging
20822 @cindex display remote packets
20823 @item set debug remote
20824 Turns on or off display of reports on all packets sent back and forth across
20825 the serial line to the remote machine. The info is printed on the
20826 @value{GDBN} standard output stream. The default is off.
20827 @item show debug remote
20828 Displays the state of display of remote packets.
20829 @item set debug serial
20830 Turns on or off display of @value{GDBN} serial debugging info. The
20832 @item show debug serial
20833 Displays the current state of displaying @value{GDBN} serial debugging
20835 @item set debug solib-frv
20836 @cindex FR-V shared-library debugging
20837 Turns on or off debugging messages for FR-V shared-library code.
20838 @item show debug solib-frv
20839 Display the current state of FR-V shared-library code debugging
20841 @item set debug target
20842 @cindex target debugging info
20843 Turns on or off display of @value{GDBN} target debugging info. This info
20844 includes what is going on at the target level of GDB, as it happens. The
20845 default is 0. Set it to 1 to track events, and to 2 to also track the
20846 value of large memory transfers. Changes to this flag do not take effect
20847 until the next time you connect to a target or use the @code{run} command.
20848 @item show debug target
20849 Displays the current state of displaying @value{GDBN} target debugging
20851 @item set debug timestamp
20852 @cindex timestampping debugging info
20853 Turns on or off display of timestamps with @value{GDBN} debugging info.
20854 When enabled, seconds and microseconds are displayed before each debugging
20856 @item show debug timestamp
20857 Displays the current state of displaying timestamps with @value{GDBN}
20859 @item set debugvarobj
20860 @cindex variable object debugging info
20861 Turns on or off display of @value{GDBN} variable object debugging
20862 info. The default is off.
20863 @item show debugvarobj
20864 Displays the current state of displaying @value{GDBN} variable object
20866 @item set debug xml
20867 @cindex XML parser debugging
20868 Turns on or off debugging messages for built-in XML parsers.
20869 @item show debug xml
20870 Displays the current state of XML debugging messages.
20873 @node Other Misc Settings
20874 @section Other Miscellaneous Settings
20875 @cindex miscellaneous settings
20878 @kindex set interactive-mode
20879 @item set interactive-mode
20880 If @code{on}, forces @value{GDBN} to assume that GDB was started
20881 in a terminal. In practice, this means that @value{GDBN} should wait
20882 for the user to answer queries generated by commands entered at
20883 the command prompt. If @code{off}, forces @value{GDBN} to operate
20884 in the opposite mode, and it uses the default answers to all queries.
20885 If @code{auto} (the default), @value{GDBN} tries to determine whether
20886 its standard input is a terminal, and works in interactive-mode if it
20887 is, non-interactively otherwise.
20889 In the vast majority of cases, the debugger should be able to guess
20890 correctly which mode should be used. But this setting can be useful
20891 in certain specific cases, such as running a MinGW @value{GDBN}
20892 inside a cygwin window.
20894 @kindex show interactive-mode
20895 @item show interactive-mode
20896 Displays whether the debugger is operating in interactive mode or not.
20899 @node Extending GDB
20900 @chapter Extending @value{GDBN}
20901 @cindex extending GDB
20903 @value{GDBN} provides three mechanisms for extension. The first is based
20904 on composition of @value{GDBN} commands, the second is based on the
20905 Python scripting language, and the third is for defining new aliases of
20908 To facilitate the use of the first two extensions, @value{GDBN} is capable
20909 of evaluating the contents of a file. When doing so, @value{GDBN}
20910 can recognize which scripting language is being used by looking at
20911 the filename extension. Files with an unrecognized filename extension
20912 are always treated as a @value{GDBN} Command Files.
20913 @xref{Command Files,, Command files}.
20915 You can control how @value{GDBN} evaluates these files with the following
20919 @kindex set script-extension
20920 @kindex show script-extension
20921 @item set script-extension off
20922 All scripts are always evaluated as @value{GDBN} Command Files.
20924 @item set script-extension soft
20925 The debugger determines the scripting language based on filename
20926 extension. If this scripting language is supported, @value{GDBN}
20927 evaluates the script using that language. Otherwise, it evaluates
20928 the file as a @value{GDBN} Command File.
20930 @item set script-extension strict
20931 The debugger determines the scripting language based on filename
20932 extension, and evaluates the script using that language. If the
20933 language is not supported, then the evaluation fails.
20935 @item show script-extension
20936 Display the current value of the @code{script-extension} option.
20941 * Sequences:: Canned Sequences of Commands
20942 * Python:: Scripting @value{GDBN} using Python
20943 * Aliases:: Creating new spellings of existing commands
20947 @section Canned Sequences of Commands
20949 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20950 Command Lists}), @value{GDBN} provides two ways to store sequences of
20951 commands for execution as a unit: user-defined commands and command
20955 * Define:: How to define your own commands
20956 * Hooks:: Hooks for user-defined commands
20957 * Command Files:: How to write scripts of commands to be stored in a file
20958 * Output:: Commands for controlled output
20962 @subsection User-defined Commands
20964 @cindex user-defined command
20965 @cindex arguments, to user-defined commands
20966 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20967 which you assign a new name as a command. This is done with the
20968 @code{define} command. User commands may accept up to 10 arguments
20969 separated by whitespace. Arguments are accessed within the user command
20970 via @code{$arg0@dots{}$arg9}. A trivial example:
20974 print $arg0 + $arg1 + $arg2
20979 To execute the command use:
20986 This defines the command @code{adder}, which prints the sum of
20987 its three arguments. Note the arguments are text substitutions, so they may
20988 reference variables, use complex expressions, or even perform inferior
20991 @cindex argument count in user-defined commands
20992 @cindex how many arguments (user-defined commands)
20993 In addition, @code{$argc} may be used to find out how many arguments have
20994 been passed. This expands to a number in the range 0@dots{}10.
20999 print $arg0 + $arg1
21002 print $arg0 + $arg1 + $arg2
21010 @item define @var{commandname}
21011 Define a command named @var{commandname}. If there is already a command
21012 by that name, you are asked to confirm that you want to redefine it.
21013 @var{commandname} may be a bare command name consisting of letters,
21014 numbers, dashes, and underscores. It may also start with any predefined
21015 prefix command. For example, @samp{define target my-target} creates
21016 a user-defined @samp{target my-target} command.
21018 The definition of the command is made up of other @value{GDBN} command lines,
21019 which are given following the @code{define} command. The end of these
21020 commands is marked by a line containing @code{end}.
21023 @kindex end@r{ (user-defined commands)}
21024 @item document @var{commandname}
21025 Document the user-defined command @var{commandname}, so that it can be
21026 accessed by @code{help}. The command @var{commandname} must already be
21027 defined. This command reads lines of documentation just as @code{define}
21028 reads the lines of the command definition, ending with @code{end}.
21029 After the @code{document} command is finished, @code{help} on command
21030 @var{commandname} displays the documentation you have written.
21032 You may use the @code{document} command again to change the
21033 documentation of a command. Redefining the command with @code{define}
21034 does not change the documentation.
21036 @kindex dont-repeat
21037 @cindex don't repeat command
21039 Used inside a user-defined command, this tells @value{GDBN} that this
21040 command should not be repeated when the user hits @key{RET}
21041 (@pxref{Command Syntax, repeat last command}).
21043 @kindex help user-defined
21044 @item help user-defined
21045 List all user-defined commands, with the first line of the documentation
21050 @itemx show user @var{commandname}
21051 Display the @value{GDBN} commands used to define @var{commandname} (but
21052 not its documentation). If no @var{commandname} is given, display the
21053 definitions for all user-defined commands.
21055 @cindex infinite recursion in user-defined commands
21056 @kindex show max-user-call-depth
21057 @kindex set max-user-call-depth
21058 @item show max-user-call-depth
21059 @itemx set max-user-call-depth
21060 The value of @code{max-user-call-depth} controls how many recursion
21061 levels are allowed in user-defined commands before @value{GDBN} suspects an
21062 infinite recursion and aborts the command.
21065 In addition to the above commands, user-defined commands frequently
21066 use control flow commands, described in @ref{Command Files}.
21068 When user-defined commands are executed, the
21069 commands of the definition are not printed. An error in any command
21070 stops execution of the user-defined command.
21072 If used interactively, commands that would ask for confirmation proceed
21073 without asking when used inside a user-defined command. Many @value{GDBN}
21074 commands that normally print messages to say what they are doing omit the
21075 messages when used in a user-defined command.
21078 @subsection User-defined Command Hooks
21079 @cindex command hooks
21080 @cindex hooks, for commands
21081 @cindex hooks, pre-command
21084 You may define @dfn{hooks}, which are a special kind of user-defined
21085 command. Whenever you run the command @samp{foo}, if the user-defined
21086 command @samp{hook-foo} exists, it is executed (with no arguments)
21087 before that command.
21089 @cindex hooks, post-command
21091 A hook may also be defined which is run after the command you executed.
21092 Whenever you run the command @samp{foo}, if the user-defined command
21093 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21094 that command. Post-execution hooks may exist simultaneously with
21095 pre-execution hooks, for the same command.
21097 It is valid for a hook to call the command which it hooks. If this
21098 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21100 @c It would be nice if hookpost could be passed a parameter indicating
21101 @c if the command it hooks executed properly or not. FIXME!
21103 @kindex stop@r{, a pseudo-command}
21104 In addition, a pseudo-command, @samp{stop} exists. Defining
21105 (@samp{hook-stop}) makes the associated commands execute every time
21106 execution stops in your program: before breakpoint commands are run,
21107 displays are printed, or the stack frame is printed.
21109 For example, to ignore @code{SIGALRM} signals while
21110 single-stepping, but treat them normally during normal execution,
21115 handle SIGALRM nopass
21119 handle SIGALRM pass
21122 define hook-continue
21123 handle SIGALRM pass
21127 As a further example, to hook at the beginning and end of the @code{echo}
21128 command, and to add extra text to the beginning and end of the message,
21136 define hookpost-echo
21140 (@value{GDBP}) echo Hello World
21141 <<<---Hello World--->>>
21146 You can define a hook for any single-word command in @value{GDBN}, but
21147 not for command aliases; you should define a hook for the basic command
21148 name, e.g.@: @code{backtrace} rather than @code{bt}.
21149 @c FIXME! So how does Joe User discover whether a command is an alias
21151 You can hook a multi-word command by adding @code{hook-} or
21152 @code{hookpost-} to the last word of the command, e.g.@:
21153 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21155 If an error occurs during the execution of your hook, execution of
21156 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21157 (before the command that you actually typed had a chance to run).
21159 If you try to define a hook which does not match any known command, you
21160 get a warning from the @code{define} command.
21162 @node Command Files
21163 @subsection Command Files
21165 @cindex command files
21166 @cindex scripting commands
21167 A command file for @value{GDBN} is a text file made of lines that are
21168 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21169 also be included. An empty line in a command file does nothing; it
21170 does not mean to repeat the last command, as it would from the
21173 You can request the execution of a command file with the @code{source}
21174 command. Note that the @code{source} command is also used to evaluate
21175 scripts that are not Command Files. The exact behavior can be configured
21176 using the @code{script-extension} setting.
21177 @xref{Extending GDB,, Extending GDB}.
21181 @cindex execute commands from a file
21182 @item source [-s] [-v] @var{filename}
21183 Execute the command file @var{filename}.
21186 The lines in a command file are generally executed sequentially,
21187 unless the order of execution is changed by one of the
21188 @emph{flow-control commands} described below. The commands are not
21189 printed as they are executed. An error in any command terminates
21190 execution of the command file and control is returned to the console.
21192 @value{GDBN} first searches for @var{filename} in the current directory.
21193 If the file is not found there, and @var{filename} does not specify a
21194 directory, then @value{GDBN} also looks for the file on the source search path
21195 (specified with the @samp{directory} command);
21196 except that @file{$cdir} is not searched because the compilation directory
21197 is not relevant to scripts.
21199 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21200 on the search path even if @var{filename} specifies a directory.
21201 The search is done by appending @var{filename} to each element of the
21202 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21203 and the search path contains @file{/home/user} then @value{GDBN} will
21204 look for the script @file{/home/user/mylib/myscript}.
21205 The search is also done if @var{filename} is an absolute path.
21206 For example, if @var{filename} is @file{/tmp/myscript} and
21207 the search path contains @file{/home/user} then @value{GDBN} will
21208 look for the script @file{/home/user/tmp/myscript}.
21209 For DOS-like systems, if @var{filename} contains a drive specification,
21210 it is stripped before concatenation. For example, if @var{filename} is
21211 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21212 will look for the script @file{c:/tmp/myscript}.
21214 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21215 each command as it is executed. The option must be given before
21216 @var{filename}, and is interpreted as part of the filename anywhere else.
21218 Commands that would ask for confirmation if used interactively proceed
21219 without asking when used in a command file. Many @value{GDBN} commands that
21220 normally print messages to say what they are doing omit the messages
21221 when called from command files.
21223 @value{GDBN} also accepts command input from standard input. In this
21224 mode, normal output goes to standard output and error output goes to
21225 standard error. Errors in a command file supplied on standard input do
21226 not terminate execution of the command file---execution continues with
21230 gdb < cmds > log 2>&1
21233 (The syntax above will vary depending on the shell used.) This example
21234 will execute commands from the file @file{cmds}. All output and errors
21235 would be directed to @file{log}.
21237 Since commands stored on command files tend to be more general than
21238 commands typed interactively, they frequently need to deal with
21239 complicated situations, such as different or unexpected values of
21240 variables and symbols, changes in how the program being debugged is
21241 built, etc. @value{GDBN} provides a set of flow-control commands to
21242 deal with these complexities. Using these commands, you can write
21243 complex scripts that loop over data structures, execute commands
21244 conditionally, etc.
21251 This command allows to include in your script conditionally executed
21252 commands. The @code{if} command takes a single argument, which is an
21253 expression to evaluate. It is followed by a series of commands that
21254 are executed only if the expression is true (its value is nonzero).
21255 There can then optionally be an @code{else} line, followed by a series
21256 of commands that are only executed if the expression was false. The
21257 end of the list is marked by a line containing @code{end}.
21261 This command allows to write loops. Its syntax is similar to
21262 @code{if}: the command takes a single argument, which is an expression
21263 to evaluate, and must be followed by the commands to execute, one per
21264 line, terminated by an @code{end}. These commands are called the
21265 @dfn{body} of the loop. The commands in the body of @code{while} are
21266 executed repeatedly as long as the expression evaluates to true.
21270 This command exits the @code{while} loop in whose body it is included.
21271 Execution of the script continues after that @code{while}s @code{end}
21274 @kindex loop_continue
21275 @item loop_continue
21276 This command skips the execution of the rest of the body of commands
21277 in the @code{while} loop in whose body it is included. Execution
21278 branches to the beginning of the @code{while} loop, where it evaluates
21279 the controlling expression.
21281 @kindex end@r{ (if/else/while commands)}
21283 Terminate the block of commands that are the body of @code{if},
21284 @code{else}, or @code{while} flow-control commands.
21289 @subsection Commands for Controlled Output
21291 During the execution of a command file or a user-defined command, normal
21292 @value{GDBN} output is suppressed; the only output that appears is what is
21293 explicitly printed by the commands in the definition. This section
21294 describes three commands useful for generating exactly the output you
21299 @item echo @var{text}
21300 @c I do not consider backslash-space a standard C escape sequence
21301 @c because it is not in ANSI.
21302 Print @var{text}. Nonprinting characters can be included in
21303 @var{text} using C escape sequences, such as @samp{\n} to print a
21304 newline. @strong{No newline is printed unless you specify one.}
21305 In addition to the standard C escape sequences, a backslash followed
21306 by a space stands for a space. This is useful for displaying a
21307 string with spaces at the beginning or the end, since leading and
21308 trailing spaces are otherwise trimmed from all arguments.
21309 To print @samp{@w{ }and foo =@w{ }}, use the command
21310 @samp{echo \@w{ }and foo = \@w{ }}.
21312 A backslash at the end of @var{text} can be used, as in C, to continue
21313 the command onto subsequent lines. For example,
21316 echo This is some text\n\
21317 which is continued\n\
21318 onto several lines.\n
21321 produces the same output as
21324 echo This is some text\n
21325 echo which is continued\n
21326 echo onto several lines.\n
21330 @item output @var{expression}
21331 Print the value of @var{expression} and nothing but that value: no
21332 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21333 value history either. @xref{Expressions, ,Expressions}, for more information
21336 @item output/@var{fmt} @var{expression}
21337 Print the value of @var{expression} in format @var{fmt}. You can use
21338 the same formats as for @code{print}. @xref{Output Formats,,Output
21339 Formats}, for more information.
21342 @item printf @var{template}, @var{expressions}@dots{}
21343 Print the values of one or more @var{expressions} under the control of
21344 the string @var{template}. To print several values, make
21345 @var{expressions} be a comma-separated list of individual expressions,
21346 which may be either numbers or pointers. Their values are printed as
21347 specified by @var{template}, exactly as a C program would do by
21348 executing the code below:
21351 printf (@var{template}, @var{expressions}@dots{});
21354 As in @code{C} @code{printf}, ordinary characters in @var{template}
21355 are printed verbatim, while @dfn{conversion specification} introduced
21356 by the @samp{%} character cause subsequent @var{expressions} to be
21357 evaluated, their values converted and formatted according to type and
21358 style information encoded in the conversion specifications, and then
21361 For example, you can print two values in hex like this:
21364 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21367 @code{printf} supports all the standard @code{C} conversion
21368 specifications, including the flags and modifiers between the @samp{%}
21369 character and the conversion letter, with the following exceptions:
21373 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21376 The modifier @samp{*} is not supported for specifying precision or
21380 The @samp{'} flag (for separation of digits into groups according to
21381 @code{LC_NUMERIC'}) is not supported.
21384 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21388 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21391 The conversion letters @samp{a} and @samp{A} are not supported.
21395 Note that the @samp{ll} type modifier is supported only if the
21396 underlying @code{C} implementation used to build @value{GDBN} supports
21397 the @code{long long int} type, and the @samp{L} type modifier is
21398 supported only if @code{long double} type is available.
21400 As in @code{C}, @code{printf} supports simple backslash-escape
21401 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21402 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21403 single character. Octal and hexadecimal escape sequences are not
21406 Additionally, @code{printf} supports conversion specifications for DFP
21407 (@dfn{Decimal Floating Point}) types using the following length modifiers
21408 together with a floating point specifier.
21413 @samp{H} for printing @code{Decimal32} types.
21416 @samp{D} for printing @code{Decimal64} types.
21419 @samp{DD} for printing @code{Decimal128} types.
21422 If the underlying @code{C} implementation used to build @value{GDBN} has
21423 support for the three length modifiers for DFP types, other modifiers
21424 such as width and precision will also be available for @value{GDBN} to use.
21426 In case there is no such @code{C} support, no additional modifiers will be
21427 available and the value will be printed in the standard way.
21429 Here's an example of printing DFP types using the above conversion letters:
21431 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21435 @item eval @var{template}, @var{expressions}@dots{}
21436 Convert the values of one or more @var{expressions} under the control of
21437 the string @var{template} to a command line, and call it.
21442 @section Scripting @value{GDBN} using Python
21443 @cindex python scripting
21444 @cindex scripting with python
21446 You can script @value{GDBN} using the @uref{http://www.python.org/,
21447 Python programming language}. This feature is available only if
21448 @value{GDBN} was configured using @option{--with-python}.
21450 @cindex python directory
21451 Python scripts used by @value{GDBN} should be installed in
21452 @file{@var{data-directory}/python}, where @var{data-directory} is
21453 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21454 This directory, known as the @dfn{python directory},
21455 is automatically added to the Python Search Path in order to allow
21456 the Python interpreter to locate all scripts installed at this location.
21458 Additionally, @value{GDBN} commands and convenience functions which
21459 are written in Python and are located in the
21460 @file{@var{data-directory}/python/gdb/command} or
21461 @file{@var{data-directory}/python/gdb/function} directories are
21462 automatically imported when @value{GDBN} starts.
21465 * Python Commands:: Accessing Python from @value{GDBN}.
21466 * Python API:: Accessing @value{GDBN} from Python.
21467 * Auto-loading:: Automatically loading Python code.
21468 * Python modules:: Python modules provided by @value{GDBN}.
21471 @node Python Commands
21472 @subsection Python Commands
21473 @cindex python commands
21474 @cindex commands to access python
21476 @value{GDBN} provides one command for accessing the Python interpreter,
21477 and one related setting:
21481 @item python @r{[}@var{code}@r{]}
21482 The @code{python} command can be used to evaluate Python code.
21484 If given an argument, the @code{python} command will evaluate the
21485 argument as a Python command. For example:
21488 (@value{GDBP}) python print 23
21492 If you do not provide an argument to @code{python}, it will act as a
21493 multi-line command, like @code{define}. In this case, the Python
21494 script is made up of subsequent command lines, given after the
21495 @code{python} command. This command list is terminated using a line
21496 containing @code{end}. For example:
21499 (@value{GDBP}) python
21501 End with a line saying just "end".
21507 @kindex set python print-stack
21508 @item set python print-stack
21509 By default, @value{GDBN} will print only the message component of a
21510 Python exception when an error occurs in a Python script. This can be
21511 controlled using @code{set python print-stack}: if @code{full}, then
21512 full Python stack printing is enabled; if @code{none}, then Python stack
21513 and message printing is disabled; if @code{message}, the default, only
21514 the message component of the error is printed.
21517 It is also possible to execute a Python script from the @value{GDBN}
21521 @item source @file{script-name}
21522 The script name must end with @samp{.py} and @value{GDBN} must be configured
21523 to recognize the script language based on filename extension using
21524 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21526 @item python execfile ("script-name")
21527 This method is based on the @code{execfile} Python built-in function,
21528 and thus is always available.
21532 @subsection Python API
21534 @cindex programming in python
21536 @cindex python stdout
21537 @cindex python pagination
21538 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21539 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21540 A Python program which outputs to one of these streams may have its
21541 output interrupted by the user (@pxref{Screen Size}). In this
21542 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21545 * Basic Python:: Basic Python Functions.
21546 * Exception Handling:: How Python exceptions are translated.
21547 * Values From Inferior:: Python representation of values.
21548 * Types In Python:: Python representation of types.
21549 * Pretty Printing API:: Pretty-printing values.
21550 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21551 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21552 * Inferiors In Python:: Python representation of inferiors (processes)
21553 * Events In Python:: Listening for events from @value{GDBN}.
21554 * Threads In Python:: Accessing inferior threads from Python.
21555 * Commands In Python:: Implementing new commands in Python.
21556 * Parameters In Python:: Adding new @value{GDBN} parameters.
21557 * Functions In Python:: Writing new convenience functions.
21558 * Progspaces In Python:: Program spaces.
21559 * Objfiles In Python:: Object files.
21560 * Frames In Python:: Accessing inferior stack frames from Python.
21561 * Blocks In Python:: Accessing frame blocks from Python.
21562 * Symbols In Python:: Python representation of symbols.
21563 * Symbol Tables In Python:: Python representation of symbol tables.
21564 * Lazy Strings In Python:: Python representation of lazy strings.
21565 * Breakpoints In Python:: Manipulating breakpoints using Python.
21566 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21571 @subsubsection Basic Python
21573 @cindex python functions
21574 @cindex python module
21576 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21577 methods and classes added by @value{GDBN} are placed in this module.
21578 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21579 use in all scripts evaluated by the @code{python} command.
21581 @findex gdb.PYTHONDIR
21582 @defvar gdb.PYTHONDIR
21583 A string containing the python directory (@pxref{Python}).
21586 @findex gdb.execute
21587 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21588 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21589 If a GDB exception happens while @var{command} runs, it is
21590 translated as described in @ref{Exception Handling,,Exception Handling}.
21592 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21593 command as having originated from the user invoking it interactively.
21594 It must be a boolean value. If omitted, it defaults to @code{False}.
21596 By default, any output produced by @var{command} is sent to
21597 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21598 @code{True}, then output will be collected by @code{gdb.execute} and
21599 returned as a string. The default is @code{False}, in which case the
21600 return value is @code{None}. If @var{to_string} is @code{True}, the
21601 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21602 and height, and its pagination will be disabled; @pxref{Screen Size}.
21605 @findex gdb.breakpoints
21606 @defun gdb.breakpoints ()
21607 Return a sequence holding all of @value{GDBN}'s breakpoints.
21608 @xref{Breakpoints In Python}, for more information.
21611 @findex gdb.parameter
21612 @defun gdb.parameter (parameter)
21613 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21614 string naming the parameter to look up; @var{parameter} may contain
21615 spaces if the parameter has a multi-part name. For example,
21616 @samp{print object} is a valid parameter name.
21618 If the named parameter does not exist, this function throws a
21619 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21620 parameter's value is converted to a Python value of the appropriate
21621 type, and returned.
21624 @findex gdb.history
21625 @defun gdb.history (number)
21626 Return a value from @value{GDBN}'s value history (@pxref{Value
21627 History}). @var{number} indicates which history element to return.
21628 If @var{number} is negative, then @value{GDBN} will take its absolute value
21629 and count backward from the last element (i.e., the most recent element) to
21630 find the value to return. If @var{number} is zero, then @value{GDBN} will
21631 return the most recent element. If the element specified by @var{number}
21632 doesn't exist in the value history, a @code{gdb.error} exception will be
21635 If no exception is raised, the return value is always an instance of
21636 @code{gdb.Value} (@pxref{Values From Inferior}).
21639 @findex gdb.parse_and_eval
21640 @defun gdb.parse_and_eval (expression)
21641 Parse @var{expression} as an expression in the current language,
21642 evaluate it, and return the result as a @code{gdb.Value}.
21643 @var{expression} must be a string.
21645 This function can be useful when implementing a new command
21646 (@pxref{Commands In Python}), as it provides a way to parse the
21647 command's argument as an expression. It is also useful simply to
21648 compute values, for example, it is the only way to get the value of a
21649 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21652 @findex gdb.post_event
21653 @defun gdb.post_event (event)
21654 Put @var{event}, a callable object taking no arguments, into
21655 @value{GDBN}'s internal event queue. This callable will be invoked at
21656 some later point, during @value{GDBN}'s event processing. Events
21657 posted using @code{post_event} will be run in the order in which they
21658 were posted; however, there is no way to know when they will be
21659 processed relative to other events inside @value{GDBN}.
21661 @value{GDBN} is not thread-safe. If your Python program uses multiple
21662 threads, you must be careful to only call @value{GDBN}-specific
21663 functions in the main @value{GDBN} thread. @code{post_event} ensures
21667 (@value{GDBP}) python
21671 > def __init__(self, message):
21672 > self.message = message;
21673 > def __call__(self):
21674 > gdb.write(self.message)
21676 >class MyThread1 (threading.Thread):
21678 > gdb.post_event(Writer("Hello "))
21680 >class MyThread2 (threading.Thread):
21682 > gdb.post_event(Writer("World\n"))
21684 >MyThread1().start()
21685 >MyThread2().start()
21687 (@value{GDBP}) Hello World
21692 @defun gdb.write (string @r{[}, stream{]})
21693 Print a string to @value{GDBN}'s paginated output stream. The
21694 optional @var{stream} determines the stream to print to. The default
21695 stream is @value{GDBN}'s standard output stream. Possible stream
21702 @value{GDBN}'s standard output stream.
21707 @value{GDBN}'s standard error stream.
21712 @value{GDBN}'s log stream (@pxref{Logging Output}).
21715 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21716 call this function and will automatically direct the output to the
21721 @defun gdb.flush ()
21722 Flush the buffer of a @value{GDBN} paginated stream so that the
21723 contents are displayed immediately. @value{GDBN} will flush the
21724 contents of a stream automatically when it encounters a newline in the
21725 buffer. The optional @var{stream} determines the stream to flush. The
21726 default stream is @value{GDBN}'s standard output stream. Possible
21733 @value{GDBN}'s standard output stream.
21738 @value{GDBN}'s standard error stream.
21743 @value{GDBN}'s log stream (@pxref{Logging Output}).
21747 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21748 call this function for the relevant stream.
21751 @findex gdb.target_charset
21752 @defun gdb.target_charset ()
21753 Return the name of the current target character set (@pxref{Character
21754 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21755 that @samp{auto} is never returned.
21758 @findex gdb.target_wide_charset
21759 @defun gdb.target_wide_charset ()
21760 Return the name of the current target wide character set
21761 (@pxref{Character Sets}). This differs from
21762 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21766 @findex gdb.solib_name
21767 @defun gdb.solib_name (address)
21768 Return the name of the shared library holding the given @var{address}
21769 as a string, or @code{None}.
21772 @findex gdb.decode_line
21773 @defun gdb.decode_line @r{[}expression@r{]}
21774 Return locations of the line specified by @var{expression}, or of the
21775 current line if no argument was given. This function returns a Python
21776 tuple containing two elements. The first element contains a string
21777 holding any unparsed section of @var{expression} (or @code{None} if
21778 the expression has been fully parsed). The second element contains
21779 either @code{None} or another tuple that contains all the locations
21780 that match the expression represented as @code{gdb.Symtab_and_line}
21781 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21782 provided, it is decoded the way that @value{GDBN}'s inbuilt
21783 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21786 @defun gdb.prompt_hook (current_prompt)
21787 @anchor{prompt_hook}
21789 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21790 assigned to this operation before a prompt is displayed by
21793 The parameter @code{current_prompt} contains the current @value{GDBN}
21794 prompt. This method must return a Python string, or @code{None}. If
21795 a string is returned, the @value{GDBN} prompt will be set to that
21796 string. If @code{None} is returned, @value{GDBN} will continue to use
21797 the current prompt.
21799 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21800 such as those used by readline for command input, and annotation
21801 related prompts are prohibited from being changed.
21804 @node Exception Handling
21805 @subsubsection Exception Handling
21806 @cindex python exceptions
21807 @cindex exceptions, python
21809 When executing the @code{python} command, Python exceptions
21810 uncaught within the Python code are translated to calls to
21811 @value{GDBN} error-reporting mechanism. If the command that called
21812 @code{python} does not handle the error, @value{GDBN} will
21813 terminate it and print an error message containing the Python
21814 exception name, the associated value, and the Python call stack
21815 backtrace at the point where the exception was raised. Example:
21818 (@value{GDBP}) python print foo
21819 Traceback (most recent call last):
21820 File "<string>", line 1, in <module>
21821 NameError: name 'foo' is not defined
21824 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21825 Python code are converted to Python exceptions. The type of the
21826 Python exception depends on the error.
21830 This is the base class for most exceptions generated by @value{GDBN}.
21831 It is derived from @code{RuntimeError}, for compatibility with earlier
21832 versions of @value{GDBN}.
21834 If an error occurring in @value{GDBN} does not fit into some more
21835 specific category, then the generated exception will have this type.
21837 @item gdb.MemoryError
21838 This is a subclass of @code{gdb.error} which is thrown when an
21839 operation tried to access invalid memory in the inferior.
21841 @item KeyboardInterrupt
21842 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21843 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21846 In all cases, your exception handler will see the @value{GDBN} error
21847 message as its value and the Python call stack backtrace at the Python
21848 statement closest to where the @value{GDBN} error occured as the
21851 @findex gdb.GdbError
21852 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21853 it is useful to be able to throw an exception that doesn't cause a
21854 traceback to be printed. For example, the user may have invoked the
21855 command incorrectly. Use the @code{gdb.GdbError} exception
21856 to handle this case. Example:
21860 >class HelloWorld (gdb.Command):
21861 > """Greet the whole world."""
21862 > def __init__ (self):
21863 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21864 > def invoke (self, args, from_tty):
21865 > argv = gdb.string_to_argv (args)
21866 > if len (argv) != 0:
21867 > raise gdb.GdbError ("hello-world takes no arguments")
21868 > print "Hello, World!"
21871 (gdb) hello-world 42
21872 hello-world takes no arguments
21875 @node Values From Inferior
21876 @subsubsection Values From Inferior
21877 @cindex values from inferior, with Python
21878 @cindex python, working with values from inferior
21880 @cindex @code{gdb.Value}
21881 @value{GDBN} provides values it obtains from the inferior program in
21882 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21883 for its internal bookkeeping of the inferior's values, and for
21884 fetching values when necessary.
21886 Inferior values that are simple scalars can be used directly in
21887 Python expressions that are valid for the value's data type. Here's
21888 an example for an integer or floating-point value @code{some_val}:
21895 As result of this, @code{bar} will also be a @code{gdb.Value} object
21896 whose values are of the same type as those of @code{some_val}.
21898 Inferior values that are structures or instances of some class can
21899 be accessed using the Python @dfn{dictionary syntax}. For example, if
21900 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21901 can access its @code{foo} element with:
21904 bar = some_val['foo']
21907 Again, @code{bar} will also be a @code{gdb.Value} object.
21909 A @code{gdb.Value} that represents a function can be executed via
21910 inferior function call. Any arguments provided to the call must match
21911 the function's prototype, and must be provided in the order specified
21914 For example, @code{some_val} is a @code{gdb.Value} instance
21915 representing a function that takes two integers as arguments. To
21916 execute this function, call it like so:
21919 result = some_val (10,20)
21922 Any values returned from a function call will be stored as a
21925 The following attributes are provided:
21928 @defvar Value.address
21929 If this object is addressable, this read-only attribute holds a
21930 @code{gdb.Value} object representing the address. Otherwise,
21931 this attribute holds @code{None}.
21934 @cindex optimized out value in Python
21935 @defvar Value.is_optimized_out
21936 This read-only boolean attribute is true if the compiler optimized out
21937 this value, thus it is not available for fetching from the inferior.
21941 The type of this @code{gdb.Value}. The value of this attribute is a
21942 @code{gdb.Type} object (@pxref{Types In Python}).
21945 @defvar Value.dynamic_type
21946 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21947 type information (@acronym{RTTI}) to determine the dynamic type of the
21948 value. If this value is of class type, it will return the class in
21949 which the value is embedded, if any. If this value is of pointer or
21950 reference to a class type, it will compute the dynamic type of the
21951 referenced object, and return a pointer or reference to that type,
21952 respectively. In all other cases, it will return the value's static
21955 Note that this feature will only work when debugging a C@t{++} program
21956 that includes @acronym{RTTI} for the object in question. Otherwise,
21957 it will just return the static type of the value as in @kbd{ptype foo}
21958 (@pxref{Symbols, ptype}).
21961 @defvar Value.is_lazy
21962 The value of this read-only boolean attribute is @code{True} if this
21963 @code{gdb.Value} has not yet been fetched from the inferior.
21964 @value{GDBN} does not fetch values until necessary, for efficiency.
21968 myval = gdb.parse_and_eval ('somevar')
21971 The value of @code{somevar} is not fetched at this time. It will be
21972 fetched when the value is needed, or when the @code{fetch_lazy}
21977 The following methods are provided:
21980 @defun Value.__init__ (@var{val})
21981 Many Python values can be converted directly to a @code{gdb.Value} via
21982 this object initializer. Specifically:
21985 @item Python boolean
21986 A Python boolean is converted to the boolean type from the current
21989 @item Python integer
21990 A Python integer is converted to the C @code{long} type for the
21991 current architecture.
21994 A Python long is converted to the C @code{long long} type for the
21995 current architecture.
21998 A Python float is converted to the C @code{double} type for the
21999 current architecture.
22001 @item Python string
22002 A Python string is converted to a target string, using the current
22005 @item @code{gdb.Value}
22006 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22008 @item @code{gdb.LazyString}
22009 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22010 Python}), then the lazy string's @code{value} method is called, and
22011 its result is used.
22015 @defun Value.cast (type)
22016 Return a new instance of @code{gdb.Value} that is the result of
22017 casting this instance to the type described by @var{type}, which must
22018 be a @code{gdb.Type} object. If the cast cannot be performed for some
22019 reason, this method throws an exception.
22022 @defun Value.dereference ()
22023 For pointer data types, this method returns a new @code{gdb.Value} object
22024 whose contents is the object pointed to by the pointer. For example, if
22025 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22032 then you can use the corresponding @code{gdb.Value} to access what
22033 @code{foo} points to like this:
22036 bar = foo.dereference ()
22039 The result @code{bar} will be a @code{gdb.Value} object holding the
22040 value pointed to by @code{foo}.
22043 @defun Value.dynamic_cast (type)
22044 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22045 operator were used. Consult a C@t{++} reference for details.
22048 @defun Value.reinterpret_cast (type)
22049 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22050 operator were used. Consult a C@t{++} reference for details.
22053 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22054 If this @code{gdb.Value} represents a string, then this method
22055 converts the contents to a Python string. Otherwise, this method will
22056 throw an exception.
22058 Strings are recognized in a language-specific way; whether a given
22059 @code{gdb.Value} represents a string is determined by the current
22062 For C-like languages, a value is a string if it is a pointer to or an
22063 array of characters or ints. The string is assumed to be terminated
22064 by a zero of the appropriate width. However if the optional length
22065 argument is given, the string will be converted to that given length,
22066 ignoring any embedded zeros that the string may contain.
22068 If the optional @var{encoding} argument is given, it must be a string
22069 naming the encoding of the string in the @code{gdb.Value}, such as
22070 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22071 the same encodings as the corresponding argument to Python's
22072 @code{string.decode} method, and the Python codec machinery will be used
22073 to convert the string. If @var{encoding} is not given, or if
22074 @var{encoding} is the empty string, then either the @code{target-charset}
22075 (@pxref{Character Sets}) will be used, or a language-specific encoding
22076 will be used, if the current language is able to supply one.
22078 The optional @var{errors} argument is the same as the corresponding
22079 argument to Python's @code{string.decode} method.
22081 If the optional @var{length} argument is given, the string will be
22082 fetched and converted to the given length.
22085 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22086 If this @code{gdb.Value} represents a string, then this method
22087 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22088 In Python}). Otherwise, this method will throw an exception.
22090 If the optional @var{encoding} argument is given, it must be a string
22091 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22092 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22093 @var{encoding} argument is an encoding that @value{GDBN} does
22094 recognize, @value{GDBN} will raise an error.
22096 When a lazy string is printed, the @value{GDBN} encoding machinery is
22097 used to convert the string during printing. If the optional
22098 @var{encoding} argument is not provided, or is an empty string,
22099 @value{GDBN} will automatically select the encoding most suitable for
22100 the string type. For further information on encoding in @value{GDBN}
22101 please see @ref{Character Sets}.
22103 If the optional @var{length} argument is given, the string will be
22104 fetched and encoded to the length of characters specified. If
22105 the @var{length} argument is not provided, the string will be fetched
22106 and encoded until a null of appropriate width is found.
22109 @defun Value.fetch_lazy ()
22110 If the @code{gdb.Value} object is currently a lazy value
22111 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22112 fetched from the inferior. Any errors that occur in the process
22113 will produce a Python exception.
22115 If the @code{gdb.Value} object is not a lazy value, this method
22118 This method does not return a value.
22123 @node Types In Python
22124 @subsubsection Types In Python
22125 @cindex types in Python
22126 @cindex Python, working with types
22129 @value{GDBN} represents types from the inferior using the class
22132 The following type-related functions are available in the @code{gdb}
22135 @findex gdb.lookup_type
22136 @defun gdb.lookup_type (name @r{[}, block@r{]})
22137 This function looks up a type by name. @var{name} is the name of the
22138 type to look up. It must be a string.
22140 If @var{block} is given, then @var{name} is looked up in that scope.
22141 Otherwise, it is searched for globally.
22143 Ordinarily, this function will return an instance of @code{gdb.Type}.
22144 If the named type cannot be found, it will throw an exception.
22147 If the type is a structure or class type, or an enum type, the fields
22148 of that type can be accessed using the Python @dfn{dictionary syntax}.
22149 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22150 a structure type, you can access its @code{foo} field with:
22153 bar = some_type['foo']
22156 @code{bar} will be a @code{gdb.Field} object; see below under the
22157 description of the @code{Type.fields} method for a description of the
22158 @code{gdb.Field} class.
22160 An instance of @code{Type} has the following attributes:
22164 The type code for this type. The type code will be one of the
22165 @code{TYPE_CODE_} constants defined below.
22168 @defvar Type.sizeof
22169 The size of this type, in target @code{char} units. Usually, a
22170 target's @code{char} type will be an 8-bit byte. However, on some
22171 unusual platforms, this type may have a different size.
22175 The tag name for this type. The tag name is the name after
22176 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22177 languages have this concept. If this type has no tag name, then
22178 @code{None} is returned.
22182 The following methods are provided:
22185 @defun Type.fields ()
22186 For structure and union types, this method returns the fields. Range
22187 types have two fields, the minimum and maximum values. Enum types
22188 have one field per enum constant. Function and method types have one
22189 field per parameter. The base types of C@t{++} classes are also
22190 represented as fields. If the type has no fields, or does not fit
22191 into one of these categories, an empty sequence will be returned.
22193 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22196 This attribute is not available for @code{static} fields (as in
22197 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22198 position of the field. For @code{enum} fields, the value is the
22199 enumeration member's integer representation.
22202 The name of the field, or @code{None} for anonymous fields.
22205 This is @code{True} if the field is artificial, usually meaning that
22206 it was provided by the compiler and not the user. This attribute is
22207 always provided, and is @code{False} if the field is not artificial.
22209 @item is_base_class
22210 This is @code{True} if the field represents a base class of a C@t{++}
22211 structure. This attribute is always provided, and is @code{False}
22212 if the field is not a base class of the type that is the argument of
22213 @code{fields}, or if that type was not a C@t{++} class.
22216 If the field is packed, or is a bitfield, then this will have a
22217 non-zero value, which is the size of the field in bits. Otherwise,
22218 this will be zero; in this case the field's size is given by its type.
22221 The type of the field. This is usually an instance of @code{Type},
22222 but it can be @code{None} in some situations.
22226 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22227 Return a new @code{gdb.Type} object which represents an array of this
22228 type. If one argument is given, it is the inclusive upper bound of
22229 the array; in this case the lower bound is zero. If two arguments are
22230 given, the first argument is the lower bound of the array, and the
22231 second argument is the upper bound of the array. An array's length
22232 must not be negative, but the bounds can be.
22235 @defun Type.const ()
22236 Return a new @code{gdb.Type} object which represents a
22237 @code{const}-qualified variant of this type.
22240 @defun Type.volatile ()
22241 Return a new @code{gdb.Type} object which represents a
22242 @code{volatile}-qualified variant of this type.
22245 @defun Type.unqualified ()
22246 Return a new @code{gdb.Type} object which represents an unqualified
22247 variant of this type. That is, the result is neither @code{const} nor
22251 @defun Type.range ()
22252 Return a Python @code{Tuple} object that contains two elements: the
22253 low bound of the argument type and the high bound of that type. If
22254 the type does not have a range, @value{GDBN} will raise a
22255 @code{gdb.error} exception (@pxref{Exception Handling}).
22258 @defun Type.reference ()
22259 Return a new @code{gdb.Type} object which represents a reference to this
22263 @defun Type.pointer ()
22264 Return a new @code{gdb.Type} object which represents a pointer to this
22268 @defun Type.strip_typedefs ()
22269 Return a new @code{gdb.Type} that represents the real type,
22270 after removing all layers of typedefs.
22273 @defun Type.target ()
22274 Return a new @code{gdb.Type} object which represents the target type
22277 For a pointer type, the target type is the type of the pointed-to
22278 object. For an array type (meaning C-like arrays), the target type is
22279 the type of the elements of the array. For a function or method type,
22280 the target type is the type of the return value. For a complex type,
22281 the target type is the type of the elements. For a typedef, the
22282 target type is the aliased type.
22284 If the type does not have a target, this method will throw an
22288 @defun Type.template_argument (n @r{[}, block@r{]})
22289 If this @code{gdb.Type} is an instantiation of a template, this will
22290 return a new @code{gdb.Type} which represents the type of the
22291 @var{n}th template argument.
22293 If this @code{gdb.Type} is not a template type, this will throw an
22294 exception. Ordinarily, only C@t{++} code will have template types.
22296 If @var{block} is given, then @var{name} is looked up in that scope.
22297 Otherwise, it is searched for globally.
22302 Each type has a code, which indicates what category this type falls
22303 into. The available type categories are represented by constants
22304 defined in the @code{gdb} module:
22307 @findex TYPE_CODE_PTR
22308 @findex gdb.TYPE_CODE_PTR
22309 @item gdb.TYPE_CODE_PTR
22310 The type is a pointer.
22312 @findex TYPE_CODE_ARRAY
22313 @findex gdb.TYPE_CODE_ARRAY
22314 @item gdb.TYPE_CODE_ARRAY
22315 The type is an array.
22317 @findex TYPE_CODE_STRUCT
22318 @findex gdb.TYPE_CODE_STRUCT
22319 @item gdb.TYPE_CODE_STRUCT
22320 The type is a structure.
22322 @findex TYPE_CODE_UNION
22323 @findex gdb.TYPE_CODE_UNION
22324 @item gdb.TYPE_CODE_UNION
22325 The type is a union.
22327 @findex TYPE_CODE_ENUM
22328 @findex gdb.TYPE_CODE_ENUM
22329 @item gdb.TYPE_CODE_ENUM
22330 The type is an enum.
22332 @findex TYPE_CODE_FLAGS
22333 @findex gdb.TYPE_CODE_FLAGS
22334 @item gdb.TYPE_CODE_FLAGS
22335 A bit flags type, used for things such as status registers.
22337 @findex TYPE_CODE_FUNC
22338 @findex gdb.TYPE_CODE_FUNC
22339 @item gdb.TYPE_CODE_FUNC
22340 The type is a function.
22342 @findex TYPE_CODE_INT
22343 @findex gdb.TYPE_CODE_INT
22344 @item gdb.TYPE_CODE_INT
22345 The type is an integer type.
22347 @findex TYPE_CODE_FLT
22348 @findex gdb.TYPE_CODE_FLT
22349 @item gdb.TYPE_CODE_FLT
22350 A floating point type.
22352 @findex TYPE_CODE_VOID
22353 @findex gdb.TYPE_CODE_VOID
22354 @item gdb.TYPE_CODE_VOID
22355 The special type @code{void}.
22357 @findex TYPE_CODE_SET
22358 @findex gdb.TYPE_CODE_SET
22359 @item gdb.TYPE_CODE_SET
22362 @findex TYPE_CODE_RANGE
22363 @findex gdb.TYPE_CODE_RANGE
22364 @item gdb.TYPE_CODE_RANGE
22365 A range type, that is, an integer type with bounds.
22367 @findex TYPE_CODE_STRING
22368 @findex gdb.TYPE_CODE_STRING
22369 @item gdb.TYPE_CODE_STRING
22370 A string type. Note that this is only used for certain languages with
22371 language-defined string types; C strings are not represented this way.
22373 @findex TYPE_CODE_BITSTRING
22374 @findex gdb.TYPE_CODE_BITSTRING
22375 @item gdb.TYPE_CODE_BITSTRING
22378 @findex TYPE_CODE_ERROR
22379 @findex gdb.TYPE_CODE_ERROR
22380 @item gdb.TYPE_CODE_ERROR
22381 An unknown or erroneous type.
22383 @findex TYPE_CODE_METHOD
22384 @findex gdb.TYPE_CODE_METHOD
22385 @item gdb.TYPE_CODE_METHOD
22386 A method type, as found in C@t{++} or Java.
22388 @findex TYPE_CODE_METHODPTR
22389 @findex gdb.TYPE_CODE_METHODPTR
22390 @item gdb.TYPE_CODE_METHODPTR
22391 A pointer-to-member-function.
22393 @findex TYPE_CODE_MEMBERPTR
22394 @findex gdb.TYPE_CODE_MEMBERPTR
22395 @item gdb.TYPE_CODE_MEMBERPTR
22396 A pointer-to-member.
22398 @findex TYPE_CODE_REF
22399 @findex gdb.TYPE_CODE_REF
22400 @item gdb.TYPE_CODE_REF
22403 @findex TYPE_CODE_CHAR
22404 @findex gdb.TYPE_CODE_CHAR
22405 @item gdb.TYPE_CODE_CHAR
22408 @findex TYPE_CODE_BOOL
22409 @findex gdb.TYPE_CODE_BOOL
22410 @item gdb.TYPE_CODE_BOOL
22413 @findex TYPE_CODE_COMPLEX
22414 @findex gdb.TYPE_CODE_COMPLEX
22415 @item gdb.TYPE_CODE_COMPLEX
22416 A complex float type.
22418 @findex TYPE_CODE_TYPEDEF
22419 @findex gdb.TYPE_CODE_TYPEDEF
22420 @item gdb.TYPE_CODE_TYPEDEF
22421 A typedef to some other type.
22423 @findex TYPE_CODE_NAMESPACE
22424 @findex gdb.TYPE_CODE_NAMESPACE
22425 @item gdb.TYPE_CODE_NAMESPACE
22426 A C@t{++} namespace.
22428 @findex TYPE_CODE_DECFLOAT
22429 @findex gdb.TYPE_CODE_DECFLOAT
22430 @item gdb.TYPE_CODE_DECFLOAT
22431 A decimal floating point type.
22433 @findex TYPE_CODE_INTERNAL_FUNCTION
22434 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22435 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22436 A function internal to @value{GDBN}. This is the type used to represent
22437 convenience functions.
22440 Further support for types is provided in the @code{gdb.types}
22441 Python module (@pxref{gdb.types}).
22443 @node Pretty Printing API
22444 @subsubsection Pretty Printing API
22446 An example output is provided (@pxref{Pretty Printing}).
22448 A pretty-printer is just an object that holds a value and implements a
22449 specific interface, defined here.
22451 @defun pretty_printer.children (self)
22452 @value{GDBN} will call this method on a pretty-printer to compute the
22453 children of the pretty-printer's value.
22455 This method must return an object conforming to the Python iterator
22456 protocol. Each item returned by the iterator must be a tuple holding
22457 two elements. The first element is the ``name'' of the child; the
22458 second element is the child's value. The value can be any Python
22459 object which is convertible to a @value{GDBN} value.
22461 This method is optional. If it does not exist, @value{GDBN} will act
22462 as though the value has no children.
22465 @defun pretty_printer.display_hint (self)
22466 The CLI may call this method and use its result to change the
22467 formatting of a value. The result will also be supplied to an MI
22468 consumer as a @samp{displayhint} attribute of the variable being
22471 This method is optional. If it does exist, this method must return a
22474 Some display hints are predefined by @value{GDBN}:
22478 Indicate that the object being printed is ``array-like''. The CLI
22479 uses this to respect parameters such as @code{set print elements} and
22480 @code{set print array}.
22483 Indicate that the object being printed is ``map-like'', and that the
22484 children of this value can be assumed to alternate between keys and
22488 Indicate that the object being printed is ``string-like''. If the
22489 printer's @code{to_string} method returns a Python string of some
22490 kind, then @value{GDBN} will call its internal language-specific
22491 string-printing function to format the string. For the CLI this means
22492 adding quotation marks, possibly escaping some characters, respecting
22493 @code{set print elements}, and the like.
22497 @defun pretty_printer.to_string (self)
22498 @value{GDBN} will call this method to display the string
22499 representation of the value passed to the object's constructor.
22501 When printing from the CLI, if the @code{to_string} method exists,
22502 then @value{GDBN} will prepend its result to the values returned by
22503 @code{children}. Exactly how this formatting is done is dependent on
22504 the display hint, and may change as more hints are added. Also,
22505 depending on the print settings (@pxref{Print Settings}), the CLI may
22506 print just the result of @code{to_string} in a stack trace, omitting
22507 the result of @code{children}.
22509 If this method returns a string, it is printed verbatim.
22511 Otherwise, if this method returns an instance of @code{gdb.Value},
22512 then @value{GDBN} prints this value. This may result in a call to
22513 another pretty-printer.
22515 If instead the method returns a Python value which is convertible to a
22516 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22517 the resulting value. Again, this may result in a call to another
22518 pretty-printer. Python scalars (integers, floats, and booleans) and
22519 strings are convertible to @code{gdb.Value}; other types are not.
22521 Finally, if this method returns @code{None} then no further operations
22522 are peformed in this method and nothing is printed.
22524 If the result is not one of these types, an exception is raised.
22527 @value{GDBN} provides a function which can be used to look up the
22528 default pretty-printer for a @code{gdb.Value}:
22530 @findex gdb.default_visualizer
22531 @defun gdb.default_visualizer (value)
22532 This function takes a @code{gdb.Value} object as an argument. If a
22533 pretty-printer for this value exists, then it is returned. If no such
22534 printer exists, then this returns @code{None}.
22537 @node Selecting Pretty-Printers
22538 @subsubsection Selecting Pretty-Printers
22540 The Python list @code{gdb.pretty_printers} contains an array of
22541 functions or callable objects that have been registered via addition
22542 as a pretty-printer. Printers in this list are called @code{global}
22543 printers, they're available when debugging all inferiors.
22544 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22545 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22548 Each function on these lists is passed a single @code{gdb.Value}
22549 argument and should return a pretty-printer object conforming to the
22550 interface definition above (@pxref{Pretty Printing API}). If a function
22551 cannot create a pretty-printer for the value, it should return
22554 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22555 @code{gdb.Objfile} in the current program space and iteratively calls
22556 each enabled lookup routine in the list for that @code{gdb.Objfile}
22557 until it receives a pretty-printer object.
22558 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22559 searches the pretty-printer list of the current program space,
22560 calling each enabled function until an object is returned.
22561 After these lists have been exhausted, it tries the global
22562 @code{gdb.pretty_printers} list, again calling each enabled function until an
22563 object is returned.
22565 The order in which the objfiles are searched is not specified. For a
22566 given list, functions are always invoked from the head of the list,
22567 and iterated over sequentially until the end of the list, or a printer
22568 object is returned.
22570 For various reasons a pretty-printer may not work.
22571 For example, the underlying data structure may have changed and
22572 the pretty-printer is out of date.
22574 The consequences of a broken pretty-printer are severe enough that
22575 @value{GDBN} provides support for enabling and disabling individual
22576 printers. For example, if @code{print frame-arguments} is on,
22577 a backtrace can become highly illegible if any argument is printed
22578 with a broken printer.
22580 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22581 attribute to the registered function or callable object. If this attribute
22582 is present and its value is @code{False}, the printer is disabled, otherwise
22583 the printer is enabled.
22585 @node Writing a Pretty-Printer
22586 @subsubsection Writing a Pretty-Printer
22587 @cindex writing a pretty-printer
22589 A pretty-printer consists of two parts: a lookup function to detect
22590 if the type is supported, and the printer itself.
22592 Here is an example showing how a @code{std::string} printer might be
22593 written. @xref{Pretty Printing API}, for details on the API this class
22597 class StdStringPrinter(object):
22598 "Print a std::string"
22600 def __init__(self, val):
22603 def to_string(self):
22604 return self.val['_M_dataplus']['_M_p']
22606 def display_hint(self):
22610 And here is an example showing how a lookup function for the printer
22611 example above might be written.
22614 def str_lookup_function(val):
22615 lookup_tag = val.type.tag
22616 if lookup_tag == None:
22618 regex = re.compile("^std::basic_string<char,.*>$")
22619 if regex.match(lookup_tag):
22620 return StdStringPrinter(val)
22624 The example lookup function extracts the value's type, and attempts to
22625 match it to a type that it can pretty-print. If it is a type the
22626 printer can pretty-print, it will return a printer object. If not, it
22627 returns @code{None}.
22629 We recommend that you put your core pretty-printers into a Python
22630 package. If your pretty-printers are for use with a library, we
22631 further recommend embedding a version number into the package name.
22632 This practice will enable @value{GDBN} to load multiple versions of
22633 your pretty-printers at the same time, because they will have
22636 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22637 can be evaluated multiple times without changing its meaning. An
22638 ideal auto-load file will consist solely of @code{import}s of your
22639 printer modules, followed by a call to a register pretty-printers with
22640 the current objfile.
22642 Taken as a whole, this approach will scale nicely to multiple
22643 inferiors, each potentially using a different library version.
22644 Embedding a version number in the Python package name will ensure that
22645 @value{GDBN} is able to load both sets of printers simultaneously.
22646 Then, because the search for pretty-printers is done by objfile, and
22647 because your auto-loaded code took care to register your library's
22648 printers with a specific objfile, @value{GDBN} will find the correct
22649 printers for the specific version of the library used by each
22652 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22653 this code might appear in @code{gdb.libstdcxx.v6}:
22656 def register_printers(objfile):
22657 objfile.pretty_printers.append(str_lookup_function)
22661 And then the corresponding contents of the auto-load file would be:
22664 import gdb.libstdcxx.v6
22665 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22668 The previous example illustrates a basic pretty-printer.
22669 There are a few things that can be improved on.
22670 The printer doesn't have a name, making it hard to identify in a
22671 list of installed printers. The lookup function has a name, but
22672 lookup functions can have arbitrary, even identical, names.
22674 Second, the printer only handles one type, whereas a library typically has
22675 several types. One could install a lookup function for each desired type
22676 in the library, but one could also have a single lookup function recognize
22677 several types. The latter is the conventional way this is handled.
22678 If a pretty-printer can handle multiple data types, then its
22679 @dfn{subprinters} are the printers for the individual data types.
22681 The @code{gdb.printing} module provides a formal way of solving these
22682 problems (@pxref{gdb.printing}).
22683 Here is another example that handles multiple types.
22685 These are the types we are going to pretty-print:
22688 struct foo @{ int a, b; @};
22689 struct bar @{ struct foo x, y; @};
22692 Here are the printers:
22696 """Print a foo object."""
22698 def __init__(self, val):
22701 def to_string(self):
22702 return ("a=<" + str(self.val["a"]) +
22703 "> b=<" + str(self.val["b"]) + ">")
22706 """Print a bar object."""
22708 def __init__(self, val):
22711 def to_string(self):
22712 return ("x=<" + str(self.val["x"]) +
22713 "> y=<" + str(self.val["y"]) + ">")
22716 This example doesn't need a lookup function, that is handled by the
22717 @code{gdb.printing} module. Instead a function is provided to build up
22718 the object that handles the lookup.
22721 import gdb.printing
22723 def build_pretty_printer():
22724 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22726 pp.add_printer('foo', '^foo$', fooPrinter)
22727 pp.add_printer('bar', '^bar$', barPrinter)
22731 And here is the autoload support:
22734 import gdb.printing
22736 gdb.printing.register_pretty_printer(
22737 gdb.current_objfile(),
22738 my_library.build_pretty_printer())
22741 Finally, when this printer is loaded into @value{GDBN}, here is the
22742 corresponding output of @samp{info pretty-printer}:
22745 (gdb) info pretty-printer
22752 @node Inferiors In Python
22753 @subsubsection Inferiors In Python
22754 @cindex inferiors in Python
22756 @findex gdb.Inferior
22757 Programs which are being run under @value{GDBN} are called inferiors
22758 (@pxref{Inferiors and Programs}). Python scripts can access
22759 information about and manipulate inferiors controlled by @value{GDBN}
22760 via objects of the @code{gdb.Inferior} class.
22762 The following inferior-related functions are available in the @code{gdb}
22765 @defun gdb.inferiors ()
22766 Return a tuple containing all inferior objects.
22769 @defun gdb.selected_inferior ()
22770 Return an object representing the current inferior.
22773 A @code{gdb.Inferior} object has the following attributes:
22776 @defvar Inferior.num
22777 ID of inferior, as assigned by GDB.
22780 @defvar Inferior.pid
22781 Process ID of the inferior, as assigned by the underlying operating
22785 @defvar Inferior.was_attached
22786 Boolean signaling whether the inferior was created using `attach', or
22787 started by @value{GDBN} itself.
22791 A @code{gdb.Inferior} object has the following methods:
22794 @defun Inferior.is_valid ()
22795 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22796 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22797 if the inferior no longer exists within @value{GDBN}. All other
22798 @code{gdb.Inferior} methods will throw an exception if it is invalid
22799 at the time the method is called.
22802 @defun Inferior.threads ()
22803 This method returns a tuple holding all the threads which are valid
22804 when it is called. If there are no valid threads, the method will
22805 return an empty tuple.
22808 @findex gdb.read_memory
22809 @defun Inferior.read_memory (address, length)
22810 Read @var{length} bytes of memory from the inferior, starting at
22811 @var{address}. Returns a buffer object, which behaves much like an array
22812 or a string. It can be modified and given to the @code{gdb.write_memory}
22816 @findex gdb.write_memory
22817 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22818 Write the contents of @var{buffer} to the inferior, starting at
22819 @var{address}. The @var{buffer} parameter must be a Python object
22820 which supports the buffer protocol, i.e., a string, an array or the
22821 object returned from @code{gdb.read_memory}. If given, @var{length}
22822 determines the number of bytes from @var{buffer} to be written.
22825 @findex gdb.search_memory
22826 @defun Inferior.search_memory (address, length, pattern)
22827 Search a region of the inferior memory starting at @var{address} with
22828 the given @var{length} using the search pattern supplied in
22829 @var{pattern}. The @var{pattern} parameter must be a Python object
22830 which supports the buffer protocol, i.e., a string, an array or the
22831 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22832 containing the address where the pattern was found, or @code{None} if
22833 the pattern could not be found.
22837 @node Events In Python
22838 @subsubsection Events In Python
22839 @cindex inferior events in Python
22841 @value{GDBN} provides a general event facility so that Python code can be
22842 notified of various state changes, particularly changes that occur in
22845 An @dfn{event} is just an object that describes some state change. The
22846 type of the object and its attributes will vary depending on the details
22847 of the change. All the existing events are described below.
22849 In order to be notified of an event, you must register an event handler
22850 with an @dfn{event registry}. An event registry is an object in the
22851 @code{gdb.events} module which dispatches particular events. A registry
22852 provides methods to register and unregister event handlers:
22855 @defun EventRegistry.connect (object)
22856 Add the given callable @var{object} to the registry. This object will be
22857 called when an event corresponding to this registry occurs.
22860 @defun EventRegistry.disconnect (object)
22861 Remove the given @var{object} from the registry. Once removed, the object
22862 will no longer receive notifications of events.
22866 Here is an example:
22869 def exit_handler (event):
22870 print "event type: exit"
22871 print "exit code: %d" % (event.exit_code)
22873 gdb.events.exited.connect (exit_handler)
22876 In the above example we connect our handler @code{exit_handler} to the
22877 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22878 called when the inferior exits. The argument @dfn{event} in this example is
22879 of type @code{gdb.ExitedEvent}. As you can see in the example the
22880 @code{ExitedEvent} object has an attribute which indicates the exit code of
22883 The following is a listing of the event registries that are available and
22884 details of the events they emit:
22889 Emits @code{gdb.ThreadEvent}.
22891 Some events can be thread specific when @value{GDBN} is running in non-stop
22892 mode. When represented in Python, these events all extend
22893 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22894 events which are emitted by this or other modules might extend this event.
22895 Examples of these events are @code{gdb.BreakpointEvent} and
22896 @code{gdb.ContinueEvent}.
22899 @defvar ThreadEvent.inferior_thread
22900 In non-stop mode this attribute will be set to the specific thread which was
22901 involved in the emitted event. Otherwise, it will be set to @code{None}.
22905 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22907 This event indicates that the inferior has been continued after a stop. For
22908 inherited attribute refer to @code{gdb.ThreadEvent} above.
22910 @item events.exited
22911 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22912 @code{events.ExitedEvent} has two attributes:
22914 @defvar ExitedEvent.exit_code
22915 An integer representing the exit code, if available, which the inferior
22916 has returned. (The exit code could be unavailable if, for example,
22917 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22918 the attribute does not exist.
22920 @defvar ExitedEvent inferior
22921 A reference to the inferior which triggered the @code{exited} event.
22926 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22928 Indicates that the inferior has stopped. All events emitted by this registry
22929 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22930 will indicate the stopped thread when @value{GDBN} is running in non-stop
22931 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22933 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22935 This event indicates that the inferior or one of its threads has received as
22936 signal. @code{gdb.SignalEvent} has the following attributes:
22939 @defvar SignalEvent.stop_signal
22940 A string representing the signal received by the inferior. A list of possible
22941 signal values can be obtained by running the command @code{info signals} in
22942 the @value{GDBN} command prompt.
22946 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22948 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22949 been hit, and has the following attributes:
22952 @defvar BreakpointEvent.breakpoints
22953 A sequence containing references to all the breakpoints (type
22954 @code{gdb.Breakpoint}) that were hit.
22955 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22957 @defvar BreakpointEvent.breakpoint
22958 A reference to the first breakpoint that was hit.
22959 This function is maintained for backward compatibility and is now deprecated
22960 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22964 @item events.new_objfile
22965 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22966 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22969 @defvar NewObjFileEvent.new_objfile
22970 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22971 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22977 @node Threads In Python
22978 @subsubsection Threads In Python
22979 @cindex threads in python
22981 @findex gdb.InferiorThread
22982 Python scripts can access information about, and manipulate inferior threads
22983 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22985 The following thread-related functions are available in the @code{gdb}
22988 @findex gdb.selected_thread
22989 @defun gdb.selected_thread ()
22990 This function returns the thread object for the selected thread. If there
22991 is no selected thread, this will return @code{None}.
22994 A @code{gdb.InferiorThread} object has the following attributes:
22997 @defvar InferiorThread.name
22998 The name of the thread. If the user specified a name using
22999 @code{thread name}, then this returns that name. Otherwise, if an
23000 OS-supplied name is available, then it is returned. Otherwise, this
23001 returns @code{None}.
23003 This attribute can be assigned to. The new value must be a string
23004 object, which sets the new name, or @code{None}, which removes any
23005 user-specified thread name.
23008 @defvar InferiorThread.num
23009 ID of the thread, as assigned by GDB.
23012 @defvar InferiorThread.ptid
23013 ID of the thread, as assigned by the operating system. This attribute is a
23014 tuple containing three integers. The first is the Process ID (PID); the second
23015 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23016 Either the LWPID or TID may be 0, which indicates that the operating system
23017 does not use that identifier.
23021 A @code{gdb.InferiorThread} object has the following methods:
23024 @defun InferiorThread.is_valid ()
23025 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23026 @code{False} if not. A @code{gdb.InferiorThread} object will become
23027 invalid if the thread exits, or the inferior that the thread belongs
23028 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23029 exception if it is invalid at the time the method is called.
23032 @defun InferiorThread.switch ()
23033 This changes @value{GDBN}'s currently selected thread to the one represented
23037 @defun InferiorThread.is_stopped ()
23038 Return a Boolean indicating whether the thread is stopped.
23041 @defun InferiorThread.is_running ()
23042 Return a Boolean indicating whether the thread is running.
23045 @defun InferiorThread.is_exited ()
23046 Return a Boolean indicating whether the thread is exited.
23050 @node Commands In Python
23051 @subsubsection Commands In Python
23053 @cindex commands in python
23054 @cindex python commands
23055 You can implement new @value{GDBN} CLI commands in Python. A CLI
23056 command is implemented using an instance of the @code{gdb.Command}
23057 class, most commonly using a subclass.
23059 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23060 The object initializer for @code{Command} registers the new command
23061 with @value{GDBN}. This initializer is normally invoked from the
23062 subclass' own @code{__init__} method.
23064 @var{name} is the name of the command. If @var{name} consists of
23065 multiple words, then the initial words are looked for as prefix
23066 commands. In this case, if one of the prefix commands does not exist,
23067 an exception is raised.
23069 There is no support for multi-line commands.
23071 @var{command_class} should be one of the @samp{COMMAND_} constants
23072 defined below. This argument tells @value{GDBN} how to categorize the
23073 new command in the help system.
23075 @var{completer_class} is an optional argument. If given, it should be
23076 one of the @samp{COMPLETE_} constants defined below. This argument
23077 tells @value{GDBN} how to perform completion for this command. If not
23078 given, @value{GDBN} will attempt to complete using the object's
23079 @code{complete} method (see below); if no such method is found, an
23080 error will occur when completion is attempted.
23082 @var{prefix} is an optional argument. If @code{True}, then the new
23083 command is a prefix command; sub-commands of this command may be
23086 The help text for the new command is taken from the Python
23087 documentation string for the command's class, if there is one. If no
23088 documentation string is provided, the default value ``This command is
23089 not documented.'' is used.
23092 @cindex don't repeat Python command
23093 @defun Command.dont_repeat ()
23094 By default, a @value{GDBN} command is repeated when the user enters a
23095 blank line at the command prompt. A command can suppress this
23096 behavior by invoking the @code{dont_repeat} method. This is similar
23097 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23100 @defun Command.invoke (argument, from_tty)
23101 This method is called by @value{GDBN} when this command is invoked.
23103 @var{argument} is a string. It is the argument to the command, after
23104 leading and trailing whitespace has been stripped.
23106 @var{from_tty} is a boolean argument. When true, this means that the
23107 command was entered by the user at the terminal; when false it means
23108 that the command came from elsewhere.
23110 If this method throws an exception, it is turned into a @value{GDBN}
23111 @code{error} call. Otherwise, the return value is ignored.
23113 @findex gdb.string_to_argv
23114 To break @var{argument} up into an argv-like string use
23115 @code{gdb.string_to_argv}. This function behaves identically to
23116 @value{GDBN}'s internal argument lexer @code{buildargv}.
23117 It is recommended to use this for consistency.
23118 Arguments are separated by spaces and may be quoted.
23122 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23123 ['1', '2 "3', '4 "5', "6 '7"]
23128 @cindex completion of Python commands
23129 @defun Command.complete (text, word)
23130 This method is called by @value{GDBN} when the user attempts
23131 completion on this command. All forms of completion are handled by
23132 this method, that is, the @key{TAB} and @key{M-?} key bindings
23133 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23136 The arguments @var{text} and @var{word} are both strings. @var{text}
23137 holds the complete command line up to the cursor's location.
23138 @var{word} holds the last word of the command line; this is computed
23139 using a word-breaking heuristic.
23141 The @code{complete} method can return several values:
23144 If the return value is a sequence, the contents of the sequence are
23145 used as the completions. It is up to @code{complete} to ensure that the
23146 contents actually do complete the word. A zero-length sequence is
23147 allowed, it means that there were no completions available. Only
23148 string elements of the sequence are used; other elements in the
23149 sequence are ignored.
23152 If the return value is one of the @samp{COMPLETE_} constants defined
23153 below, then the corresponding @value{GDBN}-internal completion
23154 function is invoked, and its result is used.
23157 All other results are treated as though there were no available
23162 When a new command is registered, it must be declared as a member of
23163 some general class of commands. This is used to classify top-level
23164 commands in the on-line help system; note that prefix commands are not
23165 listed under their own category but rather that of their top-level
23166 command. The available classifications are represented by constants
23167 defined in the @code{gdb} module:
23170 @findex COMMAND_NONE
23171 @findex gdb.COMMAND_NONE
23172 @item gdb.COMMAND_NONE
23173 The command does not belong to any particular class. A command in
23174 this category will not be displayed in any of the help categories.
23176 @findex COMMAND_RUNNING
23177 @findex gdb.COMMAND_RUNNING
23178 @item gdb.COMMAND_RUNNING
23179 The command is related to running the inferior. For example,
23180 @code{start}, @code{step}, and @code{continue} are in this category.
23181 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23182 commands in this category.
23184 @findex COMMAND_DATA
23185 @findex gdb.COMMAND_DATA
23186 @item gdb.COMMAND_DATA
23187 The command is related to data or variables. For example,
23188 @code{call}, @code{find}, and @code{print} are in this category. Type
23189 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23192 @findex COMMAND_STACK
23193 @findex gdb.COMMAND_STACK
23194 @item gdb.COMMAND_STACK
23195 The command has to do with manipulation of the stack. For example,
23196 @code{backtrace}, @code{frame}, and @code{return} are in this
23197 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23198 list of commands in this category.
23200 @findex COMMAND_FILES
23201 @findex gdb.COMMAND_FILES
23202 @item gdb.COMMAND_FILES
23203 This class is used for file-related commands. For example,
23204 @code{file}, @code{list} and @code{section} are in this category.
23205 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23206 commands in this category.
23208 @findex COMMAND_SUPPORT
23209 @findex gdb.COMMAND_SUPPORT
23210 @item gdb.COMMAND_SUPPORT
23211 This should be used for ``support facilities'', generally meaning
23212 things that are useful to the user when interacting with @value{GDBN},
23213 but not related to the state of the inferior. For example,
23214 @code{help}, @code{make}, and @code{shell} are in this category. Type
23215 @kbd{help support} at the @value{GDBN} prompt to see a list of
23216 commands in this category.
23218 @findex COMMAND_STATUS
23219 @findex gdb.COMMAND_STATUS
23220 @item gdb.COMMAND_STATUS
23221 The command is an @samp{info}-related command, that is, related to the
23222 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23223 and @code{show} are in this category. Type @kbd{help status} at the
23224 @value{GDBN} prompt to see a list of commands in this category.
23226 @findex COMMAND_BREAKPOINTS
23227 @findex gdb.COMMAND_BREAKPOINTS
23228 @item gdb.COMMAND_BREAKPOINTS
23229 The command has to do with breakpoints. For example, @code{break},
23230 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23231 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23234 @findex COMMAND_TRACEPOINTS
23235 @findex gdb.COMMAND_TRACEPOINTS
23236 @item gdb.COMMAND_TRACEPOINTS
23237 The command has to do with tracepoints. For example, @code{trace},
23238 @code{actions}, and @code{tfind} are in this category. Type
23239 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23240 commands in this category.
23242 @findex COMMAND_OBSCURE
23243 @findex gdb.COMMAND_OBSCURE
23244 @item gdb.COMMAND_OBSCURE
23245 The command is only used in unusual circumstances, or is not of
23246 general interest to users. For example, @code{checkpoint},
23247 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23248 obscure} at the @value{GDBN} prompt to see a list of commands in this
23251 @findex COMMAND_MAINTENANCE
23252 @findex gdb.COMMAND_MAINTENANCE
23253 @item gdb.COMMAND_MAINTENANCE
23254 The command is only useful to @value{GDBN} maintainers. The
23255 @code{maintenance} and @code{flushregs} commands are in this category.
23256 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23257 commands in this category.
23260 A new command can use a predefined completion function, either by
23261 specifying it via an argument at initialization, or by returning it
23262 from the @code{complete} method. These predefined completion
23263 constants are all defined in the @code{gdb} module:
23266 @findex COMPLETE_NONE
23267 @findex gdb.COMPLETE_NONE
23268 @item gdb.COMPLETE_NONE
23269 This constant means that no completion should be done.
23271 @findex COMPLETE_FILENAME
23272 @findex gdb.COMPLETE_FILENAME
23273 @item gdb.COMPLETE_FILENAME
23274 This constant means that filename completion should be performed.
23276 @findex COMPLETE_LOCATION
23277 @findex gdb.COMPLETE_LOCATION
23278 @item gdb.COMPLETE_LOCATION
23279 This constant means that location completion should be done.
23280 @xref{Specify Location}.
23282 @findex COMPLETE_COMMAND
23283 @findex gdb.COMPLETE_COMMAND
23284 @item gdb.COMPLETE_COMMAND
23285 This constant means that completion should examine @value{GDBN}
23288 @findex COMPLETE_SYMBOL
23289 @findex gdb.COMPLETE_SYMBOL
23290 @item gdb.COMPLETE_SYMBOL
23291 This constant means that completion should be done using symbol names
23295 The following code snippet shows how a trivial CLI command can be
23296 implemented in Python:
23299 class HelloWorld (gdb.Command):
23300 """Greet the whole world."""
23302 def __init__ (self):
23303 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23305 def invoke (self, arg, from_tty):
23306 print "Hello, World!"
23311 The last line instantiates the class, and is necessary to trigger the
23312 registration of the command with @value{GDBN}. Depending on how the
23313 Python code is read into @value{GDBN}, you may need to import the
23314 @code{gdb} module explicitly.
23316 @node Parameters In Python
23317 @subsubsection Parameters In Python
23319 @cindex parameters in python
23320 @cindex python parameters
23321 @tindex gdb.Parameter
23323 You can implement new @value{GDBN} parameters using Python. A new
23324 parameter is implemented as an instance of the @code{gdb.Parameter}
23327 Parameters are exposed to the user via the @code{set} and
23328 @code{show} commands. @xref{Help}.
23330 There are many parameters that already exist and can be set in
23331 @value{GDBN}. Two examples are: @code{set follow fork} and
23332 @code{set charset}. Setting these parameters influences certain
23333 behavior in @value{GDBN}. Similarly, you can define parameters that
23334 can be used to influence behavior in custom Python scripts and commands.
23336 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23337 The object initializer for @code{Parameter} registers the new
23338 parameter with @value{GDBN}. This initializer is normally invoked
23339 from the subclass' own @code{__init__} method.
23341 @var{name} is the name of the new parameter. If @var{name} consists
23342 of multiple words, then the initial words are looked for as prefix
23343 parameters. An example of this can be illustrated with the
23344 @code{set print} set of parameters. If @var{name} is
23345 @code{print foo}, then @code{print} will be searched as the prefix
23346 parameter. In this case the parameter can subsequently be accessed in
23347 @value{GDBN} as @code{set print foo}.
23349 If @var{name} consists of multiple words, and no prefix parameter group
23350 can be found, an exception is raised.
23352 @var{command-class} should be one of the @samp{COMMAND_} constants
23353 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23354 categorize the new parameter in the help system.
23356 @var{parameter-class} should be one of the @samp{PARAM_} constants
23357 defined below. This argument tells @value{GDBN} the type of the new
23358 parameter; this information is used for input validation and
23361 If @var{parameter-class} is @code{PARAM_ENUM}, then
23362 @var{enum-sequence} must be a sequence of strings. These strings
23363 represent the possible values for the parameter.
23365 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23366 of a fourth argument will cause an exception to be thrown.
23368 The help text for the new parameter is taken from the Python
23369 documentation string for the parameter's class, if there is one. If
23370 there is no documentation string, a default value is used.
23373 @defvar Parameter.set_doc
23374 If this attribute exists, and is a string, then its value is used as
23375 the help text for this parameter's @code{set} command. The value is
23376 examined when @code{Parameter.__init__} is invoked; subsequent changes
23380 @defvar Parameter.show_doc
23381 If this attribute exists, and is a string, then its value is used as
23382 the help text for this parameter's @code{show} command. The value is
23383 examined when @code{Parameter.__init__} is invoked; subsequent changes
23387 @defvar Parameter.value
23388 The @code{value} attribute holds the underlying value of the
23389 parameter. It can be read and assigned to just as any other
23390 attribute. @value{GDBN} does validation when assignments are made.
23393 There are two methods that should be implemented in any
23394 @code{Parameter} class. These are:
23396 @defun Parameter.get_set_string (self)
23397 @value{GDBN} will call this method when a @var{parameter}'s value has
23398 been changed via the @code{set} API (for example, @kbd{set foo off}).
23399 The @code{value} attribute has already been populated with the new
23400 value and may be used in output. This method must return a string.
23403 @defun Parameter.get_show_string (self, svalue)
23404 @value{GDBN} will call this method when a @var{parameter}'s
23405 @code{show} API has been invoked (for example, @kbd{show foo}). The
23406 argument @code{svalue} receives the string representation of the
23407 current value. This method must return a string.
23410 When a new parameter is defined, its type must be specified. The
23411 available types are represented by constants defined in the @code{gdb}
23415 @findex PARAM_BOOLEAN
23416 @findex gdb.PARAM_BOOLEAN
23417 @item gdb.PARAM_BOOLEAN
23418 The value is a plain boolean. The Python boolean values, @code{True}
23419 and @code{False} are the only valid values.
23421 @findex PARAM_AUTO_BOOLEAN
23422 @findex gdb.PARAM_AUTO_BOOLEAN
23423 @item gdb.PARAM_AUTO_BOOLEAN
23424 The value has three possible states: true, false, and @samp{auto}. In
23425 Python, true and false are represented using boolean constants, and
23426 @samp{auto} is represented using @code{None}.
23428 @findex PARAM_UINTEGER
23429 @findex gdb.PARAM_UINTEGER
23430 @item gdb.PARAM_UINTEGER
23431 The value is an unsigned integer. The value of 0 should be
23432 interpreted to mean ``unlimited''.
23434 @findex PARAM_INTEGER
23435 @findex gdb.PARAM_INTEGER
23436 @item gdb.PARAM_INTEGER
23437 The value is a signed integer. The value of 0 should be interpreted
23438 to mean ``unlimited''.
23440 @findex PARAM_STRING
23441 @findex gdb.PARAM_STRING
23442 @item gdb.PARAM_STRING
23443 The value is a string. When the user modifies the string, any escape
23444 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23445 translated into corresponding characters and encoded into the current
23448 @findex PARAM_STRING_NOESCAPE
23449 @findex gdb.PARAM_STRING_NOESCAPE
23450 @item gdb.PARAM_STRING_NOESCAPE
23451 The value is a string. When the user modifies the string, escapes are
23452 passed through untranslated.
23454 @findex PARAM_OPTIONAL_FILENAME
23455 @findex gdb.PARAM_OPTIONAL_FILENAME
23456 @item gdb.PARAM_OPTIONAL_FILENAME
23457 The value is a either a filename (a string), or @code{None}.
23459 @findex PARAM_FILENAME
23460 @findex gdb.PARAM_FILENAME
23461 @item gdb.PARAM_FILENAME
23462 The value is a filename. This is just like
23463 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23465 @findex PARAM_ZINTEGER
23466 @findex gdb.PARAM_ZINTEGER
23467 @item gdb.PARAM_ZINTEGER
23468 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23469 is interpreted as itself.
23472 @findex gdb.PARAM_ENUM
23473 @item gdb.PARAM_ENUM
23474 The value is a string, which must be one of a collection string
23475 constants provided when the parameter is created.
23478 @node Functions In Python
23479 @subsubsection Writing new convenience functions
23481 @cindex writing convenience functions
23482 @cindex convenience functions in python
23483 @cindex python convenience functions
23484 @tindex gdb.Function
23486 You can implement new convenience functions (@pxref{Convenience Vars})
23487 in Python. A convenience function is an instance of a subclass of the
23488 class @code{gdb.Function}.
23490 @defun Function.__init__ (name)
23491 The initializer for @code{Function} registers the new function with
23492 @value{GDBN}. The argument @var{name} is the name of the function,
23493 a string. The function will be visible to the user as a convenience
23494 variable of type @code{internal function}, whose name is the same as
23495 the given @var{name}.
23497 The documentation for the new function is taken from the documentation
23498 string for the new class.
23501 @defun Function.invoke (@var{*args})
23502 When a convenience function is evaluated, its arguments are converted
23503 to instances of @code{gdb.Value}, and then the function's
23504 @code{invoke} method is called. Note that @value{GDBN} does not
23505 predetermine the arity of convenience functions. Instead, all
23506 available arguments are passed to @code{invoke}, following the
23507 standard Python calling convention. In particular, a convenience
23508 function can have default values for parameters without ill effect.
23510 The return value of this method is used as its value in the enclosing
23511 expression. If an ordinary Python value is returned, it is converted
23512 to a @code{gdb.Value} following the usual rules.
23515 The following code snippet shows how a trivial convenience function can
23516 be implemented in Python:
23519 class Greet (gdb.Function):
23520 """Return string to greet someone.
23521 Takes a name as argument."""
23523 def __init__ (self):
23524 super (Greet, self).__init__ ("greet")
23526 def invoke (self, name):
23527 return "Hello, %s!" % name.string ()
23532 The last line instantiates the class, and is necessary to trigger the
23533 registration of the function with @value{GDBN}. Depending on how the
23534 Python code is read into @value{GDBN}, you may need to import the
23535 @code{gdb} module explicitly.
23537 @node Progspaces In Python
23538 @subsubsection Program Spaces In Python
23540 @cindex progspaces in python
23541 @tindex gdb.Progspace
23543 A program space, or @dfn{progspace}, represents a symbolic view
23544 of an address space.
23545 It consists of all of the objfiles of the program.
23546 @xref{Objfiles In Python}.
23547 @xref{Inferiors and Programs, program spaces}, for more details
23548 about program spaces.
23550 The following progspace-related functions are available in the
23553 @findex gdb.current_progspace
23554 @defun gdb.current_progspace ()
23555 This function returns the program space of the currently selected inferior.
23556 @xref{Inferiors and Programs}.
23559 @findex gdb.progspaces
23560 @defun gdb.progspaces ()
23561 Return a sequence of all the progspaces currently known to @value{GDBN}.
23564 Each progspace is represented by an instance of the @code{gdb.Progspace}
23567 @defvar Progspace.filename
23568 The file name of the progspace as a string.
23571 @defvar Progspace.pretty_printers
23572 The @code{pretty_printers} attribute is a list of functions. It is
23573 used to look up pretty-printers. A @code{Value} is passed to each
23574 function in order; if the function returns @code{None}, then the
23575 search continues. Otherwise, the return value should be an object
23576 which is used to format the value. @xref{Pretty Printing API}, for more
23580 @node Objfiles In Python
23581 @subsubsection Objfiles In Python
23583 @cindex objfiles in python
23584 @tindex gdb.Objfile
23586 @value{GDBN} loads symbols for an inferior from various
23587 symbol-containing files (@pxref{Files}). These include the primary
23588 executable file, any shared libraries used by the inferior, and any
23589 separate debug info files (@pxref{Separate Debug Files}).
23590 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23592 The following objfile-related functions are available in the
23595 @findex gdb.current_objfile
23596 @defun gdb.current_objfile ()
23597 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23598 sets the ``current objfile'' to the corresponding objfile. This
23599 function returns the current objfile. If there is no current objfile,
23600 this function returns @code{None}.
23603 @findex gdb.objfiles
23604 @defun gdb.objfiles ()
23605 Return a sequence of all the objfiles current known to @value{GDBN}.
23606 @xref{Objfiles In Python}.
23609 Each objfile is represented by an instance of the @code{gdb.Objfile}
23612 @defvar Objfile.filename
23613 The file name of the objfile as a string.
23616 @defvar Objfile.pretty_printers
23617 The @code{pretty_printers} attribute is a list of functions. It is
23618 used to look up pretty-printers. A @code{Value} is passed to each
23619 function in order; if the function returns @code{None}, then the
23620 search continues. Otherwise, the return value should be an object
23621 which is used to format the value. @xref{Pretty Printing API}, for more
23625 A @code{gdb.Objfile} object has the following methods:
23627 @defun Objfile.is_valid ()
23628 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23629 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23630 if the object file it refers to is not loaded in @value{GDBN} any
23631 longer. All other @code{gdb.Objfile} methods will throw an exception
23632 if it is invalid at the time the method is called.
23635 @node Frames In Python
23636 @subsubsection Accessing inferior stack frames from Python.
23638 @cindex frames in python
23639 When the debugged program stops, @value{GDBN} is able to analyze its call
23640 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23641 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23642 while its corresponding frame exists in the inferior's stack. If you try
23643 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23644 exception (@pxref{Exception Handling}).
23646 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23650 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23654 The following frame-related functions are available in the @code{gdb} module:
23656 @findex gdb.selected_frame
23657 @defun gdb.selected_frame ()
23658 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23661 @findex gdb.newest_frame
23662 @defun gdb.newest_frame ()
23663 Return the newest frame object for the selected thread.
23666 @defun gdb.frame_stop_reason_string (reason)
23667 Return a string explaining the reason why @value{GDBN} stopped unwinding
23668 frames, as expressed by the given @var{reason} code (an integer, see the
23669 @code{unwind_stop_reason} method further down in this section).
23672 A @code{gdb.Frame} object has the following methods:
23675 @defun Frame.is_valid ()
23676 Returns true if the @code{gdb.Frame} object is valid, false if not.
23677 A frame object can become invalid if the frame it refers to doesn't
23678 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23679 an exception if it is invalid at the time the method is called.
23682 @defun Frame.name ()
23683 Returns the function name of the frame, or @code{None} if it can't be
23687 @defun Frame.type ()
23688 Returns the type of the frame. The value can be one of:
23690 @item gdb.NORMAL_FRAME
23691 An ordinary stack frame.
23693 @item gdb.DUMMY_FRAME
23694 A fake stack frame that was created by @value{GDBN} when performing an
23695 inferior function call.
23697 @item gdb.INLINE_FRAME
23698 A frame representing an inlined function. The function was inlined
23699 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23701 @item gdb.TAILCALL_FRAME
23702 A frame representing a tail call. @xref{Tail Call Frames}.
23704 @item gdb.SIGTRAMP_FRAME
23705 A signal trampoline frame. This is the frame created by the OS when
23706 it calls into a signal handler.
23708 @item gdb.ARCH_FRAME
23709 A fake stack frame representing a cross-architecture call.
23711 @item gdb.SENTINEL_FRAME
23712 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23717 @defun Frame.unwind_stop_reason ()
23718 Return an integer representing the reason why it's not possible to find
23719 more frames toward the outermost frame. Use
23720 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23721 function to a string. The value can be one of:
23724 @item gdb.FRAME_UNWIND_NO_REASON
23725 No particular reason (older frames should be available).
23727 @item gdb.FRAME_UNWIND_NULL_ID
23728 The previous frame's analyzer returns an invalid result.
23730 @item gdb.FRAME_UNWIND_OUTERMOST
23731 This frame is the outermost.
23733 @item gdb.FRAME_UNWIND_UNAVAILABLE
23734 Cannot unwind further, because that would require knowing the
23735 values of registers or memory that have not been collected.
23737 @item gdb.FRAME_UNWIND_INNER_ID
23738 This frame ID looks like it ought to belong to a NEXT frame,
23739 but we got it for a PREV frame. Normally, this is a sign of
23740 unwinder failure. It could also indicate stack corruption.
23742 @item gdb.FRAME_UNWIND_SAME_ID
23743 This frame has the same ID as the previous one. That means
23744 that unwinding further would almost certainly give us another
23745 frame with exactly the same ID, so break the chain. Normally,
23746 this is a sign of unwinder failure. It could also indicate
23749 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23750 The frame unwinder did not find any saved PC, but we needed
23751 one to unwind further.
23753 @item gdb.FRAME_UNWIND_FIRST_ERROR
23754 Any stop reason greater or equal to this value indicates some kind
23755 of error. This special value facilitates writing code that tests
23756 for errors in unwinding in a way that will work correctly even if
23757 the list of the other values is modified in future @value{GDBN}
23758 versions. Using it, you could write:
23760 reason = gdb.selected_frame().unwind_stop_reason ()
23761 reason_str = gdb.frame_stop_reason_string (reason)
23762 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23763 print "An error occured: %s" % reason_str
23770 Returns the frame's resume address.
23773 @defun Frame.block ()
23774 Return the frame's code block. @xref{Blocks In Python}.
23777 @defun Frame.function ()
23778 Return the symbol for the function corresponding to this frame.
23779 @xref{Symbols In Python}.
23782 @defun Frame.older ()
23783 Return the frame that called this frame.
23786 @defun Frame.newer ()
23787 Return the frame called by this frame.
23790 @defun Frame.find_sal ()
23791 Return the frame's symtab and line object.
23792 @xref{Symbol Tables In Python}.
23795 @defun Frame.read_var (variable @r{[}, block@r{]})
23796 Return the value of @var{variable} in this frame. If the optional
23797 argument @var{block} is provided, search for the variable from that
23798 block; otherwise start at the frame's current block (which is
23799 determined by the frame's current program counter). @var{variable}
23800 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23801 @code{gdb.Block} object.
23804 @defun Frame.select ()
23805 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23810 @node Blocks In Python
23811 @subsubsection Accessing frame blocks from Python.
23813 @cindex blocks in python
23816 Within each frame, @value{GDBN} maintains information on each block
23817 stored in that frame. These blocks are organized hierarchically, and
23818 are represented individually in Python as a @code{gdb.Block}.
23819 Please see @ref{Frames In Python}, for a more in-depth discussion on
23820 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23821 detailed technical information on @value{GDBN}'s book-keeping of the
23824 The following block-related functions are available in the @code{gdb}
23827 @findex gdb.block_for_pc
23828 @defun gdb.block_for_pc (pc)
23829 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23830 block cannot be found for the @var{pc} value specified, the function
23831 will return @code{None}.
23834 A @code{gdb.Block} object has the following methods:
23837 @defun Block.is_valid ()
23838 Returns @code{True} if the @code{gdb.Block} object is valid,
23839 @code{False} if not. A block object can become invalid if the block it
23840 refers to doesn't exist anymore in the inferior. All other
23841 @code{gdb.Block} methods will throw an exception if it is invalid at
23842 the time the method is called. This method is also made available to
23843 the Python iterator object that @code{gdb.Block} provides in an iteration
23844 context and via the Python @code{iter} built-in function.
23848 A @code{gdb.Block} object has the following attributes:
23851 @defvar Block.start
23852 The start address of the block. This attribute is not writable.
23856 The end address of the block. This attribute is not writable.
23859 @defvar Block.function
23860 The name of the block represented as a @code{gdb.Symbol}. If the
23861 block is not named, then this attribute holds @code{None}. This
23862 attribute is not writable.
23865 @defvar Block.superblock
23866 The block containing this block. If this parent block does not exist,
23867 this attribute holds @code{None}. This attribute is not writable.
23870 @defvar Block.global_block
23871 The global block associated with this block. This attribute is not
23875 @defvar Block.static_block
23876 The static block associated with this block. This attribute is not
23880 @defvar Block.is_global
23881 @code{True} if the @code{gdb.Block} object is a global block,
23882 @code{False} if not. This attribute is not
23886 @defvar Block.is_static
23887 @code{True} if the @code{gdb.Block} object is a static block,
23888 @code{False} if not. This attribute is not writable.
23892 @node Symbols In Python
23893 @subsubsection Python representation of Symbols.
23895 @cindex symbols in python
23898 @value{GDBN} represents every variable, function and type as an
23899 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23900 Similarly, Python represents these symbols in @value{GDBN} with the
23901 @code{gdb.Symbol} object.
23903 The following symbol-related functions are available in the @code{gdb}
23906 @findex gdb.lookup_symbol
23907 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23908 This function searches for a symbol by name. The search scope can be
23909 restricted to the parameters defined in the optional domain and block
23912 @var{name} is the name of the symbol. It must be a string. The
23913 optional @var{block} argument restricts the search to symbols visible
23914 in that @var{block}. The @var{block} argument must be a
23915 @code{gdb.Block} object. If omitted, the block for the current frame
23916 is used. The optional @var{domain} argument restricts
23917 the search to the domain type. The @var{domain} argument must be a
23918 domain constant defined in the @code{gdb} module and described later
23921 The result is a tuple of two elements.
23922 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23924 If the symbol is found, the second element is @code{True} if the symbol
23925 is a field of a method's object (e.g., @code{this} in C@t{++}),
23926 otherwise it is @code{False}.
23927 If the symbol is not found, the second element is @code{False}.
23930 @findex gdb.lookup_global_symbol
23931 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23932 This function searches for a global symbol by name.
23933 The search scope can be restricted to by the domain argument.
23935 @var{name} is the name of the symbol. It must be a string.
23936 The optional @var{domain} argument restricts the search to the domain type.
23937 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23938 module and described later in this chapter.
23940 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23944 A @code{gdb.Symbol} object has the following attributes:
23947 @defvar Symbol.type
23948 The type of the symbol or @code{None} if no type is recorded.
23949 This attribute is represented as a @code{gdb.Type} object.
23950 @xref{Types In Python}. This attribute is not writable.
23953 @defvar Symbol.symtab
23954 The symbol table in which the symbol appears. This attribute is
23955 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23956 Python}. This attribute is not writable.
23959 @defvar Symbol.name
23960 The name of the symbol as a string. This attribute is not writable.
23963 @defvar Symbol.linkage_name
23964 The name of the symbol, as used by the linker (i.e., may be mangled).
23965 This attribute is not writable.
23968 @defvar Symbol.print_name
23969 The name of the symbol in a form suitable for output. This is either
23970 @code{name} or @code{linkage_name}, depending on whether the user
23971 asked @value{GDBN} to display demangled or mangled names.
23974 @defvar Symbol.addr_class
23975 The address class of the symbol. This classifies how to find the value
23976 of a symbol. Each address class is a constant defined in the
23977 @code{gdb} module and described later in this chapter.
23980 @defvar Symbol.is_argument
23981 @code{True} if the symbol is an argument of a function.
23984 @defvar Symbol.is_constant
23985 @code{True} if the symbol is a constant.
23988 @defvar Symbol.is_function
23989 @code{True} if the symbol is a function or a method.
23992 @defvar Symbol.is_variable
23993 @code{True} if the symbol is a variable.
23997 A @code{gdb.Symbol} object has the following methods:
24000 @defun Symbol.is_valid ()
24001 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24002 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24003 the symbol it refers to does not exist in @value{GDBN} any longer.
24004 All other @code{gdb.Symbol} methods will throw an exception if it is
24005 invalid at the time the method is called.
24009 The available domain categories in @code{gdb.Symbol} are represented
24010 as constants in the @code{gdb} module:
24013 @findex SYMBOL_UNDEF_DOMAIN
24014 @findex gdb.SYMBOL_UNDEF_DOMAIN
24015 @item gdb.SYMBOL_UNDEF_DOMAIN
24016 This is used when a domain has not been discovered or none of the
24017 following domains apply. This usually indicates an error either
24018 in the symbol information or in @value{GDBN}'s handling of symbols.
24019 @findex SYMBOL_VAR_DOMAIN
24020 @findex gdb.SYMBOL_VAR_DOMAIN
24021 @item gdb.SYMBOL_VAR_DOMAIN
24022 This domain contains variables, function names, typedef names and enum
24024 @findex SYMBOL_STRUCT_DOMAIN
24025 @findex gdb.SYMBOL_STRUCT_DOMAIN
24026 @item gdb.SYMBOL_STRUCT_DOMAIN
24027 This domain holds struct, union and enum type names.
24028 @findex SYMBOL_LABEL_DOMAIN
24029 @findex gdb.SYMBOL_LABEL_DOMAIN
24030 @item gdb.SYMBOL_LABEL_DOMAIN
24031 This domain contains names of labels (for gotos).
24032 @findex SYMBOL_VARIABLES_DOMAIN
24033 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24034 @item gdb.SYMBOL_VARIABLES_DOMAIN
24035 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24036 contains everything minus functions and types.
24037 @findex SYMBOL_FUNCTIONS_DOMAIN
24038 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24039 @item gdb.SYMBOL_FUNCTION_DOMAIN
24040 This domain contains all functions.
24041 @findex SYMBOL_TYPES_DOMAIN
24042 @findex gdb.SYMBOL_TYPES_DOMAIN
24043 @item gdb.SYMBOL_TYPES_DOMAIN
24044 This domain contains all types.
24047 The available address class categories in @code{gdb.Symbol} are represented
24048 as constants in the @code{gdb} module:
24051 @findex SYMBOL_LOC_UNDEF
24052 @findex gdb.SYMBOL_LOC_UNDEF
24053 @item gdb.SYMBOL_LOC_UNDEF
24054 If this is returned by address class, it indicates an error either in
24055 the symbol information or in @value{GDBN}'s handling of symbols.
24056 @findex SYMBOL_LOC_CONST
24057 @findex gdb.SYMBOL_LOC_CONST
24058 @item gdb.SYMBOL_LOC_CONST
24059 Value is constant int.
24060 @findex SYMBOL_LOC_STATIC
24061 @findex gdb.SYMBOL_LOC_STATIC
24062 @item gdb.SYMBOL_LOC_STATIC
24063 Value is at a fixed address.
24064 @findex SYMBOL_LOC_REGISTER
24065 @findex gdb.SYMBOL_LOC_REGISTER
24066 @item gdb.SYMBOL_LOC_REGISTER
24067 Value is in a register.
24068 @findex SYMBOL_LOC_ARG
24069 @findex gdb.SYMBOL_LOC_ARG
24070 @item gdb.SYMBOL_LOC_ARG
24071 Value is an argument. This value is at the offset stored within the
24072 symbol inside the frame's argument list.
24073 @findex SYMBOL_LOC_REF_ARG
24074 @findex gdb.SYMBOL_LOC_REF_ARG
24075 @item gdb.SYMBOL_LOC_REF_ARG
24076 Value address is stored in the frame's argument list. Just like
24077 @code{LOC_ARG} except that the value's address is stored at the
24078 offset, not the value itself.
24079 @findex SYMBOL_LOC_REGPARM_ADDR
24080 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24081 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24082 Value is a specified register. Just like @code{LOC_REGISTER} except
24083 the register holds the address of the argument instead of the argument
24085 @findex SYMBOL_LOC_LOCAL
24086 @findex gdb.SYMBOL_LOC_LOCAL
24087 @item gdb.SYMBOL_LOC_LOCAL
24088 Value is a local variable.
24089 @findex SYMBOL_LOC_TYPEDEF
24090 @findex gdb.SYMBOL_LOC_TYPEDEF
24091 @item gdb.SYMBOL_LOC_TYPEDEF
24092 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24094 @findex SYMBOL_LOC_BLOCK
24095 @findex gdb.SYMBOL_LOC_BLOCK
24096 @item gdb.SYMBOL_LOC_BLOCK
24098 @findex SYMBOL_LOC_CONST_BYTES
24099 @findex gdb.SYMBOL_LOC_CONST_BYTES
24100 @item gdb.SYMBOL_LOC_CONST_BYTES
24101 Value is a byte-sequence.
24102 @findex SYMBOL_LOC_UNRESOLVED
24103 @findex gdb.SYMBOL_LOC_UNRESOLVED
24104 @item gdb.SYMBOL_LOC_UNRESOLVED
24105 Value is at a fixed address, but the address of the variable has to be
24106 determined from the minimal symbol table whenever the variable is
24108 @findex SYMBOL_LOC_OPTIMIZED_OUT
24109 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24110 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24111 The value does not actually exist in the program.
24112 @findex SYMBOL_LOC_COMPUTED
24113 @findex gdb.SYMBOL_LOC_COMPUTED
24114 @item gdb.SYMBOL_LOC_COMPUTED
24115 The value's address is a computed location.
24118 @node Symbol Tables In Python
24119 @subsubsection Symbol table representation in Python.
24121 @cindex symbol tables in python
24123 @tindex gdb.Symtab_and_line
24125 Access to symbol table data maintained by @value{GDBN} on the inferior
24126 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24127 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24128 from the @code{find_sal} method in @code{gdb.Frame} object.
24129 @xref{Frames In Python}.
24131 For more information on @value{GDBN}'s symbol table management, see
24132 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24134 A @code{gdb.Symtab_and_line} object has the following attributes:
24137 @defvar Symtab_and_line.symtab
24138 The symbol table object (@code{gdb.Symtab}) for this frame.
24139 This attribute is not writable.
24142 @defvar Symtab_and_line.pc
24143 Indicates the current program counter address. This attribute is not
24147 @defvar Symtab_and_line.line
24148 Indicates the current line number for this object. This
24149 attribute is not writable.
24153 A @code{gdb.Symtab_and_line} object has the following methods:
24156 @defun Symtab_and_line.is_valid ()
24157 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24158 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24159 invalid if the Symbol table and line object it refers to does not
24160 exist in @value{GDBN} any longer. All other
24161 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24162 invalid at the time the method is called.
24166 A @code{gdb.Symtab} object has the following attributes:
24169 @defvar Symtab.filename
24170 The symbol table's source filename. This attribute is not writable.
24173 @defvar Symtab.objfile
24174 The symbol table's backing object file. @xref{Objfiles In Python}.
24175 This attribute is not writable.
24179 A @code{gdb.Symtab} object has the following methods:
24182 @defun Symtab.is_valid ()
24183 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24184 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24185 the symbol table it refers to does not exist in @value{GDBN} any
24186 longer. All other @code{gdb.Symtab} methods will throw an exception
24187 if it is invalid at the time the method is called.
24190 @defun Symtab.fullname ()
24191 Return the symbol table's source absolute file name.
24195 @node Breakpoints In Python
24196 @subsubsection Manipulating breakpoints using Python
24198 @cindex breakpoints in python
24199 @tindex gdb.Breakpoint
24201 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24204 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24205 Create a new breakpoint. @var{spec} is a string naming the
24206 location of the breakpoint, or an expression that defines a
24207 watchpoint. The contents can be any location recognized by the
24208 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24209 command. The optional @var{type} denotes the breakpoint to create
24210 from the types defined later in this chapter. This argument can be
24211 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24212 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24213 allows the breakpoint to become invisible to the user. The breakpoint
24214 will neither be reported when created, nor will it be listed in the
24215 output from @code{info breakpoints} (but will be listed with the
24216 @code{maint info breakpoints} command). The optional @var{wp_class}
24217 argument defines the class of watchpoint to create, if @var{type} is
24218 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24219 assumed to be a @code{gdb.WP_WRITE} class.
24222 @defun Breakpoint.stop (self)
24223 The @code{gdb.Breakpoint} class can be sub-classed and, in
24224 particular, you may choose to implement the @code{stop} method.
24225 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24226 it will be called when the inferior reaches any location of a
24227 breakpoint which instantiates that sub-class. If the method returns
24228 @code{True}, the inferior will be stopped at the location of the
24229 breakpoint, otherwise the inferior will continue.
24231 If there are multiple breakpoints at the same location with a
24232 @code{stop} method, each one will be called regardless of the
24233 return status of the previous. This ensures that all @code{stop}
24234 methods have a chance to execute at that location. In this scenario
24235 if one of the methods returns @code{True} but the others return
24236 @code{False}, the inferior will still be stopped.
24238 You should not alter the execution state of the inferior (i.e.@:, step,
24239 next, etc.), alter the current frame context (i.e.@:, change the current
24240 active frame), or alter, add or delete any breakpoint. As a general
24241 rule, you should not alter any data within @value{GDBN} or the inferior
24244 Example @code{stop} implementation:
24247 class MyBreakpoint (gdb.Breakpoint):
24249 inf_val = gdb.parse_and_eval("foo")
24256 The available watchpoint types represented by constants are defined in the
24261 @findex gdb.WP_READ
24263 Read only watchpoint.
24266 @findex gdb.WP_WRITE
24268 Write only watchpoint.
24271 @findex gdb.WP_ACCESS
24272 @item gdb.WP_ACCESS
24273 Read/Write watchpoint.
24276 @defun Breakpoint.is_valid ()
24277 Return @code{True} if this @code{Breakpoint} object is valid,
24278 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24279 if the user deletes the breakpoint. In this case, the object still
24280 exists, but the underlying breakpoint does not. In the cases of
24281 watchpoint scope, the watchpoint remains valid even if execution of the
24282 inferior leaves the scope of that watchpoint.
24285 @defun Breakpoint.delete
24286 Permanently deletes the @value{GDBN} breakpoint. This also
24287 invalidates the Python @code{Breakpoint} object. Any further access
24288 to this object's attributes or methods will raise an error.
24291 @defvar Breakpoint.enabled
24292 This attribute is @code{True} if the breakpoint is enabled, and
24293 @code{False} otherwise. This attribute is writable.
24296 @defvar Breakpoint.silent
24297 This attribute is @code{True} if the breakpoint is silent, and
24298 @code{False} otherwise. This attribute is writable.
24300 Note that a breakpoint can also be silent if it has commands and the
24301 first command is @code{silent}. This is not reported by the
24302 @code{silent} attribute.
24305 @defvar Breakpoint.thread
24306 If the breakpoint is thread-specific, this attribute holds the thread
24307 id. If the breakpoint is not thread-specific, this attribute is
24308 @code{None}. This attribute is writable.
24311 @defvar Breakpoint.task
24312 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24313 id. If the breakpoint is not task-specific (or the underlying
24314 language is not Ada), this attribute is @code{None}. This attribute
24318 @defvar Breakpoint.ignore_count
24319 This attribute holds the ignore count for the breakpoint, an integer.
24320 This attribute is writable.
24323 @defvar Breakpoint.number
24324 This attribute holds the breakpoint's number --- the identifier used by
24325 the user to manipulate the breakpoint. This attribute is not writable.
24328 @defvar Breakpoint.type
24329 This attribute holds the breakpoint's type --- the identifier used to
24330 determine the actual breakpoint type or use-case. This attribute is not
24334 @defvar Breakpoint.visible
24335 This attribute tells whether the breakpoint is visible to the user
24336 when set, or when the @samp{info breakpoints} command is run. This
24337 attribute is not writable.
24340 The available types are represented by constants defined in the @code{gdb}
24344 @findex BP_BREAKPOINT
24345 @findex gdb.BP_BREAKPOINT
24346 @item gdb.BP_BREAKPOINT
24347 Normal code breakpoint.
24349 @findex BP_WATCHPOINT
24350 @findex gdb.BP_WATCHPOINT
24351 @item gdb.BP_WATCHPOINT
24352 Watchpoint breakpoint.
24354 @findex BP_HARDWARE_WATCHPOINT
24355 @findex gdb.BP_HARDWARE_WATCHPOINT
24356 @item gdb.BP_HARDWARE_WATCHPOINT
24357 Hardware assisted watchpoint.
24359 @findex BP_READ_WATCHPOINT
24360 @findex gdb.BP_READ_WATCHPOINT
24361 @item gdb.BP_READ_WATCHPOINT
24362 Hardware assisted read watchpoint.
24364 @findex BP_ACCESS_WATCHPOINT
24365 @findex gdb.BP_ACCESS_WATCHPOINT
24366 @item gdb.BP_ACCESS_WATCHPOINT
24367 Hardware assisted access watchpoint.
24370 @defvar Breakpoint.hit_count
24371 This attribute holds the hit count for the breakpoint, an integer.
24372 This attribute is writable, but currently it can only be set to zero.
24375 @defvar Breakpoint.location
24376 This attribute holds the location of the breakpoint, as specified by
24377 the user. It is a string. If the breakpoint does not have a location
24378 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24379 attribute is not writable.
24382 @defvar Breakpoint.expression
24383 This attribute holds a breakpoint expression, as specified by
24384 the user. It is a string. If the breakpoint does not have an
24385 expression (the breakpoint is not a watchpoint) the attribute's value
24386 is @code{None}. This attribute is not writable.
24389 @defvar Breakpoint.condition
24390 This attribute holds the condition of the breakpoint, as specified by
24391 the user. It is a string. If there is no condition, this attribute's
24392 value is @code{None}. This attribute is writable.
24395 @defvar Breakpoint.commands
24396 This attribute holds the commands attached to the breakpoint. If
24397 there are commands, this attribute's value is a string holding all the
24398 commands, separated by newlines. If there are no commands, this
24399 attribute is @code{None}. This attribute is not writable.
24402 @node Finish Breakpoints in Python
24403 @subsubsection Finish Breakpoints
24405 @cindex python finish breakpoints
24406 @tindex gdb.FinishBreakpoint
24408 A finish breakpoint is a temporary breakpoint set at the return address of
24409 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24410 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24411 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24412 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24413 Finish breakpoints are thread specific and must be create with the right
24416 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24417 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24418 object @var{frame}. If @var{frame} is not provided, this defaults to the
24419 newest frame. The optional @var{internal} argument allows the breakpoint to
24420 become invisible to the user. @xref{Breakpoints In Python}, for further
24421 details about this argument.
24424 @defun FinishBreakpoint.out_of_scope (self)
24425 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24426 @code{return} command, @dots{}), a function may not properly terminate, and
24427 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24428 situation, the @code{out_of_scope} callback will be triggered.
24430 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24434 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24436 print "normal finish"
24439 def out_of_scope ():
24440 print "abnormal finish"
24444 @defvar FinishBreakpoint.return_value
24445 When @value{GDBN} is stopped at a finish breakpoint and the frame
24446 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24447 attribute will contain a @code{gdb.Value} object corresponding to the return
24448 value of the function. The value will be @code{None} if the function return
24449 type is @code{void} or if the return value was not computable. This attribute
24453 @node Lazy Strings In Python
24454 @subsubsection Python representation of lazy strings.
24456 @cindex lazy strings in python
24457 @tindex gdb.LazyString
24459 A @dfn{lazy string} is a string whose contents is not retrieved or
24460 encoded until it is needed.
24462 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24463 @code{address} that points to a region of memory, an @code{encoding}
24464 that will be used to encode that region of memory, and a @code{length}
24465 to delimit the region of memory that represents the string. The
24466 difference between a @code{gdb.LazyString} and a string wrapped within
24467 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24468 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24469 retrieved and encoded during printing, while a @code{gdb.Value}
24470 wrapping a string is immediately retrieved and encoded on creation.
24472 A @code{gdb.LazyString} object has the following functions:
24474 @defun LazyString.value ()
24475 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24476 will point to the string in memory, but will lose all the delayed
24477 retrieval, encoding and handling that @value{GDBN} applies to a
24478 @code{gdb.LazyString}.
24481 @defvar LazyString.address
24482 This attribute holds the address of the string. This attribute is not
24486 @defvar LazyString.length
24487 This attribute holds the length of the string in characters. If the
24488 length is -1, then the string will be fetched and encoded up to the
24489 first null of appropriate width. This attribute is not writable.
24492 @defvar LazyString.encoding
24493 This attribute holds the encoding that will be applied to the string
24494 when the string is printed by @value{GDBN}. If the encoding is not
24495 set, or contains an empty string, then @value{GDBN} will select the
24496 most appropriate encoding when the string is printed. This attribute
24500 @defvar LazyString.type
24501 This attribute holds the type that is represented by the lazy string's
24502 type. For a lazy string this will always be a pointer type. To
24503 resolve this to the lazy string's character type, use the type's
24504 @code{target} method. @xref{Types In Python}. This attribute is not
24509 @subsection Auto-loading
24510 @cindex auto-loading, Python
24512 When a new object file is read (for example, due to the @code{file}
24513 command, or because the inferior has loaded a shared library),
24514 @value{GDBN} will look for Python support scripts in several ways:
24515 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24518 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24519 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24520 * Which flavor to choose?::
24523 The auto-loading feature is useful for supplying application-specific
24524 debugging commands and scripts.
24526 Auto-loading can be enabled or disabled,
24527 and the list of auto-loaded scripts can be printed.
24530 @kindex set auto-load-scripts
24531 @item set auto-load-scripts [yes|no]
24532 Enable or disable the auto-loading of Python scripts.
24534 @kindex show auto-load-scripts
24535 @item show auto-load-scripts
24536 Show whether auto-loading of Python scripts is enabled or disabled.
24538 @kindex info auto-load-scripts
24539 @cindex print list of auto-loaded scripts
24540 @item info auto-load-scripts [@var{regexp}]
24541 Print the list of all scripts that @value{GDBN} auto-loaded.
24543 Also printed is the list of scripts that were mentioned in
24544 the @code{.debug_gdb_scripts} section and were not found
24545 (@pxref{.debug_gdb_scripts section}).
24546 This is useful because their names are not printed when @value{GDBN}
24547 tries to load them and fails. There may be many of them, and printing
24548 an error message for each one is problematic.
24550 If @var{regexp} is supplied only scripts with matching names are printed.
24555 (gdb) info auto-load-scripts
24557 Yes py-section-script.py
24558 full name: /tmp/py-section-script.py
24559 Missing my-foo-pretty-printers.py
24563 When reading an auto-loaded file, @value{GDBN} sets the
24564 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24565 function (@pxref{Objfiles In Python}). This can be useful for
24566 registering objfile-specific pretty-printers.
24568 @node objfile-gdb.py file
24569 @subsubsection The @file{@var{objfile}-gdb.py} file
24570 @cindex @file{@var{objfile}-gdb.py}
24572 When a new object file is read, @value{GDBN} looks for
24573 a file named @file{@var{objfile}-gdb.py},
24574 where @var{objfile} is the object file's real name, formed by ensuring
24575 that the file name is absolute, following all symlinks, and resolving
24576 @code{.} and @code{..} components. If this file exists and is
24577 readable, @value{GDBN} will evaluate it as a Python script.
24579 If this file does not exist, and if the parameter
24580 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24581 then @value{GDBN} will look for @var{real-name} in all of the
24582 directories mentioned in the value of @code{debug-file-directory}.
24584 Finally, if this file does not exist, then @value{GDBN} will look for
24585 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24586 @var{data-directory} is @value{GDBN}'s data directory (available via
24587 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24588 is the object file's real name, as described above.
24590 @value{GDBN} does not track which files it has already auto-loaded this way.
24591 @value{GDBN} will load the associated script every time the corresponding
24592 @var{objfile} is opened.
24593 So your @file{-gdb.py} file should be careful to avoid errors if it
24594 is evaluated more than once.
24596 @node .debug_gdb_scripts section
24597 @subsubsection The @code{.debug_gdb_scripts} section
24598 @cindex @code{.debug_gdb_scripts} section
24600 For systems using file formats like ELF and COFF,
24601 when @value{GDBN} loads a new object file
24602 it will look for a special section named @samp{.debug_gdb_scripts}.
24603 If this section exists, its contents is a list of names of scripts to load.
24605 @value{GDBN} will look for each specified script file first in the
24606 current directory and then along the source search path
24607 (@pxref{Source Path, ,Specifying Source Directories}),
24608 except that @file{$cdir} is not searched, since the compilation
24609 directory is not relevant to scripts.
24611 Entries can be placed in section @code{.debug_gdb_scripts} with,
24612 for example, this GCC macro:
24615 /* Note: The "MS" section flags are to remove duplicates. */
24616 #define DEFINE_GDB_SCRIPT(script_name) \
24618 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24620 .asciz \"" script_name "\"\n\
24626 Then one can reference the macro in a header or source file like this:
24629 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24632 The script name may include directories if desired.
24634 If the macro is put in a header, any application or library
24635 using this header will get a reference to the specified script.
24637 @node Which flavor to choose?
24638 @subsubsection Which flavor to choose?
24640 Given the multiple ways of auto-loading Python scripts, it might not always
24641 be clear which one to choose. This section provides some guidance.
24643 Benefits of the @file{-gdb.py} way:
24647 Can be used with file formats that don't support multiple sections.
24650 Ease of finding scripts for public libraries.
24652 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24653 in the source search path.
24654 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24655 isn't a source directory in which to find the script.
24658 Doesn't require source code additions.
24661 Benefits of the @code{.debug_gdb_scripts} way:
24665 Works with static linking.
24667 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24668 trigger their loading. When an application is statically linked the only
24669 objfile available is the executable, and it is cumbersome to attach all the
24670 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24673 Works with classes that are entirely inlined.
24675 Some classes can be entirely inlined, and thus there may not be an associated
24676 shared library to attach a @file{-gdb.py} script to.
24679 Scripts needn't be copied out of the source tree.
24681 In some circumstances, apps can be built out of large collections of internal
24682 libraries, and the build infrastructure necessary to install the
24683 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24684 cumbersome. It may be easier to specify the scripts in the
24685 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24686 top of the source tree to the source search path.
24689 @node Python modules
24690 @subsection Python modules
24691 @cindex python modules
24693 @value{GDBN} comes with several modules to assist writing Python code.
24696 * gdb.printing:: Building and registering pretty-printers.
24697 * gdb.types:: Utilities for working with types.
24698 * gdb.prompt:: Utilities for prompt value substitution.
24702 @subsubsection gdb.printing
24703 @cindex gdb.printing
24705 This module provides a collection of utilities for working with
24709 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24710 This class specifies the API that makes @samp{info pretty-printer},
24711 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24712 Pretty-printers should generally inherit from this class.
24714 @item SubPrettyPrinter (@var{name})
24715 For printers that handle multiple types, this class specifies the
24716 corresponding API for the subprinters.
24718 @item RegexpCollectionPrettyPrinter (@var{name})
24719 Utility class for handling multiple printers, all recognized via
24720 regular expressions.
24721 @xref{Writing a Pretty-Printer}, for an example.
24723 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24724 Register @var{printer} with the pretty-printer list of @var{obj}.
24725 If @var{replace} is @code{True} then any existing copy of the printer
24726 is replaced. Otherwise a @code{RuntimeError} exception is raised
24727 if a printer with the same name already exists.
24731 @subsubsection gdb.types
24734 This module provides a collection of utilities for working with
24735 @code{gdb.Types} objects.
24738 @item get_basic_type (@var{type})
24739 Return @var{type} with const and volatile qualifiers stripped,
24740 and with typedefs and C@t{++} references converted to the underlying type.
24745 typedef const int const_int;
24747 const_int& foo_ref (foo);
24748 int main () @{ return 0; @}
24755 (gdb) python import gdb.types
24756 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24757 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24761 @item has_field (@var{type}, @var{field})
24762 Return @code{True} if @var{type}, assumed to be a type with fields
24763 (e.g., a structure or union), has field @var{field}.
24765 @item make_enum_dict (@var{enum_type})
24766 Return a Python @code{dictionary} type produced from @var{enum_type}.
24768 @item deep_items (@var{type})
24769 Returns a Python iterator similar to the standard
24770 @code{gdb.Type.iteritems} method, except that the iterator returned
24771 by @code{deep_items} will recursively traverse anonymous struct or
24772 union fields. For example:
24786 Then in @value{GDBN}:
24788 (@value{GDBP}) python import gdb.types
24789 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24790 (@value{GDBP}) python print struct_a.keys ()
24792 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24793 @{['a', 'b0', 'b1']@}
24799 @subsubsection gdb.prompt
24802 This module provides a method for prompt value-substitution.
24805 @item substitute_prompt (@var{string})
24806 Return @var{string} with escape sequences substituted by values. Some
24807 escape sequences take arguments. You can specify arguments inside
24808 ``@{@}'' immediately following the escape sequence.
24810 The escape sequences you can pass to this function are:
24814 Substitute a backslash.
24816 Substitute an ESC character.
24818 Substitute the selected frame; an argument names a frame parameter.
24820 Substitute a newline.
24822 Substitute a parameter's value; the argument names the parameter.
24824 Substitute a carriage return.
24826 Substitute the selected thread; an argument names a thread parameter.
24828 Substitute the version of GDB.
24830 Substitute the current working directory.
24832 Begin a sequence of non-printing characters. These sequences are
24833 typically used with the ESC character, and are not counted in the string
24834 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24835 blue-colored ``(gdb)'' prompt where the length is five.
24837 End a sequence of non-printing characters.
24843 substitute_prompt (``frame: \f,
24844 print arguments: \p@{print frame-arguments@}'')
24847 @exdent will return the string:
24850 "frame: main, print arguments: scalars"
24855 @section Creating new spellings of existing commands
24856 @cindex aliases for commands
24858 It is often useful to define alternate spellings of existing commands.
24859 For example, if a new @value{GDBN} command defined in Python has
24860 a long name to type, it is handy to have an abbreviated version of it
24861 that involves less typing.
24863 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24864 of the @samp{step} command even though it is otherwise an ambiguous
24865 abbreviation of other commands like @samp{set} and @samp{show}.
24867 Aliases are also used to provide shortened or more common versions
24868 of multi-word commands. For example, @value{GDBN} provides the
24869 @samp{tty} alias of the @samp{set inferior-tty} command.
24871 You can define a new alias with the @samp{alias} command.
24876 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24880 @var{ALIAS} specifies the name of the new alias.
24881 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24884 @var{COMMAND} specifies the name of an existing command
24885 that is being aliased.
24887 The @samp{-a} option specifies that the new alias is an abbreviation
24888 of the command. Abbreviations are not shown in command
24889 lists displayed by the @samp{help} command.
24891 The @samp{--} option specifies the end of options,
24892 and is useful when @var{ALIAS} begins with a dash.
24894 Here is a simple example showing how to make an abbreviation
24895 of a command so that there is less to type.
24896 Suppose you were tired of typing @samp{disas}, the current
24897 shortest unambiguous abbreviation of the @samp{disassemble} command
24898 and you wanted an even shorter version named @samp{di}.
24899 The following will accomplish this.
24902 (gdb) alias -a di = disas
24905 Note that aliases are different from user-defined commands.
24906 With a user-defined command, you also need to write documentation
24907 for it with the @samp{document} command.
24908 An alias automatically picks up the documentation of the existing command.
24910 Here is an example where we make @samp{elms} an abbreviation of
24911 @samp{elements} in the @samp{set print elements} command.
24912 This is to show that you can make an abbreviation of any part
24916 (gdb) alias -a set print elms = set print elements
24917 (gdb) alias -a show print elms = show print elements
24918 (gdb) set p elms 20
24920 Limit on string chars or array elements to print is 200.
24923 Note that if you are defining an alias of a @samp{set} command,
24924 and you want to have an alias for the corresponding @samp{show}
24925 command, then you need to define the latter separately.
24927 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24928 @var{ALIAS}, just as they are normally.
24931 (gdb) alias -a set pr elms = set p ele
24934 Finally, here is an example showing the creation of a one word
24935 alias for a more complex command.
24936 This creates alias @samp{spe} of the command @samp{set print elements}.
24939 (gdb) alias spe = set print elements
24944 @chapter Command Interpreters
24945 @cindex command interpreters
24947 @value{GDBN} supports multiple command interpreters, and some command
24948 infrastructure to allow users or user interface writers to switch
24949 between interpreters or run commands in other interpreters.
24951 @value{GDBN} currently supports two command interpreters, the console
24952 interpreter (sometimes called the command-line interpreter or @sc{cli})
24953 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24954 describes both of these interfaces in great detail.
24956 By default, @value{GDBN} will start with the console interpreter.
24957 However, the user may choose to start @value{GDBN} with another
24958 interpreter by specifying the @option{-i} or @option{--interpreter}
24959 startup options. Defined interpreters include:
24963 @cindex console interpreter
24964 The traditional console or command-line interpreter. This is the most often
24965 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24966 @value{GDBN} will use this interpreter.
24969 @cindex mi interpreter
24970 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24971 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24972 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24976 @cindex mi2 interpreter
24977 The current @sc{gdb/mi} interface.
24980 @cindex mi1 interpreter
24981 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24985 @cindex invoke another interpreter
24986 The interpreter being used by @value{GDBN} may not be dynamically
24987 switched at runtime. Although possible, this could lead to a very
24988 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24989 enters the command "interpreter-set console" in a console view,
24990 @value{GDBN} would switch to using the console interpreter, rendering
24991 the IDE inoperable!
24993 @kindex interpreter-exec
24994 Although you may only choose a single interpreter at startup, you may execute
24995 commands in any interpreter from the current interpreter using the appropriate
24996 command. If you are running the console interpreter, simply use the
24997 @code{interpreter-exec} command:
25000 interpreter-exec mi "-data-list-register-names"
25003 @sc{gdb/mi} has a similar command, although it is only available in versions of
25004 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25007 @chapter @value{GDBN} Text User Interface
25009 @cindex Text User Interface
25012 * TUI Overview:: TUI overview
25013 * TUI Keys:: TUI key bindings
25014 * TUI Single Key Mode:: TUI single key mode
25015 * TUI Commands:: TUI-specific commands
25016 * TUI Configuration:: TUI configuration variables
25019 The @value{GDBN} Text User Interface (TUI) is a terminal
25020 interface which uses the @code{curses} library to show the source
25021 file, the assembly output, the program registers and @value{GDBN}
25022 commands in separate text windows. The TUI mode is supported only
25023 on platforms where a suitable version of the @code{curses} library
25026 The TUI mode is enabled by default when you invoke @value{GDBN} as
25027 @samp{@value{GDBP} -tui}.
25028 You can also switch in and out of TUI mode while @value{GDBN} runs by
25029 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25030 @xref{TUI Keys, ,TUI Key Bindings}.
25033 @section TUI Overview
25035 In TUI mode, @value{GDBN} can display several text windows:
25039 This window is the @value{GDBN} command window with the @value{GDBN}
25040 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25041 managed using readline.
25044 The source window shows the source file of the program. The current
25045 line and active breakpoints are displayed in this window.
25048 The assembly window shows the disassembly output of the program.
25051 This window shows the processor registers. Registers are highlighted
25052 when their values change.
25055 The source and assembly windows show the current program position
25056 by highlighting the current line and marking it with a @samp{>} marker.
25057 Breakpoints are indicated with two markers. The first marker
25058 indicates the breakpoint type:
25062 Breakpoint which was hit at least once.
25065 Breakpoint which was never hit.
25068 Hardware breakpoint which was hit at least once.
25071 Hardware breakpoint which was never hit.
25074 The second marker indicates whether the breakpoint is enabled or not:
25078 Breakpoint is enabled.
25081 Breakpoint is disabled.
25084 The source, assembly and register windows are updated when the current
25085 thread changes, when the frame changes, or when the program counter
25088 These windows are not all visible at the same time. The command
25089 window is always visible. The others can be arranged in several
25100 source and assembly,
25103 source and registers, or
25106 assembly and registers.
25109 A status line above the command window shows the following information:
25113 Indicates the current @value{GDBN} target.
25114 (@pxref{Targets, ,Specifying a Debugging Target}).
25117 Gives the current process or thread number.
25118 When no process is being debugged, this field is set to @code{No process}.
25121 Gives the current function name for the selected frame.
25122 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25123 When there is no symbol corresponding to the current program counter,
25124 the string @code{??} is displayed.
25127 Indicates the current line number for the selected frame.
25128 When the current line number is not known, the string @code{??} is displayed.
25131 Indicates the current program counter address.
25135 @section TUI Key Bindings
25136 @cindex TUI key bindings
25138 The TUI installs several key bindings in the readline keymaps
25139 @ifset SYSTEM_READLINE
25140 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25142 @ifclear SYSTEM_READLINE
25143 (@pxref{Command Line Editing}).
25145 The following key bindings are installed for both TUI mode and the
25146 @value{GDBN} standard mode.
25155 Enter or leave the TUI mode. When leaving the TUI mode,
25156 the curses window management stops and @value{GDBN} operates using
25157 its standard mode, writing on the terminal directly. When reentering
25158 the TUI mode, control is given back to the curses windows.
25159 The screen is then refreshed.
25163 Use a TUI layout with only one window. The layout will
25164 either be @samp{source} or @samp{assembly}. When the TUI mode
25165 is not active, it will switch to the TUI mode.
25167 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25171 Use a TUI layout with at least two windows. When the current
25172 layout already has two windows, the next layout with two windows is used.
25173 When a new layout is chosen, one window will always be common to the
25174 previous layout and the new one.
25176 Think of it as the Emacs @kbd{C-x 2} binding.
25180 Change the active window. The TUI associates several key bindings
25181 (like scrolling and arrow keys) with the active window. This command
25182 gives the focus to the next TUI window.
25184 Think of it as the Emacs @kbd{C-x o} binding.
25188 Switch in and out of the TUI SingleKey mode that binds single
25189 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25192 The following key bindings only work in the TUI mode:
25197 Scroll the active window one page up.
25201 Scroll the active window one page down.
25205 Scroll the active window one line up.
25209 Scroll the active window one line down.
25213 Scroll the active window one column left.
25217 Scroll the active window one column right.
25221 Refresh the screen.
25224 Because the arrow keys scroll the active window in the TUI mode, they
25225 are not available for their normal use by readline unless the command
25226 window has the focus. When another window is active, you must use
25227 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25228 and @kbd{C-f} to control the command window.
25230 @node TUI Single Key Mode
25231 @section TUI Single Key Mode
25232 @cindex TUI single key mode
25234 The TUI also provides a @dfn{SingleKey} mode, which binds several
25235 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25236 switch into this mode, where the following key bindings are used:
25239 @kindex c @r{(SingleKey TUI key)}
25243 @kindex d @r{(SingleKey TUI key)}
25247 @kindex f @r{(SingleKey TUI key)}
25251 @kindex n @r{(SingleKey TUI key)}
25255 @kindex q @r{(SingleKey TUI key)}
25257 exit the SingleKey mode.
25259 @kindex r @r{(SingleKey TUI key)}
25263 @kindex s @r{(SingleKey TUI key)}
25267 @kindex u @r{(SingleKey TUI key)}
25271 @kindex v @r{(SingleKey TUI key)}
25275 @kindex w @r{(SingleKey TUI key)}
25280 Other keys temporarily switch to the @value{GDBN} command prompt.
25281 The key that was pressed is inserted in the editing buffer so that
25282 it is possible to type most @value{GDBN} commands without interaction
25283 with the TUI SingleKey mode. Once the command is entered the TUI
25284 SingleKey mode is restored. The only way to permanently leave
25285 this mode is by typing @kbd{q} or @kbd{C-x s}.
25289 @section TUI-specific Commands
25290 @cindex TUI commands
25292 The TUI has specific commands to control the text windows.
25293 These commands are always available, even when @value{GDBN} is not in
25294 the TUI mode. When @value{GDBN} is in the standard mode, most
25295 of these commands will automatically switch to the TUI mode.
25297 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25298 terminal, or @value{GDBN} has been started with the machine interface
25299 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25300 these commands will fail with an error, because it would not be
25301 possible or desirable to enable curses window management.
25306 List and give the size of all displayed windows.
25310 Display the next layout.
25313 Display the previous layout.
25316 Display the source window only.
25319 Display the assembly window only.
25322 Display the source and assembly window.
25325 Display the register window together with the source or assembly window.
25329 Make the next window active for scrolling.
25332 Make the previous window active for scrolling.
25335 Make the source window active for scrolling.
25338 Make the assembly window active for scrolling.
25341 Make the register window active for scrolling.
25344 Make the command window active for scrolling.
25348 Refresh the screen. This is similar to typing @kbd{C-L}.
25350 @item tui reg float
25352 Show the floating point registers in the register window.
25354 @item tui reg general
25355 Show the general registers in the register window.
25358 Show the next register group. The list of register groups as well as
25359 their order is target specific. The predefined register groups are the
25360 following: @code{general}, @code{float}, @code{system}, @code{vector},
25361 @code{all}, @code{save}, @code{restore}.
25363 @item tui reg system
25364 Show the system registers in the register window.
25368 Update the source window and the current execution point.
25370 @item winheight @var{name} +@var{count}
25371 @itemx winheight @var{name} -@var{count}
25373 Change the height of the window @var{name} by @var{count}
25374 lines. Positive counts increase the height, while negative counts
25377 @item tabset @var{nchars}
25379 Set the width of tab stops to be @var{nchars} characters.
25382 @node TUI Configuration
25383 @section TUI Configuration Variables
25384 @cindex TUI configuration variables
25386 Several configuration variables control the appearance of TUI windows.
25389 @item set tui border-kind @var{kind}
25390 @kindex set tui border-kind
25391 Select the border appearance for the source, assembly and register windows.
25392 The possible values are the following:
25395 Use a space character to draw the border.
25398 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25401 Use the Alternate Character Set to draw the border. The border is
25402 drawn using character line graphics if the terminal supports them.
25405 @item set tui border-mode @var{mode}
25406 @kindex set tui border-mode
25407 @itemx set tui active-border-mode @var{mode}
25408 @kindex set tui active-border-mode
25409 Select the display attributes for the borders of the inactive windows
25410 or the active window. The @var{mode} can be one of the following:
25413 Use normal attributes to display the border.
25419 Use reverse video mode.
25422 Use half bright mode.
25424 @item half-standout
25425 Use half bright and standout mode.
25428 Use extra bright or bold mode.
25430 @item bold-standout
25431 Use extra bright or bold and standout mode.
25436 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25439 @cindex @sc{gnu} Emacs
25440 A special interface allows you to use @sc{gnu} Emacs to view (and
25441 edit) the source files for the program you are debugging with
25444 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25445 executable file you want to debug as an argument. This command starts
25446 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25447 created Emacs buffer.
25448 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25450 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25455 All ``terminal'' input and output goes through an Emacs buffer, called
25458 This applies both to @value{GDBN} commands and their output, and to the input
25459 and output done by the program you are debugging.
25461 This is useful because it means that you can copy the text of previous
25462 commands and input them again; you can even use parts of the output
25465 All the facilities of Emacs' Shell mode are available for interacting
25466 with your program. In particular, you can send signals the usual
25467 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25471 @value{GDBN} displays source code through Emacs.
25473 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25474 source file for that frame and puts an arrow (@samp{=>}) at the
25475 left margin of the current line. Emacs uses a separate buffer for
25476 source display, and splits the screen to show both your @value{GDBN} session
25479 Explicit @value{GDBN} @code{list} or search commands still produce output as
25480 usual, but you probably have no reason to use them from Emacs.
25483 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25484 a graphical mode, enabled by default, which provides further buffers
25485 that can control the execution and describe the state of your program.
25486 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25488 If you specify an absolute file name when prompted for the @kbd{M-x
25489 gdb} argument, then Emacs sets your current working directory to where
25490 your program resides. If you only specify the file name, then Emacs
25491 sets your current working directory to the directory associated
25492 with the previous buffer. In this case, @value{GDBN} may find your
25493 program by searching your environment's @code{PATH} variable, but on
25494 some operating systems it might not find the source. So, although the
25495 @value{GDBN} input and output session proceeds normally, the auxiliary
25496 buffer does not display the current source and line of execution.
25498 The initial working directory of @value{GDBN} is printed on the top
25499 line of the GUD buffer and this serves as a default for the commands
25500 that specify files for @value{GDBN} to operate on. @xref{Files,
25501 ,Commands to Specify Files}.
25503 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25504 need to call @value{GDBN} by a different name (for example, if you
25505 keep several configurations around, with different names) you can
25506 customize the Emacs variable @code{gud-gdb-command-name} to run the
25509 In the GUD buffer, you can use these special Emacs commands in
25510 addition to the standard Shell mode commands:
25514 Describe the features of Emacs' GUD Mode.
25517 Execute to another source line, like the @value{GDBN} @code{step} command; also
25518 update the display window to show the current file and location.
25521 Execute to next source line in this function, skipping all function
25522 calls, like the @value{GDBN} @code{next} command. Then update the display window
25523 to show the current file and location.
25526 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25527 display window accordingly.
25530 Execute until exit from the selected stack frame, like the @value{GDBN}
25531 @code{finish} command.
25534 Continue execution of your program, like the @value{GDBN} @code{continue}
25538 Go up the number of frames indicated by the numeric argument
25539 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25540 like the @value{GDBN} @code{up} command.
25543 Go down the number of frames indicated by the numeric argument, like the
25544 @value{GDBN} @code{down} command.
25547 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25548 tells @value{GDBN} to set a breakpoint on the source line point is on.
25550 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25551 separate frame which shows a backtrace when the GUD buffer is current.
25552 Move point to any frame in the stack and type @key{RET} to make it
25553 become the current frame and display the associated source in the
25554 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25555 selected frame become the current one. In graphical mode, the
25556 speedbar displays watch expressions.
25558 If you accidentally delete the source-display buffer, an easy way to get
25559 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25560 request a frame display; when you run under Emacs, this recreates
25561 the source buffer if necessary to show you the context of the current
25564 The source files displayed in Emacs are in ordinary Emacs buffers
25565 which are visiting the source files in the usual way. You can edit
25566 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25567 communicates with Emacs in terms of line numbers. If you add or
25568 delete lines from the text, the line numbers that @value{GDBN} knows cease
25569 to correspond properly with the code.
25571 A more detailed description of Emacs' interaction with @value{GDBN} is
25572 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25575 @c The following dropped because Epoch is nonstandard. Reactivate
25576 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25578 @kindex Emacs Epoch environment
25582 Version 18 of @sc{gnu} Emacs has a built-in window system
25583 called the @code{epoch}
25584 environment. Users of this environment can use a new command,
25585 @code{inspect} which performs identically to @code{print} except that
25586 each value is printed in its own window.
25591 @chapter The @sc{gdb/mi} Interface
25593 @unnumberedsec Function and Purpose
25595 @cindex @sc{gdb/mi}, its purpose
25596 @sc{gdb/mi} is a line based machine oriented text interface to
25597 @value{GDBN} and is activated by specifying using the
25598 @option{--interpreter} command line option (@pxref{Mode Options}). It
25599 is specifically intended to support the development of systems which
25600 use the debugger as just one small component of a larger system.
25602 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25603 in the form of a reference manual.
25605 Note that @sc{gdb/mi} is still under construction, so some of the
25606 features described below are incomplete and subject to change
25607 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25609 @unnumberedsec Notation and Terminology
25611 @cindex notational conventions, for @sc{gdb/mi}
25612 This chapter uses the following notation:
25616 @code{|} separates two alternatives.
25619 @code{[ @var{something} ]} indicates that @var{something} is optional:
25620 it may or may not be given.
25623 @code{( @var{group} )*} means that @var{group} inside the parentheses
25624 may repeat zero or more times.
25627 @code{( @var{group} )+} means that @var{group} inside the parentheses
25628 may repeat one or more times.
25631 @code{"@var{string}"} means a literal @var{string}.
25635 @heading Dependencies
25639 * GDB/MI General Design::
25640 * GDB/MI Command Syntax::
25641 * GDB/MI Compatibility with CLI::
25642 * GDB/MI Development and Front Ends::
25643 * GDB/MI Output Records::
25644 * GDB/MI Simple Examples::
25645 * GDB/MI Command Description Format::
25646 * GDB/MI Breakpoint Commands::
25647 * GDB/MI Program Context::
25648 * GDB/MI Thread Commands::
25649 * GDB/MI Ada Tasking Commands::
25650 * GDB/MI Program Execution::
25651 * GDB/MI Stack Manipulation::
25652 * GDB/MI Variable Objects::
25653 * GDB/MI Data Manipulation::
25654 * GDB/MI Tracepoint Commands::
25655 * GDB/MI Symbol Query::
25656 * GDB/MI File Commands::
25658 * GDB/MI Kod Commands::
25659 * GDB/MI Memory Overlay Commands::
25660 * GDB/MI Signal Handling Commands::
25662 * GDB/MI Target Manipulation::
25663 * GDB/MI File Transfer Commands::
25664 * GDB/MI Miscellaneous Commands::
25667 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25668 @node GDB/MI General Design
25669 @section @sc{gdb/mi} General Design
25670 @cindex GDB/MI General Design
25672 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25673 parts---commands sent to @value{GDBN}, responses to those commands
25674 and notifications. Each command results in exactly one response,
25675 indicating either successful completion of the command, or an error.
25676 For the commands that do not resume the target, the response contains the
25677 requested information. For the commands that resume the target, the
25678 response only indicates whether the target was successfully resumed.
25679 Notifications is the mechanism for reporting changes in the state of the
25680 target, or in @value{GDBN} state, that cannot conveniently be associated with
25681 a command and reported as part of that command response.
25683 The important examples of notifications are:
25687 Exec notifications. These are used to report changes in
25688 target state---when a target is resumed, or stopped. It would not
25689 be feasible to include this information in response of resuming
25690 commands, because one resume commands can result in multiple events in
25691 different threads. Also, quite some time may pass before any event
25692 happens in the target, while a frontend needs to know whether the resuming
25693 command itself was successfully executed.
25696 Console output, and status notifications. Console output
25697 notifications are used to report output of CLI commands, as well as
25698 diagnostics for other commands. Status notifications are used to
25699 report the progress of a long-running operation. Naturally, including
25700 this information in command response would mean no output is produced
25701 until the command is finished, which is undesirable.
25704 General notifications. Commands may have various side effects on
25705 the @value{GDBN} or target state beyond their official purpose. For example,
25706 a command may change the selected thread. Although such changes can
25707 be included in command response, using notification allows for more
25708 orthogonal frontend design.
25712 There's no guarantee that whenever an MI command reports an error,
25713 @value{GDBN} or the target are in any specific state, and especially,
25714 the state is not reverted to the state before the MI command was
25715 processed. Therefore, whenever an MI command results in an error,
25716 we recommend that the frontend refreshes all the information shown in
25717 the user interface.
25721 * Context management::
25722 * Asynchronous and non-stop modes::
25726 @node Context management
25727 @subsection Context management
25729 In most cases when @value{GDBN} accesses the target, this access is
25730 done in context of a specific thread and frame (@pxref{Frames}).
25731 Often, even when accessing global data, the target requires that a thread
25732 be specified. The CLI interface maintains the selected thread and frame,
25733 and supplies them to target on each command. This is convenient,
25734 because a command line user would not want to specify that information
25735 explicitly on each command, and because user interacts with
25736 @value{GDBN} via a single terminal, so no confusion is possible as
25737 to what thread and frame are the current ones.
25739 In the case of MI, the concept of selected thread and frame is less
25740 useful. First, a frontend can easily remember this information
25741 itself. Second, a graphical frontend can have more than one window,
25742 each one used for debugging a different thread, and the frontend might
25743 want to access additional threads for internal purposes. This
25744 increases the risk that by relying on implicitly selected thread, the
25745 frontend may be operating on a wrong one. Therefore, each MI command
25746 should explicitly specify which thread and frame to operate on. To
25747 make it possible, each MI command accepts the @samp{--thread} and
25748 @samp{--frame} options, the value to each is @value{GDBN} identifier
25749 for thread and frame to operate on.
25751 Usually, each top-level window in a frontend allows the user to select
25752 a thread and a frame, and remembers the user selection for further
25753 operations. However, in some cases @value{GDBN} may suggest that the
25754 current thread be changed. For example, when stopping on a breakpoint
25755 it is reasonable to switch to the thread where breakpoint is hit. For
25756 another example, if the user issues the CLI @samp{thread} command via
25757 the frontend, it is desirable to change the frontend's selected thread to the
25758 one specified by user. @value{GDBN} communicates the suggestion to
25759 change current thread using the @samp{=thread-selected} notification.
25760 No such notification is available for the selected frame at the moment.
25762 Note that historically, MI shares the selected thread with CLI, so
25763 frontends used the @code{-thread-select} to execute commands in the
25764 right context. However, getting this to work right is cumbersome. The
25765 simplest way is for frontend to emit @code{-thread-select} command
25766 before every command. This doubles the number of commands that need
25767 to be sent. The alternative approach is to suppress @code{-thread-select}
25768 if the selected thread in @value{GDBN} is supposed to be identical to the
25769 thread the frontend wants to operate on. However, getting this
25770 optimization right can be tricky. In particular, if the frontend
25771 sends several commands to @value{GDBN}, and one of the commands changes the
25772 selected thread, then the behaviour of subsequent commands will
25773 change. So, a frontend should either wait for response from such
25774 problematic commands, or explicitly add @code{-thread-select} for
25775 all subsequent commands. No frontend is known to do this exactly
25776 right, so it is suggested to just always pass the @samp{--thread} and
25777 @samp{--frame} options.
25779 @node Asynchronous and non-stop modes
25780 @subsection Asynchronous command execution and non-stop mode
25782 On some targets, @value{GDBN} is capable of processing MI commands
25783 even while the target is running. This is called @dfn{asynchronous
25784 command execution} (@pxref{Background Execution}). The frontend may
25785 specify a preferrence for asynchronous execution using the
25786 @code{-gdb-set target-async 1} command, which should be emitted before
25787 either running the executable or attaching to the target. After the
25788 frontend has started the executable or attached to the target, it can
25789 find if asynchronous execution is enabled using the
25790 @code{-list-target-features} command.
25792 Even if @value{GDBN} can accept a command while target is running,
25793 many commands that access the target do not work when the target is
25794 running. Therefore, asynchronous command execution is most useful
25795 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25796 it is possible to examine the state of one thread, while other threads
25799 When a given thread is running, MI commands that try to access the
25800 target in the context of that thread may not work, or may work only on
25801 some targets. In particular, commands that try to operate on thread's
25802 stack will not work, on any target. Commands that read memory, or
25803 modify breakpoints, may work or not work, depending on the target. Note
25804 that even commands that operate on global state, such as @code{print},
25805 @code{set}, and breakpoint commands, still access the target in the
25806 context of a specific thread, so frontend should try to find a
25807 stopped thread and perform the operation on that thread (using the
25808 @samp{--thread} option).
25810 Which commands will work in the context of a running thread is
25811 highly target dependent. However, the two commands
25812 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25813 to find the state of a thread, will always work.
25815 @node Thread groups
25816 @subsection Thread groups
25817 @value{GDBN} may be used to debug several processes at the same time.
25818 On some platfroms, @value{GDBN} may support debugging of several
25819 hardware systems, each one having several cores with several different
25820 processes running on each core. This section describes the MI
25821 mechanism to support such debugging scenarios.
25823 The key observation is that regardless of the structure of the
25824 target, MI can have a global list of threads, because most commands that
25825 accept the @samp{--thread} option do not need to know what process that
25826 thread belongs to. Therefore, it is not necessary to introduce
25827 neither additional @samp{--process} option, nor an notion of the
25828 current process in the MI interface. The only strictly new feature
25829 that is required is the ability to find how the threads are grouped
25832 To allow the user to discover such grouping, and to support arbitrary
25833 hierarchy of machines/cores/processes, MI introduces the concept of a
25834 @dfn{thread group}. Thread group is a collection of threads and other
25835 thread groups. A thread group always has a string identifier, a type,
25836 and may have additional attributes specific to the type. A new
25837 command, @code{-list-thread-groups}, returns the list of top-level
25838 thread groups, which correspond to processes that @value{GDBN} is
25839 debugging at the moment. By passing an identifier of a thread group
25840 to the @code{-list-thread-groups} command, it is possible to obtain
25841 the members of specific thread group.
25843 To allow the user to easily discover processes, and other objects, he
25844 wishes to debug, a concept of @dfn{available thread group} is
25845 introduced. Available thread group is an thread group that
25846 @value{GDBN} is not debugging, but that can be attached to, using the
25847 @code{-target-attach} command. The list of available top-level thread
25848 groups can be obtained using @samp{-list-thread-groups --available}.
25849 In general, the content of a thread group may be only retrieved only
25850 after attaching to that thread group.
25852 Thread groups are related to inferiors (@pxref{Inferiors and
25853 Programs}). Each inferior corresponds to a thread group of a special
25854 type @samp{process}, and some additional operations are permitted on
25855 such thread groups.
25857 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25858 @node GDB/MI Command Syntax
25859 @section @sc{gdb/mi} Command Syntax
25862 * GDB/MI Input Syntax::
25863 * GDB/MI Output Syntax::
25866 @node GDB/MI Input Syntax
25867 @subsection @sc{gdb/mi} Input Syntax
25869 @cindex input syntax for @sc{gdb/mi}
25870 @cindex @sc{gdb/mi}, input syntax
25872 @item @var{command} @expansion{}
25873 @code{@var{cli-command} | @var{mi-command}}
25875 @item @var{cli-command} @expansion{}
25876 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25877 @var{cli-command} is any existing @value{GDBN} CLI command.
25879 @item @var{mi-command} @expansion{}
25880 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25881 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25883 @item @var{token} @expansion{}
25884 "any sequence of digits"
25886 @item @var{option} @expansion{}
25887 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25889 @item @var{parameter} @expansion{}
25890 @code{@var{non-blank-sequence} | @var{c-string}}
25892 @item @var{operation} @expansion{}
25893 @emph{any of the operations described in this chapter}
25895 @item @var{non-blank-sequence} @expansion{}
25896 @emph{anything, provided it doesn't contain special characters such as
25897 "-", @var{nl}, """ and of course " "}
25899 @item @var{c-string} @expansion{}
25900 @code{""" @var{seven-bit-iso-c-string-content} """}
25902 @item @var{nl} @expansion{}
25911 The CLI commands are still handled by the @sc{mi} interpreter; their
25912 output is described below.
25915 The @code{@var{token}}, when present, is passed back when the command
25919 Some @sc{mi} commands accept optional arguments as part of the parameter
25920 list. Each option is identified by a leading @samp{-} (dash) and may be
25921 followed by an optional argument parameter. Options occur first in the
25922 parameter list and can be delimited from normal parameters using
25923 @samp{--} (this is useful when some parameters begin with a dash).
25930 We want easy access to the existing CLI syntax (for debugging).
25933 We want it to be easy to spot a @sc{mi} operation.
25936 @node GDB/MI Output Syntax
25937 @subsection @sc{gdb/mi} Output Syntax
25939 @cindex output syntax of @sc{gdb/mi}
25940 @cindex @sc{gdb/mi}, output syntax
25941 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25942 followed, optionally, by a single result record. This result record
25943 is for the most recent command. The sequence of output records is
25944 terminated by @samp{(gdb)}.
25946 If an input command was prefixed with a @code{@var{token}} then the
25947 corresponding output for that command will also be prefixed by that same
25951 @item @var{output} @expansion{}
25952 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25954 @item @var{result-record} @expansion{}
25955 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25957 @item @var{out-of-band-record} @expansion{}
25958 @code{@var{async-record} | @var{stream-record}}
25960 @item @var{async-record} @expansion{}
25961 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25963 @item @var{exec-async-output} @expansion{}
25964 @code{[ @var{token} ] "*" @var{async-output}}
25966 @item @var{status-async-output} @expansion{}
25967 @code{[ @var{token} ] "+" @var{async-output}}
25969 @item @var{notify-async-output} @expansion{}
25970 @code{[ @var{token} ] "=" @var{async-output}}
25972 @item @var{async-output} @expansion{}
25973 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25975 @item @var{result-class} @expansion{}
25976 @code{"done" | "running" | "connected" | "error" | "exit"}
25978 @item @var{async-class} @expansion{}
25979 @code{"stopped" | @var{others}} (where @var{others} will be added
25980 depending on the needs---this is still in development).
25982 @item @var{result} @expansion{}
25983 @code{ @var{variable} "=" @var{value}}
25985 @item @var{variable} @expansion{}
25986 @code{ @var{string} }
25988 @item @var{value} @expansion{}
25989 @code{ @var{const} | @var{tuple} | @var{list} }
25991 @item @var{const} @expansion{}
25992 @code{@var{c-string}}
25994 @item @var{tuple} @expansion{}
25995 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25997 @item @var{list} @expansion{}
25998 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25999 @var{result} ( "," @var{result} )* "]" }
26001 @item @var{stream-record} @expansion{}
26002 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26004 @item @var{console-stream-output} @expansion{}
26005 @code{"~" @var{c-string}}
26007 @item @var{target-stream-output} @expansion{}
26008 @code{"@@" @var{c-string}}
26010 @item @var{log-stream-output} @expansion{}
26011 @code{"&" @var{c-string}}
26013 @item @var{nl} @expansion{}
26016 @item @var{token} @expansion{}
26017 @emph{any sequence of digits}.
26025 All output sequences end in a single line containing a period.
26028 The @code{@var{token}} is from the corresponding request. Note that
26029 for all async output, while the token is allowed by the grammar and
26030 may be output by future versions of @value{GDBN} for select async
26031 output messages, it is generally omitted. Frontends should treat
26032 all async output as reporting general changes in the state of the
26033 target and there should be no need to associate async output to any
26037 @cindex status output in @sc{gdb/mi}
26038 @var{status-async-output} contains on-going status information about the
26039 progress of a slow operation. It can be discarded. All status output is
26040 prefixed by @samp{+}.
26043 @cindex async output in @sc{gdb/mi}
26044 @var{exec-async-output} contains asynchronous state change on the target
26045 (stopped, started, disappeared). All async output is prefixed by
26049 @cindex notify output in @sc{gdb/mi}
26050 @var{notify-async-output} contains supplementary information that the
26051 client should handle (e.g., a new breakpoint information). All notify
26052 output is prefixed by @samp{=}.
26055 @cindex console output in @sc{gdb/mi}
26056 @var{console-stream-output} is output that should be displayed as is in the
26057 console. It is the textual response to a CLI command. All the console
26058 output is prefixed by @samp{~}.
26061 @cindex target output in @sc{gdb/mi}
26062 @var{target-stream-output} is the output produced by the target program.
26063 All the target output is prefixed by @samp{@@}.
26066 @cindex log output in @sc{gdb/mi}
26067 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26068 instance messages that should be displayed as part of an error log. All
26069 the log output is prefixed by @samp{&}.
26072 @cindex list output in @sc{gdb/mi}
26073 New @sc{gdb/mi} commands should only output @var{lists} containing
26079 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26080 details about the various output records.
26082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26083 @node GDB/MI Compatibility with CLI
26084 @section @sc{gdb/mi} Compatibility with CLI
26086 @cindex compatibility, @sc{gdb/mi} and CLI
26087 @cindex @sc{gdb/mi}, compatibility with CLI
26089 For the developers convenience CLI commands can be entered directly,
26090 but there may be some unexpected behaviour. For example, commands
26091 that query the user will behave as if the user replied yes, breakpoint
26092 command lists are not executed and some CLI commands, such as
26093 @code{if}, @code{when} and @code{define}, prompt for further input with
26094 @samp{>}, which is not valid MI output.
26096 This feature may be removed at some stage in the future and it is
26097 recommended that front ends use the @code{-interpreter-exec} command
26098 (@pxref{-interpreter-exec}).
26100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26101 @node GDB/MI Development and Front Ends
26102 @section @sc{gdb/mi} Development and Front Ends
26103 @cindex @sc{gdb/mi} development
26105 The application which takes the MI output and presents the state of the
26106 program being debugged to the user is called a @dfn{front end}.
26108 Although @sc{gdb/mi} is still incomplete, it is currently being used
26109 by a variety of front ends to @value{GDBN}. This makes it difficult
26110 to introduce new functionality without breaking existing usage. This
26111 section tries to minimize the problems by describing how the protocol
26114 Some changes in MI need not break a carefully designed front end, and
26115 for these the MI version will remain unchanged. The following is a
26116 list of changes that may occur within one level, so front ends should
26117 parse MI output in a way that can handle them:
26121 New MI commands may be added.
26124 New fields may be added to the output of any MI command.
26127 The range of values for fields with specified values, e.g.,
26128 @code{in_scope} (@pxref{-var-update}) may be extended.
26130 @c The format of field's content e.g type prefix, may change so parse it
26131 @c at your own risk. Yes, in general?
26133 @c The order of fields may change? Shouldn't really matter but it might
26134 @c resolve inconsistencies.
26137 If the changes are likely to break front ends, the MI version level
26138 will be increased by one. This will allow the front end to parse the
26139 output according to the MI version. Apart from mi0, new versions of
26140 @value{GDBN} will not support old versions of MI and it will be the
26141 responsibility of the front end to work with the new one.
26143 @c Starting with mi3, add a new command -mi-version that prints the MI
26146 The best way to avoid unexpected changes in MI that might break your front
26147 end is to make your project known to @value{GDBN} developers and
26148 follow development on @email{gdb@@sourceware.org} and
26149 @email{gdb-patches@@sourceware.org}.
26150 @cindex mailing lists
26152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26153 @node GDB/MI Output Records
26154 @section @sc{gdb/mi} Output Records
26157 * GDB/MI Result Records::
26158 * GDB/MI Stream Records::
26159 * GDB/MI Async Records::
26160 * GDB/MI Frame Information::
26161 * GDB/MI Thread Information::
26162 * GDB/MI Ada Exception Information::
26165 @node GDB/MI Result Records
26166 @subsection @sc{gdb/mi} Result Records
26168 @cindex result records in @sc{gdb/mi}
26169 @cindex @sc{gdb/mi}, result records
26170 In addition to a number of out-of-band notifications, the response to a
26171 @sc{gdb/mi} command includes one of the following result indications:
26175 @item "^done" [ "," @var{results} ]
26176 The synchronous operation was successful, @code{@var{results}} are the return
26181 This result record is equivalent to @samp{^done}. Historically, it
26182 was output instead of @samp{^done} if the command has resumed the
26183 target. This behaviour is maintained for backward compatibility, but
26184 all frontends should treat @samp{^done} and @samp{^running}
26185 identically and rely on the @samp{*running} output record to determine
26186 which threads are resumed.
26190 @value{GDBN} has connected to a remote target.
26192 @item "^error" "," @var{c-string}
26194 The operation failed. The @code{@var{c-string}} contains the corresponding
26199 @value{GDBN} has terminated.
26203 @node GDB/MI Stream Records
26204 @subsection @sc{gdb/mi} Stream Records
26206 @cindex @sc{gdb/mi}, stream records
26207 @cindex stream records in @sc{gdb/mi}
26208 @value{GDBN} internally maintains a number of output streams: the console, the
26209 target, and the log. The output intended for each of these streams is
26210 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26212 Each stream record begins with a unique @dfn{prefix character} which
26213 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26214 Syntax}). In addition to the prefix, each stream record contains a
26215 @code{@var{string-output}}. This is either raw text (with an implicit new
26216 line) or a quoted C string (which does not contain an implicit newline).
26219 @item "~" @var{string-output}
26220 The console output stream contains text that should be displayed in the
26221 CLI console window. It contains the textual responses to CLI commands.
26223 @item "@@" @var{string-output}
26224 The target output stream contains any textual output from the running
26225 target. This is only present when GDB's event loop is truly
26226 asynchronous, which is currently only the case for remote targets.
26228 @item "&" @var{string-output}
26229 The log stream contains debugging messages being produced by @value{GDBN}'s
26233 @node GDB/MI Async Records
26234 @subsection @sc{gdb/mi} Async Records
26236 @cindex async records in @sc{gdb/mi}
26237 @cindex @sc{gdb/mi}, async records
26238 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26239 additional changes that have occurred. Those changes can either be a
26240 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26241 target activity (e.g., target stopped).
26243 The following is the list of possible async records:
26247 @item *running,thread-id="@var{thread}"
26248 The target is now running. The @var{thread} field tells which
26249 specific thread is now running, and can be @samp{all} if all threads
26250 are running. The frontend should assume that no interaction with a
26251 running thread is possible after this notification is produced.
26252 The frontend should not assume that this notification is output
26253 only once for any command. @value{GDBN} may emit this notification
26254 several times, either for different threads, because it cannot resume
26255 all threads together, or even for a single thread, if the thread must
26256 be stepped though some code before letting it run freely.
26258 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26259 The target has stopped. The @var{reason} field can have one of the
26263 @item breakpoint-hit
26264 A breakpoint was reached.
26265 @item watchpoint-trigger
26266 A watchpoint was triggered.
26267 @item read-watchpoint-trigger
26268 A read watchpoint was triggered.
26269 @item access-watchpoint-trigger
26270 An access watchpoint was triggered.
26271 @item function-finished
26272 An -exec-finish or similar CLI command was accomplished.
26273 @item location-reached
26274 An -exec-until or similar CLI command was accomplished.
26275 @item watchpoint-scope
26276 A watchpoint has gone out of scope.
26277 @item end-stepping-range
26278 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26279 similar CLI command was accomplished.
26280 @item exited-signalled
26281 The inferior exited because of a signal.
26283 The inferior exited.
26284 @item exited-normally
26285 The inferior exited normally.
26286 @item signal-received
26287 A signal was received by the inferior.
26289 The inferior has stopped due to a library being loaded or unloaded.
26290 This can only happen when @code{stop-on-solib-events} (@pxref{Files})
26293 The inferior has forked. This is reported when @code{catch fork}
26294 (@pxref{Set Catchpoints}) has been used.
26296 The inferior has vforked. This is reported in when @code{catch vfork}
26297 (@pxref{Set Catchpoints}) has been used.
26298 @item syscall-entry
26299 The inferior entered a system call. This is reported when @code{catch
26300 syscall} (@pxref{Set Catchpoints}) has been used.
26301 @item syscall-entry
26302 The inferior returned from a system call. This is reported when
26303 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26305 The inferior called @code{exec}. This is reported when @code{catch exec}
26306 (@pxref{Set Catchpoints}) has been used.
26309 The @var{id} field identifies the thread that directly caused the stop
26310 -- for example by hitting a breakpoint. Depending on whether all-stop
26311 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26312 stop all threads, or only the thread that directly triggered the stop.
26313 If all threads are stopped, the @var{stopped} field will have the
26314 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26315 field will be a list of thread identifiers. Presently, this list will
26316 always include a single thread, but frontend should be prepared to see
26317 several threads in the list. The @var{core} field reports the
26318 processor core on which the stop event has happened. This field may be absent
26319 if such information is not available.
26321 @item =thread-group-added,id="@var{id}"
26322 @itemx =thread-group-removed,id="@var{id}"
26323 A thread group was either added or removed. The @var{id} field
26324 contains the @value{GDBN} identifier of the thread group. When a thread
26325 group is added, it generally might not be associated with a running
26326 process. When a thread group is removed, its id becomes invalid and
26327 cannot be used in any way.
26329 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26330 A thread group became associated with a running program,
26331 either because the program was just started or the thread group
26332 was attached to a program. The @var{id} field contains the
26333 @value{GDBN} identifier of the thread group. The @var{pid} field
26334 contains process identifier, specific to the operating system.
26336 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26337 A thread group is no longer associated with a running program,
26338 either because the program has exited, or because it was detached
26339 from. The @var{id} field contains the @value{GDBN} identifier of the
26340 thread group. @var{code} is the exit code of the inferior; it exists
26341 only when the inferior exited with some code.
26343 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26344 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26345 A thread either was created, or has exited. The @var{id} field
26346 contains the @value{GDBN} identifier of the thread. The @var{gid}
26347 field identifies the thread group this thread belongs to.
26349 @item =thread-selected,id="@var{id}"
26350 Informs that the selected thread was changed as result of the last
26351 command. This notification is not emitted as result of @code{-thread-select}
26352 command but is emitted whenever an MI command that is not documented
26353 to change the selected thread actually changes it. In particular,
26354 invoking, directly or indirectly (via user-defined command), the CLI
26355 @code{thread} command, will generate this notification.
26357 We suggest that in response to this notification, front ends
26358 highlight the selected thread and cause subsequent commands to apply to
26361 @item =library-loaded,...
26362 Reports that a new library file was loaded by the program. This
26363 notification has 4 fields---@var{id}, @var{target-name},
26364 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26365 opaque identifier of the library. For remote debugging case,
26366 @var{target-name} and @var{host-name} fields give the name of the
26367 library file on the target, and on the host respectively. For native
26368 debugging, both those fields have the same value. The
26369 @var{symbols-loaded} field is emitted only for backward compatibility
26370 and should not be relied on to convey any useful information. The
26371 @var{thread-group} field, if present, specifies the id of the thread
26372 group in whose context the library was loaded. If the field is
26373 absent, it means the library was loaded in the context of all present
26376 @item =library-unloaded,...
26377 Reports that a library was unloaded by the program. This notification
26378 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26379 the same meaning as for the @code{=library-loaded} notification.
26380 The @var{thread-group} field, if present, specifies the id of the
26381 thread group in whose context the library was unloaded. If the field is
26382 absent, it means the library was unloaded in the context of all present
26385 @item =breakpoint-created,bkpt=@{...@}
26386 @itemx =breakpoint-modified,bkpt=@{...@}
26387 @itemx =breakpoint-deleted,bkpt=@{...@}
26388 Reports that a breakpoint was created, modified, or deleted,
26389 respectively. Only user-visible breakpoints are reported to the MI
26392 The @var{bkpt} argument is of the same form as returned by the various
26393 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26395 Note that if a breakpoint is emitted in the result record of a
26396 command, then it will not also be emitted in an async record.
26400 @node GDB/MI Frame Information
26401 @subsection @sc{gdb/mi} Frame Information
26403 Response from many MI commands includes an information about stack
26404 frame. This information is a tuple that may have the following
26409 The level of the stack frame. The innermost frame has the level of
26410 zero. This field is always present.
26413 The name of the function corresponding to the frame. This field may
26414 be absent if @value{GDBN} is unable to determine the function name.
26417 The code address for the frame. This field is always present.
26420 The name of the source files that correspond to the frame's code
26421 address. This field may be absent.
26424 The source line corresponding to the frames' code address. This field
26428 The name of the binary file (either executable or shared library) the
26429 corresponds to the frame's code address. This field may be absent.
26433 @node GDB/MI Thread Information
26434 @subsection @sc{gdb/mi} Thread Information
26436 Whenever @value{GDBN} has to report an information about a thread, it
26437 uses a tuple with the following fields:
26441 The numeric id assigned to the thread by @value{GDBN}. This field is
26445 Target-specific string identifying the thread. This field is always present.
26448 Additional information about the thread provided by the target.
26449 It is supposed to be human-readable and not interpreted by the
26450 frontend. This field is optional.
26453 Either @samp{stopped} or @samp{running}, depending on whether the
26454 thread is presently running. This field is always present.
26457 The value of this field is an integer number of the processor core the
26458 thread was last seen on. This field is optional.
26461 @node GDB/MI Ada Exception Information
26462 @subsection @sc{gdb/mi} Ada Exception Information
26464 Whenever a @code{*stopped} record is emitted because the program
26465 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26466 @value{GDBN} provides the name of the exception that was raised via
26467 the @code{exception-name} field.
26469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26470 @node GDB/MI Simple Examples
26471 @section Simple Examples of @sc{gdb/mi} Interaction
26472 @cindex @sc{gdb/mi}, simple examples
26474 This subsection presents several simple examples of interaction using
26475 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26476 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26477 the output received from @sc{gdb/mi}.
26479 Note the line breaks shown in the examples are here only for
26480 readability, they don't appear in the real output.
26482 @subheading Setting a Breakpoint
26484 Setting a breakpoint generates synchronous output which contains detailed
26485 information of the breakpoint.
26488 -> -break-insert main
26489 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26490 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26491 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26495 @subheading Program Execution
26497 Program execution generates asynchronous records and MI gives the
26498 reason that execution stopped.
26504 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26505 frame=@{addr="0x08048564",func="main",
26506 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26507 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26512 <- *stopped,reason="exited-normally"
26516 @subheading Quitting @value{GDBN}
26518 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26526 Please note that @samp{^exit} is printed immediately, but it might
26527 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26528 performs necessary cleanups, including killing programs being debugged
26529 or disconnecting from debug hardware, so the frontend should wait till
26530 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26531 fails to exit in reasonable time.
26533 @subheading A Bad Command
26535 Here's what happens if you pass a non-existent command:
26539 <- ^error,msg="Undefined MI command: rubbish"
26544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26545 @node GDB/MI Command Description Format
26546 @section @sc{gdb/mi} Command Description Format
26548 The remaining sections describe blocks of commands. Each block of
26549 commands is laid out in a fashion similar to this section.
26551 @subheading Motivation
26553 The motivation for this collection of commands.
26555 @subheading Introduction
26557 A brief introduction to this collection of commands as a whole.
26559 @subheading Commands
26561 For each command in the block, the following is described:
26563 @subsubheading Synopsis
26566 -command @var{args}@dots{}
26569 @subsubheading Result
26571 @subsubheading @value{GDBN} Command
26573 The corresponding @value{GDBN} CLI command(s), if any.
26575 @subsubheading Example
26577 Example(s) formatted for readability. Some of the described commands have
26578 not been implemented yet and these are labeled N.A.@: (not available).
26581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26582 @node GDB/MI Breakpoint Commands
26583 @section @sc{gdb/mi} Breakpoint Commands
26585 @cindex breakpoint commands for @sc{gdb/mi}
26586 @cindex @sc{gdb/mi}, breakpoint commands
26587 This section documents @sc{gdb/mi} commands for manipulating
26590 @subheading The @code{-break-after} Command
26591 @findex -break-after
26593 @subsubheading Synopsis
26596 -break-after @var{number} @var{count}
26599 The breakpoint number @var{number} is not in effect until it has been
26600 hit @var{count} times. To see how this is reflected in the output of
26601 the @samp{-break-list} command, see the description of the
26602 @samp{-break-list} command below.
26604 @subsubheading @value{GDBN} Command
26606 The corresponding @value{GDBN} command is @samp{ignore}.
26608 @subsubheading Example
26613 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26614 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26615 fullname="/home/foo/hello.c",line="5",times="0"@}
26622 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26623 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26624 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26625 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26626 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26627 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26628 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26629 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26630 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26631 line="5",times="0",ignore="3"@}]@}
26636 @subheading The @code{-break-catch} Command
26637 @findex -break-catch
26640 @subheading The @code{-break-commands} Command
26641 @findex -break-commands
26643 @subsubheading Synopsis
26646 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26649 Specifies the CLI commands that should be executed when breakpoint
26650 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26651 are the commands. If no command is specified, any previously-set
26652 commands are cleared. @xref{Break Commands}. Typical use of this
26653 functionality is tracing a program, that is, printing of values of
26654 some variables whenever breakpoint is hit and then continuing.
26656 @subsubheading @value{GDBN} Command
26658 The corresponding @value{GDBN} command is @samp{commands}.
26660 @subsubheading Example
26665 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26666 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26667 fullname="/home/foo/hello.c",line="5",times="0"@}
26669 -break-commands 1 "print v" "continue"
26674 @subheading The @code{-break-condition} Command
26675 @findex -break-condition
26677 @subsubheading Synopsis
26680 -break-condition @var{number} @var{expr}
26683 Breakpoint @var{number} will stop the program only if the condition in
26684 @var{expr} is true. The condition becomes part of the
26685 @samp{-break-list} output (see the description of the @samp{-break-list}
26688 @subsubheading @value{GDBN} Command
26690 The corresponding @value{GDBN} command is @samp{condition}.
26692 @subsubheading Example
26696 -break-condition 1 1
26700 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26701 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26702 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26703 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26704 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26705 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26706 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26707 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26708 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26709 line="5",cond="1",times="0",ignore="3"@}]@}
26713 @subheading The @code{-break-delete} Command
26714 @findex -break-delete
26716 @subsubheading Synopsis
26719 -break-delete ( @var{breakpoint} )+
26722 Delete the breakpoint(s) whose number(s) are specified in the argument
26723 list. This is obviously reflected in the breakpoint list.
26725 @subsubheading @value{GDBN} Command
26727 The corresponding @value{GDBN} command is @samp{delete}.
26729 @subsubheading Example
26737 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26738 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26739 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26740 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26741 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26742 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26743 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26748 @subheading The @code{-break-disable} Command
26749 @findex -break-disable
26751 @subsubheading Synopsis
26754 -break-disable ( @var{breakpoint} )+
26757 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26758 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26760 @subsubheading @value{GDBN} Command
26762 The corresponding @value{GDBN} command is @samp{disable}.
26764 @subsubheading Example
26772 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26773 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26774 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26775 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26776 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26777 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26778 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26779 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26780 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26781 line="5",times="0"@}]@}
26785 @subheading The @code{-break-enable} Command
26786 @findex -break-enable
26788 @subsubheading Synopsis
26791 -break-enable ( @var{breakpoint} )+
26794 Enable (previously disabled) @var{breakpoint}(s).
26796 @subsubheading @value{GDBN} Command
26798 The corresponding @value{GDBN} command is @samp{enable}.
26800 @subsubheading Example
26808 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26815 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26816 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26817 line="5",times="0"@}]@}
26821 @subheading The @code{-break-info} Command
26822 @findex -break-info
26824 @subsubheading Synopsis
26827 -break-info @var{breakpoint}
26831 Get information about a single breakpoint.
26833 @subsubheading @value{GDBN} Command
26835 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26837 @subsubheading Example
26840 @subheading The @code{-break-insert} Command
26841 @findex -break-insert
26843 @subsubheading Synopsis
26846 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26847 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26848 [ -p @var{thread} ] [ @var{location} ]
26852 If specified, @var{location}, can be one of:
26859 @item filename:linenum
26860 @item filename:function
26864 The possible optional parameters of this command are:
26868 Insert a temporary breakpoint.
26870 Insert a hardware breakpoint.
26871 @item -c @var{condition}
26872 Make the breakpoint conditional on @var{condition}.
26873 @item -i @var{ignore-count}
26874 Initialize the @var{ignore-count}.
26876 If @var{location} cannot be parsed (for example if it
26877 refers to unknown files or functions), create a pending
26878 breakpoint. Without this flag, @value{GDBN} will report
26879 an error, and won't create a breakpoint, if @var{location}
26882 Create a disabled breakpoint.
26884 Create a tracepoint. @xref{Tracepoints}. When this parameter
26885 is used together with @samp{-h}, a fast tracepoint is created.
26888 @subsubheading Result
26890 The result is in the form:
26893 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26894 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26895 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26896 times="@var{times}"@}
26900 where @var{number} is the @value{GDBN} number for this breakpoint,
26901 @var{funcname} is the name of the function where the breakpoint was
26902 inserted, @var{filename} is the name of the source file which contains
26903 this function, @var{lineno} is the source line number within that file
26904 and @var{times} the number of times that the breakpoint has been hit
26905 (always 0 for -break-insert but may be greater for -break-info or -break-list
26906 which use the same output).
26908 Note: this format is open to change.
26909 @c An out-of-band breakpoint instead of part of the result?
26911 @subsubheading @value{GDBN} Command
26913 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26914 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26916 @subsubheading Example
26921 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26922 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26924 -break-insert -t foo
26925 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26926 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26929 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26930 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26931 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26932 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26933 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26934 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26935 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26936 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26937 addr="0x0001072c", func="main",file="recursive2.c",
26938 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26939 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26940 addr="0x00010774",func="foo",file="recursive2.c",
26941 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26943 -break-insert -r foo.*
26944 ~int foo(int, int);
26945 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26946 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26950 @subheading The @code{-break-list} Command
26951 @findex -break-list
26953 @subsubheading Synopsis
26959 Displays the list of inserted breakpoints, showing the following fields:
26963 number of the breakpoint
26965 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26967 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26970 is the breakpoint enabled or no: @samp{y} or @samp{n}
26972 memory location at which the breakpoint is set
26974 logical location of the breakpoint, expressed by function name, file
26977 number of times the breakpoint has been hit
26980 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26981 @code{body} field is an empty list.
26983 @subsubheading @value{GDBN} Command
26985 The corresponding @value{GDBN} command is @samp{info break}.
26987 @subsubheading Example
26992 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26993 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26994 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26995 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26996 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26997 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26998 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26999 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27000 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27001 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27002 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27003 line="13",times="0"@}]@}
27007 Here's an example of the result when there are no breakpoints:
27012 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27013 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27014 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27015 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27016 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27017 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27018 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27023 @subheading The @code{-break-passcount} Command
27024 @findex -break-passcount
27026 @subsubheading Synopsis
27029 -break-passcount @var{tracepoint-number} @var{passcount}
27032 Set the passcount for tracepoint @var{tracepoint-number} to
27033 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27034 is not a tracepoint, error is emitted. This corresponds to CLI
27035 command @samp{passcount}.
27037 @subheading The @code{-break-watch} Command
27038 @findex -break-watch
27040 @subsubheading Synopsis
27043 -break-watch [ -a | -r ]
27046 Create a watchpoint. With the @samp{-a} option it will create an
27047 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27048 read from or on a write to the memory location. With the @samp{-r}
27049 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27050 trigger only when the memory location is accessed for reading. Without
27051 either of the options, the watchpoint created is a regular watchpoint,
27052 i.e., it will trigger when the memory location is accessed for writing.
27053 @xref{Set Watchpoints, , Setting Watchpoints}.
27055 Note that @samp{-break-list} will report a single list of watchpoints and
27056 breakpoints inserted.
27058 @subsubheading @value{GDBN} Command
27060 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27063 @subsubheading Example
27065 Setting a watchpoint on a variable in the @code{main} function:
27070 ^done,wpt=@{number="2",exp="x"@}
27075 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27076 value=@{old="-268439212",new="55"@},
27077 frame=@{func="main",args=[],file="recursive2.c",
27078 fullname="/home/foo/bar/recursive2.c",line="5"@}
27082 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27083 the program execution twice: first for the variable changing value, then
27084 for the watchpoint going out of scope.
27089 ^done,wpt=@{number="5",exp="C"@}
27094 *stopped,reason="watchpoint-trigger",
27095 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27096 frame=@{func="callee4",args=[],
27097 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27098 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27103 *stopped,reason="watchpoint-scope",wpnum="5",
27104 frame=@{func="callee3",args=[@{name="strarg",
27105 value="0x11940 \"A string argument.\""@}],
27106 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27107 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27111 Listing breakpoints and watchpoints, at different points in the program
27112 execution. Note that once the watchpoint goes out of scope, it is
27118 ^done,wpt=@{number="2",exp="C"@}
27121 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27122 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27123 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27124 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27125 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27126 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27127 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27128 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27129 addr="0x00010734",func="callee4",
27130 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27131 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27132 bkpt=@{number="2",type="watchpoint",disp="keep",
27133 enabled="y",addr="",what="C",times="0"@}]@}
27138 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27139 value=@{old="-276895068",new="3"@},
27140 frame=@{func="callee4",args=[],
27141 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27142 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27145 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27146 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27147 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27148 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27149 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27150 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27151 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27152 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27153 addr="0x00010734",func="callee4",
27154 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27155 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27156 bkpt=@{number="2",type="watchpoint",disp="keep",
27157 enabled="y",addr="",what="C",times="-5"@}]@}
27161 ^done,reason="watchpoint-scope",wpnum="2",
27162 frame=@{func="callee3",args=[@{name="strarg",
27163 value="0x11940 \"A string argument.\""@}],
27164 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27165 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27168 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27169 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27170 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27171 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27172 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27173 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27174 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27175 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27176 addr="0x00010734",func="callee4",
27177 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27178 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27183 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27184 @node GDB/MI Program Context
27185 @section @sc{gdb/mi} Program Context
27187 @subheading The @code{-exec-arguments} Command
27188 @findex -exec-arguments
27191 @subsubheading Synopsis
27194 -exec-arguments @var{args}
27197 Set the inferior program arguments, to be used in the next
27200 @subsubheading @value{GDBN} Command
27202 The corresponding @value{GDBN} command is @samp{set args}.
27204 @subsubheading Example
27208 -exec-arguments -v word
27215 @subheading The @code{-exec-show-arguments} Command
27216 @findex -exec-show-arguments
27218 @subsubheading Synopsis
27221 -exec-show-arguments
27224 Print the arguments of the program.
27226 @subsubheading @value{GDBN} Command
27228 The corresponding @value{GDBN} command is @samp{show args}.
27230 @subsubheading Example
27235 @subheading The @code{-environment-cd} Command
27236 @findex -environment-cd
27238 @subsubheading Synopsis
27241 -environment-cd @var{pathdir}
27244 Set @value{GDBN}'s working directory.
27246 @subsubheading @value{GDBN} Command
27248 The corresponding @value{GDBN} command is @samp{cd}.
27250 @subsubheading Example
27254 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27260 @subheading The @code{-environment-directory} Command
27261 @findex -environment-directory
27263 @subsubheading Synopsis
27266 -environment-directory [ -r ] [ @var{pathdir} ]+
27269 Add directories @var{pathdir} to beginning of search path for source files.
27270 If the @samp{-r} option is used, the search path is reset to the default
27271 search path. If directories @var{pathdir} are supplied in addition to the
27272 @samp{-r} option, the search path is first reset and then addition
27274 Multiple directories may be specified, separated by blanks. Specifying
27275 multiple directories in a single command
27276 results in the directories added to the beginning of the
27277 search path in the same order they were presented in the command.
27278 If blanks are needed as
27279 part of a directory name, double-quotes should be used around
27280 the name. In the command output, the path will show up separated
27281 by the system directory-separator character. The directory-separator
27282 character must not be used
27283 in any directory name.
27284 If no directories are specified, the current search path is displayed.
27286 @subsubheading @value{GDBN} Command
27288 The corresponding @value{GDBN} command is @samp{dir}.
27290 @subsubheading Example
27294 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27295 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27297 -environment-directory ""
27298 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27300 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27301 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27303 -environment-directory -r
27304 ^done,source-path="$cdir:$cwd"
27309 @subheading The @code{-environment-path} Command
27310 @findex -environment-path
27312 @subsubheading Synopsis
27315 -environment-path [ -r ] [ @var{pathdir} ]+
27318 Add directories @var{pathdir} to beginning of search path for object files.
27319 If the @samp{-r} option is used, the search path is reset to the original
27320 search path that existed at gdb start-up. If directories @var{pathdir} are
27321 supplied in addition to the
27322 @samp{-r} option, the search path is first reset and then addition
27324 Multiple directories may be specified, separated by blanks. Specifying
27325 multiple directories in a single command
27326 results in the directories added to the beginning of the
27327 search path in the same order they were presented in the command.
27328 If blanks are needed as
27329 part of a directory name, double-quotes should be used around
27330 the name. In the command output, the path will show up separated
27331 by the system directory-separator character. The directory-separator
27332 character must not be used
27333 in any directory name.
27334 If no directories are specified, the current path is displayed.
27337 @subsubheading @value{GDBN} Command
27339 The corresponding @value{GDBN} command is @samp{path}.
27341 @subsubheading Example
27346 ^done,path="/usr/bin"
27348 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27349 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27351 -environment-path -r /usr/local/bin
27352 ^done,path="/usr/local/bin:/usr/bin"
27357 @subheading The @code{-environment-pwd} Command
27358 @findex -environment-pwd
27360 @subsubheading Synopsis
27366 Show the current working directory.
27368 @subsubheading @value{GDBN} Command
27370 The corresponding @value{GDBN} command is @samp{pwd}.
27372 @subsubheading Example
27377 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27381 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27382 @node GDB/MI Thread Commands
27383 @section @sc{gdb/mi} Thread Commands
27386 @subheading The @code{-thread-info} Command
27387 @findex -thread-info
27389 @subsubheading Synopsis
27392 -thread-info [ @var{thread-id} ]
27395 Reports information about either a specific thread, if
27396 the @var{thread-id} parameter is present, or about all
27397 threads. When printing information about all threads,
27398 also reports the current thread.
27400 @subsubheading @value{GDBN} Command
27402 The @samp{info thread} command prints the same information
27405 @subsubheading Result
27407 The result is a list of threads. The following attributes are
27408 defined for a given thread:
27412 This field exists only for the current thread. It has the value @samp{*}.
27415 The identifier that @value{GDBN} uses to refer to the thread.
27418 The identifier that the target uses to refer to the thread.
27421 Extra information about the thread, in a target-specific format. This
27425 The name of the thread. If the user specified a name using the
27426 @code{thread name} command, then this name is given. Otherwise, if
27427 @value{GDBN} can extract the thread name from the target, then that
27428 name is given. If @value{GDBN} cannot find the thread name, then this
27432 The stack frame currently executing in the thread.
27435 The thread's state. The @samp{state} field may have the following
27440 The thread is stopped. Frame information is available for stopped
27444 The thread is running. There's no frame information for running
27450 If @value{GDBN} can find the CPU core on which this thread is running,
27451 then this field is the core identifier. This field is optional.
27455 @subsubheading Example
27460 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27461 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27462 args=[]@},state="running"@},
27463 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27464 frame=@{level="0",addr="0x0804891f",func="foo",
27465 args=[@{name="i",value="10"@}],
27466 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27467 state="running"@}],
27468 current-thread-id="1"
27472 @subheading The @code{-thread-list-ids} Command
27473 @findex -thread-list-ids
27475 @subsubheading Synopsis
27481 Produces a list of the currently known @value{GDBN} thread ids. At the
27482 end of the list it also prints the total number of such threads.
27484 This command is retained for historical reasons, the
27485 @code{-thread-info} command should be used instead.
27487 @subsubheading @value{GDBN} Command
27489 Part of @samp{info threads} supplies the same information.
27491 @subsubheading Example
27496 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27497 current-thread-id="1",number-of-threads="3"
27502 @subheading The @code{-thread-select} Command
27503 @findex -thread-select
27505 @subsubheading Synopsis
27508 -thread-select @var{threadnum}
27511 Make @var{threadnum} the current thread. It prints the number of the new
27512 current thread, and the topmost frame for that thread.
27514 This command is deprecated in favor of explicitly using the
27515 @samp{--thread} option to each command.
27517 @subsubheading @value{GDBN} Command
27519 The corresponding @value{GDBN} command is @samp{thread}.
27521 @subsubheading Example
27528 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27529 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27533 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27534 number-of-threads="3"
27537 ^done,new-thread-id="3",
27538 frame=@{level="0",func="vprintf",
27539 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27540 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27545 @node GDB/MI Ada Tasking Commands
27546 @section @sc{gdb/mi} Ada Tasking Commands
27548 @subheading The @code{-ada-task-info} Command
27549 @findex -ada-task-info
27551 @subsubheading Synopsis
27554 -ada-task-info [ @var{task-id} ]
27557 Reports information about either a specific Ada task, if the
27558 @var{task-id} parameter is present, or about all Ada tasks.
27560 @subsubheading @value{GDBN} Command
27562 The @samp{info tasks} command prints the same information
27563 about all Ada tasks (@pxref{Ada Tasks}).
27565 @subsubheading Result
27567 The result is a table of Ada tasks. The following columns are
27568 defined for each Ada task:
27572 This field exists only for the current thread. It has the value @samp{*}.
27575 The identifier that @value{GDBN} uses to refer to the Ada task.
27578 The identifier that the target uses to refer to the Ada task.
27581 The identifier of the thread corresponding to the Ada task.
27583 This field should always exist, as Ada tasks are always implemented
27584 on top of a thread. But if @value{GDBN} cannot find this corresponding
27585 thread for any reason, the field is omitted.
27588 This field exists only when the task was created by another task.
27589 In this case, it provides the ID of the parent task.
27592 The base priority of the task.
27595 The current state of the task. For a detailed description of the
27596 possible states, see @ref{Ada Tasks}.
27599 The name of the task.
27603 @subsubheading Example
27607 ^done,tasks=@{nr_rows="3",nr_cols="8",
27608 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27609 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27610 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27611 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27612 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27613 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27614 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27615 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27616 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27617 state="Child Termination Wait",name="main_task"@}]@}
27621 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27622 @node GDB/MI Program Execution
27623 @section @sc{gdb/mi} Program Execution
27625 These are the asynchronous commands which generate the out-of-band
27626 record @samp{*stopped}. Currently @value{GDBN} only really executes
27627 asynchronously with remote targets and this interaction is mimicked in
27630 @subheading The @code{-exec-continue} Command
27631 @findex -exec-continue
27633 @subsubheading Synopsis
27636 -exec-continue [--reverse] [--all|--thread-group N]
27639 Resumes the execution of the inferior program, which will continue
27640 to execute until it reaches a debugger stop event. If the
27641 @samp{--reverse} option is specified, execution resumes in reverse until
27642 it reaches a stop event. Stop events may include
27645 breakpoints or watchpoints
27647 signals or exceptions
27649 the end of the process (or its beginning under @samp{--reverse})
27651 the end or beginning of a replay log if one is being used.
27653 In all-stop mode (@pxref{All-Stop
27654 Mode}), may resume only one thread, or all threads, depending on the
27655 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27656 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27657 ignored in all-stop mode. If the @samp{--thread-group} options is
27658 specified, then all threads in that thread group are resumed.
27660 @subsubheading @value{GDBN} Command
27662 The corresponding @value{GDBN} corresponding is @samp{continue}.
27664 @subsubheading Example
27671 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27672 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27678 @subheading The @code{-exec-finish} Command
27679 @findex -exec-finish
27681 @subsubheading Synopsis
27684 -exec-finish [--reverse]
27687 Resumes the execution of the inferior program until the current
27688 function is exited. Displays the results returned by the function.
27689 If the @samp{--reverse} option is specified, resumes the reverse
27690 execution of the inferior program until the point where current
27691 function was called.
27693 @subsubheading @value{GDBN} Command
27695 The corresponding @value{GDBN} command is @samp{finish}.
27697 @subsubheading Example
27699 Function returning @code{void}.
27706 *stopped,reason="function-finished",frame=@{func="main",args=[],
27707 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27711 Function returning other than @code{void}. The name of the internal
27712 @value{GDBN} variable storing the result is printed, together with the
27719 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27720 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27721 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27722 gdb-result-var="$1",return-value="0"
27727 @subheading The @code{-exec-interrupt} Command
27728 @findex -exec-interrupt
27730 @subsubheading Synopsis
27733 -exec-interrupt [--all|--thread-group N]
27736 Interrupts the background execution of the target. Note how the token
27737 associated with the stop message is the one for the execution command
27738 that has been interrupted. The token for the interrupt itself only
27739 appears in the @samp{^done} output. If the user is trying to
27740 interrupt a non-running program, an error message will be printed.
27742 Note that when asynchronous execution is enabled, this command is
27743 asynchronous just like other execution commands. That is, first the
27744 @samp{^done} response will be printed, and the target stop will be
27745 reported after that using the @samp{*stopped} notification.
27747 In non-stop mode, only the context thread is interrupted by default.
27748 All threads (in all inferiors) will be interrupted if the
27749 @samp{--all} option is specified. If the @samp{--thread-group}
27750 option is specified, all threads in that group will be interrupted.
27752 @subsubheading @value{GDBN} Command
27754 The corresponding @value{GDBN} command is @samp{interrupt}.
27756 @subsubheading Example
27767 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27768 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27769 fullname="/home/foo/bar/try.c",line="13"@}
27774 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27778 @subheading The @code{-exec-jump} Command
27781 @subsubheading Synopsis
27784 -exec-jump @var{location}
27787 Resumes execution of the inferior program at the location specified by
27788 parameter. @xref{Specify Location}, for a description of the
27789 different forms of @var{location}.
27791 @subsubheading @value{GDBN} Command
27793 The corresponding @value{GDBN} command is @samp{jump}.
27795 @subsubheading Example
27798 -exec-jump foo.c:10
27799 *running,thread-id="all"
27804 @subheading The @code{-exec-next} Command
27807 @subsubheading Synopsis
27810 -exec-next [--reverse]
27813 Resumes execution of the inferior program, stopping when the beginning
27814 of the next source line is reached.
27816 If the @samp{--reverse} option is specified, resumes reverse execution
27817 of the inferior program, stopping at the beginning of the previous
27818 source line. If you issue this command on the first line of a
27819 function, it will take you back to the caller of that function, to the
27820 source line where the function was called.
27823 @subsubheading @value{GDBN} Command
27825 The corresponding @value{GDBN} command is @samp{next}.
27827 @subsubheading Example
27833 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27838 @subheading The @code{-exec-next-instruction} Command
27839 @findex -exec-next-instruction
27841 @subsubheading Synopsis
27844 -exec-next-instruction [--reverse]
27847 Executes one machine instruction. If the instruction is a function
27848 call, continues until the function returns. If the program stops at an
27849 instruction in the middle of a source line, the address will be
27852 If the @samp{--reverse} option is specified, resumes reverse execution
27853 of the inferior program, stopping at the previous instruction. If the
27854 previously executed instruction was a return from another function,
27855 it will continue to execute in reverse until the call to that function
27856 (from the current stack frame) is reached.
27858 @subsubheading @value{GDBN} Command
27860 The corresponding @value{GDBN} command is @samp{nexti}.
27862 @subsubheading Example
27866 -exec-next-instruction
27870 *stopped,reason="end-stepping-range",
27871 addr="0x000100d4",line="5",file="hello.c"
27876 @subheading The @code{-exec-return} Command
27877 @findex -exec-return
27879 @subsubheading Synopsis
27885 Makes current function return immediately. Doesn't execute the inferior.
27886 Displays the new current frame.
27888 @subsubheading @value{GDBN} Command
27890 The corresponding @value{GDBN} command is @samp{return}.
27892 @subsubheading Example
27896 200-break-insert callee4
27897 200^done,bkpt=@{number="1",addr="0x00010734",
27898 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27903 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27904 frame=@{func="callee4",args=[],
27905 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27906 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27912 111^done,frame=@{level="0",func="callee3",
27913 args=[@{name="strarg",
27914 value="0x11940 \"A string argument.\""@}],
27915 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27916 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27921 @subheading The @code{-exec-run} Command
27924 @subsubheading Synopsis
27927 -exec-run [--all | --thread-group N]
27930 Starts execution of the inferior from the beginning. The inferior
27931 executes until either a breakpoint is encountered or the program
27932 exits. In the latter case the output will include an exit code, if
27933 the program has exited exceptionally.
27935 When no option is specified, the current inferior is started. If the
27936 @samp{--thread-group} option is specified, it should refer to a thread
27937 group of type @samp{process}, and that thread group will be started.
27938 If the @samp{--all} option is specified, then all inferiors will be started.
27940 @subsubheading @value{GDBN} Command
27942 The corresponding @value{GDBN} command is @samp{run}.
27944 @subsubheading Examples
27949 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27954 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27955 frame=@{func="main",args=[],file="recursive2.c",
27956 fullname="/home/foo/bar/recursive2.c",line="4"@}
27961 Program exited normally:
27969 *stopped,reason="exited-normally"
27974 Program exited exceptionally:
27982 *stopped,reason="exited",exit-code="01"
27986 Another way the program can terminate is if it receives a signal such as
27987 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27991 *stopped,reason="exited-signalled",signal-name="SIGINT",
27992 signal-meaning="Interrupt"
27996 @c @subheading -exec-signal
27999 @subheading The @code{-exec-step} Command
28002 @subsubheading Synopsis
28005 -exec-step [--reverse]
28008 Resumes execution of the inferior program, stopping when the beginning
28009 of the next source line is reached, if the next source line is not a
28010 function call. If it is, stop at the first instruction of the called
28011 function. If the @samp{--reverse} option is specified, resumes reverse
28012 execution of the inferior program, stopping at the beginning of the
28013 previously executed source line.
28015 @subsubheading @value{GDBN} Command
28017 The corresponding @value{GDBN} command is @samp{step}.
28019 @subsubheading Example
28021 Stepping into a function:
28027 *stopped,reason="end-stepping-range",
28028 frame=@{func="foo",args=[@{name="a",value="10"@},
28029 @{name="b",value="0"@}],file="recursive2.c",
28030 fullname="/home/foo/bar/recursive2.c",line="11"@}
28040 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28045 @subheading The @code{-exec-step-instruction} Command
28046 @findex -exec-step-instruction
28048 @subsubheading Synopsis
28051 -exec-step-instruction [--reverse]
28054 Resumes the inferior which executes one machine instruction. If the
28055 @samp{--reverse} option is specified, resumes reverse execution of the
28056 inferior program, stopping at the previously executed instruction.
28057 The output, once @value{GDBN} has stopped, will vary depending on
28058 whether we have stopped in the middle of a source line or not. In the
28059 former case, the address at which the program stopped will be printed
28062 @subsubheading @value{GDBN} Command
28064 The corresponding @value{GDBN} command is @samp{stepi}.
28066 @subsubheading Example
28070 -exec-step-instruction
28074 *stopped,reason="end-stepping-range",
28075 frame=@{func="foo",args=[],file="try.c",
28076 fullname="/home/foo/bar/try.c",line="10"@}
28078 -exec-step-instruction
28082 *stopped,reason="end-stepping-range",
28083 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28084 fullname="/home/foo/bar/try.c",line="10"@}
28089 @subheading The @code{-exec-until} Command
28090 @findex -exec-until
28092 @subsubheading Synopsis
28095 -exec-until [ @var{location} ]
28098 Executes the inferior until the @var{location} specified in the
28099 argument is reached. If there is no argument, the inferior executes
28100 until a source line greater than the current one is reached. The
28101 reason for stopping in this case will be @samp{location-reached}.
28103 @subsubheading @value{GDBN} Command
28105 The corresponding @value{GDBN} command is @samp{until}.
28107 @subsubheading Example
28111 -exec-until recursive2.c:6
28115 *stopped,reason="location-reached",frame=@{func="main",args=[],
28116 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28121 @subheading -file-clear
28122 Is this going away????
28125 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28126 @node GDB/MI Stack Manipulation
28127 @section @sc{gdb/mi} Stack Manipulation Commands
28130 @subheading The @code{-stack-info-frame} Command
28131 @findex -stack-info-frame
28133 @subsubheading Synopsis
28139 Get info on the selected frame.
28141 @subsubheading @value{GDBN} Command
28143 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28144 (without arguments).
28146 @subsubheading Example
28151 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28152 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28153 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28157 @subheading The @code{-stack-info-depth} Command
28158 @findex -stack-info-depth
28160 @subsubheading Synopsis
28163 -stack-info-depth [ @var{max-depth} ]
28166 Return the depth of the stack. If the integer argument @var{max-depth}
28167 is specified, do not count beyond @var{max-depth} frames.
28169 @subsubheading @value{GDBN} Command
28171 There's no equivalent @value{GDBN} command.
28173 @subsubheading Example
28175 For a stack with frame levels 0 through 11:
28182 -stack-info-depth 4
28185 -stack-info-depth 12
28188 -stack-info-depth 11
28191 -stack-info-depth 13
28196 @subheading The @code{-stack-list-arguments} Command
28197 @findex -stack-list-arguments
28199 @subsubheading Synopsis
28202 -stack-list-arguments @var{print-values}
28203 [ @var{low-frame} @var{high-frame} ]
28206 Display a list of the arguments for the frames between @var{low-frame}
28207 and @var{high-frame} (inclusive). If @var{low-frame} and
28208 @var{high-frame} are not provided, list the arguments for the whole
28209 call stack. If the two arguments are equal, show the single frame
28210 at the corresponding level. It is an error if @var{low-frame} is
28211 larger than the actual number of frames. On the other hand,
28212 @var{high-frame} may be larger than the actual number of frames, in
28213 which case only existing frames will be returned.
28215 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28216 the variables; if it is 1 or @code{--all-values}, print also their
28217 values; and if it is 2 or @code{--simple-values}, print the name,
28218 type and value for simple data types, and the name and type for arrays,
28219 structures and unions.
28221 Use of this command to obtain arguments in a single frame is
28222 deprecated in favor of the @samp{-stack-list-variables} command.
28224 @subsubheading @value{GDBN} Command
28226 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28227 @samp{gdb_get_args} command which partially overlaps with the
28228 functionality of @samp{-stack-list-arguments}.
28230 @subsubheading Example
28237 frame=@{level="0",addr="0x00010734",func="callee4",
28238 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28239 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28240 frame=@{level="1",addr="0x0001076c",func="callee3",
28241 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28242 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28243 frame=@{level="2",addr="0x0001078c",func="callee2",
28244 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28245 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28246 frame=@{level="3",addr="0x000107b4",func="callee1",
28247 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28248 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28249 frame=@{level="4",addr="0x000107e0",func="main",
28250 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28251 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28253 -stack-list-arguments 0
28256 frame=@{level="0",args=[]@},
28257 frame=@{level="1",args=[name="strarg"]@},
28258 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28259 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28260 frame=@{level="4",args=[]@}]
28262 -stack-list-arguments 1
28265 frame=@{level="0",args=[]@},
28267 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28268 frame=@{level="2",args=[
28269 @{name="intarg",value="2"@},
28270 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28271 @{frame=@{level="3",args=[
28272 @{name="intarg",value="2"@},
28273 @{name="strarg",value="0x11940 \"A string argument.\""@},
28274 @{name="fltarg",value="3.5"@}]@},
28275 frame=@{level="4",args=[]@}]
28277 -stack-list-arguments 0 2 2
28278 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28280 -stack-list-arguments 1 2 2
28281 ^done,stack-args=[frame=@{level="2",
28282 args=[@{name="intarg",value="2"@},
28283 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28287 @c @subheading -stack-list-exception-handlers
28290 @subheading The @code{-stack-list-frames} Command
28291 @findex -stack-list-frames
28293 @subsubheading Synopsis
28296 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28299 List the frames currently on the stack. For each frame it displays the
28304 The frame number, 0 being the topmost frame, i.e., the innermost function.
28306 The @code{$pc} value for that frame.
28310 File name of the source file where the function lives.
28311 @item @var{fullname}
28312 The full file name of the source file where the function lives.
28314 Line number corresponding to the @code{$pc}.
28316 The shared library where this function is defined. This is only given
28317 if the frame's function is not known.
28320 If invoked without arguments, this command prints a backtrace for the
28321 whole stack. If given two integer arguments, it shows the frames whose
28322 levels are between the two arguments (inclusive). If the two arguments
28323 are equal, it shows the single frame at the corresponding level. It is
28324 an error if @var{low-frame} is larger than the actual number of
28325 frames. On the other hand, @var{high-frame} may be larger than the
28326 actual number of frames, in which case only existing frames will be returned.
28328 @subsubheading @value{GDBN} Command
28330 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28332 @subsubheading Example
28334 Full stack backtrace:
28340 [frame=@{level="0",addr="0x0001076c",func="foo",
28341 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28342 frame=@{level="1",addr="0x000107a4",func="foo",
28343 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28344 frame=@{level="2",addr="0x000107a4",func="foo",
28345 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28346 frame=@{level="3",addr="0x000107a4",func="foo",
28347 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28348 frame=@{level="4",addr="0x000107a4",func="foo",
28349 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28350 frame=@{level="5",addr="0x000107a4",func="foo",
28351 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28352 frame=@{level="6",addr="0x000107a4",func="foo",
28353 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28354 frame=@{level="7",addr="0x000107a4",func="foo",
28355 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28356 frame=@{level="8",addr="0x000107a4",func="foo",
28357 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28358 frame=@{level="9",addr="0x000107a4",func="foo",
28359 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28360 frame=@{level="10",addr="0x000107a4",func="foo",
28361 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28362 frame=@{level="11",addr="0x00010738",func="main",
28363 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28367 Show frames between @var{low_frame} and @var{high_frame}:
28371 -stack-list-frames 3 5
28373 [frame=@{level="3",addr="0x000107a4",func="foo",
28374 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28375 frame=@{level="4",addr="0x000107a4",func="foo",
28376 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28377 frame=@{level="5",addr="0x000107a4",func="foo",
28378 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28382 Show a single frame:
28386 -stack-list-frames 3 3
28388 [frame=@{level="3",addr="0x000107a4",func="foo",
28389 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28394 @subheading The @code{-stack-list-locals} Command
28395 @findex -stack-list-locals
28397 @subsubheading Synopsis
28400 -stack-list-locals @var{print-values}
28403 Display the local variable names for the selected frame. If
28404 @var{print-values} is 0 or @code{--no-values}, print only the names of
28405 the variables; if it is 1 or @code{--all-values}, print also their
28406 values; and if it is 2 or @code{--simple-values}, print the name,
28407 type and value for simple data types, and the name and type for arrays,
28408 structures and unions. In this last case, a frontend can immediately
28409 display the value of simple data types and create variable objects for
28410 other data types when the user wishes to explore their values in
28413 This command is deprecated in favor of the
28414 @samp{-stack-list-variables} command.
28416 @subsubheading @value{GDBN} Command
28418 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28420 @subsubheading Example
28424 -stack-list-locals 0
28425 ^done,locals=[name="A",name="B",name="C"]
28427 -stack-list-locals --all-values
28428 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28429 @{name="C",value="@{1, 2, 3@}"@}]
28430 -stack-list-locals --simple-values
28431 ^done,locals=[@{name="A",type="int",value="1"@},
28432 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28436 @subheading The @code{-stack-list-variables} Command
28437 @findex -stack-list-variables
28439 @subsubheading Synopsis
28442 -stack-list-variables @var{print-values}
28445 Display the names of local variables and function arguments for the selected frame. If
28446 @var{print-values} is 0 or @code{--no-values}, print only the names of
28447 the variables; if it is 1 or @code{--all-values}, print also their
28448 values; and if it is 2 or @code{--simple-values}, print the name,
28449 type and value for simple data types, and the name and type for arrays,
28450 structures and unions.
28452 @subsubheading Example
28456 -stack-list-variables --thread 1 --frame 0 --all-values
28457 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28462 @subheading The @code{-stack-select-frame} Command
28463 @findex -stack-select-frame
28465 @subsubheading Synopsis
28468 -stack-select-frame @var{framenum}
28471 Change the selected frame. Select a different frame @var{framenum} on
28474 This command in deprecated in favor of passing the @samp{--frame}
28475 option to every command.
28477 @subsubheading @value{GDBN} Command
28479 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28480 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28482 @subsubheading Example
28486 -stack-select-frame 2
28491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28492 @node GDB/MI Variable Objects
28493 @section @sc{gdb/mi} Variable Objects
28497 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28499 For the implementation of a variable debugger window (locals, watched
28500 expressions, etc.), we are proposing the adaptation of the existing code
28501 used by @code{Insight}.
28503 The two main reasons for that are:
28507 It has been proven in practice (it is already on its second generation).
28510 It will shorten development time (needless to say how important it is
28514 The original interface was designed to be used by Tcl code, so it was
28515 slightly changed so it could be used through @sc{gdb/mi}. This section
28516 describes the @sc{gdb/mi} operations that will be available and gives some
28517 hints about their use.
28519 @emph{Note}: In addition to the set of operations described here, we
28520 expect the @sc{gui} implementation of a variable window to require, at
28521 least, the following operations:
28524 @item @code{-gdb-show} @code{output-radix}
28525 @item @code{-stack-list-arguments}
28526 @item @code{-stack-list-locals}
28527 @item @code{-stack-select-frame}
28532 @subheading Introduction to Variable Objects
28534 @cindex variable objects in @sc{gdb/mi}
28536 Variable objects are "object-oriented" MI interface for examining and
28537 changing values of expressions. Unlike some other MI interfaces that
28538 work with expressions, variable objects are specifically designed for
28539 simple and efficient presentation in the frontend. A variable object
28540 is identified by string name. When a variable object is created, the
28541 frontend specifies the expression for that variable object. The
28542 expression can be a simple variable, or it can be an arbitrary complex
28543 expression, and can even involve CPU registers. After creating a
28544 variable object, the frontend can invoke other variable object
28545 operations---for example to obtain or change the value of a variable
28546 object, or to change display format.
28548 Variable objects have hierarchical tree structure. Any variable object
28549 that corresponds to a composite type, such as structure in C, has
28550 a number of child variable objects, for example corresponding to each
28551 element of a structure. A child variable object can itself have
28552 children, recursively. Recursion ends when we reach
28553 leaf variable objects, which always have built-in types. Child variable
28554 objects are created only by explicit request, so if a frontend
28555 is not interested in the children of a particular variable object, no
28556 child will be created.
28558 For a leaf variable object it is possible to obtain its value as a
28559 string, or set the value from a string. String value can be also
28560 obtained for a non-leaf variable object, but it's generally a string
28561 that only indicates the type of the object, and does not list its
28562 contents. Assignment to a non-leaf variable object is not allowed.
28564 A frontend does not need to read the values of all variable objects each time
28565 the program stops. Instead, MI provides an update command that lists all
28566 variable objects whose values has changed since the last update
28567 operation. This considerably reduces the amount of data that must
28568 be transferred to the frontend. As noted above, children variable
28569 objects are created on demand, and only leaf variable objects have a
28570 real value. As result, gdb will read target memory only for leaf
28571 variables that frontend has created.
28573 The automatic update is not always desirable. For example, a frontend
28574 might want to keep a value of some expression for future reference,
28575 and never update it. For another example, fetching memory is
28576 relatively slow for embedded targets, so a frontend might want
28577 to disable automatic update for the variables that are either not
28578 visible on the screen, or ``closed''. This is possible using so
28579 called ``frozen variable objects''. Such variable objects are never
28580 implicitly updated.
28582 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28583 fixed variable object, the expression is parsed when the variable
28584 object is created, including associating identifiers to specific
28585 variables. The meaning of expression never changes. For a floating
28586 variable object the values of variables whose names appear in the
28587 expressions are re-evaluated every time in the context of the current
28588 frame. Consider this example:
28593 struct work_state state;
28600 If a fixed variable object for the @code{state} variable is created in
28601 this function, and we enter the recursive call, the variable
28602 object will report the value of @code{state} in the top-level
28603 @code{do_work} invocation. On the other hand, a floating variable
28604 object will report the value of @code{state} in the current frame.
28606 If an expression specified when creating a fixed variable object
28607 refers to a local variable, the variable object becomes bound to the
28608 thread and frame in which the variable object is created. When such
28609 variable object is updated, @value{GDBN} makes sure that the
28610 thread/frame combination the variable object is bound to still exists,
28611 and re-evaluates the variable object in context of that thread/frame.
28613 The following is the complete set of @sc{gdb/mi} operations defined to
28614 access this functionality:
28616 @multitable @columnfractions .4 .6
28617 @item @strong{Operation}
28618 @tab @strong{Description}
28620 @item @code{-enable-pretty-printing}
28621 @tab enable Python-based pretty-printing
28622 @item @code{-var-create}
28623 @tab create a variable object
28624 @item @code{-var-delete}
28625 @tab delete the variable object and/or its children
28626 @item @code{-var-set-format}
28627 @tab set the display format of this variable
28628 @item @code{-var-show-format}
28629 @tab show the display format of this variable
28630 @item @code{-var-info-num-children}
28631 @tab tells how many children this object has
28632 @item @code{-var-list-children}
28633 @tab return a list of the object's children
28634 @item @code{-var-info-type}
28635 @tab show the type of this variable object
28636 @item @code{-var-info-expression}
28637 @tab print parent-relative expression that this variable object represents
28638 @item @code{-var-info-path-expression}
28639 @tab print full expression that this variable object represents
28640 @item @code{-var-show-attributes}
28641 @tab is this variable editable? does it exist here?
28642 @item @code{-var-evaluate-expression}
28643 @tab get the value of this variable
28644 @item @code{-var-assign}
28645 @tab set the value of this variable
28646 @item @code{-var-update}
28647 @tab update the variable and its children
28648 @item @code{-var-set-frozen}
28649 @tab set frozeness attribute
28650 @item @code{-var-set-update-range}
28651 @tab set range of children to display on update
28654 In the next subsection we describe each operation in detail and suggest
28655 how it can be used.
28657 @subheading Description And Use of Operations on Variable Objects
28659 @subheading The @code{-enable-pretty-printing} Command
28660 @findex -enable-pretty-printing
28663 -enable-pretty-printing
28666 @value{GDBN} allows Python-based visualizers to affect the output of the
28667 MI variable object commands. However, because there was no way to
28668 implement this in a fully backward-compatible way, a front end must
28669 request that this functionality be enabled.
28671 Once enabled, this feature cannot be disabled.
28673 Note that if Python support has not been compiled into @value{GDBN},
28674 this command will still succeed (and do nothing).
28676 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28677 may work differently in future versions of @value{GDBN}.
28679 @subheading The @code{-var-create} Command
28680 @findex -var-create
28682 @subsubheading Synopsis
28685 -var-create @{@var{name} | "-"@}
28686 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28689 This operation creates a variable object, which allows the monitoring of
28690 a variable, the result of an expression, a memory cell or a CPU
28693 The @var{name} parameter is the string by which the object can be
28694 referenced. It must be unique. If @samp{-} is specified, the varobj
28695 system will generate a string ``varNNNNNN'' automatically. It will be
28696 unique provided that one does not specify @var{name} of that format.
28697 The command fails if a duplicate name is found.
28699 The frame under which the expression should be evaluated can be
28700 specified by @var{frame-addr}. A @samp{*} indicates that the current
28701 frame should be used. A @samp{@@} indicates that a floating variable
28702 object must be created.
28704 @var{expression} is any expression valid on the current language set (must not
28705 begin with a @samp{*}), or one of the following:
28709 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28712 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28715 @samp{$@var{regname}} --- a CPU register name
28718 @cindex dynamic varobj
28719 A varobj's contents may be provided by a Python-based pretty-printer. In this
28720 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28721 have slightly different semantics in some cases. If the
28722 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28723 will never create a dynamic varobj. This ensures backward
28724 compatibility for existing clients.
28726 @subsubheading Result
28728 This operation returns attributes of the newly-created varobj. These
28733 The name of the varobj.
28736 The number of children of the varobj. This number is not necessarily
28737 reliable for a dynamic varobj. Instead, you must examine the
28738 @samp{has_more} attribute.
28741 The varobj's scalar value. For a varobj whose type is some sort of
28742 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28743 will not be interesting.
28746 The varobj's type. This is a string representation of the type, as
28747 would be printed by the @value{GDBN} CLI.
28750 If a variable object is bound to a specific thread, then this is the
28751 thread's identifier.
28754 For a dynamic varobj, this indicates whether there appear to be any
28755 children available. For a non-dynamic varobj, this will be 0.
28758 This attribute will be present and have the value @samp{1} if the
28759 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28760 then this attribute will not be present.
28763 A dynamic varobj can supply a display hint to the front end. The
28764 value comes directly from the Python pretty-printer object's
28765 @code{display_hint} method. @xref{Pretty Printing API}.
28768 Typical output will look like this:
28771 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28772 has_more="@var{has_more}"
28776 @subheading The @code{-var-delete} Command
28777 @findex -var-delete
28779 @subsubheading Synopsis
28782 -var-delete [ -c ] @var{name}
28785 Deletes a previously created variable object and all of its children.
28786 With the @samp{-c} option, just deletes the children.
28788 Returns an error if the object @var{name} is not found.
28791 @subheading The @code{-var-set-format} Command
28792 @findex -var-set-format
28794 @subsubheading Synopsis
28797 -var-set-format @var{name} @var{format-spec}
28800 Sets the output format for the value of the object @var{name} to be
28803 @anchor{-var-set-format}
28804 The syntax for the @var{format-spec} is as follows:
28807 @var{format-spec} @expansion{}
28808 @{binary | decimal | hexadecimal | octal | natural@}
28811 The natural format is the default format choosen automatically
28812 based on the variable type (like decimal for an @code{int}, hex
28813 for pointers, etc.).
28815 For a variable with children, the format is set only on the
28816 variable itself, and the children are not affected.
28818 @subheading The @code{-var-show-format} Command
28819 @findex -var-show-format
28821 @subsubheading Synopsis
28824 -var-show-format @var{name}
28827 Returns the format used to display the value of the object @var{name}.
28830 @var{format} @expansion{}
28835 @subheading The @code{-var-info-num-children} Command
28836 @findex -var-info-num-children
28838 @subsubheading Synopsis
28841 -var-info-num-children @var{name}
28844 Returns the number of children of a variable object @var{name}:
28850 Note that this number is not completely reliable for a dynamic varobj.
28851 It will return the current number of children, but more children may
28855 @subheading The @code{-var-list-children} Command
28856 @findex -var-list-children
28858 @subsubheading Synopsis
28861 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28863 @anchor{-var-list-children}
28865 Return a list of the children of the specified variable object and
28866 create variable objects for them, if they do not already exist. With
28867 a single argument or if @var{print-values} has a value of 0 or
28868 @code{--no-values}, print only the names of the variables; if
28869 @var{print-values} is 1 or @code{--all-values}, also print their
28870 values; and if it is 2 or @code{--simple-values} print the name and
28871 value for simple data types and just the name for arrays, structures
28874 @var{from} and @var{to}, if specified, indicate the range of children
28875 to report. If @var{from} or @var{to} is less than zero, the range is
28876 reset and all children will be reported. Otherwise, children starting
28877 at @var{from} (zero-based) and up to and excluding @var{to} will be
28880 If a child range is requested, it will only affect the current call to
28881 @code{-var-list-children}, but not future calls to @code{-var-update}.
28882 For this, you must instead use @code{-var-set-update-range}. The
28883 intent of this approach is to enable a front end to implement any
28884 update approach it likes; for example, scrolling a view may cause the
28885 front end to request more children with @code{-var-list-children}, and
28886 then the front end could call @code{-var-set-update-range} with a
28887 different range to ensure that future updates are restricted to just
28890 For each child the following results are returned:
28895 Name of the variable object created for this child.
28898 The expression to be shown to the user by the front end to designate this child.
28899 For example this may be the name of a structure member.
28901 For a dynamic varobj, this value cannot be used to form an
28902 expression. There is no way to do this at all with a dynamic varobj.
28904 For C/C@t{++} structures there are several pseudo children returned to
28905 designate access qualifiers. For these pseudo children @var{exp} is
28906 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28907 type and value are not present.
28909 A dynamic varobj will not report the access qualifying
28910 pseudo-children, regardless of the language. This information is not
28911 available at all with a dynamic varobj.
28914 Number of children this child has. For a dynamic varobj, this will be
28918 The type of the child.
28921 If values were requested, this is the value.
28924 If this variable object is associated with a thread, this is the thread id.
28925 Otherwise this result is not present.
28928 If the variable object is frozen, this variable will be present with a value of 1.
28931 The result may have its own attributes:
28935 A dynamic varobj can supply a display hint to the front end. The
28936 value comes directly from the Python pretty-printer object's
28937 @code{display_hint} method. @xref{Pretty Printing API}.
28940 This is an integer attribute which is nonzero if there are children
28941 remaining after the end of the selected range.
28944 @subsubheading Example
28948 -var-list-children n
28949 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28950 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28952 -var-list-children --all-values n
28953 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28954 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28958 @subheading The @code{-var-info-type} Command
28959 @findex -var-info-type
28961 @subsubheading Synopsis
28964 -var-info-type @var{name}
28967 Returns the type of the specified variable @var{name}. The type is
28968 returned as a string in the same format as it is output by the
28972 type=@var{typename}
28976 @subheading The @code{-var-info-expression} Command
28977 @findex -var-info-expression
28979 @subsubheading Synopsis
28982 -var-info-expression @var{name}
28985 Returns a string that is suitable for presenting this
28986 variable object in user interface. The string is generally
28987 not valid expression in the current language, and cannot be evaluated.
28989 For example, if @code{a} is an array, and variable object
28990 @code{A} was created for @code{a}, then we'll get this output:
28993 (gdb) -var-info-expression A.1
28994 ^done,lang="C",exp="1"
28998 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29000 Note that the output of the @code{-var-list-children} command also
29001 includes those expressions, so the @code{-var-info-expression} command
29004 @subheading The @code{-var-info-path-expression} Command
29005 @findex -var-info-path-expression
29007 @subsubheading Synopsis
29010 -var-info-path-expression @var{name}
29013 Returns an expression that can be evaluated in the current
29014 context and will yield the same value that a variable object has.
29015 Compare this with the @code{-var-info-expression} command, which
29016 result can be used only for UI presentation. Typical use of
29017 the @code{-var-info-path-expression} command is creating a
29018 watchpoint from a variable object.
29020 This command is currently not valid for children of a dynamic varobj,
29021 and will give an error when invoked on one.
29023 For example, suppose @code{C} is a C@t{++} class, derived from class
29024 @code{Base}, and that the @code{Base} class has a member called
29025 @code{m_size}. Assume a variable @code{c} is has the type of
29026 @code{C} and a variable object @code{C} was created for variable
29027 @code{c}. Then, we'll get this output:
29029 (gdb) -var-info-path-expression C.Base.public.m_size
29030 ^done,path_expr=((Base)c).m_size)
29033 @subheading The @code{-var-show-attributes} Command
29034 @findex -var-show-attributes
29036 @subsubheading Synopsis
29039 -var-show-attributes @var{name}
29042 List attributes of the specified variable object @var{name}:
29045 status=@var{attr} [ ( ,@var{attr} )* ]
29049 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29051 @subheading The @code{-var-evaluate-expression} Command
29052 @findex -var-evaluate-expression
29054 @subsubheading Synopsis
29057 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29060 Evaluates the expression that is represented by the specified variable
29061 object and returns its value as a string. The format of the string
29062 can be specified with the @samp{-f} option. The possible values of
29063 this option are the same as for @code{-var-set-format}
29064 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29065 the current display format will be used. The current display format
29066 can be changed using the @code{-var-set-format} command.
29072 Note that one must invoke @code{-var-list-children} for a variable
29073 before the value of a child variable can be evaluated.
29075 @subheading The @code{-var-assign} Command
29076 @findex -var-assign
29078 @subsubheading Synopsis
29081 -var-assign @var{name} @var{expression}
29084 Assigns the value of @var{expression} to the variable object specified
29085 by @var{name}. The object must be @samp{editable}. If the variable's
29086 value is altered by the assign, the variable will show up in any
29087 subsequent @code{-var-update} list.
29089 @subsubheading Example
29097 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29101 @subheading The @code{-var-update} Command
29102 @findex -var-update
29104 @subsubheading Synopsis
29107 -var-update [@var{print-values}] @{@var{name} | "*"@}
29110 Reevaluate the expressions corresponding to the variable object
29111 @var{name} and all its direct and indirect children, and return the
29112 list of variable objects whose values have changed; @var{name} must
29113 be a root variable object. Here, ``changed'' means that the result of
29114 @code{-var-evaluate-expression} before and after the
29115 @code{-var-update} is different. If @samp{*} is used as the variable
29116 object names, all existing variable objects are updated, except
29117 for frozen ones (@pxref{-var-set-frozen}). The option
29118 @var{print-values} determines whether both names and values, or just
29119 names are printed. The possible values of this option are the same
29120 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29121 recommended to use the @samp{--all-values} option, to reduce the
29122 number of MI commands needed on each program stop.
29124 With the @samp{*} parameter, if a variable object is bound to a
29125 currently running thread, it will not be updated, without any
29128 If @code{-var-set-update-range} was previously used on a varobj, then
29129 only the selected range of children will be reported.
29131 @code{-var-update} reports all the changed varobjs in a tuple named
29134 Each item in the change list is itself a tuple holding:
29138 The name of the varobj.
29141 If values were requested for this update, then this field will be
29142 present and will hold the value of the varobj.
29145 @anchor{-var-update}
29146 This field is a string which may take one of three values:
29150 The variable object's current value is valid.
29153 The variable object does not currently hold a valid value but it may
29154 hold one in the future if its associated expression comes back into
29158 The variable object no longer holds a valid value.
29159 This can occur when the executable file being debugged has changed,
29160 either through recompilation or by using the @value{GDBN} @code{file}
29161 command. The front end should normally choose to delete these variable
29165 In the future new values may be added to this list so the front should
29166 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29169 This is only present if the varobj is still valid. If the type
29170 changed, then this will be the string @samp{true}; otherwise it will
29174 If the varobj's type changed, then this field will be present and will
29177 @item new_num_children
29178 For a dynamic varobj, if the number of children changed, or if the
29179 type changed, this will be the new number of children.
29181 The @samp{numchild} field in other varobj responses is generally not
29182 valid for a dynamic varobj -- it will show the number of children that
29183 @value{GDBN} knows about, but because dynamic varobjs lazily
29184 instantiate their children, this will not reflect the number of
29185 children which may be available.
29187 The @samp{new_num_children} attribute only reports changes to the
29188 number of children known by @value{GDBN}. This is the only way to
29189 detect whether an update has removed children (which necessarily can
29190 only happen at the end of the update range).
29193 The display hint, if any.
29196 This is an integer value, which will be 1 if there are more children
29197 available outside the varobj's update range.
29200 This attribute will be present and have the value @samp{1} if the
29201 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29202 then this attribute will not be present.
29205 If new children were added to a dynamic varobj within the selected
29206 update range (as set by @code{-var-set-update-range}), then they will
29207 be listed in this attribute.
29210 @subsubheading Example
29217 -var-update --all-values var1
29218 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29219 type_changed="false"@}]
29223 @subheading The @code{-var-set-frozen} Command
29224 @findex -var-set-frozen
29225 @anchor{-var-set-frozen}
29227 @subsubheading Synopsis
29230 -var-set-frozen @var{name} @var{flag}
29233 Set the frozenness flag on the variable object @var{name}. The
29234 @var{flag} parameter should be either @samp{1} to make the variable
29235 frozen or @samp{0} to make it unfrozen. If a variable object is
29236 frozen, then neither itself, nor any of its children, are
29237 implicitly updated by @code{-var-update} of
29238 a parent variable or by @code{-var-update *}. Only
29239 @code{-var-update} of the variable itself will update its value and
29240 values of its children. After a variable object is unfrozen, it is
29241 implicitly updated by all subsequent @code{-var-update} operations.
29242 Unfreezing a variable does not update it, only subsequent
29243 @code{-var-update} does.
29245 @subsubheading Example
29249 -var-set-frozen V 1
29254 @subheading The @code{-var-set-update-range} command
29255 @findex -var-set-update-range
29256 @anchor{-var-set-update-range}
29258 @subsubheading Synopsis
29261 -var-set-update-range @var{name} @var{from} @var{to}
29264 Set the range of children to be returned by future invocations of
29265 @code{-var-update}.
29267 @var{from} and @var{to} indicate the range of children to report. If
29268 @var{from} or @var{to} is less than zero, the range is reset and all
29269 children will be reported. Otherwise, children starting at @var{from}
29270 (zero-based) and up to and excluding @var{to} will be reported.
29272 @subsubheading Example
29276 -var-set-update-range V 1 2
29280 @subheading The @code{-var-set-visualizer} command
29281 @findex -var-set-visualizer
29282 @anchor{-var-set-visualizer}
29284 @subsubheading Synopsis
29287 -var-set-visualizer @var{name} @var{visualizer}
29290 Set a visualizer for the variable object @var{name}.
29292 @var{visualizer} is the visualizer to use. The special value
29293 @samp{None} means to disable any visualizer in use.
29295 If not @samp{None}, @var{visualizer} must be a Python expression.
29296 This expression must evaluate to a callable object which accepts a
29297 single argument. @value{GDBN} will call this object with the value of
29298 the varobj @var{name} as an argument (this is done so that the same
29299 Python pretty-printing code can be used for both the CLI and MI).
29300 When called, this object must return an object which conforms to the
29301 pretty-printing interface (@pxref{Pretty Printing API}).
29303 The pre-defined function @code{gdb.default_visualizer} may be used to
29304 select a visualizer by following the built-in process
29305 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29306 a varobj is created, and so ordinarily is not needed.
29308 This feature is only available if Python support is enabled. The MI
29309 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29310 can be used to check this.
29312 @subsubheading Example
29314 Resetting the visualizer:
29318 -var-set-visualizer V None
29322 Reselecting the default (type-based) visualizer:
29326 -var-set-visualizer V gdb.default_visualizer
29330 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29331 can be used to instantiate this class for a varobj:
29335 -var-set-visualizer V "lambda val: SomeClass()"
29339 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29340 @node GDB/MI Data Manipulation
29341 @section @sc{gdb/mi} Data Manipulation
29343 @cindex data manipulation, in @sc{gdb/mi}
29344 @cindex @sc{gdb/mi}, data manipulation
29345 This section describes the @sc{gdb/mi} commands that manipulate data:
29346 examine memory and registers, evaluate expressions, etc.
29348 @c REMOVED FROM THE INTERFACE.
29349 @c @subheading -data-assign
29350 @c Change the value of a program variable. Plenty of side effects.
29351 @c @subsubheading GDB Command
29353 @c @subsubheading Example
29356 @subheading The @code{-data-disassemble} Command
29357 @findex -data-disassemble
29359 @subsubheading Synopsis
29363 [ -s @var{start-addr} -e @var{end-addr} ]
29364 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29372 @item @var{start-addr}
29373 is the beginning address (or @code{$pc})
29374 @item @var{end-addr}
29376 @item @var{filename}
29377 is the name of the file to disassemble
29378 @item @var{linenum}
29379 is the line number to disassemble around
29381 is the number of disassembly lines to be produced. If it is -1,
29382 the whole function will be disassembled, in case no @var{end-addr} is
29383 specified. If @var{end-addr} is specified as a non-zero value, and
29384 @var{lines} is lower than the number of disassembly lines between
29385 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29386 displayed; if @var{lines} is higher than the number of lines between
29387 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29390 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29391 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29392 mixed source and disassembly with raw opcodes).
29395 @subsubheading Result
29397 The output for each instruction is composed of four fields:
29406 Note that whatever included in the instruction field, is not manipulated
29407 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29409 @subsubheading @value{GDBN} Command
29411 There's no direct mapping from this command to the CLI.
29413 @subsubheading Example
29415 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29419 -data-disassemble -s $pc -e "$pc + 20" -- 0
29422 @{address="0x000107c0",func-name="main",offset="4",
29423 inst="mov 2, %o0"@},
29424 @{address="0x000107c4",func-name="main",offset="8",
29425 inst="sethi %hi(0x11800), %o2"@},
29426 @{address="0x000107c8",func-name="main",offset="12",
29427 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29428 @{address="0x000107cc",func-name="main",offset="16",
29429 inst="sethi %hi(0x11800), %o2"@},
29430 @{address="0x000107d0",func-name="main",offset="20",
29431 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29435 Disassemble the whole @code{main} function. Line 32 is part of
29439 -data-disassemble -f basics.c -l 32 -- 0
29441 @{address="0x000107bc",func-name="main",offset="0",
29442 inst="save %sp, -112, %sp"@},
29443 @{address="0x000107c0",func-name="main",offset="4",
29444 inst="mov 2, %o0"@},
29445 @{address="0x000107c4",func-name="main",offset="8",
29446 inst="sethi %hi(0x11800), %o2"@},
29448 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29449 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29453 Disassemble 3 instructions from the start of @code{main}:
29457 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29459 @{address="0x000107bc",func-name="main",offset="0",
29460 inst="save %sp, -112, %sp"@},
29461 @{address="0x000107c0",func-name="main",offset="4",
29462 inst="mov 2, %o0"@},
29463 @{address="0x000107c4",func-name="main",offset="8",
29464 inst="sethi %hi(0x11800), %o2"@}]
29468 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29472 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29474 src_and_asm_line=@{line="31",
29475 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29476 testsuite/gdb.mi/basics.c",line_asm_insn=[
29477 @{address="0x000107bc",func-name="main",offset="0",
29478 inst="save %sp, -112, %sp"@}]@},
29479 src_and_asm_line=@{line="32",
29480 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29481 testsuite/gdb.mi/basics.c",line_asm_insn=[
29482 @{address="0x000107c0",func-name="main",offset="4",
29483 inst="mov 2, %o0"@},
29484 @{address="0x000107c4",func-name="main",offset="8",
29485 inst="sethi %hi(0x11800), %o2"@}]@}]
29490 @subheading The @code{-data-evaluate-expression} Command
29491 @findex -data-evaluate-expression
29493 @subsubheading Synopsis
29496 -data-evaluate-expression @var{expr}
29499 Evaluate @var{expr} as an expression. The expression could contain an
29500 inferior function call. The function call will execute synchronously.
29501 If the expression contains spaces, it must be enclosed in double quotes.
29503 @subsubheading @value{GDBN} Command
29505 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29506 @samp{call}. In @code{gdbtk} only, there's a corresponding
29507 @samp{gdb_eval} command.
29509 @subsubheading Example
29511 In the following example, the numbers that precede the commands are the
29512 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29513 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29517 211-data-evaluate-expression A
29520 311-data-evaluate-expression &A
29521 311^done,value="0xefffeb7c"
29523 411-data-evaluate-expression A+3
29526 511-data-evaluate-expression "A + 3"
29532 @subheading The @code{-data-list-changed-registers} Command
29533 @findex -data-list-changed-registers
29535 @subsubheading Synopsis
29538 -data-list-changed-registers
29541 Display a list of the registers that have changed.
29543 @subsubheading @value{GDBN} Command
29545 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29546 has the corresponding command @samp{gdb_changed_register_list}.
29548 @subsubheading Example
29550 On a PPC MBX board:
29558 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29559 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29562 -data-list-changed-registers
29563 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29564 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29565 "24","25","26","27","28","30","31","64","65","66","67","69"]
29570 @subheading The @code{-data-list-register-names} Command
29571 @findex -data-list-register-names
29573 @subsubheading Synopsis
29576 -data-list-register-names [ ( @var{regno} )+ ]
29579 Show a list of register names for the current target. If no arguments
29580 are given, it shows a list of the names of all the registers. If
29581 integer numbers are given as arguments, it will print a list of the
29582 names of the registers corresponding to the arguments. To ensure
29583 consistency between a register name and its number, the output list may
29584 include empty register names.
29586 @subsubheading @value{GDBN} Command
29588 @value{GDBN} does not have a command which corresponds to
29589 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29590 corresponding command @samp{gdb_regnames}.
29592 @subsubheading Example
29594 For the PPC MBX board:
29597 -data-list-register-names
29598 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29599 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29600 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29601 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29602 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29603 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29604 "", "pc","ps","cr","lr","ctr","xer"]
29606 -data-list-register-names 1 2 3
29607 ^done,register-names=["r1","r2","r3"]
29611 @subheading The @code{-data-list-register-values} Command
29612 @findex -data-list-register-values
29614 @subsubheading Synopsis
29617 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29620 Display the registers' contents. @var{fmt} is the format according to
29621 which the registers' contents are to be returned, followed by an optional
29622 list of numbers specifying the registers to display. A missing list of
29623 numbers indicates that the contents of all the registers must be returned.
29625 Allowed formats for @var{fmt} are:
29642 @subsubheading @value{GDBN} Command
29644 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29645 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29647 @subsubheading Example
29649 For a PPC MBX board (note: line breaks are for readability only, they
29650 don't appear in the actual output):
29654 -data-list-register-values r 64 65
29655 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29656 @{number="65",value="0x00029002"@}]
29658 -data-list-register-values x
29659 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29660 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29661 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29662 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29663 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29664 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29665 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29666 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29667 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29668 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29669 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29670 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29671 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29672 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29673 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29674 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29675 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29676 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29677 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29678 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29679 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29680 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29681 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29682 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29683 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29684 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29685 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29686 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29687 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29688 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29689 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29690 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29691 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29692 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29693 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29694 @{number="69",value="0x20002b03"@}]
29699 @subheading The @code{-data-read-memory} Command
29700 @findex -data-read-memory
29702 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29704 @subsubheading Synopsis
29707 -data-read-memory [ -o @var{byte-offset} ]
29708 @var{address} @var{word-format} @var{word-size}
29709 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29716 @item @var{address}
29717 An expression specifying the address of the first memory word to be
29718 read. Complex expressions containing embedded white space should be
29719 quoted using the C convention.
29721 @item @var{word-format}
29722 The format to be used to print the memory words. The notation is the
29723 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29726 @item @var{word-size}
29727 The size of each memory word in bytes.
29729 @item @var{nr-rows}
29730 The number of rows in the output table.
29732 @item @var{nr-cols}
29733 The number of columns in the output table.
29736 If present, indicates that each row should include an @sc{ascii} dump. The
29737 value of @var{aschar} is used as a padding character when a byte is not a
29738 member of the printable @sc{ascii} character set (printable @sc{ascii}
29739 characters are those whose code is between 32 and 126, inclusively).
29741 @item @var{byte-offset}
29742 An offset to add to the @var{address} before fetching memory.
29745 This command displays memory contents as a table of @var{nr-rows} by
29746 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29747 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29748 (returned as @samp{total-bytes}). Should less than the requested number
29749 of bytes be returned by the target, the missing words are identified
29750 using @samp{N/A}. The number of bytes read from the target is returned
29751 in @samp{nr-bytes} and the starting address used to read memory in
29754 The address of the next/previous row or page is available in
29755 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29758 @subsubheading @value{GDBN} Command
29760 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29761 @samp{gdb_get_mem} memory read command.
29763 @subsubheading Example
29765 Read six bytes of memory starting at @code{bytes+6} but then offset by
29766 @code{-6} bytes. Format as three rows of two columns. One byte per
29767 word. Display each word in hex.
29771 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29772 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29773 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29774 prev-page="0x0000138a",memory=[
29775 @{addr="0x00001390",data=["0x00","0x01"]@},
29776 @{addr="0x00001392",data=["0x02","0x03"]@},
29777 @{addr="0x00001394",data=["0x04","0x05"]@}]
29781 Read two bytes of memory starting at address @code{shorts + 64} and
29782 display as a single word formatted in decimal.
29786 5-data-read-memory shorts+64 d 2 1 1
29787 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29788 next-row="0x00001512",prev-row="0x0000150e",
29789 next-page="0x00001512",prev-page="0x0000150e",memory=[
29790 @{addr="0x00001510",data=["128"]@}]
29794 Read thirty two bytes of memory starting at @code{bytes+16} and format
29795 as eight rows of four columns. Include a string encoding with @samp{x}
29796 used as the non-printable character.
29800 4-data-read-memory bytes+16 x 1 8 4 x
29801 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29802 next-row="0x000013c0",prev-row="0x0000139c",
29803 next-page="0x000013c0",prev-page="0x00001380",memory=[
29804 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29805 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29806 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29807 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29808 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29809 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29810 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29811 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29815 @subheading The @code{-data-read-memory-bytes} Command
29816 @findex -data-read-memory-bytes
29818 @subsubheading Synopsis
29821 -data-read-memory-bytes [ -o @var{byte-offset} ]
29822 @var{address} @var{count}
29829 @item @var{address}
29830 An expression specifying the address of the first memory word to be
29831 read. Complex expressions containing embedded white space should be
29832 quoted using the C convention.
29835 The number of bytes to read. This should be an integer literal.
29837 @item @var{byte-offset}
29838 The offsets in bytes relative to @var{address} at which to start
29839 reading. This should be an integer literal. This option is provided
29840 so that a frontend is not required to first evaluate address and then
29841 perform address arithmetics itself.
29845 This command attempts to read all accessible memory regions in the
29846 specified range. First, all regions marked as unreadable in the memory
29847 map (if one is defined) will be skipped. @xref{Memory Region
29848 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29849 regions. For each one, if reading full region results in an errors,
29850 @value{GDBN} will try to read a subset of the region.
29852 In general, every single byte in the region may be readable or not,
29853 and the only way to read every readable byte is to try a read at
29854 every address, which is not practical. Therefore, @value{GDBN} will
29855 attempt to read all accessible bytes at either beginning or the end
29856 of the region, using a binary division scheme. This heuristic works
29857 well for reading accross a memory map boundary. Note that if a region
29858 has a readable range that is neither at the beginning or the end,
29859 @value{GDBN} will not read it.
29861 The result record (@pxref{GDB/MI Result Records}) that is output of
29862 the command includes a field named @samp{memory} whose content is a
29863 list of tuples. Each tuple represent a successfully read memory block
29864 and has the following fields:
29868 The start address of the memory block, as hexadecimal literal.
29871 The end address of the memory block, as hexadecimal literal.
29874 The offset of the memory block, as hexadecimal literal, relative to
29875 the start address passed to @code{-data-read-memory-bytes}.
29878 The contents of the memory block, in hex.
29884 @subsubheading @value{GDBN} Command
29886 The corresponding @value{GDBN} command is @samp{x}.
29888 @subsubheading Example
29892 -data-read-memory-bytes &a 10
29893 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29895 contents="01000000020000000300"@}]
29900 @subheading The @code{-data-write-memory-bytes} Command
29901 @findex -data-write-memory-bytes
29903 @subsubheading Synopsis
29906 -data-write-memory-bytes @var{address} @var{contents}
29913 @item @var{address}
29914 An expression specifying the address of the first memory word to be
29915 read. Complex expressions containing embedded white space should be
29916 quoted using the C convention.
29918 @item @var{contents}
29919 The hex-encoded bytes to write.
29923 @subsubheading @value{GDBN} Command
29925 There's no corresponding @value{GDBN} command.
29927 @subsubheading Example
29931 -data-write-memory-bytes &a "aabbccdd"
29937 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29938 @node GDB/MI Tracepoint Commands
29939 @section @sc{gdb/mi} Tracepoint Commands
29941 The commands defined in this section implement MI support for
29942 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29944 @subheading The @code{-trace-find} Command
29945 @findex -trace-find
29947 @subsubheading Synopsis
29950 -trace-find @var{mode} [@var{parameters}@dots{}]
29953 Find a trace frame using criteria defined by @var{mode} and
29954 @var{parameters}. The following table lists permissible
29955 modes and their parameters. For details of operation, see @ref{tfind}.
29960 No parameters are required. Stops examining trace frames.
29963 An integer is required as parameter. Selects tracepoint frame with
29966 @item tracepoint-number
29967 An integer is required as parameter. Finds next
29968 trace frame that corresponds to tracepoint with the specified number.
29971 An address is required as parameter. Finds
29972 next trace frame that corresponds to any tracepoint at the specified
29975 @item pc-inside-range
29976 Two addresses are required as parameters. Finds next trace
29977 frame that corresponds to a tracepoint at an address inside the
29978 specified range. Both bounds are considered to be inside the range.
29980 @item pc-outside-range
29981 Two addresses are required as parameters. Finds
29982 next trace frame that corresponds to a tracepoint at an address outside
29983 the specified range. Both bounds are considered to be inside the range.
29986 Line specification is required as parameter. @xref{Specify Location}.
29987 Finds next trace frame that corresponds to a tracepoint at
29988 the specified location.
29992 If @samp{none} was passed as @var{mode}, the response does not
29993 have fields. Otherwise, the response may have the following fields:
29997 This field has either @samp{0} or @samp{1} as the value, depending
29998 on whether a matching tracepoint was found.
30001 The index of the found traceframe. This field is present iff
30002 the @samp{found} field has value of @samp{1}.
30005 The index of the found tracepoint. This field is present iff
30006 the @samp{found} field has value of @samp{1}.
30009 The information about the frame corresponding to the found trace
30010 frame. This field is present only if a trace frame was found.
30011 @xref{GDB/MI Frame Information}, for description of this field.
30015 @subsubheading @value{GDBN} Command
30017 The corresponding @value{GDBN} command is @samp{tfind}.
30019 @subheading -trace-define-variable
30020 @findex -trace-define-variable
30022 @subsubheading Synopsis
30025 -trace-define-variable @var{name} [ @var{value} ]
30028 Create trace variable @var{name} if it does not exist. If
30029 @var{value} is specified, sets the initial value of the specified
30030 trace variable to that value. Note that the @var{name} should start
30031 with the @samp{$} character.
30033 @subsubheading @value{GDBN} Command
30035 The corresponding @value{GDBN} command is @samp{tvariable}.
30037 @subheading -trace-list-variables
30038 @findex -trace-list-variables
30040 @subsubheading Synopsis
30043 -trace-list-variables
30046 Return a table of all defined trace variables. Each element of the
30047 table has the following fields:
30051 The name of the trace variable. This field is always present.
30054 The initial value. This is a 64-bit signed integer. This
30055 field is always present.
30058 The value the trace variable has at the moment. This is a 64-bit
30059 signed integer. This field is absent iff current value is
30060 not defined, for example if the trace was never run, or is
30065 @subsubheading @value{GDBN} Command
30067 The corresponding @value{GDBN} command is @samp{tvariables}.
30069 @subsubheading Example
30073 -trace-list-variables
30074 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30075 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30076 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30077 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30078 body=[variable=@{name="$trace_timestamp",initial="0"@}
30079 variable=@{name="$foo",initial="10",current="15"@}]@}
30083 @subheading -trace-save
30084 @findex -trace-save
30086 @subsubheading Synopsis
30089 -trace-save [-r ] @var{filename}
30092 Saves the collected trace data to @var{filename}. Without the
30093 @samp{-r} option, the data is downloaded from the target and saved
30094 in a local file. With the @samp{-r} option the target is asked
30095 to perform the save.
30097 @subsubheading @value{GDBN} Command
30099 The corresponding @value{GDBN} command is @samp{tsave}.
30102 @subheading -trace-start
30103 @findex -trace-start
30105 @subsubheading Synopsis
30111 Starts a tracing experiments. The result of this command does not
30114 @subsubheading @value{GDBN} Command
30116 The corresponding @value{GDBN} command is @samp{tstart}.
30118 @subheading -trace-status
30119 @findex -trace-status
30121 @subsubheading Synopsis
30127 Obtains the status of a tracing experiment. The result may include
30128 the following fields:
30133 May have a value of either @samp{0}, when no tracing operations are
30134 supported, @samp{1}, when all tracing operations are supported, or
30135 @samp{file} when examining trace file. In the latter case, examining
30136 of trace frame is possible but new tracing experiement cannot be
30137 started. This field is always present.
30140 May have a value of either @samp{0} or @samp{1} depending on whether
30141 tracing experiement is in progress on target. This field is present
30142 if @samp{supported} field is not @samp{0}.
30145 Report the reason why the tracing was stopped last time. This field
30146 may be absent iff tracing was never stopped on target yet. The
30147 value of @samp{request} means the tracing was stopped as result of
30148 the @code{-trace-stop} command. The value of @samp{overflow} means
30149 the tracing buffer is full. The value of @samp{disconnection} means
30150 tracing was automatically stopped when @value{GDBN} has disconnected.
30151 The value of @samp{passcount} means tracing was stopped when a
30152 tracepoint was passed a maximal number of times for that tracepoint.
30153 This field is present if @samp{supported} field is not @samp{0}.
30155 @item stopping-tracepoint
30156 The number of tracepoint whose passcount as exceeded. This field is
30157 present iff the @samp{stop-reason} field has the value of
30161 @itemx frames-created
30162 The @samp{frames} field is a count of the total number of trace frames
30163 in the trace buffer, while @samp{frames-created} is the total created
30164 during the run, including ones that were discarded, such as when a
30165 circular trace buffer filled up. Both fields are optional.
30169 These fields tell the current size of the tracing buffer and the
30170 remaining space. These fields are optional.
30173 The value of the circular trace buffer flag. @code{1} means that the
30174 trace buffer is circular and old trace frames will be discarded if
30175 necessary to make room, @code{0} means that the trace buffer is linear
30179 The value of the disconnected tracing flag. @code{1} means that
30180 tracing will continue after @value{GDBN} disconnects, @code{0} means
30181 that the trace run will stop.
30185 @subsubheading @value{GDBN} Command
30187 The corresponding @value{GDBN} command is @samp{tstatus}.
30189 @subheading -trace-stop
30190 @findex -trace-stop
30192 @subsubheading Synopsis
30198 Stops a tracing experiment. The result of this command has the same
30199 fields as @code{-trace-status}, except that the @samp{supported} and
30200 @samp{running} fields are not output.
30202 @subsubheading @value{GDBN} Command
30204 The corresponding @value{GDBN} command is @samp{tstop}.
30207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30208 @node GDB/MI Symbol Query
30209 @section @sc{gdb/mi} Symbol Query Commands
30213 @subheading The @code{-symbol-info-address} Command
30214 @findex -symbol-info-address
30216 @subsubheading Synopsis
30219 -symbol-info-address @var{symbol}
30222 Describe where @var{symbol} is stored.
30224 @subsubheading @value{GDBN} Command
30226 The corresponding @value{GDBN} command is @samp{info address}.
30228 @subsubheading Example
30232 @subheading The @code{-symbol-info-file} Command
30233 @findex -symbol-info-file
30235 @subsubheading Synopsis
30241 Show the file for the symbol.
30243 @subsubheading @value{GDBN} Command
30245 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30246 @samp{gdb_find_file}.
30248 @subsubheading Example
30252 @subheading The @code{-symbol-info-function} Command
30253 @findex -symbol-info-function
30255 @subsubheading Synopsis
30258 -symbol-info-function
30261 Show which function the symbol lives in.
30263 @subsubheading @value{GDBN} Command
30265 @samp{gdb_get_function} in @code{gdbtk}.
30267 @subsubheading Example
30271 @subheading The @code{-symbol-info-line} Command
30272 @findex -symbol-info-line
30274 @subsubheading Synopsis
30280 Show the core addresses of the code for a source line.
30282 @subsubheading @value{GDBN} Command
30284 The corresponding @value{GDBN} command is @samp{info line}.
30285 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30287 @subsubheading Example
30291 @subheading The @code{-symbol-info-symbol} Command
30292 @findex -symbol-info-symbol
30294 @subsubheading Synopsis
30297 -symbol-info-symbol @var{addr}
30300 Describe what symbol is at location @var{addr}.
30302 @subsubheading @value{GDBN} Command
30304 The corresponding @value{GDBN} command is @samp{info symbol}.
30306 @subsubheading Example
30310 @subheading The @code{-symbol-list-functions} Command
30311 @findex -symbol-list-functions
30313 @subsubheading Synopsis
30316 -symbol-list-functions
30319 List the functions in the executable.
30321 @subsubheading @value{GDBN} Command
30323 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30324 @samp{gdb_search} in @code{gdbtk}.
30326 @subsubheading Example
30331 @subheading The @code{-symbol-list-lines} Command
30332 @findex -symbol-list-lines
30334 @subsubheading Synopsis
30337 -symbol-list-lines @var{filename}
30340 Print the list of lines that contain code and their associated program
30341 addresses for the given source filename. The entries are sorted in
30342 ascending PC order.
30344 @subsubheading @value{GDBN} Command
30346 There is no corresponding @value{GDBN} command.
30348 @subsubheading Example
30351 -symbol-list-lines basics.c
30352 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30358 @subheading The @code{-symbol-list-types} Command
30359 @findex -symbol-list-types
30361 @subsubheading Synopsis
30367 List all the type names.
30369 @subsubheading @value{GDBN} Command
30371 The corresponding commands are @samp{info types} in @value{GDBN},
30372 @samp{gdb_search} in @code{gdbtk}.
30374 @subsubheading Example
30378 @subheading The @code{-symbol-list-variables} Command
30379 @findex -symbol-list-variables
30381 @subsubheading Synopsis
30384 -symbol-list-variables
30387 List all the global and static variable names.
30389 @subsubheading @value{GDBN} Command
30391 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30393 @subsubheading Example
30397 @subheading The @code{-symbol-locate} Command
30398 @findex -symbol-locate
30400 @subsubheading Synopsis
30406 @subsubheading @value{GDBN} Command
30408 @samp{gdb_loc} in @code{gdbtk}.
30410 @subsubheading Example
30414 @subheading The @code{-symbol-type} Command
30415 @findex -symbol-type
30417 @subsubheading Synopsis
30420 -symbol-type @var{variable}
30423 Show type of @var{variable}.
30425 @subsubheading @value{GDBN} Command
30427 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30428 @samp{gdb_obj_variable}.
30430 @subsubheading Example
30435 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30436 @node GDB/MI File Commands
30437 @section @sc{gdb/mi} File Commands
30439 This section describes the GDB/MI commands to specify executable file names
30440 and to read in and obtain symbol table information.
30442 @subheading The @code{-file-exec-and-symbols} Command
30443 @findex -file-exec-and-symbols
30445 @subsubheading Synopsis
30448 -file-exec-and-symbols @var{file}
30451 Specify the executable file to be debugged. This file is the one from
30452 which the symbol table is also read. If no file is specified, the
30453 command clears the executable and symbol information. If breakpoints
30454 are set when using this command with no arguments, @value{GDBN} will produce
30455 error messages. Otherwise, no output is produced, except a completion
30458 @subsubheading @value{GDBN} Command
30460 The corresponding @value{GDBN} command is @samp{file}.
30462 @subsubheading Example
30466 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30472 @subheading The @code{-file-exec-file} Command
30473 @findex -file-exec-file
30475 @subsubheading Synopsis
30478 -file-exec-file @var{file}
30481 Specify the executable file to be debugged. Unlike
30482 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30483 from this file. If used without argument, @value{GDBN} clears the information
30484 about the executable file. No output is produced, except a completion
30487 @subsubheading @value{GDBN} Command
30489 The corresponding @value{GDBN} command is @samp{exec-file}.
30491 @subsubheading Example
30495 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30502 @subheading The @code{-file-list-exec-sections} Command
30503 @findex -file-list-exec-sections
30505 @subsubheading Synopsis
30508 -file-list-exec-sections
30511 List the sections of the current executable file.
30513 @subsubheading @value{GDBN} Command
30515 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30516 information as this command. @code{gdbtk} has a corresponding command
30517 @samp{gdb_load_info}.
30519 @subsubheading Example
30524 @subheading The @code{-file-list-exec-source-file} Command
30525 @findex -file-list-exec-source-file
30527 @subsubheading Synopsis
30530 -file-list-exec-source-file
30533 List the line number, the current source file, and the absolute path
30534 to the current source file for the current executable. The macro
30535 information field has a value of @samp{1} or @samp{0} depending on
30536 whether or not the file includes preprocessor macro information.
30538 @subsubheading @value{GDBN} Command
30540 The @value{GDBN} equivalent is @samp{info source}
30542 @subsubheading Example
30546 123-file-list-exec-source-file
30547 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30552 @subheading The @code{-file-list-exec-source-files} Command
30553 @findex -file-list-exec-source-files
30555 @subsubheading Synopsis
30558 -file-list-exec-source-files
30561 List the source files for the current executable.
30563 It will always output the filename, but only when @value{GDBN} can find
30564 the absolute file name of a source file, will it output the fullname.
30566 @subsubheading @value{GDBN} Command
30568 The @value{GDBN} equivalent is @samp{info sources}.
30569 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30571 @subsubheading Example
30574 -file-list-exec-source-files
30576 @{file=foo.c,fullname=/home/foo.c@},
30577 @{file=/home/bar.c,fullname=/home/bar.c@},
30578 @{file=gdb_could_not_find_fullpath.c@}]
30583 @subheading The @code{-file-list-shared-libraries} Command
30584 @findex -file-list-shared-libraries
30586 @subsubheading Synopsis
30589 -file-list-shared-libraries
30592 List the shared libraries in the program.
30594 @subsubheading @value{GDBN} Command
30596 The corresponding @value{GDBN} command is @samp{info shared}.
30598 @subsubheading Example
30602 @subheading The @code{-file-list-symbol-files} Command
30603 @findex -file-list-symbol-files
30605 @subsubheading Synopsis
30608 -file-list-symbol-files
30613 @subsubheading @value{GDBN} Command
30615 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30617 @subsubheading Example
30622 @subheading The @code{-file-symbol-file} Command
30623 @findex -file-symbol-file
30625 @subsubheading Synopsis
30628 -file-symbol-file @var{file}
30631 Read symbol table info from the specified @var{file} argument. When
30632 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30633 produced, except for a completion notification.
30635 @subsubheading @value{GDBN} Command
30637 The corresponding @value{GDBN} command is @samp{symbol-file}.
30639 @subsubheading Example
30643 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30649 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30650 @node GDB/MI Memory Overlay Commands
30651 @section @sc{gdb/mi} Memory Overlay Commands
30653 The memory overlay commands are not implemented.
30655 @c @subheading -overlay-auto
30657 @c @subheading -overlay-list-mapping-state
30659 @c @subheading -overlay-list-overlays
30661 @c @subheading -overlay-map
30663 @c @subheading -overlay-off
30665 @c @subheading -overlay-on
30667 @c @subheading -overlay-unmap
30669 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30670 @node GDB/MI Signal Handling Commands
30671 @section @sc{gdb/mi} Signal Handling Commands
30673 Signal handling commands are not implemented.
30675 @c @subheading -signal-handle
30677 @c @subheading -signal-list-handle-actions
30679 @c @subheading -signal-list-signal-types
30683 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30684 @node GDB/MI Target Manipulation
30685 @section @sc{gdb/mi} Target Manipulation Commands
30688 @subheading The @code{-target-attach} Command
30689 @findex -target-attach
30691 @subsubheading Synopsis
30694 -target-attach @var{pid} | @var{gid} | @var{file}
30697 Attach to a process @var{pid} or a file @var{file} outside of
30698 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30699 group, the id previously returned by
30700 @samp{-list-thread-groups --available} must be used.
30702 @subsubheading @value{GDBN} Command
30704 The corresponding @value{GDBN} command is @samp{attach}.
30706 @subsubheading Example
30710 =thread-created,id="1"
30711 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30717 @subheading The @code{-target-compare-sections} Command
30718 @findex -target-compare-sections
30720 @subsubheading Synopsis
30723 -target-compare-sections [ @var{section} ]
30726 Compare data of section @var{section} on target to the exec file.
30727 Without the argument, all sections are compared.
30729 @subsubheading @value{GDBN} Command
30731 The @value{GDBN} equivalent is @samp{compare-sections}.
30733 @subsubheading Example
30738 @subheading The @code{-target-detach} Command
30739 @findex -target-detach
30741 @subsubheading Synopsis
30744 -target-detach [ @var{pid} | @var{gid} ]
30747 Detach from the remote target which normally resumes its execution.
30748 If either @var{pid} or @var{gid} is specified, detaches from either
30749 the specified process, or specified thread group. There's no output.
30751 @subsubheading @value{GDBN} Command
30753 The corresponding @value{GDBN} command is @samp{detach}.
30755 @subsubheading Example
30765 @subheading The @code{-target-disconnect} Command
30766 @findex -target-disconnect
30768 @subsubheading Synopsis
30774 Disconnect from the remote target. There's no output and the target is
30775 generally not resumed.
30777 @subsubheading @value{GDBN} Command
30779 The corresponding @value{GDBN} command is @samp{disconnect}.
30781 @subsubheading Example
30791 @subheading The @code{-target-download} Command
30792 @findex -target-download
30794 @subsubheading Synopsis
30800 Loads the executable onto the remote target.
30801 It prints out an update message every half second, which includes the fields:
30805 The name of the section.
30807 The size of what has been sent so far for that section.
30809 The size of the section.
30811 The total size of what was sent so far (the current and the previous sections).
30813 The size of the overall executable to download.
30817 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30818 @sc{gdb/mi} Output Syntax}).
30820 In addition, it prints the name and size of the sections, as they are
30821 downloaded. These messages include the following fields:
30825 The name of the section.
30827 The size of the section.
30829 The size of the overall executable to download.
30833 At the end, a summary is printed.
30835 @subsubheading @value{GDBN} Command
30837 The corresponding @value{GDBN} command is @samp{load}.
30839 @subsubheading Example
30841 Note: each status message appears on a single line. Here the messages
30842 have been broken down so that they can fit onto a page.
30847 +download,@{section=".text",section-size="6668",total-size="9880"@}
30848 +download,@{section=".text",section-sent="512",section-size="6668",
30849 total-sent="512",total-size="9880"@}
30850 +download,@{section=".text",section-sent="1024",section-size="6668",
30851 total-sent="1024",total-size="9880"@}
30852 +download,@{section=".text",section-sent="1536",section-size="6668",
30853 total-sent="1536",total-size="9880"@}
30854 +download,@{section=".text",section-sent="2048",section-size="6668",
30855 total-sent="2048",total-size="9880"@}
30856 +download,@{section=".text",section-sent="2560",section-size="6668",
30857 total-sent="2560",total-size="9880"@}
30858 +download,@{section=".text",section-sent="3072",section-size="6668",
30859 total-sent="3072",total-size="9880"@}
30860 +download,@{section=".text",section-sent="3584",section-size="6668",
30861 total-sent="3584",total-size="9880"@}
30862 +download,@{section=".text",section-sent="4096",section-size="6668",
30863 total-sent="4096",total-size="9880"@}
30864 +download,@{section=".text",section-sent="4608",section-size="6668",
30865 total-sent="4608",total-size="9880"@}
30866 +download,@{section=".text",section-sent="5120",section-size="6668",
30867 total-sent="5120",total-size="9880"@}
30868 +download,@{section=".text",section-sent="5632",section-size="6668",
30869 total-sent="5632",total-size="9880"@}
30870 +download,@{section=".text",section-sent="6144",section-size="6668",
30871 total-sent="6144",total-size="9880"@}
30872 +download,@{section=".text",section-sent="6656",section-size="6668",
30873 total-sent="6656",total-size="9880"@}
30874 +download,@{section=".init",section-size="28",total-size="9880"@}
30875 +download,@{section=".fini",section-size="28",total-size="9880"@}
30876 +download,@{section=".data",section-size="3156",total-size="9880"@}
30877 +download,@{section=".data",section-sent="512",section-size="3156",
30878 total-sent="7236",total-size="9880"@}
30879 +download,@{section=".data",section-sent="1024",section-size="3156",
30880 total-sent="7748",total-size="9880"@}
30881 +download,@{section=".data",section-sent="1536",section-size="3156",
30882 total-sent="8260",total-size="9880"@}
30883 +download,@{section=".data",section-sent="2048",section-size="3156",
30884 total-sent="8772",total-size="9880"@}
30885 +download,@{section=".data",section-sent="2560",section-size="3156",
30886 total-sent="9284",total-size="9880"@}
30887 +download,@{section=".data",section-sent="3072",section-size="3156",
30888 total-sent="9796",total-size="9880"@}
30889 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30896 @subheading The @code{-target-exec-status} Command
30897 @findex -target-exec-status
30899 @subsubheading Synopsis
30902 -target-exec-status
30905 Provide information on the state of the target (whether it is running or
30906 not, for instance).
30908 @subsubheading @value{GDBN} Command
30910 There's no equivalent @value{GDBN} command.
30912 @subsubheading Example
30916 @subheading The @code{-target-list-available-targets} Command
30917 @findex -target-list-available-targets
30919 @subsubheading Synopsis
30922 -target-list-available-targets
30925 List the possible targets to connect to.
30927 @subsubheading @value{GDBN} Command
30929 The corresponding @value{GDBN} command is @samp{help target}.
30931 @subsubheading Example
30935 @subheading The @code{-target-list-current-targets} Command
30936 @findex -target-list-current-targets
30938 @subsubheading Synopsis
30941 -target-list-current-targets
30944 Describe the current target.
30946 @subsubheading @value{GDBN} Command
30948 The corresponding information is printed by @samp{info file} (among
30951 @subsubheading Example
30955 @subheading The @code{-target-list-parameters} Command
30956 @findex -target-list-parameters
30958 @subsubheading Synopsis
30961 -target-list-parameters
30967 @subsubheading @value{GDBN} Command
30971 @subsubheading Example
30975 @subheading The @code{-target-select} Command
30976 @findex -target-select
30978 @subsubheading Synopsis
30981 -target-select @var{type} @var{parameters @dots{}}
30984 Connect @value{GDBN} to the remote target. This command takes two args:
30988 The type of target, for instance @samp{remote}, etc.
30989 @item @var{parameters}
30990 Device names, host names and the like. @xref{Target Commands, ,
30991 Commands for Managing Targets}, for more details.
30994 The output is a connection notification, followed by the address at
30995 which the target program is, in the following form:
30998 ^connected,addr="@var{address}",func="@var{function name}",
30999 args=[@var{arg list}]
31002 @subsubheading @value{GDBN} Command
31004 The corresponding @value{GDBN} command is @samp{target}.
31006 @subsubheading Example
31010 -target-select remote /dev/ttya
31011 ^connected,addr="0xfe00a300",func="??",args=[]
31015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31016 @node GDB/MI File Transfer Commands
31017 @section @sc{gdb/mi} File Transfer Commands
31020 @subheading The @code{-target-file-put} Command
31021 @findex -target-file-put
31023 @subsubheading Synopsis
31026 -target-file-put @var{hostfile} @var{targetfile}
31029 Copy file @var{hostfile} from the host system (the machine running
31030 @value{GDBN}) to @var{targetfile} on the target system.
31032 @subsubheading @value{GDBN} Command
31034 The corresponding @value{GDBN} command is @samp{remote put}.
31036 @subsubheading Example
31040 -target-file-put localfile remotefile
31046 @subheading The @code{-target-file-get} Command
31047 @findex -target-file-get
31049 @subsubheading Synopsis
31052 -target-file-get @var{targetfile} @var{hostfile}
31055 Copy file @var{targetfile} from the target system to @var{hostfile}
31056 on the host system.
31058 @subsubheading @value{GDBN} Command
31060 The corresponding @value{GDBN} command is @samp{remote get}.
31062 @subsubheading Example
31066 -target-file-get remotefile localfile
31072 @subheading The @code{-target-file-delete} Command
31073 @findex -target-file-delete
31075 @subsubheading Synopsis
31078 -target-file-delete @var{targetfile}
31081 Delete @var{targetfile} from the target system.
31083 @subsubheading @value{GDBN} Command
31085 The corresponding @value{GDBN} command is @samp{remote delete}.
31087 @subsubheading Example
31091 -target-file-delete remotefile
31097 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31098 @node GDB/MI Miscellaneous Commands
31099 @section Miscellaneous @sc{gdb/mi} Commands
31101 @c @subheading -gdb-complete
31103 @subheading The @code{-gdb-exit} Command
31106 @subsubheading Synopsis
31112 Exit @value{GDBN} immediately.
31114 @subsubheading @value{GDBN} Command
31116 Approximately corresponds to @samp{quit}.
31118 @subsubheading Example
31128 @subheading The @code{-exec-abort} Command
31129 @findex -exec-abort
31131 @subsubheading Synopsis
31137 Kill the inferior running program.
31139 @subsubheading @value{GDBN} Command
31141 The corresponding @value{GDBN} command is @samp{kill}.
31143 @subsubheading Example
31148 @subheading The @code{-gdb-set} Command
31151 @subsubheading Synopsis
31157 Set an internal @value{GDBN} variable.
31158 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31160 @subsubheading @value{GDBN} Command
31162 The corresponding @value{GDBN} command is @samp{set}.
31164 @subsubheading Example
31174 @subheading The @code{-gdb-show} Command
31177 @subsubheading Synopsis
31183 Show the current value of a @value{GDBN} variable.
31185 @subsubheading @value{GDBN} Command
31187 The corresponding @value{GDBN} command is @samp{show}.
31189 @subsubheading Example
31198 @c @subheading -gdb-source
31201 @subheading The @code{-gdb-version} Command
31202 @findex -gdb-version
31204 @subsubheading Synopsis
31210 Show version information for @value{GDBN}. Used mostly in testing.
31212 @subsubheading @value{GDBN} Command
31214 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31215 default shows this information when you start an interactive session.
31217 @subsubheading Example
31219 @c This example modifies the actual output from GDB to avoid overfull
31225 ~Copyright 2000 Free Software Foundation, Inc.
31226 ~GDB is free software, covered by the GNU General Public License, and
31227 ~you are welcome to change it and/or distribute copies of it under
31228 ~ certain conditions.
31229 ~Type "show copying" to see the conditions.
31230 ~There is absolutely no warranty for GDB. Type "show warranty" for
31232 ~This GDB was configured as
31233 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31238 @subheading The @code{-list-features} Command
31239 @findex -list-features
31241 Returns a list of particular features of the MI protocol that
31242 this version of gdb implements. A feature can be a command,
31243 or a new field in an output of some command, or even an
31244 important bugfix. While a frontend can sometimes detect presence
31245 of a feature at runtime, it is easier to perform detection at debugger
31248 The command returns a list of strings, with each string naming an
31249 available feature. Each returned string is just a name, it does not
31250 have any internal structure. The list of possible feature names
31256 (gdb) -list-features
31257 ^done,result=["feature1","feature2"]
31260 The current list of features is:
31263 @item frozen-varobjs
31264 Indicates support for the @code{-var-set-frozen} command, as well
31265 as possible presense of the @code{frozen} field in the output
31266 of @code{-varobj-create}.
31267 @item pending-breakpoints
31268 Indicates support for the @option{-f} option to the @code{-break-insert}
31271 Indicates Python scripting support, Python-based
31272 pretty-printing commands, and possible presence of the
31273 @samp{display_hint} field in the output of @code{-var-list-children}
31275 Indicates support for the @code{-thread-info} command.
31276 @item data-read-memory-bytes
31277 Indicates support for the @code{-data-read-memory-bytes} and the
31278 @code{-data-write-memory-bytes} commands.
31279 @item breakpoint-notifications
31280 Indicates that changes to breakpoints and breakpoints created via the
31281 CLI will be announced via async records.
31282 @item ada-task-info
31283 Indicates support for the @code{-ada-task-info} command.
31286 @subheading The @code{-list-target-features} Command
31287 @findex -list-target-features
31289 Returns a list of particular features that are supported by the
31290 target. Those features affect the permitted MI commands, but
31291 unlike the features reported by the @code{-list-features} command, the
31292 features depend on which target GDB is using at the moment. Whenever
31293 a target can change, due to commands such as @code{-target-select},
31294 @code{-target-attach} or @code{-exec-run}, the list of target features
31295 may change, and the frontend should obtain it again.
31299 (gdb) -list-features
31300 ^done,result=["async"]
31303 The current list of features is:
31307 Indicates that the target is capable of asynchronous command
31308 execution, which means that @value{GDBN} will accept further commands
31309 while the target is running.
31312 Indicates that the target is capable of reverse execution.
31313 @xref{Reverse Execution}, for more information.
31317 @subheading The @code{-list-thread-groups} Command
31318 @findex -list-thread-groups
31320 @subheading Synopsis
31323 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31326 Lists thread groups (@pxref{Thread groups}). When a single thread
31327 group is passed as the argument, lists the children of that group.
31328 When several thread group are passed, lists information about those
31329 thread groups. Without any parameters, lists information about all
31330 top-level thread groups.
31332 Normally, thread groups that are being debugged are reported.
31333 With the @samp{--available} option, @value{GDBN} reports thread groups
31334 available on the target.
31336 The output of this command may have either a @samp{threads} result or
31337 a @samp{groups} result. The @samp{thread} result has a list of tuples
31338 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31339 Information}). The @samp{groups} result has a list of tuples as value,
31340 each tuple describing a thread group. If top-level groups are
31341 requested (that is, no parameter is passed), or when several groups
31342 are passed, the output always has a @samp{groups} result. The format
31343 of the @samp{group} result is described below.
31345 To reduce the number of roundtrips it's possible to list thread groups
31346 together with their children, by passing the @samp{--recurse} option
31347 and the recursion depth. Presently, only recursion depth of 1 is
31348 permitted. If this option is present, then every reported thread group
31349 will also include its children, either as @samp{group} or
31350 @samp{threads} field.
31352 In general, any combination of option and parameters is permitted, with
31353 the following caveats:
31357 When a single thread group is passed, the output will typically
31358 be the @samp{threads} result. Because threads may not contain
31359 anything, the @samp{recurse} option will be ignored.
31362 When the @samp{--available} option is passed, limited information may
31363 be available. In particular, the list of threads of a process might
31364 be inaccessible. Further, specifying specific thread groups might
31365 not give any performance advantage over listing all thread groups.
31366 The frontend should assume that @samp{-list-thread-groups --available}
31367 is always an expensive operation and cache the results.
31371 The @samp{groups} result is a list of tuples, where each tuple may
31372 have the following fields:
31376 Identifier of the thread group. This field is always present.
31377 The identifier is an opaque string; frontends should not try to
31378 convert it to an integer, even though it might look like one.
31381 The type of the thread group. At present, only @samp{process} is a
31385 The target-specific process identifier. This field is only present
31386 for thread groups of type @samp{process} and only if the process exists.
31389 The number of children this thread group has. This field may be
31390 absent for an available thread group.
31393 This field has a list of tuples as value, each tuple describing a
31394 thread. It may be present if the @samp{--recurse} option is
31395 specified, and it's actually possible to obtain the threads.
31398 This field is a list of integers, each identifying a core that one
31399 thread of the group is running on. This field may be absent if
31400 such information is not available.
31403 The name of the executable file that corresponds to this thread group.
31404 The field is only present for thread groups of type @samp{process},
31405 and only if there is a corresponding executable file.
31409 @subheading Example
31413 -list-thread-groups
31414 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31415 -list-thread-groups 17
31416 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31417 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31418 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31419 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31420 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31421 -list-thread-groups --available
31422 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31423 -list-thread-groups --available --recurse 1
31424 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31425 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31426 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31427 -list-thread-groups --available --recurse 1 17 18
31428 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31429 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31430 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31434 @subheading The @code{-add-inferior} Command
31435 @findex -add-inferior
31437 @subheading Synopsis
31443 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31444 inferior is not associated with any executable. Such association may
31445 be established with the @samp{-file-exec-and-symbols} command
31446 (@pxref{GDB/MI File Commands}). The command response has a single
31447 field, @samp{thread-group}, whose value is the identifier of the
31448 thread group corresponding to the new inferior.
31450 @subheading Example
31455 ^done,thread-group="i3"
31458 @subheading The @code{-interpreter-exec} Command
31459 @findex -interpreter-exec
31461 @subheading Synopsis
31464 -interpreter-exec @var{interpreter} @var{command}
31466 @anchor{-interpreter-exec}
31468 Execute the specified @var{command} in the given @var{interpreter}.
31470 @subheading @value{GDBN} Command
31472 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31474 @subheading Example
31478 -interpreter-exec console "break main"
31479 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31480 &"During symbol reading, bad structure-type format.\n"
31481 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31486 @subheading The @code{-inferior-tty-set} Command
31487 @findex -inferior-tty-set
31489 @subheading Synopsis
31492 -inferior-tty-set /dev/pts/1
31495 Set terminal for future runs of the program being debugged.
31497 @subheading @value{GDBN} Command
31499 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31501 @subheading Example
31505 -inferior-tty-set /dev/pts/1
31510 @subheading The @code{-inferior-tty-show} Command
31511 @findex -inferior-tty-show
31513 @subheading Synopsis
31519 Show terminal for future runs of program being debugged.
31521 @subheading @value{GDBN} Command
31523 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31525 @subheading Example
31529 -inferior-tty-set /dev/pts/1
31533 ^done,inferior_tty_terminal="/dev/pts/1"
31537 @subheading The @code{-enable-timings} Command
31538 @findex -enable-timings
31540 @subheading Synopsis
31543 -enable-timings [yes | no]
31546 Toggle the printing of the wallclock, user and system times for an MI
31547 command as a field in its output. This command is to help frontend
31548 developers optimize the performance of their code. No argument is
31549 equivalent to @samp{yes}.
31551 @subheading @value{GDBN} Command
31555 @subheading Example
31563 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31564 addr="0x080484ed",func="main",file="myprog.c",
31565 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31566 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31574 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31575 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31576 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31577 fullname="/home/nickrob/myprog.c",line="73"@}
31582 @chapter @value{GDBN} Annotations
31584 This chapter describes annotations in @value{GDBN}. Annotations were
31585 designed to interface @value{GDBN} to graphical user interfaces or other
31586 similar programs which want to interact with @value{GDBN} at a
31587 relatively high level.
31589 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31593 This is Edition @value{EDITION}, @value{DATE}.
31597 * Annotations Overview:: What annotations are; the general syntax.
31598 * Server Prefix:: Issuing a command without affecting user state.
31599 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31600 * Errors:: Annotations for error messages.
31601 * Invalidation:: Some annotations describe things now invalid.
31602 * Annotations for Running::
31603 Whether the program is running, how it stopped, etc.
31604 * Source Annotations:: Annotations describing source code.
31607 @node Annotations Overview
31608 @section What is an Annotation?
31609 @cindex annotations
31611 Annotations start with a newline character, two @samp{control-z}
31612 characters, and the name of the annotation. If there is no additional
31613 information associated with this annotation, the name of the annotation
31614 is followed immediately by a newline. If there is additional
31615 information, the name of the annotation is followed by a space, the
31616 additional information, and a newline. The additional information
31617 cannot contain newline characters.
31619 Any output not beginning with a newline and two @samp{control-z}
31620 characters denotes literal output from @value{GDBN}. Currently there is
31621 no need for @value{GDBN} to output a newline followed by two
31622 @samp{control-z} characters, but if there was such a need, the
31623 annotations could be extended with an @samp{escape} annotation which
31624 means those three characters as output.
31626 The annotation @var{level}, which is specified using the
31627 @option{--annotate} command line option (@pxref{Mode Options}), controls
31628 how much information @value{GDBN} prints together with its prompt,
31629 values of expressions, source lines, and other types of output. Level 0
31630 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31631 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31632 for programs that control @value{GDBN}, and level 2 annotations have
31633 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31634 Interface, annotate, GDB's Obsolete Annotations}).
31637 @kindex set annotate
31638 @item set annotate @var{level}
31639 The @value{GDBN} command @code{set annotate} sets the level of
31640 annotations to the specified @var{level}.
31642 @item show annotate
31643 @kindex show annotate
31644 Show the current annotation level.
31647 This chapter describes level 3 annotations.
31649 A simple example of starting up @value{GDBN} with annotations is:
31652 $ @kbd{gdb --annotate=3}
31654 Copyright 2003 Free Software Foundation, Inc.
31655 GDB is free software, covered by the GNU General Public License,
31656 and you are welcome to change it and/or distribute copies of it
31657 under certain conditions.
31658 Type "show copying" to see the conditions.
31659 There is absolutely no warranty for GDB. Type "show warranty"
31661 This GDB was configured as "i386-pc-linux-gnu"
31672 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31673 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31674 denotes a @samp{control-z} character) are annotations; the rest is
31675 output from @value{GDBN}.
31677 @node Server Prefix
31678 @section The Server Prefix
31679 @cindex server prefix
31681 If you prefix a command with @samp{server } then it will not affect
31682 the command history, nor will it affect @value{GDBN}'s notion of which
31683 command to repeat if @key{RET} is pressed on a line by itself. This
31684 means that commands can be run behind a user's back by a front-end in
31685 a transparent manner.
31687 The @code{server } prefix does not affect the recording of values into
31688 the value history; to print a value without recording it into the
31689 value history, use the @code{output} command instead of the
31690 @code{print} command.
31692 Using this prefix also disables confirmation requests
31693 (@pxref{confirmation requests}).
31696 @section Annotation for @value{GDBN} Input
31698 @cindex annotations for prompts
31699 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31700 to know when to send output, when the output from a given command is
31703 Different kinds of input each have a different @dfn{input type}. Each
31704 input type has three annotations: a @code{pre-} annotation, which
31705 denotes the beginning of any prompt which is being output, a plain
31706 annotation, which denotes the end of the prompt, and then a @code{post-}
31707 annotation which denotes the end of any echo which may (or may not) be
31708 associated with the input. For example, the @code{prompt} input type
31709 features the following annotations:
31717 The input types are
31720 @findex pre-prompt annotation
31721 @findex prompt annotation
31722 @findex post-prompt annotation
31724 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31726 @findex pre-commands annotation
31727 @findex commands annotation
31728 @findex post-commands annotation
31730 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31731 command. The annotations are repeated for each command which is input.
31733 @findex pre-overload-choice annotation
31734 @findex overload-choice annotation
31735 @findex post-overload-choice annotation
31736 @item overload-choice
31737 When @value{GDBN} wants the user to select between various overloaded functions.
31739 @findex pre-query annotation
31740 @findex query annotation
31741 @findex post-query annotation
31743 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31745 @findex pre-prompt-for-continue annotation
31746 @findex prompt-for-continue annotation
31747 @findex post-prompt-for-continue annotation
31748 @item prompt-for-continue
31749 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31750 expect this to work well; instead use @code{set height 0} to disable
31751 prompting. This is because the counting of lines is buggy in the
31752 presence of annotations.
31757 @cindex annotations for errors, warnings and interrupts
31759 @findex quit annotation
31764 This annotation occurs right before @value{GDBN} responds to an interrupt.
31766 @findex error annotation
31771 This annotation occurs right before @value{GDBN} responds to an error.
31773 Quit and error annotations indicate that any annotations which @value{GDBN} was
31774 in the middle of may end abruptly. For example, if a
31775 @code{value-history-begin} annotation is followed by a @code{error}, one
31776 cannot expect to receive the matching @code{value-history-end}. One
31777 cannot expect not to receive it either, however; an error annotation
31778 does not necessarily mean that @value{GDBN} is immediately returning all the way
31781 @findex error-begin annotation
31782 A quit or error annotation may be preceded by
31788 Any output between that and the quit or error annotation is the error
31791 Warning messages are not yet annotated.
31792 @c If we want to change that, need to fix warning(), type_error(),
31793 @c range_error(), and possibly other places.
31796 @section Invalidation Notices
31798 @cindex annotations for invalidation messages
31799 The following annotations say that certain pieces of state may have
31803 @findex frames-invalid annotation
31804 @item ^Z^Zframes-invalid
31806 The frames (for example, output from the @code{backtrace} command) may
31809 @findex breakpoints-invalid annotation
31810 @item ^Z^Zbreakpoints-invalid
31812 The breakpoints may have changed. For example, the user just added or
31813 deleted a breakpoint.
31816 @node Annotations for Running
31817 @section Running the Program
31818 @cindex annotations for running programs
31820 @findex starting annotation
31821 @findex stopping annotation
31822 When the program starts executing due to a @value{GDBN} command such as
31823 @code{step} or @code{continue},
31829 is output. When the program stops,
31835 is output. Before the @code{stopped} annotation, a variety of
31836 annotations describe how the program stopped.
31839 @findex exited annotation
31840 @item ^Z^Zexited @var{exit-status}
31841 The program exited, and @var{exit-status} is the exit status (zero for
31842 successful exit, otherwise nonzero).
31844 @findex signalled annotation
31845 @findex signal-name annotation
31846 @findex signal-name-end annotation
31847 @findex signal-string annotation
31848 @findex signal-string-end annotation
31849 @item ^Z^Zsignalled
31850 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31851 annotation continues:
31857 ^Z^Zsignal-name-end
31861 ^Z^Zsignal-string-end
31866 where @var{name} is the name of the signal, such as @code{SIGILL} or
31867 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31868 as @code{Illegal Instruction} or @code{Segmentation fault}.
31869 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31870 user's benefit and have no particular format.
31872 @findex signal annotation
31874 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31875 just saying that the program received the signal, not that it was
31876 terminated with it.
31878 @findex breakpoint annotation
31879 @item ^Z^Zbreakpoint @var{number}
31880 The program hit breakpoint number @var{number}.
31882 @findex watchpoint annotation
31883 @item ^Z^Zwatchpoint @var{number}
31884 The program hit watchpoint number @var{number}.
31887 @node Source Annotations
31888 @section Displaying Source
31889 @cindex annotations for source display
31891 @findex source annotation
31892 The following annotation is used instead of displaying source code:
31895 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31898 where @var{filename} is an absolute file name indicating which source
31899 file, @var{line} is the line number within that file (where 1 is the
31900 first line in the file), @var{character} is the character position
31901 within the file (where 0 is the first character in the file) (for most
31902 debug formats this will necessarily point to the beginning of a line),
31903 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31904 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31905 @var{addr} is the address in the target program associated with the
31906 source which is being displayed. @var{addr} is in the form @samp{0x}
31907 followed by one or more lowercase hex digits (note that this does not
31908 depend on the language).
31910 @node JIT Interface
31911 @chapter JIT Compilation Interface
31912 @cindex just-in-time compilation
31913 @cindex JIT compilation interface
31915 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31916 interface. A JIT compiler is a program or library that generates native
31917 executable code at runtime and executes it, usually in order to achieve good
31918 performance while maintaining platform independence.
31920 Programs that use JIT compilation are normally difficult to debug because
31921 portions of their code are generated at runtime, instead of being loaded from
31922 object files, which is where @value{GDBN} normally finds the program's symbols
31923 and debug information. In order to debug programs that use JIT compilation,
31924 @value{GDBN} has an interface that allows the program to register in-memory
31925 symbol files with @value{GDBN} at runtime.
31927 If you are using @value{GDBN} to debug a program that uses this interface, then
31928 it should work transparently so long as you have not stripped the binary. If
31929 you are developing a JIT compiler, then the interface is documented in the rest
31930 of this chapter. At this time, the only known client of this interface is the
31933 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31934 JIT compiler communicates with @value{GDBN} by writing data into a global
31935 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31936 attaches, it reads a linked list of symbol files from the global variable to
31937 find existing code, and puts a breakpoint in the function so that it can find
31938 out about additional code.
31941 * Declarations:: Relevant C struct declarations
31942 * Registering Code:: Steps to register code
31943 * Unregistering Code:: Steps to unregister code
31944 * Custom Debug Info:: Emit debug information in a custom format
31948 @section JIT Declarations
31950 These are the relevant struct declarations that a C program should include to
31951 implement the interface:
31961 struct jit_code_entry
31963 struct jit_code_entry *next_entry;
31964 struct jit_code_entry *prev_entry;
31965 const char *symfile_addr;
31966 uint64_t symfile_size;
31969 struct jit_descriptor
31972 /* This type should be jit_actions_t, but we use uint32_t
31973 to be explicit about the bitwidth. */
31974 uint32_t action_flag;
31975 struct jit_code_entry *relevant_entry;
31976 struct jit_code_entry *first_entry;
31979 /* GDB puts a breakpoint in this function. */
31980 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31982 /* Make sure to specify the version statically, because the
31983 debugger may check the version before we can set it. */
31984 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31987 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31988 modifications to this global data properly, which can easily be done by putting
31989 a global mutex around modifications to these structures.
31991 @node Registering Code
31992 @section Registering Code
31994 To register code with @value{GDBN}, the JIT should follow this protocol:
31998 Generate an object file in memory with symbols and other desired debug
31999 information. The file must include the virtual addresses of the sections.
32002 Create a code entry for the file, which gives the start and size of the symbol
32006 Add it to the linked list in the JIT descriptor.
32009 Point the relevant_entry field of the descriptor at the entry.
32012 Set @code{action_flag} to @code{JIT_REGISTER} and call
32013 @code{__jit_debug_register_code}.
32016 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32017 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32018 new code. However, the linked list must still be maintained in order to allow
32019 @value{GDBN} to attach to a running process and still find the symbol files.
32021 @node Unregistering Code
32022 @section Unregistering Code
32024 If code is freed, then the JIT should use the following protocol:
32028 Remove the code entry corresponding to the code from the linked list.
32031 Point the @code{relevant_entry} field of the descriptor at the code entry.
32034 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32035 @code{__jit_debug_register_code}.
32038 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32039 and the JIT will leak the memory used for the associated symbol files.
32041 @node Custom Debug Info
32042 @section Custom Debug Info
32043 @cindex custom JIT debug info
32044 @cindex JIT debug info reader
32046 Generating debug information in platform-native file formats (like ELF
32047 or COFF) may be an overkill for JIT compilers; especially if all the
32048 debug info is used for is displaying a meaningful backtrace. The
32049 issue can be resolved by having the JIT writers decide on a debug info
32050 format and also provide a reader that parses the debug info generated
32051 by the JIT compiler. This section gives a brief overview on writing
32052 such a parser. More specific details can be found in the source file
32053 @file{gdb/jit-reader.in}, which is also installed as a header at
32054 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32056 The reader is implemented as a shared object (so this functionality is
32057 not available on platforms which don't allow loading shared objects at
32058 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32059 @code{jit-reader-unload} are provided, to be used to load and unload
32060 the readers from a preconfigured directory. Once loaded, the shared
32061 object is used the parse the debug information emitted by the JIT
32065 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32066 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32069 @node Using JIT Debug Info Readers
32070 @subsection Using JIT Debug Info Readers
32071 @kindex jit-reader-load
32072 @kindex jit-reader-unload
32074 Readers can be loaded and unloaded using the @code{jit-reader-load}
32075 and @code{jit-reader-unload} commands.
32078 @item jit-reader-load @var{reader-name}
32079 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32080 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32081 @var{libdir} is the system library directory, usually
32082 @file{/usr/local/lib}. Only one reader can be active at a time;
32083 trying to load a second reader when one is already loaded will result
32084 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32085 first unloading the current one using @code{jit-reader-load} and then
32086 invoking @code{jit-reader-load}.
32088 @item jit-reader-unload
32089 Unload the currently loaded JIT reader.
32093 @node Writing JIT Debug Info Readers
32094 @subsection Writing JIT Debug Info Readers
32095 @cindex writing JIT debug info readers
32097 As mentioned, a reader is essentially a shared object conforming to a
32098 certain ABI. This ABI is described in @file{jit-reader.h}.
32100 @file{jit-reader.h} defines the structures, macros and functions
32101 required to write a reader. It is installed (along with
32102 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32103 the system include directory.
32105 Readers need to be released under a GPL compatible license. A reader
32106 can be declared as released under such a license by placing the macro
32107 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32109 The entry point for readers is the symbol @code{gdb_init_reader},
32110 which is expected to be a function with the prototype
32112 @findex gdb_init_reader
32114 extern struct gdb_reader_funcs *gdb_init_reader (void);
32117 @cindex @code{struct gdb_reader_funcs}
32119 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32120 functions. These functions are executed to read the debug info
32121 generated by the JIT compiler (@code{read}), to unwind stack frames
32122 (@code{unwind}) and to create canonical frame IDs
32123 (@code{get_Frame_id}). It also has a callback that is called when the
32124 reader is being unloaded (@code{destroy}). The struct looks like this
32127 struct gdb_reader_funcs
32129 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32130 int reader_version;
32132 /* For use by the reader. */
32135 gdb_read_debug_info *read;
32136 gdb_unwind_frame *unwind;
32137 gdb_get_frame_id *get_frame_id;
32138 gdb_destroy_reader *destroy;
32142 @cindex @code{struct gdb_symbol_callbacks}
32143 @cindex @code{struct gdb_unwind_callbacks}
32145 The callbacks are provided with another set of callbacks by
32146 @value{GDBN} to do their job. For @code{read}, these callbacks are
32147 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32148 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32149 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32150 files and new symbol tables inside those object files. @code{struct
32151 gdb_unwind_callbacks} has callbacks to read registers off the current
32152 frame and to write out the values of the registers in the previous
32153 frame. Both have a callback (@code{target_read}) to read bytes off the
32154 target's address space.
32157 @chapter Reporting Bugs in @value{GDBN}
32158 @cindex bugs in @value{GDBN}
32159 @cindex reporting bugs in @value{GDBN}
32161 Your bug reports play an essential role in making @value{GDBN} reliable.
32163 Reporting a bug may help you by bringing a solution to your problem, or it
32164 may not. But in any case the principal function of a bug report is to help
32165 the entire community by making the next version of @value{GDBN} work better. Bug
32166 reports are your contribution to the maintenance of @value{GDBN}.
32168 In order for a bug report to serve its purpose, you must include the
32169 information that enables us to fix the bug.
32172 * Bug Criteria:: Have you found a bug?
32173 * Bug Reporting:: How to report bugs
32177 @section Have You Found a Bug?
32178 @cindex bug criteria
32180 If you are not sure whether you have found a bug, here are some guidelines:
32183 @cindex fatal signal
32184 @cindex debugger crash
32185 @cindex crash of debugger
32187 If the debugger gets a fatal signal, for any input whatever, that is a
32188 @value{GDBN} bug. Reliable debuggers never crash.
32190 @cindex error on valid input
32192 If @value{GDBN} produces an error message for valid input, that is a
32193 bug. (Note that if you're cross debugging, the problem may also be
32194 somewhere in the connection to the target.)
32196 @cindex invalid input
32198 If @value{GDBN} does not produce an error message for invalid input,
32199 that is a bug. However, you should note that your idea of
32200 ``invalid input'' might be our idea of ``an extension'' or ``support
32201 for traditional practice''.
32204 If you are an experienced user of debugging tools, your suggestions
32205 for improvement of @value{GDBN} are welcome in any case.
32208 @node Bug Reporting
32209 @section How to Report Bugs
32210 @cindex bug reports
32211 @cindex @value{GDBN} bugs, reporting
32213 A number of companies and individuals offer support for @sc{gnu} products.
32214 If you obtained @value{GDBN} from a support organization, we recommend you
32215 contact that organization first.
32217 You can find contact information for many support companies and
32218 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32220 @c should add a web page ref...
32223 @ifset BUGURL_DEFAULT
32224 In any event, we also recommend that you submit bug reports for
32225 @value{GDBN}. The preferred method is to submit them directly using
32226 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32227 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32230 @strong{Do not send bug reports to @samp{info-gdb}, or to
32231 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32232 not want to receive bug reports. Those that do have arranged to receive
32235 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32236 serves as a repeater. The mailing list and the newsgroup carry exactly
32237 the same messages. Often people think of posting bug reports to the
32238 newsgroup instead of mailing them. This appears to work, but it has one
32239 problem which can be crucial: a newsgroup posting often lacks a mail
32240 path back to the sender. Thus, if we need to ask for more information,
32241 we may be unable to reach you. For this reason, it is better to send
32242 bug reports to the mailing list.
32244 @ifclear BUGURL_DEFAULT
32245 In any event, we also recommend that you submit bug reports for
32246 @value{GDBN} to @value{BUGURL}.
32250 The fundamental principle of reporting bugs usefully is this:
32251 @strong{report all the facts}. If you are not sure whether to state a
32252 fact or leave it out, state it!
32254 Often people omit facts because they think they know what causes the
32255 problem and assume that some details do not matter. Thus, you might
32256 assume that the name of the variable you use in an example does not matter.
32257 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32258 stray memory reference which happens to fetch from the location where that
32259 name is stored in memory; perhaps, if the name were different, the contents
32260 of that location would fool the debugger into doing the right thing despite
32261 the bug. Play it safe and give a specific, complete example. That is the
32262 easiest thing for you to do, and the most helpful.
32264 Keep in mind that the purpose of a bug report is to enable us to fix the
32265 bug. It may be that the bug has been reported previously, but neither
32266 you nor we can know that unless your bug report is complete and
32269 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32270 bell?'' Those bug reports are useless, and we urge everyone to
32271 @emph{refuse to respond to them} except to chide the sender to report
32274 To enable us to fix the bug, you should include all these things:
32278 The version of @value{GDBN}. @value{GDBN} announces it if you start
32279 with no arguments; you can also print it at any time using @code{show
32282 Without this, we will not know whether there is any point in looking for
32283 the bug in the current version of @value{GDBN}.
32286 The type of machine you are using, and the operating system name and
32290 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32291 ``@value{GCC}--2.8.1''.
32294 What compiler (and its version) was used to compile the program you are
32295 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32296 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32297 to get this information; for other compilers, see the documentation for
32301 The command arguments you gave the compiler to compile your example and
32302 observe the bug. For example, did you use @samp{-O}? To guarantee
32303 you will not omit something important, list them all. A copy of the
32304 Makefile (or the output from make) is sufficient.
32306 If we were to try to guess the arguments, we would probably guess wrong
32307 and then we might not encounter the bug.
32310 A complete input script, and all necessary source files, that will
32314 A description of what behavior you observe that you believe is
32315 incorrect. For example, ``It gets a fatal signal.''
32317 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32318 will certainly notice it. But if the bug is incorrect output, we might
32319 not notice unless it is glaringly wrong. You might as well not give us
32320 a chance to make a mistake.
32322 Even if the problem you experience is a fatal signal, you should still
32323 say so explicitly. Suppose something strange is going on, such as, your
32324 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32325 the C library on your system. (This has happened!) Your copy might
32326 crash and ours would not. If you told us to expect a crash, then when
32327 ours fails to crash, we would know that the bug was not happening for
32328 us. If you had not told us to expect a crash, then we would not be able
32329 to draw any conclusion from our observations.
32332 @cindex recording a session script
32333 To collect all this information, you can use a session recording program
32334 such as @command{script}, which is available on many Unix systems.
32335 Just run your @value{GDBN} session inside @command{script} and then
32336 include the @file{typescript} file with your bug report.
32338 Another way to record a @value{GDBN} session is to run @value{GDBN}
32339 inside Emacs and then save the entire buffer to a file.
32342 If you wish to suggest changes to the @value{GDBN} source, send us context
32343 diffs. If you even discuss something in the @value{GDBN} source, refer to
32344 it by context, not by line number.
32346 The line numbers in our development sources will not match those in your
32347 sources. Your line numbers would convey no useful information to us.
32351 Here are some things that are not necessary:
32355 A description of the envelope of the bug.
32357 Often people who encounter a bug spend a lot of time investigating
32358 which changes to the input file will make the bug go away and which
32359 changes will not affect it.
32361 This is often time consuming and not very useful, because the way we
32362 will find the bug is by running a single example under the debugger
32363 with breakpoints, not by pure deduction from a series of examples.
32364 We recommend that you save your time for something else.
32366 Of course, if you can find a simpler example to report @emph{instead}
32367 of the original one, that is a convenience for us. Errors in the
32368 output will be easier to spot, running under the debugger will take
32369 less time, and so on.
32371 However, simplification is not vital; if you do not want to do this,
32372 report the bug anyway and send us the entire test case you used.
32375 A patch for the bug.
32377 A patch for the bug does help us if it is a good one. But do not omit
32378 the necessary information, such as the test case, on the assumption that
32379 a patch is all we need. We might see problems with your patch and decide
32380 to fix the problem another way, or we might not understand it at all.
32382 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32383 construct an example that will make the program follow a certain path
32384 through the code. If you do not send us the example, we will not be able
32385 to construct one, so we will not be able to verify that the bug is fixed.
32387 And if we cannot understand what bug you are trying to fix, or why your
32388 patch should be an improvement, we will not install it. A test case will
32389 help us to understand.
32392 A guess about what the bug is or what it depends on.
32394 Such guesses are usually wrong. Even we cannot guess right about such
32395 things without first using the debugger to find the facts.
32398 @c The readline documentation is distributed with the readline code
32399 @c and consists of the two following files:
32402 @c Use -I with makeinfo to point to the appropriate directory,
32403 @c environment var TEXINPUTS with TeX.
32404 @ifclear SYSTEM_READLINE
32405 @include rluser.texi
32406 @include hsuser.texi
32410 @appendix In Memoriam
32412 The @value{GDBN} project mourns the loss of the following long-time
32417 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32418 to Free Software in general. Outside of @value{GDBN}, he was known in
32419 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32421 @item Michael Snyder
32422 Michael was one of the Global Maintainers of the @value{GDBN} project,
32423 with contributions recorded as early as 1996, until 2011. In addition
32424 to his day to day participation, he was a large driving force behind
32425 adding Reverse Debugging to @value{GDBN}.
32428 Beyond their technical contributions to the project, they were also
32429 enjoyable members of the Free Software Community. We will miss them.
32431 @node Formatting Documentation
32432 @appendix Formatting Documentation
32434 @cindex @value{GDBN} reference card
32435 @cindex reference card
32436 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32437 for printing with PostScript or Ghostscript, in the @file{gdb}
32438 subdirectory of the main source directory@footnote{In
32439 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32440 release.}. If you can use PostScript or Ghostscript with your printer,
32441 you can print the reference card immediately with @file{refcard.ps}.
32443 The release also includes the source for the reference card. You
32444 can format it, using @TeX{}, by typing:
32450 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32451 mode on US ``letter'' size paper;
32452 that is, on a sheet 11 inches wide by 8.5 inches
32453 high. You will need to specify this form of printing as an option to
32454 your @sc{dvi} output program.
32456 @cindex documentation
32458 All the documentation for @value{GDBN} comes as part of the machine-readable
32459 distribution. The documentation is written in Texinfo format, which is
32460 a documentation system that uses a single source file to produce both
32461 on-line information and a printed manual. You can use one of the Info
32462 formatting commands to create the on-line version of the documentation
32463 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32465 @value{GDBN} includes an already formatted copy of the on-line Info
32466 version of this manual in the @file{gdb} subdirectory. The main Info
32467 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32468 subordinate files matching @samp{gdb.info*} in the same directory. If
32469 necessary, you can print out these files, or read them with any editor;
32470 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32471 Emacs or the standalone @code{info} program, available as part of the
32472 @sc{gnu} Texinfo distribution.
32474 If you want to format these Info files yourself, you need one of the
32475 Info formatting programs, such as @code{texinfo-format-buffer} or
32478 If you have @code{makeinfo} installed, and are in the top level
32479 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32480 version @value{GDBVN}), you can make the Info file by typing:
32487 If you want to typeset and print copies of this manual, you need @TeX{},
32488 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32489 Texinfo definitions file.
32491 @TeX{} is a typesetting program; it does not print files directly, but
32492 produces output files called @sc{dvi} files. To print a typeset
32493 document, you need a program to print @sc{dvi} files. If your system
32494 has @TeX{} installed, chances are it has such a program. The precise
32495 command to use depends on your system; @kbd{lpr -d} is common; another
32496 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32497 require a file name without any extension or a @samp{.dvi} extension.
32499 @TeX{} also requires a macro definitions file called
32500 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32501 written in Texinfo format. On its own, @TeX{} cannot either read or
32502 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32503 and is located in the @file{gdb-@var{version-number}/texinfo}
32506 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32507 typeset and print this manual. First switch to the @file{gdb}
32508 subdirectory of the main source directory (for example, to
32509 @file{gdb-@value{GDBVN}/gdb}) and type:
32515 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32517 @node Installing GDB
32518 @appendix Installing @value{GDBN}
32519 @cindex installation
32522 * Requirements:: Requirements for building @value{GDBN}
32523 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32524 * Separate Objdir:: Compiling @value{GDBN} in another directory
32525 * Config Names:: Specifying names for hosts and targets
32526 * Configure Options:: Summary of options for configure
32527 * System-wide configuration:: Having a system-wide init file
32531 @section Requirements for Building @value{GDBN}
32532 @cindex building @value{GDBN}, requirements for
32534 Building @value{GDBN} requires various tools and packages to be available.
32535 Other packages will be used only if they are found.
32537 @heading Tools/Packages Necessary for Building @value{GDBN}
32539 @item ISO C90 compiler
32540 @value{GDBN} is written in ISO C90. It should be buildable with any
32541 working C90 compiler, e.g.@: GCC.
32545 @heading Tools/Packages Optional for Building @value{GDBN}
32549 @value{GDBN} can use the Expat XML parsing library. This library may be
32550 included with your operating system distribution; if it is not, you
32551 can get the latest version from @url{http://expat.sourceforge.net}.
32552 The @file{configure} script will search for this library in several
32553 standard locations; if it is installed in an unusual path, you can
32554 use the @option{--with-libexpat-prefix} option to specify its location.
32560 Remote protocol memory maps (@pxref{Memory Map Format})
32562 Target descriptions (@pxref{Target Descriptions})
32564 Remote shared library lists (@xref{Library List Format},
32565 or alternatively @pxref{Library List Format for SVR4 Targets})
32567 MS-Windows shared libraries (@pxref{Shared Libraries})
32569 Traceframe info (@pxref{Traceframe Info Format})
32573 @cindex compressed debug sections
32574 @value{GDBN} will use the @samp{zlib} library, if available, to read
32575 compressed debug sections. Some linkers, such as GNU gold, are capable
32576 of producing binaries with compressed debug sections. If @value{GDBN}
32577 is compiled with @samp{zlib}, it will be able to read the debug
32578 information in such binaries.
32580 The @samp{zlib} library is likely included with your operating system
32581 distribution; if it is not, you can get the latest version from
32582 @url{http://zlib.net}.
32585 @value{GDBN}'s features related to character sets (@pxref{Character
32586 Sets}) require a functioning @code{iconv} implementation. If you are
32587 on a GNU system, then this is provided by the GNU C Library. Some
32588 other systems also provide a working @code{iconv}.
32590 If @value{GDBN} is using the @code{iconv} program which is installed
32591 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32592 This is done with @option{--with-iconv-bin} which specifies the
32593 directory that contains the @code{iconv} program.
32595 On systems without @code{iconv}, you can install GNU Libiconv. If you
32596 have previously installed Libiconv, you can use the
32597 @option{--with-libiconv-prefix} option to configure.
32599 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32600 arrange to build Libiconv if a directory named @file{libiconv} appears
32601 in the top-most source directory. If Libiconv is built this way, and
32602 if the operating system does not provide a suitable @code{iconv}
32603 implementation, then the just-built library will automatically be used
32604 by @value{GDBN}. One easy way to set this up is to download GNU
32605 Libiconv, unpack it, and then rename the directory holding the
32606 Libiconv source code to @samp{libiconv}.
32609 @node Running Configure
32610 @section Invoking the @value{GDBN} @file{configure} Script
32611 @cindex configuring @value{GDBN}
32612 @value{GDBN} comes with a @file{configure} script that automates the process
32613 of preparing @value{GDBN} for installation; you can then use @code{make} to
32614 build the @code{gdb} program.
32616 @c irrelevant in info file; it's as current as the code it lives with.
32617 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32618 look at the @file{README} file in the sources; we may have improved the
32619 installation procedures since publishing this manual.}
32622 The @value{GDBN} distribution includes all the source code you need for
32623 @value{GDBN} in a single directory, whose name is usually composed by
32624 appending the version number to @samp{gdb}.
32626 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32627 @file{gdb-@value{GDBVN}} directory. That directory contains:
32630 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32631 script for configuring @value{GDBN} and all its supporting libraries
32633 @item gdb-@value{GDBVN}/gdb
32634 the source specific to @value{GDBN} itself
32636 @item gdb-@value{GDBVN}/bfd
32637 source for the Binary File Descriptor library
32639 @item gdb-@value{GDBVN}/include
32640 @sc{gnu} include files
32642 @item gdb-@value{GDBVN}/libiberty
32643 source for the @samp{-liberty} free software library
32645 @item gdb-@value{GDBVN}/opcodes
32646 source for the library of opcode tables and disassemblers
32648 @item gdb-@value{GDBVN}/readline
32649 source for the @sc{gnu} command-line interface
32651 @item gdb-@value{GDBVN}/glob
32652 source for the @sc{gnu} filename pattern-matching subroutine
32654 @item gdb-@value{GDBVN}/mmalloc
32655 source for the @sc{gnu} memory-mapped malloc package
32658 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32659 from the @file{gdb-@var{version-number}} source directory, which in
32660 this example is the @file{gdb-@value{GDBVN}} directory.
32662 First switch to the @file{gdb-@var{version-number}} source directory
32663 if you are not already in it; then run @file{configure}. Pass the
32664 identifier for the platform on which @value{GDBN} will run as an
32670 cd gdb-@value{GDBVN}
32671 ./configure @var{host}
32676 where @var{host} is an identifier such as @samp{sun4} or
32677 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32678 (You can often leave off @var{host}; @file{configure} tries to guess the
32679 correct value by examining your system.)
32681 Running @samp{configure @var{host}} and then running @code{make} builds the
32682 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32683 libraries, then @code{gdb} itself. The configured source files, and the
32684 binaries, are left in the corresponding source directories.
32687 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32688 system does not recognize this automatically when you run a different
32689 shell, you may need to run @code{sh} on it explicitly:
32692 sh configure @var{host}
32695 If you run @file{configure} from a directory that contains source
32696 directories for multiple libraries or programs, such as the
32697 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32699 creates configuration files for every directory level underneath (unless
32700 you tell it not to, with the @samp{--norecursion} option).
32702 You should run the @file{configure} script from the top directory in the
32703 source tree, the @file{gdb-@var{version-number}} directory. If you run
32704 @file{configure} from one of the subdirectories, you will configure only
32705 that subdirectory. That is usually not what you want. In particular,
32706 if you run the first @file{configure} from the @file{gdb} subdirectory
32707 of the @file{gdb-@var{version-number}} directory, you will omit the
32708 configuration of @file{bfd}, @file{readline}, and other sibling
32709 directories of the @file{gdb} subdirectory. This leads to build errors
32710 about missing include files such as @file{bfd/bfd.h}.
32712 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32713 However, you should make sure that the shell on your path (named by
32714 the @samp{SHELL} environment variable) is publicly readable. Remember
32715 that @value{GDBN} uses the shell to start your program---some systems refuse to
32716 let @value{GDBN} debug child processes whose programs are not readable.
32718 @node Separate Objdir
32719 @section Compiling @value{GDBN} in Another Directory
32721 If you want to run @value{GDBN} versions for several host or target machines,
32722 you need a different @code{gdb} compiled for each combination of
32723 host and target. @file{configure} is designed to make this easy by
32724 allowing you to generate each configuration in a separate subdirectory,
32725 rather than in the source directory. If your @code{make} program
32726 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32727 @code{make} in each of these directories builds the @code{gdb}
32728 program specified there.
32730 To build @code{gdb} in a separate directory, run @file{configure}
32731 with the @samp{--srcdir} option to specify where to find the source.
32732 (You also need to specify a path to find @file{configure}
32733 itself from your working directory. If the path to @file{configure}
32734 would be the same as the argument to @samp{--srcdir}, you can leave out
32735 the @samp{--srcdir} option; it is assumed.)
32737 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32738 separate directory for a Sun 4 like this:
32742 cd gdb-@value{GDBVN}
32745 ../gdb-@value{GDBVN}/configure sun4
32750 When @file{configure} builds a configuration using a remote source
32751 directory, it creates a tree for the binaries with the same structure
32752 (and using the same names) as the tree under the source directory. In
32753 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32754 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32755 @file{gdb-sun4/gdb}.
32757 Make sure that your path to the @file{configure} script has just one
32758 instance of @file{gdb} in it. If your path to @file{configure} looks
32759 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32760 one subdirectory of @value{GDBN}, not the whole package. This leads to
32761 build errors about missing include files such as @file{bfd/bfd.h}.
32763 One popular reason to build several @value{GDBN} configurations in separate
32764 directories is to configure @value{GDBN} for cross-compiling (where
32765 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32766 programs that run on another machine---the @dfn{target}).
32767 You specify a cross-debugging target by
32768 giving the @samp{--target=@var{target}} option to @file{configure}.
32770 When you run @code{make} to build a program or library, you must run
32771 it in a configured directory---whatever directory you were in when you
32772 called @file{configure} (or one of its subdirectories).
32774 The @code{Makefile} that @file{configure} generates in each source
32775 directory also runs recursively. If you type @code{make} in a source
32776 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32777 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32778 will build all the required libraries, and then build GDB.
32780 When you have multiple hosts or targets configured in separate
32781 directories, you can run @code{make} on them in parallel (for example,
32782 if they are NFS-mounted on each of the hosts); they will not interfere
32786 @section Specifying Names for Hosts and Targets
32788 The specifications used for hosts and targets in the @file{configure}
32789 script are based on a three-part naming scheme, but some short predefined
32790 aliases are also supported. The full naming scheme encodes three pieces
32791 of information in the following pattern:
32794 @var{architecture}-@var{vendor}-@var{os}
32797 For example, you can use the alias @code{sun4} as a @var{host} argument,
32798 or as the value for @var{target} in a @code{--target=@var{target}}
32799 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32801 The @file{configure} script accompanying @value{GDBN} does not provide
32802 any query facility to list all supported host and target names or
32803 aliases. @file{configure} calls the Bourne shell script
32804 @code{config.sub} to map abbreviations to full names; you can read the
32805 script, if you wish, or you can use it to test your guesses on
32806 abbreviations---for example:
32809 % sh config.sub i386-linux
32811 % sh config.sub alpha-linux
32812 alpha-unknown-linux-gnu
32813 % sh config.sub hp9k700
32815 % sh config.sub sun4
32816 sparc-sun-sunos4.1.1
32817 % sh config.sub sun3
32818 m68k-sun-sunos4.1.1
32819 % sh config.sub i986v
32820 Invalid configuration `i986v': machine `i986v' not recognized
32824 @code{config.sub} is also distributed in the @value{GDBN} source
32825 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32827 @node Configure Options
32828 @section @file{configure} Options
32830 Here is a summary of the @file{configure} options and arguments that
32831 are most often useful for building @value{GDBN}. @file{configure} also has
32832 several other options not listed here. @inforef{What Configure
32833 Does,,configure.info}, for a full explanation of @file{configure}.
32836 configure @r{[}--help@r{]}
32837 @r{[}--prefix=@var{dir}@r{]}
32838 @r{[}--exec-prefix=@var{dir}@r{]}
32839 @r{[}--srcdir=@var{dirname}@r{]}
32840 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32841 @r{[}--target=@var{target}@r{]}
32846 You may introduce options with a single @samp{-} rather than
32847 @samp{--} if you prefer; but you may abbreviate option names if you use
32852 Display a quick summary of how to invoke @file{configure}.
32854 @item --prefix=@var{dir}
32855 Configure the source to install programs and files under directory
32858 @item --exec-prefix=@var{dir}
32859 Configure the source to install programs under directory
32862 @c avoid splitting the warning from the explanation:
32864 @item --srcdir=@var{dirname}
32865 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32866 @code{make} that implements the @code{VPATH} feature.}@*
32867 Use this option to make configurations in directories separate from the
32868 @value{GDBN} source directories. Among other things, you can use this to
32869 build (or maintain) several configurations simultaneously, in separate
32870 directories. @file{configure} writes configuration-specific files in
32871 the current directory, but arranges for them to use the source in the
32872 directory @var{dirname}. @file{configure} creates directories under
32873 the working directory in parallel to the source directories below
32876 @item --norecursion
32877 Configure only the directory level where @file{configure} is executed; do not
32878 propagate configuration to subdirectories.
32880 @item --target=@var{target}
32881 Configure @value{GDBN} for cross-debugging programs running on the specified
32882 @var{target}. Without this option, @value{GDBN} is configured to debug
32883 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32885 There is no convenient way to generate a list of all available targets.
32887 @item @var{host} @dots{}
32888 Configure @value{GDBN} to run on the specified @var{host}.
32890 There is no convenient way to generate a list of all available hosts.
32893 There are many other options available as well, but they are generally
32894 needed for special purposes only.
32896 @node System-wide configuration
32897 @section System-wide configuration and settings
32898 @cindex system-wide init file
32900 @value{GDBN} can be configured to have a system-wide init file;
32901 this file will be read and executed at startup (@pxref{Startup, , What
32902 @value{GDBN} does during startup}).
32904 Here is the corresponding configure option:
32907 @item --with-system-gdbinit=@var{file}
32908 Specify that the default location of the system-wide init file is
32912 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32913 it may be subject to relocation. Two possible cases:
32917 If the default location of this init file contains @file{$prefix},
32918 it will be subject to relocation. Suppose that the configure options
32919 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32920 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32921 init file is looked for as @file{$install/etc/gdbinit} instead of
32922 @file{$prefix/etc/gdbinit}.
32925 By contrast, if the default location does not contain the prefix,
32926 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32927 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32928 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32929 wherever @value{GDBN} is installed.
32932 @node Maintenance Commands
32933 @appendix Maintenance Commands
32934 @cindex maintenance commands
32935 @cindex internal commands
32937 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32938 includes a number of commands intended for @value{GDBN} developers,
32939 that are not documented elsewhere in this manual. These commands are
32940 provided here for reference. (For commands that turn on debugging
32941 messages, see @ref{Debugging Output}.)
32944 @kindex maint agent
32945 @kindex maint agent-eval
32946 @item maint agent @var{expression}
32947 @itemx maint agent-eval @var{expression}
32948 Translate the given @var{expression} into remote agent bytecodes.
32949 This command is useful for debugging the Agent Expression mechanism
32950 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32951 expression useful for data collection, such as by tracepoints, while
32952 @samp{maint agent-eval} produces an expression that evaluates directly
32953 to a result. For instance, a collection expression for @code{globa +
32954 globb} will include bytecodes to record four bytes of memory at each
32955 of the addresses of @code{globa} and @code{globb}, while discarding
32956 the result of the addition, while an evaluation expression will do the
32957 addition and return the sum.
32959 @kindex maint info breakpoints
32960 @item @anchor{maint info breakpoints}maint info breakpoints
32961 Using the same format as @samp{info breakpoints}, display both the
32962 breakpoints you've set explicitly, and those @value{GDBN} is using for
32963 internal purposes. Internal breakpoints are shown with negative
32964 breakpoint numbers. The type column identifies what kind of breakpoint
32969 Normal, explicitly set breakpoint.
32972 Normal, explicitly set watchpoint.
32975 Internal breakpoint, used to handle correctly stepping through
32976 @code{longjmp} calls.
32978 @item longjmp resume
32979 Internal breakpoint at the target of a @code{longjmp}.
32982 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32985 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32988 Shared library events.
32992 @kindex set displaced-stepping
32993 @kindex show displaced-stepping
32994 @cindex displaced stepping support
32995 @cindex out-of-line single-stepping
32996 @item set displaced-stepping
32997 @itemx show displaced-stepping
32998 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32999 if the target supports it. Displaced stepping is a way to single-step
33000 over breakpoints without removing them from the inferior, by executing
33001 an out-of-line copy of the instruction that was originally at the
33002 breakpoint location. It is also known as out-of-line single-stepping.
33005 @item set displaced-stepping on
33006 If the target architecture supports it, @value{GDBN} will use
33007 displaced stepping to step over breakpoints.
33009 @item set displaced-stepping off
33010 @value{GDBN} will not use displaced stepping to step over breakpoints,
33011 even if such is supported by the target architecture.
33013 @cindex non-stop mode, and @samp{set displaced-stepping}
33014 @item set displaced-stepping auto
33015 This is the default mode. @value{GDBN} will use displaced stepping
33016 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33017 architecture supports displaced stepping.
33020 @kindex maint check-symtabs
33021 @item maint check-symtabs
33022 Check the consistency of psymtabs and symtabs.
33024 @kindex maint cplus first_component
33025 @item maint cplus first_component @var{name}
33026 Print the first C@t{++} class/namespace component of @var{name}.
33028 @kindex maint cplus namespace
33029 @item maint cplus namespace
33030 Print the list of possible C@t{++} namespaces.
33032 @kindex maint demangle
33033 @item maint demangle @var{name}
33034 Demangle a C@t{++} or Objective-C mangled @var{name}.
33036 @kindex maint deprecate
33037 @kindex maint undeprecate
33038 @cindex deprecated commands
33039 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33040 @itemx maint undeprecate @var{command}
33041 Deprecate or undeprecate the named @var{command}. Deprecated commands
33042 cause @value{GDBN} to issue a warning when you use them. The optional
33043 argument @var{replacement} says which newer command should be used in
33044 favor of the deprecated one; if it is given, @value{GDBN} will mention
33045 the replacement as part of the warning.
33047 @kindex maint dump-me
33048 @item maint dump-me
33049 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33050 Cause a fatal signal in the debugger and force it to dump its core.
33051 This is supported only on systems which support aborting a program
33052 with the @code{SIGQUIT} signal.
33054 @kindex maint internal-error
33055 @kindex maint internal-warning
33056 @item maint internal-error @r{[}@var{message-text}@r{]}
33057 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33058 Cause @value{GDBN} to call the internal function @code{internal_error}
33059 or @code{internal_warning} and hence behave as though an internal error
33060 or internal warning has been detected. In addition to reporting the
33061 internal problem, these functions give the user the opportunity to
33062 either quit @value{GDBN} or create a core file of the current
33063 @value{GDBN} session.
33065 These commands take an optional parameter @var{message-text} that is
33066 used as the text of the error or warning message.
33068 Here's an example of using @code{internal-error}:
33071 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33072 @dots{}/maint.c:121: internal-error: testing, 1, 2
33073 A problem internal to GDB has been detected. Further
33074 debugging may prove unreliable.
33075 Quit this debugging session? (y or n) @kbd{n}
33076 Create a core file? (y or n) @kbd{n}
33080 @cindex @value{GDBN} internal error
33081 @cindex internal errors, control of @value{GDBN} behavior
33083 @kindex maint set internal-error
33084 @kindex maint show internal-error
33085 @kindex maint set internal-warning
33086 @kindex maint show internal-warning
33087 @item maint set internal-error @var{action} [ask|yes|no]
33088 @itemx maint show internal-error @var{action}
33089 @itemx maint set internal-warning @var{action} [ask|yes|no]
33090 @itemx maint show internal-warning @var{action}
33091 When @value{GDBN} reports an internal problem (error or warning) it
33092 gives the user the opportunity to both quit @value{GDBN} and create a
33093 core file of the current @value{GDBN} session. These commands let you
33094 override the default behaviour for each particular @var{action},
33095 described in the table below.
33099 You can specify that @value{GDBN} should always (yes) or never (no)
33100 quit. The default is to ask the user what to do.
33103 You can specify that @value{GDBN} should always (yes) or never (no)
33104 create a core file. The default is to ask the user what to do.
33107 @kindex maint packet
33108 @item maint packet @var{text}
33109 If @value{GDBN} is talking to an inferior via the serial protocol,
33110 then this command sends the string @var{text} to the inferior, and
33111 displays the response packet. @value{GDBN} supplies the initial
33112 @samp{$} character, the terminating @samp{#} character, and the
33115 @kindex maint print architecture
33116 @item maint print architecture @r{[}@var{file}@r{]}
33117 Print the entire architecture configuration. The optional argument
33118 @var{file} names the file where the output goes.
33120 @kindex maint print c-tdesc
33121 @item maint print c-tdesc
33122 Print the current target description (@pxref{Target Descriptions}) as
33123 a C source file. The created source file can be used in @value{GDBN}
33124 when an XML parser is not available to parse the description.
33126 @kindex maint print dummy-frames
33127 @item maint print dummy-frames
33128 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33131 (@value{GDBP}) @kbd{b add}
33133 (@value{GDBP}) @kbd{print add(2,3)}
33134 Breakpoint 2, add (a=2, b=3) at @dots{}
33136 The program being debugged stopped while in a function called from GDB.
33138 (@value{GDBP}) @kbd{maint print dummy-frames}
33139 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33140 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33141 call_lo=0x01014000 call_hi=0x01014001
33145 Takes an optional file parameter.
33147 @kindex maint print registers
33148 @kindex maint print raw-registers
33149 @kindex maint print cooked-registers
33150 @kindex maint print register-groups
33151 @kindex maint print remote-registers
33152 @item maint print registers @r{[}@var{file}@r{]}
33153 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33154 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33155 @itemx maint print register-groups @r{[}@var{file}@r{]}
33156 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33157 Print @value{GDBN}'s internal register data structures.
33159 The command @code{maint print raw-registers} includes the contents of
33160 the raw register cache; the command @code{maint print
33161 cooked-registers} includes the (cooked) value of all registers,
33162 including registers which aren't available on the target nor visible
33163 to user; the command @code{maint print register-groups} includes the
33164 groups that each register is a member of; and the command @code{maint
33165 print remote-registers} includes the remote target's register numbers
33166 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33167 @value{GDBN} Internals}.
33169 These commands take an optional parameter, a file name to which to
33170 write the information.
33172 @kindex maint print reggroups
33173 @item maint print reggroups @r{[}@var{file}@r{]}
33174 Print @value{GDBN}'s internal register group data structures. The
33175 optional argument @var{file} tells to what file to write the
33178 The register groups info looks like this:
33181 (@value{GDBP}) @kbd{maint print reggroups}
33194 This command forces @value{GDBN} to flush its internal register cache.
33196 @kindex maint print objfiles
33197 @cindex info for known object files
33198 @item maint print objfiles
33199 Print a dump of all known object files. For each object file, this
33200 command prints its name, address in memory, and all of its psymtabs
33203 @kindex maint print section-scripts
33204 @cindex info for known .debug_gdb_scripts-loaded scripts
33205 @item maint print section-scripts [@var{regexp}]
33206 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33207 If @var{regexp} is specified, only print scripts loaded by object files
33208 matching @var{regexp}.
33209 For each script, this command prints its name as specified in the objfile,
33210 and the full path if known.
33211 @xref{.debug_gdb_scripts section}.
33213 @kindex maint print statistics
33214 @cindex bcache statistics
33215 @item maint print statistics
33216 This command prints, for each object file in the program, various data
33217 about that object file followed by the byte cache (@dfn{bcache})
33218 statistics for the object file. The objfile data includes the number
33219 of minimal, partial, full, and stabs symbols, the number of types
33220 defined by the objfile, the number of as yet unexpanded psym tables,
33221 the number of line tables and string tables, and the amount of memory
33222 used by the various tables. The bcache statistics include the counts,
33223 sizes, and counts of duplicates of all and unique objects, max,
33224 average, and median entry size, total memory used and its overhead and
33225 savings, and various measures of the hash table size and chain
33228 @kindex maint print target-stack
33229 @cindex target stack description
33230 @item maint print target-stack
33231 A @dfn{target} is an interface between the debugger and a particular
33232 kind of file or process. Targets can be stacked in @dfn{strata},
33233 so that more than one target can potentially respond to a request.
33234 In particular, memory accesses will walk down the stack of targets
33235 until they find a target that is interested in handling that particular
33238 This command prints a short description of each layer that was pushed on
33239 the @dfn{target stack}, starting from the top layer down to the bottom one.
33241 @kindex maint print type
33242 @cindex type chain of a data type
33243 @item maint print type @var{expr}
33244 Print the type chain for a type specified by @var{expr}. The argument
33245 can be either a type name or a symbol. If it is a symbol, the type of
33246 that symbol is described. The type chain produced by this command is
33247 a recursive definition of the data type as stored in @value{GDBN}'s
33248 data structures, including its flags and contained types.
33250 @kindex maint set dwarf2 always-disassemble
33251 @kindex maint show dwarf2 always-disassemble
33252 @item maint set dwarf2 always-disassemble
33253 @item maint show dwarf2 always-disassemble
33254 Control the behavior of @code{info address} when using DWARF debugging
33257 The default is @code{off}, which means that @value{GDBN} should try to
33258 describe a variable's location in an easily readable format. When
33259 @code{on}, @value{GDBN} will instead display the DWARF location
33260 expression in an assembly-like format. Note that some locations are
33261 too complex for @value{GDBN} to describe simply; in this case you will
33262 always see the disassembly form.
33264 Here is an example of the resulting disassembly:
33267 (gdb) info addr argc
33268 Symbol "argc" is a complex DWARF expression:
33272 For more information on these expressions, see
33273 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33275 @kindex maint set dwarf2 max-cache-age
33276 @kindex maint show dwarf2 max-cache-age
33277 @item maint set dwarf2 max-cache-age
33278 @itemx maint show dwarf2 max-cache-age
33279 Control the DWARF 2 compilation unit cache.
33281 @cindex DWARF 2 compilation units cache
33282 In object files with inter-compilation-unit references, such as those
33283 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33284 reader needs to frequently refer to previously read compilation units.
33285 This setting controls how long a compilation unit will remain in the
33286 cache if it is not referenced. A higher limit means that cached
33287 compilation units will be stored in memory longer, and more total
33288 memory will be used. Setting it to zero disables caching, which will
33289 slow down @value{GDBN} startup, but reduce memory consumption.
33291 @kindex maint set profile
33292 @kindex maint show profile
33293 @cindex profiling GDB
33294 @item maint set profile
33295 @itemx maint show profile
33296 Control profiling of @value{GDBN}.
33298 Profiling will be disabled until you use the @samp{maint set profile}
33299 command to enable it. When you enable profiling, the system will begin
33300 collecting timing and execution count data; when you disable profiling or
33301 exit @value{GDBN}, the results will be written to a log file. Remember that
33302 if you use profiling, @value{GDBN} will overwrite the profiling log file
33303 (often called @file{gmon.out}). If you have a record of important profiling
33304 data in a @file{gmon.out} file, be sure to move it to a safe location.
33306 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33307 compiled with the @samp{-pg} compiler option.
33309 @kindex maint set show-debug-regs
33310 @kindex maint show show-debug-regs
33311 @cindex hardware debug registers
33312 @item maint set show-debug-regs
33313 @itemx maint show show-debug-regs
33314 Control whether to show variables that mirror the hardware debug
33315 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33316 enabled, the debug registers values are shown when @value{GDBN} inserts or
33317 removes a hardware breakpoint or watchpoint, and when the inferior
33318 triggers a hardware-assisted breakpoint or watchpoint.
33320 @kindex maint set show-all-tib
33321 @kindex maint show show-all-tib
33322 @item maint set show-all-tib
33323 @itemx maint show show-all-tib
33324 Control whether to show all non zero areas within a 1k block starting
33325 at thread local base, when using the @samp{info w32 thread-information-block}
33328 @kindex maint space
33329 @cindex memory used by commands
33331 Control whether to display memory usage for each command. If set to a
33332 nonzero value, @value{GDBN} will display how much memory each command
33333 took, following the command's own output. This can also be requested
33334 by invoking @value{GDBN} with the @option{--statistics} command-line
33335 switch (@pxref{Mode Options}).
33338 @cindex time of command execution
33340 Control whether to display the execution time of @value{GDBN} for each command.
33341 If set to a nonzero value, @value{GDBN} will display how much time it
33342 took to execute each command, following the command's own output.
33343 Both CPU time and wallclock time are printed.
33344 Printing both is useful when trying to determine whether the cost is
33345 CPU or, e.g., disk/network, latency.
33346 Note that the CPU time printed is for @value{GDBN} only, it does not include
33347 the execution time of the inferior because there's no mechanism currently
33348 to compute how much time was spent by @value{GDBN} and how much time was
33349 spent by the program been debugged.
33350 This can also be requested by invoking @value{GDBN} with the
33351 @option{--statistics} command-line switch (@pxref{Mode Options}).
33353 @kindex maint translate-address
33354 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33355 Find the symbol stored at the location specified by the address
33356 @var{addr} and an optional section name @var{section}. If found,
33357 @value{GDBN} prints the name of the closest symbol and an offset from
33358 the symbol's location to the specified address. This is similar to
33359 the @code{info address} command (@pxref{Symbols}), except that this
33360 command also allows to find symbols in other sections.
33362 If section was not specified, the section in which the symbol was found
33363 is also printed. For dynamically linked executables, the name of
33364 executable or shared library containing the symbol is printed as well.
33368 The following command is useful for non-interactive invocations of
33369 @value{GDBN}, such as in the test suite.
33372 @item set watchdog @var{nsec}
33373 @kindex set watchdog
33374 @cindex watchdog timer
33375 @cindex timeout for commands
33376 Set the maximum number of seconds @value{GDBN} will wait for the
33377 target operation to finish. If this time expires, @value{GDBN}
33378 reports and error and the command is aborted.
33380 @item show watchdog
33381 Show the current setting of the target wait timeout.
33384 @node Remote Protocol
33385 @appendix @value{GDBN} Remote Serial Protocol
33390 * Stop Reply Packets::
33391 * General Query Packets::
33392 * Architecture-Specific Protocol Details::
33393 * Tracepoint Packets::
33394 * Host I/O Packets::
33396 * Notification Packets::
33397 * Remote Non-Stop::
33398 * Packet Acknowledgment::
33400 * File-I/O Remote Protocol Extension::
33401 * Library List Format::
33402 * Library List Format for SVR4 Targets::
33403 * Memory Map Format::
33404 * Thread List Format::
33405 * Traceframe Info Format::
33411 There may be occasions when you need to know something about the
33412 protocol---for example, if there is only one serial port to your target
33413 machine, you might want your program to do something special if it
33414 recognizes a packet meant for @value{GDBN}.
33416 In the examples below, @samp{->} and @samp{<-} are used to indicate
33417 transmitted and received data, respectively.
33419 @cindex protocol, @value{GDBN} remote serial
33420 @cindex serial protocol, @value{GDBN} remote
33421 @cindex remote serial protocol
33422 All @value{GDBN} commands and responses (other than acknowledgments
33423 and notifications, see @ref{Notification Packets}) are sent as a
33424 @var{packet}. A @var{packet} is introduced with the character
33425 @samp{$}, the actual @var{packet-data}, and the terminating character
33426 @samp{#} followed by a two-digit @var{checksum}:
33429 @code{$}@var{packet-data}@code{#}@var{checksum}
33433 @cindex checksum, for @value{GDBN} remote
33435 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33436 characters between the leading @samp{$} and the trailing @samp{#} (an
33437 eight bit unsigned checksum).
33439 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33440 specification also included an optional two-digit @var{sequence-id}:
33443 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33446 @cindex sequence-id, for @value{GDBN} remote
33448 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33449 has never output @var{sequence-id}s. Stubs that handle packets added
33450 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33452 When either the host or the target machine receives a packet, the first
33453 response expected is an acknowledgment: either @samp{+} (to indicate
33454 the package was received correctly) or @samp{-} (to request
33458 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33463 The @samp{+}/@samp{-} acknowledgments can be disabled
33464 once a connection is established.
33465 @xref{Packet Acknowledgment}, for details.
33467 The host (@value{GDBN}) sends @var{command}s, and the target (the
33468 debugging stub incorporated in your program) sends a @var{response}. In
33469 the case of step and continue @var{command}s, the response is only sent
33470 when the operation has completed, and the target has again stopped all
33471 threads in all attached processes. This is the default all-stop mode
33472 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33473 execution mode; see @ref{Remote Non-Stop}, for details.
33475 @var{packet-data} consists of a sequence of characters with the
33476 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33479 @cindex remote protocol, field separator
33480 Fields within the packet should be separated using @samp{,} @samp{;} or
33481 @samp{:}. Except where otherwise noted all numbers are represented in
33482 @sc{hex} with leading zeros suppressed.
33484 Implementors should note that prior to @value{GDBN} 5.0, the character
33485 @samp{:} could not appear as the third character in a packet (as it
33486 would potentially conflict with the @var{sequence-id}).
33488 @cindex remote protocol, binary data
33489 @anchor{Binary Data}
33490 Binary data in most packets is encoded either as two hexadecimal
33491 digits per byte of binary data. This allowed the traditional remote
33492 protocol to work over connections which were only seven-bit clean.
33493 Some packets designed more recently assume an eight-bit clean
33494 connection, and use a more efficient encoding to send and receive
33497 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33498 as an escape character. Any escaped byte is transmitted as the escape
33499 character followed by the original character XORed with @code{0x20}.
33500 For example, the byte @code{0x7d} would be transmitted as the two
33501 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33502 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33503 @samp{@}}) must always be escaped. Responses sent by the stub
33504 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33505 is not interpreted as the start of a run-length encoded sequence
33508 Response @var{data} can be run-length encoded to save space.
33509 Run-length encoding replaces runs of identical characters with one
33510 instance of the repeated character, followed by a @samp{*} and a
33511 repeat count. The repeat count is itself sent encoded, to avoid
33512 binary characters in @var{data}: a value of @var{n} is sent as
33513 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33514 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33515 code 32) for a repeat count of 3. (This is because run-length
33516 encoding starts to win for counts 3 or more.) Thus, for example,
33517 @samp{0* } is a run-length encoding of ``0000'': the space character
33518 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33521 The printable characters @samp{#} and @samp{$} or with a numeric value
33522 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33523 seven repeats (@samp{$}) can be expanded using a repeat count of only
33524 five (@samp{"}). For example, @samp{00000000} can be encoded as
33527 The error response returned for some packets includes a two character
33528 error number. That number is not well defined.
33530 @cindex empty response, for unsupported packets
33531 For any @var{command} not supported by the stub, an empty response
33532 (@samp{$#00}) should be returned. That way it is possible to extend the
33533 protocol. A newer @value{GDBN} can tell if a packet is supported based
33536 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33537 commands for register access, and the @samp{m} and @samp{M} commands
33538 for memory access. Stubs that only control single-threaded targets
33539 can implement run control with the @samp{c} (continue), and @samp{s}
33540 (step) commands. Stubs that support multi-threading targets should
33541 support the @samp{vCont} command. All other commands are optional.
33546 The following table provides a complete list of all currently defined
33547 @var{command}s and their corresponding response @var{data}.
33548 @xref{File-I/O Remote Protocol Extension}, for details about the File
33549 I/O extension of the remote protocol.
33551 Each packet's description has a template showing the packet's overall
33552 syntax, followed by an explanation of the packet's meaning. We
33553 include spaces in some of the templates for clarity; these are not
33554 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33555 separate its components. For example, a template like @samp{foo
33556 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33557 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33558 @var{baz}. @value{GDBN} does not transmit a space character between the
33559 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33562 @cindex @var{thread-id}, in remote protocol
33563 @anchor{thread-id syntax}
33564 Several packets and replies include a @var{thread-id} field to identify
33565 a thread. Normally these are positive numbers with a target-specific
33566 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33567 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33570 In addition, the remote protocol supports a multiprocess feature in
33571 which the @var{thread-id} syntax is extended to optionally include both
33572 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33573 The @var{pid} (process) and @var{tid} (thread) components each have the
33574 format described above: a positive number with target-specific
33575 interpretation formatted as a big-endian hex string, literal @samp{-1}
33576 to indicate all processes or threads (respectively), or @samp{0} to
33577 indicate an arbitrary process or thread. Specifying just a process, as
33578 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33579 error to specify all processes but a specific thread, such as
33580 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33581 for those packets and replies explicitly documented to include a process
33582 ID, rather than a @var{thread-id}.
33584 The multiprocess @var{thread-id} syntax extensions are only used if both
33585 @value{GDBN} and the stub report support for the @samp{multiprocess}
33586 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33589 Note that all packet forms beginning with an upper- or lower-case
33590 letter, other than those described here, are reserved for future use.
33592 Here are the packet descriptions.
33597 @cindex @samp{!} packet
33598 @anchor{extended mode}
33599 Enable extended mode. In extended mode, the remote server is made
33600 persistent. The @samp{R} packet is used to restart the program being
33606 The remote target both supports and has enabled extended mode.
33610 @cindex @samp{?} packet
33611 Indicate the reason the target halted. The reply is the same as for
33612 step and continue. This packet has a special interpretation when the
33613 target is in non-stop mode; see @ref{Remote Non-Stop}.
33616 @xref{Stop Reply Packets}, for the reply specifications.
33618 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33619 @cindex @samp{A} packet
33620 Initialized @code{argv[]} array passed into program. @var{arglen}
33621 specifies the number of bytes in the hex encoded byte stream
33622 @var{arg}. See @code{gdbserver} for more details.
33627 The arguments were set.
33633 @cindex @samp{b} packet
33634 (Don't use this packet; its behavior is not well-defined.)
33635 Change the serial line speed to @var{baud}.
33637 JTC: @emph{When does the transport layer state change? When it's
33638 received, or after the ACK is transmitted. In either case, there are
33639 problems if the command or the acknowledgment packet is dropped.}
33641 Stan: @emph{If people really wanted to add something like this, and get
33642 it working for the first time, they ought to modify ser-unix.c to send
33643 some kind of out-of-band message to a specially-setup stub and have the
33644 switch happen "in between" packets, so that from remote protocol's point
33645 of view, nothing actually happened.}
33647 @item B @var{addr},@var{mode}
33648 @cindex @samp{B} packet
33649 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33650 breakpoint at @var{addr}.
33652 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33653 (@pxref{insert breakpoint or watchpoint packet}).
33655 @cindex @samp{bc} packet
33658 Backward continue. Execute the target system in reverse. No parameter.
33659 @xref{Reverse Execution}, for more information.
33662 @xref{Stop Reply Packets}, for the reply specifications.
33664 @cindex @samp{bs} packet
33667 Backward single step. Execute one instruction in reverse. No parameter.
33668 @xref{Reverse Execution}, for more information.
33671 @xref{Stop Reply Packets}, for the reply specifications.
33673 @item c @r{[}@var{addr}@r{]}
33674 @cindex @samp{c} packet
33675 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33676 resume at current address.
33678 This packet is deprecated for multi-threading support. @xref{vCont
33682 @xref{Stop Reply Packets}, for the reply specifications.
33684 @item C @var{sig}@r{[};@var{addr}@r{]}
33685 @cindex @samp{C} packet
33686 Continue with signal @var{sig} (hex signal number). If
33687 @samp{;@var{addr}} is omitted, resume at same address.
33689 This packet is deprecated for multi-threading support. @xref{vCont
33693 @xref{Stop Reply Packets}, for the reply specifications.
33696 @cindex @samp{d} packet
33699 Don't use this packet; instead, define a general set packet
33700 (@pxref{General Query Packets}).
33704 @cindex @samp{D} packet
33705 The first form of the packet is used to detach @value{GDBN} from the
33706 remote system. It is sent to the remote target
33707 before @value{GDBN} disconnects via the @code{detach} command.
33709 The second form, including a process ID, is used when multiprocess
33710 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33711 detach only a specific process. The @var{pid} is specified as a
33712 big-endian hex string.
33722 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33723 @cindex @samp{F} packet
33724 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33725 This is part of the File-I/O protocol extension. @xref{File-I/O
33726 Remote Protocol Extension}, for the specification.
33729 @anchor{read registers packet}
33730 @cindex @samp{g} packet
33731 Read general registers.
33735 @item @var{XX@dots{}}
33736 Each byte of register data is described by two hex digits. The bytes
33737 with the register are transmitted in target byte order. The size of
33738 each register and their position within the @samp{g} packet are
33739 determined by the @value{GDBN} internal gdbarch functions
33740 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33741 specification of several standard @samp{g} packets is specified below.
33743 When reading registers from a trace frame (@pxref{Analyze Collected
33744 Data,,Using the Collected Data}), the stub may also return a string of
33745 literal @samp{x}'s in place of the register data digits, to indicate
33746 that the corresponding register has not been collected, thus its value
33747 is unavailable. For example, for an architecture with 4 registers of
33748 4 bytes each, the following reply indicates to @value{GDBN} that
33749 registers 0 and 2 have not been collected, while registers 1 and 3
33750 have been collected, and both have zero value:
33754 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33761 @item G @var{XX@dots{}}
33762 @cindex @samp{G} packet
33763 Write general registers. @xref{read registers packet}, for a
33764 description of the @var{XX@dots{}} data.
33774 @item H @var{op} @var{thread-id}
33775 @cindex @samp{H} packet
33776 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33777 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33778 it should be @samp{c} for step and continue operations (note that this
33779 is deprecated, supporting the @samp{vCont} command is a better
33780 option), @samp{g} for other operations. The thread designator
33781 @var{thread-id} has the format and interpretation described in
33782 @ref{thread-id syntax}.
33793 @c 'H': How restrictive (or permissive) is the thread model. If a
33794 @c thread is selected and stopped, are other threads allowed
33795 @c to continue to execute? As I mentioned above, I think the
33796 @c semantics of each command when a thread is selected must be
33797 @c described. For example:
33799 @c 'g': If the stub supports threads and a specific thread is
33800 @c selected, returns the register block from that thread;
33801 @c otherwise returns current registers.
33803 @c 'G' If the stub supports threads and a specific thread is
33804 @c selected, sets the registers of the register block of
33805 @c that thread; otherwise sets current registers.
33807 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33808 @anchor{cycle step packet}
33809 @cindex @samp{i} packet
33810 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33811 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33812 step starting at that address.
33815 @cindex @samp{I} packet
33816 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33820 @cindex @samp{k} packet
33823 FIXME: @emph{There is no description of how to operate when a specific
33824 thread context has been selected (i.e.@: does 'k' kill only that
33827 @item m @var{addr},@var{length}
33828 @cindex @samp{m} packet
33829 Read @var{length} bytes of memory starting at address @var{addr}.
33830 Note that @var{addr} may not be aligned to any particular boundary.
33832 The stub need not use any particular size or alignment when gathering
33833 data from memory for the response; even if @var{addr} is word-aligned
33834 and @var{length} is a multiple of the word size, the stub is free to
33835 use byte accesses, or not. For this reason, this packet may not be
33836 suitable for accessing memory-mapped I/O devices.
33837 @cindex alignment of remote memory accesses
33838 @cindex size of remote memory accesses
33839 @cindex memory, alignment and size of remote accesses
33843 @item @var{XX@dots{}}
33844 Memory contents; each byte is transmitted as a two-digit hexadecimal
33845 number. The reply may contain fewer bytes than requested if the
33846 server was able to read only part of the region of memory.
33851 @item M @var{addr},@var{length}:@var{XX@dots{}}
33852 @cindex @samp{M} packet
33853 Write @var{length} bytes of memory starting at address @var{addr}.
33854 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33855 hexadecimal number.
33862 for an error (this includes the case where only part of the data was
33867 @cindex @samp{p} packet
33868 Read the value of register @var{n}; @var{n} is in hex.
33869 @xref{read registers packet}, for a description of how the returned
33870 register value is encoded.
33874 @item @var{XX@dots{}}
33875 the register's value
33879 Indicating an unrecognized @var{query}.
33882 @item P @var{n@dots{}}=@var{r@dots{}}
33883 @anchor{write register packet}
33884 @cindex @samp{P} packet
33885 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33886 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33887 digits for each byte in the register (target byte order).
33897 @item q @var{name} @var{params}@dots{}
33898 @itemx Q @var{name} @var{params}@dots{}
33899 @cindex @samp{q} packet
33900 @cindex @samp{Q} packet
33901 General query (@samp{q}) and set (@samp{Q}). These packets are
33902 described fully in @ref{General Query Packets}.
33905 @cindex @samp{r} packet
33906 Reset the entire system.
33908 Don't use this packet; use the @samp{R} packet instead.
33911 @cindex @samp{R} packet
33912 Restart the program being debugged. @var{XX}, while needed, is ignored.
33913 This packet is only available in extended mode (@pxref{extended mode}).
33915 The @samp{R} packet has no reply.
33917 @item s @r{[}@var{addr}@r{]}
33918 @cindex @samp{s} packet
33919 Single step. @var{addr} is the address at which to resume. If
33920 @var{addr} is omitted, resume at same address.
33922 This packet is deprecated for multi-threading support. @xref{vCont
33926 @xref{Stop Reply Packets}, for the reply specifications.
33928 @item S @var{sig}@r{[};@var{addr}@r{]}
33929 @anchor{step with signal packet}
33930 @cindex @samp{S} packet
33931 Step with signal. This is analogous to the @samp{C} packet, but
33932 requests a single-step, rather than a normal resumption of execution.
33934 This packet is deprecated for multi-threading support. @xref{vCont
33938 @xref{Stop Reply Packets}, for the reply specifications.
33940 @item t @var{addr}:@var{PP},@var{MM}
33941 @cindex @samp{t} packet
33942 Search backwards starting at address @var{addr} for a match with pattern
33943 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33944 @var{addr} must be at least 3 digits.
33946 @item T @var{thread-id}
33947 @cindex @samp{T} packet
33948 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33953 thread is still alive
33959 Packets starting with @samp{v} are identified by a multi-letter name,
33960 up to the first @samp{;} or @samp{?} (or the end of the packet).
33962 @item vAttach;@var{pid}
33963 @cindex @samp{vAttach} packet
33964 Attach to a new process with the specified process ID @var{pid}.
33965 The process ID is a
33966 hexadecimal integer identifying the process. In all-stop mode, all
33967 threads in the attached process are stopped; in non-stop mode, it may be
33968 attached without being stopped if that is supported by the target.
33970 @c In non-stop mode, on a successful vAttach, the stub should set the
33971 @c current thread to a thread of the newly-attached process. After
33972 @c attaching, GDB queries for the attached process's thread ID with qC.
33973 @c Also note that, from a user perspective, whether or not the
33974 @c target is stopped on attach in non-stop mode depends on whether you
33975 @c use the foreground or background version of the attach command, not
33976 @c on what vAttach does; GDB does the right thing with respect to either
33977 @c stopping or restarting threads.
33979 This packet is only available in extended mode (@pxref{extended mode}).
33985 @item @r{Any stop packet}
33986 for success in all-stop mode (@pxref{Stop Reply Packets})
33988 for success in non-stop mode (@pxref{Remote Non-Stop})
33991 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33992 @cindex @samp{vCont} packet
33993 @anchor{vCont packet}
33994 Resume the inferior, specifying different actions for each thread.
33995 If an action is specified with no @var{thread-id}, then it is applied to any
33996 threads that don't have a specific action specified; if no default action is
33997 specified then other threads should remain stopped in all-stop mode and
33998 in their current state in non-stop mode.
33999 Specifying multiple
34000 default actions is an error; specifying no actions is also an error.
34001 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34003 Currently supported actions are:
34009 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34013 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34018 The optional argument @var{addr} normally associated with the
34019 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34020 not supported in @samp{vCont}.
34022 The @samp{t} action is only relevant in non-stop mode
34023 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34024 A stop reply should be generated for any affected thread not already stopped.
34025 When a thread is stopped by means of a @samp{t} action,
34026 the corresponding stop reply should indicate that the thread has stopped with
34027 signal @samp{0}, regardless of whether the target uses some other signal
34028 as an implementation detail.
34031 @xref{Stop Reply Packets}, for the reply specifications.
34034 @cindex @samp{vCont?} packet
34035 Request a list of actions supported by the @samp{vCont} packet.
34039 @item vCont@r{[};@var{action}@dots{}@r{]}
34040 The @samp{vCont} packet is supported. Each @var{action} is a supported
34041 command in the @samp{vCont} packet.
34043 The @samp{vCont} packet is not supported.
34046 @item vFile:@var{operation}:@var{parameter}@dots{}
34047 @cindex @samp{vFile} packet
34048 Perform a file operation on the target system. For details,
34049 see @ref{Host I/O Packets}.
34051 @item vFlashErase:@var{addr},@var{length}
34052 @cindex @samp{vFlashErase} packet
34053 Direct the stub to erase @var{length} bytes of flash starting at
34054 @var{addr}. The region may enclose any number of flash blocks, but
34055 its start and end must fall on block boundaries, as indicated by the
34056 flash block size appearing in the memory map (@pxref{Memory Map
34057 Format}). @value{GDBN} groups flash memory programming operations
34058 together, and sends a @samp{vFlashDone} request after each group; the
34059 stub is allowed to delay erase operation until the @samp{vFlashDone}
34060 packet is received.
34062 The stub must support @samp{vCont} if it reports support for
34063 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34064 this case @samp{vCont} actions can be specified to apply to all threads
34065 in a process by using the @samp{p@var{pid}.-1} form of the
34076 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34077 @cindex @samp{vFlashWrite} packet
34078 Direct the stub to write data to flash address @var{addr}. The data
34079 is passed in binary form using the same encoding as for the @samp{X}
34080 packet (@pxref{Binary Data}). The memory ranges specified by
34081 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34082 not overlap, and must appear in order of increasing addresses
34083 (although @samp{vFlashErase} packets for higher addresses may already
34084 have been received; the ordering is guaranteed only between
34085 @samp{vFlashWrite} packets). If a packet writes to an address that was
34086 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34087 target-specific method, the results are unpredictable.
34095 for vFlashWrite addressing non-flash memory
34101 @cindex @samp{vFlashDone} packet
34102 Indicate to the stub that flash programming operation is finished.
34103 The stub is permitted to delay or batch the effects of a group of
34104 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34105 @samp{vFlashDone} packet is received. The contents of the affected
34106 regions of flash memory are unpredictable until the @samp{vFlashDone}
34107 request is completed.
34109 @item vKill;@var{pid}
34110 @cindex @samp{vKill} packet
34111 Kill the process with the specified process ID. @var{pid} is a
34112 hexadecimal integer identifying the process. This packet is used in
34113 preference to @samp{k} when multiprocess protocol extensions are
34114 supported; see @ref{multiprocess extensions}.
34124 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34125 @cindex @samp{vRun} packet
34126 Run the program @var{filename}, passing it each @var{argument} on its
34127 command line. The file and arguments are hex-encoded strings. If
34128 @var{filename} is an empty string, the stub may use a default program
34129 (e.g.@: the last program run). The program is created in the stopped
34132 @c FIXME: What about non-stop mode?
34134 This packet is only available in extended mode (@pxref{extended mode}).
34140 @item @r{Any stop packet}
34141 for success (@pxref{Stop Reply Packets})
34145 @anchor{vStopped packet}
34146 @cindex @samp{vStopped} packet
34148 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34149 reply and prompt for the stub to report another one.
34153 @item @r{Any stop packet}
34154 if there is another unreported stop event (@pxref{Stop Reply Packets})
34156 if there are no unreported stop events
34159 @item X @var{addr},@var{length}:@var{XX@dots{}}
34161 @cindex @samp{X} packet
34162 Write data to memory, where the data is transmitted in binary.
34163 @var{addr} is address, @var{length} is number of bytes,
34164 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34174 @item z @var{type},@var{addr},@var{kind}
34175 @itemx Z @var{type},@var{addr},@var{kind}
34176 @anchor{insert breakpoint or watchpoint packet}
34177 @cindex @samp{z} packet
34178 @cindex @samp{Z} packets
34179 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34180 watchpoint starting at address @var{address} of kind @var{kind}.
34182 Each breakpoint and watchpoint packet @var{type} is documented
34185 @emph{Implementation notes: A remote target shall return an empty string
34186 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34187 remote target shall support either both or neither of a given
34188 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34189 avoid potential problems with duplicate packets, the operations should
34190 be implemented in an idempotent way.}
34192 @item z0,@var{addr},@var{kind}
34193 @itemx Z0,@var{addr},@var{kind}
34194 @cindex @samp{z0} packet
34195 @cindex @samp{Z0} packet
34196 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34197 @var{addr} of type @var{kind}.
34199 A memory breakpoint is implemented by replacing the instruction at
34200 @var{addr} with a software breakpoint or trap instruction. The
34201 @var{kind} is target-specific and typically indicates the size of
34202 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34203 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34204 architectures have additional meanings for @var{kind};
34205 see @ref{Architecture-Specific Protocol Details}.
34207 @emph{Implementation note: It is possible for a target to copy or move
34208 code that contains memory breakpoints (e.g., when implementing
34209 overlays). The behavior of this packet, in the presence of such a
34210 target, is not defined.}
34222 @item z1,@var{addr},@var{kind}
34223 @itemx Z1,@var{addr},@var{kind}
34224 @cindex @samp{z1} packet
34225 @cindex @samp{Z1} packet
34226 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34227 address @var{addr}.
34229 A hardware breakpoint is implemented using a mechanism that is not
34230 dependant on being able to modify the target's memory. @var{kind}
34231 has the same meaning as in @samp{Z0} packets.
34233 @emph{Implementation note: A hardware breakpoint is not affected by code
34246 @item z2,@var{addr},@var{kind}
34247 @itemx Z2,@var{addr},@var{kind}
34248 @cindex @samp{z2} packet
34249 @cindex @samp{Z2} packet
34250 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34251 @var{kind} is interpreted as the number of bytes to watch.
34263 @item z3,@var{addr},@var{kind}
34264 @itemx Z3,@var{addr},@var{kind}
34265 @cindex @samp{z3} packet
34266 @cindex @samp{Z3} packet
34267 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34268 @var{kind} is interpreted as the number of bytes to watch.
34280 @item z4,@var{addr},@var{kind}
34281 @itemx Z4,@var{addr},@var{kind}
34282 @cindex @samp{z4} packet
34283 @cindex @samp{Z4} packet
34284 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34285 @var{kind} is interpreted as the number of bytes to watch.
34299 @node Stop Reply Packets
34300 @section Stop Reply Packets
34301 @cindex stop reply packets
34303 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34304 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34305 receive any of the below as a reply. Except for @samp{?}
34306 and @samp{vStopped}, that reply is only returned
34307 when the target halts. In the below the exact meaning of @dfn{signal
34308 number} is defined by the header @file{include/gdb/signals.h} in the
34309 @value{GDBN} source code.
34311 As in the description of request packets, we include spaces in the
34312 reply templates for clarity; these are not part of the reply packet's
34313 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34319 The program received signal number @var{AA} (a two-digit hexadecimal
34320 number). This is equivalent to a @samp{T} response with no
34321 @var{n}:@var{r} pairs.
34323 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34324 @cindex @samp{T} packet reply
34325 The program received signal number @var{AA} (a two-digit hexadecimal
34326 number). This is equivalent to an @samp{S} response, except that the
34327 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34328 and other information directly in the stop reply packet, reducing
34329 round-trip latency. Single-step and breakpoint traps are reported
34330 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34334 If @var{n} is a hexadecimal number, it is a register number, and the
34335 corresponding @var{r} gives that register's value. @var{r} is a
34336 series of bytes in target byte order, with each byte given by a
34337 two-digit hex number.
34340 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34341 the stopped thread, as specified in @ref{thread-id syntax}.
34344 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34345 the core on which the stop event was detected.
34348 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34349 specific event that stopped the target. The currently defined stop
34350 reasons are listed below. @var{aa} should be @samp{05}, the trap
34351 signal. At most one stop reason should be present.
34354 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34355 and go on to the next; this allows us to extend the protocol in the
34359 The currently defined stop reasons are:
34365 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34368 @cindex shared library events, remote reply
34370 The packet indicates that the loaded libraries have changed.
34371 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34372 list of loaded libraries. @var{r} is ignored.
34374 @cindex replay log events, remote reply
34376 The packet indicates that the target cannot continue replaying
34377 logged execution events, because it has reached the end (or the
34378 beginning when executing backward) of the log. The value of @var{r}
34379 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34380 for more information.
34384 @itemx W @var{AA} ; process:@var{pid}
34385 The process exited, and @var{AA} is the exit status. This is only
34386 applicable to certain targets.
34388 The second form of the response, including the process ID of the exited
34389 process, can be used only when @value{GDBN} has reported support for
34390 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34391 The @var{pid} is formatted as a big-endian hex string.
34394 @itemx X @var{AA} ; process:@var{pid}
34395 The process terminated with signal @var{AA}.
34397 The second form of the response, including the process ID of the
34398 terminated process, can be used only when @value{GDBN} has reported
34399 support for multiprocess protocol extensions; see @ref{multiprocess
34400 extensions}. The @var{pid} is formatted as a big-endian hex string.
34402 @item O @var{XX}@dots{}
34403 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34404 written as the program's console output. This can happen at any time
34405 while the program is running and the debugger should continue to wait
34406 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34408 @item F @var{call-id},@var{parameter}@dots{}
34409 @var{call-id} is the identifier which says which host system call should
34410 be called. This is just the name of the function. Translation into the
34411 correct system call is only applicable as it's defined in @value{GDBN}.
34412 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34415 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34416 this very system call.
34418 The target replies with this packet when it expects @value{GDBN} to
34419 call a host system call on behalf of the target. @value{GDBN} replies
34420 with an appropriate @samp{F} packet and keeps up waiting for the next
34421 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34422 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34423 Protocol Extension}, for more details.
34427 @node General Query Packets
34428 @section General Query Packets
34429 @cindex remote query requests
34431 Packets starting with @samp{q} are @dfn{general query packets};
34432 packets starting with @samp{Q} are @dfn{general set packets}. General
34433 query and set packets are a semi-unified form for retrieving and
34434 sending information to and from the stub.
34436 The initial letter of a query or set packet is followed by a name
34437 indicating what sort of thing the packet applies to. For example,
34438 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34439 definitions with the stub. These packet names follow some
34444 The name must not contain commas, colons or semicolons.
34446 Most @value{GDBN} query and set packets have a leading upper case
34449 The names of custom vendor packets should use a company prefix, in
34450 lower case, followed by a period. For example, packets designed at
34451 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34452 foos) or @samp{Qacme.bar} (for setting bars).
34455 The name of a query or set packet should be separated from any
34456 parameters by a @samp{:}; the parameters themselves should be
34457 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34458 full packet name, and check for a separator or the end of the packet,
34459 in case two packet names share a common prefix. New packets should not begin
34460 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34461 packets predate these conventions, and have arguments without any terminator
34462 for the packet name; we suspect they are in widespread use in places that
34463 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34464 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34467 Like the descriptions of the other packets, each description here
34468 has a template showing the packet's overall syntax, followed by an
34469 explanation of the packet's meaning. We include spaces in some of the
34470 templates for clarity; these are not part of the packet's syntax. No
34471 @value{GDBN} packet uses spaces to separate its components.
34473 Here are the currently defined query and set packets:
34477 @item QAllow:@var{op}:@var{val}@dots{}
34478 @cindex @samp{QAllow} packet
34479 Specify which operations @value{GDBN} expects to request of the
34480 target, as a semicolon-separated list of operation name and value
34481 pairs. Possible values for @var{op} include @samp{WriteReg},
34482 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34483 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34484 indicating that @value{GDBN} will not request the operation, or 1,
34485 indicating that it may. (The target can then use this to set up its
34486 own internals optimally, for instance if the debugger never expects to
34487 insert breakpoints, it may not need to install its own trap handler.)
34490 @cindex current thread, remote request
34491 @cindex @samp{qC} packet
34492 Return the current thread ID.
34496 @item QC @var{thread-id}
34497 Where @var{thread-id} is a thread ID as documented in
34498 @ref{thread-id syntax}.
34499 @item @r{(anything else)}
34500 Any other reply implies the old thread ID.
34503 @item qCRC:@var{addr},@var{length}
34504 @cindex CRC of memory block, remote request
34505 @cindex @samp{qCRC} packet
34506 Compute the CRC checksum of a block of memory using CRC-32 defined in
34507 IEEE 802.3. The CRC is computed byte at a time, taking the most
34508 significant bit of each byte first. The initial pattern code
34509 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34511 @emph{Note:} This is the same CRC used in validating separate debug
34512 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34513 Files}). However the algorithm is slightly different. When validating
34514 separate debug files, the CRC is computed taking the @emph{least}
34515 significant bit of each byte first, and the final result is inverted to
34516 detect trailing zeros.
34521 An error (such as memory fault)
34522 @item C @var{crc32}
34523 The specified memory region's checksum is @var{crc32}.
34526 @item QDisableRandomization:@var{value}
34527 @cindex disable address space randomization, remote request
34528 @cindex @samp{QDisableRandomization} packet
34529 Some target operating systems will randomize the virtual address space
34530 of the inferior process as a security feature, but provide a feature
34531 to disable such randomization, e.g.@: to allow for a more deterministic
34532 debugging experience. On such systems, this packet with a @var{value}
34533 of 1 directs the target to disable address space randomization for
34534 processes subsequently started via @samp{vRun} packets, while a packet
34535 with a @var{value} of 0 tells the target to enable address space
34538 This packet is only available in extended mode (@pxref{extended mode}).
34543 The request succeeded.
34546 An error occurred. @var{nn} are hex digits.
34549 An empty reply indicates that @samp{QDisableRandomization} is not supported
34553 This packet is not probed by default; the remote stub must request it,
34554 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34555 This should only be done on targets that actually support disabling
34556 address space randomization.
34559 @itemx qsThreadInfo
34560 @cindex list active threads, remote request
34561 @cindex @samp{qfThreadInfo} packet
34562 @cindex @samp{qsThreadInfo} packet
34563 Obtain a list of all active thread IDs from the target (OS). Since there
34564 may be too many active threads to fit into one reply packet, this query
34565 works iteratively: it may require more than one query/reply sequence to
34566 obtain the entire list of threads. The first query of the sequence will
34567 be the @samp{qfThreadInfo} query; subsequent queries in the
34568 sequence will be the @samp{qsThreadInfo} query.
34570 NOTE: This packet replaces the @samp{qL} query (see below).
34574 @item m @var{thread-id}
34576 @item m @var{thread-id},@var{thread-id}@dots{}
34577 a comma-separated list of thread IDs
34579 (lower case letter @samp{L}) denotes end of list.
34582 In response to each query, the target will reply with a list of one or
34583 more thread IDs, separated by commas.
34584 @value{GDBN} will respond to each reply with a request for more thread
34585 ids (using the @samp{qs} form of the query), until the target responds
34586 with @samp{l} (lower-case ell, for @dfn{last}).
34587 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34590 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34591 @cindex get thread-local storage address, remote request
34592 @cindex @samp{qGetTLSAddr} packet
34593 Fetch the address associated with thread local storage specified
34594 by @var{thread-id}, @var{offset}, and @var{lm}.
34596 @var{thread-id} is the thread ID associated with the
34597 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34599 @var{offset} is the (big endian, hex encoded) offset associated with the
34600 thread local variable. (This offset is obtained from the debug
34601 information associated with the variable.)
34603 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34604 load module associated with the thread local storage. For example,
34605 a @sc{gnu}/Linux system will pass the link map address of the shared
34606 object associated with the thread local storage under consideration.
34607 Other operating environments may choose to represent the load module
34608 differently, so the precise meaning of this parameter will vary.
34612 @item @var{XX}@dots{}
34613 Hex encoded (big endian) bytes representing the address of the thread
34614 local storage requested.
34617 An error occurred. @var{nn} are hex digits.
34620 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34623 @item qGetTIBAddr:@var{thread-id}
34624 @cindex get thread information block address
34625 @cindex @samp{qGetTIBAddr} packet
34626 Fetch address of the Windows OS specific Thread Information Block.
34628 @var{thread-id} is the thread ID associated with the thread.
34632 @item @var{XX}@dots{}
34633 Hex encoded (big endian) bytes representing the linear address of the
34634 thread information block.
34637 An error occured. This means that either the thread was not found, or the
34638 address could not be retrieved.
34641 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34644 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34645 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34646 digit) is one to indicate the first query and zero to indicate a
34647 subsequent query; @var{threadcount} (two hex digits) is the maximum
34648 number of threads the response packet can contain; and @var{nextthread}
34649 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34650 returned in the response as @var{argthread}.
34652 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34656 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34657 Where: @var{count} (two hex digits) is the number of threads being
34658 returned; @var{done} (one hex digit) is zero to indicate more threads
34659 and one indicates no further threads; @var{argthreadid} (eight hex
34660 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34661 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34662 digits). See @code{remote.c:parse_threadlist_response()}.
34666 @cindex section offsets, remote request
34667 @cindex @samp{qOffsets} packet
34668 Get section offsets that the target used when relocating the downloaded
34673 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34674 Relocate the @code{Text} section by @var{xxx} from its original address.
34675 Relocate the @code{Data} section by @var{yyy} from its original address.
34676 If the object file format provides segment information (e.g.@: @sc{elf}
34677 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34678 segments by the supplied offsets.
34680 @emph{Note: while a @code{Bss} offset may be included in the response,
34681 @value{GDBN} ignores this and instead applies the @code{Data} offset
34682 to the @code{Bss} section.}
34684 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34685 Relocate the first segment of the object file, which conventionally
34686 contains program code, to a starting address of @var{xxx}. If
34687 @samp{DataSeg} is specified, relocate the second segment, which
34688 conventionally contains modifiable data, to a starting address of
34689 @var{yyy}. @value{GDBN} will report an error if the object file
34690 does not contain segment information, or does not contain at least
34691 as many segments as mentioned in the reply. Extra segments are
34692 kept at fixed offsets relative to the last relocated segment.
34695 @item qP @var{mode} @var{thread-id}
34696 @cindex thread information, remote request
34697 @cindex @samp{qP} packet
34698 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34699 encoded 32 bit mode; @var{thread-id} is a thread ID
34700 (@pxref{thread-id syntax}).
34702 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34705 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34709 @cindex non-stop mode, remote request
34710 @cindex @samp{QNonStop} packet
34712 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34713 @xref{Remote Non-Stop}, for more information.
34718 The request succeeded.
34721 An error occurred. @var{nn} are hex digits.
34724 An empty reply indicates that @samp{QNonStop} is not supported by
34728 This packet is not probed by default; the remote stub must request it,
34729 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34730 Use of this packet is controlled by the @code{set non-stop} command;
34731 @pxref{Non-Stop Mode}.
34733 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34734 @cindex pass signals to inferior, remote request
34735 @cindex @samp{QPassSignals} packet
34736 @anchor{QPassSignals}
34737 Each listed @var{signal} should be passed directly to the inferior process.
34738 Signals are numbered identically to continue packets and stop replies
34739 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34740 strictly greater than the previous item. These signals do not need to stop
34741 the inferior, or be reported to @value{GDBN}. All other signals should be
34742 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34743 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34744 new list. This packet improves performance when using @samp{handle
34745 @var{signal} nostop noprint pass}.
34750 The request succeeded.
34753 An error occurred. @var{nn} are hex digits.
34756 An empty reply indicates that @samp{QPassSignals} is not supported by
34760 Use of this packet is controlled by the @code{set remote pass-signals}
34761 command (@pxref{Remote Configuration, set remote pass-signals}).
34762 This packet is not probed by default; the remote stub must request it,
34763 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34765 @item qRcmd,@var{command}
34766 @cindex execute remote command, remote request
34767 @cindex @samp{qRcmd} packet
34768 @var{command} (hex encoded) is passed to the local interpreter for
34769 execution. Invalid commands should be reported using the output
34770 string. Before the final result packet, the target may also respond
34771 with a number of intermediate @samp{O@var{output}} console output
34772 packets. @emph{Implementors should note that providing access to a
34773 stubs's interpreter may have security implications}.
34778 A command response with no output.
34780 A command response with the hex encoded output string @var{OUTPUT}.
34782 Indicate a badly formed request.
34784 An empty reply indicates that @samp{qRcmd} is not recognized.
34787 (Note that the @code{qRcmd} packet's name is separated from the
34788 command by a @samp{,}, not a @samp{:}, contrary to the naming
34789 conventions above. Please don't use this packet as a model for new
34792 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34793 @cindex searching memory, in remote debugging
34794 @cindex @samp{qSearch:memory} packet
34795 @anchor{qSearch memory}
34796 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34797 @var{address} and @var{length} are encoded in hex.
34798 @var{search-pattern} is a sequence of bytes, hex encoded.
34803 The pattern was not found.
34805 The pattern was found at @var{address}.
34807 A badly formed request or an error was encountered while searching memory.
34809 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34812 @item QStartNoAckMode
34813 @cindex @samp{QStartNoAckMode} packet
34814 @anchor{QStartNoAckMode}
34815 Request that the remote stub disable the normal @samp{+}/@samp{-}
34816 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34821 The stub has switched to no-acknowledgment mode.
34822 @value{GDBN} acknowledges this reponse,
34823 but neither the stub nor @value{GDBN} shall send or expect further
34824 @samp{+}/@samp{-} acknowledgments in the current connection.
34826 An empty reply indicates that the stub does not support no-acknowledgment mode.
34829 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34830 @cindex supported packets, remote query
34831 @cindex features of the remote protocol
34832 @cindex @samp{qSupported} packet
34833 @anchor{qSupported}
34834 Tell the remote stub about features supported by @value{GDBN}, and
34835 query the stub for features it supports. This packet allows
34836 @value{GDBN} and the remote stub to take advantage of each others'
34837 features. @samp{qSupported} also consolidates multiple feature probes
34838 at startup, to improve @value{GDBN} performance---a single larger
34839 packet performs better than multiple smaller probe packets on
34840 high-latency links. Some features may enable behavior which must not
34841 be on by default, e.g.@: because it would confuse older clients or
34842 stubs. Other features may describe packets which could be
34843 automatically probed for, but are not. These features must be
34844 reported before @value{GDBN} will use them. This ``default
34845 unsupported'' behavior is not appropriate for all packets, but it
34846 helps to keep the initial connection time under control with new
34847 versions of @value{GDBN} which support increasing numbers of packets.
34851 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34852 The stub supports or does not support each returned @var{stubfeature},
34853 depending on the form of each @var{stubfeature} (see below for the
34856 An empty reply indicates that @samp{qSupported} is not recognized,
34857 or that no features needed to be reported to @value{GDBN}.
34860 The allowed forms for each feature (either a @var{gdbfeature} in the
34861 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34865 @item @var{name}=@var{value}
34866 The remote protocol feature @var{name} is supported, and associated
34867 with the specified @var{value}. The format of @var{value} depends
34868 on the feature, but it must not include a semicolon.
34870 The remote protocol feature @var{name} is supported, and does not
34871 need an associated value.
34873 The remote protocol feature @var{name} is not supported.
34875 The remote protocol feature @var{name} may be supported, and
34876 @value{GDBN} should auto-detect support in some other way when it is
34877 needed. This form will not be used for @var{gdbfeature} notifications,
34878 but may be used for @var{stubfeature} responses.
34881 Whenever the stub receives a @samp{qSupported} request, the
34882 supplied set of @value{GDBN} features should override any previous
34883 request. This allows @value{GDBN} to put the stub in a known
34884 state, even if the stub had previously been communicating with
34885 a different version of @value{GDBN}.
34887 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34892 This feature indicates whether @value{GDBN} supports multiprocess
34893 extensions to the remote protocol. @value{GDBN} does not use such
34894 extensions unless the stub also reports that it supports them by
34895 including @samp{multiprocess+} in its @samp{qSupported} reply.
34896 @xref{multiprocess extensions}, for details.
34899 This feature indicates that @value{GDBN} supports the XML target
34900 description. If the stub sees @samp{xmlRegisters=} with target
34901 specific strings separated by a comma, it will report register
34905 This feature indicates whether @value{GDBN} supports the
34906 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34907 instruction reply packet}).
34910 Stubs should ignore any unknown values for
34911 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34912 packet supports receiving packets of unlimited length (earlier
34913 versions of @value{GDBN} may reject overly long responses). Additional values
34914 for @var{gdbfeature} may be defined in the future to let the stub take
34915 advantage of new features in @value{GDBN}, e.g.@: incompatible
34916 improvements in the remote protocol---the @samp{multiprocess} feature is
34917 an example of such a feature. The stub's reply should be independent
34918 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34919 describes all the features it supports, and then the stub replies with
34920 all the features it supports.
34922 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34923 responses, as long as each response uses one of the standard forms.
34925 Some features are flags. A stub which supports a flag feature
34926 should respond with a @samp{+} form response. Other features
34927 require values, and the stub should respond with an @samp{=}
34930 Each feature has a default value, which @value{GDBN} will use if
34931 @samp{qSupported} is not available or if the feature is not mentioned
34932 in the @samp{qSupported} response. The default values are fixed; a
34933 stub is free to omit any feature responses that match the defaults.
34935 Not all features can be probed, but for those which can, the probing
34936 mechanism is useful: in some cases, a stub's internal
34937 architecture may not allow the protocol layer to know some information
34938 about the underlying target in advance. This is especially common in
34939 stubs which may be configured for multiple targets.
34941 These are the currently defined stub features and their properties:
34943 @multitable @columnfractions 0.35 0.2 0.12 0.2
34944 @c NOTE: The first row should be @headitem, but we do not yet require
34945 @c a new enough version of Texinfo (4.7) to use @headitem.
34947 @tab Value Required
34951 @item @samp{PacketSize}
34956 @item @samp{qXfer:auxv:read}
34961 @item @samp{qXfer:features:read}
34966 @item @samp{qXfer:libraries:read}
34971 @item @samp{qXfer:memory-map:read}
34976 @item @samp{qXfer:sdata:read}
34981 @item @samp{qXfer:spu:read}
34986 @item @samp{qXfer:spu:write}
34991 @item @samp{qXfer:siginfo:read}
34996 @item @samp{qXfer:siginfo:write}
35001 @item @samp{qXfer:threads:read}
35006 @item @samp{qXfer:traceframe-info:read}
35011 @item @samp{qXfer:fdpic:read}
35016 @item @samp{QNonStop}
35021 @item @samp{QPassSignals}
35026 @item @samp{QStartNoAckMode}
35031 @item @samp{multiprocess}
35036 @item @samp{ConditionalTracepoints}
35041 @item @samp{ReverseContinue}
35046 @item @samp{ReverseStep}
35051 @item @samp{TracepointSource}
35056 @item @samp{QAllow}
35061 @item @samp{QDisableRandomization}
35066 @item @samp{EnableDisableTracepoints}
35071 @item @samp{tracenz}
35078 These are the currently defined stub features, in more detail:
35081 @cindex packet size, remote protocol
35082 @item PacketSize=@var{bytes}
35083 The remote stub can accept packets up to at least @var{bytes} in
35084 length. @value{GDBN} will send packets up to this size for bulk
35085 transfers, and will never send larger packets. This is a limit on the
35086 data characters in the packet, including the frame and checksum.
35087 There is no trailing NUL byte in a remote protocol packet; if the stub
35088 stores packets in a NUL-terminated format, it should allow an extra
35089 byte in its buffer for the NUL. If this stub feature is not supported,
35090 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35092 @item qXfer:auxv:read
35093 The remote stub understands the @samp{qXfer:auxv:read} packet
35094 (@pxref{qXfer auxiliary vector read}).
35096 @item qXfer:features:read
35097 The remote stub understands the @samp{qXfer:features:read} packet
35098 (@pxref{qXfer target description read}).
35100 @item qXfer:libraries:read
35101 The remote stub understands the @samp{qXfer:libraries:read} packet
35102 (@pxref{qXfer library list read}).
35104 @item qXfer:libraries-svr4:read
35105 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35106 (@pxref{qXfer svr4 library list read}).
35108 @item qXfer:memory-map:read
35109 The remote stub understands the @samp{qXfer:memory-map:read} packet
35110 (@pxref{qXfer memory map read}).
35112 @item qXfer:sdata:read
35113 The remote stub understands the @samp{qXfer:sdata:read} packet
35114 (@pxref{qXfer sdata read}).
35116 @item qXfer:spu:read
35117 The remote stub understands the @samp{qXfer:spu:read} packet
35118 (@pxref{qXfer spu read}).
35120 @item qXfer:spu:write
35121 The remote stub understands the @samp{qXfer:spu:write} packet
35122 (@pxref{qXfer spu write}).
35124 @item qXfer:siginfo:read
35125 The remote stub understands the @samp{qXfer:siginfo:read} packet
35126 (@pxref{qXfer siginfo read}).
35128 @item qXfer:siginfo:write
35129 The remote stub understands the @samp{qXfer:siginfo:write} packet
35130 (@pxref{qXfer siginfo write}).
35132 @item qXfer:threads:read
35133 The remote stub understands the @samp{qXfer:threads:read} packet
35134 (@pxref{qXfer threads read}).
35136 @item qXfer:traceframe-info:read
35137 The remote stub understands the @samp{qXfer:traceframe-info:read}
35138 packet (@pxref{qXfer traceframe info read}).
35140 @item qXfer:fdpic:read
35141 The remote stub understands the @samp{qXfer:fdpic:read}
35142 packet (@pxref{qXfer fdpic loadmap read}).
35145 The remote stub understands the @samp{QNonStop} packet
35146 (@pxref{QNonStop}).
35149 The remote stub understands the @samp{QPassSignals} packet
35150 (@pxref{QPassSignals}).
35152 @item QStartNoAckMode
35153 The remote stub understands the @samp{QStartNoAckMode} packet and
35154 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35157 @anchor{multiprocess extensions}
35158 @cindex multiprocess extensions, in remote protocol
35159 The remote stub understands the multiprocess extensions to the remote
35160 protocol syntax. The multiprocess extensions affect the syntax of
35161 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35162 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35163 replies. Note that reporting this feature indicates support for the
35164 syntactic extensions only, not that the stub necessarily supports
35165 debugging of more than one process at a time. The stub must not use
35166 multiprocess extensions in packet replies unless @value{GDBN} has also
35167 indicated it supports them in its @samp{qSupported} request.
35169 @item qXfer:osdata:read
35170 The remote stub understands the @samp{qXfer:osdata:read} packet
35171 ((@pxref{qXfer osdata read}).
35173 @item ConditionalTracepoints
35174 The remote stub accepts and implements conditional expressions defined
35175 for tracepoints (@pxref{Tracepoint Conditions}).
35177 @item ReverseContinue
35178 The remote stub accepts and implements the reverse continue packet
35182 The remote stub accepts and implements the reverse step packet
35185 @item TracepointSource
35186 The remote stub understands the @samp{QTDPsrc} packet that supplies
35187 the source form of tracepoint definitions.
35190 The remote stub understands the @samp{QAllow} packet.
35192 @item QDisableRandomization
35193 The remote stub understands the @samp{QDisableRandomization} packet.
35195 @item StaticTracepoint
35196 @cindex static tracepoints, in remote protocol
35197 The remote stub supports static tracepoints.
35199 @item InstallInTrace
35200 @anchor{install tracepoint in tracing}
35201 The remote stub supports installing tracepoint in tracing.
35203 @item EnableDisableTracepoints
35204 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35205 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35206 to be enabled and disabled while a trace experiment is running.
35209 @cindex string tracing, in remote protocol
35210 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35211 See @ref{Bytecode Descriptions} for details about the bytecode.
35216 @cindex symbol lookup, remote request
35217 @cindex @samp{qSymbol} packet
35218 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35219 requests. Accept requests from the target for the values of symbols.
35224 The target does not need to look up any (more) symbols.
35225 @item qSymbol:@var{sym_name}
35226 The target requests the value of symbol @var{sym_name} (hex encoded).
35227 @value{GDBN} may provide the value by using the
35228 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35232 @item qSymbol:@var{sym_value}:@var{sym_name}
35233 Set the value of @var{sym_name} to @var{sym_value}.
35235 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35236 target has previously requested.
35238 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35239 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35245 The target does not need to look up any (more) symbols.
35246 @item qSymbol:@var{sym_name}
35247 The target requests the value of a new symbol @var{sym_name} (hex
35248 encoded). @value{GDBN} will continue to supply the values of symbols
35249 (if available), until the target ceases to request them.
35254 @item QTDisconnected
35261 @itemx qTMinFTPILen
35263 @xref{Tracepoint Packets}.
35265 @item qThreadExtraInfo,@var{thread-id}
35266 @cindex thread attributes info, remote request
35267 @cindex @samp{qThreadExtraInfo} packet
35268 Obtain a printable string description of a thread's attributes from
35269 the target OS. @var{thread-id} is a thread ID;
35270 see @ref{thread-id syntax}. This
35271 string may contain anything that the target OS thinks is interesting
35272 for @value{GDBN} to tell the user about the thread. The string is
35273 displayed in @value{GDBN}'s @code{info threads} display. Some
35274 examples of possible thread extra info strings are @samp{Runnable}, or
35275 @samp{Blocked on Mutex}.
35279 @item @var{XX}@dots{}
35280 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35281 comprising the printable string containing the extra information about
35282 the thread's attributes.
35285 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35286 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35287 conventions above. Please don't use this packet as a model for new
35306 @xref{Tracepoint Packets}.
35308 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35309 @cindex read special object, remote request
35310 @cindex @samp{qXfer} packet
35311 @anchor{qXfer read}
35312 Read uninterpreted bytes from the target's special data area
35313 identified by the keyword @var{object}. Request @var{length} bytes
35314 starting at @var{offset} bytes into the data. The content and
35315 encoding of @var{annex} is specific to @var{object}; it can supply
35316 additional details about what data to access.
35318 Here are the specific requests of this form defined so far. All
35319 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35320 formats, listed below.
35323 @item qXfer:auxv:read::@var{offset},@var{length}
35324 @anchor{qXfer auxiliary vector read}
35325 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35326 auxiliary vector}. Note @var{annex} must be empty.
35328 This packet is not probed by default; the remote stub must request it,
35329 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35331 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35332 @anchor{qXfer target description read}
35333 Access the @dfn{target description}. @xref{Target Descriptions}. The
35334 annex specifies which XML document to access. The main description is
35335 always loaded from the @samp{target.xml} annex.
35337 This packet is not probed by default; the remote stub must request it,
35338 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35340 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35341 @anchor{qXfer library list read}
35342 Access the target's list of loaded libraries. @xref{Library List Format}.
35343 The annex part of the generic @samp{qXfer} packet must be empty
35344 (@pxref{qXfer read}).
35346 Targets which maintain a list of libraries in the program's memory do
35347 not need to implement this packet; it is designed for platforms where
35348 the operating system manages the list of loaded libraries.
35350 This packet is not probed by default; the remote stub must request it,
35351 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35353 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35354 @anchor{qXfer svr4 library list read}
35355 Access the target's list of loaded libraries when the target is an SVR4
35356 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35357 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35359 This packet is optional for better performance on SVR4 targets.
35360 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35362 This packet is not probed by default; the remote stub must request it,
35363 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35365 @item qXfer:memory-map:read::@var{offset},@var{length}
35366 @anchor{qXfer memory map read}
35367 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35368 annex part of the generic @samp{qXfer} packet must be empty
35369 (@pxref{qXfer read}).
35371 This packet is not probed by default; the remote stub must request it,
35372 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35374 @item qXfer:sdata:read::@var{offset},@var{length}
35375 @anchor{qXfer sdata read}
35377 Read contents of the extra collected static tracepoint marker
35378 information. The annex part of the generic @samp{qXfer} packet must
35379 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35382 This packet is not probed by default; the remote stub must request it,
35383 by supplying an appropriate @samp{qSupported} response
35384 (@pxref{qSupported}).
35386 @item qXfer:siginfo:read::@var{offset},@var{length}
35387 @anchor{qXfer siginfo read}
35388 Read contents of the extra signal information on the target
35389 system. The annex part of the generic @samp{qXfer} packet must be
35390 empty (@pxref{qXfer read}).
35392 This packet is not probed by default; the remote stub must request it,
35393 by supplying an appropriate @samp{qSupported} response
35394 (@pxref{qSupported}).
35396 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35397 @anchor{qXfer spu read}
35398 Read contents of an @code{spufs} file on the target system. The
35399 annex specifies which file to read; it must be of the form
35400 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35401 in the target process, and @var{name} identifes the @code{spufs} file
35402 in that context to be accessed.
35404 This packet is not probed by default; the remote stub must request it,
35405 by supplying an appropriate @samp{qSupported} response
35406 (@pxref{qSupported}).
35408 @item qXfer:threads:read::@var{offset},@var{length}
35409 @anchor{qXfer threads read}
35410 Access the list of threads on target. @xref{Thread List Format}. The
35411 annex part of the generic @samp{qXfer} packet must be empty
35412 (@pxref{qXfer read}).
35414 This packet is not probed by default; the remote stub must request it,
35415 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35417 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35418 @anchor{qXfer traceframe info read}
35420 Return a description of the current traceframe's contents.
35421 @xref{Traceframe Info Format}. The annex part of the generic
35422 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35424 This packet is not probed by default; the remote stub must request it,
35425 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35427 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35428 @anchor{qXfer fdpic loadmap read}
35429 Read contents of @code{loadmap}s on the target system. The
35430 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35431 executable @code{loadmap} or interpreter @code{loadmap} to read.
35433 This packet is not probed by default; the remote stub must request it,
35434 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35436 @item qXfer:osdata:read::@var{offset},@var{length}
35437 @anchor{qXfer osdata read}
35438 Access the target's @dfn{operating system information}.
35439 @xref{Operating System Information}.
35446 Data @var{data} (@pxref{Binary Data}) has been read from the
35447 target. There may be more data at a higher address (although
35448 it is permitted to return @samp{m} even for the last valid
35449 block of data, as long as at least one byte of data was read).
35450 @var{data} may have fewer bytes than the @var{length} in the
35454 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35455 There is no more data to be read. @var{data} may have fewer bytes
35456 than the @var{length} in the request.
35459 The @var{offset} in the request is at the end of the data.
35460 There is no more data to be read.
35463 The request was malformed, or @var{annex} was invalid.
35466 The offset was invalid, or there was an error encountered reading the data.
35467 @var{nn} is a hex-encoded @code{errno} value.
35470 An empty reply indicates the @var{object} string was not recognized by
35471 the stub, or that the object does not support reading.
35474 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35475 @cindex write data into object, remote request
35476 @anchor{qXfer write}
35477 Write uninterpreted bytes into the target's special data area
35478 identified by the keyword @var{object}, starting at @var{offset} bytes
35479 into the data. @var{data}@dots{} is the binary-encoded data
35480 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35481 is specific to @var{object}; it can supply additional details about what data
35484 Here are the specific requests of this form defined so far. All
35485 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35486 formats, listed below.
35489 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35490 @anchor{qXfer siginfo write}
35491 Write @var{data} to the extra signal information on the target system.
35492 The annex part of the generic @samp{qXfer} packet must be
35493 empty (@pxref{qXfer write}).
35495 This packet is not probed by default; the remote stub must request it,
35496 by supplying an appropriate @samp{qSupported} response
35497 (@pxref{qSupported}).
35499 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35500 @anchor{qXfer spu write}
35501 Write @var{data} to an @code{spufs} file on the target system. The
35502 annex specifies which file to write; it must be of the form
35503 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35504 in the target process, and @var{name} identifes the @code{spufs} file
35505 in that context to be accessed.
35507 This packet is not probed by default; the remote stub must request it,
35508 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35514 @var{nn} (hex encoded) is the number of bytes written.
35515 This may be fewer bytes than supplied in the request.
35518 The request was malformed, or @var{annex} was invalid.
35521 The offset was invalid, or there was an error encountered writing the data.
35522 @var{nn} is a hex-encoded @code{errno} value.
35525 An empty reply indicates the @var{object} string was not
35526 recognized by the stub, or that the object does not support writing.
35529 @item qXfer:@var{object}:@var{operation}:@dots{}
35530 Requests of this form may be added in the future. When a stub does
35531 not recognize the @var{object} keyword, or its support for
35532 @var{object} does not recognize the @var{operation} keyword, the stub
35533 must respond with an empty packet.
35535 @item qAttached:@var{pid}
35536 @cindex query attached, remote request
35537 @cindex @samp{qAttached} packet
35538 Return an indication of whether the remote server attached to an
35539 existing process or created a new process. When the multiprocess
35540 protocol extensions are supported (@pxref{multiprocess extensions}),
35541 @var{pid} is an integer in hexadecimal format identifying the target
35542 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35543 the query packet will be simplified as @samp{qAttached}.
35545 This query is used, for example, to know whether the remote process
35546 should be detached or killed when a @value{GDBN} session is ended with
35547 the @code{quit} command.
35552 The remote server attached to an existing process.
35554 The remote server created a new process.
35556 A badly formed request or an error was encountered.
35561 @node Architecture-Specific Protocol Details
35562 @section Architecture-Specific Protocol Details
35564 This section describes how the remote protocol is applied to specific
35565 target architectures. Also see @ref{Standard Target Features}, for
35566 details of XML target descriptions for each architecture.
35570 @subsubsection Breakpoint Kinds
35572 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35577 16-bit Thumb mode breakpoint.
35580 32-bit Thumb mode (Thumb-2) breakpoint.
35583 32-bit ARM mode breakpoint.
35589 @subsubsection Register Packet Format
35591 The following @code{g}/@code{G} packets have previously been defined.
35592 In the below, some thirty-two bit registers are transferred as
35593 sixty-four bits. Those registers should be zero/sign extended (which?)
35594 to fill the space allocated. Register bytes are transferred in target
35595 byte order. The two nibbles within a register byte are transferred
35596 most-significant - least-significant.
35602 All registers are transferred as thirty-two bit quantities in the order:
35603 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35604 registers; fsr; fir; fp.
35608 All registers are transferred as sixty-four bit quantities (including
35609 thirty-two bit registers such as @code{sr}). The ordering is the same
35614 @node Tracepoint Packets
35615 @section Tracepoint Packets
35616 @cindex tracepoint packets
35617 @cindex packets, tracepoint
35619 Here we describe the packets @value{GDBN} uses to implement
35620 tracepoints (@pxref{Tracepoints}).
35624 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35625 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35626 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35627 the tracepoint is disabled. @var{step} is the tracepoint's step
35628 count, and @var{pass} is its pass count. If an @samp{F} is present,
35629 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35630 the number of bytes that the target should copy elsewhere to make room
35631 for the tracepoint. If an @samp{X} is present, it introduces a
35632 tracepoint condition, which consists of a hexadecimal length, followed
35633 by a comma and hex-encoded bytes, in a manner similar to action
35634 encodings as described below. If the trailing @samp{-} is present,
35635 further @samp{QTDP} packets will follow to specify this tracepoint's
35641 The packet was understood and carried out.
35643 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35645 The packet was not recognized.
35648 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35649 Define actions to be taken when a tracepoint is hit. @var{n} and
35650 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35651 this tracepoint. This packet may only be sent immediately after
35652 another @samp{QTDP} packet that ended with a @samp{-}. If the
35653 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35654 specifying more actions for this tracepoint.
35656 In the series of action packets for a given tracepoint, at most one
35657 can have an @samp{S} before its first @var{action}. If such a packet
35658 is sent, it and the following packets define ``while-stepping''
35659 actions. Any prior packets define ordinary actions --- that is, those
35660 taken when the tracepoint is first hit. If no action packet has an
35661 @samp{S}, then all the packets in the series specify ordinary
35662 tracepoint actions.
35664 The @samp{@var{action}@dots{}} portion of the packet is a series of
35665 actions, concatenated without separators. Each action has one of the
35671 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35672 a hexadecimal number whose @var{i}'th bit is set if register number
35673 @var{i} should be collected. (The least significant bit is numbered
35674 zero.) Note that @var{mask} may be any number of digits long; it may
35675 not fit in a 32-bit word.
35677 @item M @var{basereg},@var{offset},@var{len}
35678 Collect @var{len} bytes of memory starting at the address in register
35679 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35680 @samp{-1}, then the range has a fixed address: @var{offset} is the
35681 address of the lowest byte to collect. The @var{basereg},
35682 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35683 values (the @samp{-1} value for @var{basereg} is a special case).
35685 @item X @var{len},@var{expr}
35686 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35687 it directs. @var{expr} is an agent expression, as described in
35688 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35689 two-digit hex number in the packet; @var{len} is the number of bytes
35690 in the expression (and thus one-half the number of hex digits in the
35695 Any number of actions may be packed together in a single @samp{QTDP}
35696 packet, as long as the packet does not exceed the maximum packet
35697 length (400 bytes, for many stubs). There may be only one @samp{R}
35698 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35699 actions. Any registers referred to by @samp{M} and @samp{X} actions
35700 must be collected by a preceding @samp{R} action. (The
35701 ``while-stepping'' actions are treated as if they were attached to a
35702 separate tracepoint, as far as these restrictions are concerned.)
35707 The packet was understood and carried out.
35709 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35711 The packet was not recognized.
35714 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35715 @cindex @samp{QTDPsrc} packet
35716 Specify a source string of tracepoint @var{n} at address @var{addr}.
35717 This is useful to get accurate reproduction of the tracepoints
35718 originally downloaded at the beginning of the trace run. @var{type}
35719 is the name of the tracepoint part, such as @samp{cond} for the
35720 tracepoint's conditional expression (see below for a list of types), while
35721 @var{bytes} is the string, encoded in hexadecimal.
35723 @var{start} is the offset of the @var{bytes} within the overall source
35724 string, while @var{slen} is the total length of the source string.
35725 This is intended for handling source strings that are longer than will
35726 fit in a single packet.
35727 @c Add detailed example when this info is moved into a dedicated
35728 @c tracepoint descriptions section.
35730 The available string types are @samp{at} for the location,
35731 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35732 @value{GDBN} sends a separate packet for each command in the action
35733 list, in the same order in which the commands are stored in the list.
35735 The target does not need to do anything with source strings except
35736 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35739 Although this packet is optional, and @value{GDBN} will only send it
35740 if the target replies with @samp{TracepointSource} @xref{General
35741 Query Packets}, it makes both disconnected tracing and trace files
35742 much easier to use. Otherwise the user must be careful that the
35743 tracepoints in effect while looking at trace frames are identical to
35744 the ones in effect during the trace run; even a small discrepancy
35745 could cause @samp{tdump} not to work, or a particular trace frame not
35748 @item QTDV:@var{n}:@var{value}
35749 @cindex define trace state variable, remote request
35750 @cindex @samp{QTDV} packet
35751 Create a new trace state variable, number @var{n}, with an initial
35752 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35753 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35754 the option of not using this packet for initial values of zero; the
35755 target should simply create the trace state variables as they are
35756 mentioned in expressions.
35758 @item QTFrame:@var{n}
35759 Select the @var{n}'th tracepoint frame from the buffer, and use the
35760 register and memory contents recorded there to answer subsequent
35761 request packets from @value{GDBN}.
35763 A successful reply from the stub indicates that the stub has found the
35764 requested frame. The response is a series of parts, concatenated
35765 without separators, describing the frame we selected. Each part has
35766 one of the following forms:
35770 The selected frame is number @var{n} in the trace frame buffer;
35771 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35772 was no frame matching the criteria in the request packet.
35775 The selected trace frame records a hit of tracepoint number @var{t};
35776 @var{t} is a hexadecimal number.
35780 @item QTFrame:pc:@var{addr}
35781 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35782 currently selected frame whose PC is @var{addr};
35783 @var{addr} is a hexadecimal number.
35785 @item QTFrame:tdp:@var{t}
35786 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35787 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35788 is a hexadecimal number.
35790 @item QTFrame:range:@var{start}:@var{end}
35791 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35792 currently selected frame whose PC is between @var{start} (inclusive)
35793 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35796 @item QTFrame:outside:@var{start}:@var{end}
35797 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35798 frame @emph{outside} the given range of addresses (exclusive).
35801 This packet requests the minimum length of instruction at which a fast
35802 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35803 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35804 it depends on the target system being able to create trampolines in
35805 the first 64K of memory, which might or might not be possible for that
35806 system. So the reply to this packet will be 4 if it is able to
35813 The minimum instruction length is currently unknown.
35815 The minimum instruction length is @var{length}, where @var{length} is greater
35816 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35817 that a fast tracepoint may be placed on any instruction regardless of size.
35819 An error has occurred.
35821 An empty reply indicates that the request is not supported by the stub.
35825 Begin the tracepoint experiment. Begin collecting data from
35826 tracepoint hits in the trace frame buffer. This packet supports the
35827 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35828 instruction reply packet}).
35831 End the tracepoint experiment. Stop collecting trace frames.
35833 @item QTEnable:@var{n}:@var{addr}
35835 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35836 experiment. If the tracepoint was previously disabled, then collection
35837 of data from it will resume.
35839 @item QTDisable:@var{n}:@var{addr}
35841 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35842 experiment. No more data will be collected from the tracepoint unless
35843 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35846 Clear the table of tracepoints, and empty the trace frame buffer.
35848 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35849 Establish the given ranges of memory as ``transparent''. The stub
35850 will answer requests for these ranges from memory's current contents,
35851 if they were not collected as part of the tracepoint hit.
35853 @value{GDBN} uses this to mark read-only regions of memory, like those
35854 containing program code. Since these areas never change, they should
35855 still have the same contents they did when the tracepoint was hit, so
35856 there's no reason for the stub to refuse to provide their contents.
35858 @item QTDisconnected:@var{value}
35859 Set the choice to what to do with the tracing run when @value{GDBN}
35860 disconnects from the target. A @var{value} of 1 directs the target to
35861 continue the tracing run, while 0 tells the target to stop tracing if
35862 @value{GDBN} is no longer in the picture.
35865 Ask the stub if there is a trace experiment running right now.
35867 The reply has the form:
35871 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35872 @var{running} is a single digit @code{1} if the trace is presently
35873 running, or @code{0} if not. It is followed by semicolon-separated
35874 optional fields that an agent may use to report additional status.
35878 If the trace is not running, the agent may report any of several
35879 explanations as one of the optional fields:
35884 No trace has been run yet.
35886 @item tstop[:@var{text}]:0
35887 The trace was stopped by a user-originated stop command. The optional
35888 @var{text} field is a user-supplied string supplied as part of the
35889 stop command (for instance, an explanation of why the trace was
35890 stopped manually). It is hex-encoded.
35893 The trace stopped because the trace buffer filled up.
35895 @item tdisconnected:0
35896 The trace stopped because @value{GDBN} disconnected from the target.
35898 @item tpasscount:@var{tpnum}
35899 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35901 @item terror:@var{text}:@var{tpnum}
35902 The trace stopped because tracepoint @var{tpnum} had an error. The
35903 string @var{text} is available to describe the nature of the error
35904 (for instance, a divide by zero in the condition expression).
35905 @var{text} is hex encoded.
35908 The trace stopped for some other reason.
35912 Additional optional fields supply statistical and other information.
35913 Although not required, they are extremely useful for users monitoring
35914 the progress of a trace run. If a trace has stopped, and these
35915 numbers are reported, they must reflect the state of the just-stopped
35920 @item tframes:@var{n}
35921 The number of trace frames in the buffer.
35923 @item tcreated:@var{n}
35924 The total number of trace frames created during the run. This may
35925 be larger than the trace frame count, if the buffer is circular.
35927 @item tsize:@var{n}
35928 The total size of the trace buffer, in bytes.
35930 @item tfree:@var{n}
35931 The number of bytes still unused in the buffer.
35933 @item circular:@var{n}
35934 The value of the circular trace buffer flag. @code{1} means that the
35935 trace buffer is circular and old trace frames will be discarded if
35936 necessary to make room, @code{0} means that the trace buffer is linear
35939 @item disconn:@var{n}
35940 The value of the disconnected tracing flag. @code{1} means that
35941 tracing will continue after @value{GDBN} disconnects, @code{0} means
35942 that the trace run will stop.
35946 @item qTP:@var{tp}:@var{addr}
35947 @cindex tracepoint status, remote request
35948 @cindex @samp{qTP} packet
35949 Ask the stub for the current state of tracepoint number @var{tp} at
35950 address @var{addr}.
35954 @item V@var{hits}:@var{usage}
35955 The tracepoint has been hit @var{hits} times so far during the trace
35956 run, and accounts for @var{usage} in the trace buffer. Note that
35957 @code{while-stepping} steps are not counted as separate hits, but the
35958 steps' space consumption is added into the usage number.
35962 @item qTV:@var{var}
35963 @cindex trace state variable value, remote request
35964 @cindex @samp{qTV} packet
35965 Ask the stub for the value of the trace state variable number @var{var}.
35970 The value of the variable is @var{value}. This will be the current
35971 value of the variable if the user is examining a running target, or a
35972 saved value if the variable was collected in the trace frame that the
35973 user is looking at. Note that multiple requests may result in
35974 different reply values, such as when requesting values while the
35975 program is running.
35978 The value of the variable is unknown. This would occur, for example,
35979 if the user is examining a trace frame in which the requested variable
35985 These packets request data about tracepoints that are being used by
35986 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35987 of data, and multiple @code{qTsP} to get additional pieces. Replies
35988 to these packets generally take the form of the @code{QTDP} packets
35989 that define tracepoints. (FIXME add detailed syntax)
35993 These packets request data about trace state variables that are on the
35994 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35995 and multiple @code{qTsV} to get additional variables. Replies to
35996 these packets follow the syntax of the @code{QTDV} packets that define
35997 trace state variables.
36001 These packets request data about static tracepoint markers that exist
36002 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36003 first piece of data, and multiple @code{qTsSTM} to get additional
36004 pieces. Replies to these packets take the following form:
36008 @item m @var{address}:@var{id}:@var{extra}
36010 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36011 a comma-separated list of markers
36013 (lower case letter @samp{L}) denotes end of list.
36015 An error occurred. @var{nn} are hex digits.
36017 An empty reply indicates that the request is not supported by the
36021 @var{address} is encoded in hex.
36022 @var{id} and @var{extra} are strings encoded in hex.
36024 In response to each query, the target will reply with a list of one or
36025 more markers, separated by commas. @value{GDBN} will respond to each
36026 reply with a request for more markers (using the @samp{qs} form of the
36027 query), until the target responds with @samp{l} (lower-case ell, for
36030 @item qTSTMat:@var{address}
36031 This packets requests data about static tracepoint markers in the
36032 target program at @var{address}. Replies to this packet follow the
36033 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36034 tracepoint markers.
36036 @item QTSave:@var{filename}
36037 This packet directs the target to save trace data to the file name
36038 @var{filename} in the target's filesystem. @var{filename} is encoded
36039 as a hex string; the interpretation of the file name (relative vs
36040 absolute, wild cards, etc) is up to the target.
36042 @item qTBuffer:@var{offset},@var{len}
36043 Return up to @var{len} bytes of the current contents of trace buffer,
36044 starting at @var{offset}. The trace buffer is treated as if it were
36045 a contiguous collection of traceframes, as per the trace file format.
36046 The reply consists as many hex-encoded bytes as the target can deliver
36047 in a packet; it is not an error to return fewer than were asked for.
36048 A reply consisting of just @code{l} indicates that no bytes are
36051 @item QTBuffer:circular:@var{value}
36052 This packet directs the target to use a circular trace buffer if
36053 @var{value} is 1, or a linear buffer if the value is 0.
36055 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36056 This packet adds optional textual notes to the trace run. Allowable
36057 types include @code{user}, @code{notes}, and @code{tstop}, the
36058 @var{text} fields are arbitrary strings, hex-encoded.
36062 @subsection Relocate instruction reply packet
36063 When installing fast tracepoints in memory, the target may need to
36064 relocate the instruction currently at the tracepoint address to a
36065 different address in memory. For most instructions, a simple copy is
36066 enough, but, for example, call instructions that implicitly push the
36067 return address on the stack, and relative branches or other
36068 PC-relative instructions require offset adjustment, so that the effect
36069 of executing the instruction at a different address is the same as if
36070 it had executed in the original location.
36072 In response to several of the tracepoint packets, the target may also
36073 respond with a number of intermediate @samp{qRelocInsn} request
36074 packets before the final result packet, to have @value{GDBN} handle
36075 this relocation operation. If a packet supports this mechanism, its
36076 documentation will explicitly say so. See for example the above
36077 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36078 format of the request is:
36081 @item qRelocInsn:@var{from};@var{to}
36083 This requests @value{GDBN} to copy instruction at address @var{from}
36084 to address @var{to}, possibly adjusted so that executing the
36085 instruction at @var{to} has the same effect as executing it at
36086 @var{from}. @value{GDBN} writes the adjusted instruction to target
36087 memory starting at @var{to}.
36092 @item qRelocInsn:@var{adjusted_size}
36093 Informs the stub the relocation is complete. @var{adjusted_size} is
36094 the length in bytes of resulting relocated instruction sequence.
36096 A badly formed request was detected, or an error was encountered while
36097 relocating the instruction.
36100 @node Host I/O Packets
36101 @section Host I/O Packets
36102 @cindex Host I/O, remote protocol
36103 @cindex file transfer, remote protocol
36105 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36106 operations on the far side of a remote link. For example, Host I/O is
36107 used to upload and download files to a remote target with its own
36108 filesystem. Host I/O uses the same constant values and data structure
36109 layout as the target-initiated File-I/O protocol. However, the
36110 Host I/O packets are structured differently. The target-initiated
36111 protocol relies on target memory to store parameters and buffers.
36112 Host I/O requests are initiated by @value{GDBN}, and the
36113 target's memory is not involved. @xref{File-I/O Remote Protocol
36114 Extension}, for more details on the target-initiated protocol.
36116 The Host I/O request packets all encode a single operation along with
36117 its arguments. They have this format:
36121 @item vFile:@var{operation}: @var{parameter}@dots{}
36122 @var{operation} is the name of the particular request; the target
36123 should compare the entire packet name up to the second colon when checking
36124 for a supported operation. The format of @var{parameter} depends on
36125 the operation. Numbers are always passed in hexadecimal. Negative
36126 numbers have an explicit minus sign (i.e.@: two's complement is not
36127 used). Strings (e.g.@: filenames) are encoded as a series of
36128 hexadecimal bytes. The last argument to a system call may be a
36129 buffer of escaped binary data (@pxref{Binary Data}).
36133 The valid responses to Host I/O packets are:
36137 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36138 @var{result} is the integer value returned by this operation, usually
36139 non-negative for success and -1 for errors. If an error has occured,
36140 @var{errno} will be included in the result. @var{errno} will have a
36141 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36142 operations which return data, @var{attachment} supplies the data as a
36143 binary buffer. Binary buffers in response packets are escaped in the
36144 normal way (@pxref{Binary Data}). See the individual packet
36145 documentation for the interpretation of @var{result} and
36149 An empty response indicates that this operation is not recognized.
36153 These are the supported Host I/O operations:
36156 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36157 Open a file at @var{pathname} and return a file descriptor for it, or
36158 return -1 if an error occurs. @var{pathname} is a string,
36159 @var{flags} is an integer indicating a mask of open flags
36160 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36161 of mode bits to use if the file is created (@pxref{mode_t Values}).
36162 @xref{open}, for details of the open flags and mode values.
36164 @item vFile:close: @var{fd}
36165 Close the open file corresponding to @var{fd} and return 0, or
36166 -1 if an error occurs.
36168 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36169 Read data from the open file corresponding to @var{fd}. Up to
36170 @var{count} bytes will be read from the file, starting at @var{offset}
36171 relative to the start of the file. The target may read fewer bytes;
36172 common reasons include packet size limits and an end-of-file
36173 condition. The number of bytes read is returned. Zero should only be
36174 returned for a successful read at the end of the file, or if
36175 @var{count} was zero.
36177 The data read should be returned as a binary attachment on success.
36178 If zero bytes were read, the response should include an empty binary
36179 attachment (i.e.@: a trailing semicolon). The return value is the
36180 number of target bytes read; the binary attachment may be longer if
36181 some characters were escaped.
36183 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36184 Write @var{data} (a binary buffer) to the open file corresponding
36185 to @var{fd}. Start the write at @var{offset} from the start of the
36186 file. Unlike many @code{write} system calls, there is no
36187 separate @var{count} argument; the length of @var{data} in the
36188 packet is used. @samp{vFile:write} returns the number of bytes written,
36189 which may be shorter than the length of @var{data}, or -1 if an
36192 @item vFile:unlink: @var{pathname}
36193 Delete the file at @var{pathname} on the target. Return 0,
36194 or -1 if an error occurs. @var{pathname} is a string.
36199 @section Interrupts
36200 @cindex interrupts (remote protocol)
36202 When a program on the remote target is running, @value{GDBN} may
36203 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36204 a @code{BREAK} followed by @code{g},
36205 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36207 The precise meaning of @code{BREAK} is defined by the transport
36208 mechanism and may, in fact, be undefined. @value{GDBN} does not
36209 currently define a @code{BREAK} mechanism for any of the network
36210 interfaces except for TCP, in which case @value{GDBN} sends the
36211 @code{telnet} BREAK sequence.
36213 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36214 transport mechanisms. It is represented by sending the single byte
36215 @code{0x03} without any of the usual packet overhead described in
36216 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36217 transmitted as part of a packet, it is considered to be packet data
36218 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36219 (@pxref{X packet}), used for binary downloads, may include an unescaped
36220 @code{0x03} as part of its packet.
36222 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36223 When Linux kernel receives this sequence from serial port,
36224 it stops execution and connects to gdb.
36226 Stubs are not required to recognize these interrupt mechanisms and the
36227 precise meaning associated with receipt of the interrupt is
36228 implementation defined. If the target supports debugging of multiple
36229 threads and/or processes, it should attempt to interrupt all
36230 currently-executing threads and processes.
36231 If the stub is successful at interrupting the
36232 running program, it should send one of the stop
36233 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36234 of successfully stopping the program in all-stop mode, and a stop reply
36235 for each stopped thread in non-stop mode.
36236 Interrupts received while the
36237 program is stopped are discarded.
36239 @node Notification Packets
36240 @section Notification Packets
36241 @cindex notification packets
36242 @cindex packets, notification
36244 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36245 packets that require no acknowledgment. Both the GDB and the stub
36246 may send notifications (although the only notifications defined at
36247 present are sent by the stub). Notifications carry information
36248 without incurring the round-trip latency of an acknowledgment, and so
36249 are useful for low-impact communications where occasional packet loss
36252 A notification packet has the form @samp{% @var{data} #
36253 @var{checksum}}, where @var{data} is the content of the notification,
36254 and @var{checksum} is a checksum of @var{data}, computed and formatted
36255 as for ordinary @value{GDBN} packets. A notification's @var{data}
36256 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36257 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36258 to acknowledge the notification's receipt or to report its corruption.
36260 Every notification's @var{data} begins with a name, which contains no
36261 colon characters, followed by a colon character.
36263 Recipients should silently ignore corrupted notifications and
36264 notifications they do not understand. Recipients should restart
36265 timeout periods on receipt of a well-formed notification, whether or
36266 not they understand it.
36268 Senders should only send the notifications described here when this
36269 protocol description specifies that they are permitted. In the
36270 future, we may extend the protocol to permit existing notifications in
36271 new contexts; this rule helps older senders avoid confusing newer
36274 (Older versions of @value{GDBN} ignore bytes received until they see
36275 the @samp{$} byte that begins an ordinary packet, so new stubs may
36276 transmit notifications without fear of confusing older clients. There
36277 are no notifications defined for @value{GDBN} to send at the moment, but we
36278 assume that most older stubs would ignore them, as well.)
36280 The following notification packets from the stub to @value{GDBN} are
36284 @item Stop: @var{reply}
36285 Report an asynchronous stop event in non-stop mode.
36286 The @var{reply} has the form of a stop reply, as
36287 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36288 for information on how these notifications are acknowledged by
36292 @node Remote Non-Stop
36293 @section Remote Protocol Support for Non-Stop Mode
36295 @value{GDBN}'s remote protocol supports non-stop debugging of
36296 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36297 supports non-stop mode, it should report that to @value{GDBN} by including
36298 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36300 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36301 establishing a new connection with the stub. Entering non-stop mode
36302 does not alter the state of any currently-running threads, but targets
36303 must stop all threads in any already-attached processes when entering
36304 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36305 probe the target state after a mode change.
36307 In non-stop mode, when an attached process encounters an event that
36308 would otherwise be reported with a stop reply, it uses the
36309 asynchronous notification mechanism (@pxref{Notification Packets}) to
36310 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36311 in all processes are stopped when a stop reply is sent, in non-stop
36312 mode only the thread reporting the stop event is stopped. That is,
36313 when reporting a @samp{S} or @samp{T} response to indicate completion
36314 of a step operation, hitting a breakpoint, or a fault, only the
36315 affected thread is stopped; any other still-running threads continue
36316 to run. When reporting a @samp{W} or @samp{X} response, all running
36317 threads belonging to other attached processes continue to run.
36319 Only one stop reply notification at a time may be pending; if
36320 additional stop events occur before @value{GDBN} has acknowledged the
36321 previous notification, they must be queued by the stub for later
36322 synchronous transmission in response to @samp{vStopped} packets from
36323 @value{GDBN}. Because the notification mechanism is unreliable,
36324 the stub is permitted to resend a stop reply notification
36325 if it believes @value{GDBN} may not have received it. @value{GDBN}
36326 ignores additional stop reply notifications received before it has
36327 finished processing a previous notification and the stub has completed
36328 sending any queued stop events.
36330 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36331 notification at any time. Specifically, they may appear when
36332 @value{GDBN} is not otherwise reading input from the stub, or when
36333 @value{GDBN} is expecting to read a normal synchronous response or a
36334 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36335 Notification packets are distinct from any other communication from
36336 the stub so there is no ambiguity.
36338 After receiving a stop reply notification, @value{GDBN} shall
36339 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36340 as a regular, synchronous request to the stub. Such acknowledgment
36341 is not required to happen immediately, as @value{GDBN} is permitted to
36342 send other, unrelated packets to the stub first, which the stub should
36345 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36346 stop events to report to @value{GDBN}, it shall respond by sending a
36347 normal stop reply response. @value{GDBN} shall then send another
36348 @samp{vStopped} packet to solicit further responses; again, it is
36349 permitted to send other, unrelated packets as well which the stub
36350 should process normally.
36352 If the stub receives a @samp{vStopped} packet and there are no
36353 additional stop events to report, the stub shall return an @samp{OK}
36354 response. At this point, if further stop events occur, the stub shall
36355 send a new stop reply notification, @value{GDBN} shall accept the
36356 notification, and the process shall be repeated.
36358 In non-stop mode, the target shall respond to the @samp{?} packet as
36359 follows. First, any incomplete stop reply notification/@samp{vStopped}
36360 sequence in progress is abandoned. The target must begin a new
36361 sequence reporting stop events for all stopped threads, whether or not
36362 it has previously reported those events to @value{GDBN}. The first
36363 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36364 subsequent stop replies are sent as responses to @samp{vStopped} packets
36365 using the mechanism described above. The target must not send
36366 asynchronous stop reply notifications until the sequence is complete.
36367 If all threads are running when the target receives the @samp{?} packet,
36368 or if the target is not attached to any process, it shall respond
36371 @node Packet Acknowledgment
36372 @section Packet Acknowledgment
36374 @cindex acknowledgment, for @value{GDBN} remote
36375 @cindex packet acknowledgment, for @value{GDBN} remote
36376 By default, when either the host or the target machine receives a packet,
36377 the first response expected is an acknowledgment: either @samp{+} (to indicate
36378 the package was received correctly) or @samp{-} (to request retransmission).
36379 This mechanism allows the @value{GDBN} remote protocol to operate over
36380 unreliable transport mechanisms, such as a serial line.
36382 In cases where the transport mechanism is itself reliable (such as a pipe or
36383 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36384 It may be desirable to disable them in that case to reduce communication
36385 overhead, or for other reasons. This can be accomplished by means of the
36386 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36388 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36389 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36390 and response format still includes the normal checksum, as described in
36391 @ref{Overview}, but the checksum may be ignored by the receiver.
36393 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36394 no-acknowledgment mode, it should report that to @value{GDBN}
36395 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36396 @pxref{qSupported}.
36397 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36398 disabled via the @code{set remote noack-packet off} command
36399 (@pxref{Remote Configuration}),
36400 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36401 Only then may the stub actually turn off packet acknowledgments.
36402 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36403 response, which can be safely ignored by the stub.
36405 Note that @code{set remote noack-packet} command only affects negotiation
36406 between @value{GDBN} and the stub when subsequent connections are made;
36407 it does not affect the protocol acknowledgment state for any current
36409 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36410 new connection is established,
36411 there is also no protocol request to re-enable the acknowledgments
36412 for the current connection, once disabled.
36417 Example sequence of a target being re-started. Notice how the restart
36418 does not get any direct output:
36423 @emph{target restarts}
36426 <- @code{T001:1234123412341234}
36430 Example sequence of a target being stepped by a single instruction:
36433 -> @code{G1445@dots{}}
36438 <- @code{T001:1234123412341234}
36442 <- @code{1455@dots{}}
36446 @node File-I/O Remote Protocol Extension
36447 @section File-I/O Remote Protocol Extension
36448 @cindex File-I/O remote protocol extension
36451 * File-I/O Overview::
36452 * Protocol Basics::
36453 * The F Request Packet::
36454 * The F Reply Packet::
36455 * The Ctrl-C Message::
36457 * List of Supported Calls::
36458 * Protocol-specific Representation of Datatypes::
36460 * File-I/O Examples::
36463 @node File-I/O Overview
36464 @subsection File-I/O Overview
36465 @cindex file-i/o overview
36467 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36468 target to use the host's file system and console I/O to perform various
36469 system calls. System calls on the target system are translated into a
36470 remote protocol packet to the host system, which then performs the needed
36471 actions and returns a response packet to the target system.
36472 This simulates file system operations even on targets that lack file systems.
36474 The protocol is defined to be independent of both the host and target systems.
36475 It uses its own internal representation of datatypes and values. Both
36476 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36477 translating the system-dependent value representations into the internal
36478 protocol representations when data is transmitted.
36480 The communication is synchronous. A system call is possible only when
36481 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36482 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36483 the target is stopped to allow deterministic access to the target's
36484 memory. Therefore File-I/O is not interruptible by target signals. On
36485 the other hand, it is possible to interrupt File-I/O by a user interrupt
36486 (@samp{Ctrl-C}) within @value{GDBN}.
36488 The target's request to perform a host system call does not finish
36489 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36490 after finishing the system call, the target returns to continuing the
36491 previous activity (continue, step). No additional continue or step
36492 request from @value{GDBN} is required.
36495 (@value{GDBP}) continue
36496 <- target requests 'system call X'
36497 target is stopped, @value{GDBN} executes system call
36498 -> @value{GDBN} returns result
36499 ... target continues, @value{GDBN} returns to wait for the target
36500 <- target hits breakpoint and sends a Txx packet
36503 The protocol only supports I/O on the console and to regular files on
36504 the host file system. Character or block special devices, pipes,
36505 named pipes, sockets or any other communication method on the host
36506 system are not supported by this protocol.
36508 File I/O is not supported in non-stop mode.
36510 @node Protocol Basics
36511 @subsection Protocol Basics
36512 @cindex protocol basics, file-i/o
36514 The File-I/O protocol uses the @code{F} packet as the request as well
36515 as reply packet. Since a File-I/O system call can only occur when
36516 @value{GDBN} is waiting for a response from the continuing or stepping target,
36517 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36518 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36519 This @code{F} packet contains all information needed to allow @value{GDBN}
36520 to call the appropriate host system call:
36524 A unique identifier for the requested system call.
36527 All parameters to the system call. Pointers are given as addresses
36528 in the target memory address space. Pointers to strings are given as
36529 pointer/length pair. Numerical values are given as they are.
36530 Numerical control flags are given in a protocol-specific representation.
36534 At this point, @value{GDBN} has to perform the following actions.
36538 If the parameters include pointer values to data needed as input to a
36539 system call, @value{GDBN} requests this data from the target with a
36540 standard @code{m} packet request. This additional communication has to be
36541 expected by the target implementation and is handled as any other @code{m}
36545 @value{GDBN} translates all value from protocol representation to host
36546 representation as needed. Datatypes are coerced into the host types.
36549 @value{GDBN} calls the system call.
36552 It then coerces datatypes back to protocol representation.
36555 If the system call is expected to return data in buffer space specified
36556 by pointer parameters to the call, the data is transmitted to the
36557 target using a @code{M} or @code{X} packet. This packet has to be expected
36558 by the target implementation and is handled as any other @code{M} or @code{X}
36563 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36564 necessary information for the target to continue. This at least contains
36571 @code{errno}, if has been changed by the system call.
36578 After having done the needed type and value coercion, the target continues
36579 the latest continue or step action.
36581 @node The F Request Packet
36582 @subsection The @code{F} Request Packet
36583 @cindex file-i/o request packet
36584 @cindex @code{F} request packet
36586 The @code{F} request packet has the following format:
36589 @item F@var{call-id},@var{parameter@dots{}}
36591 @var{call-id} is the identifier to indicate the host system call to be called.
36592 This is just the name of the function.
36594 @var{parameter@dots{}} are the parameters to the system call.
36595 Parameters are hexadecimal integer values, either the actual values in case
36596 of scalar datatypes, pointers to target buffer space in case of compound
36597 datatypes and unspecified memory areas, or pointer/length pairs in case
36598 of string parameters. These are appended to the @var{call-id} as a
36599 comma-delimited list. All values are transmitted in ASCII
36600 string representation, pointer/length pairs separated by a slash.
36606 @node The F Reply Packet
36607 @subsection The @code{F} Reply Packet
36608 @cindex file-i/o reply packet
36609 @cindex @code{F} reply packet
36611 The @code{F} reply packet has the following format:
36615 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36617 @var{retcode} is the return code of the system call as hexadecimal value.
36619 @var{errno} is the @code{errno} set by the call, in protocol-specific
36621 This parameter can be omitted if the call was successful.
36623 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36624 case, @var{errno} must be sent as well, even if the call was successful.
36625 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36632 or, if the call was interrupted before the host call has been performed:
36639 assuming 4 is the protocol-specific representation of @code{EINTR}.
36644 @node The Ctrl-C Message
36645 @subsection The @samp{Ctrl-C} Message
36646 @cindex ctrl-c message, in file-i/o protocol
36648 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36649 reply packet (@pxref{The F Reply Packet}),
36650 the target should behave as if it had
36651 gotten a break message. The meaning for the target is ``system call
36652 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36653 (as with a break message) and return to @value{GDBN} with a @code{T02}
36656 It's important for the target to know in which
36657 state the system call was interrupted. There are two possible cases:
36661 The system call hasn't been performed on the host yet.
36664 The system call on the host has been finished.
36668 These two states can be distinguished by the target by the value of the
36669 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36670 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36671 on POSIX systems. In any other case, the target may presume that the
36672 system call has been finished --- successfully or not --- and should behave
36673 as if the break message arrived right after the system call.
36675 @value{GDBN} must behave reliably. If the system call has not been called
36676 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36677 @code{errno} in the packet. If the system call on the host has been finished
36678 before the user requests a break, the full action must be finished by
36679 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36680 The @code{F} packet may only be sent when either nothing has happened
36681 or the full action has been completed.
36684 @subsection Console I/O
36685 @cindex console i/o as part of file-i/o
36687 By default and if not explicitly closed by the target system, the file
36688 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36689 on the @value{GDBN} console is handled as any other file output operation
36690 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36691 by @value{GDBN} so that after the target read request from file descriptor
36692 0 all following typing is buffered until either one of the following
36697 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36699 system call is treated as finished.
36702 The user presses @key{RET}. This is treated as end of input with a trailing
36706 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36707 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36711 If the user has typed more characters than fit in the buffer given to
36712 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36713 either another @code{read(0, @dots{})} is requested by the target, or debugging
36714 is stopped at the user's request.
36717 @node List of Supported Calls
36718 @subsection List of Supported Calls
36719 @cindex list of supported file-i/o calls
36736 @unnumberedsubsubsec open
36737 @cindex open, file-i/o system call
36742 int open(const char *pathname, int flags);
36743 int open(const char *pathname, int flags, mode_t mode);
36747 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36750 @var{flags} is the bitwise @code{OR} of the following values:
36754 If the file does not exist it will be created. The host
36755 rules apply as far as file ownership and time stamps
36759 When used with @code{O_CREAT}, if the file already exists it is
36760 an error and open() fails.
36763 If the file already exists and the open mode allows
36764 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36765 truncated to zero length.
36768 The file is opened in append mode.
36771 The file is opened for reading only.
36774 The file is opened for writing only.
36777 The file is opened for reading and writing.
36781 Other bits are silently ignored.
36785 @var{mode} is the bitwise @code{OR} of the following values:
36789 User has read permission.
36792 User has write permission.
36795 Group has read permission.
36798 Group has write permission.
36801 Others have read permission.
36804 Others have write permission.
36808 Other bits are silently ignored.
36811 @item Return value:
36812 @code{open} returns the new file descriptor or -1 if an error
36819 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36822 @var{pathname} refers to a directory.
36825 The requested access is not allowed.
36828 @var{pathname} was too long.
36831 A directory component in @var{pathname} does not exist.
36834 @var{pathname} refers to a device, pipe, named pipe or socket.
36837 @var{pathname} refers to a file on a read-only filesystem and
36838 write access was requested.
36841 @var{pathname} is an invalid pointer value.
36844 No space on device to create the file.
36847 The process already has the maximum number of files open.
36850 The limit on the total number of files open on the system
36854 The call was interrupted by the user.
36860 @unnumberedsubsubsec close
36861 @cindex close, file-i/o system call
36870 @samp{Fclose,@var{fd}}
36872 @item Return value:
36873 @code{close} returns zero on success, or -1 if an error occurred.
36879 @var{fd} isn't a valid open file descriptor.
36882 The call was interrupted by the user.
36888 @unnumberedsubsubsec read
36889 @cindex read, file-i/o system call
36894 int read(int fd, void *buf, unsigned int count);
36898 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36900 @item Return value:
36901 On success, the number of bytes read is returned.
36902 Zero indicates end of file. If count is zero, read
36903 returns zero as well. On error, -1 is returned.
36909 @var{fd} is not a valid file descriptor or is not open for
36913 @var{bufptr} is an invalid pointer value.
36916 The call was interrupted by the user.
36922 @unnumberedsubsubsec write
36923 @cindex write, file-i/o system call
36928 int write(int fd, const void *buf, unsigned int count);
36932 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36934 @item Return value:
36935 On success, the number of bytes written are returned.
36936 Zero indicates nothing was written. On error, -1
36943 @var{fd} is not a valid file descriptor or is not open for
36947 @var{bufptr} is an invalid pointer value.
36950 An attempt was made to write a file that exceeds the
36951 host-specific maximum file size allowed.
36954 No space on device to write the data.
36957 The call was interrupted by the user.
36963 @unnumberedsubsubsec lseek
36964 @cindex lseek, file-i/o system call
36969 long lseek (int fd, long offset, int flag);
36973 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36975 @var{flag} is one of:
36979 The offset is set to @var{offset} bytes.
36982 The offset is set to its current location plus @var{offset}
36986 The offset is set to the size of the file plus @var{offset}
36990 @item Return value:
36991 On success, the resulting unsigned offset in bytes from
36992 the beginning of the file is returned. Otherwise, a
36993 value of -1 is returned.
36999 @var{fd} is not a valid open file descriptor.
37002 @var{fd} is associated with the @value{GDBN} console.
37005 @var{flag} is not a proper value.
37008 The call was interrupted by the user.
37014 @unnumberedsubsubsec rename
37015 @cindex rename, file-i/o system call
37020 int rename(const char *oldpath, const char *newpath);
37024 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37026 @item Return value:
37027 On success, zero is returned. On error, -1 is returned.
37033 @var{newpath} is an existing directory, but @var{oldpath} is not a
37037 @var{newpath} is a non-empty directory.
37040 @var{oldpath} or @var{newpath} is a directory that is in use by some
37044 An attempt was made to make a directory a subdirectory
37048 A component used as a directory in @var{oldpath} or new
37049 path is not a directory. Or @var{oldpath} is a directory
37050 and @var{newpath} exists but is not a directory.
37053 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37056 No access to the file or the path of the file.
37060 @var{oldpath} or @var{newpath} was too long.
37063 A directory component in @var{oldpath} or @var{newpath} does not exist.
37066 The file is on a read-only filesystem.
37069 The device containing the file has no room for the new
37073 The call was interrupted by the user.
37079 @unnumberedsubsubsec unlink
37080 @cindex unlink, file-i/o system call
37085 int unlink(const char *pathname);
37089 @samp{Funlink,@var{pathnameptr}/@var{len}}
37091 @item Return value:
37092 On success, zero is returned. On error, -1 is returned.
37098 No access to the file or the path of the file.
37101 The system does not allow unlinking of directories.
37104 The file @var{pathname} cannot be unlinked because it's
37105 being used by another process.
37108 @var{pathnameptr} is an invalid pointer value.
37111 @var{pathname} was too long.
37114 A directory component in @var{pathname} does not exist.
37117 A component of the path is not a directory.
37120 The file is on a read-only filesystem.
37123 The call was interrupted by the user.
37129 @unnumberedsubsubsec stat/fstat
37130 @cindex fstat, file-i/o system call
37131 @cindex stat, file-i/o system call
37136 int stat(const char *pathname, struct stat *buf);
37137 int fstat(int fd, struct stat *buf);
37141 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37142 @samp{Ffstat,@var{fd},@var{bufptr}}
37144 @item Return value:
37145 On success, zero is returned. On error, -1 is returned.
37151 @var{fd} is not a valid open file.
37154 A directory component in @var{pathname} does not exist or the
37155 path is an empty string.
37158 A component of the path is not a directory.
37161 @var{pathnameptr} is an invalid pointer value.
37164 No access to the file or the path of the file.
37167 @var{pathname} was too long.
37170 The call was interrupted by the user.
37176 @unnumberedsubsubsec gettimeofday
37177 @cindex gettimeofday, file-i/o system call
37182 int gettimeofday(struct timeval *tv, void *tz);
37186 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37188 @item Return value:
37189 On success, 0 is returned, -1 otherwise.
37195 @var{tz} is a non-NULL pointer.
37198 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37204 @unnumberedsubsubsec isatty
37205 @cindex isatty, file-i/o system call
37210 int isatty(int fd);
37214 @samp{Fisatty,@var{fd}}
37216 @item Return value:
37217 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37223 The call was interrupted by the user.
37228 Note that the @code{isatty} call is treated as a special case: it returns
37229 1 to the target if the file descriptor is attached
37230 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37231 would require implementing @code{ioctl} and would be more complex than
37236 @unnumberedsubsubsec system
37237 @cindex system, file-i/o system call
37242 int system(const char *command);
37246 @samp{Fsystem,@var{commandptr}/@var{len}}
37248 @item Return value:
37249 If @var{len} is zero, the return value indicates whether a shell is
37250 available. A zero return value indicates a shell is not available.
37251 For non-zero @var{len}, the value returned is -1 on error and the
37252 return status of the command otherwise. Only the exit status of the
37253 command is returned, which is extracted from the host's @code{system}
37254 return value by calling @code{WEXITSTATUS(retval)}. In case
37255 @file{/bin/sh} could not be executed, 127 is returned.
37261 The call was interrupted by the user.
37266 @value{GDBN} takes over the full task of calling the necessary host calls
37267 to perform the @code{system} call. The return value of @code{system} on
37268 the host is simplified before it's returned
37269 to the target. Any termination signal information from the child process
37270 is discarded, and the return value consists
37271 entirely of the exit status of the called command.
37273 Due to security concerns, the @code{system} call is by default refused
37274 by @value{GDBN}. The user has to allow this call explicitly with the
37275 @code{set remote system-call-allowed 1} command.
37278 @item set remote system-call-allowed
37279 @kindex set remote system-call-allowed
37280 Control whether to allow the @code{system} calls in the File I/O
37281 protocol for the remote target. The default is zero (disabled).
37283 @item show remote system-call-allowed
37284 @kindex show remote system-call-allowed
37285 Show whether the @code{system} calls are allowed in the File I/O
37289 @node Protocol-specific Representation of Datatypes
37290 @subsection Protocol-specific Representation of Datatypes
37291 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37294 * Integral Datatypes::
37296 * Memory Transfer::
37301 @node Integral Datatypes
37302 @unnumberedsubsubsec Integral Datatypes
37303 @cindex integral datatypes, in file-i/o protocol
37305 The integral datatypes used in the system calls are @code{int},
37306 @code{unsigned int}, @code{long}, @code{unsigned long},
37307 @code{mode_t}, and @code{time_t}.
37309 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37310 implemented as 32 bit values in this protocol.
37312 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37314 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37315 in @file{limits.h}) to allow range checking on host and target.
37317 @code{time_t} datatypes are defined as seconds since the Epoch.
37319 All integral datatypes transferred as part of a memory read or write of a
37320 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37323 @node Pointer Values
37324 @unnumberedsubsubsec Pointer Values
37325 @cindex pointer values, in file-i/o protocol
37327 Pointers to target data are transmitted as they are. An exception
37328 is made for pointers to buffers for which the length isn't
37329 transmitted as part of the function call, namely strings. Strings
37330 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37337 which is a pointer to data of length 18 bytes at position 0x1aaf.
37338 The length is defined as the full string length in bytes, including
37339 the trailing null byte. For example, the string @code{"hello world"}
37340 at address 0x123456 is transmitted as
37346 @node Memory Transfer
37347 @unnumberedsubsubsec Memory Transfer
37348 @cindex memory transfer, in file-i/o protocol
37350 Structured data which is transferred using a memory read or write (for
37351 example, a @code{struct stat}) is expected to be in a protocol-specific format
37352 with all scalar multibyte datatypes being big endian. Translation to
37353 this representation needs to be done both by the target before the @code{F}
37354 packet is sent, and by @value{GDBN} before
37355 it transfers memory to the target. Transferred pointers to structured
37356 data should point to the already-coerced data at any time.
37360 @unnumberedsubsubsec struct stat
37361 @cindex struct stat, in file-i/o protocol
37363 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37364 is defined as follows:
37368 unsigned int st_dev; /* device */
37369 unsigned int st_ino; /* inode */
37370 mode_t st_mode; /* protection */
37371 unsigned int st_nlink; /* number of hard links */
37372 unsigned int st_uid; /* user ID of owner */
37373 unsigned int st_gid; /* group ID of owner */
37374 unsigned int st_rdev; /* device type (if inode device) */
37375 unsigned long st_size; /* total size, in bytes */
37376 unsigned long st_blksize; /* blocksize for filesystem I/O */
37377 unsigned long st_blocks; /* number of blocks allocated */
37378 time_t st_atime; /* time of last access */
37379 time_t st_mtime; /* time of last modification */
37380 time_t st_ctime; /* time of last change */
37384 The integral datatypes conform to the definitions given in the
37385 appropriate section (see @ref{Integral Datatypes}, for details) so this
37386 structure is of size 64 bytes.
37388 The values of several fields have a restricted meaning and/or
37394 A value of 0 represents a file, 1 the console.
37397 No valid meaning for the target. Transmitted unchanged.
37400 Valid mode bits are described in @ref{Constants}. Any other
37401 bits have currently no meaning for the target.
37406 No valid meaning for the target. Transmitted unchanged.
37411 These values have a host and file system dependent
37412 accuracy. Especially on Windows hosts, the file system may not
37413 support exact timing values.
37416 The target gets a @code{struct stat} of the above representation and is
37417 responsible for coercing it to the target representation before
37420 Note that due to size differences between the host, target, and protocol
37421 representations of @code{struct stat} members, these members could eventually
37422 get truncated on the target.
37424 @node struct timeval
37425 @unnumberedsubsubsec struct timeval
37426 @cindex struct timeval, in file-i/o protocol
37428 The buffer of type @code{struct timeval} used by the File-I/O protocol
37429 is defined as follows:
37433 time_t tv_sec; /* second */
37434 long tv_usec; /* microsecond */
37438 The integral datatypes conform to the definitions given in the
37439 appropriate section (see @ref{Integral Datatypes}, for details) so this
37440 structure is of size 8 bytes.
37443 @subsection Constants
37444 @cindex constants, in file-i/o protocol
37446 The following values are used for the constants inside of the
37447 protocol. @value{GDBN} and target are responsible for translating these
37448 values before and after the call as needed.
37459 @unnumberedsubsubsec Open Flags
37460 @cindex open flags, in file-i/o protocol
37462 All values are given in hexadecimal representation.
37474 @node mode_t Values
37475 @unnumberedsubsubsec mode_t Values
37476 @cindex mode_t values, in file-i/o protocol
37478 All values are given in octal representation.
37495 @unnumberedsubsubsec Errno Values
37496 @cindex errno values, in file-i/o protocol
37498 All values are given in decimal representation.
37523 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37524 any error value not in the list of supported error numbers.
37527 @unnumberedsubsubsec Lseek Flags
37528 @cindex lseek flags, in file-i/o protocol
37537 @unnumberedsubsubsec Limits
37538 @cindex limits, in file-i/o protocol
37540 All values are given in decimal representation.
37543 INT_MIN -2147483648
37545 UINT_MAX 4294967295
37546 LONG_MIN -9223372036854775808
37547 LONG_MAX 9223372036854775807
37548 ULONG_MAX 18446744073709551615
37551 @node File-I/O Examples
37552 @subsection File-I/O Examples
37553 @cindex file-i/o examples
37555 Example sequence of a write call, file descriptor 3, buffer is at target
37556 address 0x1234, 6 bytes should be written:
37559 <- @code{Fwrite,3,1234,6}
37560 @emph{request memory read from target}
37563 @emph{return "6 bytes written"}
37567 Example sequence of a read call, file descriptor 3, buffer is at target
37568 address 0x1234, 6 bytes should be read:
37571 <- @code{Fread,3,1234,6}
37572 @emph{request memory write to target}
37573 -> @code{X1234,6:XXXXXX}
37574 @emph{return "6 bytes read"}
37578 Example sequence of a read call, call fails on the host due to invalid
37579 file descriptor (@code{EBADF}):
37582 <- @code{Fread,3,1234,6}
37586 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37590 <- @code{Fread,3,1234,6}
37595 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37599 <- @code{Fread,3,1234,6}
37600 -> @code{X1234,6:XXXXXX}
37604 @node Library List Format
37605 @section Library List Format
37606 @cindex library list format, remote protocol
37608 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37609 same process as your application to manage libraries. In this case,
37610 @value{GDBN} can use the loader's symbol table and normal memory
37611 operations to maintain a list of shared libraries. On other
37612 platforms, the operating system manages loaded libraries.
37613 @value{GDBN} can not retrieve the list of currently loaded libraries
37614 through memory operations, so it uses the @samp{qXfer:libraries:read}
37615 packet (@pxref{qXfer library list read}) instead. The remote stub
37616 queries the target's operating system and reports which libraries
37619 The @samp{qXfer:libraries:read} packet returns an XML document which
37620 lists loaded libraries and their offsets. Each library has an
37621 associated name and one or more segment or section base addresses,
37622 which report where the library was loaded in memory.
37624 For the common case of libraries that are fully linked binaries, the
37625 library should have a list of segments. If the target supports
37626 dynamic linking of a relocatable object file, its library XML element
37627 should instead include a list of allocated sections. The segment or
37628 section bases are start addresses, not relocation offsets; they do not
37629 depend on the library's link-time base addresses.
37631 @value{GDBN} must be linked with the Expat library to support XML
37632 library lists. @xref{Expat}.
37634 A simple memory map, with one loaded library relocated by a single
37635 offset, looks like this:
37639 <library name="/lib/libc.so.6">
37640 <segment address="0x10000000"/>
37645 Another simple memory map, with one loaded library with three
37646 allocated sections (.text, .data, .bss), looks like this:
37650 <library name="sharedlib.o">
37651 <section address="0x10000000"/>
37652 <section address="0x20000000"/>
37653 <section address="0x30000000"/>
37658 The format of a library list is described by this DTD:
37661 <!-- library-list: Root element with versioning -->
37662 <!ELEMENT library-list (library)*>
37663 <!ATTLIST library-list version CDATA #FIXED "1.0">
37664 <!ELEMENT library (segment*, section*)>
37665 <!ATTLIST library name CDATA #REQUIRED>
37666 <!ELEMENT segment EMPTY>
37667 <!ATTLIST segment address CDATA #REQUIRED>
37668 <!ELEMENT section EMPTY>
37669 <!ATTLIST section address CDATA #REQUIRED>
37672 In addition, segments and section descriptors cannot be mixed within a
37673 single library element, and you must supply at least one segment or
37674 section for each library.
37676 @node Library List Format for SVR4 Targets
37677 @section Library List Format for SVR4 Targets
37678 @cindex library list format, remote protocol
37680 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37681 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37682 shared libraries. Still a special library list provided by this packet is
37683 more efficient for the @value{GDBN} remote protocol.
37685 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37686 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37687 target, the following parameters are reported:
37691 @code{name}, the absolute file name from the @code{l_name} field of
37692 @code{struct link_map}.
37694 @code{lm} with address of @code{struct link_map} used for TLS
37695 (Thread Local Storage) access.
37697 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37698 @code{struct link_map}. For prelinked libraries this is not an absolute
37699 memory address. It is a displacement of absolute memory address against
37700 address the file was prelinked to during the library load.
37702 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37705 Additionally the single @code{main-lm} attribute specifies address of
37706 @code{struct link_map} used for the main executable. This parameter is used
37707 for TLS access and its presence is optional.
37709 @value{GDBN} must be linked with the Expat library to support XML
37710 SVR4 library lists. @xref{Expat}.
37712 A simple memory map, with two loaded libraries (which do not use prelink),
37716 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37717 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37719 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37721 </library-list-svr>
37724 The format of an SVR4 library list is described by this DTD:
37727 <!-- library-list-svr4: Root element with versioning -->
37728 <!ELEMENT library-list-svr4 (library)*>
37729 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37730 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37731 <!ELEMENT library EMPTY>
37732 <!ATTLIST library name CDATA #REQUIRED>
37733 <!ATTLIST library lm CDATA #REQUIRED>
37734 <!ATTLIST library l_addr CDATA #REQUIRED>
37735 <!ATTLIST library l_ld CDATA #REQUIRED>
37738 @node Memory Map Format
37739 @section Memory Map Format
37740 @cindex memory map format
37742 To be able to write into flash memory, @value{GDBN} needs to obtain a
37743 memory map from the target. This section describes the format of the
37746 The memory map is obtained using the @samp{qXfer:memory-map:read}
37747 (@pxref{qXfer memory map read}) packet and is an XML document that
37748 lists memory regions.
37750 @value{GDBN} must be linked with the Expat library to support XML
37751 memory maps. @xref{Expat}.
37753 The top-level structure of the document is shown below:
37756 <?xml version="1.0"?>
37757 <!DOCTYPE memory-map
37758 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37759 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37765 Each region can be either:
37770 A region of RAM starting at @var{addr} and extending for @var{length}
37774 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37779 A region of read-only memory:
37782 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37787 A region of flash memory, with erasure blocks @var{blocksize}
37791 <memory type="flash" start="@var{addr}" length="@var{length}">
37792 <property name="blocksize">@var{blocksize}</property>
37798 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37799 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37800 packets to write to addresses in such ranges.
37802 The formal DTD for memory map format is given below:
37805 <!-- ................................................... -->
37806 <!-- Memory Map XML DTD ................................ -->
37807 <!-- File: memory-map.dtd .............................. -->
37808 <!-- .................................... .............. -->
37809 <!-- memory-map.dtd -->
37810 <!-- memory-map: Root element with versioning -->
37811 <!ELEMENT memory-map (memory | property)>
37812 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37813 <!ELEMENT memory (property)>
37814 <!-- memory: Specifies a memory region,
37815 and its type, or device. -->
37816 <!ATTLIST memory type CDATA #REQUIRED
37817 start CDATA #REQUIRED
37818 length CDATA #REQUIRED
37819 device CDATA #IMPLIED>
37820 <!-- property: Generic attribute tag -->
37821 <!ELEMENT property (#PCDATA | property)*>
37822 <!ATTLIST property name CDATA #REQUIRED>
37825 @node Thread List Format
37826 @section Thread List Format
37827 @cindex thread list format
37829 To efficiently update the list of threads and their attributes,
37830 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37831 (@pxref{qXfer threads read}) and obtains the XML document with
37832 the following structure:
37835 <?xml version="1.0"?>
37837 <thread id="id" core="0">
37838 ... description ...
37843 Each @samp{thread} element must have the @samp{id} attribute that
37844 identifies the thread (@pxref{thread-id syntax}). The
37845 @samp{core} attribute, if present, specifies which processor core
37846 the thread was last executing on. The content of the of @samp{thread}
37847 element is interpreted as human-readable auxilliary information.
37849 @node Traceframe Info Format
37850 @section Traceframe Info Format
37851 @cindex traceframe info format
37853 To be able to know which objects in the inferior can be examined when
37854 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37855 memory ranges, registers and trace state variables that have been
37856 collected in a traceframe.
37858 This list is obtained using the @samp{qXfer:traceframe-info:read}
37859 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37861 @value{GDBN} must be linked with the Expat library to support XML
37862 traceframe info discovery. @xref{Expat}.
37864 The top-level structure of the document is shown below:
37867 <?xml version="1.0"?>
37868 <!DOCTYPE traceframe-info
37869 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37870 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37876 Each traceframe block can be either:
37881 A region of collected memory starting at @var{addr} and extending for
37882 @var{length} bytes from there:
37885 <memory start="@var{addr}" length="@var{length}"/>
37890 The formal DTD for the traceframe info format is given below:
37893 <!ELEMENT traceframe-info (memory)* >
37894 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37896 <!ELEMENT memory EMPTY>
37897 <!ATTLIST memory start CDATA #REQUIRED
37898 length CDATA #REQUIRED>
37901 @include agentexpr.texi
37903 @node Target Descriptions
37904 @appendix Target Descriptions
37905 @cindex target descriptions
37907 One of the challenges of using @value{GDBN} to debug embedded systems
37908 is that there are so many minor variants of each processor
37909 architecture in use. It is common practice for vendors to start with
37910 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37911 and then make changes to adapt it to a particular market niche. Some
37912 architectures have hundreds of variants, available from dozens of
37913 vendors. This leads to a number of problems:
37917 With so many different customized processors, it is difficult for
37918 the @value{GDBN} maintainers to keep up with the changes.
37920 Since individual variants may have short lifetimes or limited
37921 audiences, it may not be worthwhile to carry information about every
37922 variant in the @value{GDBN} source tree.
37924 When @value{GDBN} does support the architecture of the embedded system
37925 at hand, the task of finding the correct architecture name to give the
37926 @command{set architecture} command can be error-prone.
37929 To address these problems, the @value{GDBN} remote protocol allows a
37930 target system to not only identify itself to @value{GDBN}, but to
37931 actually describe its own features. This lets @value{GDBN} support
37932 processor variants it has never seen before --- to the extent that the
37933 descriptions are accurate, and that @value{GDBN} understands them.
37935 @value{GDBN} must be linked with the Expat library to support XML
37936 target descriptions. @xref{Expat}.
37939 * Retrieving Descriptions:: How descriptions are fetched from a target.
37940 * Target Description Format:: The contents of a target description.
37941 * Predefined Target Types:: Standard types available for target
37943 * Standard Target Features:: Features @value{GDBN} knows about.
37946 @node Retrieving Descriptions
37947 @section Retrieving Descriptions
37949 Target descriptions can be read from the target automatically, or
37950 specified by the user manually. The default behavior is to read the
37951 description from the target. @value{GDBN} retrieves it via the remote
37952 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37953 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37954 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37955 XML document, of the form described in @ref{Target Description
37958 Alternatively, you can specify a file to read for the target description.
37959 If a file is set, the target will not be queried. The commands to
37960 specify a file are:
37963 @cindex set tdesc filename
37964 @item set tdesc filename @var{path}
37965 Read the target description from @var{path}.
37967 @cindex unset tdesc filename
37968 @item unset tdesc filename
37969 Do not read the XML target description from a file. @value{GDBN}
37970 will use the description supplied by the current target.
37972 @cindex show tdesc filename
37973 @item show tdesc filename
37974 Show the filename to read for a target description, if any.
37978 @node Target Description Format
37979 @section Target Description Format
37980 @cindex target descriptions, XML format
37982 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37983 document which complies with the Document Type Definition provided in
37984 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37985 means you can use generally available tools like @command{xmllint} to
37986 check that your feature descriptions are well-formed and valid.
37987 However, to help people unfamiliar with XML write descriptions for
37988 their targets, we also describe the grammar here.
37990 Target descriptions can identify the architecture of the remote target
37991 and (for some architectures) provide information about custom register
37992 sets. They can also identify the OS ABI of the remote target.
37993 @value{GDBN} can use this information to autoconfigure for your
37994 target, or to warn you if you connect to an unsupported target.
37996 Here is a simple target description:
37999 <target version="1.0">
38000 <architecture>i386:x86-64</architecture>
38005 This minimal description only says that the target uses
38006 the x86-64 architecture.
38008 A target description has the following overall form, with [ ] marking
38009 optional elements and @dots{} marking repeatable elements. The elements
38010 are explained further below.
38013 <?xml version="1.0"?>
38014 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38015 <target version="1.0">
38016 @r{[}@var{architecture}@r{]}
38017 @r{[}@var{osabi}@r{]}
38018 @r{[}@var{compatible}@r{]}
38019 @r{[}@var{feature}@dots{}@r{]}
38024 The description is generally insensitive to whitespace and line
38025 breaks, under the usual common-sense rules. The XML version
38026 declaration and document type declaration can generally be omitted
38027 (@value{GDBN} does not require them), but specifying them may be
38028 useful for XML validation tools. The @samp{version} attribute for
38029 @samp{<target>} may also be omitted, but we recommend
38030 including it; if future versions of @value{GDBN} use an incompatible
38031 revision of @file{gdb-target.dtd}, they will detect and report
38032 the version mismatch.
38034 @subsection Inclusion
38035 @cindex target descriptions, inclusion
38038 @cindex <xi:include>
38041 It can sometimes be valuable to split a target description up into
38042 several different annexes, either for organizational purposes, or to
38043 share files between different possible target descriptions. You can
38044 divide a description into multiple files by replacing any element of
38045 the target description with an inclusion directive of the form:
38048 <xi:include href="@var{document}"/>
38052 When @value{GDBN} encounters an element of this form, it will retrieve
38053 the named XML @var{document}, and replace the inclusion directive with
38054 the contents of that document. If the current description was read
38055 using @samp{qXfer}, then so will be the included document;
38056 @var{document} will be interpreted as the name of an annex. If the
38057 current description was read from a file, @value{GDBN} will look for
38058 @var{document} as a file in the same directory where it found the
38059 original description.
38061 @subsection Architecture
38062 @cindex <architecture>
38064 An @samp{<architecture>} element has this form:
38067 <architecture>@var{arch}</architecture>
38070 @var{arch} is one of the architectures from the set accepted by
38071 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38074 @cindex @code{<osabi>}
38076 This optional field was introduced in @value{GDBN} version 7.0.
38077 Previous versions of @value{GDBN} ignore it.
38079 An @samp{<osabi>} element has this form:
38082 <osabi>@var{abi-name}</osabi>
38085 @var{abi-name} is an OS ABI name from the same selection accepted by
38086 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38088 @subsection Compatible Architecture
38089 @cindex @code{<compatible>}
38091 This optional field was introduced in @value{GDBN} version 7.0.
38092 Previous versions of @value{GDBN} ignore it.
38094 A @samp{<compatible>} element has this form:
38097 <compatible>@var{arch}</compatible>
38100 @var{arch} is one of the architectures from the set accepted by
38101 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38103 A @samp{<compatible>} element is used to specify that the target
38104 is able to run binaries in some other than the main target architecture
38105 given by the @samp{<architecture>} element. For example, on the
38106 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38107 or @code{powerpc:common64}, but the system is able to run binaries
38108 in the @code{spu} architecture as well. The way to describe this
38109 capability with @samp{<compatible>} is as follows:
38112 <architecture>powerpc:common</architecture>
38113 <compatible>spu</compatible>
38116 @subsection Features
38119 Each @samp{<feature>} describes some logical portion of the target
38120 system. Features are currently used to describe available CPU
38121 registers and the types of their contents. A @samp{<feature>} element
38125 <feature name="@var{name}">
38126 @r{[}@var{type}@dots{}@r{]}
38132 Each feature's name should be unique within the description. The name
38133 of a feature does not matter unless @value{GDBN} has some special
38134 knowledge of the contents of that feature; if it does, the feature
38135 should have its standard name. @xref{Standard Target Features}.
38139 Any register's value is a collection of bits which @value{GDBN} must
38140 interpret. The default interpretation is a two's complement integer,
38141 but other types can be requested by name in the register description.
38142 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38143 Target Types}), and the description can define additional composite types.
38145 Each type element must have an @samp{id} attribute, which gives
38146 a unique (within the containing @samp{<feature>}) name to the type.
38147 Types must be defined before they are used.
38150 Some targets offer vector registers, which can be treated as arrays
38151 of scalar elements. These types are written as @samp{<vector>} elements,
38152 specifying the array element type, @var{type}, and the number of elements,
38156 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38160 If a register's value is usefully viewed in multiple ways, define it
38161 with a union type containing the useful representations. The
38162 @samp{<union>} element contains one or more @samp{<field>} elements,
38163 each of which has a @var{name} and a @var{type}:
38166 <union id="@var{id}">
38167 <field name="@var{name}" type="@var{type}"/>
38173 If a register's value is composed from several separate values, define
38174 it with a structure type. There are two forms of the @samp{<struct>}
38175 element; a @samp{<struct>} element must either contain only bitfields
38176 or contain no bitfields. If the structure contains only bitfields,
38177 its total size in bytes must be specified, each bitfield must have an
38178 explicit start and end, and bitfields are automatically assigned an
38179 integer type. The field's @var{start} should be less than or
38180 equal to its @var{end}, and zero represents the least significant bit.
38183 <struct id="@var{id}" size="@var{size}">
38184 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38189 If the structure contains no bitfields, then each field has an
38190 explicit type, and no implicit padding is added.
38193 <struct id="@var{id}">
38194 <field name="@var{name}" type="@var{type}"/>
38200 If a register's value is a series of single-bit flags, define it with
38201 a flags type. The @samp{<flags>} element has an explicit @var{size}
38202 and contains one or more @samp{<field>} elements. Each field has a
38203 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38207 <flags id="@var{id}" size="@var{size}">
38208 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38213 @subsection Registers
38216 Each register is represented as an element with this form:
38219 <reg name="@var{name}"
38220 bitsize="@var{size}"
38221 @r{[}regnum="@var{num}"@r{]}
38222 @r{[}save-restore="@var{save-restore}"@r{]}
38223 @r{[}type="@var{type}"@r{]}
38224 @r{[}group="@var{group}"@r{]}/>
38228 The components are as follows:
38233 The register's name; it must be unique within the target description.
38236 The register's size, in bits.
38239 The register's number. If omitted, a register's number is one greater
38240 than that of the previous register (either in the current feature or in
38241 a preceding feature); the first register in the target description
38242 defaults to zero. This register number is used to read or write
38243 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38244 packets, and registers appear in the @code{g} and @code{G} packets
38245 in order of increasing register number.
38248 Whether the register should be preserved across inferior function
38249 calls; this must be either @code{yes} or @code{no}. The default is
38250 @code{yes}, which is appropriate for most registers except for
38251 some system control registers; this is not related to the target's
38255 The type of the register. @var{type} may be a predefined type, a type
38256 defined in the current feature, or one of the special types @code{int}
38257 and @code{float}. @code{int} is an integer type of the correct size
38258 for @var{bitsize}, and @code{float} is a floating point type (in the
38259 architecture's normal floating point format) of the correct size for
38260 @var{bitsize}. The default is @code{int}.
38263 The register group to which this register belongs. @var{group} must
38264 be either @code{general}, @code{float}, or @code{vector}. If no
38265 @var{group} is specified, @value{GDBN} will not display the register
38266 in @code{info registers}.
38270 @node Predefined Target Types
38271 @section Predefined Target Types
38272 @cindex target descriptions, predefined types
38274 Type definitions in the self-description can build up composite types
38275 from basic building blocks, but can not define fundamental types. Instead,
38276 standard identifiers are provided by @value{GDBN} for the fundamental
38277 types. The currently supported types are:
38286 Signed integer types holding the specified number of bits.
38293 Unsigned integer types holding the specified number of bits.
38297 Pointers to unspecified code and data. The program counter and
38298 any dedicated return address register may be marked as code
38299 pointers; printing a code pointer converts it into a symbolic
38300 address. The stack pointer and any dedicated address registers
38301 may be marked as data pointers.
38304 Single precision IEEE floating point.
38307 Double precision IEEE floating point.
38310 The 12-byte extended precision format used by ARM FPA registers.
38313 The 10-byte extended precision format used by x87 registers.
38316 32bit @sc{eflags} register used by x86.
38319 32bit @sc{mxcsr} register used by x86.
38323 @node Standard Target Features
38324 @section Standard Target Features
38325 @cindex target descriptions, standard features
38327 A target description must contain either no registers or all the
38328 target's registers. If the description contains no registers, then
38329 @value{GDBN} will assume a default register layout, selected based on
38330 the architecture. If the description contains any registers, the
38331 default layout will not be used; the standard registers must be
38332 described in the target description, in such a way that @value{GDBN}
38333 can recognize them.
38335 This is accomplished by giving specific names to feature elements
38336 which contain standard registers. @value{GDBN} will look for features
38337 with those names and verify that they contain the expected registers;
38338 if any known feature is missing required registers, or if any required
38339 feature is missing, @value{GDBN} will reject the target
38340 description. You can add additional registers to any of the
38341 standard features --- @value{GDBN} will display them just as if
38342 they were added to an unrecognized feature.
38344 This section lists the known features and their expected contents.
38345 Sample XML documents for these features are included in the
38346 @value{GDBN} source tree, in the directory @file{gdb/features}.
38348 Names recognized by @value{GDBN} should include the name of the
38349 company or organization which selected the name, and the overall
38350 architecture to which the feature applies; so e.g.@: the feature
38351 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38353 The names of registers are not case sensitive for the purpose
38354 of recognizing standard features, but @value{GDBN} will only display
38355 registers using the capitalization used in the description.
38362 * PowerPC Features::
38368 @subsection ARM Features
38369 @cindex target descriptions, ARM features
38371 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38373 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38374 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38376 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38377 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38378 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38381 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38382 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38384 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38385 it should contain at least registers @samp{wR0} through @samp{wR15} and
38386 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38387 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38389 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38390 should contain at least registers @samp{d0} through @samp{d15}. If
38391 they are present, @samp{d16} through @samp{d31} should also be included.
38392 @value{GDBN} will synthesize the single-precision registers from
38393 halves of the double-precision registers.
38395 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38396 need to contain registers; it instructs @value{GDBN} to display the
38397 VFP double-precision registers as vectors and to synthesize the
38398 quad-precision registers from pairs of double-precision registers.
38399 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38400 be present and include 32 double-precision registers.
38402 @node i386 Features
38403 @subsection i386 Features
38404 @cindex target descriptions, i386 features
38406 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38407 targets. It should describe the following registers:
38411 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38413 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38415 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38416 @samp{fs}, @samp{gs}
38418 @samp{st0} through @samp{st7}
38420 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38421 @samp{foseg}, @samp{fooff} and @samp{fop}
38424 The register sets may be different, depending on the target.
38426 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38427 describe registers:
38431 @samp{xmm0} through @samp{xmm7} for i386
38433 @samp{xmm0} through @samp{xmm15} for amd64
38438 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38439 @samp{org.gnu.gdb.i386.sse} feature. It should
38440 describe the upper 128 bits of @sc{ymm} registers:
38444 @samp{ymm0h} through @samp{ymm7h} for i386
38446 @samp{ymm0h} through @samp{ymm15h} for amd64
38449 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38450 describe a single register, @samp{orig_eax}.
38452 @node MIPS Features
38453 @subsection MIPS Features
38454 @cindex target descriptions, MIPS features
38456 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38457 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38458 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38461 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38462 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38463 registers. They may be 32-bit or 64-bit depending on the target.
38465 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38466 it may be optional in a future version of @value{GDBN}. It should
38467 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38468 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38470 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38471 contain a single register, @samp{restart}, which is used by the
38472 Linux kernel to control restartable syscalls.
38474 @node M68K Features
38475 @subsection M68K Features
38476 @cindex target descriptions, M68K features
38479 @item @samp{org.gnu.gdb.m68k.core}
38480 @itemx @samp{org.gnu.gdb.coldfire.core}
38481 @itemx @samp{org.gnu.gdb.fido.core}
38482 One of those features must be always present.
38483 The feature that is present determines which flavor of m68k is
38484 used. The feature that is present should contain registers
38485 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38486 @samp{sp}, @samp{ps} and @samp{pc}.
38488 @item @samp{org.gnu.gdb.coldfire.fp}
38489 This feature is optional. If present, it should contain registers
38490 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38494 @node PowerPC Features
38495 @subsection PowerPC Features
38496 @cindex target descriptions, PowerPC features
38498 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38499 targets. It should contain registers @samp{r0} through @samp{r31},
38500 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38501 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38503 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38504 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38506 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38507 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38510 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38511 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38512 will combine these registers with the floating point registers
38513 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38514 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38515 through @samp{vs63}, the set of vector registers for POWER7.
38517 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38518 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38519 @samp{spefscr}. SPE targets should provide 32-bit registers in
38520 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38521 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38522 these to present registers @samp{ev0} through @samp{ev31} to the
38525 @node TIC6x Features
38526 @subsection TMS320C6x Features
38527 @cindex target descriptions, TIC6x features
38528 @cindex target descriptions, TMS320C6x features
38529 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38530 targets. It should contain registers @samp{A0} through @samp{A15},
38531 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38533 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38534 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38535 through @samp{B31}.
38537 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38538 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38540 @node Operating System Information
38541 @appendix Operating System Information
38542 @cindex operating system information
38548 Users of @value{GDBN} often wish to obtain information about the state of
38549 the operating system running on the target---for example the list of
38550 processes, or the list of open files. This section describes the
38551 mechanism that makes it possible. This mechanism is similar to the
38552 target features mechanism (@pxref{Target Descriptions}), but focuses
38553 on a different aspect of target.
38555 Operating system information is retrived from the target via the
38556 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38557 read}). The object name in the request should be @samp{osdata}, and
38558 the @var{annex} identifies the data to be fetched.
38561 @appendixsection Process list
38562 @cindex operating system information, process list
38564 When requesting the process list, the @var{annex} field in the
38565 @samp{qXfer} request should be @samp{processes}. The returned data is
38566 an XML document. The formal syntax of this document is defined in
38567 @file{gdb/features/osdata.dtd}.
38569 An example document is:
38572 <?xml version="1.0"?>
38573 <!DOCTYPE target SYSTEM "osdata.dtd">
38574 <osdata type="processes">
38576 <column name="pid">1</column>
38577 <column name="user">root</column>
38578 <column name="command">/sbin/init</column>
38579 <column name="cores">1,2,3</column>
38584 Each item should include a column whose name is @samp{pid}. The value
38585 of that column should identify the process on the target. The
38586 @samp{user} and @samp{command} columns are optional, and will be
38587 displayed by @value{GDBN}. The @samp{cores} column, if present,
38588 should contain a comma-separated list of cores that this process
38589 is running on. Target may provide additional columns,
38590 which @value{GDBN} currently ignores.
38592 @node Trace File Format
38593 @appendix Trace File Format
38594 @cindex trace file format
38596 The trace file comes in three parts: a header, a textual description
38597 section, and a trace frame section with binary data.
38599 The header has the form @code{\x7fTRACE0\n}. The first byte is
38600 @code{0x7f} so as to indicate that the file contains binary data,
38601 while the @code{0} is a version number that may have different values
38604 The description section consists of multiple lines of @sc{ascii} text
38605 separated by newline characters (@code{0xa}). The lines may include a
38606 variety of optional descriptive or context-setting information, such
38607 as tracepoint definitions or register set size. @value{GDBN} will
38608 ignore any line that it does not recognize. An empty line marks the end
38611 @c FIXME add some specific types of data
38613 The trace frame section consists of a number of consecutive frames.
38614 Each frame begins with a two-byte tracepoint number, followed by a
38615 four-byte size giving the amount of data in the frame. The data in
38616 the frame consists of a number of blocks, each introduced by a
38617 character indicating its type (at least register, memory, and trace
38618 state variable). The data in this section is raw binary, not a
38619 hexadecimal or other encoding; its endianness matches the target's
38622 @c FIXME bi-arch may require endianness/arch info in description section
38625 @item R @var{bytes}
38626 Register block. The number and ordering of bytes matches that of a
38627 @code{g} packet in the remote protocol. Note that these are the
38628 actual bytes, in target order and @value{GDBN} register order, not a
38629 hexadecimal encoding.
38631 @item M @var{address} @var{length} @var{bytes}...
38632 Memory block. This is a contiguous block of memory, at the 8-byte
38633 address @var{address}, with a 2-byte length @var{length}, followed by
38634 @var{length} bytes.
38636 @item V @var{number} @var{value}
38637 Trace state variable block. This records the 8-byte signed value
38638 @var{value} of trace state variable numbered @var{number}.
38642 Future enhancements of the trace file format may include additional types
38645 @node Index Section Format
38646 @appendix @code{.gdb_index} section format
38647 @cindex .gdb_index section format
38648 @cindex index section format
38650 This section documents the index section that is created by @code{save
38651 gdb-index} (@pxref{Index Files}). The index section is
38652 DWARF-specific; some knowledge of DWARF is assumed in this
38655 The mapped index file format is designed to be directly
38656 @code{mmap}able on any architecture. In most cases, a datum is
38657 represented using a little-endian 32-bit integer value, called an
38658 @code{offset_type}. Big endian machines must byte-swap the values
38659 before using them. Exceptions to this rule are noted. The data is
38660 laid out such that alignment is always respected.
38662 A mapped index consists of several areas, laid out in order.
38666 The file header. This is a sequence of values, of @code{offset_type}
38667 unless otherwise noted:
38671 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38672 Version 4 differs by its hashing function.
38675 The offset, from the start of the file, of the CU list.
38678 The offset, from the start of the file, of the types CU list. Note
38679 that this area can be empty, in which case this offset will be equal
38680 to the next offset.
38683 The offset, from the start of the file, of the address area.
38686 The offset, from the start of the file, of the symbol table.
38689 The offset, from the start of the file, of the constant pool.
38693 The CU list. This is a sequence of pairs of 64-bit little-endian
38694 values, sorted by the CU offset. The first element in each pair is
38695 the offset of a CU in the @code{.debug_info} section. The second
38696 element in each pair is the length of that CU. References to a CU
38697 elsewhere in the map are done using a CU index, which is just the
38698 0-based index into this table. Note that if there are type CUs, then
38699 conceptually CUs and type CUs form a single list for the purposes of
38703 The types CU list. This is a sequence of triplets of 64-bit
38704 little-endian values. In a triplet, the first value is the CU offset,
38705 the second value is the type offset in the CU, and the third value is
38706 the type signature. The types CU list is not sorted.
38709 The address area. The address area consists of a sequence of address
38710 entries. Each address entry has three elements:
38714 The low address. This is a 64-bit little-endian value.
38717 The high address. This is a 64-bit little-endian value. Like
38718 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38721 The CU index. This is an @code{offset_type} value.
38725 The symbol table. This is an open-addressed hash table. The size of
38726 the hash table is always a power of 2.
38728 Each slot in the hash table consists of a pair of @code{offset_type}
38729 values. The first value is the offset of the symbol's name in the
38730 constant pool. The second value is the offset of the CU vector in the
38733 If both values are 0, then this slot in the hash table is empty. This
38734 is ok because while 0 is a valid constant pool index, it cannot be a
38735 valid index for both a string and a CU vector.
38737 The hash value for a table entry is computed by applying an
38738 iterative hash function to the symbol's name. Starting with an
38739 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38740 the string is incorporated into the hash using the formula depending on the
38745 The formula is @code{r = r * 67 + c - 113}.
38748 The formula is @code{r = r * 67 + tolower (c) - 113}.
38751 The terminating @samp{\0} is not incorporated into the hash.
38753 The step size used in the hash table is computed via
38754 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38755 value, and @samp{size} is the size of the hash table. The step size
38756 is used to find the next candidate slot when handling a hash
38759 The names of C@t{++} symbols in the hash table are canonicalized. We
38760 don't currently have a simple description of the canonicalization
38761 algorithm; if you intend to create new index sections, you must read
38765 The constant pool. This is simply a bunch of bytes. It is organized
38766 so that alignment is correct: CU vectors are stored first, followed by
38769 A CU vector in the constant pool is a sequence of @code{offset_type}
38770 values. The first value is the number of CU indices in the vector.
38771 Each subsequent value is the index of a CU in the CU list. This
38772 element in the hash table is used to indicate which CUs define the
38775 A string in the constant pool is zero-terminated.
38780 @node GNU Free Documentation License
38781 @appendix GNU Free Documentation License
38790 % I think something like @colophon should be in texinfo. In the
38792 \long\def\colophon{\hbox to0pt{}\vfill
38793 \centerline{The body of this manual is set in}
38794 \centerline{\fontname\tenrm,}
38795 \centerline{with headings in {\bf\fontname\tenbf}}
38796 \centerline{and examples in {\tt\fontname\tentt}.}
38797 \centerline{{\it\fontname\tenit\/},}
38798 \centerline{{\bf\fontname\tenbf}, and}
38799 \centerline{{\sl\fontname\tensl\/}}
38800 \centerline{are used for emphasis.}\vfill}
38802 % Blame: doc@cygnus.com, 1991.