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,
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 @cindex C@t{++} scope resolution
7333 This use of @samp{::} is very rarely in conflict with the very similar
7334 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7335 scope resolution operator in @value{GDBN} expressions.
7336 @c FIXME: Um, so what happens in one of those rare cases where it's in
7339 @cindex wrong values
7340 @cindex variable values, wrong
7341 @cindex function entry/exit, wrong values of variables
7342 @cindex optimized code, wrong values of variables
7344 @emph{Warning:} Occasionally, a local variable may appear to have the
7345 wrong value at certain points in a function---just after entry to a new
7346 scope, and just before exit.
7348 You may see this problem when you are stepping by machine instructions.
7349 This is because, on most machines, it takes more than one instruction to
7350 set up a stack frame (including local variable definitions); if you are
7351 stepping by machine instructions, variables may appear to have the wrong
7352 values until the stack frame is completely built. On exit, it usually
7353 also takes more than one machine instruction to destroy a stack frame;
7354 after you begin stepping through that group of instructions, local
7355 variable definitions may be gone.
7357 This may also happen when the compiler does significant optimizations.
7358 To be sure of always seeing accurate values, turn off all optimization
7361 @cindex ``No symbol "foo" in current context''
7362 Another possible effect of compiler optimizations is to optimize
7363 unused variables out of existence, or assign variables to registers (as
7364 opposed to memory addresses). Depending on the support for such cases
7365 offered by the debug info format used by the compiler, @value{GDBN}
7366 might not be able to display values for such local variables. If that
7367 happens, @value{GDBN} will print a message like this:
7370 No symbol "foo" in current context.
7373 To solve such problems, either recompile without optimizations, or use a
7374 different debug info format, if the compiler supports several such
7375 formats. @xref{Compilation}, for more information on choosing compiler
7376 options. @xref{C, ,C and C@t{++}}, for more information about debug
7377 info formats that are best suited to C@t{++} programs.
7379 If you ask to print an object whose contents are unknown to
7380 @value{GDBN}, e.g., because its data type is not completely specified
7381 by the debug information, @value{GDBN} will say @samp{<incomplete
7382 type>}. @xref{Symbols, incomplete type}, for more about this.
7384 If you append @kbd{@@entry} string to a function parameter name you get its
7385 value at the time the function got called. If the value is not available an
7386 error message is printed. Entry values are available only with some compilers.
7387 Entry values are normally also printed at the function parameter list according
7388 to @ref{set print entry-values}.
7391 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7397 (gdb) print i@@entry
7401 Strings are identified as arrays of @code{char} values without specified
7402 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7403 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7404 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7405 defines literal string type @code{"char"} as @code{char} without a sign.
7410 signed char var1[] = "A";
7413 You get during debugging
7418 $2 = @{65 'A', 0 '\0'@}
7422 @section Artificial Arrays
7424 @cindex artificial array
7426 @kindex @@@r{, referencing memory as an array}
7427 It is often useful to print out several successive objects of the
7428 same type in memory; a section of an array, or an array of
7429 dynamically determined size for which only a pointer exists in the
7432 You can do this by referring to a contiguous span of memory as an
7433 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7434 operand of @samp{@@} should be the first element of the desired array
7435 and be an individual object. The right operand should be the desired length
7436 of the array. The result is an array value whose elements are all of
7437 the type of the left argument. The first element is actually the left
7438 argument; the second element comes from bytes of memory immediately
7439 following those that hold the first element, and so on. Here is an
7440 example. If a program says
7443 int *array = (int *) malloc (len * sizeof (int));
7447 you can print the contents of @code{array} with
7453 The left operand of @samp{@@} must reside in memory. Array values made
7454 with @samp{@@} in this way behave just like other arrays in terms of
7455 subscripting, and are coerced to pointers when used in expressions.
7456 Artificial arrays most often appear in expressions via the value history
7457 (@pxref{Value History, ,Value History}), after printing one out.
7459 Another way to create an artificial array is to use a cast.
7460 This re-interprets a value as if it were an array.
7461 The value need not be in memory:
7463 (@value{GDBP}) p/x (short[2])0x12345678
7464 $1 = @{0x1234, 0x5678@}
7467 As a convenience, if you leave the array length out (as in
7468 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7469 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7471 (@value{GDBP}) p/x (short[])0x12345678
7472 $2 = @{0x1234, 0x5678@}
7475 Sometimes the artificial array mechanism is not quite enough; in
7476 moderately complex data structures, the elements of interest may not
7477 actually be adjacent---for example, if you are interested in the values
7478 of pointers in an array. One useful work-around in this situation is
7479 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7480 Variables}) as a counter in an expression that prints the first
7481 interesting value, and then repeat that expression via @key{RET}. For
7482 instance, suppose you have an array @code{dtab} of pointers to
7483 structures, and you are interested in the values of a field @code{fv}
7484 in each structure. Here is an example of what you might type:
7494 @node Output Formats
7495 @section Output Formats
7497 @cindex formatted output
7498 @cindex output formats
7499 By default, @value{GDBN} prints a value according to its data type. Sometimes
7500 this is not what you want. For example, you might want to print a number
7501 in hex, or a pointer in decimal. Or you might want to view data in memory
7502 at a certain address as a character string or as an instruction. To do
7503 these things, specify an @dfn{output format} when you print a value.
7505 The simplest use of output formats is to say how to print a value
7506 already computed. This is done by starting the arguments of the
7507 @code{print} command with a slash and a format letter. The format
7508 letters supported are:
7512 Regard the bits of the value as an integer, and print the integer in
7516 Print as integer in signed decimal.
7519 Print as integer in unsigned decimal.
7522 Print as integer in octal.
7525 Print as integer in binary. The letter @samp{t} stands for ``two''.
7526 @footnote{@samp{b} cannot be used because these format letters are also
7527 used with the @code{x} command, where @samp{b} stands for ``byte'';
7528 see @ref{Memory,,Examining Memory}.}
7531 @cindex unknown address, locating
7532 @cindex locate address
7533 Print as an address, both absolute in hexadecimal and as an offset from
7534 the nearest preceding symbol. You can use this format used to discover
7535 where (in what function) an unknown address is located:
7538 (@value{GDBP}) p/a 0x54320
7539 $3 = 0x54320 <_initialize_vx+396>
7543 The command @code{info symbol 0x54320} yields similar results.
7544 @xref{Symbols, info symbol}.
7547 Regard as an integer and print it as a character constant. This
7548 prints both the numerical value and its character representation. The
7549 character representation is replaced with the octal escape @samp{\nnn}
7550 for characters outside the 7-bit @sc{ascii} range.
7552 Without this format, @value{GDBN} displays @code{char},
7553 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7554 constants. Single-byte members of vectors are displayed as integer
7558 Regard the bits of the value as a floating point number and print
7559 using typical floating point syntax.
7562 @cindex printing strings
7563 @cindex printing byte arrays
7564 Regard as a string, if possible. With this format, pointers to single-byte
7565 data are displayed as null-terminated strings and arrays of single-byte data
7566 are displayed as fixed-length strings. Other values are displayed in their
7569 Without this format, @value{GDBN} displays pointers to and arrays of
7570 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7571 strings. Single-byte members of a vector are displayed as an integer
7575 @cindex raw printing
7576 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7577 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7578 Printing}). This typically results in a higher-level display of the
7579 value's contents. The @samp{r} format bypasses any Python
7580 pretty-printer which might exist.
7583 For example, to print the program counter in hex (@pxref{Registers}), type
7590 Note that no space is required before the slash; this is because command
7591 names in @value{GDBN} cannot contain a slash.
7593 To reprint the last value in the value history with a different format,
7594 you can use the @code{print} command with just a format and no
7595 expression. For example, @samp{p/x} reprints the last value in hex.
7598 @section Examining Memory
7600 You can use the command @code{x} (for ``examine'') to examine memory in
7601 any of several formats, independently of your program's data types.
7603 @cindex examining memory
7605 @kindex x @r{(examine memory)}
7606 @item x/@var{nfu} @var{addr}
7609 Use the @code{x} command to examine memory.
7612 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7613 much memory to display and how to format it; @var{addr} is an
7614 expression giving the address where you want to start displaying memory.
7615 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7616 Several commands set convenient defaults for @var{addr}.
7619 @item @var{n}, the repeat count
7620 The repeat count is a decimal integer; the default is 1. It specifies
7621 how much memory (counting by units @var{u}) to display.
7622 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7625 @item @var{f}, the display format
7626 The display format is one of the formats used by @code{print}
7627 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7628 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7629 The default is @samp{x} (hexadecimal) initially. The default changes
7630 each time you use either @code{x} or @code{print}.
7632 @item @var{u}, the unit size
7633 The unit size is any of
7639 Halfwords (two bytes).
7641 Words (four bytes). This is the initial default.
7643 Giant words (eight bytes).
7646 Each time you specify a unit size with @code{x}, that size becomes the
7647 default unit the next time you use @code{x}. For the @samp{i} format,
7648 the unit size is ignored and is normally not written. For the @samp{s} format,
7649 the unit size defaults to @samp{b}, unless it is explicitly given.
7650 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7651 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7652 Note that the results depend on the programming language of the
7653 current compilation unit. If the language is C, the @samp{s}
7654 modifier will use the UTF-16 encoding while @samp{w} will use
7655 UTF-32. The encoding is set by the programming language and cannot
7658 @item @var{addr}, starting display address
7659 @var{addr} is the address where you want @value{GDBN} to begin displaying
7660 memory. The expression need not have a pointer value (though it may);
7661 it is always interpreted as an integer address of a byte of memory.
7662 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7663 @var{addr} is usually just after the last address examined---but several
7664 other commands also set the default address: @code{info breakpoints} (to
7665 the address of the last breakpoint listed), @code{info line} (to the
7666 starting address of a line), and @code{print} (if you use it to display
7667 a value from memory).
7670 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7671 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7672 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7673 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7674 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7676 Since the letters indicating unit sizes are all distinct from the
7677 letters specifying output formats, you do not have to remember whether
7678 unit size or format comes first; either order works. The output
7679 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7680 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7682 Even though the unit size @var{u} is ignored for the formats @samp{s}
7683 and @samp{i}, you might still want to use a count @var{n}; for example,
7684 @samp{3i} specifies that you want to see three machine instructions,
7685 including any operands. For convenience, especially when used with
7686 the @code{display} command, the @samp{i} format also prints branch delay
7687 slot instructions, if any, beyond the count specified, which immediately
7688 follow the last instruction that is within the count. The command
7689 @code{disassemble} gives an alternative way of inspecting machine
7690 instructions; see @ref{Machine Code,,Source and Machine Code}.
7692 All the defaults for the arguments to @code{x} are designed to make it
7693 easy to continue scanning memory with minimal specifications each time
7694 you use @code{x}. For example, after you have inspected three machine
7695 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7696 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7697 the repeat count @var{n} is used again; the other arguments default as
7698 for successive uses of @code{x}.
7700 When examining machine instructions, the instruction at current program
7701 counter is shown with a @code{=>} marker. For example:
7704 (@value{GDBP}) x/5i $pc-6
7705 0x804837f <main+11>: mov %esp,%ebp
7706 0x8048381 <main+13>: push %ecx
7707 0x8048382 <main+14>: sub $0x4,%esp
7708 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7709 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7712 @cindex @code{$_}, @code{$__}, and value history
7713 The addresses and contents printed by the @code{x} command are not saved
7714 in the value history because there is often too much of them and they
7715 would get in the way. Instead, @value{GDBN} makes these values available for
7716 subsequent use in expressions as values of the convenience variables
7717 @code{$_} and @code{$__}. After an @code{x} command, the last address
7718 examined is available for use in expressions in the convenience variable
7719 @code{$_}. The contents of that address, as examined, are available in
7720 the convenience variable @code{$__}.
7722 If the @code{x} command has a repeat count, the address and contents saved
7723 are from the last memory unit printed; this is not the same as the last
7724 address printed if several units were printed on the last line of output.
7726 @cindex remote memory comparison
7727 @cindex verify remote memory image
7728 When you are debugging a program running on a remote target machine
7729 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7730 remote machine's memory against the executable file you downloaded to
7731 the target. The @code{compare-sections} command is provided for such
7735 @kindex compare-sections
7736 @item compare-sections @r{[}@var{section-name}@r{]}
7737 Compare the data of a loadable section @var{section-name} in the
7738 executable file of the program being debugged with the same section in
7739 the remote machine's memory, and report any mismatches. With no
7740 arguments, compares all loadable sections. This command's
7741 availability depends on the target's support for the @code{"qCRC"}
7746 @section Automatic Display
7747 @cindex automatic display
7748 @cindex display of expressions
7750 If you find that you want to print the value of an expression frequently
7751 (to see how it changes), you might want to add it to the @dfn{automatic
7752 display list} so that @value{GDBN} prints its value each time your program stops.
7753 Each expression added to the list is given a number to identify it;
7754 to remove an expression from the list, you specify that number.
7755 The automatic display looks like this:
7759 3: bar[5] = (struct hack *) 0x3804
7763 This display shows item numbers, expressions and their current values. As with
7764 displays you request manually using @code{x} or @code{print}, you can
7765 specify the output format you prefer; in fact, @code{display} decides
7766 whether to use @code{print} or @code{x} depending your format
7767 specification---it uses @code{x} if you specify either the @samp{i}
7768 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7772 @item display @var{expr}
7773 Add the expression @var{expr} to the list of expressions to display
7774 each time your program stops. @xref{Expressions, ,Expressions}.
7776 @code{display} does not repeat if you press @key{RET} again after using it.
7778 @item display/@var{fmt} @var{expr}
7779 For @var{fmt} specifying only a display format and not a size or
7780 count, add the expression @var{expr} to the auto-display list but
7781 arrange to display it each time in the specified format @var{fmt}.
7782 @xref{Output Formats,,Output Formats}.
7784 @item display/@var{fmt} @var{addr}
7785 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7786 number of units, add the expression @var{addr} as a memory address to
7787 be examined each time your program stops. Examining means in effect
7788 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7791 For example, @samp{display/i $pc} can be helpful, to see the machine
7792 instruction about to be executed each time execution stops (@samp{$pc}
7793 is a common name for the program counter; @pxref{Registers, ,Registers}).
7796 @kindex delete display
7798 @item undisplay @var{dnums}@dots{}
7799 @itemx delete display @var{dnums}@dots{}
7800 Remove items from the list of expressions to display. Specify the
7801 numbers of the displays that you want affected with the command
7802 argument @var{dnums}. It can be a single display number, one of the
7803 numbers shown in the first field of the @samp{info display} display;
7804 or it could be a range of display numbers, as in @code{2-4}.
7806 @code{undisplay} does not repeat if you press @key{RET} after using it.
7807 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7809 @kindex disable display
7810 @item disable display @var{dnums}@dots{}
7811 Disable the display of item numbers @var{dnums}. A disabled display
7812 item is not printed automatically, but is not forgotten. It may be
7813 enabled again later. Specify the numbers of the displays that you
7814 want affected with the command argument @var{dnums}. It can be a
7815 single display number, one of the numbers shown in the first field of
7816 the @samp{info display} display; or it could be a range of display
7817 numbers, as in @code{2-4}.
7819 @kindex enable display
7820 @item enable display @var{dnums}@dots{}
7821 Enable display of item numbers @var{dnums}. It becomes effective once
7822 again in auto display of its expression, until you specify otherwise.
7823 Specify the numbers of the displays that you want affected with the
7824 command argument @var{dnums}. It can be a single display number, one
7825 of the numbers shown in the first field of the @samp{info display}
7826 display; or it could be a range of display numbers, as in @code{2-4}.
7829 Display the current values of the expressions on the list, just as is
7830 done when your program stops.
7832 @kindex info display
7834 Print the list of expressions previously set up to display
7835 automatically, each one with its item number, but without showing the
7836 values. This includes disabled expressions, which are marked as such.
7837 It also includes expressions which would not be displayed right now
7838 because they refer to automatic variables not currently available.
7841 @cindex display disabled out of scope
7842 If a display expression refers to local variables, then it does not make
7843 sense outside the lexical context for which it was set up. Such an
7844 expression is disabled when execution enters a context where one of its
7845 variables is not defined. For example, if you give the command
7846 @code{display last_char} while inside a function with an argument
7847 @code{last_char}, @value{GDBN} displays this argument while your program
7848 continues to stop inside that function. When it stops elsewhere---where
7849 there is no variable @code{last_char}---the display is disabled
7850 automatically. The next time your program stops where @code{last_char}
7851 is meaningful, you can enable the display expression once again.
7853 @node Print Settings
7854 @section Print Settings
7856 @cindex format options
7857 @cindex print settings
7858 @value{GDBN} provides the following ways to control how arrays, structures,
7859 and symbols are printed.
7862 These settings are useful for debugging programs in any language:
7866 @item set print address
7867 @itemx set print address on
7868 @cindex print/don't print memory addresses
7869 @value{GDBN} prints memory addresses showing the location of stack
7870 traces, structure values, pointer values, breakpoints, and so forth,
7871 even when it also displays the contents of those addresses. The default
7872 is @code{on}. For example, this is what a stack frame display looks like with
7873 @code{set print address on}:
7878 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7880 530 if (lquote != def_lquote)
7884 @item set print address off
7885 Do not print addresses when displaying their contents. For example,
7886 this is the same stack frame displayed with @code{set print address off}:
7890 (@value{GDBP}) set print addr off
7892 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7893 530 if (lquote != def_lquote)
7897 You can use @samp{set print address off} to eliminate all machine
7898 dependent displays from the @value{GDBN} interface. For example, with
7899 @code{print address off}, you should get the same text for backtraces on
7900 all machines---whether or not they involve pointer arguments.
7903 @item show print address
7904 Show whether or not addresses are to be printed.
7907 When @value{GDBN} prints a symbolic address, it normally prints the
7908 closest earlier symbol plus an offset. If that symbol does not uniquely
7909 identify the address (for example, it is a name whose scope is a single
7910 source file), you may need to clarify. One way to do this is with
7911 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7912 you can set @value{GDBN} to print the source file and line number when
7913 it prints a symbolic address:
7916 @item set print symbol-filename on
7917 @cindex source file and line of a symbol
7918 @cindex symbol, source file and line
7919 Tell @value{GDBN} to print the source file name and line number of a
7920 symbol in the symbolic form of an address.
7922 @item set print symbol-filename off
7923 Do not print source file name and line number of a symbol. This is the
7926 @item show print symbol-filename
7927 Show whether or not @value{GDBN} will print the source file name and
7928 line number of a symbol in the symbolic form of an address.
7931 Another situation where it is helpful to show symbol filenames and line
7932 numbers is when disassembling code; @value{GDBN} shows you the line
7933 number and source file that corresponds to each instruction.
7935 Also, you may wish to see the symbolic form only if the address being
7936 printed is reasonably close to the closest earlier symbol:
7939 @item set print max-symbolic-offset @var{max-offset}
7940 @cindex maximum value for offset of closest symbol
7941 Tell @value{GDBN} to only display the symbolic form of an address if the
7942 offset between the closest earlier symbol and the address is less than
7943 @var{max-offset}. The default is 0, which tells @value{GDBN}
7944 to always print the symbolic form of an address if any symbol precedes it.
7946 @item show print max-symbolic-offset
7947 Ask how large the maximum offset is that @value{GDBN} prints in a
7951 @cindex wild pointer, interpreting
7952 @cindex pointer, finding referent
7953 If you have a pointer and you are not sure where it points, try
7954 @samp{set print symbol-filename on}. Then you can determine the name
7955 and source file location of the variable where it points, using
7956 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7957 For example, here @value{GDBN} shows that a variable @code{ptt} points
7958 at another variable @code{t}, defined in @file{hi2.c}:
7961 (@value{GDBP}) set print symbol-filename on
7962 (@value{GDBP}) p/a ptt
7963 $4 = 0xe008 <t in hi2.c>
7967 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7968 does not show the symbol name and filename of the referent, even with
7969 the appropriate @code{set print} options turned on.
7972 Other settings control how different kinds of objects are printed:
7975 @item set print array
7976 @itemx set print array on
7977 @cindex pretty print arrays
7978 Pretty print arrays. This format is more convenient to read,
7979 but uses more space. The default is off.
7981 @item set print array off
7982 Return to compressed format for arrays.
7984 @item show print array
7985 Show whether compressed or pretty format is selected for displaying
7988 @cindex print array indexes
7989 @item set print array-indexes
7990 @itemx set print array-indexes on
7991 Print the index of each element when displaying arrays. May be more
7992 convenient to locate a given element in the array or quickly find the
7993 index of a given element in that printed array. The default is off.
7995 @item set print array-indexes off
7996 Stop printing element indexes when displaying arrays.
7998 @item show print array-indexes
7999 Show whether the index of each element is printed when displaying
8002 @item set print elements @var{number-of-elements}
8003 @cindex number of array elements to print
8004 @cindex limit on number of printed array elements
8005 Set a limit on how many elements of an array @value{GDBN} will print.
8006 If @value{GDBN} is printing a large array, it stops printing after it has
8007 printed the number of elements set by the @code{set print elements} command.
8008 This limit also applies to the display of strings.
8009 When @value{GDBN} starts, this limit is set to 200.
8010 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8012 @item show print elements
8013 Display the number of elements of a large array that @value{GDBN} will print.
8014 If the number is 0, then the printing is unlimited.
8016 @item set print frame-arguments @var{value}
8017 @kindex set print frame-arguments
8018 @cindex printing frame argument values
8019 @cindex print all frame argument values
8020 @cindex print frame argument values for scalars only
8021 @cindex do not print frame argument values
8022 This command allows to control how the values of arguments are printed
8023 when the debugger prints a frame (@pxref{Frames}). The possible
8028 The values of all arguments are printed.
8031 Print the value of an argument only if it is a scalar. The value of more
8032 complex arguments such as arrays, structures, unions, etc, is replaced
8033 by @code{@dots{}}. This is the default. Here is an example where
8034 only scalar arguments are shown:
8037 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8042 None of the argument values are printed. Instead, the value of each argument
8043 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8046 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8051 By default, only scalar arguments are printed. This command can be used
8052 to configure the debugger to print the value of all arguments, regardless
8053 of their type. However, it is often advantageous to not print the value
8054 of more complex parameters. For instance, it reduces the amount of
8055 information printed in each frame, making the backtrace more readable.
8056 Also, it improves performance when displaying Ada frames, because
8057 the computation of large arguments can sometimes be CPU-intensive,
8058 especially in large applications. Setting @code{print frame-arguments}
8059 to @code{scalars} (the default) or @code{none} avoids this computation,
8060 thus speeding up the display of each Ada frame.
8062 @item show print frame-arguments
8063 Show how the value of arguments should be displayed when printing a frame.
8065 @anchor{set print entry-values}
8066 @item set print entry-values @var{value}
8067 @kindex set print entry-values
8068 Set printing of frame argument values at function entry. In some cases
8069 @value{GDBN} can determine the value of function argument which was passed by
8070 the function caller, even if the value was modified inside the called function
8071 and therefore is different. With optimized code, the current value could be
8072 unavailable, but the entry value may still be known.
8074 The default value is @code{default} (see below for its description). Older
8075 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8076 this feature will behave in the @code{default} setting the same way as with the
8079 This functionality is currently supported only by DWARF 2 debugging format and
8080 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8081 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8084 The @var{value} parameter can be one of the following:
8088 Print only actual parameter values, never print values from function entry
8092 #0 different (val=6)
8093 #0 lost (val=<optimized out>)
8095 #0 invalid (val=<optimized out>)
8099 Print only parameter values from function entry point. The actual parameter
8100 values are never printed.
8102 #0 equal (val@@entry=5)
8103 #0 different (val@@entry=5)
8104 #0 lost (val@@entry=5)
8105 #0 born (val@@entry=<optimized out>)
8106 #0 invalid (val@@entry=<optimized out>)
8110 Print only parameter values from function entry point. If value from function
8111 entry point is not known while the actual value is known, print the actual
8112 value for such parameter.
8114 #0 equal (val@@entry=5)
8115 #0 different (val@@entry=5)
8116 #0 lost (val@@entry=5)
8118 #0 invalid (val@@entry=<optimized out>)
8122 Print actual parameter values. If actual parameter value is not known while
8123 value from function entry point is known, print the entry point value for such
8127 #0 different (val=6)
8128 #0 lost (val@@entry=5)
8130 #0 invalid (val=<optimized out>)
8134 Always print both the actual parameter value and its value from function entry
8135 point, even if values of one or both are not available due to compiler
8138 #0 equal (val=5, val@@entry=5)
8139 #0 different (val=6, val@@entry=5)
8140 #0 lost (val=<optimized out>, val@@entry=5)
8141 #0 born (val=10, val@@entry=<optimized out>)
8142 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8146 Print the actual parameter value if it is known and also its value from
8147 function entry point if it is known. If neither is known, print for the actual
8148 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8149 values are known and identical, print the shortened
8150 @code{param=param@@entry=VALUE} notation.
8152 #0 equal (val=val@@entry=5)
8153 #0 different (val=6, val@@entry=5)
8154 #0 lost (val@@entry=5)
8156 #0 invalid (val=<optimized out>)
8160 Always print the actual parameter value. Print also its value from function
8161 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8162 if both values are known and identical, print the shortened
8163 @code{param=param@@entry=VALUE} notation.
8165 #0 equal (val=val@@entry=5)
8166 #0 different (val=6, val@@entry=5)
8167 #0 lost (val=<optimized out>, val@@entry=5)
8169 #0 invalid (val=<optimized out>)
8173 For analysis messages on possible failures of frame argument values at function
8174 entry resolution see @ref{set debug entry-values}.
8176 @item show print entry-values
8177 Show the method being used for printing of frame argument values at function
8180 @item set print repeats
8181 @cindex repeated array elements
8182 Set the threshold for suppressing display of repeated array
8183 elements. When the number of consecutive identical elements of an
8184 array exceeds the threshold, @value{GDBN} prints the string
8185 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8186 identical repetitions, instead of displaying the identical elements
8187 themselves. Setting the threshold to zero will cause all elements to
8188 be individually printed. The default threshold is 10.
8190 @item show print repeats
8191 Display the current threshold for printing repeated identical
8194 @item set print null-stop
8195 @cindex @sc{null} elements in arrays
8196 Cause @value{GDBN} to stop printing the characters of an array when the first
8197 @sc{null} is encountered. This is useful when large arrays actually
8198 contain only short strings.
8201 @item show print null-stop
8202 Show whether @value{GDBN} stops printing an array on the first
8203 @sc{null} character.
8205 @item set print pretty on
8206 @cindex print structures in indented form
8207 @cindex indentation in structure display
8208 Cause @value{GDBN} to print structures in an indented format with one member
8209 per line, like this:
8224 @item set print pretty off
8225 Cause @value{GDBN} to print structures in a compact format, like this:
8229 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8230 meat = 0x54 "Pork"@}
8235 This is the default format.
8237 @item show print pretty
8238 Show which format @value{GDBN} is using to print structures.
8240 @item set print sevenbit-strings on
8241 @cindex eight-bit characters in strings
8242 @cindex octal escapes in strings
8243 Print using only seven-bit characters; if this option is set,
8244 @value{GDBN} displays any eight-bit characters (in strings or
8245 character values) using the notation @code{\}@var{nnn}. This setting is
8246 best if you are working in English (@sc{ascii}) and you use the
8247 high-order bit of characters as a marker or ``meta'' bit.
8249 @item set print sevenbit-strings off
8250 Print full eight-bit characters. This allows the use of more
8251 international character sets, and is the default.
8253 @item show print sevenbit-strings
8254 Show whether or not @value{GDBN} is printing only seven-bit characters.
8256 @item set print union on
8257 @cindex unions in structures, printing
8258 Tell @value{GDBN} to print unions which are contained in structures
8259 and other unions. This is the default setting.
8261 @item set print union off
8262 Tell @value{GDBN} not to print unions which are contained in
8263 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8266 @item show print union
8267 Ask @value{GDBN} whether or not it will print unions which are contained in
8268 structures and other unions.
8270 For example, given the declarations
8273 typedef enum @{Tree, Bug@} Species;
8274 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8275 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8286 struct thing foo = @{Tree, @{Acorn@}@};
8290 with @code{set print union on} in effect @samp{p foo} would print
8293 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8297 and with @code{set print union off} in effect it would print
8300 $1 = @{it = Tree, form = @{...@}@}
8304 @code{set print union} affects programs written in C-like languages
8310 These settings are of interest when debugging C@t{++} programs:
8313 @cindex demangling C@t{++} names
8314 @item set print demangle
8315 @itemx set print demangle on
8316 Print C@t{++} names in their source form rather than in the encoded
8317 (``mangled'') form passed to the assembler and linker for type-safe
8318 linkage. The default is on.
8320 @item show print demangle
8321 Show whether C@t{++} names are printed in mangled or demangled form.
8323 @item set print asm-demangle
8324 @itemx set print asm-demangle on
8325 Print C@t{++} names in their source form rather than their mangled form, even
8326 in assembler code printouts such as instruction disassemblies.
8329 @item show print asm-demangle
8330 Show whether C@t{++} names in assembly listings are printed in mangled
8333 @cindex C@t{++} symbol decoding style
8334 @cindex symbol decoding style, C@t{++}
8335 @kindex set demangle-style
8336 @item set demangle-style @var{style}
8337 Choose among several encoding schemes used by different compilers to
8338 represent C@t{++} names. The choices for @var{style} are currently:
8342 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8345 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8346 This is the default.
8349 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8352 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8355 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8356 @strong{Warning:} this setting alone is not sufficient to allow
8357 debugging @code{cfront}-generated executables. @value{GDBN} would
8358 require further enhancement to permit that.
8361 If you omit @var{style}, you will see a list of possible formats.
8363 @item show demangle-style
8364 Display the encoding style currently in use for decoding C@t{++} symbols.
8366 @item set print object
8367 @itemx set print object on
8368 @cindex derived type of an object, printing
8369 @cindex display derived types
8370 When displaying a pointer to an object, identify the @emph{actual}
8371 (derived) type of the object rather than the @emph{declared} type, using
8372 the virtual function table. Note that the virtual function table is
8373 required---this feature can only work for objects that have run-time
8374 type identification; a single virtual method in the object's declared
8377 @item set print object off
8378 Display only the declared type of objects, without reference to the
8379 virtual function table. This is the default setting.
8381 @item show print object
8382 Show whether actual, or declared, object types are displayed.
8384 @item set print static-members
8385 @itemx set print static-members on
8386 @cindex static members of C@t{++} objects
8387 Print static members when displaying a C@t{++} object. The default is on.
8389 @item set print static-members off
8390 Do not print static members when displaying a C@t{++} object.
8392 @item show print static-members
8393 Show whether C@t{++} static members are printed or not.
8395 @item set print pascal_static-members
8396 @itemx set print pascal_static-members on
8397 @cindex static members of Pascal objects
8398 @cindex Pascal objects, static members display
8399 Print static members when displaying a Pascal object. The default is on.
8401 @item set print pascal_static-members off
8402 Do not print static members when displaying a Pascal object.
8404 @item show print pascal_static-members
8405 Show whether Pascal static members are printed or not.
8407 @c These don't work with HP ANSI C++ yet.
8408 @item set print vtbl
8409 @itemx set print vtbl on
8410 @cindex pretty print C@t{++} virtual function tables
8411 @cindex virtual functions (C@t{++}) display
8412 @cindex VTBL display
8413 Pretty print C@t{++} virtual function tables. The default is off.
8414 (The @code{vtbl} commands do not work on programs compiled with the HP
8415 ANSI C@t{++} compiler (@code{aCC}).)
8417 @item set print vtbl off
8418 Do not pretty print C@t{++} virtual function tables.
8420 @item show print vtbl
8421 Show whether C@t{++} virtual function tables are pretty printed, or not.
8424 @node Pretty Printing
8425 @section Pretty Printing
8427 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8428 Python code. It greatly simplifies the display of complex objects. This
8429 mechanism works for both MI and the CLI.
8432 * Pretty-Printer Introduction:: Introduction to pretty-printers
8433 * Pretty-Printer Example:: An example pretty-printer
8434 * Pretty-Printer Commands:: Pretty-printer commands
8437 @node Pretty-Printer Introduction
8438 @subsection Pretty-Printer Introduction
8440 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8441 registered for the value. If there is then @value{GDBN} invokes the
8442 pretty-printer to print the value. Otherwise the value is printed normally.
8444 Pretty-printers are normally named. This makes them easy to manage.
8445 The @samp{info pretty-printer} command will list all the installed
8446 pretty-printers with their names.
8447 If a pretty-printer can handle multiple data types, then its
8448 @dfn{subprinters} are the printers for the individual data types.
8449 Each such subprinter has its own name.
8450 The format of the name is @var{printer-name};@var{subprinter-name}.
8452 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8453 Typically they are automatically loaded and registered when the corresponding
8454 debug information is loaded, thus making them available without having to
8455 do anything special.
8457 There are three places where a pretty-printer can be registered.
8461 Pretty-printers registered globally are available when debugging
8465 Pretty-printers registered with a program space are available only
8466 when debugging that program.
8467 @xref{Progspaces In Python}, for more details on program spaces in Python.
8470 Pretty-printers registered with an objfile are loaded and unloaded
8471 with the corresponding objfile (e.g., shared library).
8472 @xref{Objfiles In Python}, for more details on objfiles in Python.
8475 @xref{Selecting Pretty-Printers}, for further information on how
8476 pretty-printers are selected,
8478 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8481 @node Pretty-Printer Example
8482 @subsection Pretty-Printer Example
8484 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8487 (@value{GDBP}) print s
8489 static npos = 4294967295,
8491 <std::allocator<char>> = @{
8492 <__gnu_cxx::new_allocator<char>> = @{
8493 <No data fields>@}, <No data fields>
8495 members of std::basic_string<char, std::char_traits<char>,
8496 std::allocator<char> >::_Alloc_hider:
8497 _M_p = 0x804a014 "abcd"
8502 With a pretty-printer for @code{std::string} only the contents are printed:
8505 (@value{GDBP}) print s
8509 @node Pretty-Printer Commands
8510 @subsection Pretty-Printer Commands
8511 @cindex pretty-printer commands
8514 @kindex info pretty-printer
8515 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8516 Print the list of installed pretty-printers.
8517 This includes disabled pretty-printers, which are marked as such.
8519 @var{object-regexp} is a regular expression matching the objects
8520 whose pretty-printers to list.
8521 Objects can be @code{global}, the program space's file
8522 (@pxref{Progspaces In Python}),
8523 and the object files within that program space (@pxref{Objfiles In Python}).
8524 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8525 looks up a printer from these three objects.
8527 @var{name-regexp} is a regular expression matching the name of the printers
8530 @kindex disable pretty-printer
8531 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8532 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8533 A disabled pretty-printer is not forgotten, it may be enabled again later.
8535 @kindex enable pretty-printer
8536 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8537 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8542 Suppose we have three pretty-printers installed: one from library1.so
8543 named @code{foo} that prints objects of type @code{foo}, and
8544 another from library2.so named @code{bar} that prints two types of objects,
8545 @code{bar1} and @code{bar2}.
8548 (gdb) info pretty-printer
8555 (gdb) info pretty-printer library2
8560 (gdb) disable pretty-printer library1
8562 2 of 3 printers enabled
8563 (gdb) info pretty-printer
8570 (gdb) disable pretty-printer library2 bar:bar1
8572 1 of 3 printers enabled
8573 (gdb) info pretty-printer library2
8580 (gdb) disable pretty-printer library2 bar
8582 0 of 3 printers enabled
8583 (gdb) info pretty-printer library2
8592 Note that for @code{bar} the entire printer can be disabled,
8593 as can each individual subprinter.
8596 @section Value History
8598 @cindex value history
8599 @cindex history of values printed by @value{GDBN}
8600 Values printed by the @code{print} command are saved in the @value{GDBN}
8601 @dfn{value history}. This allows you to refer to them in other expressions.
8602 Values are kept until the symbol table is re-read or discarded
8603 (for example with the @code{file} or @code{symbol-file} commands).
8604 When the symbol table changes, the value history is discarded,
8605 since the values may contain pointers back to the types defined in the
8610 @cindex history number
8611 The values printed are given @dfn{history numbers} by which you can
8612 refer to them. These are successive integers starting with one.
8613 @code{print} shows you the history number assigned to a value by
8614 printing @samp{$@var{num} = } before the value; here @var{num} is the
8617 To refer to any previous value, use @samp{$} followed by the value's
8618 history number. The way @code{print} labels its output is designed to
8619 remind you of this. Just @code{$} refers to the most recent value in
8620 the history, and @code{$$} refers to the value before that.
8621 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8622 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8623 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8625 For example, suppose you have just printed a pointer to a structure and
8626 want to see the contents of the structure. It suffices to type
8632 If you have a chain of structures where the component @code{next} points
8633 to the next one, you can print the contents of the next one with this:
8640 You can print successive links in the chain by repeating this
8641 command---which you can do by just typing @key{RET}.
8643 Note that the history records values, not expressions. If the value of
8644 @code{x} is 4 and you type these commands:
8652 then the value recorded in the value history by the @code{print} command
8653 remains 4 even though the value of @code{x} has changed.
8658 Print the last ten values in the value history, with their item numbers.
8659 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8660 values} does not change the history.
8662 @item show values @var{n}
8663 Print ten history values centered on history item number @var{n}.
8666 Print ten history values just after the values last printed. If no more
8667 values are available, @code{show values +} produces no display.
8670 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8671 same effect as @samp{show values +}.
8673 @node Convenience Vars
8674 @section Convenience Variables
8676 @cindex convenience variables
8677 @cindex user-defined variables
8678 @value{GDBN} provides @dfn{convenience variables} that you can use within
8679 @value{GDBN} to hold on to a value and refer to it later. These variables
8680 exist entirely within @value{GDBN}; they are not part of your program, and
8681 setting a convenience variable has no direct effect on further execution
8682 of your program. That is why you can use them freely.
8684 Convenience variables are prefixed with @samp{$}. Any name preceded by
8685 @samp{$} can be used for a convenience variable, unless it is one of
8686 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8687 (Value history references, in contrast, are @emph{numbers} preceded
8688 by @samp{$}. @xref{Value History, ,Value History}.)
8690 You can save a value in a convenience variable with an assignment
8691 expression, just as you would set a variable in your program.
8695 set $foo = *object_ptr
8699 would save in @code{$foo} the value contained in the object pointed to by
8702 Using a convenience variable for the first time creates it, but its
8703 value is @code{void} until you assign a new value. You can alter the
8704 value with another assignment at any time.
8706 Convenience variables have no fixed types. You can assign a convenience
8707 variable any type of value, including structures and arrays, even if
8708 that variable already has a value of a different type. The convenience
8709 variable, when used as an expression, has the type of its current value.
8712 @kindex show convenience
8713 @cindex show all user variables
8714 @item show convenience
8715 Print a list of convenience variables used so far, and their values.
8716 Abbreviated @code{show conv}.
8718 @kindex init-if-undefined
8719 @cindex convenience variables, initializing
8720 @item init-if-undefined $@var{variable} = @var{expression}
8721 Set a convenience variable if it has not already been set. This is useful
8722 for user-defined commands that keep some state. It is similar, in concept,
8723 to using local static variables with initializers in C (except that
8724 convenience variables are global). It can also be used to allow users to
8725 override default values used in a command script.
8727 If the variable is already defined then the expression is not evaluated so
8728 any side-effects do not occur.
8731 One of the ways to use a convenience variable is as a counter to be
8732 incremented or a pointer to be advanced. For example, to print
8733 a field from successive elements of an array of structures:
8737 print bar[$i++]->contents
8741 Repeat that command by typing @key{RET}.
8743 Some convenience variables are created automatically by @value{GDBN} and given
8744 values likely to be useful.
8747 @vindex $_@r{, convenience variable}
8749 The variable @code{$_} is automatically set by the @code{x} command to
8750 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8751 commands which provide a default address for @code{x} to examine also
8752 set @code{$_} to that address; these commands include @code{info line}
8753 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8754 except when set by the @code{x} command, in which case it is a pointer
8755 to the type of @code{$__}.
8757 @vindex $__@r{, convenience variable}
8759 The variable @code{$__} is automatically set by the @code{x} command
8760 to the value found in the last address examined. Its type is chosen
8761 to match the format in which the data was printed.
8764 @vindex $_exitcode@r{, convenience variable}
8765 The variable @code{$_exitcode} is automatically set to the exit code when
8766 the program being debugged terminates.
8769 @vindex $_sdata@r{, inspect, convenience variable}
8770 The variable @code{$_sdata} contains extra collected static tracepoint
8771 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8772 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8773 if extra static tracepoint data has not been collected.
8776 @vindex $_siginfo@r{, convenience variable}
8777 The variable @code{$_siginfo} contains extra signal information
8778 (@pxref{extra signal information}). Note that @code{$_siginfo}
8779 could be empty, if the application has not yet received any signals.
8780 For example, it will be empty before you execute the @code{run} command.
8783 @vindex $_tlb@r{, convenience variable}
8784 The variable @code{$_tlb} is automatically set when debugging
8785 applications running on MS-Windows in native mode or connected to
8786 gdbserver that supports the @code{qGetTIBAddr} request.
8787 @xref{General Query Packets}.
8788 This variable contains the address of the thread information block.
8792 On HP-UX systems, if you refer to a function or variable name that
8793 begins with a dollar sign, @value{GDBN} searches for a user or system
8794 name first, before it searches for a convenience variable.
8796 @cindex convenience functions
8797 @value{GDBN} also supplies some @dfn{convenience functions}. These
8798 have a syntax similar to convenience variables. A convenience
8799 function can be used in an expression just like an ordinary function;
8800 however, a convenience function is implemented internally to
8805 @kindex help function
8806 @cindex show all convenience functions
8807 Print a list of all convenience functions.
8814 You can refer to machine register contents, in expressions, as variables
8815 with names starting with @samp{$}. The names of registers are different
8816 for each machine; use @code{info registers} to see the names used on
8820 @kindex info registers
8821 @item info registers
8822 Print the names and values of all registers except floating-point
8823 and vector registers (in the selected stack frame).
8825 @kindex info all-registers
8826 @cindex floating point registers
8827 @item info all-registers
8828 Print the names and values of all registers, including floating-point
8829 and vector registers (in the selected stack frame).
8831 @item info registers @var{regname} @dots{}
8832 Print the @dfn{relativized} value of each specified register @var{regname}.
8833 As discussed in detail below, register values are normally relative to
8834 the selected stack frame. @var{regname} may be any register name valid on
8835 the machine you are using, with or without the initial @samp{$}.
8838 @cindex stack pointer register
8839 @cindex program counter register
8840 @cindex process status register
8841 @cindex frame pointer register
8842 @cindex standard registers
8843 @value{GDBN} has four ``standard'' register names that are available (in
8844 expressions) on most machines---whenever they do not conflict with an
8845 architecture's canonical mnemonics for registers. The register names
8846 @code{$pc} and @code{$sp} are used for the program counter register and
8847 the stack pointer. @code{$fp} is used for a register that contains a
8848 pointer to the current stack frame, and @code{$ps} is used for a
8849 register that contains the processor status. For example,
8850 you could print the program counter in hex with
8857 or print the instruction to be executed next with
8864 or add four to the stack pointer@footnote{This is a way of removing
8865 one word from the stack, on machines where stacks grow downward in
8866 memory (most machines, nowadays). This assumes that the innermost
8867 stack frame is selected; setting @code{$sp} is not allowed when other
8868 stack frames are selected. To pop entire frames off the stack,
8869 regardless of machine architecture, use @code{return};
8870 see @ref{Returning, ,Returning from a Function}.} with
8876 Whenever possible, these four standard register names are available on
8877 your machine even though the machine has different canonical mnemonics,
8878 so long as there is no conflict. The @code{info registers} command
8879 shows the canonical names. For example, on the SPARC, @code{info
8880 registers} displays the processor status register as @code{$psr} but you
8881 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8882 is an alias for the @sc{eflags} register.
8884 @value{GDBN} always considers the contents of an ordinary register as an
8885 integer when the register is examined in this way. Some machines have
8886 special registers which can hold nothing but floating point; these
8887 registers are considered to have floating point values. There is no way
8888 to refer to the contents of an ordinary register as floating point value
8889 (although you can @emph{print} it as a floating point value with
8890 @samp{print/f $@var{regname}}).
8892 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8893 means that the data format in which the register contents are saved by
8894 the operating system is not the same one that your program normally
8895 sees. For example, the registers of the 68881 floating point
8896 coprocessor are always saved in ``extended'' (raw) format, but all C
8897 programs expect to work with ``double'' (virtual) format. In such
8898 cases, @value{GDBN} normally works with the virtual format only (the format
8899 that makes sense for your program), but the @code{info registers} command
8900 prints the data in both formats.
8902 @cindex SSE registers (x86)
8903 @cindex MMX registers (x86)
8904 Some machines have special registers whose contents can be interpreted
8905 in several different ways. For example, modern x86-based machines
8906 have SSE and MMX registers that can hold several values packed
8907 together in several different formats. @value{GDBN} refers to such
8908 registers in @code{struct} notation:
8911 (@value{GDBP}) print $xmm1
8913 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8914 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8915 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8916 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8917 v4_int32 = @{0, 20657912, 11, 13@},
8918 v2_int64 = @{88725056443645952, 55834574859@},
8919 uint128 = 0x0000000d0000000b013b36f800000000
8924 To set values of such registers, you need to tell @value{GDBN} which
8925 view of the register you wish to change, as if you were assigning
8926 value to a @code{struct} member:
8929 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8932 Normally, register values are relative to the selected stack frame
8933 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8934 value that the register would contain if all stack frames farther in
8935 were exited and their saved registers restored. In order to see the
8936 true contents of hardware registers, you must select the innermost
8937 frame (with @samp{frame 0}).
8939 However, @value{GDBN} must deduce where registers are saved, from the machine
8940 code generated by your compiler. If some registers are not saved, or if
8941 @value{GDBN} is unable to locate the saved registers, the selected stack
8942 frame makes no difference.
8944 @node Floating Point Hardware
8945 @section Floating Point Hardware
8946 @cindex floating point
8948 Depending on the configuration, @value{GDBN} may be able to give
8949 you more information about the status of the floating point hardware.
8954 Display hardware-dependent information about the floating
8955 point unit. The exact contents and layout vary depending on the
8956 floating point chip. Currently, @samp{info float} is supported on
8957 the ARM and x86 machines.
8961 @section Vector Unit
8964 Depending on the configuration, @value{GDBN} may be able to give you
8965 more information about the status of the vector unit.
8970 Display information about the vector unit. The exact contents and
8971 layout vary depending on the hardware.
8974 @node OS Information
8975 @section Operating System Auxiliary Information
8976 @cindex OS information
8978 @value{GDBN} provides interfaces to useful OS facilities that can help
8979 you debug your program.
8981 @cindex @code{ptrace} system call
8982 @cindex @code{struct user} contents
8983 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8984 machines), it interfaces with the inferior via the @code{ptrace}
8985 system call. The operating system creates a special sata structure,
8986 called @code{struct user}, for this interface. You can use the
8987 command @code{info udot} to display the contents of this data
8993 Display the contents of the @code{struct user} maintained by the OS
8994 kernel for the program being debugged. @value{GDBN} displays the
8995 contents of @code{struct user} as a list of hex numbers, similar to
8996 the @code{examine} command.
8999 @cindex auxiliary vector
9000 @cindex vector, auxiliary
9001 Some operating systems supply an @dfn{auxiliary vector} to programs at
9002 startup. This is akin to the arguments and environment that you
9003 specify for a program, but contains a system-dependent variety of
9004 binary values that tell system libraries important details about the
9005 hardware, operating system, and process. Each value's purpose is
9006 identified by an integer tag; the meanings are well-known but system-specific.
9007 Depending on the configuration and operating system facilities,
9008 @value{GDBN} may be able to show you this information. For remote
9009 targets, this functionality may further depend on the remote stub's
9010 support of the @samp{qXfer:auxv:read} packet, see
9011 @ref{qXfer auxiliary vector read}.
9016 Display the auxiliary vector of the inferior, which can be either a
9017 live process or a core dump file. @value{GDBN} prints each tag value
9018 numerically, and also shows names and text descriptions for recognized
9019 tags. Some values in the vector are numbers, some bit masks, and some
9020 pointers to strings or other data. @value{GDBN} displays each value in the
9021 most appropriate form for a recognized tag, and in hexadecimal for
9022 an unrecognized tag.
9025 On some targets, @value{GDBN} can access operating-system-specific information
9026 and display it to user, without interpretation. For remote targets,
9027 this functionality depends on the remote stub's support of the
9028 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9033 List the types of OS information available for the target. If the
9034 target does not return a list of possible types, this command will
9037 @kindex info os processes
9038 @item info os processes
9039 Display the list of processes on the target. For each process,
9040 @value{GDBN} prints the process identifier, the name of the user, and
9041 the command corresponding to the process.
9044 @node Memory Region Attributes
9045 @section Memory Region Attributes
9046 @cindex memory region attributes
9048 @dfn{Memory region attributes} allow you to describe special handling
9049 required by regions of your target's memory. @value{GDBN} uses
9050 attributes to determine whether to allow certain types of memory
9051 accesses; whether to use specific width accesses; and whether to cache
9052 target memory. By default the description of memory regions is
9053 fetched from the target (if the current target supports this), but the
9054 user can override the fetched regions.
9056 Defined memory regions can be individually enabled and disabled. When a
9057 memory region is disabled, @value{GDBN} uses the default attributes when
9058 accessing memory in that region. Similarly, if no memory regions have
9059 been defined, @value{GDBN} uses the default attributes when accessing
9062 When a memory region is defined, it is given a number to identify it;
9063 to enable, disable, or remove a memory region, you specify that number.
9067 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9068 Define a memory region bounded by @var{lower} and @var{upper} with
9069 attributes @var{attributes}@dots{}, and add it to the list of regions
9070 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9071 case: it is treated as the target's maximum memory address.
9072 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9075 Discard any user changes to the memory regions and use target-supplied
9076 regions, if available, or no regions if the target does not support.
9079 @item delete mem @var{nums}@dots{}
9080 Remove memory regions @var{nums}@dots{} from the list of regions
9081 monitored by @value{GDBN}.
9084 @item disable mem @var{nums}@dots{}
9085 Disable monitoring of memory regions @var{nums}@dots{}.
9086 A disabled memory region is not forgotten.
9087 It may be enabled again later.
9090 @item enable mem @var{nums}@dots{}
9091 Enable monitoring of memory regions @var{nums}@dots{}.
9095 Print a table of all defined memory regions, with the following columns
9099 @item Memory Region Number
9100 @item Enabled or Disabled.
9101 Enabled memory regions are marked with @samp{y}.
9102 Disabled memory regions are marked with @samp{n}.
9105 The address defining the inclusive lower bound of the memory region.
9108 The address defining the exclusive upper bound of the memory region.
9111 The list of attributes set for this memory region.
9116 @subsection Attributes
9118 @subsubsection Memory Access Mode
9119 The access mode attributes set whether @value{GDBN} may make read or
9120 write accesses to a memory region.
9122 While these attributes prevent @value{GDBN} from performing invalid
9123 memory accesses, they do nothing to prevent the target system, I/O DMA,
9124 etc.@: from accessing memory.
9128 Memory is read only.
9130 Memory is write only.
9132 Memory is read/write. This is the default.
9135 @subsubsection Memory Access Size
9136 The access size attribute tells @value{GDBN} to use specific sized
9137 accesses in the memory region. Often memory mapped device registers
9138 require specific sized accesses. If no access size attribute is
9139 specified, @value{GDBN} may use accesses of any size.
9143 Use 8 bit memory accesses.
9145 Use 16 bit memory accesses.
9147 Use 32 bit memory accesses.
9149 Use 64 bit memory accesses.
9152 @c @subsubsection Hardware/Software Breakpoints
9153 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9154 @c will use hardware or software breakpoints for the internal breakpoints
9155 @c used by the step, next, finish, until, etc. commands.
9159 @c Always use hardware breakpoints
9160 @c @item swbreak (default)
9163 @subsubsection Data Cache
9164 The data cache attributes set whether @value{GDBN} will cache target
9165 memory. While this generally improves performance by reducing debug
9166 protocol overhead, it can lead to incorrect results because @value{GDBN}
9167 does not know about volatile variables or memory mapped device
9172 Enable @value{GDBN} to cache target memory.
9174 Disable @value{GDBN} from caching target memory. This is the default.
9177 @subsection Memory Access Checking
9178 @value{GDBN} can be instructed to refuse accesses to memory that is
9179 not explicitly described. This can be useful if accessing such
9180 regions has undesired effects for a specific target, or to provide
9181 better error checking. The following commands control this behaviour.
9184 @kindex set mem inaccessible-by-default
9185 @item set mem inaccessible-by-default [on|off]
9186 If @code{on} is specified, make @value{GDBN} treat memory not
9187 explicitly described by the memory ranges as non-existent and refuse accesses
9188 to such memory. The checks are only performed if there's at least one
9189 memory range defined. If @code{off} is specified, make @value{GDBN}
9190 treat the memory not explicitly described by the memory ranges as RAM.
9191 The default value is @code{on}.
9192 @kindex show mem inaccessible-by-default
9193 @item show mem inaccessible-by-default
9194 Show the current handling of accesses to unknown memory.
9198 @c @subsubsection Memory Write Verification
9199 @c The memory write verification attributes set whether @value{GDBN}
9200 @c will re-reads data after each write to verify the write was successful.
9204 @c @item noverify (default)
9207 @node Dump/Restore Files
9208 @section Copy Between Memory and a File
9209 @cindex dump/restore files
9210 @cindex append data to a file
9211 @cindex dump data to a file
9212 @cindex restore data from a file
9214 You can use the commands @code{dump}, @code{append}, and
9215 @code{restore} to copy data between target memory and a file. The
9216 @code{dump} and @code{append} commands write data to a file, and the
9217 @code{restore} command reads data from a file back into the inferior's
9218 memory. Files may be in binary, Motorola S-record, Intel hex, or
9219 Tektronix Hex format; however, @value{GDBN} can only append to binary
9225 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9226 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9227 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9228 or the value of @var{expr}, to @var{filename} in the given format.
9230 The @var{format} parameter may be any one of:
9237 Motorola S-record format.
9239 Tektronix Hex format.
9242 @value{GDBN} uses the same definitions of these formats as the
9243 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9244 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9248 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9249 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9250 Append the contents of memory from @var{start_addr} to @var{end_addr},
9251 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9252 (@value{GDBN} can only append data to files in raw binary form.)
9255 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9256 Restore the contents of file @var{filename} into memory. The
9257 @code{restore} command can automatically recognize any known @sc{bfd}
9258 file format, except for raw binary. To restore a raw binary file you
9259 must specify the optional keyword @code{binary} after the filename.
9261 If @var{bias} is non-zero, its value will be added to the addresses
9262 contained in the file. Binary files always start at address zero, so
9263 they will be restored at address @var{bias}. Other bfd files have
9264 a built-in location; they will be restored at offset @var{bias}
9267 If @var{start} and/or @var{end} are non-zero, then only data between
9268 file offset @var{start} and file offset @var{end} will be restored.
9269 These offsets are relative to the addresses in the file, before
9270 the @var{bias} argument is applied.
9274 @node Core File Generation
9275 @section How to Produce a Core File from Your Program
9276 @cindex dump core from inferior
9278 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9279 image of a running process and its process status (register values
9280 etc.). Its primary use is post-mortem debugging of a program that
9281 crashed while it ran outside a debugger. A program that crashes
9282 automatically produces a core file, unless this feature is disabled by
9283 the user. @xref{Files}, for information on invoking @value{GDBN} in
9284 the post-mortem debugging mode.
9286 Occasionally, you may wish to produce a core file of the program you
9287 are debugging in order to preserve a snapshot of its state.
9288 @value{GDBN} has a special command for that.
9292 @kindex generate-core-file
9293 @item generate-core-file [@var{file}]
9294 @itemx gcore [@var{file}]
9295 Produce a core dump of the inferior process. The optional argument
9296 @var{file} specifies the file name where to put the core dump. If not
9297 specified, the file name defaults to @file{core.@var{pid}}, where
9298 @var{pid} is the inferior process ID.
9300 Note that this command is implemented only for some systems (as of
9301 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9304 @node Character Sets
9305 @section Character Sets
9306 @cindex character sets
9308 @cindex translating between character sets
9309 @cindex host character set
9310 @cindex target character set
9312 If the program you are debugging uses a different character set to
9313 represent characters and strings than the one @value{GDBN} uses itself,
9314 @value{GDBN} can automatically translate between the character sets for
9315 you. The character set @value{GDBN} uses we call the @dfn{host
9316 character set}; the one the inferior program uses we call the
9317 @dfn{target character set}.
9319 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9320 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9321 remote protocol (@pxref{Remote Debugging}) to debug a program
9322 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9323 then the host character set is Latin-1, and the target character set is
9324 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9325 target-charset EBCDIC-US}, then @value{GDBN} translates between
9326 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9327 character and string literals in expressions.
9329 @value{GDBN} has no way to automatically recognize which character set
9330 the inferior program uses; you must tell it, using the @code{set
9331 target-charset} command, described below.
9333 Here are the commands for controlling @value{GDBN}'s character set
9337 @item set target-charset @var{charset}
9338 @kindex set target-charset
9339 Set the current target character set to @var{charset}. To display the
9340 list of supported target character sets, type
9341 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9343 @item set host-charset @var{charset}
9344 @kindex set host-charset
9345 Set the current host character set to @var{charset}.
9347 By default, @value{GDBN} uses a host character set appropriate to the
9348 system it is running on; you can override that default using the
9349 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9350 automatically determine the appropriate host character set. In this
9351 case, @value{GDBN} uses @samp{UTF-8}.
9353 @value{GDBN} can only use certain character sets as its host character
9354 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9355 @value{GDBN} will list the host character sets it supports.
9357 @item set charset @var{charset}
9359 Set the current host and target character sets to @var{charset}. As
9360 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9361 @value{GDBN} will list the names of the character sets that can be used
9362 for both host and target.
9365 @kindex show charset
9366 Show the names of the current host and target character sets.
9368 @item show host-charset
9369 @kindex show host-charset
9370 Show the name of the current host character set.
9372 @item show target-charset
9373 @kindex show target-charset
9374 Show the name of the current target character set.
9376 @item set target-wide-charset @var{charset}
9377 @kindex set target-wide-charset
9378 Set the current target's wide character set to @var{charset}. This is
9379 the character set used by the target's @code{wchar_t} type. To
9380 display the list of supported wide character sets, type
9381 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9383 @item show target-wide-charset
9384 @kindex show target-wide-charset
9385 Show the name of the current target's wide character set.
9388 Here is an example of @value{GDBN}'s character set support in action.
9389 Assume that the following source code has been placed in the file
9390 @file{charset-test.c}:
9396 = @{72, 101, 108, 108, 111, 44, 32, 119,
9397 111, 114, 108, 100, 33, 10, 0@};
9398 char ibm1047_hello[]
9399 = @{200, 133, 147, 147, 150, 107, 64, 166,
9400 150, 153, 147, 132, 90, 37, 0@};
9404 printf ("Hello, world!\n");
9408 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9409 containing the string @samp{Hello, world!} followed by a newline,
9410 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9412 We compile the program, and invoke the debugger on it:
9415 $ gcc -g charset-test.c -o charset-test
9416 $ gdb -nw charset-test
9417 GNU gdb 2001-12-19-cvs
9418 Copyright 2001 Free Software Foundation, Inc.
9423 We can use the @code{show charset} command to see what character sets
9424 @value{GDBN} is currently using to interpret and display characters and
9428 (@value{GDBP}) show charset
9429 The current host and target character set is `ISO-8859-1'.
9433 For the sake of printing this manual, let's use @sc{ascii} as our
9434 initial character set:
9436 (@value{GDBP}) set charset ASCII
9437 (@value{GDBP}) show charset
9438 The current host and target character set is `ASCII'.
9442 Let's assume that @sc{ascii} is indeed the correct character set for our
9443 host system --- in other words, let's assume that if @value{GDBN} prints
9444 characters using the @sc{ascii} character set, our terminal will display
9445 them properly. Since our current target character set is also
9446 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9449 (@value{GDBP}) print ascii_hello
9450 $1 = 0x401698 "Hello, world!\n"
9451 (@value{GDBP}) print ascii_hello[0]
9456 @value{GDBN} uses the target character set for character and string
9457 literals you use in expressions:
9460 (@value{GDBP}) print '+'
9465 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9468 @value{GDBN} relies on the user to tell it which character set the
9469 target program uses. If we print @code{ibm1047_hello} while our target
9470 character set is still @sc{ascii}, we get jibberish:
9473 (@value{GDBP}) print ibm1047_hello
9474 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9475 (@value{GDBP}) print ibm1047_hello[0]
9480 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9481 @value{GDBN} tells us the character sets it supports:
9484 (@value{GDBP}) set target-charset
9485 ASCII EBCDIC-US IBM1047 ISO-8859-1
9486 (@value{GDBP}) set target-charset
9489 We can select @sc{ibm1047} as our target character set, and examine the
9490 program's strings again. Now the @sc{ascii} string is wrong, but
9491 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9492 target character set, @sc{ibm1047}, to the host character set,
9493 @sc{ascii}, and they display correctly:
9496 (@value{GDBP}) set target-charset IBM1047
9497 (@value{GDBP}) show charset
9498 The current host character set is `ASCII'.
9499 The current target character set is `IBM1047'.
9500 (@value{GDBP}) print ascii_hello
9501 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9502 (@value{GDBP}) print ascii_hello[0]
9504 (@value{GDBP}) print ibm1047_hello
9505 $8 = 0x4016a8 "Hello, world!\n"
9506 (@value{GDBP}) print ibm1047_hello[0]
9511 As above, @value{GDBN} uses the target character set for character and
9512 string literals you use in expressions:
9515 (@value{GDBP}) print '+'
9520 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9523 @node Caching Remote Data
9524 @section Caching Data of Remote Targets
9525 @cindex caching data of remote targets
9527 @value{GDBN} caches data exchanged between the debugger and a
9528 remote target (@pxref{Remote Debugging}). Such caching generally improves
9529 performance, because it reduces the overhead of the remote protocol by
9530 bundling memory reads and writes into large chunks. Unfortunately, simply
9531 caching everything would lead to incorrect results, since @value{GDBN}
9532 does not necessarily know anything about volatile values, memory-mapped I/O
9533 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9534 memory can be changed @emph{while} a gdb command is executing.
9535 Therefore, by default, @value{GDBN} only caches data
9536 known to be on the stack@footnote{In non-stop mode, it is moderately
9537 rare for a running thread to modify the stack of a stopped thread
9538 in a way that would interfere with a backtrace, and caching of
9539 stack reads provides a significant speed up of remote backtraces.}.
9540 Other regions of memory can be explicitly marked as
9541 cacheable; see @pxref{Memory Region Attributes}.
9544 @kindex set remotecache
9545 @item set remotecache on
9546 @itemx set remotecache off
9547 This option no longer does anything; it exists for compatibility
9550 @kindex show remotecache
9551 @item show remotecache
9552 Show the current state of the obsolete remotecache flag.
9554 @kindex set stack-cache
9555 @item set stack-cache on
9556 @itemx set stack-cache off
9557 Enable or disable caching of stack accesses. When @code{ON}, use
9558 caching. By default, this option is @code{ON}.
9560 @kindex show stack-cache
9561 @item show stack-cache
9562 Show the current state of data caching for memory accesses.
9565 @item info dcache @r{[}line@r{]}
9566 Print the information about the data cache performance. The
9567 information displayed includes the dcache width and depth, and for
9568 each cache line, its number, address, and how many times it was
9569 referenced. This command is useful for debugging the data cache
9572 If a line number is specified, the contents of that line will be
9575 @item set dcache size @var{size}
9577 @kindex set dcache size
9578 Set maximum number of entries in dcache (dcache depth above).
9580 @item set dcache line-size @var{line-size}
9581 @cindex dcache line-size
9582 @kindex set dcache line-size
9583 Set number of bytes each dcache entry caches (dcache width above).
9584 Must be a power of 2.
9586 @item show dcache size
9587 @kindex show dcache size
9588 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9590 @item show dcache line-size
9591 @kindex show dcache line-size
9592 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9596 @node Searching Memory
9597 @section Search Memory
9598 @cindex searching memory
9600 Memory can be searched for a particular sequence of bytes with the
9601 @code{find} command.
9605 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9606 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9607 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9608 etc. The search begins at address @var{start_addr} and continues for either
9609 @var{len} bytes or through to @var{end_addr} inclusive.
9612 @var{s} and @var{n} are optional parameters.
9613 They may be specified in either order, apart or together.
9616 @item @var{s}, search query size
9617 The size of each search query value.
9623 halfwords (two bytes)
9627 giant words (eight bytes)
9630 All values are interpreted in the current language.
9631 This means, for example, that if the current source language is C/C@t{++}
9632 then searching for the string ``hello'' includes the trailing '\0'.
9634 If the value size is not specified, it is taken from the
9635 value's type in the current language.
9636 This is useful when one wants to specify the search
9637 pattern as a mixture of types.
9638 Note that this means, for example, that in the case of C-like languages
9639 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9640 which is typically four bytes.
9642 @item @var{n}, maximum number of finds
9643 The maximum number of matches to print. The default is to print all finds.
9646 You can use strings as search values. Quote them with double-quotes
9648 The string value is copied into the search pattern byte by byte,
9649 regardless of the endianness of the target and the size specification.
9651 The address of each match found is printed as well as a count of the
9652 number of matches found.
9654 The address of the last value found is stored in convenience variable
9656 A count of the number of matches is stored in @samp{$numfound}.
9658 For example, if stopped at the @code{printf} in this function:
9664 static char hello[] = "hello-hello";
9665 static struct @{ char c; short s; int i; @}
9666 __attribute__ ((packed)) mixed
9667 = @{ 'c', 0x1234, 0x87654321 @};
9668 printf ("%s\n", hello);
9673 you get during debugging:
9676 (gdb) find &hello[0], +sizeof(hello), "hello"
9677 0x804956d <hello.1620+6>
9679 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9680 0x8049567 <hello.1620>
9681 0x804956d <hello.1620+6>
9683 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9684 0x8049567 <hello.1620>
9686 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9687 0x8049560 <mixed.1625>
9689 (gdb) print $numfound
9692 $2 = (void *) 0x8049560
9695 @node Optimized Code
9696 @chapter Debugging Optimized Code
9697 @cindex optimized code, debugging
9698 @cindex debugging optimized code
9700 Almost all compilers support optimization. With optimization
9701 disabled, the compiler generates assembly code that corresponds
9702 directly to your source code, in a simplistic way. As the compiler
9703 applies more powerful optimizations, the generated assembly code
9704 diverges from your original source code. With help from debugging
9705 information generated by the compiler, @value{GDBN} can map from
9706 the running program back to constructs from your original source.
9708 @value{GDBN} is more accurate with optimization disabled. If you
9709 can recompile without optimization, it is easier to follow the
9710 progress of your program during debugging. But, there are many cases
9711 where you may need to debug an optimized version.
9713 When you debug a program compiled with @samp{-g -O}, remember that the
9714 optimizer has rearranged your code; the debugger shows you what is
9715 really there. Do not be too surprised when the execution path does not
9716 exactly match your source file! An extreme example: if you define a
9717 variable, but never use it, @value{GDBN} never sees that
9718 variable---because the compiler optimizes it out of existence.
9720 Some things do not work as well with @samp{-g -O} as with just
9721 @samp{-g}, particularly on machines with instruction scheduling. If in
9722 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9723 please report it to us as a bug (including a test case!).
9724 @xref{Variables}, for more information about debugging optimized code.
9727 * Inline Functions:: How @value{GDBN} presents inlining
9728 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9731 @node Inline Functions
9732 @section Inline Functions
9733 @cindex inline functions, debugging
9735 @dfn{Inlining} is an optimization that inserts a copy of the function
9736 body directly at each call site, instead of jumping to a shared
9737 routine. @value{GDBN} displays inlined functions just like
9738 non-inlined functions. They appear in backtraces. You can view their
9739 arguments and local variables, step into them with @code{step}, skip
9740 them with @code{next}, and escape from them with @code{finish}.
9741 You can check whether a function was inlined by using the
9742 @code{info frame} command.
9744 For @value{GDBN} to support inlined functions, the compiler must
9745 record information about inlining in the debug information ---
9746 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9747 other compilers do also. @value{GDBN} only supports inlined functions
9748 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9749 do not emit two required attributes (@samp{DW_AT_call_file} and
9750 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9751 function calls with earlier versions of @value{NGCC}. It instead
9752 displays the arguments and local variables of inlined functions as
9753 local variables in the caller.
9755 The body of an inlined function is directly included at its call site;
9756 unlike a non-inlined function, there are no instructions devoted to
9757 the call. @value{GDBN} still pretends that the call site and the
9758 start of the inlined function are different instructions. Stepping to
9759 the call site shows the call site, and then stepping again shows
9760 the first line of the inlined function, even though no additional
9761 instructions are executed.
9763 This makes source-level debugging much clearer; you can see both the
9764 context of the call and then the effect of the call. Only stepping by
9765 a single instruction using @code{stepi} or @code{nexti} does not do
9766 this; single instruction steps always show the inlined body.
9768 There are some ways that @value{GDBN} does not pretend that inlined
9769 function calls are the same as normal calls:
9773 You cannot set breakpoints on inlined functions. @value{GDBN}
9774 either reports that there is no symbol with that name, or else sets the
9775 breakpoint only on non-inlined copies of the function. This limitation
9776 will be removed in a future version of @value{GDBN}; until then,
9777 set a breakpoint by line number on the first line of the inlined
9781 Setting breakpoints at the call site of an inlined function may not
9782 work, because the call site does not contain any code. @value{GDBN}
9783 may incorrectly move the breakpoint to the next line of the enclosing
9784 function, after the call. This limitation will be removed in a future
9785 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9786 or inside the inlined function instead.
9789 @value{GDBN} cannot locate the return value of inlined calls after
9790 using the @code{finish} command. This is a limitation of compiler-generated
9791 debugging information; after @code{finish}, you can step to the next line
9792 and print a variable where your program stored the return value.
9796 @node Tail Call Frames
9797 @section Tail Call Frames
9798 @cindex tail call frames, debugging
9800 Function @code{B} can call function @code{C} in its very last statement. In
9801 unoptimized compilation the call of @code{C} is immediately followed by return
9802 instruction at the end of @code{B} code. Optimizing compiler may replace the
9803 call and return in function @code{B} into one jump to function @code{C}
9804 instead. Such use of a jump instruction is called @dfn{tail call}.
9806 During execution of function @code{C}, there will be no indication in the
9807 function call stack frames that it was tail-called from @code{B}. If function
9808 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9809 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9810 some cases @value{GDBN} can determine that @code{C} was tail-called from
9811 @code{B}, and it will then create fictitious call frame for that, with the
9812 return address set up as if @code{B} called @code{C} normally.
9814 This functionality is currently supported only by DWARF 2 debugging format and
9815 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9816 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9819 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9820 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9824 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9826 Stack level 1, frame at 0x7fffffffda30:
9827 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9828 tail call frame, caller of frame at 0x7fffffffda30
9829 source language c++.
9830 Arglist at unknown address.
9831 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9834 The detection of all the possible code path executions can find them ambiguous.
9835 There is no execution history stored (possible @ref{Reverse Execution} is never
9836 used for this purpose) and the last known caller could have reached the known
9837 callee by multiple different jump sequences. In such case @value{GDBN} still
9838 tries to show at least all the unambiguous top tail callers and all the
9839 unambiguous bottom tail calees, if any.
9842 @anchor{set debug entry-values}
9843 @item set debug entry-values
9844 @kindex set debug entry-values
9845 When set to on, enables printing of analysis messages for both frame argument
9846 values at function entry and tail calls. It will show all the possible valid
9847 tail calls code paths it has considered. It will also print the intersection
9848 of them with the final unambiguous (possibly partial or even empty) code path
9851 @item show debug entry-values
9852 @kindex show debug entry-values
9853 Show the current state of analysis messages printing for both frame argument
9854 values at function entry and tail calls.
9857 The analysis messages for tail calls can for example show why the virtual tail
9858 call frame for function @code{c} has not been recognized (due to the indirect
9859 reference by variable @code{x}):
9862 static void __attribute__((noinline, noclone)) c (void);
9863 void (*x) (void) = c;
9864 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9865 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9866 int main (void) @{ x (); return 0; @}
9868 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9869 DW_TAG_GNU_call_site 0x40039a in main
9871 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9874 #1 0x000000000040039a in main () at t.c:5
9877 Another possibility is an ambiguous virtual tail call frames resolution:
9881 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9882 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9883 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9884 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9885 static void __attribute__((noinline, noclone)) b (void)
9886 @{ if (i) c (); else e (); @}
9887 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9888 int main (void) @{ a (); return 0; @}
9890 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9891 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9892 tailcall: reduced: 0x4004d2(a) |
9895 #1 0x00000000004004d2 in a () at t.c:8
9896 #2 0x0000000000400395 in main () at t.c:9
9899 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9900 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9902 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9903 @ifset HAVE_MAKEINFO_CLICK
9905 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9906 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9908 @ifclear HAVE_MAKEINFO_CLICK
9910 @set CALLSEQ1B @value{CALLSEQ1A}
9911 @set CALLSEQ2B @value{CALLSEQ2A}
9914 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9915 The code can have possible execution paths @value{CALLSEQ1B} or
9916 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9918 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9919 has found. It then finds another possible calling sequcen - that one is
9920 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9921 printed as the @code{reduced:} calling sequence. That one could have many
9922 futher @code{compare:} and @code{reduced:} statements as long as there remain
9923 any non-ambiguous sequence entries.
9925 For the frame of function @code{b} in both cases there are different possible
9926 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9927 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9928 therefore this one is displayed to the user while the ambiguous frames are
9931 There can be also reasons why printing of frame argument values at function
9936 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9937 static void __attribute__((noinline, noclone)) a (int i);
9938 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9939 static void __attribute__((noinline, noclone)) a (int i)
9940 @{ if (i) b (i - 1); else c (0); @}
9941 int main (void) @{ a (5); return 0; @}
9944 #0 c (i=i@@entry=0) at t.c:2
9945 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9946 function "a" at 0x400420 can call itself via tail calls
9947 i=<optimized out>) at t.c:6
9948 #2 0x000000000040036e in main () at t.c:7
9951 @value{GDBN} cannot find out from the inferior state if and how many times did
9952 function @code{a} call itself (via function @code{b}) as these calls would be
9953 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9954 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9955 prints @code{<optimized out>} instead.
9958 @chapter C Preprocessor Macros
9960 Some languages, such as C and C@t{++}, provide a way to define and invoke
9961 ``preprocessor macros'' which expand into strings of tokens.
9962 @value{GDBN} can evaluate expressions containing macro invocations, show
9963 the result of macro expansion, and show a macro's definition, including
9964 where it was defined.
9966 You may need to compile your program specially to provide @value{GDBN}
9967 with information about preprocessor macros. Most compilers do not
9968 include macros in their debugging information, even when you compile
9969 with the @option{-g} flag. @xref{Compilation}.
9971 A program may define a macro at one point, remove that definition later,
9972 and then provide a different definition after that. Thus, at different
9973 points in the program, a macro may have different definitions, or have
9974 no definition at all. If there is a current stack frame, @value{GDBN}
9975 uses the macros in scope at that frame's source code line. Otherwise,
9976 @value{GDBN} uses the macros in scope at the current listing location;
9979 Whenever @value{GDBN} evaluates an expression, it always expands any
9980 macro invocations present in the expression. @value{GDBN} also provides
9981 the following commands for working with macros explicitly.
9985 @kindex macro expand
9986 @cindex macro expansion, showing the results of preprocessor
9987 @cindex preprocessor macro expansion, showing the results of
9988 @cindex expanding preprocessor macros
9989 @item macro expand @var{expression}
9990 @itemx macro exp @var{expression}
9991 Show the results of expanding all preprocessor macro invocations in
9992 @var{expression}. Since @value{GDBN} simply expands macros, but does
9993 not parse the result, @var{expression} need not be a valid expression;
9994 it can be any string of tokens.
9997 @item macro expand-once @var{expression}
9998 @itemx macro exp1 @var{expression}
9999 @cindex expand macro once
10000 @i{(This command is not yet implemented.)} Show the results of
10001 expanding those preprocessor macro invocations that appear explicitly in
10002 @var{expression}. Macro invocations appearing in that expansion are
10003 left unchanged. This command allows you to see the effect of a
10004 particular macro more clearly, without being confused by further
10005 expansions. Since @value{GDBN} simply expands macros, but does not
10006 parse the result, @var{expression} need not be a valid expression; it
10007 can be any string of tokens.
10010 @cindex macro definition, showing
10011 @cindex definition of a macro, showing
10012 @cindex macros, from debug info
10013 @item info macro [-a|-all] [--] @var{macro}
10014 Show the current definition or all definitions of the named @var{macro},
10015 and describe the source location or compiler command-line where that
10016 definition was established. The optional double dash is to signify the end of
10017 argument processing and the beginning of @var{macro} for non C-like macros where
10018 the macro may begin with a hyphen.
10020 @kindex info macros
10021 @item info macros @var{linespec}
10022 Show all macro definitions that are in effect at the location specified
10023 by @var{linespec}, and describe the source location or compiler
10024 command-line where those definitions were established.
10026 @kindex macro define
10027 @cindex user-defined macros
10028 @cindex defining macros interactively
10029 @cindex macros, user-defined
10030 @item macro define @var{macro} @var{replacement-list}
10031 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10032 Introduce a definition for a preprocessor macro named @var{macro},
10033 invocations of which are replaced by the tokens given in
10034 @var{replacement-list}. The first form of this command defines an
10035 ``object-like'' macro, which takes no arguments; the second form
10036 defines a ``function-like'' macro, which takes the arguments given in
10039 A definition introduced by this command is in scope in every
10040 expression evaluated in @value{GDBN}, until it is removed with the
10041 @code{macro undef} command, described below. The definition overrides
10042 all definitions for @var{macro} present in the program being debugged,
10043 as well as any previous user-supplied definition.
10045 @kindex macro undef
10046 @item macro undef @var{macro}
10047 Remove any user-supplied definition for the macro named @var{macro}.
10048 This command only affects definitions provided with the @code{macro
10049 define} command, described above; it cannot remove definitions present
10050 in the program being debugged.
10054 List all the macros defined using the @code{macro define} command.
10057 @cindex macros, example of debugging with
10058 Here is a transcript showing the above commands in action. First, we
10059 show our source files:
10064 #include "sample.h"
10067 #define ADD(x) (M + x)
10072 printf ("Hello, world!\n");
10074 printf ("We're so creative.\n");
10076 printf ("Goodbye, world!\n");
10083 Now, we compile the program using the @sc{gnu} C compiler,
10084 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10085 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10086 and @option{-gdwarf-4}; we recommend always choosing the most recent
10087 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10088 includes information about preprocessor macros in the debugging
10092 $ gcc -gdwarf-2 -g3 sample.c -o sample
10096 Now, we start @value{GDBN} on our sample program:
10100 GNU gdb 2002-05-06-cvs
10101 Copyright 2002 Free Software Foundation, Inc.
10102 GDB is free software, @dots{}
10106 We can expand macros and examine their definitions, even when the
10107 program is not running. @value{GDBN} uses the current listing position
10108 to decide which macro definitions are in scope:
10111 (@value{GDBP}) list main
10114 5 #define ADD(x) (M + x)
10119 10 printf ("Hello, world!\n");
10121 12 printf ("We're so creative.\n");
10122 (@value{GDBP}) info macro ADD
10123 Defined at /home/jimb/gdb/macros/play/sample.c:5
10124 #define ADD(x) (M + x)
10125 (@value{GDBP}) info macro Q
10126 Defined at /home/jimb/gdb/macros/play/sample.h:1
10127 included at /home/jimb/gdb/macros/play/sample.c:2
10129 (@value{GDBP}) macro expand ADD(1)
10130 expands to: (42 + 1)
10131 (@value{GDBP}) macro expand-once ADD(1)
10132 expands to: once (M + 1)
10136 In the example above, note that @code{macro expand-once} expands only
10137 the macro invocation explicit in the original text --- the invocation of
10138 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10139 which was introduced by @code{ADD}.
10141 Once the program is running, @value{GDBN} uses the macro definitions in
10142 force at the source line of the current stack frame:
10145 (@value{GDBP}) break main
10146 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10148 Starting program: /home/jimb/gdb/macros/play/sample
10150 Breakpoint 1, main () at sample.c:10
10151 10 printf ("Hello, world!\n");
10155 At line 10, the definition of the macro @code{N} at line 9 is in force:
10158 (@value{GDBP}) info macro N
10159 Defined at /home/jimb/gdb/macros/play/sample.c:9
10161 (@value{GDBP}) macro expand N Q M
10162 expands to: 28 < 42
10163 (@value{GDBP}) print N Q M
10168 As we step over directives that remove @code{N}'s definition, and then
10169 give it a new definition, @value{GDBN} finds the definition (or lack
10170 thereof) in force at each point:
10173 (@value{GDBP}) next
10175 12 printf ("We're so creative.\n");
10176 (@value{GDBP}) info macro N
10177 The symbol `N' has no definition as a C/C++ preprocessor macro
10178 at /home/jimb/gdb/macros/play/sample.c:12
10179 (@value{GDBP}) next
10181 14 printf ("Goodbye, world!\n");
10182 (@value{GDBP}) info macro N
10183 Defined at /home/jimb/gdb/macros/play/sample.c:13
10185 (@value{GDBP}) macro expand N Q M
10186 expands to: 1729 < 42
10187 (@value{GDBP}) print N Q M
10192 In addition to source files, macros can be defined on the compilation command
10193 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10194 such a way, @value{GDBN} displays the location of their definition as line zero
10195 of the source file submitted to the compiler.
10198 (@value{GDBP}) info macro __STDC__
10199 Defined at /home/jimb/gdb/macros/play/sample.c:0
10206 @chapter Tracepoints
10207 @c This chapter is based on the documentation written by Michael
10208 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10210 @cindex tracepoints
10211 In some applications, it is not feasible for the debugger to interrupt
10212 the program's execution long enough for the developer to learn
10213 anything helpful about its behavior. If the program's correctness
10214 depends on its real-time behavior, delays introduced by a debugger
10215 might cause the program to change its behavior drastically, or perhaps
10216 fail, even when the code itself is correct. It is useful to be able
10217 to observe the program's behavior without interrupting it.
10219 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10220 specify locations in the program, called @dfn{tracepoints}, and
10221 arbitrary expressions to evaluate when those tracepoints are reached.
10222 Later, using the @code{tfind} command, you can examine the values
10223 those expressions had when the program hit the tracepoints. The
10224 expressions may also denote objects in memory---structures or arrays,
10225 for example---whose values @value{GDBN} should record; while visiting
10226 a particular tracepoint, you may inspect those objects as if they were
10227 in memory at that moment. However, because @value{GDBN} records these
10228 values without interacting with you, it can do so quickly and
10229 unobtrusively, hopefully not disturbing the program's behavior.
10231 The tracepoint facility is currently available only for remote
10232 targets. @xref{Targets}. In addition, your remote target must know
10233 how to collect trace data. This functionality is implemented in the
10234 remote stub; however, none of the stubs distributed with @value{GDBN}
10235 support tracepoints as of this writing. The format of the remote
10236 packets used to implement tracepoints are described in @ref{Tracepoint
10239 It is also possible to get trace data from a file, in a manner reminiscent
10240 of corefiles; you specify the filename, and use @code{tfind} to search
10241 through the file. @xref{Trace Files}, for more details.
10243 This chapter describes the tracepoint commands and features.
10246 * Set Tracepoints::
10247 * Analyze Collected Data::
10248 * Tracepoint Variables::
10252 @node Set Tracepoints
10253 @section Commands to Set Tracepoints
10255 Before running such a @dfn{trace experiment}, an arbitrary number of
10256 tracepoints can be set. A tracepoint is actually a special type of
10257 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10258 standard breakpoint commands. For instance, as with breakpoints,
10259 tracepoint numbers are successive integers starting from one, and many
10260 of the commands associated with tracepoints take the tracepoint number
10261 as their argument, to identify which tracepoint to work on.
10263 For each tracepoint, you can specify, in advance, some arbitrary set
10264 of data that you want the target to collect in the trace buffer when
10265 it hits that tracepoint. The collected data can include registers,
10266 local variables, or global data. Later, you can use @value{GDBN}
10267 commands to examine the values these data had at the time the
10268 tracepoint was hit.
10270 Tracepoints do not support every breakpoint feature. Ignore counts on
10271 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10272 commands when they are hit. Tracepoints may not be thread-specific
10275 @cindex fast tracepoints
10276 Some targets may support @dfn{fast tracepoints}, which are inserted in
10277 a different way (such as with a jump instead of a trap), that is
10278 faster but possibly restricted in where they may be installed.
10280 @cindex static tracepoints
10281 @cindex markers, static tracepoints
10282 @cindex probing markers, static tracepoints
10283 Regular and fast tracepoints are dynamic tracing facilities, meaning
10284 that they can be used to insert tracepoints at (almost) any location
10285 in the target. Some targets may also support controlling @dfn{static
10286 tracepoints} from @value{GDBN}. With static tracing, a set of
10287 instrumentation points, also known as @dfn{markers}, are embedded in
10288 the target program, and can be activated or deactivated by name or
10289 address. These are usually placed at locations which facilitate
10290 investigating what the target is actually doing. @value{GDBN}'s
10291 support for static tracing includes being able to list instrumentation
10292 points, and attach them with @value{GDBN} defined high level
10293 tracepoints that expose the whole range of convenience of
10294 @value{GDBN}'s tracepoints support. Namely, support for collecting
10295 registers values and values of global or local (to the instrumentation
10296 point) variables; tracepoint conditions and trace state variables.
10297 The act of installing a @value{GDBN} static tracepoint on an
10298 instrumentation point, or marker, is referred to as @dfn{probing} a
10299 static tracepoint marker.
10301 @code{gdbserver} supports tracepoints on some target systems.
10302 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10304 This section describes commands to set tracepoints and associated
10305 conditions and actions.
10308 * Create and Delete Tracepoints::
10309 * Enable and Disable Tracepoints::
10310 * Tracepoint Passcounts::
10311 * Tracepoint Conditions::
10312 * Trace State Variables::
10313 * Tracepoint Actions::
10314 * Listing Tracepoints::
10315 * Listing Static Tracepoint Markers::
10316 * Starting and Stopping Trace Experiments::
10317 * Tracepoint Restrictions::
10320 @node Create and Delete Tracepoints
10321 @subsection Create and Delete Tracepoints
10324 @cindex set tracepoint
10326 @item trace @var{location}
10327 The @code{trace} command is very similar to the @code{break} command.
10328 Its argument @var{location} can be a source line, a function name, or
10329 an address in the target program. @xref{Specify Location}. The
10330 @code{trace} command defines a tracepoint, which is a point in the
10331 target program where the debugger will briefly stop, collect some
10332 data, and then allow the program to continue. Setting a tracepoint or
10333 changing its actions takes effect immediately if the remote stub
10334 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10336 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10337 these changes don't take effect until the next @code{tstart}
10338 command, and once a trace experiment is running, further changes will
10339 not have any effect until the next trace experiment starts. In addition,
10340 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10341 address is not yet resolved. (This is similar to pending breakpoints.)
10342 Pending tracepoints are not downloaded to the target and not installed
10343 until they are resolved. The resolution of pending tracepoints requires
10344 @value{GDBN} support---when debugging with the remote target, and
10345 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10346 tracing}), pending tracepoints can not be resolved (and downloaded to
10347 the remote stub) while @value{GDBN} is disconnected.
10349 Here are some examples of using the @code{trace} command:
10352 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10354 (@value{GDBP}) @b{trace +2} // 2 lines forward
10356 (@value{GDBP}) @b{trace my_function} // first source line of function
10358 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10360 (@value{GDBP}) @b{trace *0x2117c4} // an address
10364 You can abbreviate @code{trace} as @code{tr}.
10366 @item trace @var{location} if @var{cond}
10367 Set a tracepoint with condition @var{cond}; evaluate the expression
10368 @var{cond} each time the tracepoint is reached, and collect data only
10369 if the value is nonzero---that is, if @var{cond} evaluates as true.
10370 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10371 information on tracepoint conditions.
10373 @item ftrace @var{location} [ if @var{cond} ]
10374 @cindex set fast tracepoint
10375 @cindex fast tracepoints, setting
10377 The @code{ftrace} command sets a fast tracepoint. For targets that
10378 support them, fast tracepoints will use a more efficient but possibly
10379 less general technique to trigger data collection, such as a jump
10380 instruction instead of a trap, or some sort of hardware support. It
10381 may not be possible to create a fast tracepoint at the desired
10382 location, in which case the command will exit with an explanatory
10385 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10388 On 32-bit x86-architecture systems, fast tracepoints normally need to
10389 be placed at an instruction that is 5 bytes or longer, but can be
10390 placed at 4-byte instructions if the low 64K of memory of the target
10391 program is available to install trampolines. Some Unix-type systems,
10392 such as @sc{gnu}/Linux, exclude low addresses from the program's
10393 address space; but for instance with the Linux kernel it is possible
10394 to let @value{GDBN} use this area by doing a @command{sysctl} command
10395 to set the @code{mmap_min_addr} kernel parameter, as in
10398 sudo sysctl -w vm.mmap_min_addr=32768
10402 which sets the low address to 32K, which leaves plenty of room for
10403 trampolines. The minimum address should be set to a page boundary.
10405 @item strace @var{location} [ if @var{cond} ]
10406 @cindex set static tracepoint
10407 @cindex static tracepoints, setting
10408 @cindex probe static tracepoint marker
10410 The @code{strace} command sets a static tracepoint. For targets that
10411 support it, setting a static tracepoint probes a static
10412 instrumentation point, or marker, found at @var{location}. It may not
10413 be possible to set a static tracepoint at the desired location, in
10414 which case the command will exit with an explanatory message.
10416 @value{GDBN} handles arguments to @code{strace} exactly as for
10417 @code{trace}, with the addition that the user can also specify
10418 @code{-m @var{marker}} as @var{location}. This probes the marker
10419 identified by the @var{marker} string identifier. This identifier
10420 depends on the static tracepoint backend library your program is
10421 using. You can find all the marker identifiers in the @samp{ID} field
10422 of the @code{info static-tracepoint-markers} command output.
10423 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10424 Markers}. For example, in the following small program using the UST
10430 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10435 the marker id is composed of joining the first two arguments to the
10436 @code{trace_mark} call with a slash, which translates to:
10439 (@value{GDBP}) info static-tracepoint-markers
10440 Cnt Enb ID Address What
10441 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10447 so you may probe the marker above with:
10450 (@value{GDBP}) strace -m ust/bar33
10453 Static tracepoints accept an extra collect action --- @code{collect
10454 $_sdata}. This collects arbitrary user data passed in the probe point
10455 call to the tracing library. In the UST example above, you'll see
10456 that the third argument to @code{trace_mark} is a printf-like format
10457 string. The user data is then the result of running that formating
10458 string against the following arguments. Note that @code{info
10459 static-tracepoint-markers} command output lists that format string in
10460 the @samp{Data:} field.
10462 You can inspect this data when analyzing the trace buffer, by printing
10463 the $_sdata variable like any other variable available to
10464 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10467 @cindex last tracepoint number
10468 @cindex recent tracepoint number
10469 @cindex tracepoint number
10470 The convenience variable @code{$tpnum} records the tracepoint number
10471 of the most recently set tracepoint.
10473 @kindex delete tracepoint
10474 @cindex tracepoint deletion
10475 @item delete tracepoint @r{[}@var{num}@r{]}
10476 Permanently delete one or more tracepoints. With no argument, the
10477 default is to delete all tracepoints. Note that the regular
10478 @code{delete} command can remove tracepoints also.
10483 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10485 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10489 You can abbreviate this command as @code{del tr}.
10492 @node Enable and Disable Tracepoints
10493 @subsection Enable and Disable Tracepoints
10495 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10498 @kindex disable tracepoint
10499 @item disable tracepoint @r{[}@var{num}@r{]}
10500 Disable tracepoint @var{num}, or all tracepoints if no argument
10501 @var{num} is given. A disabled tracepoint will have no effect during
10502 a trace experiment, but it is not forgotten. You can re-enable
10503 a disabled tracepoint using the @code{enable tracepoint} command.
10504 If the command is issued during a trace experiment and the debug target
10505 has support for disabling tracepoints during a trace experiment, then the
10506 change will be effective immediately. Otherwise, it will be applied to the
10507 next trace experiment.
10509 @kindex enable tracepoint
10510 @item enable tracepoint @r{[}@var{num}@r{]}
10511 Enable tracepoint @var{num}, or all tracepoints. If this command is
10512 issued during a trace experiment and the debug target supports enabling
10513 tracepoints during a trace experiment, then the enabled tracepoints will
10514 become effective immediately. Otherwise, they will become effective the
10515 next time a trace experiment is run.
10518 @node Tracepoint Passcounts
10519 @subsection Tracepoint Passcounts
10523 @cindex tracepoint pass count
10524 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10525 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10526 automatically stop a trace experiment. If a tracepoint's passcount is
10527 @var{n}, then the trace experiment will be automatically stopped on
10528 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10529 @var{num} is not specified, the @code{passcount} command sets the
10530 passcount of the most recently defined tracepoint. If no passcount is
10531 given, the trace experiment will run until stopped explicitly by the
10537 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10538 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10540 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10541 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10542 (@value{GDBP}) @b{trace foo}
10543 (@value{GDBP}) @b{pass 3}
10544 (@value{GDBP}) @b{trace bar}
10545 (@value{GDBP}) @b{pass 2}
10546 (@value{GDBP}) @b{trace baz}
10547 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10548 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10549 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10550 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10554 @node Tracepoint Conditions
10555 @subsection Tracepoint Conditions
10556 @cindex conditional tracepoints
10557 @cindex tracepoint conditions
10559 The simplest sort of tracepoint collects data every time your program
10560 reaches a specified place. You can also specify a @dfn{condition} for
10561 a tracepoint. A condition is just a Boolean expression in your
10562 programming language (@pxref{Expressions, ,Expressions}). A
10563 tracepoint with a condition evaluates the expression each time your
10564 program reaches it, and data collection happens only if the condition
10567 Tracepoint conditions can be specified when a tracepoint is set, by
10568 using @samp{if} in the arguments to the @code{trace} command.
10569 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10570 also be set or changed at any time with the @code{condition} command,
10571 just as with breakpoints.
10573 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10574 the conditional expression itself. Instead, @value{GDBN} encodes the
10575 expression into an agent expression (@pxref{Agent Expressions})
10576 suitable for execution on the target, independently of @value{GDBN}.
10577 Global variables become raw memory locations, locals become stack
10578 accesses, and so forth.
10580 For instance, suppose you have a function that is usually called
10581 frequently, but should not be called after an error has occurred. You
10582 could use the following tracepoint command to collect data about calls
10583 of that function that happen while the error code is propagating
10584 through the program; an unconditional tracepoint could end up
10585 collecting thousands of useless trace frames that you would have to
10589 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10592 @node Trace State Variables
10593 @subsection Trace State Variables
10594 @cindex trace state variables
10596 A @dfn{trace state variable} is a special type of variable that is
10597 created and managed by target-side code. The syntax is the same as
10598 that for GDB's convenience variables (a string prefixed with ``$''),
10599 but they are stored on the target. They must be created explicitly,
10600 using a @code{tvariable} command. They are always 64-bit signed
10603 Trace state variables are remembered by @value{GDBN}, and downloaded
10604 to the target along with tracepoint information when the trace
10605 experiment starts. There are no intrinsic limits on the number of
10606 trace state variables, beyond memory limitations of the target.
10608 @cindex convenience variables, and trace state variables
10609 Although trace state variables are managed by the target, you can use
10610 them in print commands and expressions as if they were convenience
10611 variables; @value{GDBN} will get the current value from the target
10612 while the trace experiment is running. Trace state variables share
10613 the same namespace as other ``$'' variables, which means that you
10614 cannot have trace state variables with names like @code{$23} or
10615 @code{$pc}, nor can you have a trace state variable and a convenience
10616 variable with the same name.
10620 @item tvariable $@var{name} [ = @var{expression} ]
10622 The @code{tvariable} command creates a new trace state variable named
10623 @code{$@var{name}}, and optionally gives it an initial value of
10624 @var{expression}. @var{expression} is evaluated when this command is
10625 entered; the result will be converted to an integer if possible,
10626 otherwise @value{GDBN} will report an error. A subsequent
10627 @code{tvariable} command specifying the same name does not create a
10628 variable, but instead assigns the supplied initial value to the
10629 existing variable of that name, overwriting any previous initial
10630 value. The default initial value is 0.
10632 @item info tvariables
10633 @kindex info tvariables
10634 List all the trace state variables along with their initial values.
10635 Their current values may also be displayed, if the trace experiment is
10638 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10639 @kindex delete tvariable
10640 Delete the given trace state variables, or all of them if no arguments
10645 @node Tracepoint Actions
10646 @subsection Tracepoint Action Lists
10650 @cindex tracepoint actions
10651 @item actions @r{[}@var{num}@r{]}
10652 This command will prompt for a list of actions to be taken when the
10653 tracepoint is hit. If the tracepoint number @var{num} is not
10654 specified, this command sets the actions for the one that was most
10655 recently defined (so that you can define a tracepoint and then say
10656 @code{actions} without bothering about its number). You specify the
10657 actions themselves on the following lines, one action at a time, and
10658 terminate the actions list with a line containing just @code{end}. So
10659 far, the only defined actions are @code{collect}, @code{teval}, and
10660 @code{while-stepping}.
10662 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10663 Commands, ,Breakpoint Command Lists}), except that only the defined
10664 actions are allowed; any other @value{GDBN} command is rejected.
10666 @cindex remove actions from a tracepoint
10667 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10668 and follow it immediately with @samp{end}.
10671 (@value{GDBP}) @b{collect @var{data}} // collect some data
10673 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10675 (@value{GDBP}) @b{end} // signals the end of actions.
10678 In the following example, the action list begins with @code{collect}
10679 commands indicating the things to be collected when the tracepoint is
10680 hit. Then, in order to single-step and collect additional data
10681 following the tracepoint, a @code{while-stepping} command is used,
10682 followed by the list of things to be collected after each step in a
10683 sequence of single steps. The @code{while-stepping} command is
10684 terminated by its own separate @code{end} command. Lastly, the action
10685 list is terminated by an @code{end} command.
10688 (@value{GDBP}) @b{trace foo}
10689 (@value{GDBP}) @b{actions}
10690 Enter actions for tracepoint 1, one per line:
10693 > while-stepping 12
10694 > collect $pc, arr[i]
10699 @kindex collect @r{(tracepoints)}
10700 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10701 Collect values of the given expressions when the tracepoint is hit.
10702 This command accepts a comma-separated list of any valid expressions.
10703 In addition to global, static, or local variables, the following
10704 special arguments are supported:
10708 Collect all registers.
10711 Collect all function arguments.
10714 Collect all local variables.
10717 Collect the return address. This is helpful if you want to see more
10721 @vindex $_sdata@r{, collect}
10722 Collect static tracepoint marker specific data. Only available for
10723 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10724 Lists}. On the UST static tracepoints library backend, an
10725 instrumentation point resembles a @code{printf} function call. The
10726 tracing library is able to collect user specified data formatted to a
10727 character string using the format provided by the programmer that
10728 instrumented the program. Other backends have similar mechanisms.
10729 Here's an example of a UST marker call:
10732 const char master_name[] = "$your_name";
10733 trace_mark(channel1, marker1, "hello %s", master_name)
10736 In this case, collecting @code{$_sdata} collects the string
10737 @samp{hello $yourname}. When analyzing the trace buffer, you can
10738 inspect @samp{$_sdata} like any other variable available to
10742 You can give several consecutive @code{collect} commands, each one
10743 with a single argument, or one @code{collect} command with several
10744 arguments separated by commas; the effect is the same.
10746 The optional @var{mods} changes the usual handling of the arguments.
10747 @code{s} requests that pointers to chars be handled as strings, in
10748 particular collecting the contents of the memory being pointed at, up
10749 to the first zero. The upper bound is by default the value of the
10750 @code{print elements} variable; if @code{s} is followed by a decimal
10751 number, that is the upper bound instead. So for instance
10752 @samp{collect/s25 mystr} collects as many as 25 characters at
10755 The command @code{info scope} (@pxref{Symbols, info scope}) is
10756 particularly useful for figuring out what data to collect.
10758 @kindex teval @r{(tracepoints)}
10759 @item teval @var{expr1}, @var{expr2}, @dots{}
10760 Evaluate the given expressions when the tracepoint is hit. This
10761 command accepts a comma-separated list of expressions. The results
10762 are discarded, so this is mainly useful for assigning values to trace
10763 state variables (@pxref{Trace State Variables}) without adding those
10764 values to the trace buffer, as would be the case if the @code{collect}
10767 @kindex while-stepping @r{(tracepoints)}
10768 @item while-stepping @var{n}
10769 Perform @var{n} single-step instruction traces after the tracepoint,
10770 collecting new data after each step. The @code{while-stepping}
10771 command is followed by the list of what to collect while stepping
10772 (followed by its own @code{end} command):
10775 > while-stepping 12
10776 > collect $regs, myglobal
10782 Note that @code{$pc} is not automatically collected by
10783 @code{while-stepping}; you need to explicitly collect that register if
10784 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10787 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10788 @kindex set default-collect
10789 @cindex default collection action
10790 This variable is a list of expressions to collect at each tracepoint
10791 hit. It is effectively an additional @code{collect} action prepended
10792 to every tracepoint action list. The expressions are parsed
10793 individually for each tracepoint, so for instance a variable named
10794 @code{xyz} may be interpreted as a global for one tracepoint, and a
10795 local for another, as appropriate to the tracepoint's location.
10797 @item show default-collect
10798 @kindex show default-collect
10799 Show the list of expressions that are collected by default at each
10804 @node Listing Tracepoints
10805 @subsection Listing Tracepoints
10808 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10809 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10810 @cindex information about tracepoints
10811 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10812 Display information about the tracepoint @var{num}. If you don't
10813 specify a tracepoint number, displays information about all the
10814 tracepoints defined so far. The format is similar to that used for
10815 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10816 command, simply restricting itself to tracepoints.
10818 A tracepoint's listing may include additional information specific to
10823 its passcount as given by the @code{passcount @var{n}} command
10827 (@value{GDBP}) @b{info trace}
10828 Num Type Disp Enb Address What
10829 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10831 collect globfoo, $regs
10840 This command can be abbreviated @code{info tp}.
10843 @node Listing Static Tracepoint Markers
10844 @subsection Listing Static Tracepoint Markers
10847 @kindex info static-tracepoint-markers
10848 @cindex information about static tracepoint markers
10849 @item info static-tracepoint-markers
10850 Display information about all static tracepoint markers defined in the
10853 For each marker, the following columns are printed:
10857 An incrementing counter, output to help readability. This is not a
10860 The marker ID, as reported by the target.
10861 @item Enabled or Disabled
10862 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10863 that are not enabled.
10865 Where the marker is in your program, as a memory address.
10867 Where the marker is in the source for your program, as a file and line
10868 number. If the debug information included in the program does not
10869 allow @value{GDBN} to locate the source of the marker, this column
10870 will be left blank.
10874 In addition, the following information may be printed for each marker:
10878 User data passed to the tracing library by the marker call. In the
10879 UST backend, this is the format string passed as argument to the
10881 @item Static tracepoints probing the marker
10882 The list of static tracepoints attached to the marker.
10886 (@value{GDBP}) info static-tracepoint-markers
10887 Cnt ID Enb Address What
10888 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10889 Data: number1 %d number2 %d
10890 Probed by static tracepoints: #2
10891 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10897 @node Starting and Stopping Trace Experiments
10898 @subsection Starting and Stopping Trace Experiments
10901 @kindex tstart [ @var{notes} ]
10902 @cindex start a new trace experiment
10903 @cindex collected data discarded
10905 This command starts the trace experiment, and begins collecting data.
10906 It has the side effect of discarding all the data collected in the
10907 trace buffer during the previous trace experiment. If any arguments
10908 are supplied, they are taken as a note and stored with the trace
10909 experiment's state. The notes may be arbitrary text, and are
10910 especially useful with disconnected tracing in a multi-user context;
10911 the notes can explain what the trace is doing, supply user contact
10912 information, and so forth.
10914 @kindex tstop [ @var{notes} ]
10915 @cindex stop a running trace experiment
10917 This command stops the trace experiment. If any arguments are
10918 supplied, they are recorded with the experiment as a note. This is
10919 useful if you are stopping a trace started by someone else, for
10920 instance if the trace is interfering with the system's behavior and
10921 needs to be stopped quickly.
10923 @strong{Note}: a trace experiment and data collection may stop
10924 automatically if any tracepoint's passcount is reached
10925 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10928 @cindex status of trace data collection
10929 @cindex trace experiment, status of
10931 This command displays the status of the current trace data
10935 Here is an example of the commands we described so far:
10938 (@value{GDBP}) @b{trace gdb_c_test}
10939 (@value{GDBP}) @b{actions}
10940 Enter actions for tracepoint #1, one per line.
10941 > collect $regs,$locals,$args
10942 > while-stepping 11
10946 (@value{GDBP}) @b{tstart}
10947 [time passes @dots{}]
10948 (@value{GDBP}) @b{tstop}
10951 @anchor{disconnected tracing}
10952 @cindex disconnected tracing
10953 You can choose to continue running the trace experiment even if
10954 @value{GDBN} disconnects from the target, voluntarily or
10955 involuntarily. For commands such as @code{detach}, the debugger will
10956 ask what you want to do with the trace. But for unexpected
10957 terminations (@value{GDBN} crash, network outage), it would be
10958 unfortunate to lose hard-won trace data, so the variable
10959 @code{disconnected-tracing} lets you decide whether the trace should
10960 continue running without @value{GDBN}.
10963 @item set disconnected-tracing on
10964 @itemx set disconnected-tracing off
10965 @kindex set disconnected-tracing
10966 Choose whether a tracing run should continue to run if @value{GDBN}
10967 has disconnected from the target. Note that @code{detach} or
10968 @code{quit} will ask you directly what to do about a running trace no
10969 matter what this variable's setting, so the variable is mainly useful
10970 for handling unexpected situations, such as loss of the network.
10972 @item show disconnected-tracing
10973 @kindex show disconnected-tracing
10974 Show the current choice for disconnected tracing.
10978 When you reconnect to the target, the trace experiment may or may not
10979 still be running; it might have filled the trace buffer in the
10980 meantime, or stopped for one of the other reasons. If it is running,
10981 it will continue after reconnection.
10983 Upon reconnection, the target will upload information about the
10984 tracepoints in effect. @value{GDBN} will then compare that
10985 information to the set of tracepoints currently defined, and attempt
10986 to match them up, allowing for the possibility that the numbers may
10987 have changed due to creation and deletion in the meantime. If one of
10988 the target's tracepoints does not match any in @value{GDBN}, the
10989 debugger will create a new tracepoint, so that you have a number with
10990 which to specify that tracepoint. This matching-up process is
10991 necessarily heuristic, and it may result in useless tracepoints being
10992 created; you may simply delete them if they are of no use.
10994 @cindex circular trace buffer
10995 If your target agent supports a @dfn{circular trace buffer}, then you
10996 can run a trace experiment indefinitely without filling the trace
10997 buffer; when space runs out, the agent deletes already-collected trace
10998 frames, oldest first, until there is enough room to continue
10999 collecting. This is especially useful if your tracepoints are being
11000 hit too often, and your trace gets terminated prematurely because the
11001 buffer is full. To ask for a circular trace buffer, simply set
11002 @samp{circular-trace-buffer} to on. You can set this at any time,
11003 including during tracing; if the agent can do it, it will change
11004 buffer handling on the fly, otherwise it will not take effect until
11008 @item set circular-trace-buffer on
11009 @itemx set circular-trace-buffer off
11010 @kindex set circular-trace-buffer
11011 Choose whether a tracing run should use a linear or circular buffer
11012 for trace data. A linear buffer will not lose any trace data, but may
11013 fill up prematurely, while a circular buffer will discard old trace
11014 data, but it will have always room for the latest tracepoint hits.
11016 @item show circular-trace-buffer
11017 @kindex show circular-trace-buffer
11018 Show the current choice for the trace buffer. Note that this may not
11019 match the agent's current buffer handling, nor is it guaranteed to
11020 match the setting that might have been in effect during a past run,
11021 for instance if you are looking at frames from a trace file.
11026 @item set trace-user @var{text}
11027 @kindex set trace-user
11029 @item show trace-user
11030 @kindex show trace-user
11032 @item set trace-notes @var{text}
11033 @kindex set trace-notes
11034 Set the trace run's notes.
11036 @item show trace-notes
11037 @kindex show trace-notes
11038 Show the trace run's notes.
11040 @item set trace-stop-notes @var{text}
11041 @kindex set trace-stop-notes
11042 Set the trace run's stop notes. The handling of the note is as for
11043 @code{tstop} arguments; the set command is convenient way to fix a
11044 stop note that is mistaken or incomplete.
11046 @item show trace-stop-notes
11047 @kindex show trace-stop-notes
11048 Show the trace run's stop notes.
11052 @node Tracepoint Restrictions
11053 @subsection Tracepoint Restrictions
11055 @cindex tracepoint restrictions
11056 There are a number of restrictions on the use of tracepoints. As
11057 described above, tracepoint data gathering occurs on the target
11058 without interaction from @value{GDBN}. Thus the full capabilities of
11059 the debugger are not available during data gathering, and then at data
11060 examination time, you will be limited by only having what was
11061 collected. The following items describe some common problems, but it
11062 is not exhaustive, and you may run into additional difficulties not
11068 Tracepoint expressions are intended to gather objects (lvalues). Thus
11069 the full flexibility of GDB's expression evaluator is not available.
11070 You cannot call functions, cast objects to aggregate types, access
11071 convenience variables or modify values (except by assignment to trace
11072 state variables). Some language features may implicitly call
11073 functions (for instance Objective-C fields with accessors), and therefore
11074 cannot be collected either.
11077 Collection of local variables, either individually or in bulk with
11078 @code{$locals} or @code{$args}, during @code{while-stepping} may
11079 behave erratically. The stepping action may enter a new scope (for
11080 instance by stepping into a function), or the location of the variable
11081 may change (for instance it is loaded into a register). The
11082 tracepoint data recorded uses the location information for the
11083 variables that is correct for the tracepoint location. When the
11084 tracepoint is created, it is not possible, in general, to determine
11085 where the steps of a @code{while-stepping} sequence will advance the
11086 program---particularly if a conditional branch is stepped.
11089 Collection of an incompletely-initialized or partially-destroyed object
11090 may result in something that @value{GDBN} cannot display, or displays
11091 in a misleading way.
11094 When @value{GDBN} displays a pointer to character it automatically
11095 dereferences the pointer to also display characters of the string
11096 being pointed to. However, collecting the pointer during tracing does
11097 not automatically collect the string. You need to explicitly
11098 dereference the pointer and provide size information if you want to
11099 collect not only the pointer, but the memory pointed to. For example,
11100 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11104 It is not possible to collect a complete stack backtrace at a
11105 tracepoint. Instead, you may collect the registers and a few hundred
11106 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11107 (adjust to use the name of the actual stack pointer register on your
11108 target architecture, and the amount of stack you wish to capture).
11109 Then the @code{backtrace} command will show a partial backtrace when
11110 using a trace frame. The number of stack frames that can be examined
11111 depends on the sizes of the frames in the collected stack. Note that
11112 if you ask for a block so large that it goes past the bottom of the
11113 stack, the target agent may report an error trying to read from an
11117 If you do not collect registers at a tracepoint, @value{GDBN} can
11118 infer that the value of @code{$pc} must be the same as the address of
11119 the tracepoint and use that when you are looking at a trace frame
11120 for that tracepoint. However, this cannot work if the tracepoint has
11121 multiple locations (for instance if it was set in a function that was
11122 inlined), or if it has a @code{while-stepping} loop. In those cases
11123 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11128 @node Analyze Collected Data
11129 @section Using the Collected Data
11131 After the tracepoint experiment ends, you use @value{GDBN} commands
11132 for examining the trace data. The basic idea is that each tracepoint
11133 collects a trace @dfn{snapshot} every time it is hit and another
11134 snapshot every time it single-steps. All these snapshots are
11135 consecutively numbered from zero and go into a buffer, and you can
11136 examine them later. The way you examine them is to @dfn{focus} on a
11137 specific trace snapshot. When the remote stub is focused on a trace
11138 snapshot, it will respond to all @value{GDBN} requests for memory and
11139 registers by reading from the buffer which belongs to that snapshot,
11140 rather than from @emph{real} memory or registers of the program being
11141 debugged. This means that @strong{all} @value{GDBN} commands
11142 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11143 behave as if we were currently debugging the program state as it was
11144 when the tracepoint occurred. Any requests for data that are not in
11145 the buffer will fail.
11148 * tfind:: How to select a trace snapshot
11149 * tdump:: How to display all data for a snapshot
11150 * save tracepoints:: How to save tracepoints for a future run
11154 @subsection @code{tfind @var{n}}
11157 @cindex select trace snapshot
11158 @cindex find trace snapshot
11159 The basic command for selecting a trace snapshot from the buffer is
11160 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11161 counting from zero. If no argument @var{n} is given, the next
11162 snapshot is selected.
11164 Here are the various forms of using the @code{tfind} command.
11168 Find the first snapshot in the buffer. This is a synonym for
11169 @code{tfind 0} (since 0 is the number of the first snapshot).
11172 Stop debugging trace snapshots, resume @emph{live} debugging.
11175 Same as @samp{tfind none}.
11178 No argument means find the next trace snapshot.
11181 Find the previous trace snapshot before the current one. This permits
11182 retracing earlier steps.
11184 @item tfind tracepoint @var{num}
11185 Find the next snapshot associated with tracepoint @var{num}. Search
11186 proceeds forward from the last examined trace snapshot. If no
11187 argument @var{num} is given, it means find the next snapshot collected
11188 for the same tracepoint as the current snapshot.
11190 @item tfind pc @var{addr}
11191 Find the next snapshot associated with the value @var{addr} of the
11192 program counter. Search proceeds forward from the last examined trace
11193 snapshot. If no argument @var{addr} is given, it means find the next
11194 snapshot with the same value of PC as the current snapshot.
11196 @item tfind outside @var{addr1}, @var{addr2}
11197 Find the next snapshot whose PC is outside the given range of
11198 addresses (exclusive).
11200 @item tfind range @var{addr1}, @var{addr2}
11201 Find the next snapshot whose PC is between @var{addr1} and
11202 @var{addr2} (inclusive).
11204 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11205 Find the next snapshot associated with the source line @var{n}. If
11206 the optional argument @var{file} is given, refer to line @var{n} in
11207 that source file. Search proceeds forward from the last examined
11208 trace snapshot. If no argument @var{n} is given, it means find the
11209 next line other than the one currently being examined; thus saying
11210 @code{tfind line} repeatedly can appear to have the same effect as
11211 stepping from line to line in a @emph{live} debugging session.
11214 The default arguments for the @code{tfind} commands are specifically
11215 designed to make it easy to scan through the trace buffer. For
11216 instance, @code{tfind} with no argument selects the next trace
11217 snapshot, and @code{tfind -} with no argument selects the previous
11218 trace snapshot. So, by giving one @code{tfind} command, and then
11219 simply hitting @key{RET} repeatedly you can examine all the trace
11220 snapshots in order. Or, by saying @code{tfind -} and then hitting
11221 @key{RET} repeatedly you can examine the snapshots in reverse order.
11222 The @code{tfind line} command with no argument selects the snapshot
11223 for the next source line executed. The @code{tfind pc} command with
11224 no argument selects the next snapshot with the same program counter
11225 (PC) as the current frame. The @code{tfind tracepoint} command with
11226 no argument selects the next trace snapshot collected by the same
11227 tracepoint as the current one.
11229 In addition to letting you scan through the trace buffer manually,
11230 these commands make it easy to construct @value{GDBN} scripts that
11231 scan through the trace buffer and print out whatever collected data
11232 you are interested in. Thus, if we want to examine the PC, FP, and SP
11233 registers from each trace frame in the buffer, we can say this:
11236 (@value{GDBP}) @b{tfind start}
11237 (@value{GDBP}) @b{while ($trace_frame != -1)}
11238 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11239 $trace_frame, $pc, $sp, $fp
11243 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11244 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11245 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11246 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11247 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11248 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11249 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11250 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11251 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11252 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11253 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11256 Or, if we want to examine the variable @code{X} at each source line in
11260 (@value{GDBP}) @b{tfind start}
11261 (@value{GDBP}) @b{while ($trace_frame != -1)}
11262 > printf "Frame %d, X == %d\n", $trace_frame, X
11272 @subsection @code{tdump}
11274 @cindex dump all data collected at tracepoint
11275 @cindex tracepoint data, display
11277 This command takes no arguments. It prints all the data collected at
11278 the current trace snapshot.
11281 (@value{GDBP}) @b{trace 444}
11282 (@value{GDBP}) @b{actions}
11283 Enter actions for tracepoint #2, one per line:
11284 > collect $regs, $locals, $args, gdb_long_test
11287 (@value{GDBP}) @b{tstart}
11289 (@value{GDBP}) @b{tfind line 444}
11290 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11292 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11294 (@value{GDBP}) @b{tdump}
11295 Data collected at tracepoint 2, trace frame 1:
11296 d0 0xc4aa0085 -995491707
11300 d4 0x71aea3d 119204413
11303 d7 0x380035 3670069
11304 a0 0x19e24a 1696330
11305 a1 0x3000668 50333288
11307 a3 0x322000 3284992
11308 a4 0x3000698 50333336
11309 a5 0x1ad3cc 1758156
11310 fp 0x30bf3c 0x30bf3c
11311 sp 0x30bf34 0x30bf34
11313 pc 0x20b2c8 0x20b2c8
11317 p = 0x20e5b4 "gdb-test"
11324 gdb_long_test = 17 '\021'
11329 @code{tdump} works by scanning the tracepoint's current collection
11330 actions and printing the value of each expression listed. So
11331 @code{tdump} can fail, if after a run, you change the tracepoint's
11332 actions to mention variables that were not collected during the run.
11334 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11335 uses the collected value of @code{$pc} to distinguish between trace
11336 frames that were collected at the tracepoint hit, and frames that were
11337 collected while stepping. This allows it to correctly choose whether
11338 to display the basic list of collections, or the collections from the
11339 body of the while-stepping loop. However, if @code{$pc} was not collected,
11340 then @code{tdump} will always attempt to dump using the basic collection
11341 list, and may fail if a while-stepping frame does not include all the
11342 same data that is collected at the tracepoint hit.
11343 @c This is getting pretty arcane, example would be good.
11345 @node save tracepoints
11346 @subsection @code{save tracepoints @var{filename}}
11347 @kindex save tracepoints
11348 @kindex save-tracepoints
11349 @cindex save tracepoints for future sessions
11351 This command saves all current tracepoint definitions together with
11352 their actions and passcounts, into a file @file{@var{filename}}
11353 suitable for use in a later debugging session. To read the saved
11354 tracepoint definitions, use the @code{source} command (@pxref{Command
11355 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11356 alias for @w{@code{save tracepoints}}
11358 @node Tracepoint Variables
11359 @section Convenience Variables for Tracepoints
11360 @cindex tracepoint variables
11361 @cindex convenience variables for tracepoints
11364 @vindex $trace_frame
11365 @item (int) $trace_frame
11366 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11367 snapshot is selected.
11369 @vindex $tracepoint
11370 @item (int) $tracepoint
11371 The tracepoint for the current trace snapshot.
11373 @vindex $trace_line
11374 @item (int) $trace_line
11375 The line number for the current trace snapshot.
11377 @vindex $trace_file
11378 @item (char []) $trace_file
11379 The source file for the current trace snapshot.
11381 @vindex $trace_func
11382 @item (char []) $trace_func
11383 The name of the function containing @code{$tracepoint}.
11386 Note: @code{$trace_file} is not suitable for use in @code{printf},
11387 use @code{output} instead.
11389 Here's a simple example of using these convenience variables for
11390 stepping through all the trace snapshots and printing some of their
11391 data. Note that these are not the same as trace state variables,
11392 which are managed by the target.
11395 (@value{GDBP}) @b{tfind start}
11397 (@value{GDBP}) @b{while $trace_frame != -1}
11398 > output $trace_file
11399 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11405 @section Using Trace Files
11406 @cindex trace files
11408 In some situations, the target running a trace experiment may no
11409 longer be available; perhaps it crashed, or the hardware was needed
11410 for a different activity. To handle these cases, you can arrange to
11411 dump the trace data into a file, and later use that file as a source
11412 of trace data, via the @code{target tfile} command.
11417 @item tsave [ -r ] @var{filename}
11418 Save the trace data to @var{filename}. By default, this command
11419 assumes that @var{filename} refers to the host filesystem, so if
11420 necessary @value{GDBN} will copy raw trace data up from the target and
11421 then save it. If the target supports it, you can also supply the
11422 optional argument @code{-r} (``remote'') to direct the target to save
11423 the data directly into @var{filename} in its own filesystem, which may be
11424 more efficient if the trace buffer is very large. (Note, however, that
11425 @code{target tfile} can only read from files accessible to the host.)
11427 @kindex target tfile
11429 @item target tfile @var{filename}
11430 Use the file named @var{filename} as a source of trace data. Commands
11431 that examine data work as they do with a live target, but it is not
11432 possible to run any new trace experiments. @code{tstatus} will report
11433 the state of the trace run at the moment the data was saved, as well
11434 as the current trace frame you are examining. @var{filename} must be
11435 on a filesystem accessible to the host.
11440 @chapter Debugging Programs That Use Overlays
11443 If your program is too large to fit completely in your target system's
11444 memory, you can sometimes use @dfn{overlays} to work around this
11445 problem. @value{GDBN} provides some support for debugging programs that
11449 * How Overlays Work:: A general explanation of overlays.
11450 * Overlay Commands:: Managing overlays in @value{GDBN}.
11451 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11452 mapped by asking the inferior.
11453 * Overlay Sample Program:: A sample program using overlays.
11456 @node How Overlays Work
11457 @section How Overlays Work
11458 @cindex mapped overlays
11459 @cindex unmapped overlays
11460 @cindex load address, overlay's
11461 @cindex mapped address
11462 @cindex overlay area
11464 Suppose you have a computer whose instruction address space is only 64
11465 kilobytes long, but which has much more memory which can be accessed by
11466 other means: special instructions, segment registers, or memory
11467 management hardware, for example. Suppose further that you want to
11468 adapt a program which is larger than 64 kilobytes to run on this system.
11470 One solution is to identify modules of your program which are relatively
11471 independent, and need not call each other directly; call these modules
11472 @dfn{overlays}. Separate the overlays from the main program, and place
11473 their machine code in the larger memory. Place your main program in
11474 instruction memory, but leave at least enough space there to hold the
11475 largest overlay as well.
11477 Now, to call a function located in an overlay, you must first copy that
11478 overlay's machine code from the large memory into the space set aside
11479 for it in the instruction memory, and then jump to its entry point
11482 @c NB: In the below the mapped area's size is greater or equal to the
11483 @c size of all overlays. This is intentional to remind the developer
11484 @c that overlays don't necessarily need to be the same size.
11488 Data Instruction Larger
11489 Address Space Address Space Address Space
11490 +-----------+ +-----------+ +-----------+
11492 +-----------+ +-----------+ +-----------+<-- overlay 1
11493 | program | | main | .----| overlay 1 | load address
11494 | variables | | program | | +-----------+
11495 | and heap | | | | | |
11496 +-----------+ | | | +-----------+<-- overlay 2
11497 | | +-----------+ | | | load address
11498 +-----------+ | | | .-| overlay 2 |
11500 mapped --->+-----------+ | | +-----------+
11501 address | | | | | |
11502 | overlay | <-' | | |
11503 | area | <---' +-----------+<-- overlay 3
11504 | | <---. | | load address
11505 +-----------+ `--| overlay 3 |
11512 @anchor{A code overlay}A code overlay
11516 The diagram (@pxref{A code overlay}) shows a system with separate data
11517 and instruction address spaces. To map an overlay, the program copies
11518 its code from the larger address space to the instruction address space.
11519 Since the overlays shown here all use the same mapped address, only one
11520 may be mapped at a time. For a system with a single address space for
11521 data and instructions, the diagram would be similar, except that the
11522 program variables and heap would share an address space with the main
11523 program and the overlay area.
11525 An overlay loaded into instruction memory and ready for use is called a
11526 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11527 instruction memory. An overlay not present (or only partially present)
11528 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11529 is its address in the larger memory. The mapped address is also called
11530 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11531 called the @dfn{load memory address}, or @dfn{LMA}.
11533 Unfortunately, overlays are not a completely transparent way to adapt a
11534 program to limited instruction memory. They introduce a new set of
11535 global constraints you must keep in mind as you design your program:
11540 Before calling or returning to a function in an overlay, your program
11541 must make sure that overlay is actually mapped. Otherwise, the call or
11542 return will transfer control to the right address, but in the wrong
11543 overlay, and your program will probably crash.
11546 If the process of mapping an overlay is expensive on your system, you
11547 will need to choose your overlays carefully to minimize their effect on
11548 your program's performance.
11551 The executable file you load onto your system must contain each
11552 overlay's instructions, appearing at the overlay's load address, not its
11553 mapped address. However, each overlay's instructions must be relocated
11554 and its symbols defined as if the overlay were at its mapped address.
11555 You can use GNU linker scripts to specify different load and relocation
11556 addresses for pieces of your program; see @ref{Overlay Description,,,
11557 ld.info, Using ld: the GNU linker}.
11560 The procedure for loading executable files onto your system must be able
11561 to load their contents into the larger address space as well as the
11562 instruction and data spaces.
11566 The overlay system described above is rather simple, and could be
11567 improved in many ways:
11572 If your system has suitable bank switch registers or memory management
11573 hardware, you could use those facilities to make an overlay's load area
11574 contents simply appear at their mapped address in instruction space.
11575 This would probably be faster than copying the overlay to its mapped
11576 area in the usual way.
11579 If your overlays are small enough, you could set aside more than one
11580 overlay area, and have more than one overlay mapped at a time.
11583 You can use overlays to manage data, as well as instructions. In
11584 general, data overlays are even less transparent to your design than
11585 code overlays: whereas code overlays only require care when you call or
11586 return to functions, data overlays require care every time you access
11587 the data. Also, if you change the contents of a data overlay, you
11588 must copy its contents back out to its load address before you can copy a
11589 different data overlay into the same mapped area.
11594 @node Overlay Commands
11595 @section Overlay Commands
11597 To use @value{GDBN}'s overlay support, each overlay in your program must
11598 correspond to a separate section of the executable file. The section's
11599 virtual memory address and load memory address must be the overlay's
11600 mapped and load addresses. Identifying overlays with sections allows
11601 @value{GDBN} to determine the appropriate address of a function or
11602 variable, depending on whether the overlay is mapped or not.
11604 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11605 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11610 Disable @value{GDBN}'s overlay support. When overlay support is
11611 disabled, @value{GDBN} assumes that all functions and variables are
11612 always present at their mapped addresses. By default, @value{GDBN}'s
11613 overlay support is disabled.
11615 @item overlay manual
11616 @cindex manual overlay debugging
11617 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11618 relies on you to tell it which overlays are mapped, and which are not,
11619 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11620 commands described below.
11622 @item overlay map-overlay @var{overlay}
11623 @itemx overlay map @var{overlay}
11624 @cindex map an overlay
11625 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11626 be the name of the object file section containing the overlay. When an
11627 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11628 functions and variables at their mapped addresses. @value{GDBN} assumes
11629 that any other overlays whose mapped ranges overlap that of
11630 @var{overlay} are now unmapped.
11632 @item overlay unmap-overlay @var{overlay}
11633 @itemx overlay unmap @var{overlay}
11634 @cindex unmap an overlay
11635 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11636 must be the name of the object file section containing the overlay.
11637 When an overlay is unmapped, @value{GDBN} assumes it can find the
11638 overlay's functions and variables at their load addresses.
11641 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11642 consults a data structure the overlay manager maintains in the inferior
11643 to see which overlays are mapped. For details, see @ref{Automatic
11644 Overlay Debugging}.
11646 @item overlay load-target
11647 @itemx overlay load
11648 @cindex reloading the overlay table
11649 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11650 re-reads the table @value{GDBN} automatically each time the inferior
11651 stops, so this command should only be necessary if you have changed the
11652 overlay mapping yourself using @value{GDBN}. This command is only
11653 useful when using automatic overlay debugging.
11655 @item overlay list-overlays
11656 @itemx overlay list
11657 @cindex listing mapped overlays
11658 Display a list of the overlays currently mapped, along with their mapped
11659 addresses, load addresses, and sizes.
11663 Normally, when @value{GDBN} prints a code address, it includes the name
11664 of the function the address falls in:
11667 (@value{GDBP}) print main
11668 $3 = @{int ()@} 0x11a0 <main>
11671 When overlay debugging is enabled, @value{GDBN} recognizes code in
11672 unmapped overlays, and prints the names of unmapped functions with
11673 asterisks around them. For example, if @code{foo} is a function in an
11674 unmapped overlay, @value{GDBN} prints it this way:
11677 (@value{GDBP}) overlay list
11678 No sections are mapped.
11679 (@value{GDBP}) print foo
11680 $5 = @{int (int)@} 0x100000 <*foo*>
11683 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11687 (@value{GDBP}) overlay list
11688 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11689 mapped at 0x1016 - 0x104a
11690 (@value{GDBP}) print foo
11691 $6 = @{int (int)@} 0x1016 <foo>
11694 When overlay debugging is enabled, @value{GDBN} can find the correct
11695 address for functions and variables in an overlay, whether or not the
11696 overlay is mapped. This allows most @value{GDBN} commands, like
11697 @code{break} and @code{disassemble}, to work normally, even on unmapped
11698 code. However, @value{GDBN}'s breakpoint support has some limitations:
11702 @cindex breakpoints in overlays
11703 @cindex overlays, setting breakpoints in
11704 You can set breakpoints in functions in unmapped overlays, as long as
11705 @value{GDBN} can write to the overlay at its load address.
11707 @value{GDBN} can not set hardware or simulator-based breakpoints in
11708 unmapped overlays. However, if you set a breakpoint at the end of your
11709 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11710 you are using manual overlay management), @value{GDBN} will re-set its
11711 breakpoints properly.
11715 @node Automatic Overlay Debugging
11716 @section Automatic Overlay Debugging
11717 @cindex automatic overlay debugging
11719 @value{GDBN} can automatically track which overlays are mapped and which
11720 are not, given some simple co-operation from the overlay manager in the
11721 inferior. If you enable automatic overlay debugging with the
11722 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11723 looks in the inferior's memory for certain variables describing the
11724 current state of the overlays.
11726 Here are the variables your overlay manager must define to support
11727 @value{GDBN}'s automatic overlay debugging:
11731 @item @code{_ovly_table}:
11732 This variable must be an array of the following structures:
11737 /* The overlay's mapped address. */
11740 /* The size of the overlay, in bytes. */
11741 unsigned long size;
11743 /* The overlay's load address. */
11746 /* Non-zero if the overlay is currently mapped;
11748 unsigned long mapped;
11752 @item @code{_novlys}:
11753 This variable must be a four-byte signed integer, holding the total
11754 number of elements in @code{_ovly_table}.
11758 To decide whether a particular overlay is mapped or not, @value{GDBN}
11759 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11760 @code{lma} members equal the VMA and LMA of the overlay's section in the
11761 executable file. When @value{GDBN} finds a matching entry, it consults
11762 the entry's @code{mapped} member to determine whether the overlay is
11765 In addition, your overlay manager may define a function called
11766 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11767 will silently set a breakpoint there. If the overlay manager then
11768 calls this function whenever it has changed the overlay table, this
11769 will enable @value{GDBN} to accurately keep track of which overlays
11770 are in program memory, and update any breakpoints that may be set
11771 in overlays. This will allow breakpoints to work even if the
11772 overlays are kept in ROM or other non-writable memory while they
11773 are not being executed.
11775 @node Overlay Sample Program
11776 @section Overlay Sample Program
11777 @cindex overlay example program
11779 When linking a program which uses overlays, you must place the overlays
11780 at their load addresses, while relocating them to run at their mapped
11781 addresses. To do this, you must write a linker script (@pxref{Overlay
11782 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11783 since linker scripts are specific to a particular host system, target
11784 architecture, and target memory layout, this manual cannot provide
11785 portable sample code demonstrating @value{GDBN}'s overlay support.
11787 However, the @value{GDBN} source distribution does contain an overlaid
11788 program, with linker scripts for a few systems, as part of its test
11789 suite. The program consists of the following files from
11790 @file{gdb/testsuite/gdb.base}:
11794 The main program file.
11796 A simple overlay manager, used by @file{overlays.c}.
11801 Overlay modules, loaded and used by @file{overlays.c}.
11804 Linker scripts for linking the test program on the @code{d10v-elf}
11805 and @code{m32r-elf} targets.
11808 You can build the test program using the @code{d10v-elf} GCC
11809 cross-compiler like this:
11812 $ d10v-elf-gcc -g -c overlays.c
11813 $ d10v-elf-gcc -g -c ovlymgr.c
11814 $ d10v-elf-gcc -g -c foo.c
11815 $ d10v-elf-gcc -g -c bar.c
11816 $ d10v-elf-gcc -g -c baz.c
11817 $ d10v-elf-gcc -g -c grbx.c
11818 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11819 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11822 The build process is identical for any other architecture, except that
11823 you must substitute the appropriate compiler and linker script for the
11824 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11828 @chapter Using @value{GDBN} with Different Languages
11831 Although programming languages generally have common aspects, they are
11832 rarely expressed in the same manner. For instance, in ANSI C,
11833 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11834 Modula-2, it is accomplished by @code{p^}. Values can also be
11835 represented (and displayed) differently. Hex numbers in C appear as
11836 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11838 @cindex working language
11839 Language-specific information is built into @value{GDBN} for some languages,
11840 allowing you to express operations like the above in your program's
11841 native language, and allowing @value{GDBN} to output values in a manner
11842 consistent with the syntax of your program's native language. The
11843 language you use to build expressions is called the @dfn{working
11847 * Setting:: Switching between source languages
11848 * Show:: Displaying the language
11849 * Checks:: Type and range checks
11850 * Supported Languages:: Supported languages
11851 * Unsupported Languages:: Unsupported languages
11855 @section Switching Between Source Languages
11857 There are two ways to control the working language---either have @value{GDBN}
11858 set it automatically, or select it manually yourself. You can use the
11859 @code{set language} command for either purpose. On startup, @value{GDBN}
11860 defaults to setting the language automatically. The working language is
11861 used to determine how expressions you type are interpreted, how values
11864 In addition to the working language, every source file that
11865 @value{GDBN} knows about has its own working language. For some object
11866 file formats, the compiler might indicate which language a particular
11867 source file is in. However, most of the time @value{GDBN} infers the
11868 language from the name of the file. The language of a source file
11869 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11870 show each frame appropriately for its own language. There is no way to
11871 set the language of a source file from within @value{GDBN}, but you can
11872 set the language associated with a filename extension. @xref{Show, ,
11873 Displaying the Language}.
11875 This is most commonly a problem when you use a program, such
11876 as @code{cfront} or @code{f2c}, that generates C but is written in
11877 another language. In that case, make the
11878 program use @code{#line} directives in its C output; that way
11879 @value{GDBN} will know the correct language of the source code of the original
11880 program, and will display that source code, not the generated C code.
11883 * Filenames:: Filename extensions and languages.
11884 * Manually:: Setting the working language manually
11885 * Automatically:: Having @value{GDBN} infer the source language
11889 @subsection List of Filename Extensions and Languages
11891 If a source file name ends in one of the following extensions, then
11892 @value{GDBN} infers that its language is the one indicated.
11910 C@t{++} source file
11916 Objective-C source file
11920 Fortran source file
11923 Modula-2 source file
11927 Assembler source file. This actually behaves almost like C, but
11928 @value{GDBN} does not skip over function prologues when stepping.
11931 In addition, you may set the language associated with a filename
11932 extension. @xref{Show, , Displaying the Language}.
11935 @subsection Setting the Working Language
11937 If you allow @value{GDBN} to set the language automatically,
11938 expressions are interpreted the same way in your debugging session and
11941 @kindex set language
11942 If you wish, you may set the language manually. To do this, issue the
11943 command @samp{set language @var{lang}}, where @var{lang} is the name of
11944 a language, such as
11945 @code{c} or @code{modula-2}.
11946 For a list of the supported languages, type @samp{set language}.
11948 Setting the language manually prevents @value{GDBN} from updating the working
11949 language automatically. This can lead to confusion if you try
11950 to debug a program when the working language is not the same as the
11951 source language, when an expression is acceptable to both
11952 languages---but means different things. For instance, if the current
11953 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11961 might not have the effect you intended. In C, this means to add
11962 @code{b} and @code{c} and place the result in @code{a}. The result
11963 printed would be the value of @code{a}. In Modula-2, this means to compare
11964 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11966 @node Automatically
11967 @subsection Having @value{GDBN} Infer the Source Language
11969 To have @value{GDBN} set the working language automatically, use
11970 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11971 then infers the working language. That is, when your program stops in a
11972 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11973 working language to the language recorded for the function in that
11974 frame. If the language for a frame is unknown (that is, if the function
11975 or block corresponding to the frame was defined in a source file that
11976 does not have a recognized extension), the current working language is
11977 not changed, and @value{GDBN} issues a warning.
11979 This may not seem necessary for most programs, which are written
11980 entirely in one source language. However, program modules and libraries
11981 written in one source language can be used by a main program written in
11982 a different source language. Using @samp{set language auto} in this
11983 case frees you from having to set the working language manually.
11986 @section Displaying the Language
11988 The following commands help you find out which language is the
11989 working language, and also what language source files were written in.
11992 @item show language
11993 @kindex show language
11994 Display the current working language. This is the
11995 language you can use with commands such as @code{print} to
11996 build and compute expressions that may involve variables in your program.
11999 @kindex info frame@r{, show the source language}
12000 Display the source language for this frame. This language becomes the
12001 working language if you use an identifier from this frame.
12002 @xref{Frame Info, ,Information about a Frame}, to identify the other
12003 information listed here.
12006 @kindex info source@r{, show the source language}
12007 Display the source language of this source file.
12008 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12009 information listed here.
12012 In unusual circumstances, you may have source files with extensions
12013 not in the standard list. You can then set the extension associated
12014 with a language explicitly:
12017 @item set extension-language @var{ext} @var{language}
12018 @kindex set extension-language
12019 Tell @value{GDBN} that source files with extension @var{ext} are to be
12020 assumed as written in the source language @var{language}.
12022 @item info extensions
12023 @kindex info extensions
12024 List all the filename extensions and the associated languages.
12028 @section Type and Range Checking
12031 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12032 checking are included, but they do not yet have any effect. This
12033 section documents the intended facilities.
12035 @c FIXME remove warning when type/range code added
12037 Some languages are designed to guard you against making seemingly common
12038 errors through a series of compile- and run-time checks. These include
12039 checking the type of arguments to functions and operators, and making
12040 sure mathematical overflows are caught at run time. Checks such as
12041 these help to ensure a program's correctness once it has been compiled
12042 by eliminating type mismatches, and providing active checks for range
12043 errors when your program is running.
12045 @value{GDBN} can check for conditions like the above if you wish.
12046 Although @value{GDBN} does not check the statements in your program,
12047 it can check expressions entered directly into @value{GDBN} for
12048 evaluation via the @code{print} command, for example. As with the
12049 working language, @value{GDBN} can also decide whether or not to check
12050 automatically based on your program's source language.
12051 @xref{Supported Languages, ,Supported Languages}, for the default
12052 settings of supported languages.
12055 * Type Checking:: An overview of type checking
12056 * Range Checking:: An overview of range checking
12059 @cindex type checking
12060 @cindex checks, type
12061 @node Type Checking
12062 @subsection An Overview of Type Checking
12064 Some languages, such as Modula-2, are strongly typed, meaning that the
12065 arguments to operators and functions have to be of the correct type,
12066 otherwise an error occurs. These checks prevent type mismatch
12067 errors from ever causing any run-time problems. For example,
12075 The second example fails because the @code{CARDINAL} 1 is not
12076 type-compatible with the @code{REAL} 2.3.
12078 For the expressions you use in @value{GDBN} commands, you can tell the
12079 @value{GDBN} type checker to skip checking;
12080 to treat any mismatches as errors and abandon the expression;
12081 or to only issue warnings when type mismatches occur,
12082 but evaluate the expression anyway. When you choose the last of
12083 these, @value{GDBN} evaluates expressions like the second example above, but
12084 also issues a warning.
12086 Even if you turn type checking off, there may be other reasons
12087 related to type that prevent @value{GDBN} from evaluating an expression.
12088 For instance, @value{GDBN} does not know how to add an @code{int} and
12089 a @code{struct foo}. These particular type errors have nothing to do
12090 with the language in use, and usually arise from expressions, such as
12091 the one described above, which make little sense to evaluate anyway.
12093 Each language defines to what degree it is strict about type. For
12094 instance, both Modula-2 and C require the arguments to arithmetical
12095 operators to be numbers. In C, enumerated types and pointers can be
12096 represented as numbers, so that they are valid arguments to mathematical
12097 operators. @xref{Supported Languages, ,Supported Languages}, for further
12098 details on specific languages.
12100 @value{GDBN} provides some additional commands for controlling the type checker:
12102 @kindex set check type
12103 @kindex show check type
12105 @item set check type auto
12106 Set type checking on or off based on the current working language.
12107 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12110 @item set check type on
12111 @itemx set check type off
12112 Set type checking on or off, overriding the default setting for the
12113 current working language. Issue a warning if the setting does not
12114 match the language default. If any type mismatches occur in
12115 evaluating an expression while type checking is on, @value{GDBN} prints a
12116 message and aborts evaluation of the expression.
12118 @item set check type warn
12119 Cause the type checker to issue warnings, but to always attempt to
12120 evaluate the expression. Evaluating the expression may still
12121 be impossible for other reasons. For example, @value{GDBN} cannot add
12122 numbers and structures.
12125 Show the current setting of the type checker, and whether or not @value{GDBN}
12126 is setting it automatically.
12129 @cindex range checking
12130 @cindex checks, range
12131 @node Range Checking
12132 @subsection An Overview of Range Checking
12134 In some languages (such as Modula-2), it is an error to exceed the
12135 bounds of a type; this is enforced with run-time checks. Such range
12136 checking is meant to ensure program correctness by making sure
12137 computations do not overflow, or indices on an array element access do
12138 not exceed the bounds of the array.
12140 For expressions you use in @value{GDBN} commands, you can tell
12141 @value{GDBN} to treat range errors in one of three ways: ignore them,
12142 always treat them as errors and abandon the expression, or issue
12143 warnings but evaluate the expression anyway.
12145 A range error can result from numerical overflow, from exceeding an
12146 array index bound, or when you type a constant that is not a member
12147 of any type. Some languages, however, do not treat overflows as an
12148 error. In many implementations of C, mathematical overflow causes the
12149 result to ``wrap around'' to lower values---for example, if @var{m} is
12150 the largest integer value, and @var{s} is the smallest, then
12153 @var{m} + 1 @result{} @var{s}
12156 This, too, is specific to individual languages, and in some cases
12157 specific to individual compilers or machines. @xref{Supported Languages, ,
12158 Supported Languages}, for further details on specific languages.
12160 @value{GDBN} provides some additional commands for controlling the range checker:
12162 @kindex set check range
12163 @kindex show check range
12165 @item set check range auto
12166 Set range checking on or off based on the current working language.
12167 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12170 @item set check range on
12171 @itemx set check range off
12172 Set range checking on or off, overriding the default setting for the
12173 current working language. A warning is issued if the setting does not
12174 match the language default. If a range error occurs and range checking is on,
12175 then a message is printed and evaluation of the expression is aborted.
12177 @item set check range warn
12178 Output messages when the @value{GDBN} range checker detects a range error,
12179 but attempt to evaluate the expression anyway. Evaluating the
12180 expression may still be impossible for other reasons, such as accessing
12181 memory that the process does not own (a typical example from many Unix
12185 Show the current setting of the range checker, and whether or not it is
12186 being set automatically by @value{GDBN}.
12189 @node Supported Languages
12190 @section Supported Languages
12192 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12193 assembly, Modula-2, and Ada.
12194 @c This is false ...
12195 Some @value{GDBN} features may be used in expressions regardless of the
12196 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12197 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12198 ,Expressions}) can be used with the constructs of any supported
12201 The following sections detail to what degree each source language is
12202 supported by @value{GDBN}. These sections are not meant to be language
12203 tutorials or references, but serve only as a reference guide to what the
12204 @value{GDBN} expression parser accepts, and what input and output
12205 formats should look like for different languages. There are many good
12206 books written on each of these languages; please look to these for a
12207 language reference or tutorial.
12210 * C:: C and C@t{++}
12212 * Objective-C:: Objective-C
12213 * OpenCL C:: OpenCL C
12214 * Fortran:: Fortran
12216 * Modula-2:: Modula-2
12221 @subsection C and C@t{++}
12223 @cindex C and C@t{++}
12224 @cindex expressions in C or C@t{++}
12226 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12227 to both languages. Whenever this is the case, we discuss those languages
12231 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12232 @cindex @sc{gnu} C@t{++}
12233 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12234 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12235 effectively, you must compile your C@t{++} programs with a supported
12236 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12237 compiler (@code{aCC}).
12240 * C Operators:: C and C@t{++} operators
12241 * C Constants:: C and C@t{++} constants
12242 * C Plus Plus Expressions:: C@t{++} expressions
12243 * C Defaults:: Default settings for C and C@t{++}
12244 * C Checks:: C and C@t{++} type and range checks
12245 * Debugging C:: @value{GDBN} and C
12246 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12247 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12251 @subsubsection C and C@t{++} Operators
12253 @cindex C and C@t{++} operators
12255 Operators must be defined on values of specific types. For instance,
12256 @code{+} is defined on numbers, but not on structures. Operators are
12257 often defined on groups of types.
12259 For the purposes of C and C@t{++}, the following definitions hold:
12264 @emph{Integral types} include @code{int} with any of its storage-class
12265 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12268 @emph{Floating-point types} include @code{float}, @code{double}, and
12269 @code{long double} (if supported by the target platform).
12272 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12275 @emph{Scalar types} include all of the above.
12280 The following operators are supported. They are listed here
12281 in order of increasing precedence:
12285 The comma or sequencing operator. Expressions in a comma-separated list
12286 are evaluated from left to right, with the result of the entire
12287 expression being the last expression evaluated.
12290 Assignment. The value of an assignment expression is the value
12291 assigned. Defined on scalar types.
12294 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12295 and translated to @w{@code{@var{a} = @var{a op b}}}.
12296 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12297 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12298 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12301 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12302 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12306 Logical @sc{or}. Defined on integral types.
12309 Logical @sc{and}. Defined on integral types.
12312 Bitwise @sc{or}. Defined on integral types.
12315 Bitwise exclusive-@sc{or}. Defined on integral types.
12318 Bitwise @sc{and}. Defined on integral types.
12321 Equality and inequality. Defined on scalar types. The value of these
12322 expressions is 0 for false and non-zero for true.
12324 @item <@r{, }>@r{, }<=@r{, }>=
12325 Less than, greater than, less than or equal, greater than or equal.
12326 Defined on scalar types. The value of these expressions is 0 for false
12327 and non-zero for true.
12330 left shift, and right shift. Defined on integral types.
12333 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12336 Addition and subtraction. Defined on integral types, floating-point types and
12339 @item *@r{, }/@r{, }%
12340 Multiplication, division, and modulus. Multiplication and division are
12341 defined on integral and floating-point types. Modulus is defined on
12345 Increment and decrement. When appearing before a variable, the
12346 operation is performed before the variable is used in an expression;
12347 when appearing after it, the variable's value is used before the
12348 operation takes place.
12351 Pointer dereferencing. Defined on pointer types. Same precedence as
12355 Address operator. Defined on variables. Same precedence as @code{++}.
12357 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12358 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12359 to examine the address
12360 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12364 Negative. Defined on integral and floating-point types. Same
12365 precedence as @code{++}.
12368 Logical negation. Defined on integral types. Same precedence as
12372 Bitwise complement operator. Defined on integral types. Same precedence as
12377 Structure member, and pointer-to-structure member. For convenience,
12378 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12379 pointer based on the stored type information.
12380 Defined on @code{struct} and @code{union} data.
12383 Dereferences of pointers to members.
12386 Array indexing. @code{@var{a}[@var{i}]} is defined as
12387 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12390 Function parameter list. Same precedence as @code{->}.
12393 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12394 and @code{class} types.
12397 Doubled colons also represent the @value{GDBN} scope operator
12398 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12402 If an operator is redefined in the user code, @value{GDBN} usually
12403 attempts to invoke the redefined version instead of using the operator's
12404 predefined meaning.
12407 @subsubsection C and C@t{++} Constants
12409 @cindex C and C@t{++} constants
12411 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12416 Integer constants are a sequence of digits. Octal constants are
12417 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12418 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12419 @samp{l}, specifying that the constant should be treated as a
12423 Floating point constants are a sequence of digits, followed by a decimal
12424 point, followed by a sequence of digits, and optionally followed by an
12425 exponent. An exponent is of the form:
12426 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12427 sequence of digits. The @samp{+} is optional for positive exponents.
12428 A floating-point constant may also end with a letter @samp{f} or
12429 @samp{F}, specifying that the constant should be treated as being of
12430 the @code{float} (as opposed to the default @code{double}) type; or with
12431 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12435 Enumerated constants consist of enumerated identifiers, or their
12436 integral equivalents.
12439 Character constants are a single character surrounded by single quotes
12440 (@code{'}), or a number---the ordinal value of the corresponding character
12441 (usually its @sc{ascii} value). Within quotes, the single character may
12442 be represented by a letter or by @dfn{escape sequences}, which are of
12443 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12444 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12445 @samp{@var{x}} is a predefined special character---for example,
12446 @samp{\n} for newline.
12448 Wide character constants can be written by prefixing a character
12449 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12450 form of @samp{x}. The target wide character set is used when
12451 computing the value of this constant (@pxref{Character Sets}).
12454 String constants are a sequence of character constants surrounded by
12455 double quotes (@code{"}). Any valid character constant (as described
12456 above) may appear. Double quotes within the string must be preceded by
12457 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12460 Wide string constants can be written by prefixing a string constant
12461 with @samp{L}, as in C. The target wide character set is used when
12462 computing the value of this constant (@pxref{Character Sets}).
12465 Pointer constants are an integral value. You can also write pointers
12466 to constants using the C operator @samp{&}.
12469 Array constants are comma-separated lists surrounded by braces @samp{@{}
12470 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12471 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12472 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12475 @node C Plus Plus Expressions
12476 @subsubsection C@t{++} Expressions
12478 @cindex expressions in C@t{++}
12479 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12481 @cindex debugging C@t{++} programs
12482 @cindex C@t{++} compilers
12483 @cindex debug formats and C@t{++}
12484 @cindex @value{NGCC} and C@t{++}
12486 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12487 the proper compiler and the proper debug format. Currently,
12488 @value{GDBN} works best when debugging C@t{++} code that is compiled
12489 with the most recent version of @value{NGCC} possible. The DWARF
12490 debugging format is preferred; @value{NGCC} defaults to this on most
12491 popular platforms. Other compilers and/or debug formats are likely to
12492 work badly or not at all when using @value{GDBN} to debug C@t{++}
12493 code. @xref{Compilation}.
12498 @cindex member functions
12500 Member function calls are allowed; you can use expressions like
12503 count = aml->GetOriginal(x, y)
12506 @vindex this@r{, inside C@t{++} member functions}
12507 @cindex namespace in C@t{++}
12509 While a member function is active (in the selected stack frame), your
12510 expressions have the same namespace available as the member function;
12511 that is, @value{GDBN} allows implicit references to the class instance
12512 pointer @code{this} following the same rules as C@t{++}. @code{using}
12513 declarations in the current scope are also respected by @value{GDBN}.
12515 @cindex call overloaded functions
12516 @cindex overloaded functions, calling
12517 @cindex type conversions in C@t{++}
12519 You can call overloaded functions; @value{GDBN} resolves the function
12520 call to the right definition, with some restrictions. @value{GDBN} does not
12521 perform overload resolution involving user-defined type conversions,
12522 calls to constructors, or instantiations of templates that do not exist
12523 in the program. It also cannot handle ellipsis argument lists or
12526 It does perform integral conversions and promotions, floating-point
12527 promotions, arithmetic conversions, pointer conversions, conversions of
12528 class objects to base classes, and standard conversions such as those of
12529 functions or arrays to pointers; it requires an exact match on the
12530 number of function arguments.
12532 Overload resolution is always performed, unless you have specified
12533 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12534 ,@value{GDBN} Features for C@t{++}}.
12536 You must specify @code{set overload-resolution off} in order to use an
12537 explicit function signature to call an overloaded function, as in
12539 p 'foo(char,int)'('x', 13)
12542 The @value{GDBN} command-completion facility can simplify this;
12543 see @ref{Completion, ,Command Completion}.
12545 @cindex reference declarations
12547 @value{GDBN} understands variables declared as C@t{++} references; you can use
12548 them in expressions just as you do in C@t{++} source---they are automatically
12551 In the parameter list shown when @value{GDBN} displays a frame, the values of
12552 reference variables are not displayed (unlike other variables); this
12553 avoids clutter, since references are often used for large structures.
12554 The @emph{address} of a reference variable is always shown, unless
12555 you have specified @samp{set print address off}.
12558 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12559 expressions can use it just as expressions in your program do. Since
12560 one scope may be defined in another, you can use @code{::} repeatedly if
12561 necessary, for example in an expression like
12562 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12563 resolving name scope by reference to source files, in both C and C@t{++}
12564 debugging (@pxref{Variables, ,Program Variables}).
12567 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12572 @subsubsection C and C@t{++} Defaults
12574 @cindex C and C@t{++} defaults
12576 If you allow @value{GDBN} to set type and range checking automatically, they
12577 both default to @code{off} whenever the working language changes to
12578 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12579 selects the working language.
12581 If you allow @value{GDBN} to set the language automatically, it
12582 recognizes source files whose names end with @file{.c}, @file{.C}, or
12583 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12584 these files, it sets the working language to C or C@t{++}.
12585 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12586 for further details.
12588 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12589 @c unimplemented. If (b) changes, it might make sense to let this node
12590 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12593 @subsubsection C and C@t{++} Type and Range Checks
12595 @cindex C and C@t{++} checks
12597 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12598 is not used. However, if you turn type checking on, @value{GDBN}
12599 considers two variables type equivalent if:
12603 The two variables are structured and have the same structure, union, or
12607 The two variables have the same type name, or types that have been
12608 declared equivalent through @code{typedef}.
12611 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12614 The two @code{struct}, @code{union}, or @code{enum} variables are
12615 declared in the same declaration. (Note: this may not be true for all C
12620 Range checking, if turned on, is done on mathematical operations. Array
12621 indices are not checked, since they are often used to index a pointer
12622 that is not itself an array.
12625 @subsubsection @value{GDBN} and C
12627 The @code{set print union} and @code{show print union} commands apply to
12628 the @code{union} type. When set to @samp{on}, any @code{union} that is
12629 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12630 appears as @samp{@{...@}}.
12632 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12633 with pointers and a memory allocation function. @xref{Expressions,
12636 @node Debugging C Plus Plus
12637 @subsubsection @value{GDBN} Features for C@t{++}
12639 @cindex commands for C@t{++}
12641 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12642 designed specifically for use with C@t{++}. Here is a summary:
12645 @cindex break in overloaded functions
12646 @item @r{breakpoint menus}
12647 When you want a breakpoint in a function whose name is overloaded,
12648 @value{GDBN} has the capability to display a menu of possible breakpoint
12649 locations to help you specify which function definition you want.
12650 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12652 @cindex overloading in C@t{++}
12653 @item rbreak @var{regex}
12654 Setting breakpoints using regular expressions is helpful for setting
12655 breakpoints on overloaded functions that are not members of any special
12657 @xref{Set Breaks, ,Setting Breakpoints}.
12659 @cindex C@t{++} exception handling
12662 Debug C@t{++} exception handling using these commands. @xref{Set
12663 Catchpoints, , Setting Catchpoints}.
12665 @cindex inheritance
12666 @item ptype @var{typename}
12667 Print inheritance relationships as well as other information for type
12669 @xref{Symbols, ,Examining the Symbol Table}.
12671 @cindex C@t{++} symbol display
12672 @item set print demangle
12673 @itemx show print demangle
12674 @itemx set print asm-demangle
12675 @itemx show print asm-demangle
12676 Control whether C@t{++} symbols display in their source form, both when
12677 displaying code as C@t{++} source and when displaying disassemblies.
12678 @xref{Print Settings, ,Print Settings}.
12680 @item set print object
12681 @itemx show print object
12682 Choose whether to print derived (actual) or declared types of objects.
12683 @xref{Print Settings, ,Print Settings}.
12685 @item set print vtbl
12686 @itemx show print vtbl
12687 Control the format for printing virtual function tables.
12688 @xref{Print Settings, ,Print Settings}.
12689 (The @code{vtbl} commands do not work on programs compiled with the HP
12690 ANSI C@t{++} compiler (@code{aCC}).)
12692 @kindex set overload-resolution
12693 @cindex overloaded functions, overload resolution
12694 @item set overload-resolution on
12695 Enable overload resolution for C@t{++} expression evaluation. The default
12696 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12697 and searches for a function whose signature matches the argument types,
12698 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12699 Expressions, ,C@t{++} Expressions}, for details).
12700 If it cannot find a match, it emits a message.
12702 @item set overload-resolution off
12703 Disable overload resolution for C@t{++} expression evaluation. For
12704 overloaded functions that are not class member functions, @value{GDBN}
12705 chooses the first function of the specified name that it finds in the
12706 symbol table, whether or not its arguments are of the correct type. For
12707 overloaded functions that are class member functions, @value{GDBN}
12708 searches for a function whose signature @emph{exactly} matches the
12711 @kindex show overload-resolution
12712 @item show overload-resolution
12713 Show the current setting of overload resolution.
12715 @item @r{Overloaded symbol names}
12716 You can specify a particular definition of an overloaded symbol, using
12717 the same notation that is used to declare such symbols in C@t{++}: type
12718 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12719 also use the @value{GDBN} command-line word completion facilities to list the
12720 available choices, or to finish the type list for you.
12721 @xref{Completion,, Command Completion}, for details on how to do this.
12724 @node Decimal Floating Point
12725 @subsubsection Decimal Floating Point format
12726 @cindex decimal floating point format
12728 @value{GDBN} can examine, set and perform computations with numbers in
12729 decimal floating point format, which in the C language correspond to the
12730 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12731 specified by the extension to support decimal floating-point arithmetic.
12733 There are two encodings in use, depending on the architecture: BID (Binary
12734 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12735 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12738 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12739 to manipulate decimal floating point numbers, it is not possible to convert
12740 (using a cast, for example) integers wider than 32-bit to decimal float.
12742 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12743 point computations, error checking in decimal float operations ignores
12744 underflow, overflow and divide by zero exceptions.
12746 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12747 to inspect @code{_Decimal128} values stored in floating point registers.
12748 See @ref{PowerPC,,PowerPC} for more details.
12754 @value{GDBN} can be used to debug programs written in D and compiled with
12755 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12756 specific feature --- dynamic arrays.
12759 @subsection Objective-C
12761 @cindex Objective-C
12762 This section provides information about some commands and command
12763 options that are useful for debugging Objective-C code. See also
12764 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12765 few more commands specific to Objective-C support.
12768 * Method Names in Commands::
12769 * The Print Command with Objective-C::
12772 @node Method Names in Commands
12773 @subsubsection Method Names in Commands
12775 The following commands have been extended to accept Objective-C method
12776 names as line specifications:
12778 @kindex clear@r{, and Objective-C}
12779 @kindex break@r{, and Objective-C}
12780 @kindex info line@r{, and Objective-C}
12781 @kindex jump@r{, and Objective-C}
12782 @kindex list@r{, and Objective-C}
12786 @item @code{info line}
12791 A fully qualified Objective-C method name is specified as
12794 -[@var{Class} @var{methodName}]
12797 where the minus sign is used to indicate an instance method and a
12798 plus sign (not shown) is used to indicate a class method. The class
12799 name @var{Class} and method name @var{methodName} are enclosed in
12800 brackets, similar to the way messages are specified in Objective-C
12801 source code. For example, to set a breakpoint at the @code{create}
12802 instance method of class @code{Fruit} in the program currently being
12806 break -[Fruit create]
12809 To list ten program lines around the @code{initialize} class method,
12813 list +[NSText initialize]
12816 In the current version of @value{GDBN}, the plus or minus sign is
12817 required. In future versions of @value{GDBN}, the plus or minus
12818 sign will be optional, but you can use it to narrow the search. It
12819 is also possible to specify just a method name:
12825 You must specify the complete method name, including any colons. If
12826 your program's source files contain more than one @code{create} method,
12827 you'll be presented with a numbered list of classes that implement that
12828 method. Indicate your choice by number, or type @samp{0} to exit if
12831 As another example, to clear a breakpoint established at the
12832 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12835 clear -[NSWindow makeKeyAndOrderFront:]
12838 @node The Print Command with Objective-C
12839 @subsubsection The Print Command With Objective-C
12840 @cindex Objective-C, print objects
12841 @kindex print-object
12842 @kindex po @r{(@code{print-object})}
12844 The print command has also been extended to accept methods. For example:
12847 print -[@var{object} hash]
12850 @cindex print an Objective-C object description
12851 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12853 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12854 and print the result. Also, an additional command has been added,
12855 @code{print-object} or @code{po} for short, which is meant to print
12856 the description of an object. However, this command may only work
12857 with certain Objective-C libraries that have a particular hook
12858 function, @code{_NSPrintForDebugger}, defined.
12861 @subsection OpenCL C
12864 This section provides information about @value{GDBN}s OpenCL C support.
12867 * OpenCL C Datatypes::
12868 * OpenCL C Expressions::
12869 * OpenCL C Operators::
12872 @node OpenCL C Datatypes
12873 @subsubsection OpenCL C Datatypes
12875 @cindex OpenCL C Datatypes
12876 @value{GDBN} supports the builtin scalar and vector datatypes specified
12877 by OpenCL 1.1. In addition the half- and double-precision floating point
12878 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12879 extensions are also known to @value{GDBN}.
12881 @node OpenCL C Expressions
12882 @subsubsection OpenCL C Expressions
12884 @cindex OpenCL C Expressions
12885 @value{GDBN} supports accesses to vector components including the access as
12886 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12887 supported by @value{GDBN} can be used as well.
12889 @node OpenCL C Operators
12890 @subsubsection OpenCL C Operators
12892 @cindex OpenCL C Operators
12893 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12897 @subsection Fortran
12898 @cindex Fortran-specific support in @value{GDBN}
12900 @value{GDBN} can be used to debug programs written in Fortran, but it
12901 currently supports only the features of Fortran 77 language.
12903 @cindex trailing underscore, in Fortran symbols
12904 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12905 among them) append an underscore to the names of variables and
12906 functions. When you debug programs compiled by those compilers, you
12907 will need to refer to variables and functions with a trailing
12911 * Fortran Operators:: Fortran operators and expressions
12912 * Fortran Defaults:: Default settings for Fortran
12913 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12916 @node Fortran Operators
12917 @subsubsection Fortran Operators and Expressions
12919 @cindex Fortran operators and expressions
12921 Operators must be defined on values of specific types. For instance,
12922 @code{+} is defined on numbers, but not on characters or other non-
12923 arithmetic types. Operators are often defined on groups of types.
12927 The exponentiation operator. It raises the first operand to the power
12931 The range operator. Normally used in the form of array(low:high) to
12932 represent a section of array.
12935 The access component operator. Normally used to access elements in derived
12936 types. Also suitable for unions. As unions aren't part of regular Fortran,
12937 this can only happen when accessing a register that uses a gdbarch-defined
12941 @node Fortran Defaults
12942 @subsubsection Fortran Defaults
12944 @cindex Fortran Defaults
12946 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12947 default uses case-insensitive matches for Fortran symbols. You can
12948 change that with the @samp{set case-insensitive} command, see
12949 @ref{Symbols}, for the details.
12951 @node Special Fortran Commands
12952 @subsubsection Special Fortran Commands
12954 @cindex Special Fortran commands
12956 @value{GDBN} has some commands to support Fortran-specific features,
12957 such as displaying common blocks.
12960 @cindex @code{COMMON} blocks, Fortran
12961 @kindex info common
12962 @item info common @r{[}@var{common-name}@r{]}
12963 This command prints the values contained in the Fortran @code{COMMON}
12964 block whose name is @var{common-name}. With no argument, the names of
12965 all @code{COMMON} blocks visible at the current program location are
12972 @cindex Pascal support in @value{GDBN}, limitations
12973 Debugging Pascal programs which use sets, subranges, file variables, or
12974 nested functions does not currently work. @value{GDBN} does not support
12975 entering expressions, printing values, or similar features using Pascal
12978 The Pascal-specific command @code{set print pascal_static-members}
12979 controls whether static members of Pascal objects are displayed.
12980 @xref{Print Settings, pascal_static-members}.
12983 @subsection Modula-2
12985 @cindex Modula-2, @value{GDBN} support
12987 The extensions made to @value{GDBN} to support Modula-2 only support
12988 output from the @sc{gnu} Modula-2 compiler (which is currently being
12989 developed). Other Modula-2 compilers are not currently supported, and
12990 attempting to debug executables produced by them is most likely
12991 to give an error as @value{GDBN} reads in the executable's symbol
12994 @cindex expressions in Modula-2
12996 * M2 Operators:: Built-in operators
12997 * Built-In Func/Proc:: Built-in functions and procedures
12998 * M2 Constants:: Modula-2 constants
12999 * M2 Types:: Modula-2 types
13000 * M2 Defaults:: Default settings for Modula-2
13001 * Deviations:: Deviations from standard Modula-2
13002 * M2 Checks:: Modula-2 type and range checks
13003 * M2 Scope:: The scope operators @code{::} and @code{.}
13004 * GDB/M2:: @value{GDBN} and Modula-2
13008 @subsubsection Operators
13009 @cindex Modula-2 operators
13011 Operators must be defined on values of specific types. For instance,
13012 @code{+} is defined on numbers, but not on structures. Operators are
13013 often defined on groups of types. For the purposes of Modula-2, the
13014 following definitions hold:
13019 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13023 @emph{Character types} consist of @code{CHAR} and its subranges.
13026 @emph{Floating-point types} consist of @code{REAL}.
13029 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13033 @emph{Scalar types} consist of all of the above.
13036 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13039 @emph{Boolean types} consist of @code{BOOLEAN}.
13043 The following operators are supported, and appear in order of
13044 increasing precedence:
13048 Function argument or array index separator.
13051 Assignment. The value of @var{var} @code{:=} @var{value} is
13055 Less than, greater than on integral, floating-point, or enumerated
13059 Less than or equal to, greater than or equal to
13060 on integral, floating-point and enumerated types, or set inclusion on
13061 set types. Same precedence as @code{<}.
13063 @item =@r{, }<>@r{, }#
13064 Equality and two ways of expressing inequality, valid on scalar types.
13065 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13066 available for inequality, since @code{#} conflicts with the script
13070 Set membership. Defined on set types and the types of their members.
13071 Same precedence as @code{<}.
13074 Boolean disjunction. Defined on boolean types.
13077 Boolean conjunction. Defined on boolean types.
13080 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13083 Addition and subtraction on integral and floating-point types, or union
13084 and difference on set types.
13087 Multiplication on integral and floating-point types, or set intersection
13091 Division on floating-point types, or symmetric set difference on set
13092 types. Same precedence as @code{*}.
13095 Integer division and remainder. Defined on integral types. Same
13096 precedence as @code{*}.
13099 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13102 Pointer dereferencing. Defined on pointer types.
13105 Boolean negation. Defined on boolean types. Same precedence as
13109 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13110 precedence as @code{^}.
13113 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13116 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13120 @value{GDBN} and Modula-2 scope operators.
13124 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13125 treats the use of the operator @code{IN}, or the use of operators
13126 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13127 @code{<=}, and @code{>=} on sets as an error.
13131 @node Built-In Func/Proc
13132 @subsubsection Built-in Functions and Procedures
13133 @cindex Modula-2 built-ins
13135 Modula-2 also makes available several built-in procedures and functions.
13136 In describing these, the following metavariables are used:
13141 represents an @code{ARRAY} variable.
13144 represents a @code{CHAR} constant or variable.
13147 represents a variable or constant of integral type.
13150 represents an identifier that belongs to a set. Generally used in the
13151 same function with the metavariable @var{s}. The type of @var{s} should
13152 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13155 represents a variable or constant of integral or floating-point type.
13158 represents a variable or constant of floating-point type.
13164 represents a variable.
13167 represents a variable or constant of one of many types. See the
13168 explanation of the function for details.
13171 All Modula-2 built-in procedures also return a result, described below.
13175 Returns the absolute value of @var{n}.
13178 If @var{c} is a lower case letter, it returns its upper case
13179 equivalent, otherwise it returns its argument.
13182 Returns the character whose ordinal value is @var{i}.
13185 Decrements the value in the variable @var{v} by one. Returns the new value.
13187 @item DEC(@var{v},@var{i})
13188 Decrements the value in the variable @var{v} by @var{i}. Returns the
13191 @item EXCL(@var{m},@var{s})
13192 Removes the element @var{m} from the set @var{s}. Returns the new
13195 @item FLOAT(@var{i})
13196 Returns the floating point equivalent of the integer @var{i}.
13198 @item HIGH(@var{a})
13199 Returns the index of the last member of @var{a}.
13202 Increments the value in the variable @var{v} by one. Returns the new value.
13204 @item INC(@var{v},@var{i})
13205 Increments the value in the variable @var{v} by @var{i}. Returns the
13208 @item INCL(@var{m},@var{s})
13209 Adds the element @var{m} to the set @var{s} if it is not already
13210 there. Returns the new set.
13213 Returns the maximum value of the type @var{t}.
13216 Returns the minimum value of the type @var{t}.
13219 Returns boolean TRUE if @var{i} is an odd number.
13222 Returns the ordinal value of its argument. For example, the ordinal
13223 value of a character is its @sc{ascii} value (on machines supporting the
13224 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13225 integral, character and enumerated types.
13227 @item SIZE(@var{x})
13228 Returns the size of its argument. @var{x} can be a variable or a type.
13230 @item TRUNC(@var{r})
13231 Returns the integral part of @var{r}.
13233 @item TSIZE(@var{x})
13234 Returns the size of its argument. @var{x} can be a variable or a type.
13236 @item VAL(@var{t},@var{i})
13237 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13241 @emph{Warning:} Sets and their operations are not yet supported, so
13242 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13246 @cindex Modula-2 constants
13248 @subsubsection Constants
13250 @value{GDBN} allows you to express the constants of Modula-2 in the following
13256 Integer constants are simply a sequence of digits. When used in an
13257 expression, a constant is interpreted to be type-compatible with the
13258 rest of the expression. Hexadecimal integers are specified by a
13259 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13262 Floating point constants appear as a sequence of digits, followed by a
13263 decimal point and another sequence of digits. An optional exponent can
13264 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13265 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13266 digits of the floating point constant must be valid decimal (base 10)
13270 Character constants consist of a single character enclosed by a pair of
13271 like quotes, either single (@code{'}) or double (@code{"}). They may
13272 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13273 followed by a @samp{C}.
13276 String constants consist of a sequence of characters enclosed by a
13277 pair of like quotes, either single (@code{'}) or double (@code{"}).
13278 Escape sequences in the style of C are also allowed. @xref{C
13279 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13283 Enumerated constants consist of an enumerated identifier.
13286 Boolean constants consist of the identifiers @code{TRUE} and
13290 Pointer constants consist of integral values only.
13293 Set constants are not yet supported.
13297 @subsubsection Modula-2 Types
13298 @cindex Modula-2 types
13300 Currently @value{GDBN} can print the following data types in Modula-2
13301 syntax: array types, record types, set types, pointer types, procedure
13302 types, enumerated types, subrange types and base types. You can also
13303 print the contents of variables declared using these type.
13304 This section gives a number of simple source code examples together with
13305 sample @value{GDBN} sessions.
13307 The first example contains the following section of code:
13316 and you can request @value{GDBN} to interrogate the type and value of
13317 @code{r} and @code{s}.
13320 (@value{GDBP}) print s
13322 (@value{GDBP}) ptype s
13324 (@value{GDBP}) print r
13326 (@value{GDBP}) ptype r
13331 Likewise if your source code declares @code{s} as:
13335 s: SET ['A'..'Z'] ;
13339 then you may query the type of @code{s} by:
13342 (@value{GDBP}) ptype s
13343 type = SET ['A'..'Z']
13347 Note that at present you cannot interactively manipulate set
13348 expressions using the debugger.
13350 The following example shows how you might declare an array in Modula-2
13351 and how you can interact with @value{GDBN} to print its type and contents:
13355 s: ARRAY [-10..10] OF CHAR ;
13359 (@value{GDBP}) ptype s
13360 ARRAY [-10..10] OF CHAR
13363 Note that the array handling is not yet complete and although the type
13364 is printed correctly, expression handling still assumes that all
13365 arrays have a lower bound of zero and not @code{-10} as in the example
13368 Here are some more type related Modula-2 examples:
13372 colour = (blue, red, yellow, green) ;
13373 t = [blue..yellow] ;
13381 The @value{GDBN} interaction shows how you can query the data type
13382 and value of a variable.
13385 (@value{GDBP}) print s
13387 (@value{GDBP}) ptype t
13388 type = [blue..yellow]
13392 In this example a Modula-2 array is declared and its contents
13393 displayed. Observe that the contents are written in the same way as
13394 their @code{C} counterparts.
13398 s: ARRAY [1..5] OF CARDINAL ;
13404 (@value{GDBP}) print s
13405 $1 = @{1, 0, 0, 0, 0@}
13406 (@value{GDBP}) ptype s
13407 type = ARRAY [1..5] OF CARDINAL
13410 The Modula-2 language interface to @value{GDBN} also understands
13411 pointer types as shown in this example:
13415 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13422 and you can request that @value{GDBN} describes the type of @code{s}.
13425 (@value{GDBP}) ptype s
13426 type = POINTER TO ARRAY [1..5] OF CARDINAL
13429 @value{GDBN} handles compound types as we can see in this example.
13430 Here we combine array types, record types, pointer types and subrange
13441 myarray = ARRAY myrange OF CARDINAL ;
13442 myrange = [-2..2] ;
13444 s: POINTER TO ARRAY myrange OF foo ;
13448 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13452 (@value{GDBP}) ptype s
13453 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13456 f3 : ARRAY [-2..2] OF CARDINAL;
13461 @subsubsection Modula-2 Defaults
13462 @cindex Modula-2 defaults
13464 If type and range checking are set automatically by @value{GDBN}, they
13465 both default to @code{on} whenever the working language changes to
13466 Modula-2. This happens regardless of whether you or @value{GDBN}
13467 selected the working language.
13469 If you allow @value{GDBN} to set the language automatically, then entering
13470 code compiled from a file whose name ends with @file{.mod} sets the
13471 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13472 Infer the Source Language}, for further details.
13475 @subsubsection Deviations from Standard Modula-2
13476 @cindex Modula-2, deviations from
13478 A few changes have been made to make Modula-2 programs easier to debug.
13479 This is done primarily via loosening its type strictness:
13483 Unlike in standard Modula-2, pointer constants can be formed by
13484 integers. This allows you to modify pointer variables during
13485 debugging. (In standard Modula-2, the actual address contained in a
13486 pointer variable is hidden from you; it can only be modified
13487 through direct assignment to another pointer variable or expression that
13488 returned a pointer.)
13491 C escape sequences can be used in strings and characters to represent
13492 non-printable characters. @value{GDBN} prints out strings with these
13493 escape sequences embedded. Single non-printable characters are
13494 printed using the @samp{CHR(@var{nnn})} format.
13497 The assignment operator (@code{:=}) returns the value of its right-hand
13501 All built-in procedures both modify @emph{and} return their argument.
13505 @subsubsection Modula-2 Type and Range Checks
13506 @cindex Modula-2 checks
13509 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13512 @c FIXME remove warning when type/range checks added
13514 @value{GDBN} considers two Modula-2 variables type equivalent if:
13518 They are of types that have been declared equivalent via a @code{TYPE
13519 @var{t1} = @var{t2}} statement
13522 They have been declared on the same line. (Note: This is true of the
13523 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13526 As long as type checking is enabled, any attempt to combine variables
13527 whose types are not equivalent is an error.
13529 Range checking is done on all mathematical operations, assignment, array
13530 index bounds, and all built-in functions and procedures.
13533 @subsubsection The Scope Operators @code{::} and @code{.}
13535 @cindex @code{.}, Modula-2 scope operator
13536 @cindex colon, doubled as scope operator
13538 @vindex colon-colon@r{, in Modula-2}
13539 @c Info cannot handle :: but TeX can.
13542 @vindex ::@r{, in Modula-2}
13545 There are a few subtle differences between the Modula-2 scope operator
13546 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13551 @var{module} . @var{id}
13552 @var{scope} :: @var{id}
13556 where @var{scope} is the name of a module or a procedure,
13557 @var{module} the name of a module, and @var{id} is any declared
13558 identifier within your program, except another module.
13560 Using the @code{::} operator makes @value{GDBN} search the scope
13561 specified by @var{scope} for the identifier @var{id}. If it is not
13562 found in the specified scope, then @value{GDBN} searches all scopes
13563 enclosing the one specified by @var{scope}.
13565 Using the @code{.} operator makes @value{GDBN} search the current scope for
13566 the identifier specified by @var{id} that was imported from the
13567 definition module specified by @var{module}. With this operator, it is
13568 an error if the identifier @var{id} was not imported from definition
13569 module @var{module}, or if @var{id} is not an identifier in
13573 @subsubsection @value{GDBN} and Modula-2
13575 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13576 Five subcommands of @code{set print} and @code{show print} apply
13577 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13578 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13579 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13580 analogue in Modula-2.
13582 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13583 with any language, is not useful with Modula-2. Its
13584 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13585 created in Modula-2 as they can in C or C@t{++}. However, because an
13586 address can be specified by an integral constant, the construct
13587 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13589 @cindex @code{#} in Modula-2
13590 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13591 interpreted as the beginning of a comment. Use @code{<>} instead.
13597 The extensions made to @value{GDBN} for Ada only support
13598 output from the @sc{gnu} Ada (GNAT) compiler.
13599 Other Ada compilers are not currently supported, and
13600 attempting to debug executables produced by them is most likely
13604 @cindex expressions in Ada
13606 * Ada Mode Intro:: General remarks on the Ada syntax
13607 and semantics supported by Ada mode
13609 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13610 * Additions to Ada:: Extensions of the Ada expression syntax.
13611 * Stopping Before Main Program:: Debugging the program during elaboration.
13612 * Ada Tasks:: Listing and setting breakpoints in tasks.
13613 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13614 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13616 * Ada Glitches:: Known peculiarities of Ada mode.
13619 @node Ada Mode Intro
13620 @subsubsection Introduction
13621 @cindex Ada mode, general
13623 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13624 syntax, with some extensions.
13625 The philosophy behind the design of this subset is
13629 That @value{GDBN} should provide basic literals and access to operations for
13630 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13631 leaving more sophisticated computations to subprograms written into the
13632 program (which therefore may be called from @value{GDBN}).
13635 That type safety and strict adherence to Ada language restrictions
13636 are not particularly important to the @value{GDBN} user.
13639 That brevity is important to the @value{GDBN} user.
13642 Thus, for brevity, the debugger acts as if all names declared in
13643 user-written packages are directly visible, even if they are not visible
13644 according to Ada rules, thus making it unnecessary to fully qualify most
13645 names with their packages, regardless of context. Where this causes
13646 ambiguity, @value{GDBN} asks the user's intent.
13648 The debugger will start in Ada mode if it detects an Ada main program.
13649 As for other languages, it will enter Ada mode when stopped in a program that
13650 was translated from an Ada source file.
13652 While in Ada mode, you may use `@t{--}' for comments. This is useful
13653 mostly for documenting command files. The standard @value{GDBN} comment
13654 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13655 middle (to allow based literals).
13657 The debugger supports limited overloading. Given a subprogram call in which
13658 the function symbol has multiple definitions, it will use the number of
13659 actual parameters and some information about their types to attempt to narrow
13660 the set of definitions. It also makes very limited use of context, preferring
13661 procedures to functions in the context of the @code{call} command, and
13662 functions to procedures elsewhere.
13664 @node Omissions from Ada
13665 @subsubsection Omissions from Ada
13666 @cindex Ada, omissions from
13668 Here are the notable omissions from the subset:
13672 Only a subset of the attributes are supported:
13676 @t{'First}, @t{'Last}, and @t{'Length}
13677 on array objects (not on types and subtypes).
13680 @t{'Min} and @t{'Max}.
13683 @t{'Pos} and @t{'Val}.
13689 @t{'Range} on array objects (not subtypes), but only as the right
13690 operand of the membership (@code{in}) operator.
13693 @t{'Access}, @t{'Unchecked_Access}, and
13694 @t{'Unrestricted_Access} (a GNAT extension).
13702 @code{Characters.Latin_1} are not available and
13703 concatenation is not implemented. Thus, escape characters in strings are
13704 not currently available.
13707 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13708 equality of representations. They will generally work correctly
13709 for strings and arrays whose elements have integer or enumeration types.
13710 They may not work correctly for arrays whose element
13711 types have user-defined equality, for arrays of real values
13712 (in particular, IEEE-conformant floating point, because of negative
13713 zeroes and NaNs), and for arrays whose elements contain unused bits with
13714 indeterminate values.
13717 The other component-by-component array operations (@code{and}, @code{or},
13718 @code{xor}, @code{not}, and relational tests other than equality)
13719 are not implemented.
13722 @cindex array aggregates (Ada)
13723 @cindex record aggregates (Ada)
13724 @cindex aggregates (Ada)
13725 There is limited support for array and record aggregates. They are
13726 permitted only on the right sides of assignments, as in these examples:
13729 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13730 (@value{GDBP}) set An_Array := (1, others => 0)
13731 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13732 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13733 (@value{GDBP}) set A_Record := (1, "Peter", True);
13734 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13738 discriminant's value by assigning an aggregate has an
13739 undefined effect if that discriminant is used within the record.
13740 However, you can first modify discriminants by directly assigning to
13741 them (which normally would not be allowed in Ada), and then performing an
13742 aggregate assignment. For example, given a variable @code{A_Rec}
13743 declared to have a type such as:
13746 type Rec (Len : Small_Integer := 0) is record
13748 Vals : IntArray (1 .. Len);
13752 you can assign a value with a different size of @code{Vals} with two
13756 (@value{GDBP}) set A_Rec.Len := 4
13757 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13760 As this example also illustrates, @value{GDBN} is very loose about the usual
13761 rules concerning aggregates. You may leave out some of the
13762 components of an array or record aggregate (such as the @code{Len}
13763 component in the assignment to @code{A_Rec} above); they will retain their
13764 original values upon assignment. You may freely use dynamic values as
13765 indices in component associations. You may even use overlapping or
13766 redundant component associations, although which component values are
13767 assigned in such cases is not defined.
13770 Calls to dispatching subprograms are not implemented.
13773 The overloading algorithm is much more limited (i.e., less selective)
13774 than that of real Ada. It makes only limited use of the context in
13775 which a subexpression appears to resolve its meaning, and it is much
13776 looser in its rules for allowing type matches. As a result, some
13777 function calls will be ambiguous, and the user will be asked to choose
13778 the proper resolution.
13781 The @code{new} operator is not implemented.
13784 Entry calls are not implemented.
13787 Aside from printing, arithmetic operations on the native VAX floating-point
13788 formats are not supported.
13791 It is not possible to slice a packed array.
13794 The names @code{True} and @code{False}, when not part of a qualified name,
13795 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13797 Should your program
13798 redefine these names in a package or procedure (at best a dubious practice),
13799 you will have to use fully qualified names to access their new definitions.
13802 @node Additions to Ada
13803 @subsubsection Additions to Ada
13804 @cindex Ada, deviations from
13806 As it does for other languages, @value{GDBN} makes certain generic
13807 extensions to Ada (@pxref{Expressions}):
13811 If the expression @var{E} is a variable residing in memory (typically
13812 a local variable or array element) and @var{N} is a positive integer,
13813 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13814 @var{N}-1 adjacent variables following it in memory as an array. In
13815 Ada, this operator is generally not necessary, since its prime use is
13816 in displaying parts of an array, and slicing will usually do this in
13817 Ada. However, there are occasional uses when debugging programs in
13818 which certain debugging information has been optimized away.
13821 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13822 appears in function or file @var{B}.'' When @var{B} is a file name,
13823 you must typically surround it in single quotes.
13826 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13827 @var{type} that appears at address @var{addr}.''
13830 A name starting with @samp{$} is a convenience variable
13831 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13834 In addition, @value{GDBN} provides a few other shortcuts and outright
13835 additions specific to Ada:
13839 The assignment statement is allowed as an expression, returning
13840 its right-hand operand as its value. Thus, you may enter
13843 (@value{GDBP}) set x := y + 3
13844 (@value{GDBP}) print A(tmp := y + 1)
13848 The semicolon is allowed as an ``operator,'' returning as its value
13849 the value of its right-hand operand.
13850 This allows, for example,
13851 complex conditional breaks:
13854 (@value{GDBP}) break f
13855 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13859 Rather than use catenation and symbolic character names to introduce special
13860 characters into strings, one may instead use a special bracket notation,
13861 which is also used to print strings. A sequence of characters of the form
13862 @samp{["@var{XX}"]} within a string or character literal denotes the
13863 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13864 sequence of characters @samp{["""]} also denotes a single quotation mark
13865 in strings. For example,
13867 "One line.["0a"]Next line.["0a"]"
13870 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13874 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13875 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13879 (@value{GDBP}) print 'max(x, y)
13883 When printing arrays, @value{GDBN} uses positional notation when the
13884 array has a lower bound of 1, and uses a modified named notation otherwise.
13885 For example, a one-dimensional array of three integers with a lower bound
13886 of 3 might print as
13893 That is, in contrast to valid Ada, only the first component has a @code{=>}
13897 You may abbreviate attributes in expressions with any unique,
13898 multi-character subsequence of
13899 their names (an exact match gets preference).
13900 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13901 in place of @t{a'length}.
13904 @cindex quoting Ada internal identifiers
13905 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13906 to lower case. The GNAT compiler uses upper-case characters for
13907 some of its internal identifiers, which are normally of no interest to users.
13908 For the rare occasions when you actually have to look at them,
13909 enclose them in angle brackets to avoid the lower-case mapping.
13912 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13916 Printing an object of class-wide type or dereferencing an
13917 access-to-class-wide value will display all the components of the object's
13918 specific type (as indicated by its run-time tag). Likewise, component
13919 selection on such a value will operate on the specific type of the
13924 @node Stopping Before Main Program
13925 @subsubsection Stopping at the Very Beginning
13927 @cindex breakpointing Ada elaboration code
13928 It is sometimes necessary to debug the program during elaboration, and
13929 before reaching the main procedure.
13930 As defined in the Ada Reference
13931 Manual, the elaboration code is invoked from a procedure called
13932 @code{adainit}. To run your program up to the beginning of
13933 elaboration, simply use the following two commands:
13934 @code{tbreak adainit} and @code{run}.
13937 @subsubsection Extensions for Ada Tasks
13938 @cindex Ada, tasking
13940 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13941 @value{GDBN} provides the following task-related commands:
13946 This command shows a list of current Ada tasks, as in the following example:
13953 (@value{GDBP}) info tasks
13954 ID TID P-ID Pri State Name
13955 1 8088000 0 15 Child Activation Wait main_task
13956 2 80a4000 1 15 Accept Statement b
13957 3 809a800 1 15 Child Activation Wait a
13958 * 4 80ae800 3 15 Runnable c
13963 In this listing, the asterisk before the last task indicates it to be the
13964 task currently being inspected.
13968 Represents @value{GDBN}'s internal task number.
13974 The parent's task ID (@value{GDBN}'s internal task number).
13977 The base priority of the task.
13980 Current state of the task.
13984 The task has been created but has not been activated. It cannot be
13988 The task is not blocked for any reason known to Ada. (It may be waiting
13989 for a mutex, though.) It is conceptually "executing" in normal mode.
13992 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13993 that were waiting on terminate alternatives have been awakened and have
13994 terminated themselves.
13996 @item Child Activation Wait
13997 The task is waiting for created tasks to complete activation.
13999 @item Accept Statement
14000 The task is waiting on an accept or selective wait statement.
14002 @item Waiting on entry call
14003 The task is waiting on an entry call.
14005 @item Async Select Wait
14006 The task is waiting to start the abortable part of an asynchronous
14010 The task is waiting on a select statement with only a delay
14013 @item Child Termination Wait
14014 The task is sleeping having completed a master within itself, and is
14015 waiting for the tasks dependent on that master to become terminated or
14016 waiting on a terminate Phase.
14018 @item Wait Child in Term Alt
14019 The task is sleeping waiting for tasks on terminate alternatives to
14020 finish terminating.
14022 @item Accepting RV with @var{taskno}
14023 The task is accepting a rendez-vous with the task @var{taskno}.
14027 Name of the task in the program.
14031 @kindex info task @var{taskno}
14032 @item info task @var{taskno}
14033 This command shows detailled informations on the specified task, as in
14034 the following example:
14039 (@value{GDBP}) info tasks
14040 ID TID P-ID Pri State Name
14041 1 8077880 0 15 Child Activation Wait main_task
14042 * 2 807c468 1 15 Runnable task_1
14043 (@value{GDBP}) info task 2
14044 Ada Task: 0x807c468
14047 Parent: 1 (main_task)
14053 @kindex task@r{ (Ada)}
14054 @cindex current Ada task ID
14055 This command prints the ID of the current task.
14061 (@value{GDBP}) info tasks
14062 ID TID P-ID Pri State Name
14063 1 8077870 0 15 Child Activation Wait main_task
14064 * 2 807c458 1 15 Runnable t
14065 (@value{GDBP}) task
14066 [Current task is 2]
14069 @item task @var{taskno}
14070 @cindex Ada task switching
14071 This command is like the @code{thread @var{threadno}}
14072 command (@pxref{Threads}). It switches the context of debugging
14073 from the current task to the given task.
14079 (@value{GDBP}) info tasks
14080 ID TID P-ID Pri State Name
14081 1 8077870 0 15 Child Activation Wait main_task
14082 * 2 807c458 1 15 Runnable t
14083 (@value{GDBP}) task 1
14084 [Switching to task 1]
14085 #0 0x8067726 in pthread_cond_wait ()
14087 #0 0x8067726 in pthread_cond_wait ()
14088 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14089 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14090 #3 0x806153e in system.tasking.stages.activate_tasks ()
14091 #4 0x804aacc in un () at un.adb:5
14094 @item break @var{linespec} task @var{taskno}
14095 @itemx break @var{linespec} task @var{taskno} if @dots{}
14096 @cindex breakpoints and tasks, in Ada
14097 @cindex task breakpoints, in Ada
14098 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14099 These commands are like the @code{break @dots{} thread @dots{}}
14100 command (@pxref{Thread Stops}).
14101 @var{linespec} specifies source lines, as described
14102 in @ref{Specify Location}.
14104 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14105 to specify that you only want @value{GDBN} to stop the program when a
14106 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14107 numeric task identifiers assigned by @value{GDBN}, shown in the first
14108 column of the @samp{info tasks} display.
14110 If you do not specify @samp{task @var{taskno}} when you set a
14111 breakpoint, the breakpoint applies to @emph{all} tasks of your
14114 You can use the @code{task} qualifier on conditional breakpoints as
14115 well; in this case, place @samp{task @var{taskno}} before the
14116 breakpoint condition (before the @code{if}).
14124 (@value{GDBP}) info tasks
14125 ID TID P-ID Pri State Name
14126 1 140022020 0 15 Child Activation Wait main_task
14127 2 140045060 1 15 Accept/Select Wait t2
14128 3 140044840 1 15 Runnable t1
14129 * 4 140056040 1 15 Runnable t3
14130 (@value{GDBP}) b 15 task 2
14131 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14132 (@value{GDBP}) cont
14137 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14139 (@value{GDBP}) info tasks
14140 ID TID P-ID Pri State Name
14141 1 140022020 0 15 Child Activation Wait main_task
14142 * 2 140045060 1 15 Runnable t2
14143 3 140044840 1 15 Runnable t1
14144 4 140056040 1 15 Delay Sleep t3
14148 @node Ada Tasks and Core Files
14149 @subsubsection Tasking Support when Debugging Core Files
14150 @cindex Ada tasking and core file debugging
14152 When inspecting a core file, as opposed to debugging a live program,
14153 tasking support may be limited or even unavailable, depending on
14154 the platform being used.
14155 For instance, on x86-linux, the list of tasks is available, but task
14156 switching is not supported. On Tru64, however, task switching will work
14159 On certain platforms, including Tru64, the debugger needs to perform some
14160 memory writes in order to provide Ada tasking support. When inspecting
14161 a core file, this means that the core file must be opened with read-write
14162 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14163 Under these circumstances, you should make a backup copy of the core
14164 file before inspecting it with @value{GDBN}.
14166 @node Ravenscar Profile
14167 @subsubsection Tasking Support when using the Ravenscar Profile
14168 @cindex Ravenscar Profile
14170 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14171 specifically designed for systems with safety-critical real-time
14175 @kindex set ravenscar task-switching on
14176 @cindex task switching with program using Ravenscar Profile
14177 @item set ravenscar task-switching on
14178 Allows task switching when debugging a program that uses the Ravenscar
14179 Profile. This is the default.
14181 @kindex set ravenscar task-switching off
14182 @item set ravenscar task-switching off
14183 Turn off task switching when debugging a program that uses the Ravenscar
14184 Profile. This is mostly intended to disable the code that adds support
14185 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14186 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14187 To be effective, this command should be run before the program is started.
14189 @kindex show ravenscar task-switching
14190 @item show ravenscar task-switching
14191 Show whether it is possible to switch from task to task in a program
14192 using the Ravenscar Profile.
14197 @subsubsection Known Peculiarities of Ada Mode
14198 @cindex Ada, problems
14200 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14201 we know of several problems with and limitations of Ada mode in
14203 some of which will be fixed with planned future releases of the debugger
14204 and the GNU Ada compiler.
14208 Static constants that the compiler chooses not to materialize as objects in
14209 storage are invisible to the debugger.
14212 Named parameter associations in function argument lists are ignored (the
14213 argument lists are treated as positional).
14216 Many useful library packages are currently invisible to the debugger.
14219 Fixed-point arithmetic, conversions, input, and output is carried out using
14220 floating-point arithmetic, and may give results that only approximate those on
14224 The GNAT compiler never generates the prefix @code{Standard} for any of
14225 the standard symbols defined by the Ada language. @value{GDBN} knows about
14226 this: it will strip the prefix from names when you use it, and will never
14227 look for a name you have so qualified among local symbols, nor match against
14228 symbols in other packages or subprograms. If you have
14229 defined entities anywhere in your program other than parameters and
14230 local variables whose simple names match names in @code{Standard},
14231 GNAT's lack of qualification here can cause confusion. When this happens,
14232 you can usually resolve the confusion
14233 by qualifying the problematic names with package
14234 @code{Standard} explicitly.
14237 Older versions of the compiler sometimes generate erroneous debugging
14238 information, resulting in the debugger incorrectly printing the value
14239 of affected entities. In some cases, the debugger is able to work
14240 around an issue automatically. In other cases, the debugger is able
14241 to work around the issue, but the work-around has to be specifically
14244 @kindex set ada trust-PAD-over-XVS
14245 @kindex show ada trust-PAD-over-XVS
14248 @item set ada trust-PAD-over-XVS on
14249 Configure GDB to strictly follow the GNAT encoding when computing the
14250 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14251 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14252 a complete description of the encoding used by the GNAT compiler).
14253 This is the default.
14255 @item set ada trust-PAD-over-XVS off
14256 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14257 sometimes prints the wrong value for certain entities, changing @code{ada
14258 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14259 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14260 @code{off}, but this incurs a slight performance penalty, so it is
14261 recommended to leave this setting to @code{on} unless necessary.
14265 @node Unsupported Languages
14266 @section Unsupported Languages
14268 @cindex unsupported languages
14269 @cindex minimal language
14270 In addition to the other fully-supported programming languages,
14271 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14272 It does not represent a real programming language, but provides a set
14273 of capabilities close to what the C or assembly languages provide.
14274 This should allow most simple operations to be performed while debugging
14275 an application that uses a language currently not supported by @value{GDBN}.
14277 If the language is set to @code{auto}, @value{GDBN} will automatically
14278 select this language if the current frame corresponds to an unsupported
14282 @chapter Examining the Symbol Table
14284 The commands described in this chapter allow you to inquire about the
14285 symbols (names of variables, functions and types) defined in your
14286 program. This information is inherent in the text of your program and
14287 does not change as your program executes. @value{GDBN} finds it in your
14288 program's symbol table, in the file indicated when you started @value{GDBN}
14289 (@pxref{File Options, ,Choosing Files}), or by one of the
14290 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14292 @cindex symbol names
14293 @cindex names of symbols
14294 @cindex quoting names
14295 Occasionally, you may need to refer to symbols that contain unusual
14296 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14297 most frequent case is in referring to static variables in other
14298 source files (@pxref{Variables,,Program Variables}). File names
14299 are recorded in object files as debugging symbols, but @value{GDBN} would
14300 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14301 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14302 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14309 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14312 @cindex case-insensitive symbol names
14313 @cindex case sensitivity in symbol names
14314 @kindex set case-sensitive
14315 @item set case-sensitive on
14316 @itemx set case-sensitive off
14317 @itemx set case-sensitive auto
14318 Normally, when @value{GDBN} looks up symbols, it matches their names
14319 with case sensitivity determined by the current source language.
14320 Occasionally, you may wish to control that. The command @code{set
14321 case-sensitive} lets you do that by specifying @code{on} for
14322 case-sensitive matches or @code{off} for case-insensitive ones. If
14323 you specify @code{auto}, case sensitivity is reset to the default
14324 suitable for the source language. The default is case-sensitive
14325 matches for all languages except for Fortran, for which the default is
14326 case-insensitive matches.
14328 @kindex show case-sensitive
14329 @item show case-sensitive
14330 This command shows the current setting of case sensitivity for symbols
14333 @kindex info address
14334 @cindex address of a symbol
14335 @item info address @var{symbol}
14336 Describe where the data for @var{symbol} is stored. For a register
14337 variable, this says which register it is kept in. For a non-register
14338 local variable, this prints the stack-frame offset at which the variable
14341 Note the contrast with @samp{print &@var{symbol}}, which does not work
14342 at all for a register variable, and for a stack local variable prints
14343 the exact address of the current instantiation of the variable.
14345 @kindex info symbol
14346 @cindex symbol from address
14347 @cindex closest symbol and offset for an address
14348 @item info symbol @var{addr}
14349 Print the name of a symbol which is stored at the address @var{addr}.
14350 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14351 nearest symbol and an offset from it:
14354 (@value{GDBP}) info symbol 0x54320
14355 _initialize_vx + 396 in section .text
14359 This is the opposite of the @code{info address} command. You can use
14360 it to find out the name of a variable or a function given its address.
14362 For dynamically linked executables, the name of executable or shared
14363 library containing the symbol is also printed:
14366 (@value{GDBP}) info symbol 0x400225
14367 _start + 5 in section .text of /tmp/a.out
14368 (@value{GDBP}) info symbol 0x2aaaac2811cf
14369 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14373 @item whatis [@var{arg}]
14374 Print the data type of @var{arg}, which can be either an expression
14375 or a name of a data type. With no argument, print the data type of
14376 @code{$}, the last value in the value history.
14378 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14379 is not actually evaluated, and any side-effecting operations (such as
14380 assignments or function calls) inside it do not take place.
14382 If @var{arg} is a variable or an expression, @code{whatis} prints its
14383 literal type as it is used in the source code. If the type was
14384 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14385 the data type underlying the @code{typedef}. If the type of the
14386 variable or the expression is a compound data type, such as
14387 @code{struct} or @code{class}, @code{whatis} never prints their
14388 fields or methods. It just prints the @code{struct}/@code{class}
14389 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14390 such a compound data type, use @code{ptype}.
14392 If @var{arg} is a type name that was defined using @code{typedef},
14393 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14394 Unrolling means that @code{whatis} will show the underlying type used
14395 in the @code{typedef} declaration of @var{arg}. However, if that
14396 underlying type is also a @code{typedef}, @code{whatis} will not
14399 For C code, the type names may also have the form @samp{class
14400 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14401 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14404 @item ptype [@var{arg}]
14405 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14406 detailed description of the type, instead of just the name of the type.
14407 @xref{Expressions, ,Expressions}.
14409 Contrary to @code{whatis}, @code{ptype} always unrolls any
14410 @code{typedef}s in its argument declaration, whether the argument is
14411 a variable, expression, or a data type. This means that @code{ptype}
14412 of a variable or an expression will not print literally its type as
14413 present in the source code---use @code{whatis} for that. @code{typedef}s at
14414 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14415 fields, methods and inner @code{class typedef}s of @code{struct}s,
14416 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14418 For example, for this variable declaration:
14421 typedef double real_t;
14422 struct complex @{ real_t real; double imag; @};
14423 typedef struct complex complex_t;
14425 real_t *real_pointer_var;
14429 the two commands give this output:
14433 (@value{GDBP}) whatis var
14435 (@value{GDBP}) ptype var
14436 type = struct complex @{
14440 (@value{GDBP}) whatis complex_t
14441 type = struct complex
14442 (@value{GDBP}) whatis struct complex
14443 type = struct complex
14444 (@value{GDBP}) ptype struct complex
14445 type = struct complex @{
14449 (@value{GDBP}) whatis real_pointer_var
14451 (@value{GDBP}) ptype real_pointer_var
14457 As with @code{whatis}, using @code{ptype} without an argument refers to
14458 the type of @code{$}, the last value in the value history.
14460 @cindex incomplete type
14461 Sometimes, programs use opaque data types or incomplete specifications
14462 of complex data structure. If the debug information included in the
14463 program does not allow @value{GDBN} to display a full declaration of
14464 the data type, it will say @samp{<incomplete type>}. For example,
14465 given these declarations:
14469 struct foo *fooptr;
14473 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14476 (@value{GDBP}) ptype foo
14477 $1 = <incomplete type>
14481 ``Incomplete type'' is C terminology for data types that are not
14482 completely specified.
14485 @item info types @var{regexp}
14487 Print a brief description of all types whose names match the regular
14488 expression @var{regexp} (or all types in your program, if you supply
14489 no argument). Each complete typename is matched as though it were a
14490 complete line; thus, @samp{i type value} gives information on all
14491 types in your program whose names include the string @code{value}, but
14492 @samp{i type ^value$} gives information only on types whose complete
14493 name is @code{value}.
14495 This command differs from @code{ptype} in two ways: first, like
14496 @code{whatis}, it does not print a detailed description; second, it
14497 lists all source files where a type is defined.
14500 @cindex local variables
14501 @item info scope @var{location}
14502 List all the variables local to a particular scope. This command
14503 accepts a @var{location} argument---a function name, a source line, or
14504 an address preceded by a @samp{*}, and prints all the variables local
14505 to the scope defined by that location. (@xref{Specify Location}, for
14506 details about supported forms of @var{location}.) For example:
14509 (@value{GDBP}) @b{info scope command_line_handler}
14510 Scope for command_line_handler:
14511 Symbol rl is an argument at stack/frame offset 8, length 4.
14512 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14513 Symbol linelength is in static storage at address 0x150a1c, length 4.
14514 Symbol p is a local variable in register $esi, length 4.
14515 Symbol p1 is a local variable in register $ebx, length 4.
14516 Symbol nline is a local variable in register $edx, length 4.
14517 Symbol repeat is a local variable at frame offset -8, length 4.
14521 This command is especially useful for determining what data to collect
14522 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14525 @kindex info source
14527 Show information about the current source file---that is, the source file for
14528 the function containing the current point of execution:
14531 the name of the source file, and the directory containing it,
14533 the directory it was compiled in,
14535 its length, in lines,
14537 which programming language it is written in,
14539 whether the executable includes debugging information for that file, and
14540 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14542 whether the debugging information includes information about
14543 preprocessor macros.
14547 @kindex info sources
14549 Print the names of all source files in your program for which there is
14550 debugging information, organized into two lists: files whose symbols
14551 have already been read, and files whose symbols will be read when needed.
14553 @kindex info functions
14554 @item info functions
14555 Print the names and data types of all defined functions.
14557 @item info functions @var{regexp}
14558 Print the names and data types of all defined functions
14559 whose names contain a match for regular expression @var{regexp}.
14560 Thus, @samp{info fun step} finds all functions whose names
14561 include @code{step}; @samp{info fun ^step} finds those whose names
14562 start with @code{step}. If a function name contains characters
14563 that conflict with the regular expression language (e.g.@:
14564 @samp{operator*()}), they may be quoted with a backslash.
14566 @kindex info variables
14567 @item info variables
14568 Print the names and data types of all variables that are defined
14569 outside of functions (i.e.@: excluding local variables).
14571 @item info variables @var{regexp}
14572 Print the names and data types of all variables (except for local
14573 variables) whose names contain a match for regular expression
14576 @kindex info classes
14577 @cindex Objective-C, classes and selectors
14579 @itemx info classes @var{regexp}
14580 Display all Objective-C classes in your program, or
14581 (with the @var{regexp} argument) all those matching a particular regular
14584 @kindex info selectors
14585 @item info selectors
14586 @itemx info selectors @var{regexp}
14587 Display all Objective-C selectors in your program, or
14588 (with the @var{regexp} argument) all those matching a particular regular
14592 This was never implemented.
14593 @kindex info methods
14595 @itemx info methods @var{regexp}
14596 The @code{info methods} command permits the user to examine all defined
14597 methods within C@t{++} program, or (with the @var{regexp} argument) a
14598 specific set of methods found in the various C@t{++} classes. Many
14599 C@t{++} classes provide a large number of methods. Thus, the output
14600 from the @code{ptype} command can be overwhelming and hard to use. The
14601 @code{info-methods} command filters the methods, printing only those
14602 which match the regular-expression @var{regexp}.
14605 @cindex reloading symbols
14606 Some systems allow individual object files that make up your program to
14607 be replaced without stopping and restarting your program. For example,
14608 in VxWorks you can simply recompile a defective object file and keep on
14609 running. If you are running on one of these systems, you can allow
14610 @value{GDBN} to reload the symbols for automatically relinked modules:
14613 @kindex set symbol-reloading
14614 @item set symbol-reloading on
14615 Replace symbol definitions for the corresponding source file when an
14616 object file with a particular name is seen again.
14618 @item set symbol-reloading off
14619 Do not replace symbol definitions when encountering object files of the
14620 same name more than once. This is the default state; if you are not
14621 running on a system that permits automatic relinking of modules, you
14622 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14623 may discard symbols when linking large programs, that may contain
14624 several modules (from different directories or libraries) with the same
14627 @kindex show symbol-reloading
14628 @item show symbol-reloading
14629 Show the current @code{on} or @code{off} setting.
14632 @cindex opaque data types
14633 @kindex set opaque-type-resolution
14634 @item set opaque-type-resolution on
14635 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14636 declared as a pointer to a @code{struct}, @code{class}, or
14637 @code{union}---for example, @code{struct MyType *}---that is used in one
14638 source file although the full declaration of @code{struct MyType} is in
14639 another source file. The default is on.
14641 A change in the setting of this subcommand will not take effect until
14642 the next time symbols for a file are loaded.
14644 @item set opaque-type-resolution off
14645 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14646 is printed as follows:
14648 @{<no data fields>@}
14651 @kindex show opaque-type-resolution
14652 @item show opaque-type-resolution
14653 Show whether opaque types are resolved or not.
14655 @kindex maint print symbols
14656 @cindex symbol dump
14657 @kindex maint print psymbols
14658 @cindex partial symbol dump
14659 @item maint print symbols @var{filename}
14660 @itemx maint print psymbols @var{filename}
14661 @itemx maint print msymbols @var{filename}
14662 Write a dump of debugging symbol data into the file @var{filename}.
14663 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14664 symbols with debugging data are included. If you use @samp{maint print
14665 symbols}, @value{GDBN} includes all the symbols for which it has already
14666 collected full details: that is, @var{filename} reflects symbols for
14667 only those files whose symbols @value{GDBN} has read. You can use the
14668 command @code{info sources} to find out which files these are. If you
14669 use @samp{maint print psymbols} instead, the dump shows information about
14670 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14671 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14672 @samp{maint print msymbols} dumps just the minimal symbol information
14673 required for each object file from which @value{GDBN} has read some symbols.
14674 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14675 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14677 @kindex maint info symtabs
14678 @kindex maint info psymtabs
14679 @cindex listing @value{GDBN}'s internal symbol tables
14680 @cindex symbol tables, listing @value{GDBN}'s internal
14681 @cindex full symbol tables, listing @value{GDBN}'s internal
14682 @cindex partial symbol tables, listing @value{GDBN}'s internal
14683 @item maint info symtabs @r{[} @var{regexp} @r{]}
14684 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14686 List the @code{struct symtab} or @code{struct partial_symtab}
14687 structures whose names match @var{regexp}. If @var{regexp} is not
14688 given, list them all. The output includes expressions which you can
14689 copy into a @value{GDBN} debugging this one to examine a particular
14690 structure in more detail. For example:
14693 (@value{GDBP}) maint info psymtabs dwarf2read
14694 @{ objfile /home/gnu/build/gdb/gdb
14695 ((struct objfile *) 0x82e69d0)
14696 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14697 ((struct partial_symtab *) 0x8474b10)
14700 text addresses 0x814d3c8 -- 0x8158074
14701 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14702 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14703 dependencies (none)
14706 (@value{GDBP}) maint info symtabs
14710 We see that there is one partial symbol table whose filename contains
14711 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14712 and we see that @value{GDBN} has not read in any symtabs yet at all.
14713 If we set a breakpoint on a function, that will cause @value{GDBN} to
14714 read the symtab for the compilation unit containing that function:
14717 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14718 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14720 (@value{GDBP}) maint info symtabs
14721 @{ objfile /home/gnu/build/gdb/gdb
14722 ((struct objfile *) 0x82e69d0)
14723 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14724 ((struct symtab *) 0x86c1f38)
14727 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14728 linetable ((struct linetable *) 0x8370fa0)
14729 debugformat DWARF 2
14738 @chapter Altering Execution
14740 Once you think you have found an error in your program, you might want to
14741 find out for certain whether correcting the apparent error would lead to
14742 correct results in the rest of the run. You can find the answer by
14743 experiment, using the @value{GDBN} features for altering execution of the
14746 For example, you can store new values into variables or memory
14747 locations, give your program a signal, restart it at a different
14748 address, or even return prematurely from a function.
14751 * Assignment:: Assignment to variables
14752 * Jumping:: Continuing at a different address
14753 * Signaling:: Giving your program a signal
14754 * Returning:: Returning from a function
14755 * Calling:: Calling your program's functions
14756 * Patching:: Patching your program
14760 @section Assignment to Variables
14763 @cindex setting variables
14764 To alter the value of a variable, evaluate an assignment expression.
14765 @xref{Expressions, ,Expressions}. For example,
14772 stores the value 4 into the variable @code{x}, and then prints the
14773 value of the assignment expression (which is 4).
14774 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14775 information on operators in supported languages.
14777 @kindex set variable
14778 @cindex variables, setting
14779 If you are not interested in seeing the value of the assignment, use the
14780 @code{set} command instead of the @code{print} command. @code{set} is
14781 really the same as @code{print} except that the expression's value is
14782 not printed and is not put in the value history (@pxref{Value History,
14783 ,Value History}). The expression is evaluated only for its effects.
14785 If the beginning of the argument string of the @code{set} command
14786 appears identical to a @code{set} subcommand, use the @code{set
14787 variable} command instead of just @code{set}. This command is identical
14788 to @code{set} except for its lack of subcommands. For example, if your
14789 program has a variable @code{width}, you get an error if you try to set
14790 a new value with just @samp{set width=13}, because @value{GDBN} has the
14791 command @code{set width}:
14794 (@value{GDBP}) whatis width
14796 (@value{GDBP}) p width
14798 (@value{GDBP}) set width=47
14799 Invalid syntax in expression.
14803 The invalid expression, of course, is @samp{=47}. In
14804 order to actually set the program's variable @code{width}, use
14807 (@value{GDBP}) set var width=47
14810 Because the @code{set} command has many subcommands that can conflict
14811 with the names of program variables, it is a good idea to use the
14812 @code{set variable} command instead of just @code{set}. For example, if
14813 your program has a variable @code{g}, you run into problems if you try
14814 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14815 the command @code{set gnutarget}, abbreviated @code{set g}:
14819 (@value{GDBP}) whatis g
14823 (@value{GDBP}) set g=4
14827 The program being debugged has been started already.
14828 Start it from the beginning? (y or n) y
14829 Starting program: /home/smith/cc_progs/a.out
14830 "/home/smith/cc_progs/a.out": can't open to read symbols:
14831 Invalid bfd target.
14832 (@value{GDBP}) show g
14833 The current BFD target is "=4".
14838 The program variable @code{g} did not change, and you silently set the
14839 @code{gnutarget} to an invalid value. In order to set the variable
14843 (@value{GDBP}) set var g=4
14846 @value{GDBN} allows more implicit conversions in assignments than C; you can
14847 freely store an integer value into a pointer variable or vice versa,
14848 and you can convert any structure to any other structure that is the
14849 same length or shorter.
14850 @comment FIXME: how do structs align/pad in these conversions?
14851 @comment /doc@cygnus.com 18dec1990
14853 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14854 construct to generate a value of specified type at a specified address
14855 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14856 to memory location @code{0x83040} as an integer (which implies a certain size
14857 and representation in memory), and
14860 set @{int@}0x83040 = 4
14864 stores the value 4 into that memory location.
14867 @section Continuing at a Different Address
14869 Ordinarily, when you continue your program, you do so at the place where
14870 it stopped, with the @code{continue} command. You can instead continue at
14871 an address of your own choosing, with the following commands:
14875 @item jump @var{linespec}
14876 @itemx jump @var{location}
14877 Resume execution at line @var{linespec} or at address given by
14878 @var{location}. Execution stops again immediately if there is a
14879 breakpoint there. @xref{Specify Location}, for a description of the
14880 different forms of @var{linespec} and @var{location}. It is common
14881 practice to use the @code{tbreak} command in conjunction with
14882 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14884 The @code{jump} command does not change the current stack frame, or
14885 the stack pointer, or the contents of any memory location or any
14886 register other than the program counter. If line @var{linespec} is in
14887 a different function from the one currently executing, the results may
14888 be bizarre if the two functions expect different patterns of arguments or
14889 of local variables. For this reason, the @code{jump} command requests
14890 confirmation if the specified line is not in the function currently
14891 executing. However, even bizarre results are predictable if you are
14892 well acquainted with the machine-language code of your program.
14895 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14896 On many systems, you can get much the same effect as the @code{jump}
14897 command by storing a new value into the register @code{$pc}. The
14898 difference is that this does not start your program running; it only
14899 changes the address of where it @emph{will} run when you continue. For
14907 makes the next @code{continue} command or stepping command execute at
14908 address @code{0x485}, rather than at the address where your program stopped.
14909 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14911 The most common occasion to use the @code{jump} command is to back
14912 up---perhaps with more breakpoints set---over a portion of a program
14913 that has already executed, in order to examine its execution in more
14918 @section Giving your Program a Signal
14919 @cindex deliver a signal to a program
14923 @item signal @var{signal}
14924 Resume execution where your program stopped, but immediately give it the
14925 signal @var{signal}. @var{signal} can be the name or the number of a
14926 signal. For example, on many systems @code{signal 2} and @code{signal
14927 SIGINT} are both ways of sending an interrupt signal.
14929 Alternatively, if @var{signal} is zero, continue execution without
14930 giving a signal. This is useful when your program stopped on account of
14931 a signal and would ordinary see the signal when resumed with the
14932 @code{continue} command; @samp{signal 0} causes it to resume without a
14935 @code{signal} does not repeat when you press @key{RET} a second time
14936 after executing the command.
14940 Invoking the @code{signal} command is not the same as invoking the
14941 @code{kill} utility from the shell. Sending a signal with @code{kill}
14942 causes @value{GDBN} to decide what to do with the signal depending on
14943 the signal handling tables (@pxref{Signals}). The @code{signal} command
14944 passes the signal directly to your program.
14948 @section Returning from a Function
14951 @cindex returning from a function
14954 @itemx return @var{expression}
14955 You can cancel execution of a function call with the @code{return}
14956 command. If you give an
14957 @var{expression} argument, its value is used as the function's return
14961 When you use @code{return}, @value{GDBN} discards the selected stack frame
14962 (and all frames within it). You can think of this as making the
14963 discarded frame return prematurely. If you wish to specify a value to
14964 be returned, give that value as the argument to @code{return}.
14966 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14967 Frame}), and any other frames inside of it, leaving its caller as the
14968 innermost remaining frame. That frame becomes selected. The
14969 specified value is stored in the registers used for returning values
14972 The @code{return} command does not resume execution; it leaves the
14973 program stopped in the state that would exist if the function had just
14974 returned. In contrast, the @code{finish} command (@pxref{Continuing
14975 and Stepping, ,Continuing and Stepping}) resumes execution until the
14976 selected stack frame returns naturally.
14978 @value{GDBN} needs to know how the @var{expression} argument should be set for
14979 the inferior. The concrete registers assignment depends on the OS ABI and the
14980 type being returned by the selected stack frame. For example it is common for
14981 OS ABI to return floating point values in FPU registers while integer values in
14982 CPU registers. Still some ABIs return even floating point values in CPU
14983 registers. Larger integer widths (such as @code{long long int}) also have
14984 specific placement rules. @value{GDBN} already knows the OS ABI from its
14985 current target so it needs to find out also the type being returned to make the
14986 assignment into the right register(s).
14988 Normally, the selected stack frame has debug info. @value{GDBN} will always
14989 use the debug info instead of the implicit type of @var{expression} when the
14990 debug info is available. For example, if you type @kbd{return -1}, and the
14991 function in the current stack frame is declared to return a @code{long long
14992 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14993 into a @code{long long int}:
14996 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14998 (@value{GDBP}) return -1
14999 Make func return now? (y or n) y
15000 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15001 43 printf ("result=%lld\n", func ());
15005 However, if the selected stack frame does not have a debug info, e.g., if the
15006 function was compiled without debug info, @value{GDBN} has to find out the type
15007 to return from user. Specifying a different type by mistake may set the value
15008 in different inferior registers than the caller code expects. For example,
15009 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15010 of a @code{long long int} result for a debug info less function (on 32-bit
15011 architectures). Therefore the user is required to specify the return type by
15012 an appropriate cast explicitly:
15015 Breakpoint 2, 0x0040050b in func ()
15016 (@value{GDBP}) return -1
15017 Return value type not available for selected stack frame.
15018 Please use an explicit cast of the value to return.
15019 (@value{GDBP}) return (long long int) -1
15020 Make selected stack frame return now? (y or n) y
15021 #0 0x00400526 in main ()
15026 @section Calling Program Functions
15029 @cindex calling functions
15030 @cindex inferior functions, calling
15031 @item print @var{expr}
15032 Evaluate the expression @var{expr} and display the resulting value.
15033 @var{expr} may include calls to functions in the program being
15037 @item call @var{expr}
15038 Evaluate the expression @var{expr} without displaying @code{void}
15041 You can use this variant of the @code{print} command if you want to
15042 execute a function from your program that does not return anything
15043 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15044 with @code{void} returned values that @value{GDBN} will otherwise
15045 print. If the result is not void, it is printed and saved in the
15049 It is possible for the function you call via the @code{print} or
15050 @code{call} command to generate a signal (e.g., if there's a bug in
15051 the function, or if you passed it incorrect arguments). What happens
15052 in that case is controlled by the @code{set unwindonsignal} command.
15054 Similarly, with a C@t{++} program it is possible for the function you
15055 call via the @code{print} or @code{call} command to generate an
15056 exception that is not handled due to the constraints of the dummy
15057 frame. In this case, any exception that is raised in the frame, but has
15058 an out-of-frame exception handler will not be found. GDB builds a
15059 dummy-frame for the inferior function call, and the unwinder cannot
15060 seek for exception handlers outside of this dummy-frame. What happens
15061 in that case is controlled by the
15062 @code{set unwind-on-terminating-exception} command.
15065 @item set unwindonsignal
15066 @kindex set unwindonsignal
15067 @cindex unwind stack in called functions
15068 @cindex call dummy stack unwinding
15069 Set unwinding of the stack if a signal is received while in a function
15070 that @value{GDBN} called in the program being debugged. If set to on,
15071 @value{GDBN} unwinds the stack it created for the call and restores
15072 the context to what it was before the call. If set to off (the
15073 default), @value{GDBN} stops in the frame where the signal was
15076 @item show unwindonsignal
15077 @kindex show unwindonsignal
15078 Show the current setting of stack unwinding in the functions called by
15081 @item set unwind-on-terminating-exception
15082 @kindex set unwind-on-terminating-exception
15083 @cindex unwind stack in called functions with unhandled exceptions
15084 @cindex call dummy stack unwinding on unhandled exception.
15085 Set unwinding of the stack if a C@t{++} exception is raised, but left
15086 unhandled while in a function that @value{GDBN} called in the program being
15087 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15088 it created for the call and restores the context to what it was before
15089 the call. If set to off, @value{GDBN} the exception is delivered to
15090 the default C@t{++} exception handler and the inferior terminated.
15092 @item show unwind-on-terminating-exception
15093 @kindex show unwind-on-terminating-exception
15094 Show the current setting of stack unwinding in the functions called by
15099 @cindex weak alias functions
15100 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15101 for another function. In such case, @value{GDBN} might not pick up
15102 the type information, including the types of the function arguments,
15103 which causes @value{GDBN} to call the inferior function incorrectly.
15104 As a result, the called function will function erroneously and may
15105 even crash. A solution to that is to use the name of the aliased
15109 @section Patching Programs
15111 @cindex patching binaries
15112 @cindex writing into executables
15113 @cindex writing into corefiles
15115 By default, @value{GDBN} opens the file containing your program's
15116 executable code (or the corefile) read-only. This prevents accidental
15117 alterations to machine code; but it also prevents you from intentionally
15118 patching your program's binary.
15120 If you'd like to be able to patch the binary, you can specify that
15121 explicitly with the @code{set write} command. For example, you might
15122 want to turn on internal debugging flags, or even to make emergency
15128 @itemx set write off
15129 If you specify @samp{set write on}, @value{GDBN} opens executable and
15130 core files for both reading and writing; if you specify @kbd{set write
15131 off} (the default), @value{GDBN} opens them read-only.
15133 If you have already loaded a file, you must load it again (using the
15134 @code{exec-file} or @code{core-file} command) after changing @code{set
15135 write}, for your new setting to take effect.
15139 Display whether executable files and core files are opened for writing
15140 as well as reading.
15144 @chapter @value{GDBN} Files
15146 @value{GDBN} needs to know the file name of the program to be debugged,
15147 both in order to read its symbol table and in order to start your
15148 program. To debug a core dump of a previous run, you must also tell
15149 @value{GDBN} the name of the core dump file.
15152 * Files:: Commands to specify files
15153 * Separate Debug Files:: Debugging information in separate files
15154 * Index Files:: Index files speed up GDB
15155 * Symbol Errors:: Errors reading symbol files
15156 * Data Files:: GDB data files
15160 @section Commands to Specify Files
15162 @cindex symbol table
15163 @cindex core dump file
15165 You may want to specify executable and core dump file names. The usual
15166 way to do this is at start-up time, using the arguments to
15167 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15168 Out of @value{GDBN}}).
15170 Occasionally it is necessary to change to a different file during a
15171 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15172 specify a file you want to use. Or you are debugging a remote target
15173 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15174 Program}). In these situations the @value{GDBN} commands to specify
15175 new files are useful.
15178 @cindex executable file
15180 @item file @var{filename}
15181 Use @var{filename} as the program to be debugged. It is read for its
15182 symbols and for the contents of pure memory. It is also the program
15183 executed when you use the @code{run} command. If you do not specify a
15184 directory and the file is not found in the @value{GDBN} working directory,
15185 @value{GDBN} uses the environment variable @code{PATH} as a list of
15186 directories to search, just as the shell does when looking for a program
15187 to run. You can change the value of this variable, for both @value{GDBN}
15188 and your program, using the @code{path} command.
15190 @cindex unlinked object files
15191 @cindex patching object files
15192 You can load unlinked object @file{.o} files into @value{GDBN} using
15193 the @code{file} command. You will not be able to ``run'' an object
15194 file, but you can disassemble functions and inspect variables. Also,
15195 if the underlying BFD functionality supports it, you could use
15196 @kbd{gdb -write} to patch object files using this technique. Note
15197 that @value{GDBN} can neither interpret nor modify relocations in this
15198 case, so branches and some initialized variables will appear to go to
15199 the wrong place. But this feature is still handy from time to time.
15202 @code{file} with no argument makes @value{GDBN} discard any information it
15203 has on both executable file and the symbol table.
15206 @item exec-file @r{[} @var{filename} @r{]}
15207 Specify that the program to be run (but not the symbol table) is found
15208 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15209 if necessary to locate your program. Omitting @var{filename} means to
15210 discard information on the executable file.
15212 @kindex symbol-file
15213 @item symbol-file @r{[} @var{filename} @r{]}
15214 Read symbol table information from file @var{filename}. @code{PATH} is
15215 searched when necessary. Use the @code{file} command to get both symbol
15216 table and program to run from the same file.
15218 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15219 program's symbol table.
15221 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15222 some breakpoints and auto-display expressions. This is because they may
15223 contain pointers to the internal data recording symbols and data types,
15224 which are part of the old symbol table data being discarded inside
15227 @code{symbol-file} does not repeat if you press @key{RET} again after
15230 When @value{GDBN} is configured for a particular environment, it
15231 understands debugging information in whatever format is the standard
15232 generated for that environment; you may use either a @sc{gnu} compiler, or
15233 other compilers that adhere to the local conventions.
15234 Best results are usually obtained from @sc{gnu} compilers; for example,
15235 using @code{@value{NGCC}} you can generate debugging information for
15238 For most kinds of object files, with the exception of old SVR3 systems
15239 using COFF, the @code{symbol-file} command does not normally read the
15240 symbol table in full right away. Instead, it scans the symbol table
15241 quickly to find which source files and which symbols are present. The
15242 details are read later, one source file at a time, as they are needed.
15244 The purpose of this two-stage reading strategy is to make @value{GDBN}
15245 start up faster. For the most part, it is invisible except for
15246 occasional pauses while the symbol table details for a particular source
15247 file are being read. (The @code{set verbose} command can turn these
15248 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15249 Warnings and Messages}.)
15251 We have not implemented the two-stage strategy for COFF yet. When the
15252 symbol table is stored in COFF format, @code{symbol-file} reads the
15253 symbol table data in full right away. Note that ``stabs-in-COFF''
15254 still does the two-stage strategy, since the debug info is actually
15258 @cindex reading symbols immediately
15259 @cindex symbols, reading immediately
15260 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15261 @itemx file @r{[} -readnow @r{]} @var{filename}
15262 You can override the @value{GDBN} two-stage strategy for reading symbol
15263 tables by using the @samp{-readnow} option with any of the commands that
15264 load symbol table information, if you want to be sure @value{GDBN} has the
15265 entire symbol table available.
15267 @c FIXME: for now no mention of directories, since this seems to be in
15268 @c flux. 13mar1992 status is that in theory GDB would look either in
15269 @c current dir or in same dir as myprog; but issues like competing
15270 @c GDB's, or clutter in system dirs, mean that in practice right now
15271 @c only current dir is used. FFish says maybe a special GDB hierarchy
15272 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15276 @item core-file @r{[}@var{filename}@r{]}
15278 Specify the whereabouts of a core dump file to be used as the ``contents
15279 of memory''. Traditionally, core files contain only some parts of the
15280 address space of the process that generated them; @value{GDBN} can access the
15281 executable file itself for other parts.
15283 @code{core-file} with no argument specifies that no core file is
15286 Note that the core file is ignored when your program is actually running
15287 under @value{GDBN}. So, if you have been running your program and you
15288 wish to debug a core file instead, you must kill the subprocess in which
15289 the program is running. To do this, use the @code{kill} command
15290 (@pxref{Kill Process, ,Killing the Child Process}).
15292 @kindex add-symbol-file
15293 @cindex dynamic linking
15294 @item add-symbol-file @var{filename} @var{address}
15295 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15296 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15297 The @code{add-symbol-file} command reads additional symbol table
15298 information from the file @var{filename}. You would use this command
15299 when @var{filename} has been dynamically loaded (by some other means)
15300 into the program that is running. @var{address} should be the memory
15301 address at which the file has been loaded; @value{GDBN} cannot figure
15302 this out for itself. You can additionally specify an arbitrary number
15303 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15304 section name and base address for that section. You can specify any
15305 @var{address} as an expression.
15307 The symbol table of the file @var{filename} is added to the symbol table
15308 originally read with the @code{symbol-file} command. You can use the
15309 @code{add-symbol-file} command any number of times; the new symbol data
15310 thus read keeps adding to the old. To discard all old symbol data
15311 instead, use the @code{symbol-file} command without any arguments.
15313 @cindex relocatable object files, reading symbols from
15314 @cindex object files, relocatable, reading symbols from
15315 @cindex reading symbols from relocatable object files
15316 @cindex symbols, reading from relocatable object files
15317 @cindex @file{.o} files, reading symbols from
15318 Although @var{filename} is typically a shared library file, an
15319 executable file, or some other object file which has been fully
15320 relocated for loading into a process, you can also load symbolic
15321 information from relocatable @file{.o} files, as long as:
15325 the file's symbolic information refers only to linker symbols defined in
15326 that file, not to symbols defined by other object files,
15328 every section the file's symbolic information refers to has actually
15329 been loaded into the inferior, as it appears in the file, and
15331 you can determine the address at which every section was loaded, and
15332 provide these to the @code{add-symbol-file} command.
15336 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15337 relocatable files into an already running program; such systems
15338 typically make the requirements above easy to meet. However, it's
15339 important to recognize that many native systems use complex link
15340 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15341 assembly, for example) that make the requirements difficult to meet. In
15342 general, one cannot assume that using @code{add-symbol-file} to read a
15343 relocatable object file's symbolic information will have the same effect
15344 as linking the relocatable object file into the program in the normal
15347 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15349 @kindex add-symbol-file-from-memory
15350 @cindex @code{syscall DSO}
15351 @cindex load symbols from memory
15352 @item add-symbol-file-from-memory @var{address}
15353 Load symbols from the given @var{address} in a dynamically loaded
15354 object file whose image is mapped directly into the inferior's memory.
15355 For example, the Linux kernel maps a @code{syscall DSO} into each
15356 process's address space; this DSO provides kernel-specific code for
15357 some system calls. The argument can be any expression whose
15358 evaluation yields the address of the file's shared object file header.
15359 For this command to work, you must have used @code{symbol-file} or
15360 @code{exec-file} commands in advance.
15362 @kindex add-shared-symbol-files
15364 @item add-shared-symbol-files @var{library-file}
15365 @itemx assf @var{library-file}
15366 The @code{add-shared-symbol-files} command can currently be used only
15367 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15368 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15369 @value{GDBN} automatically looks for shared libraries, however if
15370 @value{GDBN} does not find yours, you can invoke
15371 @code{add-shared-symbol-files}. It takes one argument: the shared
15372 library's file name. @code{assf} is a shorthand alias for
15373 @code{add-shared-symbol-files}.
15376 @item section @var{section} @var{addr}
15377 The @code{section} command changes the base address of the named
15378 @var{section} of the exec file to @var{addr}. This can be used if the
15379 exec file does not contain section addresses, (such as in the
15380 @code{a.out} format), or when the addresses specified in the file
15381 itself are wrong. Each section must be changed separately. The
15382 @code{info files} command, described below, lists all the sections and
15386 @kindex info target
15389 @code{info files} and @code{info target} are synonymous; both print the
15390 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15391 including the names of the executable and core dump files currently in
15392 use by @value{GDBN}, and the files from which symbols were loaded. The
15393 command @code{help target} lists all possible targets rather than
15396 @kindex maint info sections
15397 @item maint info sections
15398 Another command that can give you extra information about program sections
15399 is @code{maint info sections}. In addition to the section information
15400 displayed by @code{info files}, this command displays the flags and file
15401 offset of each section in the executable and core dump files. In addition,
15402 @code{maint info sections} provides the following command options (which
15403 may be arbitrarily combined):
15407 Display sections for all loaded object files, including shared libraries.
15408 @item @var{sections}
15409 Display info only for named @var{sections}.
15410 @item @var{section-flags}
15411 Display info only for sections for which @var{section-flags} are true.
15412 The section flags that @value{GDBN} currently knows about are:
15415 Section will have space allocated in the process when loaded.
15416 Set for all sections except those containing debug information.
15418 Section will be loaded from the file into the child process memory.
15419 Set for pre-initialized code and data, clear for @code{.bss} sections.
15421 Section needs to be relocated before loading.
15423 Section cannot be modified by the child process.
15425 Section contains executable code only.
15427 Section contains data only (no executable code).
15429 Section will reside in ROM.
15431 Section contains data for constructor/destructor lists.
15433 Section is not empty.
15435 An instruction to the linker to not output the section.
15436 @item COFF_SHARED_LIBRARY
15437 A notification to the linker that the section contains
15438 COFF shared library information.
15440 Section contains common symbols.
15443 @kindex set trust-readonly-sections
15444 @cindex read-only sections
15445 @item set trust-readonly-sections on
15446 Tell @value{GDBN} that readonly sections in your object file
15447 really are read-only (i.e.@: that their contents will not change).
15448 In that case, @value{GDBN} can fetch values from these sections
15449 out of the object file, rather than from the target program.
15450 For some targets (notably embedded ones), this can be a significant
15451 enhancement to debugging performance.
15453 The default is off.
15455 @item set trust-readonly-sections off
15456 Tell @value{GDBN} not to trust readonly sections. This means that
15457 the contents of the section might change while the program is running,
15458 and must therefore be fetched from the target when needed.
15460 @item show trust-readonly-sections
15461 Show the current setting of trusting readonly sections.
15464 All file-specifying commands allow both absolute and relative file names
15465 as arguments. @value{GDBN} always converts the file name to an absolute file
15466 name and remembers it that way.
15468 @cindex shared libraries
15469 @anchor{Shared Libraries}
15470 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15471 and IBM RS/6000 AIX shared libraries.
15473 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15474 shared libraries. @xref{Expat}.
15476 @value{GDBN} automatically loads symbol definitions from shared libraries
15477 when you use the @code{run} command, or when you examine a core file.
15478 (Before you issue the @code{run} command, @value{GDBN} does not understand
15479 references to a function in a shared library, however---unless you are
15480 debugging a core file).
15482 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15483 automatically loads the symbols at the time of the @code{shl_load} call.
15485 @c FIXME: some @value{GDBN} release may permit some refs to undef
15486 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15487 @c FIXME...lib; check this from time to time when updating manual
15489 There are times, however, when you may wish to not automatically load
15490 symbol definitions from shared libraries, such as when they are
15491 particularly large or there are many of them.
15493 To control the automatic loading of shared library symbols, use the
15497 @kindex set auto-solib-add
15498 @item set auto-solib-add @var{mode}
15499 If @var{mode} is @code{on}, symbols from all shared object libraries
15500 will be loaded automatically when the inferior begins execution, you
15501 attach to an independently started inferior, or when the dynamic linker
15502 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15503 is @code{off}, symbols must be loaded manually, using the
15504 @code{sharedlibrary} command. The default value is @code{on}.
15506 @cindex memory used for symbol tables
15507 If your program uses lots of shared libraries with debug info that
15508 takes large amounts of memory, you can decrease the @value{GDBN}
15509 memory footprint by preventing it from automatically loading the
15510 symbols from shared libraries. To that end, type @kbd{set
15511 auto-solib-add off} before running the inferior, then load each
15512 library whose debug symbols you do need with @kbd{sharedlibrary
15513 @var{regexp}}, where @var{regexp} is a regular expression that matches
15514 the libraries whose symbols you want to be loaded.
15516 @kindex show auto-solib-add
15517 @item show auto-solib-add
15518 Display the current autoloading mode.
15521 @cindex load shared library
15522 To explicitly load shared library symbols, use the @code{sharedlibrary}
15526 @kindex info sharedlibrary
15528 @item info share @var{regex}
15529 @itemx info sharedlibrary @var{regex}
15530 Print the names of the shared libraries which are currently loaded
15531 that match @var{regex}. If @var{regex} is omitted then print
15532 all shared libraries that are loaded.
15534 @kindex sharedlibrary
15536 @item sharedlibrary @var{regex}
15537 @itemx share @var{regex}
15538 Load shared object library symbols for files matching a
15539 Unix regular expression.
15540 As with files loaded automatically, it only loads shared libraries
15541 required by your program for a core file or after typing @code{run}. If
15542 @var{regex} is omitted all shared libraries required by your program are
15545 @item nosharedlibrary
15546 @kindex nosharedlibrary
15547 @cindex unload symbols from shared libraries
15548 Unload all shared object library symbols. This discards all symbols
15549 that have been loaded from all shared libraries. Symbols from shared
15550 libraries that were loaded by explicit user requests are not
15554 Sometimes you may wish that @value{GDBN} stops and gives you control
15555 when any of shared library events happen. Use the @code{set
15556 stop-on-solib-events} command for this:
15559 @item set stop-on-solib-events
15560 @kindex set stop-on-solib-events
15561 This command controls whether @value{GDBN} should give you control
15562 when the dynamic linker notifies it about some shared library event.
15563 The most common event of interest is loading or unloading of a new
15566 @item show stop-on-solib-events
15567 @kindex show stop-on-solib-events
15568 Show whether @value{GDBN} stops and gives you control when shared
15569 library events happen.
15572 Shared libraries are also supported in many cross or remote debugging
15573 configurations. @value{GDBN} needs to have access to the target's libraries;
15574 this can be accomplished either by providing copies of the libraries
15575 on the host system, or by asking @value{GDBN} to automatically retrieve the
15576 libraries from the target. If copies of the target libraries are
15577 provided, they need to be the same as the target libraries, although the
15578 copies on the target can be stripped as long as the copies on the host are
15581 @cindex where to look for shared libraries
15582 For remote debugging, you need to tell @value{GDBN} where the target
15583 libraries are, so that it can load the correct copies---otherwise, it
15584 may try to load the host's libraries. @value{GDBN} has two variables
15585 to specify the search directories for target libraries.
15588 @cindex prefix for shared library file names
15589 @cindex system root, alternate
15590 @kindex set solib-absolute-prefix
15591 @kindex set sysroot
15592 @item set sysroot @var{path}
15593 Use @var{path} as the system root for the program being debugged. Any
15594 absolute shared library paths will be prefixed with @var{path}; many
15595 runtime loaders store the absolute paths to the shared library in the
15596 target program's memory. If you use @code{set sysroot} to find shared
15597 libraries, they need to be laid out in the same way that they are on
15598 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15601 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15602 retrieve the target libraries from the remote system. This is only
15603 supported when using a remote target that supports the @code{remote get}
15604 command (@pxref{File Transfer,,Sending files to a remote system}).
15605 The part of @var{path} following the initial @file{remote:}
15606 (if present) is used as system root prefix on the remote file system.
15607 @footnote{If you want to specify a local system root using a directory
15608 that happens to be named @file{remote:}, you need to use some equivalent
15609 variant of the name like @file{./remote:}.}
15611 For targets with an MS-DOS based filesystem, such as MS-Windows and
15612 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15613 absolute file name with @var{path}. But first, on Unix hosts,
15614 @value{GDBN} converts all backslash directory separators into forward
15615 slashes, because the backslash is not a directory separator on Unix:
15618 c:\foo\bar.dll @result{} c:/foo/bar.dll
15621 Then, @value{GDBN} attempts prefixing the target file name with
15622 @var{path}, and looks for the resulting file name in the host file
15626 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15629 If that does not find the shared library, @value{GDBN} tries removing
15630 the @samp{:} character from the drive spec, both for convenience, and,
15631 for the case of the host file system not supporting file names with
15635 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15638 This makes it possible to have a system root that mirrors a target
15639 with more than one drive. E.g., you may want to setup your local
15640 copies of the target system shared libraries like so (note @samp{c} vs
15644 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15645 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15646 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15650 and point the system root at @file{/path/to/sysroot}, so that
15651 @value{GDBN} can find the correct copies of both
15652 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15654 If that still does not find the shared library, @value{GDBN} tries
15655 removing the whole drive spec from the target file name:
15658 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15661 This last lookup makes it possible to not care about the drive name,
15662 if you don't want or need to.
15664 The @code{set solib-absolute-prefix} command is an alias for @code{set
15667 @cindex default system root
15668 @cindex @samp{--with-sysroot}
15669 You can set the default system root by using the configure-time
15670 @samp{--with-sysroot} option. If the system root is inside
15671 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15672 @samp{--exec-prefix}), then the default system root will be updated
15673 automatically if the installed @value{GDBN} is moved to a new
15676 @kindex show sysroot
15678 Display the current shared library prefix.
15680 @kindex set solib-search-path
15681 @item set solib-search-path @var{path}
15682 If this variable is set, @var{path} is a colon-separated list of
15683 directories to search for shared libraries. @samp{solib-search-path}
15684 is used after @samp{sysroot} fails to locate the library, or if the
15685 path to the library is relative instead of absolute. If you want to
15686 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15687 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15688 finding your host's libraries. @samp{sysroot} is preferred; setting
15689 it to a nonexistent directory may interfere with automatic loading
15690 of shared library symbols.
15692 @kindex show solib-search-path
15693 @item show solib-search-path
15694 Display the current shared library search path.
15696 @cindex DOS file-name semantics of file names.
15697 @kindex set target-file-system-kind (unix|dos-based|auto)
15698 @kindex show target-file-system-kind
15699 @item set target-file-system-kind @var{kind}
15700 Set assumed file system kind for target reported file names.
15702 Shared library file names as reported by the target system may not
15703 make sense as is on the system @value{GDBN} is running on. For
15704 example, when remote debugging a target that has MS-DOS based file
15705 system semantics, from a Unix host, the target may be reporting to
15706 @value{GDBN} a list of loaded shared libraries with file names such as
15707 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15708 drive letters, so the @samp{c:\} prefix is not normally understood as
15709 indicating an absolute file name, and neither is the backslash
15710 normally considered a directory separator character. In that case,
15711 the native file system would interpret this whole absolute file name
15712 as a relative file name with no directory components. This would make
15713 it impossible to point @value{GDBN} at a copy of the remote target's
15714 shared libraries on the host using @code{set sysroot}, and impractical
15715 with @code{set solib-search-path}. Setting
15716 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15717 to interpret such file names similarly to how the target would, and to
15718 map them to file names valid on @value{GDBN}'s native file system
15719 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15720 to one of the supported file system kinds. In that case, @value{GDBN}
15721 tries to determine the appropriate file system variant based on the
15722 current target's operating system (@pxref{ABI, ,Configuring the
15723 Current ABI}). The supported file system settings are:
15727 Instruct @value{GDBN} to assume the target file system is of Unix
15728 kind. Only file names starting the forward slash (@samp{/}) character
15729 are considered absolute, and the directory separator character is also
15733 Instruct @value{GDBN} to assume the target file system is DOS based.
15734 File names starting with either a forward slash, or a drive letter
15735 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15736 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15737 considered directory separators.
15740 Instruct @value{GDBN} to use the file system kind associated with the
15741 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15742 This is the default.
15746 @cindex file name canonicalization
15747 @cindex base name differences
15748 When processing file names provided by the user, @value{GDBN}
15749 frequently needs to compare them to the file names recorded in the
15750 program's debug info. Normally, @value{GDBN} compares just the
15751 @dfn{base names} of the files as strings, which is reasonably fast
15752 even for very large programs. (The base name of a file is the last
15753 portion of its name, after stripping all the leading directories.)
15754 This shortcut in comparison is based upon the assumption that files
15755 cannot have more than one base name. This is usually true, but
15756 references to files that use symlinks or similar filesystem
15757 facilities violate that assumption. If your program records files
15758 using such facilities, or if you provide file names to @value{GDBN}
15759 using symlinks etc., you can set @code{basenames-may-differ} to
15760 @code{true} to instruct @value{GDBN} to completely canonicalize each
15761 pair of file names it needs to compare. This will make file-name
15762 comparisons accurate, but at a price of a significant slowdown.
15765 @item set basenames-may-differ
15766 @kindex set basenames-may-differ
15767 Set whether a source file may have multiple base names.
15769 @item show basenames-may-differ
15770 @kindex show basenames-may-differ
15771 Show whether a source file may have multiple base names.
15774 @node Separate Debug Files
15775 @section Debugging Information in Separate Files
15776 @cindex separate debugging information files
15777 @cindex debugging information in separate files
15778 @cindex @file{.debug} subdirectories
15779 @cindex debugging information directory, global
15780 @cindex global debugging information directory
15781 @cindex build ID, and separate debugging files
15782 @cindex @file{.build-id} directory
15784 @value{GDBN} allows you to put a program's debugging information in a
15785 file separate from the executable itself, in a way that allows
15786 @value{GDBN} to find and load the debugging information automatically.
15787 Since debugging information can be very large---sometimes larger
15788 than the executable code itself---some systems distribute debugging
15789 information for their executables in separate files, which users can
15790 install only when they need to debug a problem.
15792 @value{GDBN} supports two ways of specifying the separate debug info
15797 The executable contains a @dfn{debug link} that specifies the name of
15798 the separate debug info file. The separate debug file's name is
15799 usually @file{@var{executable}.debug}, where @var{executable} is the
15800 name of the corresponding executable file without leading directories
15801 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15802 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15803 checksum for the debug file, which @value{GDBN} uses to validate that
15804 the executable and the debug file came from the same build.
15807 The executable contains a @dfn{build ID}, a unique bit string that is
15808 also present in the corresponding debug info file. (This is supported
15809 only on some operating systems, notably those which use the ELF format
15810 for binary files and the @sc{gnu} Binutils.) For more details about
15811 this feature, see the description of the @option{--build-id}
15812 command-line option in @ref{Options, , Command Line Options, ld.info,
15813 The GNU Linker}. The debug info file's name is not specified
15814 explicitly by the build ID, but can be computed from the build ID, see
15818 Depending on the way the debug info file is specified, @value{GDBN}
15819 uses two different methods of looking for the debug file:
15823 For the ``debug link'' method, @value{GDBN} looks up the named file in
15824 the directory of the executable file, then in a subdirectory of that
15825 directory named @file{.debug}, and finally under the global debug
15826 directory, in a subdirectory whose name is identical to the leading
15827 directories of the executable's absolute file name.
15830 For the ``build ID'' method, @value{GDBN} looks in the
15831 @file{.build-id} subdirectory of the global debug directory for a file
15832 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15833 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15834 are the rest of the bit string. (Real build ID strings are 32 or more
15835 hex characters, not 10.)
15838 So, for example, suppose you ask @value{GDBN} to debug
15839 @file{/usr/bin/ls}, which has a debug link that specifies the
15840 file @file{ls.debug}, and a build ID whose value in hex is
15841 @code{abcdef1234}. If the global debug directory is
15842 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15843 debug information files, in the indicated order:
15847 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15849 @file{/usr/bin/ls.debug}
15851 @file{/usr/bin/.debug/ls.debug}
15853 @file{/usr/lib/debug/usr/bin/ls.debug}.
15856 You can set the global debugging info directory's name, and view the
15857 name @value{GDBN} is currently using.
15861 @kindex set debug-file-directory
15862 @item set debug-file-directory @var{directories}
15863 Set the directories which @value{GDBN} searches for separate debugging
15864 information files to @var{directory}. Multiple directory components can be set
15865 concatenating them by a directory separator.
15867 @kindex show debug-file-directory
15868 @item show debug-file-directory
15869 Show the directories @value{GDBN} searches for separate debugging
15874 @cindex @code{.gnu_debuglink} sections
15875 @cindex debug link sections
15876 A debug link is a special section of the executable file named
15877 @code{.gnu_debuglink}. The section must contain:
15881 A filename, with any leading directory components removed, followed by
15884 zero to three bytes of padding, as needed to reach the next four-byte
15885 boundary within the section, and
15887 a four-byte CRC checksum, stored in the same endianness used for the
15888 executable file itself. The checksum is computed on the debugging
15889 information file's full contents by the function given below, passing
15890 zero as the @var{crc} argument.
15893 Any executable file format can carry a debug link, as long as it can
15894 contain a section named @code{.gnu_debuglink} with the contents
15897 @cindex @code{.note.gnu.build-id} sections
15898 @cindex build ID sections
15899 The build ID is a special section in the executable file (and in other
15900 ELF binary files that @value{GDBN} may consider). This section is
15901 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15902 It contains unique identification for the built files---the ID remains
15903 the same across multiple builds of the same build tree. The default
15904 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15905 content for the build ID string. The same section with an identical
15906 value is present in the original built binary with symbols, in its
15907 stripped variant, and in the separate debugging information file.
15909 The debugging information file itself should be an ordinary
15910 executable, containing a full set of linker symbols, sections, and
15911 debugging information. The sections of the debugging information file
15912 should have the same names, addresses, and sizes as the original file,
15913 but they need not contain any data---much like a @code{.bss} section
15914 in an ordinary executable.
15916 The @sc{gnu} binary utilities (Binutils) package includes the
15917 @samp{objcopy} utility that can produce
15918 the separated executable / debugging information file pairs using the
15919 following commands:
15922 @kbd{objcopy --only-keep-debug foo foo.debug}
15927 These commands remove the debugging
15928 information from the executable file @file{foo} and place it in the file
15929 @file{foo.debug}. You can use the first, second or both methods to link the
15934 The debug link method needs the following additional command to also leave
15935 behind a debug link in @file{foo}:
15938 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15941 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15942 a version of the @code{strip} command such that the command @kbd{strip foo -f
15943 foo.debug} has the same functionality as the two @code{objcopy} commands and
15944 the @code{ln -s} command above, together.
15947 Build ID gets embedded into the main executable using @code{ld --build-id} or
15948 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15949 compatibility fixes for debug files separation are present in @sc{gnu} binary
15950 utilities (Binutils) package since version 2.18.
15955 @cindex CRC algorithm definition
15956 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15957 IEEE 802.3 using the polynomial:
15959 @c TexInfo requires naked braces for multi-digit exponents for Tex
15960 @c output, but this causes HTML output to barf. HTML has to be set using
15961 @c raw commands. So we end up having to specify this equation in 2
15966 <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>
15967 + <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
15973 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15974 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15978 The function is computed byte at a time, taking the least
15979 significant bit of each byte first. The initial pattern
15980 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15981 the final result is inverted to ensure trailing zeros also affect the
15984 @emph{Note:} This is the same CRC polynomial as used in handling the
15985 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15986 , @value{GDBN} Remote Serial Protocol}). However in the
15987 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15988 significant bit first, and the result is not inverted, so trailing
15989 zeros have no effect on the CRC value.
15991 To complete the description, we show below the code of the function
15992 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15993 initially supplied @code{crc} argument means that an initial call to
15994 this function passing in zero will start computing the CRC using
15997 @kindex gnu_debuglink_crc32
16000 gnu_debuglink_crc32 (unsigned long crc,
16001 unsigned char *buf, size_t len)
16003 static const unsigned long crc32_table[256] =
16005 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16006 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16007 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16008 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16009 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16010 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16011 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16012 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16013 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16014 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16015 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16016 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16017 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16018 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16019 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16020 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16021 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16022 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16023 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16024 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16025 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16026 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16027 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16028 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16029 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16030 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16031 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16032 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16033 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16034 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16035 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16036 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16037 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16038 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16039 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16040 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16041 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16042 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16043 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16044 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16045 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16046 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16047 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16048 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16049 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16050 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16051 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16052 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16053 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16054 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16055 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16058 unsigned char *end;
16060 crc = ~crc & 0xffffffff;
16061 for (end = buf + len; buf < end; ++buf)
16062 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16063 return ~crc & 0xffffffff;
16068 This computation does not apply to the ``build ID'' method.
16072 @section Index Files Speed Up @value{GDBN}
16073 @cindex index files
16074 @cindex @samp{.gdb_index} section
16076 When @value{GDBN} finds a symbol file, it scans the symbols in the
16077 file in order to construct an internal symbol table. This lets most
16078 @value{GDBN} operations work quickly---at the cost of a delay early
16079 on. For large programs, this delay can be quite lengthy, so
16080 @value{GDBN} provides a way to build an index, which speeds up
16083 The index is stored as a section in the symbol file. @value{GDBN} can
16084 write the index to a file, then you can put it into the symbol file
16085 using @command{objcopy}.
16087 To create an index file, use the @code{save gdb-index} command:
16090 @item save gdb-index @var{directory}
16091 @kindex save gdb-index
16092 Create an index file for each symbol file currently known by
16093 @value{GDBN}. Each file is named after its corresponding symbol file,
16094 with @samp{.gdb-index} appended, and is written into the given
16098 Once you have created an index file you can merge it into your symbol
16099 file, here named @file{symfile}, using @command{objcopy}:
16102 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16103 --set-section-flags .gdb_index=readonly symfile symfile
16106 There are currently some limitation on indices. They only work when
16107 for DWARF debugging information, not stabs. And, they do not
16108 currently work for programs using Ada.
16110 @node Symbol Errors
16111 @section Errors Reading Symbol Files
16113 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16114 such as symbol types it does not recognize, or known bugs in compiler
16115 output. By default, @value{GDBN} does not notify you of such problems, since
16116 they are relatively common and primarily of interest to people
16117 debugging compilers. If you are interested in seeing information
16118 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16119 only one message about each such type of problem, no matter how many
16120 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16121 to see how many times the problems occur, with the @code{set
16122 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16125 The messages currently printed, and their meanings, include:
16128 @item inner block not inside outer block in @var{symbol}
16130 The symbol information shows where symbol scopes begin and end
16131 (such as at the start of a function or a block of statements). This
16132 error indicates that an inner scope block is not fully contained
16133 in its outer scope blocks.
16135 @value{GDBN} circumvents the problem by treating the inner block as if it had
16136 the same scope as the outer block. In the error message, @var{symbol}
16137 may be shown as ``@code{(don't know)}'' if the outer block is not a
16140 @item block at @var{address} out of order
16142 The symbol information for symbol scope blocks should occur in
16143 order of increasing addresses. This error indicates that it does not
16146 @value{GDBN} does not circumvent this problem, and has trouble
16147 locating symbols in the source file whose symbols it is reading. (You
16148 can often determine what source file is affected by specifying
16149 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16152 @item bad block start address patched
16154 The symbol information for a symbol scope block has a start address
16155 smaller than the address of the preceding source line. This is known
16156 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16158 @value{GDBN} circumvents the problem by treating the symbol scope block as
16159 starting on the previous source line.
16161 @item bad string table offset in symbol @var{n}
16164 Symbol number @var{n} contains a pointer into the string table which is
16165 larger than the size of the string table.
16167 @value{GDBN} circumvents the problem by considering the symbol to have the
16168 name @code{foo}, which may cause other problems if many symbols end up
16171 @item unknown symbol type @code{0x@var{nn}}
16173 The symbol information contains new data types that @value{GDBN} does
16174 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16175 uncomprehended information, in hexadecimal.
16177 @value{GDBN} circumvents the error by ignoring this symbol information.
16178 This usually allows you to debug your program, though certain symbols
16179 are not accessible. If you encounter such a problem and feel like
16180 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16181 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16182 and examine @code{*bufp} to see the symbol.
16184 @item stub type has NULL name
16186 @value{GDBN} could not find the full definition for a struct or class.
16188 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16189 The symbol information for a C@t{++} member function is missing some
16190 information that recent versions of the compiler should have output for
16193 @item info mismatch between compiler and debugger
16195 @value{GDBN} could not parse a type specification output by the compiler.
16200 @section GDB Data Files
16202 @cindex prefix for data files
16203 @value{GDBN} will sometimes read an auxiliary data file. These files
16204 are kept in a directory known as the @dfn{data directory}.
16206 You can set the data directory's name, and view the name @value{GDBN}
16207 is currently using.
16210 @kindex set data-directory
16211 @item set data-directory @var{directory}
16212 Set the directory which @value{GDBN} searches for auxiliary data files
16213 to @var{directory}.
16215 @kindex show data-directory
16216 @item show data-directory
16217 Show the directory @value{GDBN} searches for auxiliary data files.
16220 @cindex default data directory
16221 @cindex @samp{--with-gdb-datadir}
16222 You can set the default data directory by using the configure-time
16223 @samp{--with-gdb-datadir} option. If the data directory is inside
16224 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16225 @samp{--exec-prefix}), then the default data directory will be updated
16226 automatically if the installed @value{GDBN} is moved to a new
16229 The data directory may also be specified with the
16230 @code{--data-directory} command line option.
16231 @xref{Mode Options}.
16234 @chapter Specifying a Debugging Target
16236 @cindex debugging target
16237 A @dfn{target} is the execution environment occupied by your program.
16239 Often, @value{GDBN} runs in the same host environment as your program;
16240 in that case, the debugging target is specified as a side effect when
16241 you use the @code{file} or @code{core} commands. When you need more
16242 flexibility---for example, running @value{GDBN} on a physically separate
16243 host, or controlling a standalone system over a serial port or a
16244 realtime system over a TCP/IP connection---you can use the @code{target}
16245 command to specify one of the target types configured for @value{GDBN}
16246 (@pxref{Target Commands, ,Commands for Managing Targets}).
16248 @cindex target architecture
16249 It is possible to build @value{GDBN} for several different @dfn{target
16250 architectures}. When @value{GDBN} is built like that, you can choose
16251 one of the available architectures with the @kbd{set architecture}
16255 @kindex set architecture
16256 @kindex show architecture
16257 @item set architecture @var{arch}
16258 This command sets the current target architecture to @var{arch}. The
16259 value of @var{arch} can be @code{"auto"}, in addition to one of the
16260 supported architectures.
16262 @item show architecture
16263 Show the current target architecture.
16265 @item set processor
16267 @kindex set processor
16268 @kindex show processor
16269 These are alias commands for, respectively, @code{set architecture}
16270 and @code{show architecture}.
16274 * Active Targets:: Active targets
16275 * Target Commands:: Commands for managing targets
16276 * Byte Order:: Choosing target byte order
16279 @node Active Targets
16280 @section Active Targets
16282 @cindex stacking targets
16283 @cindex active targets
16284 @cindex multiple targets
16286 There are multiple classes of targets such as: processes, executable files or
16287 recording sessions. Core files belong to the process class, making core file
16288 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16289 on multiple active targets, one in each class. This allows you to (for
16290 example) start a process and inspect its activity, while still having access to
16291 the executable file after the process finishes. Or if you start process
16292 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16293 presented a virtual layer of the recording target, while the process target
16294 remains stopped at the chronologically last point of the process execution.
16296 Use the @code{core-file} and @code{exec-file} commands to select a new core
16297 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16298 specify as a target a process that is already running, use the @code{attach}
16299 command (@pxref{Attach, ,Debugging an Already-running Process}).
16301 @node Target Commands
16302 @section Commands for Managing Targets
16305 @item target @var{type} @var{parameters}
16306 Connects the @value{GDBN} host environment to a target machine or
16307 process. A target is typically a protocol for talking to debugging
16308 facilities. You use the argument @var{type} to specify the type or
16309 protocol of the target machine.
16311 Further @var{parameters} are interpreted by the target protocol, but
16312 typically include things like device names or host names to connect
16313 with, process numbers, and baud rates.
16315 The @code{target} command does not repeat if you press @key{RET} again
16316 after executing the command.
16318 @kindex help target
16320 Displays the names of all targets available. To display targets
16321 currently selected, use either @code{info target} or @code{info files}
16322 (@pxref{Files, ,Commands to Specify Files}).
16324 @item help target @var{name}
16325 Describe a particular target, including any parameters necessary to
16328 @kindex set gnutarget
16329 @item set gnutarget @var{args}
16330 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16331 knows whether it is reading an @dfn{executable},
16332 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16333 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16334 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16337 @emph{Warning:} To specify a file format with @code{set gnutarget},
16338 you must know the actual BFD name.
16342 @xref{Files, , Commands to Specify Files}.
16344 @kindex show gnutarget
16345 @item show gnutarget
16346 Use the @code{show gnutarget} command to display what file format
16347 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16348 @value{GDBN} will determine the file format for each file automatically,
16349 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16352 @cindex common targets
16353 Here are some common targets (available, or not, depending on the GDB
16358 @item target exec @var{program}
16359 @cindex executable file target
16360 An executable file. @samp{target exec @var{program}} is the same as
16361 @samp{exec-file @var{program}}.
16363 @item target core @var{filename}
16364 @cindex core dump file target
16365 A core dump file. @samp{target core @var{filename}} is the same as
16366 @samp{core-file @var{filename}}.
16368 @item target remote @var{medium}
16369 @cindex remote target
16370 A remote system connected to @value{GDBN} via a serial line or network
16371 connection. This command tells @value{GDBN} to use its own remote
16372 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16374 For example, if you have a board connected to @file{/dev/ttya} on the
16375 machine running @value{GDBN}, you could say:
16378 target remote /dev/ttya
16381 @code{target remote} supports the @code{load} command. This is only
16382 useful if you have some other way of getting the stub to the target
16383 system, and you can put it somewhere in memory where it won't get
16384 clobbered by the download.
16386 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16387 @cindex built-in simulator target
16388 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16396 works; however, you cannot assume that a specific memory map, device
16397 drivers, or even basic I/O is available, although some simulators do
16398 provide these. For info about any processor-specific simulator details,
16399 see the appropriate section in @ref{Embedded Processors, ,Embedded
16404 Some configurations may include these targets as well:
16408 @item target nrom @var{dev}
16409 @cindex NetROM ROM emulator target
16410 NetROM ROM emulator. This target only supports downloading.
16414 Different targets are available on different configurations of @value{GDBN};
16415 your configuration may have more or fewer targets.
16417 Many remote targets require you to download the executable's code once
16418 you've successfully established a connection. You may wish to control
16419 various aspects of this process.
16424 @kindex set hash@r{, for remote monitors}
16425 @cindex hash mark while downloading
16426 This command controls whether a hash mark @samp{#} is displayed while
16427 downloading a file to the remote monitor. If on, a hash mark is
16428 displayed after each S-record is successfully downloaded to the
16432 @kindex show hash@r{, for remote monitors}
16433 Show the current status of displaying the hash mark.
16435 @item set debug monitor
16436 @kindex set debug monitor
16437 @cindex display remote monitor communications
16438 Enable or disable display of communications messages between
16439 @value{GDBN} and the remote monitor.
16441 @item show debug monitor
16442 @kindex show debug monitor
16443 Show the current status of displaying communications between
16444 @value{GDBN} and the remote monitor.
16449 @kindex load @var{filename}
16450 @item load @var{filename}
16452 Depending on what remote debugging facilities are configured into
16453 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16454 is meant to make @var{filename} (an executable) available for debugging
16455 on the remote system---by downloading, or dynamic linking, for example.
16456 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16457 the @code{add-symbol-file} command.
16459 If your @value{GDBN} does not have a @code{load} command, attempting to
16460 execute it gets the error message ``@code{You can't do that when your
16461 target is @dots{}}''
16463 The file is loaded at whatever address is specified in the executable.
16464 For some object file formats, you can specify the load address when you
16465 link the program; for other formats, like a.out, the object file format
16466 specifies a fixed address.
16467 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16469 Depending on the remote side capabilities, @value{GDBN} may be able to
16470 load programs into flash memory.
16472 @code{load} does not repeat if you press @key{RET} again after using it.
16476 @section Choosing Target Byte Order
16478 @cindex choosing target byte order
16479 @cindex target byte order
16481 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16482 offer the ability to run either big-endian or little-endian byte
16483 orders. Usually the executable or symbol will include a bit to
16484 designate the endian-ness, and you will not need to worry about
16485 which to use. However, you may still find it useful to adjust
16486 @value{GDBN}'s idea of processor endian-ness manually.
16490 @item set endian big
16491 Instruct @value{GDBN} to assume the target is big-endian.
16493 @item set endian little
16494 Instruct @value{GDBN} to assume the target is little-endian.
16496 @item set endian auto
16497 Instruct @value{GDBN} to use the byte order associated with the
16501 Display @value{GDBN}'s current idea of the target byte order.
16505 Note that these commands merely adjust interpretation of symbolic
16506 data on the host, and that they have absolutely no effect on the
16510 @node Remote Debugging
16511 @chapter Debugging Remote Programs
16512 @cindex remote debugging
16514 If you are trying to debug a program running on a machine that cannot run
16515 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16516 For example, you might use remote debugging on an operating system kernel,
16517 or on a small system which does not have a general purpose operating system
16518 powerful enough to run a full-featured debugger.
16520 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16521 to make this work with particular debugging targets. In addition,
16522 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16523 but not specific to any particular target system) which you can use if you
16524 write the remote stubs---the code that runs on the remote system to
16525 communicate with @value{GDBN}.
16527 Other remote targets may be available in your
16528 configuration of @value{GDBN}; use @code{help target} to list them.
16531 * Connecting:: Connecting to a remote target
16532 * File Transfer:: Sending files to a remote system
16533 * Server:: Using the gdbserver program
16534 * Remote Configuration:: Remote configuration
16535 * Remote Stub:: Implementing a remote stub
16539 @section Connecting to a Remote Target
16541 On the @value{GDBN} host machine, you will need an unstripped copy of
16542 your program, since @value{GDBN} needs symbol and debugging information.
16543 Start up @value{GDBN} as usual, using the name of the local copy of your
16544 program as the first argument.
16546 @cindex @code{target remote}
16547 @value{GDBN} can communicate with the target over a serial line, or
16548 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16549 each case, @value{GDBN} uses the same protocol for debugging your
16550 program; only the medium carrying the debugging packets varies. The
16551 @code{target remote} command establishes a connection to the target.
16552 Its arguments indicate which medium to use:
16556 @item target remote @var{serial-device}
16557 @cindex serial line, @code{target remote}
16558 Use @var{serial-device} to communicate with the target. For example,
16559 to use a serial line connected to the device named @file{/dev/ttyb}:
16562 target remote /dev/ttyb
16565 If you're using a serial line, you may want to give @value{GDBN} the
16566 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16567 (@pxref{Remote Configuration, set remotebaud}) before the
16568 @code{target} command.
16570 @item target remote @code{@var{host}:@var{port}}
16571 @itemx target remote @code{tcp:@var{host}:@var{port}}
16572 @cindex @acronym{TCP} port, @code{target remote}
16573 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16574 The @var{host} may be either a host name or a numeric @acronym{IP}
16575 address; @var{port} must be a decimal number. The @var{host} could be
16576 the target machine itself, if it is directly connected to the net, or
16577 it might be a terminal server which in turn has a serial line to the
16580 For example, to connect to port 2828 on a terminal server named
16584 target remote manyfarms:2828
16587 If your remote target is actually running on the same machine as your
16588 debugger session (e.g.@: a simulator for your target running on the
16589 same host), you can omit the hostname. For example, to connect to
16590 port 1234 on your local machine:
16593 target remote :1234
16597 Note that the colon is still required here.
16599 @item target remote @code{udp:@var{host}:@var{port}}
16600 @cindex @acronym{UDP} port, @code{target remote}
16601 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16602 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16605 target remote udp:manyfarms:2828
16608 When using a @acronym{UDP} connection for remote debugging, you should
16609 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16610 can silently drop packets on busy or unreliable networks, which will
16611 cause havoc with your debugging session.
16613 @item target remote | @var{command}
16614 @cindex pipe, @code{target remote} to
16615 Run @var{command} in the background and communicate with it using a
16616 pipe. The @var{command} is a shell command, to be parsed and expanded
16617 by the system's command shell, @code{/bin/sh}; it should expect remote
16618 protocol packets on its standard input, and send replies on its
16619 standard output. You could use this to run a stand-alone simulator
16620 that speaks the remote debugging protocol, to make net connections
16621 using programs like @code{ssh}, or for other similar tricks.
16623 If @var{command} closes its standard output (perhaps by exiting),
16624 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16625 program has already exited, this will have no effect.)
16629 Once the connection has been established, you can use all the usual
16630 commands to examine and change data. The remote program is already
16631 running; you can use @kbd{step} and @kbd{continue}, and you do not
16632 need to use @kbd{run}.
16634 @cindex interrupting remote programs
16635 @cindex remote programs, interrupting
16636 Whenever @value{GDBN} is waiting for the remote program, if you type the
16637 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16638 program. This may or may not succeed, depending in part on the hardware
16639 and the serial drivers the remote system uses. If you type the
16640 interrupt character once again, @value{GDBN} displays this prompt:
16643 Interrupted while waiting for the program.
16644 Give up (and stop debugging it)? (y or n)
16647 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16648 (If you decide you want to try again later, you can use @samp{target
16649 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16650 goes back to waiting.
16653 @kindex detach (remote)
16655 When you have finished debugging the remote program, you can use the
16656 @code{detach} command to release it from @value{GDBN} control.
16657 Detaching from the target normally resumes its execution, but the results
16658 will depend on your particular remote stub. After the @code{detach}
16659 command, @value{GDBN} is free to connect to another target.
16663 The @code{disconnect} command behaves like @code{detach}, except that
16664 the target is generally not resumed. It will wait for @value{GDBN}
16665 (this instance or another one) to connect and continue debugging. After
16666 the @code{disconnect} command, @value{GDBN} is again free to connect to
16669 @cindex send command to remote monitor
16670 @cindex extend @value{GDBN} for remote targets
16671 @cindex add new commands for external monitor
16673 @item monitor @var{cmd}
16674 This command allows you to send arbitrary commands directly to the
16675 remote monitor. Since @value{GDBN} doesn't care about the commands it
16676 sends like this, this command is the way to extend @value{GDBN}---you
16677 can add new commands that only the external monitor will understand
16681 @node File Transfer
16682 @section Sending files to a remote system
16683 @cindex remote target, file transfer
16684 @cindex file transfer
16685 @cindex sending files to remote systems
16687 Some remote targets offer the ability to transfer files over the same
16688 connection used to communicate with @value{GDBN}. This is convenient
16689 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16690 running @code{gdbserver} over a network interface. For other targets,
16691 e.g.@: embedded devices with only a single serial port, this may be
16692 the only way to upload or download files.
16694 Not all remote targets support these commands.
16698 @item remote put @var{hostfile} @var{targetfile}
16699 Copy file @var{hostfile} from the host system (the machine running
16700 @value{GDBN}) to @var{targetfile} on the target system.
16703 @item remote get @var{targetfile} @var{hostfile}
16704 Copy file @var{targetfile} from the target system to @var{hostfile}
16705 on the host system.
16707 @kindex remote delete
16708 @item remote delete @var{targetfile}
16709 Delete @var{targetfile} from the target system.
16714 @section Using the @code{gdbserver} Program
16717 @cindex remote connection without stubs
16718 @code{gdbserver} is a control program for Unix-like systems, which
16719 allows you to connect your program with a remote @value{GDBN} via
16720 @code{target remote}---but without linking in the usual debugging stub.
16722 @code{gdbserver} is not a complete replacement for the debugging stubs,
16723 because it requires essentially the same operating-system facilities
16724 that @value{GDBN} itself does. In fact, a system that can run
16725 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16726 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16727 because it is a much smaller program than @value{GDBN} itself. It is
16728 also easier to port than all of @value{GDBN}, so you may be able to get
16729 started more quickly on a new system by using @code{gdbserver}.
16730 Finally, if you develop code for real-time systems, you may find that
16731 the tradeoffs involved in real-time operation make it more convenient to
16732 do as much development work as possible on another system, for example
16733 by cross-compiling. You can use @code{gdbserver} to make a similar
16734 choice for debugging.
16736 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16737 or a TCP connection, using the standard @value{GDBN} remote serial
16741 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16742 Do not run @code{gdbserver} connected to any public network; a
16743 @value{GDBN} connection to @code{gdbserver} provides access to the
16744 target system with the same privileges as the user running
16748 @subsection Running @code{gdbserver}
16749 @cindex arguments, to @code{gdbserver}
16750 @cindex @code{gdbserver}, command-line arguments
16752 Run @code{gdbserver} on the target system. You need a copy of the
16753 program you want to debug, including any libraries it requires.
16754 @code{gdbserver} does not need your program's symbol table, so you can
16755 strip the program if necessary to save space. @value{GDBN} on the host
16756 system does all the symbol handling.
16758 To use the server, you must tell it how to communicate with @value{GDBN};
16759 the name of your program; and the arguments for your program. The usual
16763 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16766 @var{comm} is either a device name (to use a serial line), or a TCP
16767 hostname and portnumber, or @code{-} or @code{stdio} to use
16768 stdin/stdout of @code{gdbserver}.
16769 For example, to debug Emacs with the argument
16770 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16774 target> gdbserver /dev/com1 emacs foo.txt
16777 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16780 To use a TCP connection instead of a serial line:
16783 target> gdbserver host:2345 emacs foo.txt
16786 The only difference from the previous example is the first argument,
16787 specifying that you are communicating with the host @value{GDBN} via
16788 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16789 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16790 (Currently, the @samp{host} part is ignored.) You can choose any number
16791 you want for the port number as long as it does not conflict with any
16792 TCP ports already in use on the target system (for example, @code{23} is
16793 reserved for @code{telnet}).@footnote{If you choose a port number that
16794 conflicts with another service, @code{gdbserver} prints an error message
16795 and exits.} You must use the same port number with the host @value{GDBN}
16796 @code{target remote} command.
16798 The @code{stdio} connection is useful when starting @code{gdbserver}
16802 (gdb) target remote | ssh -T hostname gdbserver - hello
16805 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16806 and we don't want escape-character handling. Ssh does this by default when
16807 a command is provided, the flag is provided to make it explicit.
16808 You could elide it if you want to.
16810 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16811 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16812 display through a pipe connected to gdbserver.
16813 Both @code{stdout} and @code{stderr} use the same pipe.
16815 @subsubsection Attaching to a Running Program
16816 @cindex attach to a program, @code{gdbserver}
16817 @cindex @option{--attach}, @code{gdbserver} option
16819 On some targets, @code{gdbserver} can also attach to running programs.
16820 This is accomplished via the @code{--attach} argument. The syntax is:
16823 target> gdbserver --attach @var{comm} @var{pid}
16826 @var{pid} is the process ID of a currently running process. It isn't necessary
16827 to point @code{gdbserver} at a binary for the running process.
16830 You can debug processes by name instead of process ID if your target has the
16831 @code{pidof} utility:
16834 target> gdbserver --attach @var{comm} `pidof @var{program}`
16837 In case more than one copy of @var{program} is running, or @var{program}
16838 has multiple threads, most versions of @code{pidof} support the
16839 @code{-s} option to only return the first process ID.
16841 @subsubsection Multi-Process Mode for @code{gdbserver}
16842 @cindex @code{gdbserver}, multiple processes
16843 @cindex multiple processes with @code{gdbserver}
16845 When you connect to @code{gdbserver} using @code{target remote},
16846 @code{gdbserver} debugs the specified program only once. When the
16847 program exits, or you detach from it, @value{GDBN} closes the connection
16848 and @code{gdbserver} exits.
16850 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16851 enters multi-process mode. When the debugged program exits, or you
16852 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16853 though no program is running. The @code{run} and @code{attach}
16854 commands instruct @code{gdbserver} to run or attach to a new program.
16855 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16856 remote exec-file}) to select the program to run. Command line
16857 arguments are supported, except for wildcard expansion and I/O
16858 redirection (@pxref{Arguments}).
16860 @cindex @option{--multi}, @code{gdbserver} option
16861 To start @code{gdbserver} without supplying an initial command to run
16862 or process ID to attach, use the @option{--multi} command line option.
16863 Then you can connect using @kbd{target extended-remote} and start
16864 the program you want to debug.
16866 In multi-process mode @code{gdbserver} does not automatically exit unless you
16867 use the option @option{--once}. You can terminate it by using
16868 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16869 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16870 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16871 @option{--multi} option to @code{gdbserver} has no influence on that.
16873 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16875 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16877 @code{gdbserver} normally terminates after all of its debugged processes have
16878 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16879 extended-remote}, @code{gdbserver} stays running even with no processes left.
16880 @value{GDBN} normally terminates the spawned debugged process on its exit,
16881 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16882 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16883 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16884 stays running even in the @kbd{target remote} mode.
16886 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16887 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16888 completeness, at most one @value{GDBN} can be connected at a time.
16890 @cindex @option{--once}, @code{gdbserver} option
16891 By default, @code{gdbserver} keeps the listening TCP port open, so that
16892 additional connections are possible. However, if you start @code{gdbserver}
16893 with the @option{--once} option, it will stop listening for any further
16894 connection attempts after connecting to the first @value{GDBN} session. This
16895 means no further connections to @code{gdbserver} will be possible after the
16896 first one. It also means @code{gdbserver} will terminate after the first
16897 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16898 connections and even in the @kbd{target extended-remote} mode. The
16899 @option{--once} option allows reusing the same port number for connecting to
16900 multiple instances of @code{gdbserver} running on the same host, since each
16901 instance closes its port after the first connection.
16903 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16905 @cindex @option{--debug}, @code{gdbserver} option
16906 The @option{--debug} option tells @code{gdbserver} to display extra
16907 status information about the debugging process.
16908 @cindex @option{--remote-debug}, @code{gdbserver} option
16909 The @option{--remote-debug} option tells @code{gdbserver} to display
16910 remote protocol debug output. These options are intended for
16911 @code{gdbserver} development and for bug reports to the developers.
16913 @cindex @option{--wrapper}, @code{gdbserver} option
16914 The @option{--wrapper} option specifies a wrapper to launch programs
16915 for debugging. The option should be followed by the name of the
16916 wrapper, then any command-line arguments to pass to the wrapper, then
16917 @kbd{--} indicating the end of the wrapper arguments.
16919 @code{gdbserver} runs the specified wrapper program with a combined
16920 command line including the wrapper arguments, then the name of the
16921 program to debug, then any arguments to the program. The wrapper
16922 runs until it executes your program, and then @value{GDBN} gains control.
16924 You can use any program that eventually calls @code{execve} with
16925 its arguments as a wrapper. Several standard Unix utilities do
16926 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16927 with @code{exec "$@@"} will also work.
16929 For example, you can use @code{env} to pass an environment variable to
16930 the debugged program, without setting the variable in @code{gdbserver}'s
16934 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16937 @subsection Connecting to @code{gdbserver}
16939 Run @value{GDBN} on the host system.
16941 First make sure you have the necessary symbol files. Load symbols for
16942 your application using the @code{file} command before you connect. Use
16943 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16944 was compiled with the correct sysroot using @code{--with-sysroot}).
16946 The symbol file and target libraries must exactly match the executable
16947 and libraries on the target, with one exception: the files on the host
16948 system should not be stripped, even if the files on the target system
16949 are. Mismatched or missing files will lead to confusing results
16950 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16951 files may also prevent @code{gdbserver} from debugging multi-threaded
16954 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16955 For TCP connections, you must start up @code{gdbserver} prior to using
16956 the @code{target remote} command. Otherwise you may get an error whose
16957 text depends on the host system, but which usually looks something like
16958 @samp{Connection refused}. Don't use the @code{load}
16959 command in @value{GDBN} when using @code{gdbserver}, since the program is
16960 already on the target.
16962 @subsection Monitor Commands for @code{gdbserver}
16963 @cindex monitor commands, for @code{gdbserver}
16964 @anchor{Monitor Commands for gdbserver}
16966 During a @value{GDBN} session using @code{gdbserver}, you can use the
16967 @code{monitor} command to send special requests to @code{gdbserver}.
16968 Here are the available commands.
16972 List the available monitor commands.
16974 @item monitor set debug 0
16975 @itemx monitor set debug 1
16976 Disable or enable general debugging messages.
16978 @item monitor set remote-debug 0
16979 @itemx monitor set remote-debug 1
16980 Disable or enable specific debugging messages associated with the remote
16981 protocol (@pxref{Remote Protocol}).
16983 @item monitor set libthread-db-search-path [PATH]
16984 @cindex gdbserver, search path for @code{libthread_db}
16985 When this command is issued, @var{path} is a colon-separated list of
16986 directories to search for @code{libthread_db} (@pxref{Threads,,set
16987 libthread-db-search-path}). If you omit @var{path},
16988 @samp{libthread-db-search-path} will be reset to its default value.
16990 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16991 not supported in @code{gdbserver}.
16994 Tell gdbserver to exit immediately. This command should be followed by
16995 @code{disconnect} to close the debugging session. @code{gdbserver} will
16996 detach from any attached processes and kill any processes it created.
16997 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16998 of a multi-process mode debug session.
17002 @subsection Tracepoints support in @code{gdbserver}
17003 @cindex tracepoints support in @code{gdbserver}
17005 On some targets, @code{gdbserver} supports tracepoints, fast
17006 tracepoints and static tracepoints.
17008 For fast or static tracepoints to work, a special library called the
17009 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17010 This library is built and distributed as an integral part of
17011 @code{gdbserver}. In addition, support for static tracepoints
17012 requires building the in-process agent library with static tracepoints
17013 support. At present, the UST (LTTng Userspace Tracer,
17014 @url{http://lttng.org/ust}) tracing engine is supported. This support
17015 is automatically available if UST development headers are found in the
17016 standard include path when @code{gdbserver} is built, or if
17017 @code{gdbserver} was explicitly configured using @option{--with-ust}
17018 to point at such headers. You can explicitly disable the support
17019 using @option{--with-ust=no}.
17021 There are several ways to load the in-process agent in your program:
17024 @item Specifying it as dependency at link time
17026 You can link your program dynamically with the in-process agent
17027 library. On most systems, this is accomplished by adding
17028 @code{-linproctrace} to the link command.
17030 @item Using the system's preloading mechanisms
17032 You can force loading the in-process agent at startup time by using
17033 your system's support for preloading shared libraries. Many Unixes
17034 support the concept of preloading user defined libraries. In most
17035 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17036 in the environment. See also the description of @code{gdbserver}'s
17037 @option{--wrapper} command line option.
17039 @item Using @value{GDBN} to force loading the agent at run time
17041 On some systems, you can force the inferior to load a shared library,
17042 by calling a dynamic loader function in the inferior that takes care
17043 of dynamically looking up and loading a shared library. On most Unix
17044 systems, the function is @code{dlopen}. You'll use the @code{call}
17045 command for that. For example:
17048 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17051 Note that on most Unix systems, for the @code{dlopen} function to be
17052 available, the program needs to be linked with @code{-ldl}.
17055 On systems that have a userspace dynamic loader, like most Unix
17056 systems, when you connect to @code{gdbserver} using @code{target
17057 remote}, you'll find that the program is stopped at the dynamic
17058 loader's entry point, and no shared library has been loaded in the
17059 program's address space yet, including the in-process agent. In that
17060 case, before being able to use any of the fast or static tracepoints
17061 features, you need to let the loader run and load the shared
17062 libraries. The simplest way to do that is to run the program to the
17063 main procedure. E.g., if debugging a C or C@t{++} program, start
17064 @code{gdbserver} like so:
17067 $ gdbserver :9999 myprogram
17070 Start GDB and connect to @code{gdbserver} like so, and run to main:
17074 (@value{GDBP}) target remote myhost:9999
17075 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17076 (@value{GDBP}) b main
17077 (@value{GDBP}) continue
17080 The in-process tracing agent library should now be loaded into the
17081 process; you can confirm it with the @code{info sharedlibrary}
17082 command, which will list @file{libinproctrace.so} as loaded in the
17083 process. You are now ready to install fast tracepoints, list static
17084 tracepoint markers, probe static tracepoints markers, and start
17087 @node Remote Configuration
17088 @section Remote Configuration
17091 @kindex show remote
17092 This section documents the configuration options available when
17093 debugging remote programs. For the options related to the File I/O
17094 extensions of the remote protocol, see @ref{system,
17095 system-call-allowed}.
17098 @item set remoteaddresssize @var{bits}
17099 @cindex address size for remote targets
17100 @cindex bits in remote address
17101 Set the maximum size of address in a memory packet to the specified
17102 number of bits. @value{GDBN} will mask off the address bits above
17103 that number, when it passes addresses to the remote target. The
17104 default value is the number of bits in the target's address.
17106 @item show remoteaddresssize
17107 Show the current value of remote address size in bits.
17109 @item set remotebaud @var{n}
17110 @cindex baud rate for remote targets
17111 Set the baud rate for the remote serial I/O to @var{n} baud. The
17112 value is used to set the speed of the serial port used for debugging
17115 @item show remotebaud
17116 Show the current speed of the remote connection.
17118 @item set remotebreak
17119 @cindex interrupt remote programs
17120 @cindex BREAK signal instead of Ctrl-C
17121 @anchor{set remotebreak}
17122 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17123 when you type @kbd{Ctrl-c} to interrupt the program running
17124 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17125 character instead. The default is off, since most remote systems
17126 expect to see @samp{Ctrl-C} as the interrupt signal.
17128 @item show remotebreak
17129 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17130 interrupt the remote program.
17132 @item set remoteflow on
17133 @itemx set remoteflow off
17134 @kindex set remoteflow
17135 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17136 on the serial port used to communicate to the remote target.
17138 @item show remoteflow
17139 @kindex show remoteflow
17140 Show the current setting of hardware flow control.
17142 @item set remotelogbase @var{base}
17143 Set the base (a.k.a.@: radix) of logging serial protocol
17144 communications to @var{base}. Supported values of @var{base} are:
17145 @code{ascii}, @code{octal}, and @code{hex}. The default is
17148 @item show remotelogbase
17149 Show the current setting of the radix for logging remote serial
17152 @item set remotelogfile @var{file}
17153 @cindex record serial communications on file
17154 Record remote serial communications on the named @var{file}. The
17155 default is not to record at all.
17157 @item show remotelogfile.
17158 Show the current setting of the file name on which to record the
17159 serial communications.
17161 @item set remotetimeout @var{num}
17162 @cindex timeout for serial communications
17163 @cindex remote timeout
17164 Set the timeout limit to wait for the remote target to respond to
17165 @var{num} seconds. The default is 2 seconds.
17167 @item show remotetimeout
17168 Show the current number of seconds to wait for the remote target
17171 @cindex limit hardware breakpoints and watchpoints
17172 @cindex remote target, limit break- and watchpoints
17173 @anchor{set remote hardware-watchpoint-limit}
17174 @anchor{set remote hardware-breakpoint-limit}
17175 @item set remote hardware-watchpoint-limit @var{limit}
17176 @itemx set remote hardware-breakpoint-limit @var{limit}
17177 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17178 watchpoints. A limit of -1, the default, is treated as unlimited.
17180 @cindex limit hardware watchpoints length
17181 @cindex remote target, limit watchpoints length
17182 @anchor{set remote hardware-watchpoint-length-limit}
17183 @item set remote hardware-watchpoint-length-limit @var{limit}
17184 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17185 a remote hardware watchpoint. A limit of -1, the default, is treated
17188 @item show remote hardware-watchpoint-length-limit
17189 Show the current limit (in bytes) of the maximum length of
17190 a remote hardware watchpoint.
17192 @item set remote exec-file @var{filename}
17193 @itemx show remote exec-file
17194 @anchor{set remote exec-file}
17195 @cindex executable file, for remote target
17196 Select the file used for @code{run} with @code{target
17197 extended-remote}. This should be set to a filename valid on the
17198 target system. If it is not set, the target will use a default
17199 filename (e.g.@: the last program run).
17201 @item set remote interrupt-sequence
17202 @cindex interrupt remote programs
17203 @cindex select Ctrl-C, BREAK or BREAK-g
17204 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17205 @samp{BREAK-g} as the
17206 sequence to the remote target in order to interrupt the execution.
17207 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17208 is high level of serial line for some certain time.
17209 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17210 It is @code{BREAK} signal followed by character @code{g}.
17212 @item show interrupt-sequence
17213 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17214 is sent by @value{GDBN} to interrupt the remote program.
17215 @code{BREAK-g} is BREAK signal followed by @code{g} and
17216 also known as Magic SysRq g.
17218 @item set remote interrupt-on-connect
17219 @cindex send interrupt-sequence on start
17220 Specify whether interrupt-sequence is sent to remote target when
17221 @value{GDBN} connects to it. This is mostly needed when you debug
17222 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17223 which is known as Magic SysRq g in order to connect @value{GDBN}.
17225 @item show interrupt-on-connect
17226 Show whether interrupt-sequence is sent
17227 to remote target when @value{GDBN} connects to it.
17231 @item set tcp auto-retry on
17232 @cindex auto-retry, for remote TCP target
17233 Enable auto-retry for remote TCP connections. This is useful if the remote
17234 debugging agent is launched in parallel with @value{GDBN}; there is a race
17235 condition because the agent may not become ready to accept the connection
17236 before @value{GDBN} attempts to connect. When auto-retry is
17237 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17238 to establish the connection using the timeout specified by
17239 @code{set tcp connect-timeout}.
17241 @item set tcp auto-retry off
17242 Do not auto-retry failed TCP connections.
17244 @item show tcp auto-retry
17245 Show the current auto-retry setting.
17247 @item set tcp connect-timeout @var{seconds}
17248 @cindex connection timeout, for remote TCP target
17249 @cindex timeout, for remote target connection
17250 Set the timeout for establishing a TCP connection to the remote target to
17251 @var{seconds}. The timeout affects both polling to retry failed connections
17252 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17253 that are merely slow to complete, and represents an approximate cumulative
17256 @item show tcp connect-timeout
17257 Show the current connection timeout setting.
17260 @cindex remote packets, enabling and disabling
17261 The @value{GDBN} remote protocol autodetects the packets supported by
17262 your debugging stub. If you need to override the autodetection, you
17263 can use these commands to enable or disable individual packets. Each
17264 packet can be set to @samp{on} (the remote target supports this
17265 packet), @samp{off} (the remote target does not support this packet),
17266 or @samp{auto} (detect remote target support for this packet). They
17267 all default to @samp{auto}. For more information about each packet,
17268 see @ref{Remote Protocol}.
17270 During normal use, you should not have to use any of these commands.
17271 If you do, that may be a bug in your remote debugging stub, or a bug
17272 in @value{GDBN}. You may want to report the problem to the
17273 @value{GDBN} developers.
17275 For each packet @var{name}, the command to enable or disable the
17276 packet is @code{set remote @var{name}-packet}. The available settings
17279 @multitable @columnfractions 0.28 0.32 0.25
17282 @tab Related Features
17284 @item @code{fetch-register}
17286 @tab @code{info registers}
17288 @item @code{set-register}
17292 @item @code{binary-download}
17294 @tab @code{load}, @code{set}
17296 @item @code{read-aux-vector}
17297 @tab @code{qXfer:auxv:read}
17298 @tab @code{info auxv}
17300 @item @code{symbol-lookup}
17301 @tab @code{qSymbol}
17302 @tab Detecting multiple threads
17304 @item @code{attach}
17305 @tab @code{vAttach}
17308 @item @code{verbose-resume}
17310 @tab Stepping or resuming multiple threads
17316 @item @code{software-breakpoint}
17320 @item @code{hardware-breakpoint}
17324 @item @code{write-watchpoint}
17328 @item @code{read-watchpoint}
17332 @item @code{access-watchpoint}
17336 @item @code{target-features}
17337 @tab @code{qXfer:features:read}
17338 @tab @code{set architecture}
17340 @item @code{library-info}
17341 @tab @code{qXfer:libraries:read}
17342 @tab @code{info sharedlibrary}
17344 @item @code{memory-map}
17345 @tab @code{qXfer:memory-map:read}
17346 @tab @code{info mem}
17348 @item @code{read-sdata-object}
17349 @tab @code{qXfer:sdata:read}
17350 @tab @code{print $_sdata}
17352 @item @code{read-spu-object}
17353 @tab @code{qXfer:spu:read}
17354 @tab @code{info spu}
17356 @item @code{write-spu-object}
17357 @tab @code{qXfer:spu:write}
17358 @tab @code{info spu}
17360 @item @code{read-siginfo-object}
17361 @tab @code{qXfer:siginfo:read}
17362 @tab @code{print $_siginfo}
17364 @item @code{write-siginfo-object}
17365 @tab @code{qXfer:siginfo:write}
17366 @tab @code{set $_siginfo}
17368 @item @code{threads}
17369 @tab @code{qXfer:threads:read}
17370 @tab @code{info threads}
17372 @item @code{get-thread-local-@*storage-address}
17373 @tab @code{qGetTLSAddr}
17374 @tab Displaying @code{__thread} variables
17376 @item @code{get-thread-information-block-address}
17377 @tab @code{qGetTIBAddr}
17378 @tab Display MS-Windows Thread Information Block.
17380 @item @code{search-memory}
17381 @tab @code{qSearch:memory}
17384 @item @code{supported-packets}
17385 @tab @code{qSupported}
17386 @tab Remote communications parameters
17388 @item @code{pass-signals}
17389 @tab @code{QPassSignals}
17390 @tab @code{handle @var{signal}}
17392 @item @code{hostio-close-packet}
17393 @tab @code{vFile:close}
17394 @tab @code{remote get}, @code{remote put}
17396 @item @code{hostio-open-packet}
17397 @tab @code{vFile:open}
17398 @tab @code{remote get}, @code{remote put}
17400 @item @code{hostio-pread-packet}
17401 @tab @code{vFile:pread}
17402 @tab @code{remote get}, @code{remote put}
17404 @item @code{hostio-pwrite-packet}
17405 @tab @code{vFile:pwrite}
17406 @tab @code{remote get}, @code{remote put}
17408 @item @code{hostio-unlink-packet}
17409 @tab @code{vFile:unlink}
17410 @tab @code{remote delete}
17412 @item @code{noack-packet}
17413 @tab @code{QStartNoAckMode}
17414 @tab Packet acknowledgment
17416 @item @code{osdata}
17417 @tab @code{qXfer:osdata:read}
17418 @tab @code{info os}
17420 @item @code{query-attached}
17421 @tab @code{qAttached}
17422 @tab Querying remote process attach state.
17424 @item @code{traceframe-info}
17425 @tab @code{qXfer:traceframe-info:read}
17426 @tab Traceframe info
17428 @item @code{install-in-trace}
17429 @tab @code{InstallInTrace}
17430 @tab Install tracepoint in tracing
17432 @item @code{disable-randomization}
17433 @tab @code{QDisableRandomization}
17434 @tab @code{set disable-randomization}
17438 @section Implementing a Remote Stub
17440 @cindex debugging stub, example
17441 @cindex remote stub, example
17442 @cindex stub example, remote debugging
17443 The stub files provided with @value{GDBN} implement the target side of the
17444 communication protocol, and the @value{GDBN} side is implemented in the
17445 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17446 these subroutines to communicate, and ignore the details. (If you're
17447 implementing your own stub file, you can still ignore the details: start
17448 with one of the existing stub files. @file{sparc-stub.c} is the best
17449 organized, and therefore the easiest to read.)
17451 @cindex remote serial debugging, overview
17452 To debug a program running on another machine (the debugging
17453 @dfn{target} machine), you must first arrange for all the usual
17454 prerequisites for the program to run by itself. For example, for a C
17459 A startup routine to set up the C runtime environment; these usually
17460 have a name like @file{crt0}. The startup routine may be supplied by
17461 your hardware supplier, or you may have to write your own.
17464 A C subroutine library to support your program's
17465 subroutine calls, notably managing input and output.
17468 A way of getting your program to the other machine---for example, a
17469 download program. These are often supplied by the hardware
17470 manufacturer, but you may have to write your own from hardware
17474 The next step is to arrange for your program to use a serial port to
17475 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17476 machine). In general terms, the scheme looks like this:
17480 @value{GDBN} already understands how to use this protocol; when everything
17481 else is set up, you can simply use the @samp{target remote} command
17482 (@pxref{Targets,,Specifying a Debugging Target}).
17484 @item On the target,
17485 you must link with your program a few special-purpose subroutines that
17486 implement the @value{GDBN} remote serial protocol. The file containing these
17487 subroutines is called a @dfn{debugging stub}.
17489 On certain remote targets, you can use an auxiliary program
17490 @code{gdbserver} instead of linking a stub into your program.
17491 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17494 The debugging stub is specific to the architecture of the remote
17495 machine; for example, use @file{sparc-stub.c} to debug programs on
17498 @cindex remote serial stub list
17499 These working remote stubs are distributed with @value{GDBN}:
17504 @cindex @file{i386-stub.c}
17507 For Intel 386 and compatible architectures.
17510 @cindex @file{m68k-stub.c}
17511 @cindex Motorola 680x0
17513 For Motorola 680x0 architectures.
17516 @cindex @file{sh-stub.c}
17519 For Renesas SH architectures.
17522 @cindex @file{sparc-stub.c}
17524 For @sc{sparc} architectures.
17526 @item sparcl-stub.c
17527 @cindex @file{sparcl-stub.c}
17530 For Fujitsu @sc{sparclite} architectures.
17534 The @file{README} file in the @value{GDBN} distribution may list other
17535 recently added stubs.
17538 * Stub Contents:: What the stub can do for you
17539 * Bootstrapping:: What you must do for the stub
17540 * Debug Session:: Putting it all together
17543 @node Stub Contents
17544 @subsection What the Stub Can Do for You
17546 @cindex remote serial stub
17547 The debugging stub for your architecture supplies these three
17551 @item set_debug_traps
17552 @findex set_debug_traps
17553 @cindex remote serial stub, initialization
17554 This routine arranges for @code{handle_exception} to run when your
17555 program stops. You must call this subroutine explicitly in your
17556 program's startup code.
17558 @item handle_exception
17559 @findex handle_exception
17560 @cindex remote serial stub, main routine
17561 This is the central workhorse, but your program never calls it
17562 explicitly---the setup code arranges for @code{handle_exception} to
17563 run when a trap is triggered.
17565 @code{handle_exception} takes control when your program stops during
17566 execution (for example, on a breakpoint), and mediates communications
17567 with @value{GDBN} on the host machine. This is where the communications
17568 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17569 representative on the target machine. It begins by sending summary
17570 information on the state of your program, then continues to execute,
17571 retrieving and transmitting any information @value{GDBN} needs, until you
17572 execute a @value{GDBN} command that makes your program resume; at that point,
17573 @code{handle_exception} returns control to your own code on the target
17577 @cindex @code{breakpoint} subroutine, remote
17578 Use this auxiliary subroutine to make your program contain a
17579 breakpoint. Depending on the particular situation, this may be the only
17580 way for @value{GDBN} to get control. For instance, if your target
17581 machine has some sort of interrupt button, you won't need to call this;
17582 pressing the interrupt button transfers control to
17583 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17584 simply receiving characters on the serial port may also trigger a trap;
17585 again, in that situation, you don't need to call @code{breakpoint} from
17586 your own program---simply running @samp{target remote} from the host
17587 @value{GDBN} session gets control.
17589 Call @code{breakpoint} if none of these is true, or if you simply want
17590 to make certain your program stops at a predetermined point for the
17591 start of your debugging session.
17594 @node Bootstrapping
17595 @subsection What You Must Do for the Stub
17597 @cindex remote stub, support routines
17598 The debugging stubs that come with @value{GDBN} are set up for a particular
17599 chip architecture, but they have no information about the rest of your
17600 debugging target machine.
17602 First of all you need to tell the stub how to communicate with the
17606 @item int getDebugChar()
17607 @findex getDebugChar
17608 Write this subroutine to read a single character from the serial port.
17609 It may be identical to @code{getchar} for your target system; a
17610 different name is used to allow you to distinguish the two if you wish.
17612 @item void putDebugChar(int)
17613 @findex putDebugChar
17614 Write this subroutine to write a single character to the serial port.
17615 It may be identical to @code{putchar} for your target system; a
17616 different name is used to allow you to distinguish the two if you wish.
17619 @cindex control C, and remote debugging
17620 @cindex interrupting remote targets
17621 If you want @value{GDBN} to be able to stop your program while it is
17622 running, you need to use an interrupt-driven serial driver, and arrange
17623 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17624 character). That is the character which @value{GDBN} uses to tell the
17625 remote system to stop.
17627 Getting the debugging target to return the proper status to @value{GDBN}
17628 probably requires changes to the standard stub; one quick and dirty way
17629 is to just execute a breakpoint instruction (the ``dirty'' part is that
17630 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17632 Other routines you need to supply are:
17635 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17636 @findex exceptionHandler
17637 Write this function to install @var{exception_address} in the exception
17638 handling tables. You need to do this because the stub does not have any
17639 way of knowing what the exception handling tables on your target system
17640 are like (for example, the processor's table might be in @sc{rom},
17641 containing entries which point to a table in @sc{ram}).
17642 @var{exception_number} is the exception number which should be changed;
17643 its meaning is architecture-dependent (for example, different numbers
17644 might represent divide by zero, misaligned access, etc). When this
17645 exception occurs, control should be transferred directly to
17646 @var{exception_address}, and the processor state (stack, registers,
17647 and so on) should be just as it is when a processor exception occurs. So if
17648 you want to use a jump instruction to reach @var{exception_address}, it
17649 should be a simple jump, not a jump to subroutine.
17651 For the 386, @var{exception_address} should be installed as an interrupt
17652 gate so that interrupts are masked while the handler runs. The gate
17653 should be at privilege level 0 (the most privileged level). The
17654 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17655 help from @code{exceptionHandler}.
17657 @item void flush_i_cache()
17658 @findex flush_i_cache
17659 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17660 instruction cache, if any, on your target machine. If there is no
17661 instruction cache, this subroutine may be a no-op.
17663 On target machines that have instruction caches, @value{GDBN} requires this
17664 function to make certain that the state of your program is stable.
17668 You must also make sure this library routine is available:
17671 @item void *memset(void *, int, int)
17673 This is the standard library function @code{memset} that sets an area of
17674 memory to a known value. If you have one of the free versions of
17675 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17676 either obtain it from your hardware manufacturer, or write your own.
17679 If you do not use the GNU C compiler, you may need other standard
17680 library subroutines as well; this varies from one stub to another,
17681 but in general the stubs are likely to use any of the common library
17682 subroutines which @code{@value{NGCC}} generates as inline code.
17685 @node Debug Session
17686 @subsection Putting it All Together
17688 @cindex remote serial debugging summary
17689 In summary, when your program is ready to debug, you must follow these
17694 Make sure you have defined the supporting low-level routines
17695 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17697 @code{getDebugChar}, @code{putDebugChar},
17698 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17702 Insert these lines in your program's startup code, before the main
17703 procedure is called:
17710 On some machines, when a breakpoint trap is raised, the hardware
17711 automatically makes the PC point to the instruction after the
17712 breakpoint. If your machine doesn't do that, you may need to adjust
17713 @code{handle_exception} to arrange for it to return to the instruction
17714 after the breakpoint on this first invocation, so that your program
17715 doesn't keep hitting the initial breakpoint instead of making
17719 For the 680x0 stub only, you need to provide a variable called
17720 @code{exceptionHook}. Normally you just use:
17723 void (*exceptionHook)() = 0;
17727 but if before calling @code{set_debug_traps}, you set it to point to a
17728 function in your program, that function is called when
17729 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17730 error). The function indicated by @code{exceptionHook} is called with
17731 one parameter: an @code{int} which is the exception number.
17734 Compile and link together: your program, the @value{GDBN} debugging stub for
17735 your target architecture, and the supporting subroutines.
17738 Make sure you have a serial connection between your target machine and
17739 the @value{GDBN} host, and identify the serial port on the host.
17742 @c The "remote" target now provides a `load' command, so we should
17743 @c document that. FIXME.
17744 Download your program to your target machine (or get it there by
17745 whatever means the manufacturer provides), and start it.
17748 Start @value{GDBN} on the host, and connect to the target
17749 (@pxref{Connecting,,Connecting to a Remote Target}).
17753 @node Configurations
17754 @chapter Configuration-Specific Information
17756 While nearly all @value{GDBN} commands are available for all native and
17757 cross versions of the debugger, there are some exceptions. This chapter
17758 describes things that are only available in certain configurations.
17760 There are three major categories of configurations: native
17761 configurations, where the host and target are the same, embedded
17762 operating system configurations, which are usually the same for several
17763 different processor architectures, and bare embedded processors, which
17764 are quite different from each other.
17769 * Embedded Processors::
17776 This section describes details specific to particular native
17781 * BSD libkvm Interface:: Debugging BSD kernel memory images
17782 * SVR4 Process Information:: SVR4 process information
17783 * DJGPP Native:: Features specific to the DJGPP port
17784 * Cygwin Native:: Features specific to the Cygwin port
17785 * Hurd Native:: Features specific to @sc{gnu} Hurd
17786 * Neutrino:: Features specific to QNX Neutrino
17787 * Darwin:: Features specific to Darwin
17793 On HP-UX systems, if you refer to a function or variable name that
17794 begins with a dollar sign, @value{GDBN} searches for a user or system
17795 name first, before it searches for a convenience variable.
17798 @node BSD libkvm Interface
17799 @subsection BSD libkvm Interface
17802 @cindex kernel memory image
17803 @cindex kernel crash dump
17805 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17806 interface that provides a uniform interface for accessing kernel virtual
17807 memory images, including live systems and crash dumps. @value{GDBN}
17808 uses this interface to allow you to debug live kernels and kernel crash
17809 dumps on many native BSD configurations. This is implemented as a
17810 special @code{kvm} debugging target. For debugging a live system, load
17811 the currently running kernel into @value{GDBN} and connect to the
17815 (@value{GDBP}) @b{target kvm}
17818 For debugging crash dumps, provide the file name of the crash dump as an
17822 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17825 Once connected to the @code{kvm} target, the following commands are
17831 Set current context from the @dfn{Process Control Block} (PCB) address.
17834 Set current context from proc address. This command isn't available on
17835 modern FreeBSD systems.
17838 @node SVR4 Process Information
17839 @subsection SVR4 Process Information
17841 @cindex examine process image
17842 @cindex process info via @file{/proc}
17844 Many versions of SVR4 and compatible systems provide a facility called
17845 @samp{/proc} that can be used to examine the image of a running
17846 process using file-system subroutines. If @value{GDBN} is configured
17847 for an operating system with this facility, the command @code{info
17848 proc} is available to report information about the process running
17849 your program, or about any process running on your system. @code{info
17850 proc} works only on SVR4 systems that include the @code{procfs} code.
17851 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17852 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17858 @itemx info proc @var{process-id}
17859 Summarize available information about any running process. If a
17860 process ID is specified by @var{process-id}, display information about
17861 that process; otherwise display information about the program being
17862 debugged. The summary includes the debugged process ID, the command
17863 line used to invoke it, its current working directory, and its
17864 executable file's absolute file name.
17866 On some systems, @var{process-id} can be of the form
17867 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17868 within a process. If the optional @var{pid} part is missing, it means
17869 a thread from the process being debugged (the leading @samp{/} still
17870 needs to be present, or else @value{GDBN} will interpret the number as
17871 a process ID rather than a thread ID).
17873 @item info proc mappings
17874 @cindex memory address space mappings
17875 Report the memory address space ranges accessible in the program, with
17876 information on whether the process has read, write, or execute access
17877 rights to each range. On @sc{gnu}/Linux systems, each memory range
17878 includes the object file which is mapped to that range, instead of the
17879 memory access rights to that range.
17881 @item info proc stat
17882 @itemx info proc status
17883 @cindex process detailed status information
17884 These subcommands are specific to @sc{gnu}/Linux systems. They show
17885 the process-related information, including the user ID and group ID;
17886 how many threads are there in the process; its virtual memory usage;
17887 the signals that are pending, blocked, and ignored; its TTY; its
17888 consumption of system and user time; its stack size; its @samp{nice}
17889 value; etc. For more information, see the @samp{proc} man page
17890 (type @kbd{man 5 proc} from your shell prompt).
17892 @item info proc all
17893 Show all the information about the process described under all of the
17894 above @code{info proc} subcommands.
17897 @comment These sub-options of 'info proc' were not included when
17898 @comment procfs.c was re-written. Keep their descriptions around
17899 @comment against the day when someone finds the time to put them back in.
17900 @kindex info proc times
17901 @item info proc times
17902 Starting time, user CPU time, and system CPU time for your program and
17905 @kindex info proc id
17907 Report on the process IDs related to your program: its own process ID,
17908 the ID of its parent, the process group ID, and the session ID.
17911 @item set procfs-trace
17912 @kindex set procfs-trace
17913 @cindex @code{procfs} API calls
17914 This command enables and disables tracing of @code{procfs} API calls.
17916 @item show procfs-trace
17917 @kindex show procfs-trace
17918 Show the current state of @code{procfs} API call tracing.
17920 @item set procfs-file @var{file}
17921 @kindex set procfs-file
17922 Tell @value{GDBN} to write @code{procfs} API trace to the named
17923 @var{file}. @value{GDBN} appends the trace info to the previous
17924 contents of the file. The default is to display the trace on the
17927 @item show procfs-file
17928 @kindex show procfs-file
17929 Show the file to which @code{procfs} API trace is written.
17931 @item proc-trace-entry
17932 @itemx proc-trace-exit
17933 @itemx proc-untrace-entry
17934 @itemx proc-untrace-exit
17935 @kindex proc-trace-entry
17936 @kindex proc-trace-exit
17937 @kindex proc-untrace-entry
17938 @kindex proc-untrace-exit
17939 These commands enable and disable tracing of entries into and exits
17940 from the @code{syscall} interface.
17943 @kindex info pidlist
17944 @cindex process list, QNX Neutrino
17945 For QNX Neutrino only, this command displays the list of all the
17946 processes and all the threads within each process.
17949 @kindex info meminfo
17950 @cindex mapinfo list, QNX Neutrino
17951 For QNX Neutrino only, this command displays the list of all mapinfos.
17955 @subsection Features for Debugging @sc{djgpp} Programs
17956 @cindex @sc{djgpp} debugging
17957 @cindex native @sc{djgpp} debugging
17958 @cindex MS-DOS-specific commands
17961 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17962 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17963 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17964 top of real-mode DOS systems and their emulations.
17966 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17967 defines a few commands specific to the @sc{djgpp} port. This
17968 subsection describes those commands.
17973 This is a prefix of @sc{djgpp}-specific commands which print
17974 information about the target system and important OS structures.
17977 @cindex MS-DOS system info
17978 @cindex free memory information (MS-DOS)
17979 @item info dos sysinfo
17980 This command displays assorted information about the underlying
17981 platform: the CPU type and features, the OS version and flavor, the
17982 DPMI version, and the available conventional and DPMI memory.
17987 @cindex segment descriptor tables
17988 @cindex descriptor tables display
17990 @itemx info dos ldt
17991 @itemx info dos idt
17992 These 3 commands display entries from, respectively, Global, Local,
17993 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17994 tables are data structures which store a descriptor for each segment
17995 that is currently in use. The segment's selector is an index into a
17996 descriptor table; the table entry for that index holds the
17997 descriptor's base address and limit, and its attributes and access
18000 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18001 segment (used for both data and the stack), and a DOS segment (which
18002 allows access to DOS/BIOS data structures and absolute addresses in
18003 conventional memory). However, the DPMI host will usually define
18004 additional segments in order to support the DPMI environment.
18006 @cindex garbled pointers
18007 These commands allow to display entries from the descriptor tables.
18008 Without an argument, all entries from the specified table are
18009 displayed. An argument, which should be an integer expression, means
18010 display a single entry whose index is given by the argument. For
18011 example, here's a convenient way to display information about the
18012 debugged program's data segment:
18015 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18016 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18020 This comes in handy when you want to see whether a pointer is outside
18021 the data segment's limit (i.e.@: @dfn{garbled}).
18023 @cindex page tables display (MS-DOS)
18025 @itemx info dos pte
18026 These two commands display entries from, respectively, the Page
18027 Directory and the Page Tables. Page Directories and Page Tables are
18028 data structures which control how virtual memory addresses are mapped
18029 into physical addresses. A Page Table includes an entry for every
18030 page of memory that is mapped into the program's address space; there
18031 may be several Page Tables, each one holding up to 4096 entries. A
18032 Page Directory has up to 4096 entries, one each for every Page Table
18033 that is currently in use.
18035 Without an argument, @kbd{info dos pde} displays the entire Page
18036 Directory, and @kbd{info dos pte} displays all the entries in all of
18037 the Page Tables. An argument, an integer expression, given to the
18038 @kbd{info dos pde} command means display only that entry from the Page
18039 Directory table. An argument given to the @kbd{info dos pte} command
18040 means display entries from a single Page Table, the one pointed to by
18041 the specified entry in the Page Directory.
18043 @cindex direct memory access (DMA) on MS-DOS
18044 These commands are useful when your program uses @dfn{DMA} (Direct
18045 Memory Access), which needs physical addresses to program the DMA
18048 These commands are supported only with some DPMI servers.
18050 @cindex physical address from linear address
18051 @item info dos address-pte @var{addr}
18052 This command displays the Page Table entry for a specified linear
18053 address. The argument @var{addr} is a linear address which should
18054 already have the appropriate segment's base address added to it,
18055 because this command accepts addresses which may belong to @emph{any}
18056 segment. For example, here's how to display the Page Table entry for
18057 the page where a variable @code{i} is stored:
18060 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18061 @exdent @code{Page Table entry for address 0x11a00d30:}
18062 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18066 This says that @code{i} is stored at offset @code{0xd30} from the page
18067 whose physical base address is @code{0x02698000}, and shows all the
18068 attributes of that page.
18070 Note that you must cast the addresses of variables to a @code{char *},
18071 since otherwise the value of @code{__djgpp_base_address}, the base
18072 address of all variables and functions in a @sc{djgpp} program, will
18073 be added using the rules of C pointer arithmetics: if @code{i} is
18074 declared an @code{int}, @value{GDBN} will add 4 times the value of
18075 @code{__djgpp_base_address} to the address of @code{i}.
18077 Here's another example, it displays the Page Table entry for the
18081 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18082 @exdent @code{Page Table entry for address 0x29110:}
18083 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18087 (The @code{+ 3} offset is because the transfer buffer's address is the
18088 3rd member of the @code{_go32_info_block} structure.) The output
18089 clearly shows that this DPMI server maps the addresses in conventional
18090 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18091 linear (@code{0x29110}) addresses are identical.
18093 This command is supported only with some DPMI servers.
18096 @cindex DOS serial data link, remote debugging
18097 In addition to native debugging, the DJGPP port supports remote
18098 debugging via a serial data link. The following commands are specific
18099 to remote serial debugging in the DJGPP port of @value{GDBN}.
18102 @kindex set com1base
18103 @kindex set com1irq
18104 @kindex set com2base
18105 @kindex set com2irq
18106 @kindex set com3base
18107 @kindex set com3irq
18108 @kindex set com4base
18109 @kindex set com4irq
18110 @item set com1base @var{addr}
18111 This command sets the base I/O port address of the @file{COM1} serial
18114 @item set com1irq @var{irq}
18115 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18116 for the @file{COM1} serial port.
18118 There are similar commands @samp{set com2base}, @samp{set com3irq},
18119 etc.@: for setting the port address and the @code{IRQ} lines for the
18122 @kindex show com1base
18123 @kindex show com1irq
18124 @kindex show com2base
18125 @kindex show com2irq
18126 @kindex show com3base
18127 @kindex show com3irq
18128 @kindex show com4base
18129 @kindex show com4irq
18130 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18131 display the current settings of the base address and the @code{IRQ}
18132 lines used by the COM ports.
18135 @kindex info serial
18136 @cindex DOS serial port status
18137 This command prints the status of the 4 DOS serial ports. For each
18138 port, it prints whether it's active or not, its I/O base address and
18139 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18140 counts of various errors encountered so far.
18144 @node Cygwin Native
18145 @subsection Features for Debugging MS Windows PE Executables
18146 @cindex MS Windows debugging
18147 @cindex native Cygwin debugging
18148 @cindex Cygwin-specific commands
18150 @value{GDBN} supports native debugging of MS Windows programs, including
18151 DLLs with and without symbolic debugging information.
18153 @cindex Ctrl-BREAK, MS-Windows
18154 @cindex interrupt debuggee on MS-Windows
18155 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18156 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18157 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18158 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18159 sequence, which can be used to interrupt the debuggee even if it
18162 There are various additional Cygwin-specific commands, described in
18163 this section. Working with DLLs that have no debugging symbols is
18164 described in @ref{Non-debug DLL Symbols}.
18169 This is a prefix of MS Windows-specific commands which print
18170 information about the target system and important OS structures.
18172 @item info w32 selector
18173 This command displays information returned by
18174 the Win32 API @code{GetThreadSelectorEntry} function.
18175 It takes an optional argument that is evaluated to
18176 a long value to give the information about this given selector.
18177 Without argument, this command displays information
18178 about the six segment registers.
18180 @item info w32 thread-information-block
18181 This command displays thread specific information stored in the
18182 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18183 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18187 This is a Cygwin-specific alias of @code{info shared}.
18189 @kindex dll-symbols
18191 This command loads symbols from a dll similarly to
18192 add-sym command but without the need to specify a base address.
18194 @kindex set cygwin-exceptions
18195 @cindex debugging the Cygwin DLL
18196 @cindex Cygwin DLL, debugging
18197 @item set cygwin-exceptions @var{mode}
18198 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18199 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18200 @value{GDBN} will delay recognition of exceptions, and may ignore some
18201 exceptions which seem to be caused by internal Cygwin DLL
18202 ``bookkeeping''. This option is meant primarily for debugging the
18203 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18204 @value{GDBN} users with false @code{SIGSEGV} signals.
18206 @kindex show cygwin-exceptions
18207 @item show cygwin-exceptions
18208 Displays whether @value{GDBN} will break on exceptions that happen
18209 inside the Cygwin DLL itself.
18211 @kindex set new-console
18212 @item set new-console @var{mode}
18213 If @var{mode} is @code{on} the debuggee will
18214 be started in a new console on next start.
18215 If @var{mode} is @code{off}, the debuggee will
18216 be started in the same console as the debugger.
18218 @kindex show new-console
18219 @item show new-console
18220 Displays whether a new console is used
18221 when the debuggee is started.
18223 @kindex set new-group
18224 @item set new-group @var{mode}
18225 This boolean value controls whether the debuggee should
18226 start a new group or stay in the same group as the debugger.
18227 This affects the way the Windows OS handles
18230 @kindex show new-group
18231 @item show new-group
18232 Displays current value of new-group boolean.
18234 @kindex set debugevents
18235 @item set debugevents
18236 This boolean value adds debug output concerning kernel events related
18237 to the debuggee seen by the debugger. This includes events that
18238 signal thread and process creation and exit, DLL loading and
18239 unloading, console interrupts, and debugging messages produced by the
18240 Windows @code{OutputDebugString} API call.
18242 @kindex set debugexec
18243 @item set debugexec
18244 This boolean value adds debug output concerning execute events
18245 (such as resume thread) seen by the debugger.
18247 @kindex set debugexceptions
18248 @item set debugexceptions
18249 This boolean value adds debug output concerning exceptions in the
18250 debuggee seen by the debugger.
18252 @kindex set debugmemory
18253 @item set debugmemory
18254 This boolean value adds debug output concerning debuggee memory reads
18255 and writes by the debugger.
18259 This boolean values specifies whether the debuggee is called
18260 via a shell or directly (default value is on).
18264 Displays if the debuggee will be started with a shell.
18269 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18272 @node Non-debug DLL Symbols
18273 @subsubsection Support for DLLs without Debugging Symbols
18274 @cindex DLLs with no debugging symbols
18275 @cindex Minimal symbols and DLLs
18277 Very often on windows, some of the DLLs that your program relies on do
18278 not include symbolic debugging information (for example,
18279 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18280 symbols in a DLL, it relies on the minimal amount of symbolic
18281 information contained in the DLL's export table. This section
18282 describes working with such symbols, known internally to @value{GDBN} as
18283 ``minimal symbols''.
18285 Note that before the debugged program has started execution, no DLLs
18286 will have been loaded. The easiest way around this problem is simply to
18287 start the program --- either by setting a breakpoint or letting the
18288 program run once to completion. It is also possible to force
18289 @value{GDBN} to load a particular DLL before starting the executable ---
18290 see the shared library information in @ref{Files}, or the
18291 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18292 explicitly loading symbols from a DLL with no debugging information will
18293 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18294 which may adversely affect symbol lookup performance.
18296 @subsubsection DLL Name Prefixes
18298 In keeping with the naming conventions used by the Microsoft debugging
18299 tools, DLL export symbols are made available with a prefix based on the
18300 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18301 also entered into the symbol table, so @code{CreateFileA} is often
18302 sufficient. In some cases there will be name clashes within a program
18303 (particularly if the executable itself includes full debugging symbols)
18304 necessitating the use of the fully qualified name when referring to the
18305 contents of the DLL. Use single-quotes around the name to avoid the
18306 exclamation mark (``!'') being interpreted as a language operator.
18308 Note that the internal name of the DLL may be all upper-case, even
18309 though the file name of the DLL is lower-case, or vice-versa. Since
18310 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18311 some confusion. If in doubt, try the @code{info functions} and
18312 @code{info variables} commands or even @code{maint print msymbols}
18313 (@pxref{Symbols}). Here's an example:
18316 (@value{GDBP}) info function CreateFileA
18317 All functions matching regular expression "CreateFileA":
18319 Non-debugging symbols:
18320 0x77e885f4 CreateFileA
18321 0x77e885f4 KERNEL32!CreateFileA
18325 (@value{GDBP}) info function !
18326 All functions matching regular expression "!":
18328 Non-debugging symbols:
18329 0x6100114c cygwin1!__assert
18330 0x61004034 cygwin1!_dll_crt0@@0
18331 0x61004240 cygwin1!dll_crt0(per_process *)
18335 @subsubsection Working with Minimal Symbols
18337 Symbols extracted from a DLL's export table do not contain very much
18338 type information. All that @value{GDBN} can do is guess whether a symbol
18339 refers to a function or variable depending on the linker section that
18340 contains the symbol. Also note that the actual contents of the memory
18341 contained in a DLL are not available unless the program is running. This
18342 means that you cannot examine the contents of a variable or disassemble
18343 a function within a DLL without a running program.
18345 Variables are generally treated as pointers and dereferenced
18346 automatically. For this reason, it is often necessary to prefix a
18347 variable name with the address-of operator (``&'') and provide explicit
18348 type information in the command. Here's an example of the type of
18352 (@value{GDBP}) print 'cygwin1!__argv'
18357 (@value{GDBP}) x 'cygwin1!__argv'
18358 0x10021610: "\230y\""
18361 And two possible solutions:
18364 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18365 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18369 (@value{GDBP}) x/2x &'cygwin1!__argv'
18370 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18371 (@value{GDBP}) x/x 0x10021608
18372 0x10021608: 0x0022fd98
18373 (@value{GDBP}) x/s 0x0022fd98
18374 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18377 Setting a break point within a DLL is possible even before the program
18378 starts execution. However, under these circumstances, @value{GDBN} can't
18379 examine the initial instructions of the function in order to skip the
18380 function's frame set-up code. You can work around this by using ``*&''
18381 to set the breakpoint at a raw memory address:
18384 (@value{GDBP}) break *&'python22!PyOS_Readline'
18385 Breakpoint 1 at 0x1e04eff0
18388 The author of these extensions is not entirely convinced that setting a
18389 break point within a shared DLL like @file{kernel32.dll} is completely
18393 @subsection Commands Specific to @sc{gnu} Hurd Systems
18394 @cindex @sc{gnu} Hurd debugging
18396 This subsection describes @value{GDBN} commands specific to the
18397 @sc{gnu} Hurd native debugging.
18402 @kindex set signals@r{, Hurd command}
18403 @kindex set sigs@r{, Hurd command}
18404 This command toggles the state of inferior signal interception by
18405 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18406 affected by this command. @code{sigs} is a shorthand alias for
18411 @kindex show signals@r{, Hurd command}
18412 @kindex show sigs@r{, Hurd command}
18413 Show the current state of intercepting inferior's signals.
18415 @item set signal-thread
18416 @itemx set sigthread
18417 @kindex set signal-thread
18418 @kindex set sigthread
18419 This command tells @value{GDBN} which thread is the @code{libc} signal
18420 thread. That thread is run when a signal is delivered to a running
18421 process. @code{set sigthread} is the shorthand alias of @code{set
18424 @item show signal-thread
18425 @itemx show sigthread
18426 @kindex show signal-thread
18427 @kindex show sigthread
18428 These two commands show which thread will run when the inferior is
18429 delivered a signal.
18432 @kindex set stopped@r{, Hurd command}
18433 This commands tells @value{GDBN} that the inferior process is stopped,
18434 as with the @code{SIGSTOP} signal. The stopped process can be
18435 continued by delivering a signal to it.
18438 @kindex show stopped@r{, Hurd command}
18439 This command shows whether @value{GDBN} thinks the debuggee is
18442 @item set exceptions
18443 @kindex set exceptions@r{, Hurd command}
18444 Use this command to turn off trapping of exceptions in the inferior.
18445 When exception trapping is off, neither breakpoints nor
18446 single-stepping will work. To restore the default, set exception
18449 @item show exceptions
18450 @kindex show exceptions@r{, Hurd command}
18451 Show the current state of trapping exceptions in the inferior.
18453 @item set task pause
18454 @kindex set task@r{, Hurd commands}
18455 @cindex task attributes (@sc{gnu} Hurd)
18456 @cindex pause current task (@sc{gnu} Hurd)
18457 This command toggles task suspension when @value{GDBN} has control.
18458 Setting it to on takes effect immediately, and the task is suspended
18459 whenever @value{GDBN} gets control. Setting it to off will take
18460 effect the next time the inferior is continued. If this option is set
18461 to off, you can use @code{set thread default pause on} or @code{set
18462 thread pause on} (see below) to pause individual threads.
18464 @item show task pause
18465 @kindex show task@r{, Hurd commands}
18466 Show the current state of task suspension.
18468 @item set task detach-suspend-count
18469 @cindex task suspend count
18470 @cindex detach from task, @sc{gnu} Hurd
18471 This command sets the suspend count the task will be left with when
18472 @value{GDBN} detaches from it.
18474 @item show task detach-suspend-count
18475 Show the suspend count the task will be left with when detaching.
18477 @item set task exception-port
18478 @itemx set task excp
18479 @cindex task exception port, @sc{gnu} Hurd
18480 This command sets the task exception port to which @value{GDBN} will
18481 forward exceptions. The argument should be the value of the @dfn{send
18482 rights} of the task. @code{set task excp} is a shorthand alias.
18484 @item set noninvasive
18485 @cindex noninvasive task options
18486 This command switches @value{GDBN} to a mode that is the least
18487 invasive as far as interfering with the inferior is concerned. This
18488 is the same as using @code{set task pause}, @code{set exceptions}, and
18489 @code{set signals} to values opposite to the defaults.
18491 @item info send-rights
18492 @itemx info receive-rights
18493 @itemx info port-rights
18494 @itemx info port-sets
18495 @itemx info dead-names
18498 @cindex send rights, @sc{gnu} Hurd
18499 @cindex receive rights, @sc{gnu} Hurd
18500 @cindex port rights, @sc{gnu} Hurd
18501 @cindex port sets, @sc{gnu} Hurd
18502 @cindex dead names, @sc{gnu} Hurd
18503 These commands display information about, respectively, send rights,
18504 receive rights, port rights, port sets, and dead names of a task.
18505 There are also shorthand aliases: @code{info ports} for @code{info
18506 port-rights} and @code{info psets} for @code{info port-sets}.
18508 @item set thread pause
18509 @kindex set thread@r{, Hurd command}
18510 @cindex thread properties, @sc{gnu} Hurd
18511 @cindex pause current thread (@sc{gnu} Hurd)
18512 This command toggles current thread suspension when @value{GDBN} has
18513 control. Setting it to on takes effect immediately, and the current
18514 thread is suspended whenever @value{GDBN} gets control. Setting it to
18515 off will take effect the next time the inferior is continued.
18516 Normally, this command has no effect, since when @value{GDBN} has
18517 control, the whole task is suspended. However, if you used @code{set
18518 task pause off} (see above), this command comes in handy to suspend
18519 only the current thread.
18521 @item show thread pause
18522 @kindex show thread@r{, Hurd command}
18523 This command shows the state of current thread suspension.
18525 @item set thread run
18526 This command sets whether the current thread is allowed to run.
18528 @item show thread run
18529 Show whether the current thread is allowed to run.
18531 @item set thread detach-suspend-count
18532 @cindex thread suspend count, @sc{gnu} Hurd
18533 @cindex detach from thread, @sc{gnu} Hurd
18534 This command sets the suspend count @value{GDBN} will leave on a
18535 thread when detaching. This number is relative to the suspend count
18536 found by @value{GDBN} when it notices the thread; use @code{set thread
18537 takeover-suspend-count} to force it to an absolute value.
18539 @item show thread detach-suspend-count
18540 Show the suspend count @value{GDBN} will leave on the thread when
18543 @item set thread exception-port
18544 @itemx set thread excp
18545 Set the thread exception port to which to forward exceptions. This
18546 overrides the port set by @code{set task exception-port} (see above).
18547 @code{set thread excp} is the shorthand alias.
18549 @item set thread takeover-suspend-count
18550 Normally, @value{GDBN}'s thread suspend counts are relative to the
18551 value @value{GDBN} finds when it notices each thread. This command
18552 changes the suspend counts to be absolute instead.
18554 @item set thread default
18555 @itemx show thread default
18556 @cindex thread default settings, @sc{gnu} Hurd
18557 Each of the above @code{set thread} commands has a @code{set thread
18558 default} counterpart (e.g., @code{set thread default pause}, @code{set
18559 thread default exception-port}, etc.). The @code{thread default}
18560 variety of commands sets the default thread properties for all
18561 threads; you can then change the properties of individual threads with
18562 the non-default commands.
18567 @subsection QNX Neutrino
18568 @cindex QNX Neutrino
18570 @value{GDBN} provides the following commands specific to the QNX
18574 @item set debug nto-debug
18575 @kindex set debug nto-debug
18576 When set to on, enables debugging messages specific to the QNX
18579 @item show debug nto-debug
18580 @kindex show debug nto-debug
18581 Show the current state of QNX Neutrino messages.
18588 @value{GDBN} provides the following commands specific to the Darwin target:
18591 @item set debug darwin @var{num}
18592 @kindex set debug darwin
18593 When set to a non zero value, enables debugging messages specific to
18594 the Darwin support. Higher values produce more verbose output.
18596 @item show debug darwin
18597 @kindex show debug darwin
18598 Show the current state of Darwin messages.
18600 @item set debug mach-o @var{num}
18601 @kindex set debug mach-o
18602 When set to a non zero value, enables debugging messages while
18603 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18604 file format used on Darwin for object and executable files.) Higher
18605 values produce more verbose output. This is a command to diagnose
18606 problems internal to @value{GDBN} and should not be needed in normal
18609 @item show debug mach-o
18610 @kindex show debug mach-o
18611 Show the current state of Mach-O file messages.
18613 @item set mach-exceptions on
18614 @itemx set mach-exceptions off
18615 @kindex set mach-exceptions
18616 On Darwin, faults are first reported as a Mach exception and are then
18617 mapped to a Posix signal. Use this command to turn on trapping of
18618 Mach exceptions in the inferior. This might be sometimes useful to
18619 better understand the cause of a fault. The default is off.
18621 @item show mach-exceptions
18622 @kindex show mach-exceptions
18623 Show the current state of exceptions trapping.
18628 @section Embedded Operating Systems
18630 This section describes configurations involving the debugging of
18631 embedded operating systems that are available for several different
18635 * VxWorks:: Using @value{GDBN} with VxWorks
18638 @value{GDBN} includes the ability to debug programs running on
18639 various real-time operating systems.
18642 @subsection Using @value{GDBN} with VxWorks
18648 @kindex target vxworks
18649 @item target vxworks @var{machinename}
18650 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18651 is the target system's machine name or IP address.
18655 On VxWorks, @code{load} links @var{filename} dynamically on the
18656 current target system as well as adding its symbols in @value{GDBN}.
18658 @value{GDBN} enables developers to spawn and debug tasks running on networked
18659 VxWorks targets from a Unix host. Already-running tasks spawned from
18660 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18661 both the Unix host and on the VxWorks target. The program
18662 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18663 installed with the name @code{vxgdb}, to distinguish it from a
18664 @value{GDBN} for debugging programs on the host itself.)
18667 @item VxWorks-timeout @var{args}
18668 @kindex vxworks-timeout
18669 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18670 This option is set by the user, and @var{args} represents the number of
18671 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18672 your VxWorks target is a slow software simulator or is on the far side
18673 of a thin network line.
18676 The following information on connecting to VxWorks was current when
18677 this manual was produced; newer releases of VxWorks may use revised
18680 @findex INCLUDE_RDB
18681 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18682 to include the remote debugging interface routines in the VxWorks
18683 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18684 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18685 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18686 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18687 information on configuring and remaking VxWorks, see the manufacturer's
18689 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18691 Once you have included @file{rdb.a} in your VxWorks system image and set
18692 your Unix execution search path to find @value{GDBN}, you are ready to
18693 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18694 @code{vxgdb}, depending on your installation).
18696 @value{GDBN} comes up showing the prompt:
18703 * VxWorks Connection:: Connecting to VxWorks
18704 * VxWorks Download:: VxWorks download
18705 * VxWorks Attach:: Running tasks
18708 @node VxWorks Connection
18709 @subsubsection Connecting to VxWorks
18711 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18712 network. To connect to a target whose host name is ``@code{tt}'', type:
18715 (vxgdb) target vxworks tt
18719 @value{GDBN} displays messages like these:
18722 Attaching remote machine across net...
18727 @value{GDBN} then attempts to read the symbol tables of any object modules
18728 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18729 these files by searching the directories listed in the command search
18730 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18731 to find an object file, it displays a message such as:
18734 prog.o: No such file or directory.
18737 When this happens, add the appropriate directory to the search path with
18738 the @value{GDBN} command @code{path}, and execute the @code{target}
18741 @node VxWorks Download
18742 @subsubsection VxWorks Download
18744 @cindex download to VxWorks
18745 If you have connected to the VxWorks target and you want to debug an
18746 object that has not yet been loaded, you can use the @value{GDBN}
18747 @code{load} command to download a file from Unix to VxWorks
18748 incrementally. The object file given as an argument to the @code{load}
18749 command is actually opened twice: first by the VxWorks target in order
18750 to download the code, then by @value{GDBN} in order to read the symbol
18751 table. This can lead to problems if the current working directories on
18752 the two systems differ. If both systems have NFS mounted the same
18753 filesystems, you can avoid these problems by using absolute paths.
18754 Otherwise, it is simplest to set the working directory on both systems
18755 to the directory in which the object file resides, and then to reference
18756 the file by its name, without any path. For instance, a program
18757 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18758 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18759 program, type this on VxWorks:
18762 -> cd "@var{vxpath}/vw/demo/rdb"
18766 Then, in @value{GDBN}, type:
18769 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18770 (vxgdb) load prog.o
18773 @value{GDBN} displays a response similar to this:
18776 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18779 You can also use the @code{load} command to reload an object module
18780 after editing and recompiling the corresponding source file. Note that
18781 this makes @value{GDBN} delete all currently-defined breakpoints,
18782 auto-displays, and convenience variables, and to clear the value
18783 history. (This is necessary in order to preserve the integrity of
18784 debugger's data structures that reference the target system's symbol
18787 @node VxWorks Attach
18788 @subsubsection Running Tasks
18790 @cindex running VxWorks tasks
18791 You can also attach to an existing task using the @code{attach} command as
18795 (vxgdb) attach @var{task}
18799 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18800 or suspended when you attach to it. Running tasks are suspended at
18801 the time of attachment.
18803 @node Embedded Processors
18804 @section Embedded Processors
18806 This section goes into details specific to particular embedded
18809 @cindex send command to simulator
18810 Whenever a specific embedded processor has a simulator, @value{GDBN}
18811 allows to send an arbitrary command to the simulator.
18814 @item sim @var{command}
18815 @kindex sim@r{, a command}
18816 Send an arbitrary @var{command} string to the simulator. Consult the
18817 documentation for the specific simulator in use for information about
18818 acceptable commands.
18824 * M32R/D:: Renesas M32R/D
18825 * M68K:: Motorola M68K
18826 * MicroBlaze:: Xilinx MicroBlaze
18827 * MIPS Embedded:: MIPS Embedded
18828 * OpenRISC 1000:: OpenRisc 1000
18829 * PA:: HP PA Embedded
18830 * PowerPC Embedded:: PowerPC Embedded
18831 * Sparclet:: Tsqware Sparclet
18832 * Sparclite:: Fujitsu Sparclite
18833 * Z8000:: Zilog Z8000
18836 * Super-H:: Renesas Super-H
18845 @item target rdi @var{dev}
18846 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18847 use this target to communicate with both boards running the Angel
18848 monitor, or with the EmbeddedICE JTAG debug device.
18851 @item target rdp @var{dev}
18856 @value{GDBN} provides the following ARM-specific commands:
18859 @item set arm disassembler
18861 This commands selects from a list of disassembly styles. The
18862 @code{"std"} style is the standard style.
18864 @item show arm disassembler
18866 Show the current disassembly style.
18868 @item set arm apcs32
18869 @cindex ARM 32-bit mode
18870 This command toggles ARM operation mode between 32-bit and 26-bit.
18872 @item show arm apcs32
18873 Display the current usage of the ARM 32-bit mode.
18875 @item set arm fpu @var{fputype}
18876 This command sets the ARM floating-point unit (FPU) type. The
18877 argument @var{fputype} can be one of these:
18881 Determine the FPU type by querying the OS ABI.
18883 Software FPU, with mixed-endian doubles on little-endian ARM
18886 GCC-compiled FPA co-processor.
18888 Software FPU with pure-endian doubles.
18894 Show the current type of the FPU.
18897 This command forces @value{GDBN} to use the specified ABI.
18900 Show the currently used ABI.
18902 @item set arm fallback-mode (arm|thumb|auto)
18903 @value{GDBN} uses the symbol table, when available, to determine
18904 whether instructions are ARM or Thumb. This command controls
18905 @value{GDBN}'s default behavior when the symbol table is not
18906 available. The default is @samp{auto}, which causes @value{GDBN} to
18907 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18910 @item show arm fallback-mode
18911 Show the current fallback instruction mode.
18913 @item set arm force-mode (arm|thumb|auto)
18914 This command overrides use of the symbol table to determine whether
18915 instructions are ARM or Thumb. The default is @samp{auto}, which
18916 causes @value{GDBN} to use the symbol table and then the setting
18917 of @samp{set arm fallback-mode}.
18919 @item show arm force-mode
18920 Show the current forced instruction mode.
18922 @item set debug arm
18923 Toggle whether to display ARM-specific debugging messages from the ARM
18924 target support subsystem.
18926 @item show debug arm
18927 Show whether ARM-specific debugging messages are enabled.
18930 The following commands are available when an ARM target is debugged
18931 using the RDI interface:
18934 @item rdilogfile @r{[}@var{file}@r{]}
18936 @cindex ADP (Angel Debugger Protocol) logging
18937 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18938 With an argument, sets the log file to the specified @var{file}. With
18939 no argument, show the current log file name. The default log file is
18942 @item rdilogenable @r{[}@var{arg}@r{]}
18943 @kindex rdilogenable
18944 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18945 enables logging, with an argument 0 or @code{"no"} disables it. With
18946 no arguments displays the current setting. When logging is enabled,
18947 ADP packets exchanged between @value{GDBN} and the RDI target device
18948 are logged to a file.
18950 @item set rdiromatzero
18951 @kindex set rdiromatzero
18952 @cindex ROM at zero address, RDI
18953 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18954 vector catching is disabled, so that zero address can be used. If off
18955 (the default), vector catching is enabled. For this command to take
18956 effect, it needs to be invoked prior to the @code{target rdi} command.
18958 @item show rdiromatzero
18959 @kindex show rdiromatzero
18960 Show the current setting of ROM at zero address.
18962 @item set rdiheartbeat
18963 @kindex set rdiheartbeat
18964 @cindex RDI heartbeat
18965 Enable or disable RDI heartbeat packets. It is not recommended to
18966 turn on this option, since it confuses ARM and EPI JTAG interface, as
18967 well as the Angel monitor.
18969 @item show rdiheartbeat
18970 @kindex show rdiheartbeat
18971 Show the setting of RDI heartbeat packets.
18975 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18976 The @value{GDBN} ARM simulator accepts the following optional arguments.
18979 @item --swi-support=@var{type}
18980 Tell the simulator which SWI interfaces to support.
18981 @var{type} may be a comma separated list of the following values.
18982 The default value is @code{all}.
18995 @subsection Renesas M32R/D and M32R/SDI
18998 @kindex target m32r
18999 @item target m32r @var{dev}
19000 Renesas M32R/D ROM monitor.
19002 @kindex target m32rsdi
19003 @item target m32rsdi @var{dev}
19004 Renesas M32R SDI server, connected via parallel port to the board.
19007 The following @value{GDBN} commands are specific to the M32R monitor:
19010 @item set download-path @var{path}
19011 @kindex set download-path
19012 @cindex find downloadable @sc{srec} files (M32R)
19013 Set the default path for finding downloadable @sc{srec} files.
19015 @item show download-path
19016 @kindex show download-path
19017 Show the default path for downloadable @sc{srec} files.
19019 @item set board-address @var{addr}
19020 @kindex set board-address
19021 @cindex M32-EVA target board address
19022 Set the IP address for the M32R-EVA target board.
19024 @item show board-address
19025 @kindex show board-address
19026 Show the current IP address of the target board.
19028 @item set server-address @var{addr}
19029 @kindex set server-address
19030 @cindex download server address (M32R)
19031 Set the IP address for the download server, which is the @value{GDBN}'s
19034 @item show server-address
19035 @kindex show server-address
19036 Display the IP address of the download server.
19038 @item upload @r{[}@var{file}@r{]}
19039 @kindex upload@r{, M32R}
19040 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19041 upload capability. If no @var{file} argument is given, the current
19042 executable file is uploaded.
19044 @item tload @r{[}@var{file}@r{]}
19045 @kindex tload@r{, M32R}
19046 Test the @code{upload} command.
19049 The following commands are available for M32R/SDI:
19054 @cindex reset SDI connection, M32R
19055 This command resets the SDI connection.
19059 This command shows the SDI connection status.
19062 @kindex debug_chaos
19063 @cindex M32R/Chaos debugging
19064 Instructs the remote that M32R/Chaos debugging is to be used.
19066 @item use_debug_dma
19067 @kindex use_debug_dma
19068 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19071 @kindex use_mon_code
19072 Instructs the remote to use the MON_CODE method of accessing memory.
19075 @kindex use_ib_break
19076 Instructs the remote to set breakpoints by IB break.
19078 @item use_dbt_break
19079 @kindex use_dbt_break
19080 Instructs the remote to set breakpoints by DBT.
19086 The Motorola m68k configuration includes ColdFire support, and a
19087 target command for the following ROM monitor.
19091 @kindex target dbug
19092 @item target dbug @var{dev}
19093 dBUG ROM monitor for Motorola ColdFire.
19098 @subsection MicroBlaze
19099 @cindex Xilinx MicroBlaze
19100 @cindex XMD, Xilinx Microprocessor Debugger
19102 The MicroBlaze is a soft-core processor supported on various Xilinx
19103 FPGAs, such as Spartan or Virtex series. Boards with these processors
19104 usually have JTAG ports which connect to a host system running the Xilinx
19105 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19106 This host system is used to download the configuration bitstream to
19107 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19108 communicates with the target board using the JTAG interface and
19109 presents a @code{gdbserver} interface to the board. By default
19110 @code{xmd} uses port @code{1234}. (While it is possible to change
19111 this default port, it requires the use of undocumented @code{xmd}
19112 commands. Contact Xilinx support if you need to do this.)
19114 Use these GDB commands to connect to the MicroBlaze target processor.
19117 @item target remote :1234
19118 Use this command to connect to the target if you are running @value{GDBN}
19119 on the same system as @code{xmd}.
19121 @item target remote @var{xmd-host}:1234
19122 Use this command to connect to the target if it is connected to @code{xmd}
19123 running on a different system named @var{xmd-host}.
19126 Use this command to download a program to the MicroBlaze target.
19128 @item set debug microblaze @var{n}
19129 Enable MicroBlaze-specific debugging messages if non-zero.
19131 @item show debug microblaze @var{n}
19132 Show MicroBlaze-specific debugging level.
19135 @node MIPS Embedded
19136 @subsection MIPS Embedded
19138 @cindex MIPS boards
19139 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19140 MIPS board attached to a serial line. This is available when
19141 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19144 Use these @value{GDBN} commands to specify the connection to your target board:
19147 @item target mips @var{port}
19148 @kindex target mips @var{port}
19149 To run a program on the board, start up @code{@value{GDBP}} with the
19150 name of your program as the argument. To connect to the board, use the
19151 command @samp{target mips @var{port}}, where @var{port} is the name of
19152 the serial port connected to the board. If the program has not already
19153 been downloaded to the board, you may use the @code{load} command to
19154 download it. You can then use all the usual @value{GDBN} commands.
19156 For example, this sequence connects to the target board through a serial
19157 port, and loads and runs a program called @var{prog} through the
19161 host$ @value{GDBP} @var{prog}
19162 @value{GDBN} is free software and @dots{}
19163 (@value{GDBP}) target mips /dev/ttyb
19164 (@value{GDBP}) load @var{prog}
19168 @item target mips @var{hostname}:@var{portnumber}
19169 On some @value{GDBN} host configurations, you can specify a TCP
19170 connection (for instance, to a serial line managed by a terminal
19171 concentrator) instead of a serial port, using the syntax
19172 @samp{@var{hostname}:@var{portnumber}}.
19174 @item target pmon @var{port}
19175 @kindex target pmon @var{port}
19178 @item target ddb @var{port}
19179 @kindex target ddb @var{port}
19180 NEC's DDB variant of PMON for Vr4300.
19182 @item target lsi @var{port}
19183 @kindex target lsi @var{port}
19184 LSI variant of PMON.
19186 @kindex target r3900
19187 @item target r3900 @var{dev}
19188 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19190 @kindex target array
19191 @item target array @var{dev}
19192 Array Tech LSI33K RAID controller board.
19198 @value{GDBN} also supports these special commands for MIPS targets:
19201 @item set mipsfpu double
19202 @itemx set mipsfpu single
19203 @itemx set mipsfpu none
19204 @itemx set mipsfpu auto
19205 @itemx show mipsfpu
19206 @kindex set mipsfpu
19207 @kindex show mipsfpu
19208 @cindex MIPS remote floating point
19209 @cindex floating point, MIPS remote
19210 If your target board does not support the MIPS floating point
19211 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19212 need this, you may wish to put the command in your @value{GDBN} init
19213 file). This tells @value{GDBN} how to find the return value of
19214 functions which return floating point values. It also allows
19215 @value{GDBN} to avoid saving the floating point registers when calling
19216 functions on the board. If you are using a floating point coprocessor
19217 with only single precision floating point support, as on the @sc{r4650}
19218 processor, use the command @samp{set mipsfpu single}. The default
19219 double precision floating point coprocessor may be selected using
19220 @samp{set mipsfpu double}.
19222 In previous versions the only choices were double precision or no
19223 floating point, so @samp{set mipsfpu on} will select double precision
19224 and @samp{set mipsfpu off} will select no floating point.
19226 As usual, you can inquire about the @code{mipsfpu} variable with
19227 @samp{show mipsfpu}.
19229 @item set timeout @var{seconds}
19230 @itemx set retransmit-timeout @var{seconds}
19231 @itemx show timeout
19232 @itemx show retransmit-timeout
19233 @cindex @code{timeout}, MIPS protocol
19234 @cindex @code{retransmit-timeout}, MIPS protocol
19235 @kindex set timeout
19236 @kindex show timeout
19237 @kindex set retransmit-timeout
19238 @kindex show retransmit-timeout
19239 You can control the timeout used while waiting for a packet, in the MIPS
19240 remote protocol, with the @code{set timeout @var{seconds}} command. The
19241 default is 5 seconds. Similarly, you can control the timeout used while
19242 waiting for an acknowledgment of a packet with the @code{set
19243 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19244 You can inspect both values with @code{show timeout} and @code{show
19245 retransmit-timeout}. (These commands are @emph{only} available when
19246 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19248 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19249 is waiting for your program to stop. In that case, @value{GDBN} waits
19250 forever because it has no way of knowing how long the program is going
19251 to run before stopping.
19253 @item set syn-garbage-limit @var{num}
19254 @kindex set syn-garbage-limit@r{, MIPS remote}
19255 @cindex synchronize with remote MIPS target
19256 Limit the maximum number of characters @value{GDBN} should ignore when
19257 it tries to synchronize with the remote target. The default is 10
19258 characters. Setting the limit to -1 means there's no limit.
19260 @item show syn-garbage-limit
19261 @kindex show syn-garbage-limit@r{, MIPS remote}
19262 Show the current limit on the number of characters to ignore when
19263 trying to synchronize with the remote system.
19265 @item set monitor-prompt @var{prompt}
19266 @kindex set monitor-prompt@r{, MIPS remote}
19267 @cindex remote monitor prompt
19268 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19269 remote monitor. The default depends on the target:
19279 @item show monitor-prompt
19280 @kindex show monitor-prompt@r{, MIPS remote}
19281 Show the current strings @value{GDBN} expects as the prompt from the
19284 @item set monitor-warnings
19285 @kindex set monitor-warnings@r{, MIPS remote}
19286 Enable or disable monitor warnings about hardware breakpoints. This
19287 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19288 display warning messages whose codes are returned by the @code{lsi}
19289 PMON monitor for breakpoint commands.
19291 @item show monitor-warnings
19292 @kindex show monitor-warnings@r{, MIPS remote}
19293 Show the current setting of printing monitor warnings.
19295 @item pmon @var{command}
19296 @kindex pmon@r{, MIPS remote}
19297 @cindex send PMON command
19298 This command allows sending an arbitrary @var{command} string to the
19299 monitor. The monitor must be in debug mode for this to work.
19302 @node OpenRISC 1000
19303 @subsection OpenRISC 1000
19304 @cindex OpenRISC 1000
19306 @cindex or1k boards
19307 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19308 about platform and commands.
19312 @kindex target jtag
19313 @item target jtag jtag://@var{host}:@var{port}
19315 Connects to remote JTAG server.
19316 JTAG remote server can be either an or1ksim or JTAG server,
19317 connected via parallel port to the board.
19319 Example: @code{target jtag jtag://localhost:9999}
19322 @item or1ksim @var{command}
19323 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19324 Simulator, proprietary commands can be executed.
19326 @kindex info or1k spr
19327 @item info or1k spr
19328 Displays spr groups.
19330 @item info or1k spr @var{group}
19331 @itemx info or1k spr @var{groupno}
19332 Displays register names in selected group.
19334 @item info or1k spr @var{group} @var{register}
19335 @itemx info or1k spr @var{register}
19336 @itemx info or1k spr @var{groupno} @var{registerno}
19337 @itemx info or1k spr @var{registerno}
19338 Shows information about specified spr register.
19341 @item spr @var{group} @var{register} @var{value}
19342 @itemx spr @var{register @var{value}}
19343 @itemx spr @var{groupno} @var{registerno @var{value}}
19344 @itemx spr @var{registerno @var{value}}
19345 Writes @var{value} to specified spr register.
19348 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19349 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19350 program execution and is thus much faster. Hardware breakpoints/watchpoint
19351 triggers can be set using:
19354 Load effective address/data
19356 Store effective address/data
19358 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19363 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19364 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19366 @code{htrace} commands:
19367 @cindex OpenRISC 1000 htrace
19370 @item hwatch @var{conditional}
19371 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19372 or Data. For example:
19374 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19376 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19380 Display information about current HW trace configuration.
19382 @item htrace trigger @var{conditional}
19383 Set starting criteria for HW trace.
19385 @item htrace qualifier @var{conditional}
19386 Set acquisition qualifier for HW trace.
19388 @item htrace stop @var{conditional}
19389 Set HW trace stopping criteria.
19391 @item htrace record [@var{data}]*
19392 Selects the data to be recorded, when qualifier is met and HW trace was
19395 @item htrace enable
19396 @itemx htrace disable
19397 Enables/disables the HW trace.
19399 @item htrace rewind [@var{filename}]
19400 Clears currently recorded trace data.
19402 If filename is specified, new trace file is made and any newly collected data
19403 will be written there.
19405 @item htrace print [@var{start} [@var{len}]]
19406 Prints trace buffer, using current record configuration.
19408 @item htrace mode continuous
19409 Set continuous trace mode.
19411 @item htrace mode suspend
19412 Set suspend trace mode.
19416 @node PowerPC Embedded
19417 @subsection PowerPC Embedded
19419 @cindex DVC register
19420 @value{GDBN} supports using the DVC (Data Value Compare) register to
19421 implement in hardware simple hardware watchpoint conditions of the form:
19424 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19425 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19428 The DVC register will be automatically used when @value{GDBN} detects
19429 such pattern in a condition expression, and the created watchpoint uses one
19430 debug register (either the @code{exact-watchpoints} option is on and the
19431 variable is scalar, or the variable has a length of one byte). This feature
19432 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19435 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19436 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19437 in which case watchpoints using only one debug register are created when
19438 watching variables of scalar types.
19440 You can create an artificial array to watch an arbitrary memory
19441 region using one of the following commands (@pxref{Expressions}):
19444 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19445 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19448 PowerPC embedded processors support masked watchpoints. See the discussion
19449 about the @code{mask} argument in @ref{Set Watchpoints}.
19451 @cindex ranged breakpoint
19452 PowerPC embedded processors support hardware accelerated
19453 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19454 the inferior whenever it executes an instruction at any address within
19455 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19456 use the @code{break-range} command.
19458 @value{GDBN} provides the following PowerPC-specific commands:
19461 @kindex break-range
19462 @item break-range @var{start-location}, @var{end-location}
19463 Set a breakpoint for an address range.
19464 @var{start-location} and @var{end-location} can specify a function name,
19465 a line number, an offset of lines from the current line or from the start
19466 location, or an address of an instruction (see @ref{Specify Location},
19467 for a list of all the possible ways to specify a @var{location}.)
19468 The breakpoint will stop execution of the inferior whenever it
19469 executes an instruction at any address within the specified range,
19470 (including @var{start-location} and @var{end-location}.)
19472 @kindex set powerpc
19473 @item set powerpc soft-float
19474 @itemx show powerpc soft-float
19475 Force @value{GDBN} to use (or not use) a software floating point calling
19476 convention. By default, @value{GDBN} selects the calling convention based
19477 on the selected architecture and the provided executable file.
19479 @item set powerpc vector-abi
19480 @itemx show powerpc vector-abi
19481 Force @value{GDBN} to use the specified calling convention for vector
19482 arguments and return values. The valid options are @samp{auto};
19483 @samp{generic}, to avoid vector registers even if they are present;
19484 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19485 registers. By default, @value{GDBN} selects the calling convention
19486 based on the selected architecture and the provided executable file.
19488 @item set powerpc exact-watchpoints
19489 @itemx show powerpc exact-watchpoints
19490 Allow @value{GDBN} to use only one debug register when watching a variable
19491 of scalar type, thus assuming that the variable is accessed through the
19492 address of its first byte.
19494 @kindex target dink32
19495 @item target dink32 @var{dev}
19496 DINK32 ROM monitor.
19498 @kindex target ppcbug
19499 @item target ppcbug @var{dev}
19500 @kindex target ppcbug1
19501 @item target ppcbug1 @var{dev}
19502 PPCBUG ROM monitor for PowerPC.
19505 @item target sds @var{dev}
19506 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19509 @cindex SDS protocol
19510 The following commands specific to the SDS protocol are supported
19514 @item set sdstimeout @var{nsec}
19515 @kindex set sdstimeout
19516 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19517 default is 2 seconds.
19519 @item show sdstimeout
19520 @kindex show sdstimeout
19521 Show the current value of the SDS timeout.
19523 @item sds @var{command}
19524 @kindex sds@r{, a command}
19525 Send the specified @var{command} string to the SDS monitor.
19530 @subsection HP PA Embedded
19534 @kindex target op50n
19535 @item target op50n @var{dev}
19536 OP50N monitor, running on an OKI HPPA board.
19538 @kindex target w89k
19539 @item target w89k @var{dev}
19540 W89K monitor, running on a Winbond HPPA board.
19545 @subsection Tsqware Sparclet
19549 @value{GDBN} enables developers to debug tasks running on
19550 Sparclet targets from a Unix host.
19551 @value{GDBN} uses code that runs on
19552 both the Unix host and on the Sparclet target. The program
19553 @code{@value{GDBP}} is installed and executed on the Unix host.
19556 @item remotetimeout @var{args}
19557 @kindex remotetimeout
19558 @value{GDBN} supports the option @code{remotetimeout}.
19559 This option is set by the user, and @var{args} represents the number of
19560 seconds @value{GDBN} waits for responses.
19563 @cindex compiling, on Sparclet
19564 When compiling for debugging, include the options @samp{-g} to get debug
19565 information and @samp{-Ttext} to relocate the program to where you wish to
19566 load it on the target. You may also want to add the options @samp{-n} or
19567 @samp{-N} in order to reduce the size of the sections. Example:
19570 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19573 You can use @code{objdump} to verify that the addresses are what you intended:
19576 sparclet-aout-objdump --headers --syms prog
19579 @cindex running, on Sparclet
19581 your Unix execution search path to find @value{GDBN}, you are ready to
19582 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19583 (or @code{sparclet-aout-gdb}, depending on your installation).
19585 @value{GDBN} comes up showing the prompt:
19592 * Sparclet File:: Setting the file to debug
19593 * Sparclet Connection:: Connecting to Sparclet
19594 * Sparclet Download:: Sparclet download
19595 * Sparclet Execution:: Running and debugging
19598 @node Sparclet File
19599 @subsubsection Setting File to Debug
19601 The @value{GDBN} command @code{file} lets you choose with program to debug.
19604 (gdbslet) file prog
19608 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19609 @value{GDBN} locates
19610 the file by searching the directories listed in the command search
19612 If the file was compiled with debug information (option @samp{-g}), source
19613 files will be searched as well.
19614 @value{GDBN} locates
19615 the source files by searching the directories listed in the directory search
19616 path (@pxref{Environment, ,Your Program's Environment}).
19618 to find a file, it displays a message such as:
19621 prog: No such file or directory.
19624 When this happens, add the appropriate directories to the search paths with
19625 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19626 @code{target} command again.
19628 @node Sparclet Connection
19629 @subsubsection Connecting to Sparclet
19631 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19632 To connect to a target on serial port ``@code{ttya}'', type:
19635 (gdbslet) target sparclet /dev/ttya
19636 Remote target sparclet connected to /dev/ttya
19637 main () at ../prog.c:3
19641 @value{GDBN} displays messages like these:
19647 @node Sparclet Download
19648 @subsubsection Sparclet Download
19650 @cindex download to Sparclet
19651 Once connected to the Sparclet target,
19652 you can use the @value{GDBN}
19653 @code{load} command to download the file from the host to the target.
19654 The file name and load offset should be given as arguments to the @code{load}
19656 Since the file format is aout, the program must be loaded to the starting
19657 address. You can use @code{objdump} to find out what this value is. The load
19658 offset is an offset which is added to the VMA (virtual memory address)
19659 of each of the file's sections.
19660 For instance, if the program
19661 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19662 and bss at 0x12010170, in @value{GDBN}, type:
19665 (gdbslet) load prog 0x12010000
19666 Loading section .text, size 0xdb0 vma 0x12010000
19669 If the code is loaded at a different address then what the program was linked
19670 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19671 to tell @value{GDBN} where to map the symbol table.
19673 @node Sparclet Execution
19674 @subsubsection Running and Debugging
19676 @cindex running and debugging Sparclet programs
19677 You can now begin debugging the task using @value{GDBN}'s execution control
19678 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19679 manual for the list of commands.
19683 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19685 Starting program: prog
19686 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19687 3 char *symarg = 0;
19689 4 char *execarg = "hello!";
19694 @subsection Fujitsu Sparclite
19698 @kindex target sparclite
19699 @item target sparclite @var{dev}
19700 Fujitsu sparclite boards, used only for the purpose of loading.
19701 You must use an additional command to debug the program.
19702 For example: target remote @var{dev} using @value{GDBN} standard
19708 @subsection Zilog Z8000
19711 @cindex simulator, Z8000
19712 @cindex Zilog Z8000 simulator
19714 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19717 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19718 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19719 segmented variant). The simulator recognizes which architecture is
19720 appropriate by inspecting the object code.
19723 @item target sim @var{args}
19725 @kindex target sim@r{, with Z8000}
19726 Debug programs on a simulated CPU. If the simulator supports setup
19727 options, specify them via @var{args}.
19731 After specifying this target, you can debug programs for the simulated
19732 CPU in the same style as programs for your host computer; use the
19733 @code{file} command to load a new program image, the @code{run} command
19734 to run your program, and so on.
19736 As well as making available all the usual machine registers
19737 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19738 additional items of information as specially named registers:
19743 Counts clock-ticks in the simulator.
19746 Counts instructions run in the simulator.
19749 Execution time in 60ths of a second.
19753 You can refer to these values in @value{GDBN} expressions with the usual
19754 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19755 conditional breakpoint that suspends only after at least 5000
19756 simulated clock ticks.
19759 @subsection Atmel AVR
19762 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19763 following AVR-specific commands:
19766 @item info io_registers
19767 @kindex info io_registers@r{, AVR}
19768 @cindex I/O registers (Atmel AVR)
19769 This command displays information about the AVR I/O registers. For
19770 each register, @value{GDBN} prints its number and value.
19777 When configured for debugging CRIS, @value{GDBN} provides the
19778 following CRIS-specific commands:
19781 @item set cris-version @var{ver}
19782 @cindex CRIS version
19783 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19784 The CRIS version affects register names and sizes. This command is useful in
19785 case autodetection of the CRIS version fails.
19787 @item show cris-version
19788 Show the current CRIS version.
19790 @item set cris-dwarf2-cfi
19791 @cindex DWARF-2 CFI and CRIS
19792 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19793 Change to @samp{off} when using @code{gcc-cris} whose version is below
19796 @item show cris-dwarf2-cfi
19797 Show the current state of using DWARF-2 CFI.
19799 @item set cris-mode @var{mode}
19801 Set the current CRIS mode to @var{mode}. It should only be changed when
19802 debugging in guru mode, in which case it should be set to
19803 @samp{guru} (the default is @samp{normal}).
19805 @item show cris-mode
19806 Show the current CRIS mode.
19810 @subsection Renesas Super-H
19813 For the Renesas Super-H processor, @value{GDBN} provides these
19818 @kindex regs@r{, Super-H}
19819 Show the values of all Super-H registers.
19821 @item set sh calling-convention @var{convention}
19822 @kindex set sh calling-convention
19823 Set the calling-convention used when calling functions from @value{GDBN}.
19824 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19825 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19826 convention. If the DWARF-2 information of the called function specifies
19827 that the function follows the Renesas calling convention, the function
19828 is called using the Renesas calling convention. If the calling convention
19829 is set to @samp{renesas}, the Renesas calling convention is always used,
19830 regardless of the DWARF-2 information. This can be used to override the
19831 default of @samp{gcc} if debug information is missing, or the compiler
19832 does not emit the DWARF-2 calling convention entry for a function.
19834 @item show sh calling-convention
19835 @kindex show sh calling-convention
19836 Show the current calling convention setting.
19841 @node Architectures
19842 @section Architectures
19844 This section describes characteristics of architectures that affect
19845 all uses of @value{GDBN} with the architecture, both native and cross.
19852 * HPPA:: HP PA architecture
19853 * SPU:: Cell Broadband Engine SPU architecture
19858 @subsection x86 Architecture-specific Issues
19861 @item set struct-convention @var{mode}
19862 @kindex set struct-convention
19863 @cindex struct return convention
19864 @cindex struct/union returned in registers
19865 Set the convention used by the inferior to return @code{struct}s and
19866 @code{union}s from functions to @var{mode}. Possible values of
19867 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19868 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19869 are returned on the stack, while @code{"reg"} means that a
19870 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19871 be returned in a register.
19873 @item show struct-convention
19874 @kindex show struct-convention
19875 Show the current setting of the convention to return @code{struct}s
19884 @kindex set rstack_high_address
19885 @cindex AMD 29K register stack
19886 @cindex register stack, AMD29K
19887 @item set rstack_high_address @var{address}
19888 On AMD 29000 family processors, registers are saved in a separate
19889 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19890 extent of this stack. Normally, @value{GDBN} just assumes that the
19891 stack is ``large enough''. This may result in @value{GDBN} referencing
19892 memory locations that do not exist. If necessary, you can get around
19893 this problem by specifying the ending address of the register stack with
19894 the @code{set rstack_high_address} command. The argument should be an
19895 address, which you probably want to precede with @samp{0x} to specify in
19898 @kindex show rstack_high_address
19899 @item show rstack_high_address
19900 Display the current limit of the register stack, on AMD 29000 family
19908 See the following section.
19913 @cindex stack on Alpha
19914 @cindex stack on MIPS
19915 @cindex Alpha stack
19917 Alpha- and MIPS-based computers use an unusual stack frame, which
19918 sometimes requires @value{GDBN} to search backward in the object code to
19919 find the beginning of a function.
19921 @cindex response time, MIPS debugging
19922 To improve response time (especially for embedded applications, where
19923 @value{GDBN} may be restricted to a slow serial line for this search)
19924 you may want to limit the size of this search, using one of these
19928 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19929 @item set heuristic-fence-post @var{limit}
19930 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19931 search for the beginning of a function. A value of @var{0} (the
19932 default) means there is no limit. However, except for @var{0}, the
19933 larger the limit the more bytes @code{heuristic-fence-post} must search
19934 and therefore the longer it takes to run. You should only need to use
19935 this command when debugging a stripped executable.
19937 @item show heuristic-fence-post
19938 Display the current limit.
19942 These commands are available @emph{only} when @value{GDBN} is configured
19943 for debugging programs on Alpha or MIPS processors.
19945 Several MIPS-specific commands are available when debugging MIPS
19949 @item set mips abi @var{arg}
19950 @kindex set mips abi
19951 @cindex set ABI for MIPS
19952 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19953 values of @var{arg} are:
19957 The default ABI associated with the current binary (this is the
19967 @item show mips abi
19968 @kindex show mips abi
19969 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19972 @itemx show mipsfpu
19973 @xref{MIPS Embedded, set mipsfpu}.
19975 @item set mips mask-address @var{arg}
19976 @kindex set mips mask-address
19977 @cindex MIPS addresses, masking
19978 This command determines whether the most-significant 32 bits of 64-bit
19979 MIPS addresses are masked off. The argument @var{arg} can be
19980 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19981 setting, which lets @value{GDBN} determine the correct value.
19983 @item show mips mask-address
19984 @kindex show mips mask-address
19985 Show whether the upper 32 bits of MIPS addresses are masked off or
19988 @item set remote-mips64-transfers-32bit-regs
19989 @kindex set remote-mips64-transfers-32bit-regs
19990 This command controls compatibility with 64-bit MIPS targets that
19991 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19992 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19993 and 64 bits for other registers, set this option to @samp{on}.
19995 @item show remote-mips64-transfers-32bit-regs
19996 @kindex show remote-mips64-transfers-32bit-regs
19997 Show the current setting of compatibility with older MIPS 64 targets.
19999 @item set debug mips
20000 @kindex set debug mips
20001 This command turns on and off debugging messages for the MIPS-specific
20002 target code in @value{GDBN}.
20004 @item show debug mips
20005 @kindex show debug mips
20006 Show the current setting of MIPS debugging messages.
20012 @cindex HPPA support
20014 When @value{GDBN} is debugging the HP PA architecture, it provides the
20015 following special commands:
20018 @item set debug hppa
20019 @kindex set debug hppa
20020 This command determines whether HPPA architecture-specific debugging
20021 messages are to be displayed.
20023 @item show debug hppa
20024 Show whether HPPA debugging messages are displayed.
20026 @item maint print unwind @var{address}
20027 @kindex maint print unwind@r{, HPPA}
20028 This command displays the contents of the unwind table entry at the
20029 given @var{address}.
20035 @subsection Cell Broadband Engine SPU architecture
20036 @cindex Cell Broadband Engine
20039 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20040 it provides the following special commands:
20043 @item info spu event
20045 Display SPU event facility status. Shows current event mask
20046 and pending event status.
20048 @item info spu signal
20049 Display SPU signal notification facility status. Shows pending
20050 signal-control word and signal notification mode of both signal
20051 notification channels.
20053 @item info spu mailbox
20054 Display SPU mailbox facility status. Shows all pending entries,
20055 in order of processing, in each of the SPU Write Outbound,
20056 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20059 Display MFC DMA status. Shows all pending commands in the MFC
20060 DMA queue. For each entry, opcode, tag, class IDs, effective
20061 and local store addresses and transfer size are shown.
20063 @item info spu proxydma
20064 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20065 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20066 and local store addresses and transfer size are shown.
20070 When @value{GDBN} is debugging a combined PowerPC/SPU application
20071 on the Cell Broadband Engine, it provides in addition the following
20075 @item set spu stop-on-load @var{arg}
20077 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20078 will give control to the user when a new SPE thread enters its @code{main}
20079 function. The default is @code{off}.
20081 @item show spu stop-on-load
20083 Show whether to stop for new SPE threads.
20085 @item set spu auto-flush-cache @var{arg}
20086 Set whether to automatically flush the software-managed cache. When set to
20087 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20088 cache to be flushed whenever SPE execution stops. This provides a consistent
20089 view of PowerPC memory that is accessed via the cache. If an application
20090 does not use the software-managed cache, this option has no effect.
20092 @item show spu auto-flush-cache
20093 Show whether to automatically flush the software-managed cache.
20098 @subsection PowerPC
20099 @cindex PowerPC architecture
20101 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20102 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20103 numbers stored in the floating point registers. These values must be stored
20104 in two consecutive registers, always starting at an even register like
20105 @code{f0} or @code{f2}.
20107 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20108 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20109 @code{f2} and @code{f3} for @code{$dl1} and so on.
20111 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20112 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20115 @node Controlling GDB
20116 @chapter Controlling @value{GDBN}
20118 You can alter the way @value{GDBN} interacts with you by using the
20119 @code{set} command. For commands controlling how @value{GDBN} displays
20120 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20125 * Editing:: Command editing
20126 * Command History:: Command history
20127 * Screen Size:: Screen size
20128 * Numbers:: Numbers
20129 * ABI:: Configuring the current ABI
20130 * Messages/Warnings:: Optional warnings and messages
20131 * Debugging Output:: Optional messages about internal happenings
20132 * Other Misc Settings:: Other Miscellaneous Settings
20140 @value{GDBN} indicates its readiness to read a command by printing a string
20141 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20142 can change the prompt string with the @code{set prompt} command. For
20143 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20144 the prompt in one of the @value{GDBN} sessions so that you can always tell
20145 which one you are talking to.
20147 @emph{Note:} @code{set prompt} does not add a space for you after the
20148 prompt you set. This allows you to set a prompt which ends in a space
20149 or a prompt that does not.
20153 @item set prompt @var{newprompt}
20154 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20156 @kindex show prompt
20158 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20161 Versions of @value{GDBN} that ship with Python scripting enabled have
20162 prompt extensions. The commands for interacting with these extensions
20166 @kindex set extended-prompt
20167 @item set extended-prompt @var{prompt}
20168 Set an extended prompt that allows for substitutions.
20169 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20170 substitution. Any escape sequences specified as part of the prompt
20171 string are replaced with the corresponding strings each time the prompt
20177 set extended-prompt Current working directory: \w (gdb)
20180 Note that when an extended-prompt is set, it takes control of the
20181 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20183 @kindex show extended-prompt
20184 @item show extended-prompt
20185 Prints the extended prompt. Any escape sequences specified as part of
20186 the prompt string with @code{set extended-prompt}, are replaced with the
20187 corresponding strings each time the prompt is displayed.
20191 @section Command Editing
20193 @cindex command line editing
20195 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20196 @sc{gnu} library provides consistent behavior for programs which provide a
20197 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20198 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20199 substitution, and a storage and recall of command history across
20200 debugging sessions.
20202 You may control the behavior of command line editing in @value{GDBN} with the
20203 command @code{set}.
20206 @kindex set editing
20209 @itemx set editing on
20210 Enable command line editing (enabled by default).
20212 @item set editing off
20213 Disable command line editing.
20215 @kindex show editing
20217 Show whether command line editing is enabled.
20220 @ifset SYSTEM_READLINE
20221 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20223 @ifclear SYSTEM_READLINE
20224 @xref{Command Line Editing},
20226 for more details about the Readline
20227 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20228 encouraged to read that chapter.
20230 @node Command History
20231 @section Command History
20232 @cindex command history
20234 @value{GDBN} can keep track of the commands you type during your
20235 debugging sessions, so that you can be certain of precisely what
20236 happened. Use these commands to manage the @value{GDBN} command
20239 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20240 package, to provide the history facility.
20241 @ifset SYSTEM_READLINE
20242 @xref{Using History Interactively, , , history, GNU History Library},
20244 @ifclear SYSTEM_READLINE
20245 @xref{Using History Interactively},
20247 for the detailed description of the History library.
20249 To issue a command to @value{GDBN} without affecting certain aspects of
20250 the state which is seen by users, prefix it with @samp{server }
20251 (@pxref{Server Prefix}). This
20252 means that this command will not affect the command history, nor will it
20253 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20254 pressed on a line by itself.
20256 @cindex @code{server}, command prefix
20257 The server prefix does not affect the recording of values into the value
20258 history; to print a value without recording it into the value history,
20259 use the @code{output} command instead of the @code{print} command.
20261 Here is the description of @value{GDBN} commands related to command
20265 @cindex history substitution
20266 @cindex history file
20267 @kindex set history filename
20268 @cindex @env{GDBHISTFILE}, environment variable
20269 @item set history filename @var{fname}
20270 Set the name of the @value{GDBN} command history file to @var{fname}.
20271 This is the file where @value{GDBN} reads an initial command history
20272 list, and where it writes the command history from this session when it
20273 exits. You can access this list through history expansion or through
20274 the history command editing characters listed below. This file defaults
20275 to the value of the environment variable @code{GDBHISTFILE}, or to
20276 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20279 @cindex save command history
20280 @kindex set history save
20281 @item set history save
20282 @itemx set history save on
20283 Record command history in a file, whose name may be specified with the
20284 @code{set history filename} command. By default, this option is disabled.
20286 @item set history save off
20287 Stop recording command history in a file.
20289 @cindex history size
20290 @kindex set history size
20291 @cindex @env{HISTSIZE}, environment variable
20292 @item set history size @var{size}
20293 Set the number of commands which @value{GDBN} keeps in its history list.
20294 This defaults to the value of the environment variable
20295 @code{HISTSIZE}, or to 256 if this variable is not set.
20298 History expansion assigns special meaning to the character @kbd{!}.
20299 @ifset SYSTEM_READLINE
20300 @xref{Event Designators, , , history, GNU History Library},
20302 @ifclear SYSTEM_READLINE
20303 @xref{Event Designators},
20307 @cindex history expansion, turn on/off
20308 Since @kbd{!} is also the logical not operator in C, history expansion
20309 is off by default. If you decide to enable history expansion with the
20310 @code{set history expansion on} command, you may sometimes need to
20311 follow @kbd{!} (when it is used as logical not, in an expression) with
20312 a space or a tab to prevent it from being expanded. The readline
20313 history facilities do not attempt substitution on the strings
20314 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20316 The commands to control history expansion are:
20319 @item set history expansion on
20320 @itemx set history expansion
20321 @kindex set history expansion
20322 Enable history expansion. History expansion is off by default.
20324 @item set history expansion off
20325 Disable history expansion.
20328 @kindex show history
20330 @itemx show history filename
20331 @itemx show history save
20332 @itemx show history size
20333 @itemx show history expansion
20334 These commands display the state of the @value{GDBN} history parameters.
20335 @code{show history} by itself displays all four states.
20340 @kindex show commands
20341 @cindex show last commands
20342 @cindex display command history
20343 @item show commands
20344 Display the last ten commands in the command history.
20346 @item show commands @var{n}
20347 Print ten commands centered on command number @var{n}.
20349 @item show commands +
20350 Print ten commands just after the commands last printed.
20354 @section Screen Size
20355 @cindex size of screen
20356 @cindex pauses in output
20358 Certain commands to @value{GDBN} may produce large amounts of
20359 information output to the screen. To help you read all of it,
20360 @value{GDBN} pauses and asks you for input at the end of each page of
20361 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20362 to discard the remaining output. Also, the screen width setting
20363 determines when to wrap lines of output. Depending on what is being
20364 printed, @value{GDBN} tries to break the line at a readable place,
20365 rather than simply letting it overflow onto the following line.
20367 Normally @value{GDBN} knows the size of the screen from the terminal
20368 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20369 together with the value of the @code{TERM} environment variable and the
20370 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20371 you can override it with the @code{set height} and @code{set
20378 @kindex show height
20379 @item set height @var{lpp}
20381 @itemx set width @var{cpl}
20383 These @code{set} commands specify a screen height of @var{lpp} lines and
20384 a screen width of @var{cpl} characters. The associated @code{show}
20385 commands display the current settings.
20387 If you specify a height of zero lines, @value{GDBN} does not pause during
20388 output no matter how long the output is. This is useful if output is to a
20389 file or to an editor buffer.
20391 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20392 from wrapping its output.
20394 @item set pagination on
20395 @itemx set pagination off
20396 @kindex set pagination
20397 Turn the output pagination on or off; the default is on. Turning
20398 pagination off is the alternative to @code{set height 0}. Note that
20399 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20400 Options, -batch}) also automatically disables pagination.
20402 @item show pagination
20403 @kindex show pagination
20404 Show the current pagination mode.
20409 @cindex number representation
20410 @cindex entering numbers
20412 You can always enter numbers in octal, decimal, or hexadecimal in
20413 @value{GDBN} by the usual conventions: octal numbers begin with
20414 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20415 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20416 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20417 10; likewise, the default display for numbers---when no particular
20418 format is specified---is base 10. You can change the default base for
20419 both input and output with the commands described below.
20422 @kindex set input-radix
20423 @item set input-radix @var{base}
20424 Set the default base for numeric input. Supported choices
20425 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20426 specified either unambiguously or using the current input radix; for
20430 set input-radix 012
20431 set input-radix 10.
20432 set input-radix 0xa
20436 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20437 leaves the input radix unchanged, no matter what it was, since
20438 @samp{10}, being without any leading or trailing signs of its base, is
20439 interpreted in the current radix. Thus, if the current radix is 16,
20440 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20443 @kindex set output-radix
20444 @item set output-radix @var{base}
20445 Set the default base for numeric display. Supported choices
20446 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20447 specified either unambiguously or using the current input radix.
20449 @kindex show input-radix
20450 @item show input-radix
20451 Display the current default base for numeric input.
20453 @kindex show output-radix
20454 @item show output-radix
20455 Display the current default base for numeric display.
20457 @item set radix @r{[}@var{base}@r{]}
20461 These commands set and show the default base for both input and output
20462 of numbers. @code{set radix} sets the radix of input and output to
20463 the same base; without an argument, it resets the radix back to its
20464 default value of 10.
20469 @section Configuring the Current ABI
20471 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20472 application automatically. However, sometimes you need to override its
20473 conclusions. Use these commands to manage @value{GDBN}'s view of the
20480 One @value{GDBN} configuration can debug binaries for multiple operating
20481 system targets, either via remote debugging or native emulation.
20482 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20483 but you can override its conclusion using the @code{set osabi} command.
20484 One example where this is useful is in debugging of binaries which use
20485 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20486 not have the same identifying marks that the standard C library for your
20491 Show the OS ABI currently in use.
20494 With no argument, show the list of registered available OS ABI's.
20496 @item set osabi @var{abi}
20497 Set the current OS ABI to @var{abi}.
20500 @cindex float promotion
20502 Generally, the way that an argument of type @code{float} is passed to a
20503 function depends on whether the function is prototyped. For a prototyped
20504 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20505 according to the architecture's convention for @code{float}. For unprototyped
20506 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20507 @code{double} and then passed.
20509 Unfortunately, some forms of debug information do not reliably indicate whether
20510 a function is prototyped. If @value{GDBN} calls a function that is not marked
20511 as prototyped, it consults @kbd{set coerce-float-to-double}.
20514 @kindex set coerce-float-to-double
20515 @item set coerce-float-to-double
20516 @itemx set coerce-float-to-double on
20517 Arguments of type @code{float} will be promoted to @code{double} when passed
20518 to an unprototyped function. This is the default setting.
20520 @item set coerce-float-to-double off
20521 Arguments of type @code{float} will be passed directly to unprototyped
20524 @kindex show coerce-float-to-double
20525 @item show coerce-float-to-double
20526 Show the current setting of promoting @code{float} to @code{double}.
20530 @kindex show cp-abi
20531 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20532 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20533 used to build your application. @value{GDBN} only fully supports
20534 programs with a single C@t{++} ABI; if your program contains code using
20535 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20536 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20537 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20538 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20539 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20540 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20545 Show the C@t{++} ABI currently in use.
20548 With no argument, show the list of supported C@t{++} ABI's.
20550 @item set cp-abi @var{abi}
20551 @itemx set cp-abi auto
20552 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20555 @node Messages/Warnings
20556 @section Optional Warnings and Messages
20558 @cindex verbose operation
20559 @cindex optional warnings
20560 By default, @value{GDBN} is silent about its inner workings. If you are
20561 running on a slow machine, you may want to use the @code{set verbose}
20562 command. This makes @value{GDBN} tell you when it does a lengthy
20563 internal operation, so you will not think it has crashed.
20565 Currently, the messages controlled by @code{set verbose} are those
20566 which announce that the symbol table for a source file is being read;
20567 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20570 @kindex set verbose
20571 @item set verbose on
20572 Enables @value{GDBN} output of certain informational messages.
20574 @item set verbose off
20575 Disables @value{GDBN} output of certain informational messages.
20577 @kindex show verbose
20579 Displays whether @code{set verbose} is on or off.
20582 By default, if @value{GDBN} encounters bugs in the symbol table of an
20583 object file, it is silent; but if you are debugging a compiler, you may
20584 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20589 @kindex set complaints
20590 @item set complaints @var{limit}
20591 Permits @value{GDBN} to output @var{limit} complaints about each type of
20592 unusual symbols before becoming silent about the problem. Set
20593 @var{limit} to zero to suppress all complaints; set it to a large number
20594 to prevent complaints from being suppressed.
20596 @kindex show complaints
20597 @item show complaints
20598 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20602 @anchor{confirmation requests}
20603 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20604 lot of stupid questions to confirm certain commands. For example, if
20605 you try to run a program which is already running:
20609 The program being debugged has been started already.
20610 Start it from the beginning? (y or n)
20613 If you are willing to unflinchingly face the consequences of your own
20614 commands, you can disable this ``feature'':
20618 @kindex set confirm
20620 @cindex confirmation
20621 @cindex stupid questions
20622 @item set confirm off
20623 Disables confirmation requests. Note that running @value{GDBN} with
20624 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20625 automatically disables confirmation requests.
20627 @item set confirm on
20628 Enables confirmation requests (the default).
20630 @kindex show confirm
20632 Displays state of confirmation requests.
20636 @cindex command tracing
20637 If you need to debug user-defined commands or sourced files you may find it
20638 useful to enable @dfn{command tracing}. In this mode each command will be
20639 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20640 quantity denoting the call depth of each command.
20643 @kindex set trace-commands
20644 @cindex command scripts, debugging
20645 @item set trace-commands on
20646 Enable command tracing.
20647 @item set trace-commands off
20648 Disable command tracing.
20649 @item show trace-commands
20650 Display the current state of command tracing.
20653 @node Debugging Output
20654 @section Optional Messages about Internal Happenings
20655 @cindex optional debugging messages
20657 @value{GDBN} has commands that enable optional debugging messages from
20658 various @value{GDBN} subsystems; normally these commands are of
20659 interest to @value{GDBN} maintainers, or when reporting a bug. This
20660 section documents those commands.
20663 @kindex set exec-done-display
20664 @item set exec-done-display
20665 Turns on or off the notification of asynchronous commands'
20666 completion. When on, @value{GDBN} will print a message when an
20667 asynchronous command finishes its execution. The default is off.
20668 @kindex show exec-done-display
20669 @item show exec-done-display
20670 Displays the current setting of asynchronous command completion
20673 @cindex gdbarch debugging info
20674 @cindex architecture debugging info
20675 @item set debug arch
20676 Turns on or off display of gdbarch debugging info. The default is off
20678 @item show debug arch
20679 Displays the current state of displaying gdbarch debugging info.
20680 @item set debug aix-thread
20681 @cindex AIX threads
20682 Display debugging messages about inner workings of the AIX thread
20684 @item show debug aix-thread
20685 Show the current state of AIX thread debugging info display.
20686 @item set debug check-physname
20688 Check the results of the ``physname'' computation. When reading DWARF
20689 debugging information for C@t{++}, @value{GDBN} attempts to compute
20690 each entity's name. @value{GDBN} can do this computation in two
20691 different ways, depending on exactly what information is present.
20692 When enabled, this setting causes @value{GDBN} to compute the names
20693 both ways and display any discrepancies.
20694 @item show debug check-physname
20695 Show the current state of ``physname'' checking.
20696 @item set debug dwarf2-die
20697 @cindex DWARF2 DIEs
20698 Dump DWARF2 DIEs after they are read in.
20699 The value is the number of nesting levels to print.
20700 A value of zero turns off the display.
20701 @item show debug dwarf2-die
20702 Show the current state of DWARF2 DIE debugging.
20703 @item set debug displaced
20704 @cindex displaced stepping debugging info
20705 Turns on or off display of @value{GDBN} debugging info for the
20706 displaced stepping support. The default is off.
20707 @item show debug displaced
20708 Displays the current state of displaying @value{GDBN} debugging info
20709 related to displaced stepping.
20710 @item set debug event
20711 @cindex event debugging info
20712 Turns on or off display of @value{GDBN} event debugging info. The
20714 @item show debug event
20715 Displays the current state of displaying @value{GDBN} event debugging
20717 @item set debug expression
20718 @cindex expression debugging info
20719 Turns on or off display of debugging info about @value{GDBN}
20720 expression parsing. The default is off.
20721 @item show debug expression
20722 Displays the current state of displaying debugging info about
20723 @value{GDBN} expression parsing.
20724 @item set debug frame
20725 @cindex frame debugging info
20726 Turns on or off display of @value{GDBN} frame debugging info. The
20728 @item show debug frame
20729 Displays the current state of displaying @value{GDBN} frame debugging
20731 @item set debug gnu-nat
20732 @cindex @sc{gnu}/Hurd debug messages
20733 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20734 @item show debug gnu-nat
20735 Show the current state of @sc{gnu}/Hurd debugging messages.
20736 @item set debug infrun
20737 @cindex inferior debugging info
20738 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20739 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20740 for implementing operations such as single-stepping the inferior.
20741 @item show debug infrun
20742 Displays the current state of @value{GDBN} inferior debugging.
20743 @item set debug jit
20744 @cindex just-in-time compilation, debugging messages
20745 Turns on or off debugging messages from JIT debug support.
20746 @item show debug jit
20747 Displays the current state of @value{GDBN} JIT debugging.
20748 @item set debug lin-lwp
20749 @cindex @sc{gnu}/Linux LWP debug messages
20750 @cindex Linux lightweight processes
20751 Turns on or off debugging messages from the Linux LWP debug support.
20752 @item show debug lin-lwp
20753 Show the current state of Linux LWP debugging messages.
20754 @item set debug observer
20755 @cindex observer debugging info
20756 Turns on or off display of @value{GDBN} observer debugging. This
20757 includes info such as the notification of observable events.
20758 @item show debug observer
20759 Displays the current state of observer debugging.
20760 @item set debug overload
20761 @cindex C@t{++} overload debugging info
20762 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20763 info. This includes info such as ranking of functions, etc. The default
20765 @item show debug overload
20766 Displays the current state of displaying @value{GDBN} C@t{++} overload
20768 @cindex expression parser, debugging info
20769 @cindex debug expression parser
20770 @item set debug parser
20771 Turns on or off the display of expression parser debugging output.
20772 Internally, this sets the @code{yydebug} variable in the expression
20773 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20774 details. The default is off.
20775 @item show debug parser
20776 Show the current state of expression parser debugging.
20777 @cindex packets, reporting on stdout
20778 @cindex serial connections, debugging
20779 @cindex debug remote protocol
20780 @cindex remote protocol debugging
20781 @cindex display remote packets
20782 @item set debug remote
20783 Turns on or off display of reports on all packets sent back and forth across
20784 the serial line to the remote machine. The info is printed on the
20785 @value{GDBN} standard output stream. The default is off.
20786 @item show debug remote
20787 Displays the state of display of remote packets.
20788 @item set debug serial
20789 Turns on or off display of @value{GDBN} serial debugging info. The
20791 @item show debug serial
20792 Displays the current state of displaying @value{GDBN} serial debugging
20794 @item set debug solib-frv
20795 @cindex FR-V shared-library debugging
20796 Turns on or off debugging messages for FR-V shared-library code.
20797 @item show debug solib-frv
20798 Display the current state of FR-V shared-library code debugging
20800 @item set debug target
20801 @cindex target debugging info
20802 Turns on or off display of @value{GDBN} target debugging info. This info
20803 includes what is going on at the target level of GDB, as it happens. The
20804 default is 0. Set it to 1 to track events, and to 2 to also track the
20805 value of large memory transfers. Changes to this flag do not take effect
20806 until the next time you connect to a target or use the @code{run} command.
20807 @item show debug target
20808 Displays the current state of displaying @value{GDBN} target debugging
20810 @item set debug timestamp
20811 @cindex timestampping debugging info
20812 Turns on or off display of timestamps with @value{GDBN} debugging info.
20813 When enabled, seconds and microseconds are displayed before each debugging
20815 @item show debug timestamp
20816 Displays the current state of displaying timestamps with @value{GDBN}
20818 @item set debugvarobj
20819 @cindex variable object debugging info
20820 Turns on or off display of @value{GDBN} variable object debugging
20821 info. The default is off.
20822 @item show debugvarobj
20823 Displays the current state of displaying @value{GDBN} variable object
20825 @item set debug xml
20826 @cindex XML parser debugging
20827 Turns on or off debugging messages for built-in XML parsers.
20828 @item show debug xml
20829 Displays the current state of XML debugging messages.
20832 @node Other Misc Settings
20833 @section Other Miscellaneous Settings
20834 @cindex miscellaneous settings
20837 @kindex set interactive-mode
20838 @item set interactive-mode
20839 If @code{on}, forces @value{GDBN} to assume that GDB was started
20840 in a terminal. In practice, this means that @value{GDBN} should wait
20841 for the user to answer queries generated by commands entered at
20842 the command prompt. If @code{off}, forces @value{GDBN} to operate
20843 in the opposite mode, and it uses the default answers to all queries.
20844 If @code{auto} (the default), @value{GDBN} tries to determine whether
20845 its standard input is a terminal, and works in interactive-mode if it
20846 is, non-interactively otherwise.
20848 In the vast majority of cases, the debugger should be able to guess
20849 correctly which mode should be used. But this setting can be useful
20850 in certain specific cases, such as running a MinGW @value{GDBN}
20851 inside a cygwin window.
20853 @kindex show interactive-mode
20854 @item show interactive-mode
20855 Displays whether the debugger is operating in interactive mode or not.
20858 @node Extending GDB
20859 @chapter Extending @value{GDBN}
20860 @cindex extending GDB
20862 @value{GDBN} provides three mechanisms for extension. The first is based
20863 on composition of @value{GDBN} commands, the second is based on the
20864 Python scripting language, and the third is for defining new aliases of
20867 To facilitate the use of the first two extensions, @value{GDBN} is capable
20868 of evaluating the contents of a file. When doing so, @value{GDBN}
20869 can recognize which scripting language is being used by looking at
20870 the filename extension. Files with an unrecognized filename extension
20871 are always treated as a @value{GDBN} Command Files.
20872 @xref{Command Files,, Command files}.
20874 You can control how @value{GDBN} evaluates these files with the following
20878 @kindex set script-extension
20879 @kindex show script-extension
20880 @item set script-extension off
20881 All scripts are always evaluated as @value{GDBN} Command Files.
20883 @item set script-extension soft
20884 The debugger determines the scripting language based on filename
20885 extension. If this scripting language is supported, @value{GDBN}
20886 evaluates the script using that language. Otherwise, it evaluates
20887 the file as a @value{GDBN} Command File.
20889 @item set script-extension strict
20890 The debugger determines the scripting language based on filename
20891 extension, and evaluates the script using that language. If the
20892 language is not supported, then the evaluation fails.
20894 @item show script-extension
20895 Display the current value of the @code{script-extension} option.
20900 * Sequences:: Canned Sequences of Commands
20901 * Python:: Scripting @value{GDBN} using Python
20902 * Aliases:: Creating new spellings of existing commands
20906 @section Canned Sequences of Commands
20908 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20909 Command Lists}), @value{GDBN} provides two ways to store sequences of
20910 commands for execution as a unit: user-defined commands and command
20914 * Define:: How to define your own commands
20915 * Hooks:: Hooks for user-defined commands
20916 * Command Files:: How to write scripts of commands to be stored in a file
20917 * Output:: Commands for controlled output
20921 @subsection User-defined Commands
20923 @cindex user-defined command
20924 @cindex arguments, to user-defined commands
20925 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20926 which you assign a new name as a command. This is done with the
20927 @code{define} command. User commands may accept up to 10 arguments
20928 separated by whitespace. Arguments are accessed within the user command
20929 via @code{$arg0@dots{}$arg9}. A trivial example:
20933 print $arg0 + $arg1 + $arg2
20938 To execute the command use:
20945 This defines the command @code{adder}, which prints the sum of
20946 its three arguments. Note the arguments are text substitutions, so they may
20947 reference variables, use complex expressions, or even perform inferior
20950 @cindex argument count in user-defined commands
20951 @cindex how many arguments (user-defined commands)
20952 In addition, @code{$argc} may be used to find out how many arguments have
20953 been passed. This expands to a number in the range 0@dots{}10.
20958 print $arg0 + $arg1
20961 print $arg0 + $arg1 + $arg2
20969 @item define @var{commandname}
20970 Define a command named @var{commandname}. If there is already a command
20971 by that name, you are asked to confirm that you want to redefine it.
20972 @var{commandname} may be a bare command name consisting of letters,
20973 numbers, dashes, and underscores. It may also start with any predefined
20974 prefix command. For example, @samp{define target my-target} creates
20975 a user-defined @samp{target my-target} command.
20977 The definition of the command is made up of other @value{GDBN} command lines,
20978 which are given following the @code{define} command. The end of these
20979 commands is marked by a line containing @code{end}.
20982 @kindex end@r{ (user-defined commands)}
20983 @item document @var{commandname}
20984 Document the user-defined command @var{commandname}, so that it can be
20985 accessed by @code{help}. The command @var{commandname} must already be
20986 defined. This command reads lines of documentation just as @code{define}
20987 reads the lines of the command definition, ending with @code{end}.
20988 After the @code{document} command is finished, @code{help} on command
20989 @var{commandname} displays the documentation you have written.
20991 You may use the @code{document} command again to change the
20992 documentation of a command. Redefining the command with @code{define}
20993 does not change the documentation.
20995 @kindex dont-repeat
20996 @cindex don't repeat command
20998 Used inside a user-defined command, this tells @value{GDBN} that this
20999 command should not be repeated when the user hits @key{RET}
21000 (@pxref{Command Syntax, repeat last command}).
21002 @kindex help user-defined
21003 @item help user-defined
21004 List all user-defined commands, with the first line of the documentation
21009 @itemx show user @var{commandname}
21010 Display the @value{GDBN} commands used to define @var{commandname} (but
21011 not its documentation). If no @var{commandname} is given, display the
21012 definitions for all user-defined commands.
21014 @cindex infinite recursion in user-defined commands
21015 @kindex show max-user-call-depth
21016 @kindex set max-user-call-depth
21017 @item show max-user-call-depth
21018 @itemx set max-user-call-depth
21019 The value of @code{max-user-call-depth} controls how many recursion
21020 levels are allowed in user-defined commands before @value{GDBN} suspects an
21021 infinite recursion and aborts the command.
21024 In addition to the above commands, user-defined commands frequently
21025 use control flow commands, described in @ref{Command Files}.
21027 When user-defined commands are executed, the
21028 commands of the definition are not printed. An error in any command
21029 stops execution of the user-defined command.
21031 If used interactively, commands that would ask for confirmation proceed
21032 without asking when used inside a user-defined command. Many @value{GDBN}
21033 commands that normally print messages to say what they are doing omit the
21034 messages when used in a user-defined command.
21037 @subsection User-defined Command Hooks
21038 @cindex command hooks
21039 @cindex hooks, for commands
21040 @cindex hooks, pre-command
21043 You may define @dfn{hooks}, which are a special kind of user-defined
21044 command. Whenever you run the command @samp{foo}, if the user-defined
21045 command @samp{hook-foo} exists, it is executed (with no arguments)
21046 before that command.
21048 @cindex hooks, post-command
21050 A hook may also be defined which is run after the command you executed.
21051 Whenever you run the command @samp{foo}, if the user-defined command
21052 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21053 that command. Post-execution hooks may exist simultaneously with
21054 pre-execution hooks, for the same command.
21056 It is valid for a hook to call the command which it hooks. If this
21057 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21059 @c It would be nice if hookpost could be passed a parameter indicating
21060 @c if the command it hooks executed properly or not. FIXME!
21062 @kindex stop@r{, a pseudo-command}
21063 In addition, a pseudo-command, @samp{stop} exists. Defining
21064 (@samp{hook-stop}) makes the associated commands execute every time
21065 execution stops in your program: before breakpoint commands are run,
21066 displays are printed, or the stack frame is printed.
21068 For example, to ignore @code{SIGALRM} signals while
21069 single-stepping, but treat them normally during normal execution,
21074 handle SIGALRM nopass
21078 handle SIGALRM pass
21081 define hook-continue
21082 handle SIGALRM pass
21086 As a further example, to hook at the beginning and end of the @code{echo}
21087 command, and to add extra text to the beginning and end of the message,
21095 define hookpost-echo
21099 (@value{GDBP}) echo Hello World
21100 <<<---Hello World--->>>
21105 You can define a hook for any single-word command in @value{GDBN}, but
21106 not for command aliases; you should define a hook for the basic command
21107 name, e.g.@: @code{backtrace} rather than @code{bt}.
21108 @c FIXME! So how does Joe User discover whether a command is an alias
21110 You can hook a multi-word command by adding @code{hook-} or
21111 @code{hookpost-} to the last word of the command, e.g.@:
21112 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21114 If an error occurs during the execution of your hook, execution of
21115 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21116 (before the command that you actually typed had a chance to run).
21118 If you try to define a hook which does not match any known command, you
21119 get a warning from the @code{define} command.
21121 @node Command Files
21122 @subsection Command Files
21124 @cindex command files
21125 @cindex scripting commands
21126 A command file for @value{GDBN} is a text file made of lines that are
21127 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21128 also be included. An empty line in a command file does nothing; it
21129 does not mean to repeat the last command, as it would from the
21132 You can request the execution of a command file with the @code{source}
21133 command. Note that the @code{source} command is also used to evaluate
21134 scripts that are not Command Files. The exact behavior can be configured
21135 using the @code{script-extension} setting.
21136 @xref{Extending GDB,, Extending GDB}.
21140 @cindex execute commands from a file
21141 @item source [-s] [-v] @var{filename}
21142 Execute the command file @var{filename}.
21145 The lines in a command file are generally executed sequentially,
21146 unless the order of execution is changed by one of the
21147 @emph{flow-control commands} described below. The commands are not
21148 printed as they are executed. An error in any command terminates
21149 execution of the command file and control is returned to the console.
21151 @value{GDBN} first searches for @var{filename} in the current directory.
21152 If the file is not found there, and @var{filename} does not specify a
21153 directory, then @value{GDBN} also looks for the file on the source search path
21154 (specified with the @samp{directory} command);
21155 except that @file{$cdir} is not searched because the compilation directory
21156 is not relevant to scripts.
21158 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21159 on the search path even if @var{filename} specifies a directory.
21160 The search is done by appending @var{filename} to each element of the
21161 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21162 and the search path contains @file{/home/user} then @value{GDBN} will
21163 look for the script @file{/home/user/mylib/myscript}.
21164 The search is also done if @var{filename} is an absolute path.
21165 For example, if @var{filename} is @file{/tmp/myscript} and
21166 the search path contains @file{/home/user} then @value{GDBN} will
21167 look for the script @file{/home/user/tmp/myscript}.
21168 For DOS-like systems, if @var{filename} contains a drive specification,
21169 it is stripped before concatenation. For example, if @var{filename} is
21170 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21171 will look for the script @file{c:/tmp/myscript}.
21173 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21174 each command as it is executed. The option must be given before
21175 @var{filename}, and is interpreted as part of the filename anywhere else.
21177 Commands that would ask for confirmation if used interactively proceed
21178 without asking when used in a command file. Many @value{GDBN} commands that
21179 normally print messages to say what they are doing omit the messages
21180 when called from command files.
21182 @value{GDBN} also accepts command input from standard input. In this
21183 mode, normal output goes to standard output and error output goes to
21184 standard error. Errors in a command file supplied on standard input do
21185 not terminate execution of the command file---execution continues with
21189 gdb < cmds > log 2>&1
21192 (The syntax above will vary depending on the shell used.) This example
21193 will execute commands from the file @file{cmds}. All output and errors
21194 would be directed to @file{log}.
21196 Since commands stored on command files tend to be more general than
21197 commands typed interactively, they frequently need to deal with
21198 complicated situations, such as different or unexpected values of
21199 variables and symbols, changes in how the program being debugged is
21200 built, etc. @value{GDBN} provides a set of flow-control commands to
21201 deal with these complexities. Using these commands, you can write
21202 complex scripts that loop over data structures, execute commands
21203 conditionally, etc.
21210 This command allows to include in your script conditionally executed
21211 commands. The @code{if} command takes a single argument, which is an
21212 expression to evaluate. It is followed by a series of commands that
21213 are executed only if the expression is true (its value is nonzero).
21214 There can then optionally be an @code{else} line, followed by a series
21215 of commands that are only executed if the expression was false. The
21216 end of the list is marked by a line containing @code{end}.
21220 This command allows to write loops. Its syntax is similar to
21221 @code{if}: the command takes a single argument, which is an expression
21222 to evaluate, and must be followed by the commands to execute, one per
21223 line, terminated by an @code{end}. These commands are called the
21224 @dfn{body} of the loop. The commands in the body of @code{while} are
21225 executed repeatedly as long as the expression evaluates to true.
21229 This command exits the @code{while} loop in whose body it is included.
21230 Execution of the script continues after that @code{while}s @code{end}
21233 @kindex loop_continue
21234 @item loop_continue
21235 This command skips the execution of the rest of the body of commands
21236 in the @code{while} loop in whose body it is included. Execution
21237 branches to the beginning of the @code{while} loop, where it evaluates
21238 the controlling expression.
21240 @kindex end@r{ (if/else/while commands)}
21242 Terminate the block of commands that are the body of @code{if},
21243 @code{else}, or @code{while} flow-control commands.
21248 @subsection Commands for Controlled Output
21250 During the execution of a command file or a user-defined command, normal
21251 @value{GDBN} output is suppressed; the only output that appears is what is
21252 explicitly printed by the commands in the definition. This section
21253 describes three commands useful for generating exactly the output you
21258 @item echo @var{text}
21259 @c I do not consider backslash-space a standard C escape sequence
21260 @c because it is not in ANSI.
21261 Print @var{text}. Nonprinting characters can be included in
21262 @var{text} using C escape sequences, such as @samp{\n} to print a
21263 newline. @strong{No newline is printed unless you specify one.}
21264 In addition to the standard C escape sequences, a backslash followed
21265 by a space stands for a space. This is useful for displaying a
21266 string with spaces at the beginning or the end, since leading and
21267 trailing spaces are otherwise trimmed from all arguments.
21268 To print @samp{@w{ }and foo =@w{ }}, use the command
21269 @samp{echo \@w{ }and foo = \@w{ }}.
21271 A backslash at the end of @var{text} can be used, as in C, to continue
21272 the command onto subsequent lines. For example,
21275 echo This is some text\n\
21276 which is continued\n\
21277 onto several lines.\n
21280 produces the same output as
21283 echo This is some text\n
21284 echo which is continued\n
21285 echo onto several lines.\n
21289 @item output @var{expression}
21290 Print the value of @var{expression} and nothing but that value: no
21291 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21292 value history either. @xref{Expressions, ,Expressions}, for more information
21295 @item output/@var{fmt} @var{expression}
21296 Print the value of @var{expression} in format @var{fmt}. You can use
21297 the same formats as for @code{print}. @xref{Output Formats,,Output
21298 Formats}, for more information.
21301 @item printf @var{template}, @var{expressions}@dots{}
21302 Print the values of one or more @var{expressions} under the control of
21303 the string @var{template}. To print several values, make
21304 @var{expressions} be a comma-separated list of individual expressions,
21305 which may be either numbers or pointers. Their values are printed as
21306 specified by @var{template}, exactly as a C program would do by
21307 executing the code below:
21310 printf (@var{template}, @var{expressions}@dots{});
21313 As in @code{C} @code{printf}, ordinary characters in @var{template}
21314 are printed verbatim, while @dfn{conversion specification} introduced
21315 by the @samp{%} character cause subsequent @var{expressions} to be
21316 evaluated, their values converted and formatted according to type and
21317 style information encoded in the conversion specifications, and then
21320 For example, you can print two values in hex like this:
21323 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21326 @code{printf} supports all the standard @code{C} conversion
21327 specifications, including the flags and modifiers between the @samp{%}
21328 character and the conversion letter, with the following exceptions:
21332 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21335 The modifier @samp{*} is not supported for specifying precision or
21339 The @samp{'} flag (for separation of digits into groups according to
21340 @code{LC_NUMERIC'}) is not supported.
21343 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21347 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21350 The conversion letters @samp{a} and @samp{A} are not supported.
21354 Note that the @samp{ll} type modifier is supported only if the
21355 underlying @code{C} implementation used to build @value{GDBN} supports
21356 the @code{long long int} type, and the @samp{L} type modifier is
21357 supported only if @code{long double} type is available.
21359 As in @code{C}, @code{printf} supports simple backslash-escape
21360 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21361 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21362 single character. Octal and hexadecimal escape sequences are not
21365 Additionally, @code{printf} supports conversion specifications for DFP
21366 (@dfn{Decimal Floating Point}) types using the following length modifiers
21367 together with a floating point specifier.
21372 @samp{H} for printing @code{Decimal32} types.
21375 @samp{D} for printing @code{Decimal64} types.
21378 @samp{DD} for printing @code{Decimal128} types.
21381 If the underlying @code{C} implementation used to build @value{GDBN} has
21382 support for the three length modifiers for DFP types, other modifiers
21383 such as width and precision will also be available for @value{GDBN} to use.
21385 In case there is no such @code{C} support, no additional modifiers will be
21386 available and the value will be printed in the standard way.
21388 Here's an example of printing DFP types using the above conversion letters:
21390 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21394 @item eval @var{template}, @var{expressions}@dots{}
21395 Convert the values of one or more @var{expressions} under the control of
21396 the string @var{template} to a command line, and call it.
21401 @section Scripting @value{GDBN} using Python
21402 @cindex python scripting
21403 @cindex scripting with python
21405 You can script @value{GDBN} using the @uref{http://www.python.org/,
21406 Python programming language}. This feature is available only if
21407 @value{GDBN} was configured using @option{--with-python}.
21409 @cindex python directory
21410 Python scripts used by @value{GDBN} should be installed in
21411 @file{@var{data-directory}/python}, where @var{data-directory} is
21412 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21413 This directory, known as the @dfn{python directory},
21414 is automatically added to the Python Search Path in order to allow
21415 the Python interpreter to locate all scripts installed at this location.
21417 Additionally, @value{GDBN} commands and convenience functions which
21418 are written in Python and are located in the
21419 @file{@var{data-directory}/python/gdb/command} or
21420 @file{@var{data-directory}/python/gdb/function} directories are
21421 automatically imported when @value{GDBN} starts.
21424 * Python Commands:: Accessing Python from @value{GDBN}.
21425 * Python API:: Accessing @value{GDBN} from Python.
21426 * Auto-loading:: Automatically loading Python code.
21427 * Python modules:: Python modules provided by @value{GDBN}.
21430 @node Python Commands
21431 @subsection Python Commands
21432 @cindex python commands
21433 @cindex commands to access python
21435 @value{GDBN} provides one command for accessing the Python interpreter,
21436 and one related setting:
21440 @item python @r{[}@var{code}@r{]}
21441 The @code{python} command can be used to evaluate Python code.
21443 If given an argument, the @code{python} command will evaluate the
21444 argument as a Python command. For example:
21447 (@value{GDBP}) python print 23
21451 If you do not provide an argument to @code{python}, it will act as a
21452 multi-line command, like @code{define}. In this case, the Python
21453 script is made up of subsequent command lines, given after the
21454 @code{python} command. This command list is terminated using a line
21455 containing @code{end}. For example:
21458 (@value{GDBP}) python
21460 End with a line saying just "end".
21466 @kindex set python print-stack
21467 @item set python print-stack
21468 By default, @value{GDBN} will print only the message component of a
21469 Python exception when an error occurs in a Python script. This can be
21470 controlled using @code{set python print-stack}: if @code{full}, then
21471 full Python stack printing is enabled; if @code{none}, then Python stack
21472 and message printing is disabled; if @code{message}, the default, only
21473 the message component of the error is printed.
21476 It is also possible to execute a Python script from the @value{GDBN}
21480 @item source @file{script-name}
21481 The script name must end with @samp{.py} and @value{GDBN} must be configured
21482 to recognize the script language based on filename extension using
21483 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21485 @item python execfile ("script-name")
21486 This method is based on the @code{execfile} Python built-in function,
21487 and thus is always available.
21491 @subsection Python API
21493 @cindex programming in python
21495 @cindex python stdout
21496 @cindex python pagination
21497 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21498 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21499 A Python program which outputs to one of these streams may have its
21500 output interrupted by the user (@pxref{Screen Size}). In this
21501 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21504 * Basic Python:: Basic Python Functions.
21505 * Exception Handling:: How Python exceptions are translated.
21506 * Values From Inferior:: Python representation of values.
21507 * Types In Python:: Python representation of types.
21508 * Pretty Printing API:: Pretty-printing values.
21509 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21510 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21511 * Inferiors In Python:: Python representation of inferiors (processes)
21512 * Events In Python:: Listening for events from @value{GDBN}.
21513 * Threads In Python:: Accessing inferior threads from Python.
21514 * Commands In Python:: Implementing new commands in Python.
21515 * Parameters In Python:: Adding new @value{GDBN} parameters.
21516 * Functions In Python:: Writing new convenience functions.
21517 * Progspaces In Python:: Program spaces.
21518 * Objfiles In Python:: Object files.
21519 * Frames In Python:: Accessing inferior stack frames from Python.
21520 * Blocks In Python:: Accessing frame blocks from Python.
21521 * Symbols In Python:: Python representation of symbols.
21522 * Symbol Tables In Python:: Python representation of symbol tables.
21523 * Lazy Strings In Python:: Python representation of lazy strings.
21524 * Breakpoints In Python:: Manipulating breakpoints using Python.
21525 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21530 @subsubsection Basic Python
21532 @cindex python functions
21533 @cindex python module
21535 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21536 methods and classes added by @value{GDBN} are placed in this module.
21537 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21538 use in all scripts evaluated by the @code{python} command.
21540 @findex gdb.PYTHONDIR
21541 @defvar gdb.PYTHONDIR
21542 A string containing the python directory (@pxref{Python}).
21545 @findex gdb.execute
21546 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21547 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21548 If a GDB exception happens while @var{command} runs, it is
21549 translated as described in @ref{Exception Handling,,Exception Handling}.
21551 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21552 command as having originated from the user invoking it interactively.
21553 It must be a boolean value. If omitted, it defaults to @code{False}.
21555 By default, any output produced by @var{command} is sent to
21556 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21557 @code{True}, then output will be collected by @code{gdb.execute} and
21558 returned as a string. The default is @code{False}, in which case the
21559 return value is @code{None}. If @var{to_string} is @code{True}, the
21560 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21561 and height, and its pagination will be disabled; @pxref{Screen Size}.
21564 @findex gdb.breakpoints
21565 @defun gdb.breakpoints ()
21566 Return a sequence holding all of @value{GDBN}'s breakpoints.
21567 @xref{Breakpoints In Python}, for more information.
21570 @findex gdb.parameter
21571 @defun gdb.parameter (parameter)
21572 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21573 string naming the parameter to look up; @var{parameter} may contain
21574 spaces if the parameter has a multi-part name. For example,
21575 @samp{print object} is a valid parameter name.
21577 If the named parameter does not exist, this function throws a
21578 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21579 parameter's value is converted to a Python value of the appropriate
21580 type, and returned.
21583 @findex gdb.history
21584 @defun gdb.history (number)
21585 Return a value from @value{GDBN}'s value history (@pxref{Value
21586 History}). @var{number} indicates which history element to return.
21587 If @var{number} is negative, then @value{GDBN} will take its absolute value
21588 and count backward from the last element (i.e., the most recent element) to
21589 find the value to return. If @var{number} is zero, then @value{GDBN} will
21590 return the most recent element. If the element specified by @var{number}
21591 doesn't exist in the value history, a @code{gdb.error} exception will be
21594 If no exception is raised, the return value is always an instance of
21595 @code{gdb.Value} (@pxref{Values From Inferior}).
21598 @findex gdb.parse_and_eval
21599 @defun gdb.parse_and_eval (expression)
21600 Parse @var{expression} as an expression in the current language,
21601 evaluate it, and return the result as a @code{gdb.Value}.
21602 @var{expression} must be a string.
21604 This function can be useful when implementing a new command
21605 (@pxref{Commands In Python}), as it provides a way to parse the
21606 command's argument as an expression. It is also useful simply to
21607 compute values, for example, it is the only way to get the value of a
21608 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21611 @findex gdb.post_event
21612 @defun gdb.post_event (event)
21613 Put @var{event}, a callable object taking no arguments, into
21614 @value{GDBN}'s internal event queue. This callable will be invoked at
21615 some later point, during @value{GDBN}'s event processing. Events
21616 posted using @code{post_event} will be run in the order in which they
21617 were posted; however, there is no way to know when they will be
21618 processed relative to other events inside @value{GDBN}.
21620 @value{GDBN} is not thread-safe. If your Python program uses multiple
21621 threads, you must be careful to only call @value{GDBN}-specific
21622 functions in the main @value{GDBN} thread. @code{post_event} ensures
21626 (@value{GDBP}) python
21630 > def __init__(self, message):
21631 > self.message = message;
21632 > def __call__(self):
21633 > gdb.write(self.message)
21635 >class MyThread1 (threading.Thread):
21637 > gdb.post_event(Writer("Hello "))
21639 >class MyThread2 (threading.Thread):
21641 > gdb.post_event(Writer("World\n"))
21643 >MyThread1().start()
21644 >MyThread2().start()
21646 (@value{GDBP}) Hello World
21651 @defun gdb.write (string @r{[}, stream{]})
21652 Print a string to @value{GDBN}'s paginated output stream. The
21653 optional @var{stream} determines the stream to print to. The default
21654 stream is @value{GDBN}'s standard output stream. Possible stream
21661 @value{GDBN}'s standard output stream.
21666 @value{GDBN}'s standard error stream.
21671 @value{GDBN}'s log stream (@pxref{Logging Output}).
21674 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21675 call this function and will automatically direct the output to the
21680 @defun gdb.flush ()
21681 Flush the buffer of a @value{GDBN} paginated stream so that the
21682 contents are displayed immediately. @value{GDBN} will flush the
21683 contents of a stream automatically when it encounters a newline in the
21684 buffer. The optional @var{stream} determines the stream to flush. The
21685 default stream is @value{GDBN}'s standard output stream. Possible
21692 @value{GDBN}'s standard output stream.
21697 @value{GDBN}'s standard error stream.
21702 @value{GDBN}'s log stream (@pxref{Logging Output}).
21706 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21707 call this function for the relevant stream.
21710 @findex gdb.target_charset
21711 @defun gdb.target_charset ()
21712 Return the name of the current target character set (@pxref{Character
21713 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21714 that @samp{auto} is never returned.
21717 @findex gdb.target_wide_charset
21718 @defun gdb.target_wide_charset ()
21719 Return the name of the current target wide character set
21720 (@pxref{Character Sets}). This differs from
21721 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21725 @findex gdb.solib_name
21726 @defun gdb.solib_name (address)
21727 Return the name of the shared library holding the given @var{address}
21728 as a string, or @code{None}.
21731 @findex gdb.decode_line
21732 @defun gdb.decode_line @r{[}expression@r{]}
21733 Return locations of the line specified by @var{expression}, or of the
21734 current line if no argument was given. This function returns a Python
21735 tuple containing two elements. The first element contains a string
21736 holding any unparsed section of @var{expression} (or @code{None} if
21737 the expression has been fully parsed). The second element contains
21738 either @code{None} or another tuple that contains all the locations
21739 that match the expression represented as @code{gdb.Symtab_and_line}
21740 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21741 provided, it is decoded the way that @value{GDBN}'s inbuilt
21742 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21745 @defun gdb.prompt_hook (current_prompt)
21746 @anchor{prompt_hook}
21748 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21749 assigned to this operation before a prompt is displayed by
21752 The parameter @code{current_prompt} contains the current @value{GDBN}
21753 prompt. This method must return a Python string, or @code{None}. If
21754 a string is returned, the @value{GDBN} prompt will be set to that
21755 string. If @code{None} is returned, @value{GDBN} will continue to use
21756 the current prompt.
21758 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21759 such as those used by readline for command input, and annotation
21760 related prompts are prohibited from being changed.
21763 @node Exception Handling
21764 @subsubsection Exception Handling
21765 @cindex python exceptions
21766 @cindex exceptions, python
21768 When executing the @code{python} command, Python exceptions
21769 uncaught within the Python code are translated to calls to
21770 @value{GDBN} error-reporting mechanism. If the command that called
21771 @code{python} does not handle the error, @value{GDBN} will
21772 terminate it and print an error message containing the Python
21773 exception name, the associated value, and the Python call stack
21774 backtrace at the point where the exception was raised. Example:
21777 (@value{GDBP}) python print foo
21778 Traceback (most recent call last):
21779 File "<string>", line 1, in <module>
21780 NameError: name 'foo' is not defined
21783 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21784 Python code are converted to Python exceptions. The type of the
21785 Python exception depends on the error.
21789 This is the base class for most exceptions generated by @value{GDBN}.
21790 It is derived from @code{RuntimeError}, for compatibility with earlier
21791 versions of @value{GDBN}.
21793 If an error occurring in @value{GDBN} does not fit into some more
21794 specific category, then the generated exception will have this type.
21796 @item gdb.MemoryError
21797 This is a subclass of @code{gdb.error} which is thrown when an
21798 operation tried to access invalid memory in the inferior.
21800 @item KeyboardInterrupt
21801 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21802 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21805 In all cases, your exception handler will see the @value{GDBN} error
21806 message as its value and the Python call stack backtrace at the Python
21807 statement closest to where the @value{GDBN} error occured as the
21810 @findex gdb.GdbError
21811 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21812 it is useful to be able to throw an exception that doesn't cause a
21813 traceback to be printed. For example, the user may have invoked the
21814 command incorrectly. Use the @code{gdb.GdbError} exception
21815 to handle this case. Example:
21819 >class HelloWorld (gdb.Command):
21820 > """Greet the whole world."""
21821 > def __init__ (self):
21822 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21823 > def invoke (self, args, from_tty):
21824 > argv = gdb.string_to_argv (args)
21825 > if len (argv) != 0:
21826 > raise gdb.GdbError ("hello-world takes no arguments")
21827 > print "Hello, World!"
21830 (gdb) hello-world 42
21831 hello-world takes no arguments
21834 @node Values From Inferior
21835 @subsubsection Values From Inferior
21836 @cindex values from inferior, with Python
21837 @cindex python, working with values from inferior
21839 @cindex @code{gdb.Value}
21840 @value{GDBN} provides values it obtains from the inferior program in
21841 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21842 for its internal bookkeeping of the inferior's values, and for
21843 fetching values when necessary.
21845 Inferior values that are simple scalars can be used directly in
21846 Python expressions that are valid for the value's data type. Here's
21847 an example for an integer or floating-point value @code{some_val}:
21854 As result of this, @code{bar} will also be a @code{gdb.Value} object
21855 whose values are of the same type as those of @code{some_val}.
21857 Inferior values that are structures or instances of some class can
21858 be accessed using the Python @dfn{dictionary syntax}. For example, if
21859 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21860 can access its @code{foo} element with:
21863 bar = some_val['foo']
21866 Again, @code{bar} will also be a @code{gdb.Value} object.
21868 A @code{gdb.Value} that represents a function can be executed via
21869 inferior function call. Any arguments provided to the call must match
21870 the function's prototype, and must be provided in the order specified
21873 For example, @code{some_val} is a @code{gdb.Value} instance
21874 representing a function that takes two integers as arguments. To
21875 execute this function, call it like so:
21878 result = some_val (10,20)
21881 Any values returned from a function call will be stored as a
21884 The following attributes are provided:
21887 @defvar Value.address
21888 If this object is addressable, this read-only attribute holds a
21889 @code{gdb.Value} object representing the address. Otherwise,
21890 this attribute holds @code{None}.
21893 @cindex optimized out value in Python
21894 @defvar Value.is_optimized_out
21895 This read-only boolean attribute is true if the compiler optimized out
21896 this value, thus it is not available for fetching from the inferior.
21900 The type of this @code{gdb.Value}. The value of this attribute is a
21901 @code{gdb.Type} object (@pxref{Types In Python}).
21904 @defvar Value.dynamic_type
21905 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21906 type information (@acronym{RTTI}) to determine the dynamic type of the
21907 value. If this value is of class type, it will return the class in
21908 which the value is embedded, if any. If this value is of pointer or
21909 reference to a class type, it will compute the dynamic type of the
21910 referenced object, and return a pointer or reference to that type,
21911 respectively. In all other cases, it will return the value's static
21914 Note that this feature will only work when debugging a C@t{++} program
21915 that includes @acronym{RTTI} for the object in question. Otherwise,
21916 it will just return the static type of the value as in @kbd{ptype foo}
21917 (@pxref{Symbols, ptype}).
21920 @defvar Value.is_lazy
21921 The value of this read-only boolean attribute is @code{True} if this
21922 @code{gdb.Value} has not yet been fetched from the inferior.
21923 @value{GDBN} does not fetch values until necessary, for efficiency.
21927 myval = gdb.parse_and_eval ('somevar')
21930 The value of @code{somevar} is not fetched at this time. It will be
21931 fetched when the value is needed, or when the @code{fetch_lazy}
21936 The following methods are provided:
21939 @defun Value.__init__ (@var{val})
21940 Many Python values can be converted directly to a @code{gdb.Value} via
21941 this object initializer. Specifically:
21944 @item Python boolean
21945 A Python boolean is converted to the boolean type from the current
21948 @item Python integer
21949 A Python integer is converted to the C @code{long} type for the
21950 current architecture.
21953 A Python long is converted to the C @code{long long} type for the
21954 current architecture.
21957 A Python float is converted to the C @code{double} type for the
21958 current architecture.
21960 @item Python string
21961 A Python string is converted to a target string, using the current
21964 @item @code{gdb.Value}
21965 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21967 @item @code{gdb.LazyString}
21968 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21969 Python}), then the lazy string's @code{value} method is called, and
21970 its result is used.
21974 @defun Value.cast (type)
21975 Return a new instance of @code{gdb.Value} that is the result of
21976 casting this instance to the type described by @var{type}, which must
21977 be a @code{gdb.Type} object. If the cast cannot be performed for some
21978 reason, this method throws an exception.
21981 @defun Value.dereference ()
21982 For pointer data types, this method returns a new @code{gdb.Value} object
21983 whose contents is the object pointed to by the pointer. For example, if
21984 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21991 then you can use the corresponding @code{gdb.Value} to access what
21992 @code{foo} points to like this:
21995 bar = foo.dereference ()
21998 The result @code{bar} will be a @code{gdb.Value} object holding the
21999 value pointed to by @code{foo}.
22002 @defun Value.dynamic_cast (type)
22003 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22004 operator were used. Consult a C@t{++} reference for details.
22007 @defun Value.reinterpret_cast (type)
22008 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22009 operator were used. Consult a C@t{++} reference for details.
22012 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22013 If this @code{gdb.Value} represents a string, then this method
22014 converts the contents to a Python string. Otherwise, this method will
22015 throw an exception.
22017 Strings are recognized in a language-specific way; whether a given
22018 @code{gdb.Value} represents a string is determined by the current
22021 For C-like languages, a value is a string if it is a pointer to or an
22022 array of characters or ints. The string is assumed to be terminated
22023 by a zero of the appropriate width. However if the optional length
22024 argument is given, the string will be converted to that given length,
22025 ignoring any embedded zeros that the string may contain.
22027 If the optional @var{encoding} argument is given, it must be a string
22028 naming the encoding of the string in the @code{gdb.Value}, such as
22029 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22030 the same encodings as the corresponding argument to Python's
22031 @code{string.decode} method, and the Python codec machinery will be used
22032 to convert the string. If @var{encoding} is not given, or if
22033 @var{encoding} is the empty string, then either the @code{target-charset}
22034 (@pxref{Character Sets}) will be used, or a language-specific encoding
22035 will be used, if the current language is able to supply one.
22037 The optional @var{errors} argument is the same as the corresponding
22038 argument to Python's @code{string.decode} method.
22040 If the optional @var{length} argument is given, the string will be
22041 fetched and converted to the given length.
22044 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22045 If this @code{gdb.Value} represents a string, then this method
22046 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22047 In Python}). Otherwise, this method will throw an exception.
22049 If the optional @var{encoding} argument is given, it must be a string
22050 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22051 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22052 @var{encoding} argument is an encoding that @value{GDBN} does
22053 recognize, @value{GDBN} will raise an error.
22055 When a lazy string is printed, the @value{GDBN} encoding machinery is
22056 used to convert the string during printing. If the optional
22057 @var{encoding} argument is not provided, or is an empty string,
22058 @value{GDBN} will automatically select the encoding most suitable for
22059 the string type. For further information on encoding in @value{GDBN}
22060 please see @ref{Character Sets}.
22062 If the optional @var{length} argument is given, the string will be
22063 fetched and encoded to the length of characters specified. If
22064 the @var{length} argument is not provided, the string will be fetched
22065 and encoded until a null of appropriate width is found.
22068 @defun Value.fetch_lazy ()
22069 If the @code{gdb.Value} object is currently a lazy value
22070 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22071 fetched from the inferior. Any errors that occur in the process
22072 will produce a Python exception.
22074 If the @code{gdb.Value} object is not a lazy value, this method
22077 This method does not return a value.
22082 @node Types In Python
22083 @subsubsection Types In Python
22084 @cindex types in Python
22085 @cindex Python, working with types
22088 @value{GDBN} represents types from the inferior using the class
22091 The following type-related functions are available in the @code{gdb}
22094 @findex gdb.lookup_type
22095 @defun gdb.lookup_type (name @r{[}, block@r{]})
22096 This function looks up a type by name. @var{name} is the name of the
22097 type to look up. It must be a string.
22099 If @var{block} is given, then @var{name} is looked up in that scope.
22100 Otherwise, it is searched for globally.
22102 Ordinarily, this function will return an instance of @code{gdb.Type}.
22103 If the named type cannot be found, it will throw an exception.
22106 If the type is a structure or class type, or an enum type, the fields
22107 of that type can be accessed using the Python @dfn{dictionary syntax}.
22108 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22109 a structure type, you can access its @code{foo} field with:
22112 bar = some_type['foo']
22115 @code{bar} will be a @code{gdb.Field} object; see below under the
22116 description of the @code{Type.fields} method for a description of the
22117 @code{gdb.Field} class.
22119 An instance of @code{Type} has the following attributes:
22123 The type code for this type. The type code will be one of the
22124 @code{TYPE_CODE_} constants defined below.
22127 @defvar Type.sizeof
22128 The size of this type, in target @code{char} units. Usually, a
22129 target's @code{char} type will be an 8-bit byte. However, on some
22130 unusual platforms, this type may have a different size.
22134 The tag name for this type. The tag name is the name after
22135 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22136 languages have this concept. If this type has no tag name, then
22137 @code{None} is returned.
22141 The following methods are provided:
22144 @defun Type.fields ()
22145 For structure and union types, this method returns the fields. Range
22146 types have two fields, the minimum and maximum values. Enum types
22147 have one field per enum constant. Function and method types have one
22148 field per parameter. The base types of C@t{++} classes are also
22149 represented as fields. If the type has no fields, or does not fit
22150 into one of these categories, an empty sequence will be returned.
22152 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22155 This attribute is not available for @code{static} fields (as in
22156 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22157 position of the field. For @code{enum} fields, the value is the
22158 enumeration member's integer representation.
22161 The name of the field, or @code{None} for anonymous fields.
22164 This is @code{True} if the field is artificial, usually meaning that
22165 it was provided by the compiler and not the user. This attribute is
22166 always provided, and is @code{False} if the field is not artificial.
22168 @item is_base_class
22169 This is @code{True} if the field represents a base class of a C@t{++}
22170 structure. This attribute is always provided, and is @code{False}
22171 if the field is not a base class of the type that is the argument of
22172 @code{fields}, or if that type was not a C@t{++} class.
22175 If the field is packed, or is a bitfield, then this will have a
22176 non-zero value, which is the size of the field in bits. Otherwise,
22177 this will be zero; in this case the field's size is given by its type.
22180 The type of the field. This is usually an instance of @code{Type},
22181 but it can be @code{None} in some situations.
22185 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22186 Return a new @code{gdb.Type} object which represents an array of this
22187 type. If one argument is given, it is the inclusive upper bound of
22188 the array; in this case the lower bound is zero. If two arguments are
22189 given, the first argument is the lower bound of the array, and the
22190 second argument is the upper bound of the array. An array's length
22191 must not be negative, but the bounds can be.
22194 @defun Type.const ()
22195 Return a new @code{gdb.Type} object which represents a
22196 @code{const}-qualified variant of this type.
22199 @defun Type.volatile ()
22200 Return a new @code{gdb.Type} object which represents a
22201 @code{volatile}-qualified variant of this type.
22204 @defun Type.unqualified ()
22205 Return a new @code{gdb.Type} object which represents an unqualified
22206 variant of this type. That is, the result is neither @code{const} nor
22210 @defun Type.range ()
22211 Return a Python @code{Tuple} object that contains two elements: the
22212 low bound of the argument type and the high bound of that type. If
22213 the type does not have a range, @value{GDBN} will raise a
22214 @code{gdb.error} exception (@pxref{Exception Handling}).
22217 @defun Type.reference ()
22218 Return a new @code{gdb.Type} object which represents a reference to this
22222 @defun Type.pointer ()
22223 Return a new @code{gdb.Type} object which represents a pointer to this
22227 @defun Type.strip_typedefs ()
22228 Return a new @code{gdb.Type} that represents the real type,
22229 after removing all layers of typedefs.
22232 @defun Type.target ()
22233 Return a new @code{gdb.Type} object which represents the target type
22236 For a pointer type, the target type is the type of the pointed-to
22237 object. For an array type (meaning C-like arrays), the target type is
22238 the type of the elements of the array. For a function or method type,
22239 the target type is the type of the return value. For a complex type,
22240 the target type is the type of the elements. For a typedef, the
22241 target type is the aliased type.
22243 If the type does not have a target, this method will throw an
22247 @defun Type.template_argument (n @r{[}, block@r{]})
22248 If this @code{gdb.Type} is an instantiation of a template, this will
22249 return a new @code{gdb.Type} which represents the type of the
22250 @var{n}th template argument.
22252 If this @code{gdb.Type} is not a template type, this will throw an
22253 exception. Ordinarily, only C@t{++} code will have template types.
22255 If @var{block} is given, then @var{name} is looked up in that scope.
22256 Otherwise, it is searched for globally.
22261 Each type has a code, which indicates what category this type falls
22262 into. The available type categories are represented by constants
22263 defined in the @code{gdb} module:
22266 @findex TYPE_CODE_PTR
22267 @findex gdb.TYPE_CODE_PTR
22268 @item gdb.TYPE_CODE_PTR
22269 The type is a pointer.
22271 @findex TYPE_CODE_ARRAY
22272 @findex gdb.TYPE_CODE_ARRAY
22273 @item gdb.TYPE_CODE_ARRAY
22274 The type is an array.
22276 @findex TYPE_CODE_STRUCT
22277 @findex gdb.TYPE_CODE_STRUCT
22278 @item gdb.TYPE_CODE_STRUCT
22279 The type is a structure.
22281 @findex TYPE_CODE_UNION
22282 @findex gdb.TYPE_CODE_UNION
22283 @item gdb.TYPE_CODE_UNION
22284 The type is a union.
22286 @findex TYPE_CODE_ENUM
22287 @findex gdb.TYPE_CODE_ENUM
22288 @item gdb.TYPE_CODE_ENUM
22289 The type is an enum.
22291 @findex TYPE_CODE_FLAGS
22292 @findex gdb.TYPE_CODE_FLAGS
22293 @item gdb.TYPE_CODE_FLAGS
22294 A bit flags type, used for things such as status registers.
22296 @findex TYPE_CODE_FUNC
22297 @findex gdb.TYPE_CODE_FUNC
22298 @item gdb.TYPE_CODE_FUNC
22299 The type is a function.
22301 @findex TYPE_CODE_INT
22302 @findex gdb.TYPE_CODE_INT
22303 @item gdb.TYPE_CODE_INT
22304 The type is an integer type.
22306 @findex TYPE_CODE_FLT
22307 @findex gdb.TYPE_CODE_FLT
22308 @item gdb.TYPE_CODE_FLT
22309 A floating point type.
22311 @findex TYPE_CODE_VOID
22312 @findex gdb.TYPE_CODE_VOID
22313 @item gdb.TYPE_CODE_VOID
22314 The special type @code{void}.
22316 @findex TYPE_CODE_SET
22317 @findex gdb.TYPE_CODE_SET
22318 @item gdb.TYPE_CODE_SET
22321 @findex TYPE_CODE_RANGE
22322 @findex gdb.TYPE_CODE_RANGE
22323 @item gdb.TYPE_CODE_RANGE
22324 A range type, that is, an integer type with bounds.
22326 @findex TYPE_CODE_STRING
22327 @findex gdb.TYPE_CODE_STRING
22328 @item gdb.TYPE_CODE_STRING
22329 A string type. Note that this is only used for certain languages with
22330 language-defined string types; C strings are not represented this way.
22332 @findex TYPE_CODE_BITSTRING
22333 @findex gdb.TYPE_CODE_BITSTRING
22334 @item gdb.TYPE_CODE_BITSTRING
22337 @findex TYPE_CODE_ERROR
22338 @findex gdb.TYPE_CODE_ERROR
22339 @item gdb.TYPE_CODE_ERROR
22340 An unknown or erroneous type.
22342 @findex TYPE_CODE_METHOD
22343 @findex gdb.TYPE_CODE_METHOD
22344 @item gdb.TYPE_CODE_METHOD
22345 A method type, as found in C@t{++} or Java.
22347 @findex TYPE_CODE_METHODPTR
22348 @findex gdb.TYPE_CODE_METHODPTR
22349 @item gdb.TYPE_CODE_METHODPTR
22350 A pointer-to-member-function.
22352 @findex TYPE_CODE_MEMBERPTR
22353 @findex gdb.TYPE_CODE_MEMBERPTR
22354 @item gdb.TYPE_CODE_MEMBERPTR
22355 A pointer-to-member.
22357 @findex TYPE_CODE_REF
22358 @findex gdb.TYPE_CODE_REF
22359 @item gdb.TYPE_CODE_REF
22362 @findex TYPE_CODE_CHAR
22363 @findex gdb.TYPE_CODE_CHAR
22364 @item gdb.TYPE_CODE_CHAR
22367 @findex TYPE_CODE_BOOL
22368 @findex gdb.TYPE_CODE_BOOL
22369 @item gdb.TYPE_CODE_BOOL
22372 @findex TYPE_CODE_COMPLEX
22373 @findex gdb.TYPE_CODE_COMPLEX
22374 @item gdb.TYPE_CODE_COMPLEX
22375 A complex float type.
22377 @findex TYPE_CODE_TYPEDEF
22378 @findex gdb.TYPE_CODE_TYPEDEF
22379 @item gdb.TYPE_CODE_TYPEDEF
22380 A typedef to some other type.
22382 @findex TYPE_CODE_NAMESPACE
22383 @findex gdb.TYPE_CODE_NAMESPACE
22384 @item gdb.TYPE_CODE_NAMESPACE
22385 A C@t{++} namespace.
22387 @findex TYPE_CODE_DECFLOAT
22388 @findex gdb.TYPE_CODE_DECFLOAT
22389 @item gdb.TYPE_CODE_DECFLOAT
22390 A decimal floating point type.
22392 @findex TYPE_CODE_INTERNAL_FUNCTION
22393 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22394 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22395 A function internal to @value{GDBN}. This is the type used to represent
22396 convenience functions.
22399 Further support for types is provided in the @code{gdb.types}
22400 Python module (@pxref{gdb.types}).
22402 @node Pretty Printing API
22403 @subsubsection Pretty Printing API
22405 An example output is provided (@pxref{Pretty Printing}).
22407 A pretty-printer is just an object that holds a value and implements a
22408 specific interface, defined here.
22410 @defun pretty_printer.children (self)
22411 @value{GDBN} will call this method on a pretty-printer to compute the
22412 children of the pretty-printer's value.
22414 This method must return an object conforming to the Python iterator
22415 protocol. Each item returned by the iterator must be a tuple holding
22416 two elements. The first element is the ``name'' of the child; the
22417 second element is the child's value. The value can be any Python
22418 object which is convertible to a @value{GDBN} value.
22420 This method is optional. If it does not exist, @value{GDBN} will act
22421 as though the value has no children.
22424 @defun pretty_printer.display_hint (self)
22425 The CLI may call this method and use its result to change the
22426 formatting of a value. The result will also be supplied to an MI
22427 consumer as a @samp{displayhint} attribute of the variable being
22430 This method is optional. If it does exist, this method must return a
22433 Some display hints are predefined by @value{GDBN}:
22437 Indicate that the object being printed is ``array-like''. The CLI
22438 uses this to respect parameters such as @code{set print elements} and
22439 @code{set print array}.
22442 Indicate that the object being printed is ``map-like'', and that the
22443 children of this value can be assumed to alternate between keys and
22447 Indicate that the object being printed is ``string-like''. If the
22448 printer's @code{to_string} method returns a Python string of some
22449 kind, then @value{GDBN} will call its internal language-specific
22450 string-printing function to format the string. For the CLI this means
22451 adding quotation marks, possibly escaping some characters, respecting
22452 @code{set print elements}, and the like.
22456 @defun pretty_printer.to_string (self)
22457 @value{GDBN} will call this method to display the string
22458 representation of the value passed to the object's constructor.
22460 When printing from the CLI, if the @code{to_string} method exists,
22461 then @value{GDBN} will prepend its result to the values returned by
22462 @code{children}. Exactly how this formatting is done is dependent on
22463 the display hint, and may change as more hints are added. Also,
22464 depending on the print settings (@pxref{Print Settings}), the CLI may
22465 print just the result of @code{to_string} in a stack trace, omitting
22466 the result of @code{children}.
22468 If this method returns a string, it is printed verbatim.
22470 Otherwise, if this method returns an instance of @code{gdb.Value},
22471 then @value{GDBN} prints this value. This may result in a call to
22472 another pretty-printer.
22474 If instead the method returns a Python value which is convertible to a
22475 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22476 the resulting value. Again, this may result in a call to another
22477 pretty-printer. Python scalars (integers, floats, and booleans) and
22478 strings are convertible to @code{gdb.Value}; other types are not.
22480 Finally, if this method returns @code{None} then no further operations
22481 are peformed in this method and nothing is printed.
22483 If the result is not one of these types, an exception is raised.
22486 @value{GDBN} provides a function which can be used to look up the
22487 default pretty-printer for a @code{gdb.Value}:
22489 @findex gdb.default_visualizer
22490 @defun gdb.default_visualizer (value)
22491 This function takes a @code{gdb.Value} object as an argument. If a
22492 pretty-printer for this value exists, then it is returned. If no such
22493 printer exists, then this returns @code{None}.
22496 @node Selecting Pretty-Printers
22497 @subsubsection Selecting Pretty-Printers
22499 The Python list @code{gdb.pretty_printers} contains an array of
22500 functions or callable objects that have been registered via addition
22501 as a pretty-printer. Printers in this list are called @code{global}
22502 printers, they're available when debugging all inferiors.
22503 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22504 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22507 Each function on these lists is passed a single @code{gdb.Value}
22508 argument and should return a pretty-printer object conforming to the
22509 interface definition above (@pxref{Pretty Printing API}). If a function
22510 cannot create a pretty-printer for the value, it should return
22513 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22514 @code{gdb.Objfile} in the current program space and iteratively calls
22515 each enabled lookup routine in the list for that @code{gdb.Objfile}
22516 until it receives a pretty-printer object.
22517 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22518 searches the pretty-printer list of the current program space,
22519 calling each enabled function until an object is returned.
22520 After these lists have been exhausted, it tries the global
22521 @code{gdb.pretty_printers} list, again calling each enabled function until an
22522 object is returned.
22524 The order in which the objfiles are searched is not specified. For a
22525 given list, functions are always invoked from the head of the list,
22526 and iterated over sequentially until the end of the list, or a printer
22527 object is returned.
22529 For various reasons a pretty-printer may not work.
22530 For example, the underlying data structure may have changed and
22531 the pretty-printer is out of date.
22533 The consequences of a broken pretty-printer are severe enough that
22534 @value{GDBN} provides support for enabling and disabling individual
22535 printers. For example, if @code{print frame-arguments} is on,
22536 a backtrace can become highly illegible if any argument is printed
22537 with a broken printer.
22539 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22540 attribute to the registered function or callable object. If this attribute
22541 is present and its value is @code{False}, the printer is disabled, otherwise
22542 the printer is enabled.
22544 @node Writing a Pretty-Printer
22545 @subsubsection Writing a Pretty-Printer
22546 @cindex writing a pretty-printer
22548 A pretty-printer consists of two parts: a lookup function to detect
22549 if the type is supported, and the printer itself.
22551 Here is an example showing how a @code{std::string} printer might be
22552 written. @xref{Pretty Printing API}, for details on the API this class
22556 class StdStringPrinter(object):
22557 "Print a std::string"
22559 def __init__(self, val):
22562 def to_string(self):
22563 return self.val['_M_dataplus']['_M_p']
22565 def display_hint(self):
22569 And here is an example showing how a lookup function for the printer
22570 example above might be written.
22573 def str_lookup_function(val):
22574 lookup_tag = val.type.tag
22575 if lookup_tag == None:
22577 regex = re.compile("^std::basic_string<char,.*>$")
22578 if regex.match(lookup_tag):
22579 return StdStringPrinter(val)
22583 The example lookup function extracts the value's type, and attempts to
22584 match it to a type that it can pretty-print. If it is a type the
22585 printer can pretty-print, it will return a printer object. If not, it
22586 returns @code{None}.
22588 We recommend that you put your core pretty-printers into a Python
22589 package. If your pretty-printers are for use with a library, we
22590 further recommend embedding a version number into the package name.
22591 This practice will enable @value{GDBN} to load multiple versions of
22592 your pretty-printers at the same time, because they will have
22595 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22596 can be evaluated multiple times without changing its meaning. An
22597 ideal auto-load file will consist solely of @code{import}s of your
22598 printer modules, followed by a call to a register pretty-printers with
22599 the current objfile.
22601 Taken as a whole, this approach will scale nicely to multiple
22602 inferiors, each potentially using a different library version.
22603 Embedding a version number in the Python package name will ensure that
22604 @value{GDBN} is able to load both sets of printers simultaneously.
22605 Then, because the search for pretty-printers is done by objfile, and
22606 because your auto-loaded code took care to register your library's
22607 printers with a specific objfile, @value{GDBN} will find the correct
22608 printers for the specific version of the library used by each
22611 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22612 this code might appear in @code{gdb.libstdcxx.v6}:
22615 def register_printers(objfile):
22616 objfile.pretty_printers.append(str_lookup_function)
22620 And then the corresponding contents of the auto-load file would be:
22623 import gdb.libstdcxx.v6
22624 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22627 The previous example illustrates a basic pretty-printer.
22628 There are a few things that can be improved on.
22629 The printer doesn't have a name, making it hard to identify in a
22630 list of installed printers. The lookup function has a name, but
22631 lookup functions can have arbitrary, even identical, names.
22633 Second, the printer only handles one type, whereas a library typically has
22634 several types. One could install a lookup function for each desired type
22635 in the library, but one could also have a single lookup function recognize
22636 several types. The latter is the conventional way this is handled.
22637 If a pretty-printer can handle multiple data types, then its
22638 @dfn{subprinters} are the printers for the individual data types.
22640 The @code{gdb.printing} module provides a formal way of solving these
22641 problems (@pxref{gdb.printing}).
22642 Here is another example that handles multiple types.
22644 These are the types we are going to pretty-print:
22647 struct foo @{ int a, b; @};
22648 struct bar @{ struct foo x, y; @};
22651 Here are the printers:
22655 """Print a foo object."""
22657 def __init__(self, val):
22660 def to_string(self):
22661 return ("a=<" + str(self.val["a"]) +
22662 "> b=<" + str(self.val["b"]) + ">")
22665 """Print a bar object."""
22667 def __init__(self, val):
22670 def to_string(self):
22671 return ("x=<" + str(self.val["x"]) +
22672 "> y=<" + str(self.val["y"]) + ">")
22675 This example doesn't need a lookup function, that is handled by the
22676 @code{gdb.printing} module. Instead a function is provided to build up
22677 the object that handles the lookup.
22680 import gdb.printing
22682 def build_pretty_printer():
22683 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22685 pp.add_printer('foo', '^foo$', fooPrinter)
22686 pp.add_printer('bar', '^bar$', barPrinter)
22690 And here is the autoload support:
22693 import gdb.printing
22695 gdb.printing.register_pretty_printer(
22696 gdb.current_objfile(),
22697 my_library.build_pretty_printer())
22700 Finally, when this printer is loaded into @value{GDBN}, here is the
22701 corresponding output of @samp{info pretty-printer}:
22704 (gdb) info pretty-printer
22711 @node Inferiors In Python
22712 @subsubsection Inferiors In Python
22713 @cindex inferiors in Python
22715 @findex gdb.Inferior
22716 Programs which are being run under @value{GDBN} are called inferiors
22717 (@pxref{Inferiors and Programs}). Python scripts can access
22718 information about and manipulate inferiors controlled by @value{GDBN}
22719 via objects of the @code{gdb.Inferior} class.
22721 The following inferior-related functions are available in the @code{gdb}
22724 @defun gdb.inferiors ()
22725 Return a tuple containing all inferior objects.
22728 @defun gdb.selected_inferior ()
22729 Return an object representing the current inferior.
22732 A @code{gdb.Inferior} object has the following attributes:
22735 @defvar Inferior.num
22736 ID of inferior, as assigned by GDB.
22739 @defvar Inferior.pid
22740 Process ID of the inferior, as assigned by the underlying operating
22744 @defvar Inferior.was_attached
22745 Boolean signaling whether the inferior was created using `attach', or
22746 started by @value{GDBN} itself.
22750 A @code{gdb.Inferior} object has the following methods:
22753 @defun Inferior.is_valid ()
22754 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22755 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22756 if the inferior no longer exists within @value{GDBN}. All other
22757 @code{gdb.Inferior} methods will throw an exception if it is invalid
22758 at the time the method is called.
22761 @defun Inferior.threads ()
22762 This method returns a tuple holding all the threads which are valid
22763 when it is called. If there are no valid threads, the method will
22764 return an empty tuple.
22767 @findex gdb.read_memory
22768 @defun Inferior.read_memory (address, length)
22769 Read @var{length} bytes of memory from the inferior, starting at
22770 @var{address}. Returns a buffer object, which behaves much like an array
22771 or a string. It can be modified and given to the @code{gdb.write_memory}
22775 @findex gdb.write_memory
22776 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22777 Write the contents of @var{buffer} to the inferior, starting at
22778 @var{address}. The @var{buffer} parameter must be a Python object
22779 which supports the buffer protocol, i.e., a string, an array or the
22780 object returned from @code{gdb.read_memory}. If given, @var{length}
22781 determines the number of bytes from @var{buffer} to be written.
22784 @findex gdb.search_memory
22785 @defun Inferior.search_memory (address, length, pattern)
22786 Search a region of the inferior memory starting at @var{address} with
22787 the given @var{length} using the search pattern supplied in
22788 @var{pattern}. The @var{pattern} parameter must be a Python object
22789 which supports the buffer protocol, i.e., a string, an array or the
22790 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22791 containing the address where the pattern was found, or @code{None} if
22792 the pattern could not be found.
22796 @node Events In Python
22797 @subsubsection Events In Python
22798 @cindex inferior events in Python
22800 @value{GDBN} provides a general event facility so that Python code can be
22801 notified of various state changes, particularly changes that occur in
22804 An @dfn{event} is just an object that describes some state change. The
22805 type of the object and its attributes will vary depending on the details
22806 of the change. All the existing events are described below.
22808 In order to be notified of an event, you must register an event handler
22809 with an @dfn{event registry}. An event registry is an object in the
22810 @code{gdb.events} module which dispatches particular events. A registry
22811 provides methods to register and unregister event handlers:
22814 @defun EventRegistry.connect (object)
22815 Add the given callable @var{object} to the registry. This object will be
22816 called when an event corresponding to this registry occurs.
22819 @defun EventRegistry.disconnect (object)
22820 Remove the given @var{object} from the registry. Once removed, the object
22821 will no longer receive notifications of events.
22825 Here is an example:
22828 def exit_handler (event):
22829 print "event type: exit"
22830 print "exit code: %d" % (event.exit_code)
22832 gdb.events.exited.connect (exit_handler)
22835 In the above example we connect our handler @code{exit_handler} to the
22836 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22837 called when the inferior exits. The argument @dfn{event} in this example is
22838 of type @code{gdb.ExitedEvent}. As you can see in the example the
22839 @code{ExitedEvent} object has an attribute which indicates the exit code of
22842 The following is a listing of the event registries that are available and
22843 details of the events they emit:
22848 Emits @code{gdb.ThreadEvent}.
22850 Some events can be thread specific when @value{GDBN} is running in non-stop
22851 mode. When represented in Python, these events all extend
22852 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22853 events which are emitted by this or other modules might extend this event.
22854 Examples of these events are @code{gdb.BreakpointEvent} and
22855 @code{gdb.ContinueEvent}.
22858 @defvar ThreadEvent.inferior_thread
22859 In non-stop mode this attribute will be set to the specific thread which was
22860 involved in the emitted event. Otherwise, it will be set to @code{None}.
22864 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22866 This event indicates that the inferior has been continued after a stop. For
22867 inherited attribute refer to @code{gdb.ThreadEvent} above.
22869 @item events.exited
22870 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22871 @code{events.ExitedEvent} has two attributes:
22873 @defvar ExitedEvent.exit_code
22874 An integer representing the exit code, if available, which the inferior
22875 has returned. (The exit code could be unavailable if, for example,
22876 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22877 the attribute does not exist.
22879 @defvar ExitedEvent inferior
22880 A reference to the inferior which triggered the @code{exited} event.
22885 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22887 Indicates that the inferior has stopped. All events emitted by this registry
22888 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22889 will indicate the stopped thread when @value{GDBN} is running in non-stop
22890 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22892 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22894 This event indicates that the inferior or one of its threads has received as
22895 signal. @code{gdb.SignalEvent} has the following attributes:
22898 @defvar SignalEvent.stop_signal
22899 A string representing the signal received by the inferior. A list of possible
22900 signal values can be obtained by running the command @code{info signals} in
22901 the @value{GDBN} command prompt.
22905 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22907 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22908 been hit, and has the following attributes:
22911 @defvar BreakpointEvent.breakpoints
22912 A sequence containing references to all the breakpoints (type
22913 @code{gdb.Breakpoint}) that were hit.
22914 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22916 @defvar BreakpointEvent.breakpoint
22917 A reference to the first breakpoint that was hit.
22918 This function is maintained for backward compatibility and is now deprecated
22919 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22923 @item events.new_objfile
22924 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22925 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22928 @defvar NewObjFileEvent.new_objfile
22929 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22930 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22936 @node Threads In Python
22937 @subsubsection Threads In Python
22938 @cindex threads in python
22940 @findex gdb.InferiorThread
22941 Python scripts can access information about, and manipulate inferior threads
22942 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22944 The following thread-related functions are available in the @code{gdb}
22947 @findex gdb.selected_thread
22948 @defun gdb.selected_thread ()
22949 This function returns the thread object for the selected thread. If there
22950 is no selected thread, this will return @code{None}.
22953 A @code{gdb.InferiorThread} object has the following attributes:
22956 @defvar InferiorThread.name
22957 The name of the thread. If the user specified a name using
22958 @code{thread name}, then this returns that name. Otherwise, if an
22959 OS-supplied name is available, then it is returned. Otherwise, this
22960 returns @code{None}.
22962 This attribute can be assigned to. The new value must be a string
22963 object, which sets the new name, or @code{None}, which removes any
22964 user-specified thread name.
22967 @defvar InferiorThread.num
22968 ID of the thread, as assigned by GDB.
22971 @defvar InferiorThread.ptid
22972 ID of the thread, as assigned by the operating system. This attribute is a
22973 tuple containing three integers. The first is the Process ID (PID); the second
22974 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22975 Either the LWPID or TID may be 0, which indicates that the operating system
22976 does not use that identifier.
22980 A @code{gdb.InferiorThread} object has the following methods:
22983 @defun InferiorThread.is_valid ()
22984 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22985 @code{False} if not. A @code{gdb.InferiorThread} object will become
22986 invalid if the thread exits, or the inferior that the thread belongs
22987 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22988 exception if it is invalid at the time the method is called.
22991 @defun InferiorThread.switch ()
22992 This changes @value{GDBN}'s currently selected thread to the one represented
22996 @defun InferiorThread.is_stopped ()
22997 Return a Boolean indicating whether the thread is stopped.
23000 @defun InferiorThread.is_running ()
23001 Return a Boolean indicating whether the thread is running.
23004 @defun InferiorThread.is_exited ()
23005 Return a Boolean indicating whether the thread is exited.
23009 @node Commands In Python
23010 @subsubsection Commands In Python
23012 @cindex commands in python
23013 @cindex python commands
23014 You can implement new @value{GDBN} CLI commands in Python. A CLI
23015 command is implemented using an instance of the @code{gdb.Command}
23016 class, most commonly using a subclass.
23018 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23019 The object initializer for @code{Command} registers the new command
23020 with @value{GDBN}. This initializer is normally invoked from the
23021 subclass' own @code{__init__} method.
23023 @var{name} is the name of the command. If @var{name} consists of
23024 multiple words, then the initial words are looked for as prefix
23025 commands. In this case, if one of the prefix commands does not exist,
23026 an exception is raised.
23028 There is no support for multi-line commands.
23030 @var{command_class} should be one of the @samp{COMMAND_} constants
23031 defined below. This argument tells @value{GDBN} how to categorize the
23032 new command in the help system.
23034 @var{completer_class} is an optional argument. If given, it should be
23035 one of the @samp{COMPLETE_} constants defined below. This argument
23036 tells @value{GDBN} how to perform completion for this command. If not
23037 given, @value{GDBN} will attempt to complete using the object's
23038 @code{complete} method (see below); if no such method is found, an
23039 error will occur when completion is attempted.
23041 @var{prefix} is an optional argument. If @code{True}, then the new
23042 command is a prefix command; sub-commands of this command may be
23045 The help text for the new command is taken from the Python
23046 documentation string for the command's class, if there is one. If no
23047 documentation string is provided, the default value ``This command is
23048 not documented.'' is used.
23051 @cindex don't repeat Python command
23052 @defun Command.dont_repeat ()
23053 By default, a @value{GDBN} command is repeated when the user enters a
23054 blank line at the command prompt. A command can suppress this
23055 behavior by invoking the @code{dont_repeat} method. This is similar
23056 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23059 @defun Command.invoke (argument, from_tty)
23060 This method is called by @value{GDBN} when this command is invoked.
23062 @var{argument} is a string. It is the argument to the command, after
23063 leading and trailing whitespace has been stripped.
23065 @var{from_tty} is a boolean argument. When true, this means that the
23066 command was entered by the user at the terminal; when false it means
23067 that the command came from elsewhere.
23069 If this method throws an exception, it is turned into a @value{GDBN}
23070 @code{error} call. Otherwise, the return value is ignored.
23072 @findex gdb.string_to_argv
23073 To break @var{argument} up into an argv-like string use
23074 @code{gdb.string_to_argv}. This function behaves identically to
23075 @value{GDBN}'s internal argument lexer @code{buildargv}.
23076 It is recommended to use this for consistency.
23077 Arguments are separated by spaces and may be quoted.
23081 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23082 ['1', '2 "3', '4 "5', "6 '7"]
23087 @cindex completion of Python commands
23088 @defun Command.complete (text, word)
23089 This method is called by @value{GDBN} when the user attempts
23090 completion on this command. All forms of completion are handled by
23091 this method, that is, the @key{TAB} and @key{M-?} key bindings
23092 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23095 The arguments @var{text} and @var{word} are both strings. @var{text}
23096 holds the complete command line up to the cursor's location.
23097 @var{word} holds the last word of the command line; this is computed
23098 using a word-breaking heuristic.
23100 The @code{complete} method can return several values:
23103 If the return value is a sequence, the contents of the sequence are
23104 used as the completions. It is up to @code{complete} to ensure that the
23105 contents actually do complete the word. A zero-length sequence is
23106 allowed, it means that there were no completions available. Only
23107 string elements of the sequence are used; other elements in the
23108 sequence are ignored.
23111 If the return value is one of the @samp{COMPLETE_} constants defined
23112 below, then the corresponding @value{GDBN}-internal completion
23113 function is invoked, and its result is used.
23116 All other results are treated as though there were no available
23121 When a new command is registered, it must be declared as a member of
23122 some general class of commands. This is used to classify top-level
23123 commands in the on-line help system; note that prefix commands are not
23124 listed under their own category but rather that of their top-level
23125 command. The available classifications are represented by constants
23126 defined in the @code{gdb} module:
23129 @findex COMMAND_NONE
23130 @findex gdb.COMMAND_NONE
23131 @item gdb.COMMAND_NONE
23132 The command does not belong to any particular class. A command in
23133 this category will not be displayed in any of the help categories.
23135 @findex COMMAND_RUNNING
23136 @findex gdb.COMMAND_RUNNING
23137 @item gdb.COMMAND_RUNNING
23138 The command is related to running the inferior. For example,
23139 @code{start}, @code{step}, and @code{continue} are in this category.
23140 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23141 commands in this category.
23143 @findex COMMAND_DATA
23144 @findex gdb.COMMAND_DATA
23145 @item gdb.COMMAND_DATA
23146 The command is related to data or variables. For example,
23147 @code{call}, @code{find}, and @code{print} are in this category. Type
23148 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23151 @findex COMMAND_STACK
23152 @findex gdb.COMMAND_STACK
23153 @item gdb.COMMAND_STACK
23154 The command has to do with manipulation of the stack. For example,
23155 @code{backtrace}, @code{frame}, and @code{return} are in this
23156 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23157 list of commands in this category.
23159 @findex COMMAND_FILES
23160 @findex gdb.COMMAND_FILES
23161 @item gdb.COMMAND_FILES
23162 This class is used for file-related commands. For example,
23163 @code{file}, @code{list} and @code{section} are in this category.
23164 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23165 commands in this category.
23167 @findex COMMAND_SUPPORT
23168 @findex gdb.COMMAND_SUPPORT
23169 @item gdb.COMMAND_SUPPORT
23170 This should be used for ``support facilities'', generally meaning
23171 things that are useful to the user when interacting with @value{GDBN},
23172 but not related to the state of the inferior. For example,
23173 @code{help}, @code{make}, and @code{shell} are in this category. Type
23174 @kbd{help support} at the @value{GDBN} prompt to see a list of
23175 commands in this category.
23177 @findex COMMAND_STATUS
23178 @findex gdb.COMMAND_STATUS
23179 @item gdb.COMMAND_STATUS
23180 The command is an @samp{info}-related command, that is, related to the
23181 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23182 and @code{show} are in this category. Type @kbd{help status} at the
23183 @value{GDBN} prompt to see a list of commands in this category.
23185 @findex COMMAND_BREAKPOINTS
23186 @findex gdb.COMMAND_BREAKPOINTS
23187 @item gdb.COMMAND_BREAKPOINTS
23188 The command has to do with breakpoints. For example, @code{break},
23189 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23190 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23193 @findex COMMAND_TRACEPOINTS
23194 @findex gdb.COMMAND_TRACEPOINTS
23195 @item gdb.COMMAND_TRACEPOINTS
23196 The command has to do with tracepoints. For example, @code{trace},
23197 @code{actions}, and @code{tfind} are in this category. Type
23198 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23199 commands in this category.
23201 @findex COMMAND_OBSCURE
23202 @findex gdb.COMMAND_OBSCURE
23203 @item gdb.COMMAND_OBSCURE
23204 The command is only used in unusual circumstances, or is not of
23205 general interest to users. For example, @code{checkpoint},
23206 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23207 obscure} at the @value{GDBN} prompt to see a list of commands in this
23210 @findex COMMAND_MAINTENANCE
23211 @findex gdb.COMMAND_MAINTENANCE
23212 @item gdb.COMMAND_MAINTENANCE
23213 The command is only useful to @value{GDBN} maintainers. The
23214 @code{maintenance} and @code{flushregs} commands are in this category.
23215 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23216 commands in this category.
23219 A new command can use a predefined completion function, either by
23220 specifying it via an argument at initialization, or by returning it
23221 from the @code{complete} method. These predefined completion
23222 constants are all defined in the @code{gdb} module:
23225 @findex COMPLETE_NONE
23226 @findex gdb.COMPLETE_NONE
23227 @item gdb.COMPLETE_NONE
23228 This constant means that no completion should be done.
23230 @findex COMPLETE_FILENAME
23231 @findex gdb.COMPLETE_FILENAME
23232 @item gdb.COMPLETE_FILENAME
23233 This constant means that filename completion should be performed.
23235 @findex COMPLETE_LOCATION
23236 @findex gdb.COMPLETE_LOCATION
23237 @item gdb.COMPLETE_LOCATION
23238 This constant means that location completion should be done.
23239 @xref{Specify Location}.
23241 @findex COMPLETE_COMMAND
23242 @findex gdb.COMPLETE_COMMAND
23243 @item gdb.COMPLETE_COMMAND
23244 This constant means that completion should examine @value{GDBN}
23247 @findex COMPLETE_SYMBOL
23248 @findex gdb.COMPLETE_SYMBOL
23249 @item gdb.COMPLETE_SYMBOL
23250 This constant means that completion should be done using symbol names
23254 The following code snippet shows how a trivial CLI command can be
23255 implemented in Python:
23258 class HelloWorld (gdb.Command):
23259 """Greet the whole world."""
23261 def __init__ (self):
23262 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23264 def invoke (self, arg, from_tty):
23265 print "Hello, World!"
23270 The last line instantiates the class, and is necessary to trigger the
23271 registration of the command with @value{GDBN}. Depending on how the
23272 Python code is read into @value{GDBN}, you may need to import the
23273 @code{gdb} module explicitly.
23275 @node Parameters In Python
23276 @subsubsection Parameters In Python
23278 @cindex parameters in python
23279 @cindex python parameters
23280 @tindex gdb.Parameter
23282 You can implement new @value{GDBN} parameters using Python. A new
23283 parameter is implemented as an instance of the @code{gdb.Parameter}
23286 Parameters are exposed to the user via the @code{set} and
23287 @code{show} commands. @xref{Help}.
23289 There are many parameters that already exist and can be set in
23290 @value{GDBN}. Two examples are: @code{set follow fork} and
23291 @code{set charset}. Setting these parameters influences certain
23292 behavior in @value{GDBN}. Similarly, you can define parameters that
23293 can be used to influence behavior in custom Python scripts and commands.
23295 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23296 The object initializer for @code{Parameter} registers the new
23297 parameter with @value{GDBN}. This initializer is normally invoked
23298 from the subclass' own @code{__init__} method.
23300 @var{name} is the name of the new parameter. If @var{name} consists
23301 of multiple words, then the initial words are looked for as prefix
23302 parameters. An example of this can be illustrated with the
23303 @code{set print} set of parameters. If @var{name} is
23304 @code{print foo}, then @code{print} will be searched as the prefix
23305 parameter. In this case the parameter can subsequently be accessed in
23306 @value{GDBN} as @code{set print foo}.
23308 If @var{name} consists of multiple words, and no prefix parameter group
23309 can be found, an exception is raised.
23311 @var{command-class} should be one of the @samp{COMMAND_} constants
23312 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23313 categorize the new parameter in the help system.
23315 @var{parameter-class} should be one of the @samp{PARAM_} constants
23316 defined below. This argument tells @value{GDBN} the type of the new
23317 parameter; this information is used for input validation and
23320 If @var{parameter-class} is @code{PARAM_ENUM}, then
23321 @var{enum-sequence} must be a sequence of strings. These strings
23322 represent the possible values for the parameter.
23324 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23325 of a fourth argument will cause an exception to be thrown.
23327 The help text for the new parameter is taken from the Python
23328 documentation string for the parameter's class, if there is one. If
23329 there is no documentation string, a default value is used.
23332 @defvar Parameter.set_doc
23333 If this attribute exists, and is a string, then its value is used as
23334 the help text for this parameter's @code{set} command. The value is
23335 examined when @code{Parameter.__init__} is invoked; subsequent changes
23339 @defvar Parameter.show_doc
23340 If this attribute exists, and is a string, then its value is used as
23341 the help text for this parameter's @code{show} command. The value is
23342 examined when @code{Parameter.__init__} is invoked; subsequent changes
23346 @defvar Parameter.value
23347 The @code{value} attribute holds the underlying value of the
23348 parameter. It can be read and assigned to just as any other
23349 attribute. @value{GDBN} does validation when assignments are made.
23352 There are two methods that should be implemented in any
23353 @code{Parameter} class. These are:
23355 @defun Parameter.get_set_string (self)
23356 @value{GDBN} will call this method when a @var{parameter}'s value has
23357 been changed via the @code{set} API (for example, @kbd{set foo off}).
23358 The @code{value} attribute has already been populated with the new
23359 value and may be used in output. This method must return a string.
23362 @defun Parameter.get_show_string (self, svalue)
23363 @value{GDBN} will call this method when a @var{parameter}'s
23364 @code{show} API has been invoked (for example, @kbd{show foo}). The
23365 argument @code{svalue} receives the string representation of the
23366 current value. This method must return a string.
23369 When a new parameter is defined, its type must be specified. The
23370 available types are represented by constants defined in the @code{gdb}
23374 @findex PARAM_BOOLEAN
23375 @findex gdb.PARAM_BOOLEAN
23376 @item gdb.PARAM_BOOLEAN
23377 The value is a plain boolean. The Python boolean values, @code{True}
23378 and @code{False} are the only valid values.
23380 @findex PARAM_AUTO_BOOLEAN
23381 @findex gdb.PARAM_AUTO_BOOLEAN
23382 @item gdb.PARAM_AUTO_BOOLEAN
23383 The value has three possible states: true, false, and @samp{auto}. In
23384 Python, true and false are represented using boolean constants, and
23385 @samp{auto} is represented using @code{None}.
23387 @findex PARAM_UINTEGER
23388 @findex gdb.PARAM_UINTEGER
23389 @item gdb.PARAM_UINTEGER
23390 The value is an unsigned integer. The value of 0 should be
23391 interpreted to mean ``unlimited''.
23393 @findex PARAM_INTEGER
23394 @findex gdb.PARAM_INTEGER
23395 @item gdb.PARAM_INTEGER
23396 The value is a signed integer. The value of 0 should be interpreted
23397 to mean ``unlimited''.
23399 @findex PARAM_STRING
23400 @findex gdb.PARAM_STRING
23401 @item gdb.PARAM_STRING
23402 The value is a string. When the user modifies the string, any escape
23403 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23404 translated into corresponding characters and encoded into the current
23407 @findex PARAM_STRING_NOESCAPE
23408 @findex gdb.PARAM_STRING_NOESCAPE
23409 @item gdb.PARAM_STRING_NOESCAPE
23410 The value is a string. When the user modifies the string, escapes are
23411 passed through untranslated.
23413 @findex PARAM_OPTIONAL_FILENAME
23414 @findex gdb.PARAM_OPTIONAL_FILENAME
23415 @item gdb.PARAM_OPTIONAL_FILENAME
23416 The value is a either a filename (a string), or @code{None}.
23418 @findex PARAM_FILENAME
23419 @findex gdb.PARAM_FILENAME
23420 @item gdb.PARAM_FILENAME
23421 The value is a filename. This is just like
23422 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23424 @findex PARAM_ZINTEGER
23425 @findex gdb.PARAM_ZINTEGER
23426 @item gdb.PARAM_ZINTEGER
23427 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23428 is interpreted as itself.
23431 @findex gdb.PARAM_ENUM
23432 @item gdb.PARAM_ENUM
23433 The value is a string, which must be one of a collection string
23434 constants provided when the parameter is created.
23437 @node Functions In Python
23438 @subsubsection Writing new convenience functions
23440 @cindex writing convenience functions
23441 @cindex convenience functions in python
23442 @cindex python convenience functions
23443 @tindex gdb.Function
23445 You can implement new convenience functions (@pxref{Convenience Vars})
23446 in Python. A convenience function is an instance of a subclass of the
23447 class @code{gdb.Function}.
23449 @defun Function.__init__ (name)
23450 The initializer for @code{Function} registers the new function with
23451 @value{GDBN}. The argument @var{name} is the name of the function,
23452 a string. The function will be visible to the user as a convenience
23453 variable of type @code{internal function}, whose name is the same as
23454 the given @var{name}.
23456 The documentation for the new function is taken from the documentation
23457 string for the new class.
23460 @defun Function.invoke (@var{*args})
23461 When a convenience function is evaluated, its arguments are converted
23462 to instances of @code{gdb.Value}, and then the function's
23463 @code{invoke} method is called. Note that @value{GDBN} does not
23464 predetermine the arity of convenience functions. Instead, all
23465 available arguments are passed to @code{invoke}, following the
23466 standard Python calling convention. In particular, a convenience
23467 function can have default values for parameters without ill effect.
23469 The return value of this method is used as its value in the enclosing
23470 expression. If an ordinary Python value is returned, it is converted
23471 to a @code{gdb.Value} following the usual rules.
23474 The following code snippet shows how a trivial convenience function can
23475 be implemented in Python:
23478 class Greet (gdb.Function):
23479 """Return string to greet someone.
23480 Takes a name as argument."""
23482 def __init__ (self):
23483 super (Greet, self).__init__ ("greet")
23485 def invoke (self, name):
23486 return "Hello, %s!" % name.string ()
23491 The last line instantiates the class, and is necessary to trigger the
23492 registration of the function with @value{GDBN}. Depending on how the
23493 Python code is read into @value{GDBN}, you may need to import the
23494 @code{gdb} module explicitly.
23496 @node Progspaces In Python
23497 @subsubsection Program Spaces In Python
23499 @cindex progspaces in python
23500 @tindex gdb.Progspace
23502 A program space, or @dfn{progspace}, represents a symbolic view
23503 of an address space.
23504 It consists of all of the objfiles of the program.
23505 @xref{Objfiles In Python}.
23506 @xref{Inferiors and Programs, program spaces}, for more details
23507 about program spaces.
23509 The following progspace-related functions are available in the
23512 @findex gdb.current_progspace
23513 @defun gdb.current_progspace ()
23514 This function returns the program space of the currently selected inferior.
23515 @xref{Inferiors and Programs}.
23518 @findex gdb.progspaces
23519 @defun gdb.progspaces ()
23520 Return a sequence of all the progspaces currently known to @value{GDBN}.
23523 Each progspace is represented by an instance of the @code{gdb.Progspace}
23526 @defvar Progspace.filename
23527 The file name of the progspace as a string.
23530 @defvar Progspace.pretty_printers
23531 The @code{pretty_printers} attribute is a list of functions. It is
23532 used to look up pretty-printers. A @code{Value} is passed to each
23533 function in order; if the function returns @code{None}, then the
23534 search continues. Otherwise, the return value should be an object
23535 which is used to format the value. @xref{Pretty Printing API}, for more
23539 @node Objfiles In Python
23540 @subsubsection Objfiles In Python
23542 @cindex objfiles in python
23543 @tindex gdb.Objfile
23545 @value{GDBN} loads symbols for an inferior from various
23546 symbol-containing files (@pxref{Files}). These include the primary
23547 executable file, any shared libraries used by the inferior, and any
23548 separate debug info files (@pxref{Separate Debug Files}).
23549 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23551 The following objfile-related functions are available in the
23554 @findex gdb.current_objfile
23555 @defun gdb.current_objfile ()
23556 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23557 sets the ``current objfile'' to the corresponding objfile. This
23558 function returns the current objfile. If there is no current objfile,
23559 this function returns @code{None}.
23562 @findex gdb.objfiles
23563 @defun gdb.objfiles ()
23564 Return a sequence of all the objfiles current known to @value{GDBN}.
23565 @xref{Objfiles In Python}.
23568 Each objfile is represented by an instance of the @code{gdb.Objfile}
23571 @defvar Objfile.filename
23572 The file name of the objfile as a string.
23575 @defvar Objfile.pretty_printers
23576 The @code{pretty_printers} attribute is a list of functions. It is
23577 used to look up pretty-printers. A @code{Value} is passed to each
23578 function in order; if the function returns @code{None}, then the
23579 search continues. Otherwise, the return value should be an object
23580 which is used to format the value. @xref{Pretty Printing API}, for more
23584 A @code{gdb.Objfile} object has the following methods:
23586 @defun Objfile.is_valid ()
23587 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23588 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23589 if the object file it refers to is not loaded in @value{GDBN} any
23590 longer. All other @code{gdb.Objfile} methods will throw an exception
23591 if it is invalid at the time the method is called.
23594 @node Frames In Python
23595 @subsubsection Accessing inferior stack frames from Python.
23597 @cindex frames in python
23598 When the debugged program stops, @value{GDBN} is able to analyze its call
23599 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23600 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23601 while its corresponding frame exists in the inferior's stack. If you try
23602 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23603 exception (@pxref{Exception Handling}).
23605 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23609 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23613 The following frame-related functions are available in the @code{gdb} module:
23615 @findex gdb.selected_frame
23616 @defun gdb.selected_frame ()
23617 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23620 @findex gdb.newest_frame
23621 @defun gdb.newest_frame ()
23622 Return the newest frame object for the selected thread.
23625 @defun gdb.frame_stop_reason_string (reason)
23626 Return a string explaining the reason why @value{GDBN} stopped unwinding
23627 frames, as expressed by the given @var{reason} code (an integer, see the
23628 @code{unwind_stop_reason} method further down in this section).
23631 A @code{gdb.Frame} object has the following methods:
23634 @defun Frame.is_valid ()
23635 Returns true if the @code{gdb.Frame} object is valid, false if not.
23636 A frame object can become invalid if the frame it refers to doesn't
23637 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23638 an exception if it is invalid at the time the method is called.
23641 @defun Frame.name ()
23642 Returns the function name of the frame, or @code{None} if it can't be
23646 @defun Frame.type ()
23647 Returns the type of the frame. The value can be one of:
23649 @item gdb.NORMAL_FRAME
23650 An ordinary stack frame.
23652 @item gdb.DUMMY_FRAME
23653 A fake stack frame that was created by @value{GDBN} when performing an
23654 inferior function call.
23656 @item gdb.INLINE_FRAME
23657 A frame representing an inlined function. The function was inlined
23658 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23660 @item gdb.TAILCALL_FRAME
23661 A frame representing a tail call. @xref{Tail Call Frames}.
23663 @item gdb.SIGTRAMP_FRAME
23664 A signal trampoline frame. This is the frame created by the OS when
23665 it calls into a signal handler.
23667 @item gdb.ARCH_FRAME
23668 A fake stack frame representing a cross-architecture call.
23670 @item gdb.SENTINEL_FRAME
23671 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23676 @defun Frame.unwind_stop_reason ()
23677 Return an integer representing the reason why it's not possible to find
23678 more frames toward the outermost frame. Use
23679 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23680 function to a string. The value can be one of:
23683 @item gdb.FRAME_UNWIND_NO_REASON
23684 No particular reason (older frames should be available).
23686 @item gdb.FRAME_UNWIND_NULL_ID
23687 The previous frame's analyzer returns an invalid result.
23689 @item gdb.FRAME_UNWIND_OUTERMOST
23690 This frame is the outermost.
23692 @item gdb.FRAME_UNWIND_UNAVAILABLE
23693 Cannot unwind further, because that would require knowing the
23694 values of registers or memory that have not been collected.
23696 @item gdb.FRAME_UNWIND_INNER_ID
23697 This frame ID looks like it ought to belong to a NEXT frame,
23698 but we got it for a PREV frame. Normally, this is a sign of
23699 unwinder failure. It could also indicate stack corruption.
23701 @item gdb.FRAME_UNWIND_SAME_ID
23702 This frame has the same ID as the previous one. That means
23703 that unwinding further would almost certainly give us another
23704 frame with exactly the same ID, so break the chain. Normally,
23705 this is a sign of unwinder failure. It could also indicate
23708 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23709 The frame unwinder did not find any saved PC, but we needed
23710 one to unwind further.
23712 @item gdb.FRAME_UNWIND_FIRST_ERROR
23713 Any stop reason greater or equal to this value indicates some kind
23714 of error. This special value facilitates writing code that tests
23715 for errors in unwinding in a way that will work correctly even if
23716 the list of the other values is modified in future @value{GDBN}
23717 versions. Using it, you could write:
23719 reason = gdb.selected_frame().unwind_stop_reason ()
23720 reason_str = gdb.frame_stop_reason_string (reason)
23721 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23722 print "An error occured: %s" % reason_str
23729 Returns the frame's resume address.
23732 @defun Frame.block ()
23733 Return the frame's code block. @xref{Blocks In Python}.
23736 @defun Frame.function ()
23737 Return the symbol for the function corresponding to this frame.
23738 @xref{Symbols In Python}.
23741 @defun Frame.older ()
23742 Return the frame that called this frame.
23745 @defun Frame.newer ()
23746 Return the frame called by this frame.
23749 @defun Frame.find_sal ()
23750 Return the frame's symtab and line object.
23751 @xref{Symbol Tables In Python}.
23754 @defun Frame.read_var (variable @r{[}, block@r{]})
23755 Return the value of @var{variable} in this frame. If the optional
23756 argument @var{block} is provided, search for the variable from that
23757 block; otherwise start at the frame's current block (which is
23758 determined by the frame's current program counter). @var{variable}
23759 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23760 @code{gdb.Block} object.
23763 @defun Frame.select ()
23764 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23769 @node Blocks In Python
23770 @subsubsection Accessing frame blocks from Python.
23772 @cindex blocks in python
23775 Within each frame, @value{GDBN} maintains information on each block
23776 stored in that frame. These blocks are organized hierarchically, and
23777 are represented individually in Python as a @code{gdb.Block}.
23778 Please see @ref{Frames In Python}, for a more in-depth discussion on
23779 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23780 detailed technical information on @value{GDBN}'s book-keeping of the
23783 The following block-related functions are available in the @code{gdb}
23786 @findex gdb.block_for_pc
23787 @defun gdb.block_for_pc (pc)
23788 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23789 block cannot be found for the @var{pc} value specified, the function
23790 will return @code{None}.
23793 A @code{gdb.Block} object has the following methods:
23796 @defun Block.is_valid ()
23797 Returns @code{True} if the @code{gdb.Block} object is valid,
23798 @code{False} if not. A block object can become invalid if the block it
23799 refers to doesn't exist anymore in the inferior. All other
23800 @code{gdb.Block} methods will throw an exception if it is invalid at
23801 the time the method is called. This method is also made available to
23802 the Python iterator object that @code{gdb.Block} provides in an iteration
23803 context and via the Python @code{iter} built-in function.
23807 A @code{gdb.Block} object has the following attributes:
23810 @defvar Block.start
23811 The start address of the block. This attribute is not writable.
23815 The end address of the block. This attribute is not writable.
23818 @defvar Block.function
23819 The name of the block represented as a @code{gdb.Symbol}. If the
23820 block is not named, then this attribute holds @code{None}. This
23821 attribute is not writable.
23824 @defvar Block.superblock
23825 The block containing this block. If this parent block does not exist,
23826 this attribute holds @code{None}. This attribute is not writable.
23829 @defvar Block.global_block
23830 The global block associated with this block. This attribute is not
23834 @defvar Block.static_block
23835 The static block associated with this block. This attribute is not
23839 @defvar Block.is_global
23840 @code{True} if the @code{gdb.Block} object is a global block,
23841 @code{False} if not. This attribute is not
23845 @defvar Block.is_static
23846 @code{True} if the @code{gdb.Block} object is a static block,
23847 @code{False} if not. This attribute is not writable.
23851 @node Symbols In Python
23852 @subsubsection Python representation of Symbols.
23854 @cindex symbols in python
23857 @value{GDBN} represents every variable, function and type as an
23858 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23859 Similarly, Python represents these symbols in @value{GDBN} with the
23860 @code{gdb.Symbol} object.
23862 The following symbol-related functions are available in the @code{gdb}
23865 @findex gdb.lookup_symbol
23866 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23867 This function searches for a symbol by name. The search scope can be
23868 restricted to the parameters defined in the optional domain and block
23871 @var{name} is the name of the symbol. It must be a string. The
23872 optional @var{block} argument restricts the search to symbols visible
23873 in that @var{block}. The @var{block} argument must be a
23874 @code{gdb.Block} object. If omitted, the block for the current frame
23875 is used. The optional @var{domain} argument restricts
23876 the search to the domain type. The @var{domain} argument must be a
23877 domain constant defined in the @code{gdb} module and described later
23880 The result is a tuple of two elements.
23881 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23883 If the symbol is found, the second element is @code{True} if the symbol
23884 is a field of a method's object (e.g., @code{this} in C@t{++}),
23885 otherwise it is @code{False}.
23886 If the symbol is not found, the second element is @code{False}.
23889 @findex gdb.lookup_global_symbol
23890 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23891 This function searches for a global symbol by name.
23892 The search scope can be restricted to by the domain argument.
23894 @var{name} is the name of the symbol. It must be a string.
23895 The optional @var{domain} argument restricts the search to the domain type.
23896 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23897 module and described later in this chapter.
23899 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23903 A @code{gdb.Symbol} object has the following attributes:
23906 @defvar Symbol.type
23907 The type of the symbol or @code{None} if no type is recorded.
23908 This attribute is represented as a @code{gdb.Type} object.
23909 @xref{Types In Python}. This attribute is not writable.
23912 @defvar Symbol.symtab
23913 The symbol table in which the symbol appears. This attribute is
23914 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23915 Python}. This attribute is not writable.
23918 @defvar Symbol.name
23919 The name of the symbol as a string. This attribute is not writable.
23922 @defvar Symbol.linkage_name
23923 The name of the symbol, as used by the linker (i.e., may be mangled).
23924 This attribute is not writable.
23927 @defvar Symbol.print_name
23928 The name of the symbol in a form suitable for output. This is either
23929 @code{name} or @code{linkage_name}, depending on whether the user
23930 asked @value{GDBN} to display demangled or mangled names.
23933 @defvar Symbol.addr_class
23934 The address class of the symbol. This classifies how to find the value
23935 of a symbol. Each address class is a constant defined in the
23936 @code{gdb} module and described later in this chapter.
23939 @defvar Symbol.is_argument
23940 @code{True} if the symbol is an argument of a function.
23943 @defvar Symbol.is_constant
23944 @code{True} if the symbol is a constant.
23947 @defvar Symbol.is_function
23948 @code{True} if the symbol is a function or a method.
23951 @defvar Symbol.is_variable
23952 @code{True} if the symbol is a variable.
23956 A @code{gdb.Symbol} object has the following methods:
23959 @defun Symbol.is_valid ()
23960 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23961 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23962 the symbol it refers to does not exist in @value{GDBN} any longer.
23963 All other @code{gdb.Symbol} methods will throw an exception if it is
23964 invalid at the time the method is called.
23968 The available domain categories in @code{gdb.Symbol} are represented
23969 as constants in the @code{gdb} module:
23972 @findex SYMBOL_UNDEF_DOMAIN
23973 @findex gdb.SYMBOL_UNDEF_DOMAIN
23974 @item gdb.SYMBOL_UNDEF_DOMAIN
23975 This is used when a domain has not been discovered or none of the
23976 following domains apply. This usually indicates an error either
23977 in the symbol information or in @value{GDBN}'s handling of symbols.
23978 @findex SYMBOL_VAR_DOMAIN
23979 @findex gdb.SYMBOL_VAR_DOMAIN
23980 @item gdb.SYMBOL_VAR_DOMAIN
23981 This domain contains variables, function names, typedef names and enum
23983 @findex SYMBOL_STRUCT_DOMAIN
23984 @findex gdb.SYMBOL_STRUCT_DOMAIN
23985 @item gdb.SYMBOL_STRUCT_DOMAIN
23986 This domain holds struct, union and enum type names.
23987 @findex SYMBOL_LABEL_DOMAIN
23988 @findex gdb.SYMBOL_LABEL_DOMAIN
23989 @item gdb.SYMBOL_LABEL_DOMAIN
23990 This domain contains names of labels (for gotos).
23991 @findex SYMBOL_VARIABLES_DOMAIN
23992 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23993 @item gdb.SYMBOL_VARIABLES_DOMAIN
23994 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23995 contains everything minus functions and types.
23996 @findex SYMBOL_FUNCTIONS_DOMAIN
23997 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23998 @item gdb.SYMBOL_FUNCTION_DOMAIN
23999 This domain contains all functions.
24000 @findex SYMBOL_TYPES_DOMAIN
24001 @findex gdb.SYMBOL_TYPES_DOMAIN
24002 @item gdb.SYMBOL_TYPES_DOMAIN
24003 This domain contains all types.
24006 The available address class categories in @code{gdb.Symbol} are represented
24007 as constants in the @code{gdb} module:
24010 @findex SYMBOL_LOC_UNDEF
24011 @findex gdb.SYMBOL_LOC_UNDEF
24012 @item gdb.SYMBOL_LOC_UNDEF
24013 If this is returned by address class, it indicates an error either in
24014 the symbol information or in @value{GDBN}'s handling of symbols.
24015 @findex SYMBOL_LOC_CONST
24016 @findex gdb.SYMBOL_LOC_CONST
24017 @item gdb.SYMBOL_LOC_CONST
24018 Value is constant int.
24019 @findex SYMBOL_LOC_STATIC
24020 @findex gdb.SYMBOL_LOC_STATIC
24021 @item gdb.SYMBOL_LOC_STATIC
24022 Value is at a fixed address.
24023 @findex SYMBOL_LOC_REGISTER
24024 @findex gdb.SYMBOL_LOC_REGISTER
24025 @item gdb.SYMBOL_LOC_REGISTER
24026 Value is in a register.
24027 @findex SYMBOL_LOC_ARG
24028 @findex gdb.SYMBOL_LOC_ARG
24029 @item gdb.SYMBOL_LOC_ARG
24030 Value is an argument. This value is at the offset stored within the
24031 symbol inside the frame's argument list.
24032 @findex SYMBOL_LOC_REF_ARG
24033 @findex gdb.SYMBOL_LOC_REF_ARG
24034 @item gdb.SYMBOL_LOC_REF_ARG
24035 Value address is stored in the frame's argument list. Just like
24036 @code{LOC_ARG} except that the value's address is stored at the
24037 offset, not the value itself.
24038 @findex SYMBOL_LOC_REGPARM_ADDR
24039 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24040 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24041 Value is a specified register. Just like @code{LOC_REGISTER} except
24042 the register holds the address of the argument instead of the argument
24044 @findex SYMBOL_LOC_LOCAL
24045 @findex gdb.SYMBOL_LOC_LOCAL
24046 @item gdb.SYMBOL_LOC_LOCAL
24047 Value is a local variable.
24048 @findex SYMBOL_LOC_TYPEDEF
24049 @findex gdb.SYMBOL_LOC_TYPEDEF
24050 @item gdb.SYMBOL_LOC_TYPEDEF
24051 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24053 @findex SYMBOL_LOC_BLOCK
24054 @findex gdb.SYMBOL_LOC_BLOCK
24055 @item gdb.SYMBOL_LOC_BLOCK
24057 @findex SYMBOL_LOC_CONST_BYTES
24058 @findex gdb.SYMBOL_LOC_CONST_BYTES
24059 @item gdb.SYMBOL_LOC_CONST_BYTES
24060 Value is a byte-sequence.
24061 @findex SYMBOL_LOC_UNRESOLVED
24062 @findex gdb.SYMBOL_LOC_UNRESOLVED
24063 @item gdb.SYMBOL_LOC_UNRESOLVED
24064 Value is at a fixed address, but the address of the variable has to be
24065 determined from the minimal symbol table whenever the variable is
24067 @findex SYMBOL_LOC_OPTIMIZED_OUT
24068 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24069 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24070 The value does not actually exist in the program.
24071 @findex SYMBOL_LOC_COMPUTED
24072 @findex gdb.SYMBOL_LOC_COMPUTED
24073 @item gdb.SYMBOL_LOC_COMPUTED
24074 The value's address is a computed location.
24077 @node Symbol Tables In Python
24078 @subsubsection Symbol table representation in Python.
24080 @cindex symbol tables in python
24082 @tindex gdb.Symtab_and_line
24084 Access to symbol table data maintained by @value{GDBN} on the inferior
24085 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24086 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24087 from the @code{find_sal} method in @code{gdb.Frame} object.
24088 @xref{Frames In Python}.
24090 For more information on @value{GDBN}'s symbol table management, see
24091 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24093 A @code{gdb.Symtab_and_line} object has the following attributes:
24096 @defvar Symtab_and_line.symtab
24097 The symbol table object (@code{gdb.Symtab}) for this frame.
24098 This attribute is not writable.
24101 @defvar Symtab_and_line.pc
24102 Indicates the current program counter address. This attribute is not
24106 @defvar Symtab_and_line.line
24107 Indicates the current line number for this object. This
24108 attribute is not writable.
24112 A @code{gdb.Symtab_and_line} object has the following methods:
24115 @defun Symtab_and_line.is_valid ()
24116 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24117 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24118 invalid if the Symbol table and line object it refers to does not
24119 exist in @value{GDBN} any longer. All other
24120 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24121 invalid at the time the method is called.
24125 A @code{gdb.Symtab} object has the following attributes:
24128 @defvar Symtab.filename
24129 The symbol table's source filename. This attribute is not writable.
24132 @defvar Symtab.objfile
24133 The symbol table's backing object file. @xref{Objfiles In Python}.
24134 This attribute is not writable.
24138 A @code{gdb.Symtab} object has the following methods:
24141 @defun Symtab.is_valid ()
24142 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24143 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24144 the symbol table it refers to does not exist in @value{GDBN} any
24145 longer. All other @code{gdb.Symtab} methods will throw an exception
24146 if it is invalid at the time the method is called.
24149 @defun Symtab.fullname ()
24150 Return the symbol table's source absolute file name.
24154 @node Breakpoints In Python
24155 @subsubsection Manipulating breakpoints using Python
24157 @cindex breakpoints in python
24158 @tindex gdb.Breakpoint
24160 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24163 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24164 Create a new breakpoint. @var{spec} is a string naming the
24165 location of the breakpoint, or an expression that defines a
24166 watchpoint. The contents can be any location recognized by the
24167 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24168 command. The optional @var{type} denotes the breakpoint to create
24169 from the types defined later in this chapter. This argument can be
24170 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24171 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24172 allows the breakpoint to become invisible to the user. The breakpoint
24173 will neither be reported when created, nor will it be listed in the
24174 output from @code{info breakpoints} (but will be listed with the
24175 @code{maint info breakpoints} command). The optional @var{wp_class}
24176 argument defines the class of watchpoint to create, if @var{type} is
24177 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24178 assumed to be a @code{gdb.WP_WRITE} class.
24181 @defun Breakpoint.stop (self)
24182 The @code{gdb.Breakpoint} class can be sub-classed and, in
24183 particular, you may choose to implement the @code{stop} method.
24184 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24185 it will be called when the inferior reaches any location of a
24186 breakpoint which instantiates that sub-class. If the method returns
24187 @code{True}, the inferior will be stopped at the location of the
24188 breakpoint, otherwise the inferior will continue.
24190 If there are multiple breakpoints at the same location with a
24191 @code{stop} method, each one will be called regardless of the
24192 return status of the previous. This ensures that all @code{stop}
24193 methods have a chance to execute at that location. In this scenario
24194 if one of the methods returns @code{True} but the others return
24195 @code{False}, the inferior will still be stopped.
24197 You should not alter the execution state of the inferior (i.e.@:, step,
24198 next, etc.), alter the current frame context (i.e.@:, change the current
24199 active frame), or alter, add or delete any breakpoint. As a general
24200 rule, you should not alter any data within @value{GDBN} or the inferior
24203 Example @code{stop} implementation:
24206 class MyBreakpoint (gdb.Breakpoint):
24208 inf_val = gdb.parse_and_eval("foo")
24215 The available watchpoint types represented by constants are defined in the
24220 @findex gdb.WP_READ
24222 Read only watchpoint.
24225 @findex gdb.WP_WRITE
24227 Write only watchpoint.
24230 @findex gdb.WP_ACCESS
24231 @item gdb.WP_ACCESS
24232 Read/Write watchpoint.
24235 @defun Breakpoint.is_valid ()
24236 Return @code{True} if this @code{Breakpoint} object is valid,
24237 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24238 if the user deletes the breakpoint. In this case, the object still
24239 exists, but the underlying breakpoint does not. In the cases of
24240 watchpoint scope, the watchpoint remains valid even if execution of the
24241 inferior leaves the scope of that watchpoint.
24244 @defun Breakpoint.delete
24245 Permanently deletes the @value{GDBN} breakpoint. This also
24246 invalidates the Python @code{Breakpoint} object. Any further access
24247 to this object's attributes or methods will raise an error.
24250 @defvar Breakpoint.enabled
24251 This attribute is @code{True} if the breakpoint is enabled, and
24252 @code{False} otherwise. This attribute is writable.
24255 @defvar Breakpoint.silent
24256 This attribute is @code{True} if the breakpoint is silent, and
24257 @code{False} otherwise. This attribute is writable.
24259 Note that a breakpoint can also be silent if it has commands and the
24260 first command is @code{silent}. This is not reported by the
24261 @code{silent} attribute.
24264 @defvar Breakpoint.thread
24265 If the breakpoint is thread-specific, this attribute holds the thread
24266 id. If the breakpoint is not thread-specific, this attribute is
24267 @code{None}. This attribute is writable.
24270 @defvar Breakpoint.task
24271 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24272 id. If the breakpoint is not task-specific (or the underlying
24273 language is not Ada), this attribute is @code{None}. This attribute
24277 @defvar Breakpoint.ignore_count
24278 This attribute holds the ignore count for the breakpoint, an integer.
24279 This attribute is writable.
24282 @defvar Breakpoint.number
24283 This attribute holds the breakpoint's number --- the identifier used by
24284 the user to manipulate the breakpoint. This attribute is not writable.
24287 @defvar Breakpoint.type
24288 This attribute holds the breakpoint's type --- the identifier used to
24289 determine the actual breakpoint type or use-case. This attribute is not
24293 @defvar Breakpoint.visible
24294 This attribute tells whether the breakpoint is visible to the user
24295 when set, or when the @samp{info breakpoints} command is run. This
24296 attribute is not writable.
24299 The available types are represented by constants defined in the @code{gdb}
24303 @findex BP_BREAKPOINT
24304 @findex gdb.BP_BREAKPOINT
24305 @item gdb.BP_BREAKPOINT
24306 Normal code breakpoint.
24308 @findex BP_WATCHPOINT
24309 @findex gdb.BP_WATCHPOINT
24310 @item gdb.BP_WATCHPOINT
24311 Watchpoint breakpoint.
24313 @findex BP_HARDWARE_WATCHPOINT
24314 @findex gdb.BP_HARDWARE_WATCHPOINT
24315 @item gdb.BP_HARDWARE_WATCHPOINT
24316 Hardware assisted watchpoint.
24318 @findex BP_READ_WATCHPOINT
24319 @findex gdb.BP_READ_WATCHPOINT
24320 @item gdb.BP_READ_WATCHPOINT
24321 Hardware assisted read watchpoint.
24323 @findex BP_ACCESS_WATCHPOINT
24324 @findex gdb.BP_ACCESS_WATCHPOINT
24325 @item gdb.BP_ACCESS_WATCHPOINT
24326 Hardware assisted access watchpoint.
24329 @defvar Breakpoint.hit_count
24330 This attribute holds the hit count for the breakpoint, an integer.
24331 This attribute is writable, but currently it can only be set to zero.
24334 @defvar Breakpoint.location
24335 This attribute holds the location of the breakpoint, as specified by
24336 the user. It is a string. If the breakpoint does not have a location
24337 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24338 attribute is not writable.
24341 @defvar Breakpoint.expression
24342 This attribute holds a breakpoint expression, as specified by
24343 the user. It is a string. If the breakpoint does not have an
24344 expression (the breakpoint is not a watchpoint) the attribute's value
24345 is @code{None}. This attribute is not writable.
24348 @defvar Breakpoint.condition
24349 This attribute holds the condition of the breakpoint, as specified by
24350 the user. It is a string. If there is no condition, this attribute's
24351 value is @code{None}. This attribute is writable.
24354 @defvar Breakpoint.commands
24355 This attribute holds the commands attached to the breakpoint. If
24356 there are commands, this attribute's value is a string holding all the
24357 commands, separated by newlines. If there are no commands, this
24358 attribute is @code{None}. This attribute is not writable.
24361 @node Finish Breakpoints in Python
24362 @subsubsection Finish Breakpoints
24364 @cindex python finish breakpoints
24365 @tindex gdb.FinishBreakpoint
24367 A finish breakpoint is a temporary breakpoint set at the return address of
24368 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24369 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24370 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24371 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24372 Finish breakpoints are thread specific and must be create with the right
24375 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24376 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24377 object @var{frame}. If @var{frame} is not provided, this defaults to the
24378 newest frame. The optional @var{internal} argument allows the breakpoint to
24379 become invisible to the user. @xref{Breakpoints In Python}, for further
24380 details about this argument.
24383 @defun FinishBreakpoint.out_of_scope (self)
24384 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24385 @code{return} command, @dots{}), a function may not properly terminate, and
24386 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24387 situation, the @code{out_of_scope} callback will be triggered.
24389 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24393 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24395 print "normal finish"
24398 def out_of_scope ():
24399 print "abnormal finish"
24403 @defvar FinishBreakpoint.return_value
24404 When @value{GDBN} is stopped at a finish breakpoint and the frame
24405 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24406 attribute will contain a @code{gdb.Value} object corresponding to the return
24407 value of the function. The value will be @code{None} if the function return
24408 type is @code{void} or if the return value was not computable. This attribute
24412 @node Lazy Strings In Python
24413 @subsubsection Python representation of lazy strings.
24415 @cindex lazy strings in python
24416 @tindex gdb.LazyString
24418 A @dfn{lazy string} is a string whose contents is not retrieved or
24419 encoded until it is needed.
24421 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24422 @code{address} that points to a region of memory, an @code{encoding}
24423 that will be used to encode that region of memory, and a @code{length}
24424 to delimit the region of memory that represents the string. The
24425 difference between a @code{gdb.LazyString} and a string wrapped within
24426 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24427 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24428 retrieved and encoded during printing, while a @code{gdb.Value}
24429 wrapping a string is immediately retrieved and encoded on creation.
24431 A @code{gdb.LazyString} object has the following functions:
24433 @defun LazyString.value ()
24434 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24435 will point to the string in memory, but will lose all the delayed
24436 retrieval, encoding and handling that @value{GDBN} applies to a
24437 @code{gdb.LazyString}.
24440 @defvar LazyString.address
24441 This attribute holds the address of the string. This attribute is not
24445 @defvar LazyString.length
24446 This attribute holds the length of the string in characters. If the
24447 length is -1, then the string will be fetched and encoded up to the
24448 first null of appropriate width. This attribute is not writable.
24451 @defvar LazyString.encoding
24452 This attribute holds the encoding that will be applied to the string
24453 when the string is printed by @value{GDBN}. If the encoding is not
24454 set, or contains an empty string, then @value{GDBN} will select the
24455 most appropriate encoding when the string is printed. This attribute
24459 @defvar LazyString.type
24460 This attribute holds the type that is represented by the lazy string's
24461 type. For a lazy string this will always be a pointer type. To
24462 resolve this to the lazy string's character type, use the type's
24463 @code{target} method. @xref{Types In Python}. This attribute is not
24468 @subsection Auto-loading
24469 @cindex auto-loading, Python
24471 When a new object file is read (for example, due to the @code{file}
24472 command, or because the inferior has loaded a shared library),
24473 @value{GDBN} will look for Python support scripts in several ways:
24474 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24477 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24478 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24479 * Which flavor to choose?::
24482 The auto-loading feature is useful for supplying application-specific
24483 debugging commands and scripts.
24485 Auto-loading can be enabled or disabled,
24486 and the list of auto-loaded scripts can be printed.
24489 @kindex set auto-load-scripts
24490 @item set auto-load-scripts [yes|no]
24491 Enable or disable the auto-loading of Python scripts.
24493 @kindex show auto-load-scripts
24494 @item show auto-load-scripts
24495 Show whether auto-loading of Python scripts is enabled or disabled.
24497 @kindex info auto-load-scripts
24498 @cindex print list of auto-loaded scripts
24499 @item info auto-load-scripts [@var{regexp}]
24500 Print the list of all scripts that @value{GDBN} auto-loaded.
24502 Also printed is the list of scripts that were mentioned in
24503 the @code{.debug_gdb_scripts} section and were not found
24504 (@pxref{.debug_gdb_scripts section}).
24505 This is useful because their names are not printed when @value{GDBN}
24506 tries to load them and fails. There may be many of them, and printing
24507 an error message for each one is problematic.
24509 If @var{regexp} is supplied only scripts with matching names are printed.
24514 (gdb) info auto-load-scripts
24516 Yes py-section-script.py
24517 full name: /tmp/py-section-script.py
24518 Missing my-foo-pretty-printers.py
24522 When reading an auto-loaded file, @value{GDBN} sets the
24523 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24524 function (@pxref{Objfiles In Python}). This can be useful for
24525 registering objfile-specific pretty-printers.
24527 @node objfile-gdb.py file
24528 @subsubsection The @file{@var{objfile}-gdb.py} file
24529 @cindex @file{@var{objfile}-gdb.py}
24531 When a new object file is read, @value{GDBN} looks for
24532 a file named @file{@var{objfile}-gdb.py},
24533 where @var{objfile} is the object file's real name, formed by ensuring
24534 that the file name is absolute, following all symlinks, and resolving
24535 @code{.} and @code{..} components. If this file exists and is
24536 readable, @value{GDBN} will evaluate it as a Python script.
24538 If this file does not exist, and if the parameter
24539 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24540 then @value{GDBN} will look for @var{real-name} in all of the
24541 directories mentioned in the value of @code{debug-file-directory}.
24543 Finally, if this file does not exist, then @value{GDBN} will look for
24544 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24545 @var{data-directory} is @value{GDBN}'s data directory (available via
24546 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24547 is the object file's real name, as described above.
24549 @value{GDBN} does not track which files it has already auto-loaded this way.
24550 @value{GDBN} will load the associated script every time the corresponding
24551 @var{objfile} is opened.
24552 So your @file{-gdb.py} file should be careful to avoid errors if it
24553 is evaluated more than once.
24555 @node .debug_gdb_scripts section
24556 @subsubsection The @code{.debug_gdb_scripts} section
24557 @cindex @code{.debug_gdb_scripts} section
24559 For systems using file formats like ELF and COFF,
24560 when @value{GDBN} loads a new object file
24561 it will look for a special section named @samp{.debug_gdb_scripts}.
24562 If this section exists, its contents is a list of names of scripts to load.
24564 @value{GDBN} will look for each specified script file first in the
24565 current directory and then along the source search path
24566 (@pxref{Source Path, ,Specifying Source Directories}),
24567 except that @file{$cdir} is not searched, since the compilation
24568 directory is not relevant to scripts.
24570 Entries can be placed in section @code{.debug_gdb_scripts} with,
24571 for example, this GCC macro:
24574 /* Note: The "MS" section flags are to remove duplicates. */
24575 #define DEFINE_GDB_SCRIPT(script_name) \
24577 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24579 .asciz \"" script_name "\"\n\
24585 Then one can reference the macro in a header or source file like this:
24588 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24591 The script name may include directories if desired.
24593 If the macro is put in a header, any application or library
24594 using this header will get a reference to the specified script.
24596 @node Which flavor to choose?
24597 @subsubsection Which flavor to choose?
24599 Given the multiple ways of auto-loading Python scripts, it might not always
24600 be clear which one to choose. This section provides some guidance.
24602 Benefits of the @file{-gdb.py} way:
24606 Can be used with file formats that don't support multiple sections.
24609 Ease of finding scripts for public libraries.
24611 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24612 in the source search path.
24613 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24614 isn't a source directory in which to find the script.
24617 Doesn't require source code additions.
24620 Benefits of the @code{.debug_gdb_scripts} way:
24624 Works with static linking.
24626 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24627 trigger their loading. When an application is statically linked the only
24628 objfile available is the executable, and it is cumbersome to attach all the
24629 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24632 Works with classes that are entirely inlined.
24634 Some classes can be entirely inlined, and thus there may not be an associated
24635 shared library to attach a @file{-gdb.py} script to.
24638 Scripts needn't be copied out of the source tree.
24640 In some circumstances, apps can be built out of large collections of internal
24641 libraries, and the build infrastructure necessary to install the
24642 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24643 cumbersome. It may be easier to specify the scripts in the
24644 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24645 top of the source tree to the source search path.
24648 @node Python modules
24649 @subsection Python modules
24650 @cindex python modules
24652 @value{GDBN} comes with several modules to assist writing Python code.
24655 * gdb.printing:: Building and registering pretty-printers.
24656 * gdb.types:: Utilities for working with types.
24657 * gdb.prompt:: Utilities for prompt value substitution.
24661 @subsubsection gdb.printing
24662 @cindex gdb.printing
24664 This module provides a collection of utilities for working with
24668 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24669 This class specifies the API that makes @samp{info pretty-printer},
24670 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24671 Pretty-printers should generally inherit from this class.
24673 @item SubPrettyPrinter (@var{name})
24674 For printers that handle multiple types, this class specifies the
24675 corresponding API for the subprinters.
24677 @item RegexpCollectionPrettyPrinter (@var{name})
24678 Utility class for handling multiple printers, all recognized via
24679 regular expressions.
24680 @xref{Writing a Pretty-Printer}, for an example.
24682 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24683 Register @var{printer} with the pretty-printer list of @var{obj}.
24684 If @var{replace} is @code{True} then any existing copy of the printer
24685 is replaced. Otherwise a @code{RuntimeError} exception is raised
24686 if a printer with the same name already exists.
24690 @subsubsection gdb.types
24693 This module provides a collection of utilities for working with
24694 @code{gdb.Types} objects.
24697 @item get_basic_type (@var{type})
24698 Return @var{type} with const and volatile qualifiers stripped,
24699 and with typedefs and C@t{++} references converted to the underlying type.
24704 typedef const int const_int;
24706 const_int& foo_ref (foo);
24707 int main () @{ return 0; @}
24714 (gdb) python import gdb.types
24715 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24716 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24720 @item has_field (@var{type}, @var{field})
24721 Return @code{True} if @var{type}, assumed to be a type with fields
24722 (e.g., a structure or union), has field @var{field}.
24724 @item make_enum_dict (@var{enum_type})
24725 Return a Python @code{dictionary} type produced from @var{enum_type}.
24727 @item deep_items (@var{type})
24728 Returns a Python iterator similar to the standard
24729 @code{gdb.Type.iteritems} method, except that the iterator returned
24730 by @code{deep_items} will recursively traverse anonymous struct or
24731 union fields. For example:
24745 Then in @value{GDBN}:
24747 (@value{GDBP}) python import gdb.types
24748 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24749 (@value{GDBP}) python print struct_a.keys ()
24751 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24752 @{['a', 'b0', 'b1']@}
24758 @subsubsection gdb.prompt
24761 This module provides a method for prompt value-substitution.
24764 @item substitute_prompt (@var{string})
24765 Return @var{string} with escape sequences substituted by values. Some
24766 escape sequences take arguments. You can specify arguments inside
24767 ``@{@}'' immediately following the escape sequence.
24769 The escape sequences you can pass to this function are:
24773 Substitute a backslash.
24775 Substitute an ESC character.
24777 Substitute the selected frame; an argument names a frame parameter.
24779 Substitute a newline.
24781 Substitute a parameter's value; the argument names the parameter.
24783 Substitute a carriage return.
24785 Substitute the selected thread; an argument names a thread parameter.
24787 Substitute the version of GDB.
24789 Substitute the current working directory.
24791 Begin a sequence of non-printing characters. These sequences are
24792 typically used with the ESC character, and are not counted in the string
24793 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24794 blue-colored ``(gdb)'' prompt where the length is five.
24796 End a sequence of non-printing characters.
24802 substitute_prompt (``frame: \f,
24803 print arguments: \p@{print frame-arguments@}'')
24806 @exdent will return the string:
24809 "frame: main, print arguments: scalars"
24814 @section Creating new spellings of existing commands
24815 @cindex aliases for commands
24817 It is often useful to define alternate spellings of existing commands.
24818 For example, if a new @value{GDBN} command defined in Python has
24819 a long name to type, it is handy to have an abbreviated version of it
24820 that involves less typing.
24822 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24823 of the @samp{step} command even though it is otherwise an ambiguous
24824 abbreviation of other commands like @samp{set} and @samp{show}.
24826 Aliases are also used to provide shortened or more common versions
24827 of multi-word commands. For example, @value{GDBN} provides the
24828 @samp{tty} alias of the @samp{set inferior-tty} command.
24830 You can define a new alias with the @samp{alias} command.
24835 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24839 @var{ALIAS} specifies the name of the new alias.
24840 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24843 @var{COMMAND} specifies the name of an existing command
24844 that is being aliased.
24846 The @samp{-a} option specifies that the new alias is an abbreviation
24847 of the command. Abbreviations are not shown in command
24848 lists displayed by the @samp{help} command.
24850 The @samp{--} option specifies the end of options,
24851 and is useful when @var{ALIAS} begins with a dash.
24853 Here is a simple example showing how to make an abbreviation
24854 of a command so that there is less to type.
24855 Suppose you were tired of typing @samp{disas}, the current
24856 shortest unambiguous abbreviation of the @samp{disassemble} command
24857 and you wanted an even shorter version named @samp{di}.
24858 The following will accomplish this.
24861 (gdb) alias -a di = disas
24864 Note that aliases are different from user-defined commands.
24865 With a user-defined command, you also need to write documentation
24866 for it with the @samp{document} command.
24867 An alias automatically picks up the documentation of the existing command.
24869 Here is an example where we make @samp{elms} an abbreviation of
24870 @samp{elements} in the @samp{set print elements} command.
24871 This is to show that you can make an abbreviation of any part
24875 (gdb) alias -a set print elms = set print elements
24876 (gdb) alias -a show print elms = show print elements
24877 (gdb) set p elms 20
24879 Limit on string chars or array elements to print is 200.
24882 Note that if you are defining an alias of a @samp{set} command,
24883 and you want to have an alias for the corresponding @samp{show}
24884 command, then you need to define the latter separately.
24886 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24887 @var{ALIAS}, just as they are normally.
24890 (gdb) alias -a set pr elms = set p ele
24893 Finally, here is an example showing the creation of a one word
24894 alias for a more complex command.
24895 This creates alias @samp{spe} of the command @samp{set print elements}.
24898 (gdb) alias spe = set print elements
24903 @chapter Command Interpreters
24904 @cindex command interpreters
24906 @value{GDBN} supports multiple command interpreters, and some command
24907 infrastructure to allow users or user interface writers to switch
24908 between interpreters or run commands in other interpreters.
24910 @value{GDBN} currently supports two command interpreters, the console
24911 interpreter (sometimes called the command-line interpreter or @sc{cli})
24912 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24913 describes both of these interfaces in great detail.
24915 By default, @value{GDBN} will start with the console interpreter.
24916 However, the user may choose to start @value{GDBN} with another
24917 interpreter by specifying the @option{-i} or @option{--interpreter}
24918 startup options. Defined interpreters include:
24922 @cindex console interpreter
24923 The traditional console or command-line interpreter. This is the most often
24924 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24925 @value{GDBN} will use this interpreter.
24928 @cindex mi interpreter
24929 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24930 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24931 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24935 @cindex mi2 interpreter
24936 The current @sc{gdb/mi} interface.
24939 @cindex mi1 interpreter
24940 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24944 @cindex invoke another interpreter
24945 The interpreter being used by @value{GDBN} may not be dynamically
24946 switched at runtime. Although possible, this could lead to a very
24947 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24948 enters the command "interpreter-set console" in a console view,
24949 @value{GDBN} would switch to using the console interpreter, rendering
24950 the IDE inoperable!
24952 @kindex interpreter-exec
24953 Although you may only choose a single interpreter at startup, you may execute
24954 commands in any interpreter from the current interpreter using the appropriate
24955 command. If you are running the console interpreter, simply use the
24956 @code{interpreter-exec} command:
24959 interpreter-exec mi "-data-list-register-names"
24962 @sc{gdb/mi} has a similar command, although it is only available in versions of
24963 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24966 @chapter @value{GDBN} Text User Interface
24968 @cindex Text User Interface
24971 * TUI Overview:: TUI overview
24972 * TUI Keys:: TUI key bindings
24973 * TUI Single Key Mode:: TUI single key mode
24974 * TUI Commands:: TUI-specific commands
24975 * TUI Configuration:: TUI configuration variables
24978 The @value{GDBN} Text User Interface (TUI) is a terminal
24979 interface which uses the @code{curses} library to show the source
24980 file, the assembly output, the program registers and @value{GDBN}
24981 commands in separate text windows. The TUI mode is supported only
24982 on platforms where a suitable version of the @code{curses} library
24985 The TUI mode is enabled by default when you invoke @value{GDBN} as
24986 @samp{@value{GDBP} -tui}.
24987 You can also switch in and out of TUI mode while @value{GDBN} runs by
24988 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24989 @xref{TUI Keys, ,TUI Key Bindings}.
24992 @section TUI Overview
24994 In TUI mode, @value{GDBN} can display several text windows:
24998 This window is the @value{GDBN} command window with the @value{GDBN}
24999 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25000 managed using readline.
25003 The source window shows the source file of the program. The current
25004 line and active breakpoints are displayed in this window.
25007 The assembly window shows the disassembly output of the program.
25010 This window shows the processor registers. Registers are highlighted
25011 when their values change.
25014 The source and assembly windows show the current program position
25015 by highlighting the current line and marking it with a @samp{>} marker.
25016 Breakpoints are indicated with two markers. The first marker
25017 indicates the breakpoint type:
25021 Breakpoint which was hit at least once.
25024 Breakpoint which was never hit.
25027 Hardware breakpoint which was hit at least once.
25030 Hardware breakpoint which was never hit.
25033 The second marker indicates whether the breakpoint is enabled or not:
25037 Breakpoint is enabled.
25040 Breakpoint is disabled.
25043 The source, assembly and register windows are updated when the current
25044 thread changes, when the frame changes, or when the program counter
25047 These windows are not all visible at the same time. The command
25048 window is always visible. The others can be arranged in several
25059 source and assembly,
25062 source and registers, or
25065 assembly and registers.
25068 A status line above the command window shows the following information:
25072 Indicates the current @value{GDBN} target.
25073 (@pxref{Targets, ,Specifying a Debugging Target}).
25076 Gives the current process or thread number.
25077 When no process is being debugged, this field is set to @code{No process}.
25080 Gives the current function name for the selected frame.
25081 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25082 When there is no symbol corresponding to the current program counter,
25083 the string @code{??} is displayed.
25086 Indicates the current line number for the selected frame.
25087 When the current line number is not known, the string @code{??} is displayed.
25090 Indicates the current program counter address.
25094 @section TUI Key Bindings
25095 @cindex TUI key bindings
25097 The TUI installs several key bindings in the readline keymaps
25098 @ifset SYSTEM_READLINE
25099 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25101 @ifclear SYSTEM_READLINE
25102 (@pxref{Command Line Editing}).
25104 The following key bindings are installed for both TUI mode and the
25105 @value{GDBN} standard mode.
25114 Enter or leave the TUI mode. When leaving the TUI mode,
25115 the curses window management stops and @value{GDBN} operates using
25116 its standard mode, writing on the terminal directly. When reentering
25117 the TUI mode, control is given back to the curses windows.
25118 The screen is then refreshed.
25122 Use a TUI layout with only one window. The layout will
25123 either be @samp{source} or @samp{assembly}. When the TUI mode
25124 is not active, it will switch to the TUI mode.
25126 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25130 Use a TUI layout with at least two windows. When the current
25131 layout already has two windows, the next layout with two windows is used.
25132 When a new layout is chosen, one window will always be common to the
25133 previous layout and the new one.
25135 Think of it as the Emacs @kbd{C-x 2} binding.
25139 Change the active window. The TUI associates several key bindings
25140 (like scrolling and arrow keys) with the active window. This command
25141 gives the focus to the next TUI window.
25143 Think of it as the Emacs @kbd{C-x o} binding.
25147 Switch in and out of the TUI SingleKey mode that binds single
25148 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25151 The following key bindings only work in the TUI mode:
25156 Scroll the active window one page up.
25160 Scroll the active window one page down.
25164 Scroll the active window one line up.
25168 Scroll the active window one line down.
25172 Scroll the active window one column left.
25176 Scroll the active window one column right.
25180 Refresh the screen.
25183 Because the arrow keys scroll the active window in the TUI mode, they
25184 are not available for their normal use by readline unless the command
25185 window has the focus. When another window is active, you must use
25186 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25187 and @kbd{C-f} to control the command window.
25189 @node TUI Single Key Mode
25190 @section TUI Single Key Mode
25191 @cindex TUI single key mode
25193 The TUI also provides a @dfn{SingleKey} mode, which binds several
25194 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25195 switch into this mode, where the following key bindings are used:
25198 @kindex c @r{(SingleKey TUI key)}
25202 @kindex d @r{(SingleKey TUI key)}
25206 @kindex f @r{(SingleKey TUI key)}
25210 @kindex n @r{(SingleKey TUI key)}
25214 @kindex q @r{(SingleKey TUI key)}
25216 exit the SingleKey mode.
25218 @kindex r @r{(SingleKey TUI key)}
25222 @kindex s @r{(SingleKey TUI key)}
25226 @kindex u @r{(SingleKey TUI key)}
25230 @kindex v @r{(SingleKey TUI key)}
25234 @kindex w @r{(SingleKey TUI key)}
25239 Other keys temporarily switch to the @value{GDBN} command prompt.
25240 The key that was pressed is inserted in the editing buffer so that
25241 it is possible to type most @value{GDBN} commands without interaction
25242 with the TUI SingleKey mode. Once the command is entered the TUI
25243 SingleKey mode is restored. The only way to permanently leave
25244 this mode is by typing @kbd{q} or @kbd{C-x s}.
25248 @section TUI-specific Commands
25249 @cindex TUI commands
25251 The TUI has specific commands to control the text windows.
25252 These commands are always available, even when @value{GDBN} is not in
25253 the TUI mode. When @value{GDBN} is in the standard mode, most
25254 of these commands will automatically switch to the TUI mode.
25256 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25257 terminal, or @value{GDBN} has been started with the machine interface
25258 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25259 these commands will fail with an error, because it would not be
25260 possible or desirable to enable curses window management.
25265 List and give the size of all displayed windows.
25269 Display the next layout.
25272 Display the previous layout.
25275 Display the source window only.
25278 Display the assembly window only.
25281 Display the source and assembly window.
25284 Display the register window together with the source or assembly window.
25288 Make the next window active for scrolling.
25291 Make the previous window active for scrolling.
25294 Make the source window active for scrolling.
25297 Make the assembly window active for scrolling.
25300 Make the register window active for scrolling.
25303 Make the command window active for scrolling.
25307 Refresh the screen. This is similar to typing @kbd{C-L}.
25309 @item tui reg float
25311 Show the floating point registers in the register window.
25313 @item tui reg general
25314 Show the general registers in the register window.
25317 Show the next register group. The list of register groups as well as
25318 their order is target specific. The predefined register groups are the
25319 following: @code{general}, @code{float}, @code{system}, @code{vector},
25320 @code{all}, @code{save}, @code{restore}.
25322 @item tui reg system
25323 Show the system registers in the register window.
25327 Update the source window and the current execution point.
25329 @item winheight @var{name} +@var{count}
25330 @itemx winheight @var{name} -@var{count}
25332 Change the height of the window @var{name} by @var{count}
25333 lines. Positive counts increase the height, while negative counts
25336 @item tabset @var{nchars}
25338 Set the width of tab stops to be @var{nchars} characters.
25341 @node TUI Configuration
25342 @section TUI Configuration Variables
25343 @cindex TUI configuration variables
25345 Several configuration variables control the appearance of TUI windows.
25348 @item set tui border-kind @var{kind}
25349 @kindex set tui border-kind
25350 Select the border appearance for the source, assembly and register windows.
25351 The possible values are the following:
25354 Use a space character to draw the border.
25357 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25360 Use the Alternate Character Set to draw the border. The border is
25361 drawn using character line graphics if the terminal supports them.
25364 @item set tui border-mode @var{mode}
25365 @kindex set tui border-mode
25366 @itemx set tui active-border-mode @var{mode}
25367 @kindex set tui active-border-mode
25368 Select the display attributes for the borders of the inactive windows
25369 or the active window. The @var{mode} can be one of the following:
25372 Use normal attributes to display the border.
25378 Use reverse video mode.
25381 Use half bright mode.
25383 @item half-standout
25384 Use half bright and standout mode.
25387 Use extra bright or bold mode.
25389 @item bold-standout
25390 Use extra bright or bold and standout mode.
25395 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25398 @cindex @sc{gnu} Emacs
25399 A special interface allows you to use @sc{gnu} Emacs to view (and
25400 edit) the source files for the program you are debugging with
25403 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25404 executable file you want to debug as an argument. This command starts
25405 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25406 created Emacs buffer.
25407 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25409 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25414 All ``terminal'' input and output goes through an Emacs buffer, called
25417 This applies both to @value{GDBN} commands and their output, and to the input
25418 and output done by the program you are debugging.
25420 This is useful because it means that you can copy the text of previous
25421 commands and input them again; you can even use parts of the output
25424 All the facilities of Emacs' Shell mode are available for interacting
25425 with your program. In particular, you can send signals the usual
25426 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25430 @value{GDBN} displays source code through Emacs.
25432 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25433 source file for that frame and puts an arrow (@samp{=>}) at the
25434 left margin of the current line. Emacs uses a separate buffer for
25435 source display, and splits the screen to show both your @value{GDBN} session
25438 Explicit @value{GDBN} @code{list} or search commands still produce output as
25439 usual, but you probably have no reason to use them from Emacs.
25442 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25443 a graphical mode, enabled by default, which provides further buffers
25444 that can control the execution and describe the state of your program.
25445 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25447 If you specify an absolute file name when prompted for the @kbd{M-x
25448 gdb} argument, then Emacs sets your current working directory to where
25449 your program resides. If you only specify the file name, then Emacs
25450 sets your current working directory to the directory associated
25451 with the previous buffer. In this case, @value{GDBN} may find your
25452 program by searching your environment's @code{PATH} variable, but on
25453 some operating systems it might not find the source. So, although the
25454 @value{GDBN} input and output session proceeds normally, the auxiliary
25455 buffer does not display the current source and line of execution.
25457 The initial working directory of @value{GDBN} is printed on the top
25458 line of the GUD buffer and this serves as a default for the commands
25459 that specify files for @value{GDBN} to operate on. @xref{Files,
25460 ,Commands to Specify Files}.
25462 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25463 need to call @value{GDBN} by a different name (for example, if you
25464 keep several configurations around, with different names) you can
25465 customize the Emacs variable @code{gud-gdb-command-name} to run the
25468 In the GUD buffer, you can use these special Emacs commands in
25469 addition to the standard Shell mode commands:
25473 Describe the features of Emacs' GUD Mode.
25476 Execute to another source line, like the @value{GDBN} @code{step} command; also
25477 update the display window to show the current file and location.
25480 Execute to next source line in this function, skipping all function
25481 calls, like the @value{GDBN} @code{next} command. Then update the display window
25482 to show the current file and location.
25485 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25486 display window accordingly.
25489 Execute until exit from the selected stack frame, like the @value{GDBN}
25490 @code{finish} command.
25493 Continue execution of your program, like the @value{GDBN} @code{continue}
25497 Go up the number of frames indicated by the numeric argument
25498 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25499 like the @value{GDBN} @code{up} command.
25502 Go down the number of frames indicated by the numeric argument, like the
25503 @value{GDBN} @code{down} command.
25506 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25507 tells @value{GDBN} to set a breakpoint on the source line point is on.
25509 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25510 separate frame which shows a backtrace when the GUD buffer is current.
25511 Move point to any frame in the stack and type @key{RET} to make it
25512 become the current frame and display the associated source in the
25513 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25514 selected frame become the current one. In graphical mode, the
25515 speedbar displays watch expressions.
25517 If you accidentally delete the source-display buffer, an easy way to get
25518 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25519 request a frame display; when you run under Emacs, this recreates
25520 the source buffer if necessary to show you the context of the current
25523 The source files displayed in Emacs are in ordinary Emacs buffers
25524 which are visiting the source files in the usual way. You can edit
25525 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25526 communicates with Emacs in terms of line numbers. If you add or
25527 delete lines from the text, the line numbers that @value{GDBN} knows cease
25528 to correspond properly with the code.
25530 A more detailed description of Emacs' interaction with @value{GDBN} is
25531 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25534 @c The following dropped because Epoch is nonstandard. Reactivate
25535 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25537 @kindex Emacs Epoch environment
25541 Version 18 of @sc{gnu} Emacs has a built-in window system
25542 called the @code{epoch}
25543 environment. Users of this environment can use a new command,
25544 @code{inspect} which performs identically to @code{print} except that
25545 each value is printed in its own window.
25550 @chapter The @sc{gdb/mi} Interface
25552 @unnumberedsec Function and Purpose
25554 @cindex @sc{gdb/mi}, its purpose
25555 @sc{gdb/mi} is a line based machine oriented text interface to
25556 @value{GDBN} and is activated by specifying using the
25557 @option{--interpreter} command line option (@pxref{Mode Options}). It
25558 is specifically intended to support the development of systems which
25559 use the debugger as just one small component of a larger system.
25561 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25562 in the form of a reference manual.
25564 Note that @sc{gdb/mi} is still under construction, so some of the
25565 features described below are incomplete and subject to change
25566 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25568 @unnumberedsec Notation and Terminology
25570 @cindex notational conventions, for @sc{gdb/mi}
25571 This chapter uses the following notation:
25575 @code{|} separates two alternatives.
25578 @code{[ @var{something} ]} indicates that @var{something} is optional:
25579 it may or may not be given.
25582 @code{( @var{group} )*} means that @var{group} inside the parentheses
25583 may repeat zero or more times.
25586 @code{( @var{group} )+} means that @var{group} inside the parentheses
25587 may repeat one or more times.
25590 @code{"@var{string}"} means a literal @var{string}.
25594 @heading Dependencies
25598 * GDB/MI General Design::
25599 * GDB/MI Command Syntax::
25600 * GDB/MI Compatibility with CLI::
25601 * GDB/MI Development and Front Ends::
25602 * GDB/MI Output Records::
25603 * GDB/MI Simple Examples::
25604 * GDB/MI Command Description Format::
25605 * GDB/MI Breakpoint Commands::
25606 * GDB/MI Program Context::
25607 * GDB/MI Thread Commands::
25608 * GDB/MI Ada Tasking Commands::
25609 * GDB/MI Program Execution::
25610 * GDB/MI Stack Manipulation::
25611 * GDB/MI Variable Objects::
25612 * GDB/MI Data Manipulation::
25613 * GDB/MI Tracepoint Commands::
25614 * GDB/MI Symbol Query::
25615 * GDB/MI File Commands::
25617 * GDB/MI Kod Commands::
25618 * GDB/MI Memory Overlay Commands::
25619 * GDB/MI Signal Handling Commands::
25621 * GDB/MI Target Manipulation::
25622 * GDB/MI File Transfer Commands::
25623 * GDB/MI Miscellaneous Commands::
25626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25627 @node GDB/MI General Design
25628 @section @sc{gdb/mi} General Design
25629 @cindex GDB/MI General Design
25631 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25632 parts---commands sent to @value{GDBN}, responses to those commands
25633 and notifications. Each command results in exactly one response,
25634 indicating either successful completion of the command, or an error.
25635 For the commands that do not resume the target, the response contains the
25636 requested information. For the commands that resume the target, the
25637 response only indicates whether the target was successfully resumed.
25638 Notifications is the mechanism for reporting changes in the state of the
25639 target, or in @value{GDBN} state, that cannot conveniently be associated with
25640 a command and reported as part of that command response.
25642 The important examples of notifications are:
25646 Exec notifications. These are used to report changes in
25647 target state---when a target is resumed, or stopped. It would not
25648 be feasible to include this information in response of resuming
25649 commands, because one resume commands can result in multiple events in
25650 different threads. Also, quite some time may pass before any event
25651 happens in the target, while a frontend needs to know whether the resuming
25652 command itself was successfully executed.
25655 Console output, and status notifications. Console output
25656 notifications are used to report output of CLI commands, as well as
25657 diagnostics for other commands. Status notifications are used to
25658 report the progress of a long-running operation. Naturally, including
25659 this information in command response would mean no output is produced
25660 until the command is finished, which is undesirable.
25663 General notifications. Commands may have various side effects on
25664 the @value{GDBN} or target state beyond their official purpose. For example,
25665 a command may change the selected thread. Although such changes can
25666 be included in command response, using notification allows for more
25667 orthogonal frontend design.
25671 There's no guarantee that whenever an MI command reports an error,
25672 @value{GDBN} or the target are in any specific state, and especially,
25673 the state is not reverted to the state before the MI command was
25674 processed. Therefore, whenever an MI command results in an error,
25675 we recommend that the frontend refreshes all the information shown in
25676 the user interface.
25680 * Context management::
25681 * Asynchronous and non-stop modes::
25685 @node Context management
25686 @subsection Context management
25688 In most cases when @value{GDBN} accesses the target, this access is
25689 done in context of a specific thread and frame (@pxref{Frames}).
25690 Often, even when accessing global data, the target requires that a thread
25691 be specified. The CLI interface maintains the selected thread and frame,
25692 and supplies them to target on each command. This is convenient,
25693 because a command line user would not want to specify that information
25694 explicitly on each command, and because user interacts with
25695 @value{GDBN} via a single terminal, so no confusion is possible as
25696 to what thread and frame are the current ones.
25698 In the case of MI, the concept of selected thread and frame is less
25699 useful. First, a frontend can easily remember this information
25700 itself. Second, a graphical frontend can have more than one window,
25701 each one used for debugging a different thread, and the frontend might
25702 want to access additional threads for internal purposes. This
25703 increases the risk that by relying on implicitly selected thread, the
25704 frontend may be operating on a wrong one. Therefore, each MI command
25705 should explicitly specify which thread and frame to operate on. To
25706 make it possible, each MI command accepts the @samp{--thread} and
25707 @samp{--frame} options, the value to each is @value{GDBN} identifier
25708 for thread and frame to operate on.
25710 Usually, each top-level window in a frontend allows the user to select
25711 a thread and a frame, and remembers the user selection for further
25712 operations. However, in some cases @value{GDBN} may suggest that the
25713 current thread be changed. For example, when stopping on a breakpoint
25714 it is reasonable to switch to the thread where breakpoint is hit. For
25715 another example, if the user issues the CLI @samp{thread} command via
25716 the frontend, it is desirable to change the frontend's selected thread to the
25717 one specified by user. @value{GDBN} communicates the suggestion to
25718 change current thread using the @samp{=thread-selected} notification.
25719 No such notification is available for the selected frame at the moment.
25721 Note that historically, MI shares the selected thread with CLI, so
25722 frontends used the @code{-thread-select} to execute commands in the
25723 right context. However, getting this to work right is cumbersome. The
25724 simplest way is for frontend to emit @code{-thread-select} command
25725 before every command. This doubles the number of commands that need
25726 to be sent. The alternative approach is to suppress @code{-thread-select}
25727 if the selected thread in @value{GDBN} is supposed to be identical to the
25728 thread the frontend wants to operate on. However, getting this
25729 optimization right can be tricky. In particular, if the frontend
25730 sends several commands to @value{GDBN}, and one of the commands changes the
25731 selected thread, then the behaviour of subsequent commands will
25732 change. So, a frontend should either wait for response from such
25733 problematic commands, or explicitly add @code{-thread-select} for
25734 all subsequent commands. No frontend is known to do this exactly
25735 right, so it is suggested to just always pass the @samp{--thread} and
25736 @samp{--frame} options.
25738 @node Asynchronous and non-stop modes
25739 @subsection Asynchronous command execution and non-stop mode
25741 On some targets, @value{GDBN} is capable of processing MI commands
25742 even while the target is running. This is called @dfn{asynchronous
25743 command execution} (@pxref{Background Execution}). The frontend may
25744 specify a preferrence for asynchronous execution using the
25745 @code{-gdb-set target-async 1} command, which should be emitted before
25746 either running the executable or attaching to the target. After the
25747 frontend has started the executable or attached to the target, it can
25748 find if asynchronous execution is enabled using the
25749 @code{-list-target-features} command.
25751 Even if @value{GDBN} can accept a command while target is running,
25752 many commands that access the target do not work when the target is
25753 running. Therefore, asynchronous command execution is most useful
25754 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25755 it is possible to examine the state of one thread, while other threads
25758 When a given thread is running, MI commands that try to access the
25759 target in the context of that thread may not work, or may work only on
25760 some targets. In particular, commands that try to operate on thread's
25761 stack will not work, on any target. Commands that read memory, or
25762 modify breakpoints, may work or not work, depending on the target. Note
25763 that even commands that operate on global state, such as @code{print},
25764 @code{set}, and breakpoint commands, still access the target in the
25765 context of a specific thread, so frontend should try to find a
25766 stopped thread and perform the operation on that thread (using the
25767 @samp{--thread} option).
25769 Which commands will work in the context of a running thread is
25770 highly target dependent. However, the two commands
25771 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25772 to find the state of a thread, will always work.
25774 @node Thread groups
25775 @subsection Thread groups
25776 @value{GDBN} may be used to debug several processes at the same time.
25777 On some platfroms, @value{GDBN} may support debugging of several
25778 hardware systems, each one having several cores with several different
25779 processes running on each core. This section describes the MI
25780 mechanism to support such debugging scenarios.
25782 The key observation is that regardless of the structure of the
25783 target, MI can have a global list of threads, because most commands that
25784 accept the @samp{--thread} option do not need to know what process that
25785 thread belongs to. Therefore, it is not necessary to introduce
25786 neither additional @samp{--process} option, nor an notion of the
25787 current process in the MI interface. The only strictly new feature
25788 that is required is the ability to find how the threads are grouped
25791 To allow the user to discover such grouping, and to support arbitrary
25792 hierarchy of machines/cores/processes, MI introduces the concept of a
25793 @dfn{thread group}. Thread group is a collection of threads and other
25794 thread groups. A thread group always has a string identifier, a type,
25795 and may have additional attributes specific to the type. A new
25796 command, @code{-list-thread-groups}, returns the list of top-level
25797 thread groups, which correspond to processes that @value{GDBN} is
25798 debugging at the moment. By passing an identifier of a thread group
25799 to the @code{-list-thread-groups} command, it is possible to obtain
25800 the members of specific thread group.
25802 To allow the user to easily discover processes, and other objects, he
25803 wishes to debug, a concept of @dfn{available thread group} is
25804 introduced. Available thread group is an thread group that
25805 @value{GDBN} is not debugging, but that can be attached to, using the
25806 @code{-target-attach} command. The list of available top-level thread
25807 groups can be obtained using @samp{-list-thread-groups --available}.
25808 In general, the content of a thread group may be only retrieved only
25809 after attaching to that thread group.
25811 Thread groups are related to inferiors (@pxref{Inferiors and
25812 Programs}). Each inferior corresponds to a thread group of a special
25813 type @samp{process}, and some additional operations are permitted on
25814 such thread groups.
25816 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25817 @node GDB/MI Command Syntax
25818 @section @sc{gdb/mi} Command Syntax
25821 * GDB/MI Input Syntax::
25822 * GDB/MI Output Syntax::
25825 @node GDB/MI Input Syntax
25826 @subsection @sc{gdb/mi} Input Syntax
25828 @cindex input syntax for @sc{gdb/mi}
25829 @cindex @sc{gdb/mi}, input syntax
25831 @item @var{command} @expansion{}
25832 @code{@var{cli-command} | @var{mi-command}}
25834 @item @var{cli-command} @expansion{}
25835 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25836 @var{cli-command} is any existing @value{GDBN} CLI command.
25838 @item @var{mi-command} @expansion{}
25839 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25840 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25842 @item @var{token} @expansion{}
25843 "any sequence of digits"
25845 @item @var{option} @expansion{}
25846 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25848 @item @var{parameter} @expansion{}
25849 @code{@var{non-blank-sequence} | @var{c-string}}
25851 @item @var{operation} @expansion{}
25852 @emph{any of the operations described in this chapter}
25854 @item @var{non-blank-sequence} @expansion{}
25855 @emph{anything, provided it doesn't contain special characters such as
25856 "-", @var{nl}, """ and of course " "}
25858 @item @var{c-string} @expansion{}
25859 @code{""" @var{seven-bit-iso-c-string-content} """}
25861 @item @var{nl} @expansion{}
25870 The CLI commands are still handled by the @sc{mi} interpreter; their
25871 output is described below.
25874 The @code{@var{token}}, when present, is passed back when the command
25878 Some @sc{mi} commands accept optional arguments as part of the parameter
25879 list. Each option is identified by a leading @samp{-} (dash) and may be
25880 followed by an optional argument parameter. Options occur first in the
25881 parameter list and can be delimited from normal parameters using
25882 @samp{--} (this is useful when some parameters begin with a dash).
25889 We want easy access to the existing CLI syntax (for debugging).
25892 We want it to be easy to spot a @sc{mi} operation.
25895 @node GDB/MI Output Syntax
25896 @subsection @sc{gdb/mi} Output Syntax
25898 @cindex output syntax of @sc{gdb/mi}
25899 @cindex @sc{gdb/mi}, output syntax
25900 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25901 followed, optionally, by a single result record. This result record
25902 is for the most recent command. The sequence of output records is
25903 terminated by @samp{(gdb)}.
25905 If an input command was prefixed with a @code{@var{token}} then the
25906 corresponding output for that command will also be prefixed by that same
25910 @item @var{output} @expansion{}
25911 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25913 @item @var{result-record} @expansion{}
25914 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25916 @item @var{out-of-band-record} @expansion{}
25917 @code{@var{async-record} | @var{stream-record}}
25919 @item @var{async-record} @expansion{}
25920 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25922 @item @var{exec-async-output} @expansion{}
25923 @code{[ @var{token} ] "*" @var{async-output}}
25925 @item @var{status-async-output} @expansion{}
25926 @code{[ @var{token} ] "+" @var{async-output}}
25928 @item @var{notify-async-output} @expansion{}
25929 @code{[ @var{token} ] "=" @var{async-output}}
25931 @item @var{async-output} @expansion{}
25932 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25934 @item @var{result-class} @expansion{}
25935 @code{"done" | "running" | "connected" | "error" | "exit"}
25937 @item @var{async-class} @expansion{}
25938 @code{"stopped" | @var{others}} (where @var{others} will be added
25939 depending on the needs---this is still in development).
25941 @item @var{result} @expansion{}
25942 @code{ @var{variable} "=" @var{value}}
25944 @item @var{variable} @expansion{}
25945 @code{ @var{string} }
25947 @item @var{value} @expansion{}
25948 @code{ @var{const} | @var{tuple} | @var{list} }
25950 @item @var{const} @expansion{}
25951 @code{@var{c-string}}
25953 @item @var{tuple} @expansion{}
25954 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25956 @item @var{list} @expansion{}
25957 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25958 @var{result} ( "," @var{result} )* "]" }
25960 @item @var{stream-record} @expansion{}
25961 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25963 @item @var{console-stream-output} @expansion{}
25964 @code{"~" @var{c-string}}
25966 @item @var{target-stream-output} @expansion{}
25967 @code{"@@" @var{c-string}}
25969 @item @var{log-stream-output} @expansion{}
25970 @code{"&" @var{c-string}}
25972 @item @var{nl} @expansion{}
25975 @item @var{token} @expansion{}
25976 @emph{any sequence of digits}.
25984 All output sequences end in a single line containing a period.
25987 The @code{@var{token}} is from the corresponding request. Note that
25988 for all async output, while the token is allowed by the grammar and
25989 may be output by future versions of @value{GDBN} for select async
25990 output messages, it is generally omitted. Frontends should treat
25991 all async output as reporting general changes in the state of the
25992 target and there should be no need to associate async output to any
25996 @cindex status output in @sc{gdb/mi}
25997 @var{status-async-output} contains on-going status information about the
25998 progress of a slow operation. It can be discarded. All status output is
25999 prefixed by @samp{+}.
26002 @cindex async output in @sc{gdb/mi}
26003 @var{exec-async-output} contains asynchronous state change on the target
26004 (stopped, started, disappeared). All async output is prefixed by
26008 @cindex notify output in @sc{gdb/mi}
26009 @var{notify-async-output} contains supplementary information that the
26010 client should handle (e.g., a new breakpoint information). All notify
26011 output is prefixed by @samp{=}.
26014 @cindex console output in @sc{gdb/mi}
26015 @var{console-stream-output} is output that should be displayed as is in the
26016 console. It is the textual response to a CLI command. All the console
26017 output is prefixed by @samp{~}.
26020 @cindex target output in @sc{gdb/mi}
26021 @var{target-stream-output} is the output produced by the target program.
26022 All the target output is prefixed by @samp{@@}.
26025 @cindex log output in @sc{gdb/mi}
26026 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26027 instance messages that should be displayed as part of an error log. All
26028 the log output is prefixed by @samp{&}.
26031 @cindex list output in @sc{gdb/mi}
26032 New @sc{gdb/mi} commands should only output @var{lists} containing
26038 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26039 details about the various output records.
26041 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26042 @node GDB/MI Compatibility with CLI
26043 @section @sc{gdb/mi} Compatibility with CLI
26045 @cindex compatibility, @sc{gdb/mi} and CLI
26046 @cindex @sc{gdb/mi}, compatibility with CLI
26048 For the developers convenience CLI commands can be entered directly,
26049 but there may be some unexpected behaviour. For example, commands
26050 that query the user will behave as if the user replied yes, breakpoint
26051 command lists are not executed and some CLI commands, such as
26052 @code{if}, @code{when} and @code{define}, prompt for further input with
26053 @samp{>}, which is not valid MI output.
26055 This feature may be removed at some stage in the future and it is
26056 recommended that front ends use the @code{-interpreter-exec} command
26057 (@pxref{-interpreter-exec}).
26059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26060 @node GDB/MI Development and Front Ends
26061 @section @sc{gdb/mi} Development and Front Ends
26062 @cindex @sc{gdb/mi} development
26064 The application which takes the MI output and presents the state of the
26065 program being debugged to the user is called a @dfn{front end}.
26067 Although @sc{gdb/mi} is still incomplete, it is currently being used
26068 by a variety of front ends to @value{GDBN}. This makes it difficult
26069 to introduce new functionality without breaking existing usage. This
26070 section tries to minimize the problems by describing how the protocol
26073 Some changes in MI need not break a carefully designed front end, and
26074 for these the MI version will remain unchanged. The following is a
26075 list of changes that may occur within one level, so front ends should
26076 parse MI output in a way that can handle them:
26080 New MI commands may be added.
26083 New fields may be added to the output of any MI command.
26086 The range of values for fields with specified values, e.g.,
26087 @code{in_scope} (@pxref{-var-update}) may be extended.
26089 @c The format of field's content e.g type prefix, may change so parse it
26090 @c at your own risk. Yes, in general?
26092 @c The order of fields may change? Shouldn't really matter but it might
26093 @c resolve inconsistencies.
26096 If the changes are likely to break front ends, the MI version level
26097 will be increased by one. This will allow the front end to parse the
26098 output according to the MI version. Apart from mi0, new versions of
26099 @value{GDBN} will not support old versions of MI and it will be the
26100 responsibility of the front end to work with the new one.
26102 @c Starting with mi3, add a new command -mi-version that prints the MI
26105 The best way to avoid unexpected changes in MI that might break your front
26106 end is to make your project known to @value{GDBN} developers and
26107 follow development on @email{gdb@@sourceware.org} and
26108 @email{gdb-patches@@sourceware.org}.
26109 @cindex mailing lists
26111 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26112 @node GDB/MI Output Records
26113 @section @sc{gdb/mi} Output Records
26116 * GDB/MI Result Records::
26117 * GDB/MI Stream Records::
26118 * GDB/MI Async Records::
26119 * GDB/MI Frame Information::
26120 * GDB/MI Thread Information::
26121 * GDB/MI Ada Exception Information::
26124 @node GDB/MI Result Records
26125 @subsection @sc{gdb/mi} Result Records
26127 @cindex result records in @sc{gdb/mi}
26128 @cindex @sc{gdb/mi}, result records
26129 In addition to a number of out-of-band notifications, the response to a
26130 @sc{gdb/mi} command includes one of the following result indications:
26134 @item "^done" [ "," @var{results} ]
26135 The synchronous operation was successful, @code{@var{results}} are the return
26140 This result record is equivalent to @samp{^done}. Historically, it
26141 was output instead of @samp{^done} if the command has resumed the
26142 target. This behaviour is maintained for backward compatibility, but
26143 all frontends should treat @samp{^done} and @samp{^running}
26144 identically and rely on the @samp{*running} output record to determine
26145 which threads are resumed.
26149 @value{GDBN} has connected to a remote target.
26151 @item "^error" "," @var{c-string}
26153 The operation failed. The @code{@var{c-string}} contains the corresponding
26158 @value{GDBN} has terminated.
26162 @node GDB/MI Stream Records
26163 @subsection @sc{gdb/mi} Stream Records
26165 @cindex @sc{gdb/mi}, stream records
26166 @cindex stream records in @sc{gdb/mi}
26167 @value{GDBN} internally maintains a number of output streams: the console, the
26168 target, and the log. The output intended for each of these streams is
26169 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26171 Each stream record begins with a unique @dfn{prefix character} which
26172 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26173 Syntax}). In addition to the prefix, each stream record contains a
26174 @code{@var{string-output}}. This is either raw text (with an implicit new
26175 line) or a quoted C string (which does not contain an implicit newline).
26178 @item "~" @var{string-output}
26179 The console output stream contains text that should be displayed in the
26180 CLI console window. It contains the textual responses to CLI commands.
26182 @item "@@" @var{string-output}
26183 The target output stream contains any textual output from the running
26184 target. This is only present when GDB's event loop is truly
26185 asynchronous, which is currently only the case for remote targets.
26187 @item "&" @var{string-output}
26188 The log stream contains debugging messages being produced by @value{GDBN}'s
26192 @node GDB/MI Async Records
26193 @subsection @sc{gdb/mi} Async Records
26195 @cindex async records in @sc{gdb/mi}
26196 @cindex @sc{gdb/mi}, async records
26197 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26198 additional changes that have occurred. Those changes can either be a
26199 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26200 target activity (e.g., target stopped).
26202 The following is the list of possible async records:
26206 @item *running,thread-id="@var{thread}"
26207 The target is now running. The @var{thread} field tells which
26208 specific thread is now running, and can be @samp{all} if all threads
26209 are running. The frontend should assume that no interaction with a
26210 running thread is possible after this notification is produced.
26211 The frontend should not assume that this notification is output
26212 only once for any command. @value{GDBN} may emit this notification
26213 several times, either for different threads, because it cannot resume
26214 all threads together, or even for a single thread, if the thread must
26215 be stepped though some code before letting it run freely.
26217 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26218 The target has stopped. The @var{reason} field can have one of the
26222 @item breakpoint-hit
26223 A breakpoint was reached.
26224 @item watchpoint-trigger
26225 A watchpoint was triggered.
26226 @item read-watchpoint-trigger
26227 A read watchpoint was triggered.
26228 @item access-watchpoint-trigger
26229 An access watchpoint was triggered.
26230 @item function-finished
26231 An -exec-finish or similar CLI command was accomplished.
26232 @item location-reached
26233 An -exec-until or similar CLI command was accomplished.
26234 @item watchpoint-scope
26235 A watchpoint has gone out of scope.
26236 @item end-stepping-range
26237 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26238 similar CLI command was accomplished.
26239 @item exited-signalled
26240 The inferior exited because of a signal.
26242 The inferior exited.
26243 @item exited-normally
26244 The inferior exited normally.
26245 @item signal-received
26246 A signal was received by the inferior.
26248 The inferior has stopped due to a library being loaded or unloaded.
26249 This can only happen when @code{stop-on-solib-events} (@pxref{Files})
26252 The inferior has forked. This is reported when @code{catch fork}
26253 (@pxref{Set Catchpoints}) has been used.
26255 The inferior has vforked. This is reported in when @code{catch vfork}
26256 (@pxref{Set Catchpoints}) has been used.
26257 @item syscall-entry
26258 The inferior entered a system call. This is reported when @code{catch
26259 syscall} (@pxref{Set Catchpoints}) has been used.
26260 @item syscall-entry
26261 The inferior returned from a system call. This is reported when
26262 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26264 The inferior called @code{exec}. This is reported when @code{catch exec}
26265 (@pxref{Set Catchpoints}) has been used.
26268 The @var{id} field identifies the thread that directly caused the stop
26269 -- for example by hitting a breakpoint. Depending on whether all-stop
26270 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26271 stop all threads, or only the thread that directly triggered the stop.
26272 If all threads are stopped, the @var{stopped} field will have the
26273 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26274 field will be a list of thread identifiers. Presently, this list will
26275 always include a single thread, but frontend should be prepared to see
26276 several threads in the list. The @var{core} field reports the
26277 processor core on which the stop event has happened. This field may be absent
26278 if such information is not available.
26280 @item =thread-group-added,id="@var{id}"
26281 @itemx =thread-group-removed,id="@var{id}"
26282 A thread group was either added or removed. The @var{id} field
26283 contains the @value{GDBN} identifier of the thread group. When a thread
26284 group is added, it generally might not be associated with a running
26285 process. When a thread group is removed, its id becomes invalid and
26286 cannot be used in any way.
26288 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26289 A thread group became associated with a running program,
26290 either because the program was just started or the thread group
26291 was attached to a program. The @var{id} field contains the
26292 @value{GDBN} identifier of the thread group. The @var{pid} field
26293 contains process identifier, specific to the operating system.
26295 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26296 A thread group is no longer associated with a running program,
26297 either because the program has exited, or because it was detached
26298 from. The @var{id} field contains the @value{GDBN} identifier of the
26299 thread group. @var{code} is the exit code of the inferior; it exists
26300 only when the inferior exited with some code.
26302 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26303 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26304 A thread either was created, or has exited. The @var{id} field
26305 contains the @value{GDBN} identifier of the thread. The @var{gid}
26306 field identifies the thread group this thread belongs to.
26308 @item =thread-selected,id="@var{id}"
26309 Informs that the selected thread was changed as result of the last
26310 command. This notification is not emitted as result of @code{-thread-select}
26311 command but is emitted whenever an MI command that is not documented
26312 to change the selected thread actually changes it. In particular,
26313 invoking, directly or indirectly (via user-defined command), the CLI
26314 @code{thread} command, will generate this notification.
26316 We suggest that in response to this notification, front ends
26317 highlight the selected thread and cause subsequent commands to apply to
26320 @item =library-loaded,...
26321 Reports that a new library file was loaded by the program. This
26322 notification has 4 fields---@var{id}, @var{target-name},
26323 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26324 opaque identifier of the library. For remote debugging case,
26325 @var{target-name} and @var{host-name} fields give the name of the
26326 library file on the target, and on the host respectively. For native
26327 debugging, both those fields have the same value. The
26328 @var{symbols-loaded} field is emitted only for backward compatibility
26329 and should not be relied on to convey any useful information. The
26330 @var{thread-group} field, if present, specifies the id of the thread
26331 group in whose context the library was loaded. If the field is
26332 absent, it means the library was loaded in the context of all present
26335 @item =library-unloaded,...
26336 Reports that a library was unloaded by the program. This notification
26337 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26338 the same meaning as for the @code{=library-loaded} notification.
26339 The @var{thread-group} field, if present, specifies the id of the
26340 thread group in whose context the library was unloaded. If the field is
26341 absent, it means the library was unloaded in the context of all present
26344 @item =breakpoint-created,bkpt=@{...@}
26345 @itemx =breakpoint-modified,bkpt=@{...@}
26346 @itemx =breakpoint-deleted,bkpt=@{...@}
26347 Reports that a breakpoint was created, modified, or deleted,
26348 respectively. Only user-visible breakpoints are reported to the MI
26351 The @var{bkpt} argument is of the same form as returned by the various
26352 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26354 Note that if a breakpoint is emitted in the result record of a
26355 command, then it will not also be emitted in an async record.
26359 @node GDB/MI Frame Information
26360 @subsection @sc{gdb/mi} Frame Information
26362 Response from many MI commands includes an information about stack
26363 frame. This information is a tuple that may have the following
26368 The level of the stack frame. The innermost frame has the level of
26369 zero. This field is always present.
26372 The name of the function corresponding to the frame. This field may
26373 be absent if @value{GDBN} is unable to determine the function name.
26376 The code address for the frame. This field is always present.
26379 The name of the source files that correspond to the frame's code
26380 address. This field may be absent.
26383 The source line corresponding to the frames' code address. This field
26387 The name of the binary file (either executable or shared library) the
26388 corresponds to the frame's code address. This field may be absent.
26392 @node GDB/MI Thread Information
26393 @subsection @sc{gdb/mi} Thread Information
26395 Whenever @value{GDBN} has to report an information about a thread, it
26396 uses a tuple with the following fields:
26400 The numeric id assigned to the thread by @value{GDBN}. This field is
26404 Target-specific string identifying the thread. This field is always present.
26407 Additional information about the thread provided by the target.
26408 It is supposed to be human-readable and not interpreted by the
26409 frontend. This field is optional.
26412 Either @samp{stopped} or @samp{running}, depending on whether the
26413 thread is presently running. This field is always present.
26416 The value of this field is an integer number of the processor core the
26417 thread was last seen on. This field is optional.
26420 @node GDB/MI Ada Exception Information
26421 @subsection @sc{gdb/mi} Ada Exception Information
26423 Whenever a @code{*stopped} record is emitted because the program
26424 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26425 @value{GDBN} provides the name of the exception that was raised via
26426 the @code{exception-name} field.
26428 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26429 @node GDB/MI Simple Examples
26430 @section Simple Examples of @sc{gdb/mi} Interaction
26431 @cindex @sc{gdb/mi}, simple examples
26433 This subsection presents several simple examples of interaction using
26434 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26435 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26436 the output received from @sc{gdb/mi}.
26438 Note the line breaks shown in the examples are here only for
26439 readability, they don't appear in the real output.
26441 @subheading Setting a Breakpoint
26443 Setting a breakpoint generates synchronous output which contains detailed
26444 information of the breakpoint.
26447 -> -break-insert main
26448 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26449 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26450 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26454 @subheading Program Execution
26456 Program execution generates asynchronous records and MI gives the
26457 reason that execution stopped.
26463 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26464 frame=@{addr="0x08048564",func="main",
26465 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26466 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26471 <- *stopped,reason="exited-normally"
26475 @subheading Quitting @value{GDBN}
26477 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26485 Please note that @samp{^exit} is printed immediately, but it might
26486 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26487 performs necessary cleanups, including killing programs being debugged
26488 or disconnecting from debug hardware, so the frontend should wait till
26489 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26490 fails to exit in reasonable time.
26492 @subheading A Bad Command
26494 Here's what happens if you pass a non-existent command:
26498 <- ^error,msg="Undefined MI command: rubbish"
26503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26504 @node GDB/MI Command Description Format
26505 @section @sc{gdb/mi} Command Description Format
26507 The remaining sections describe blocks of commands. Each block of
26508 commands is laid out in a fashion similar to this section.
26510 @subheading Motivation
26512 The motivation for this collection of commands.
26514 @subheading Introduction
26516 A brief introduction to this collection of commands as a whole.
26518 @subheading Commands
26520 For each command in the block, the following is described:
26522 @subsubheading Synopsis
26525 -command @var{args}@dots{}
26528 @subsubheading Result
26530 @subsubheading @value{GDBN} Command
26532 The corresponding @value{GDBN} CLI command(s), if any.
26534 @subsubheading Example
26536 Example(s) formatted for readability. Some of the described commands have
26537 not been implemented yet and these are labeled N.A.@: (not available).
26540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26541 @node GDB/MI Breakpoint Commands
26542 @section @sc{gdb/mi} Breakpoint Commands
26544 @cindex breakpoint commands for @sc{gdb/mi}
26545 @cindex @sc{gdb/mi}, breakpoint commands
26546 This section documents @sc{gdb/mi} commands for manipulating
26549 @subheading The @code{-break-after} Command
26550 @findex -break-after
26552 @subsubheading Synopsis
26555 -break-after @var{number} @var{count}
26558 The breakpoint number @var{number} is not in effect until it has been
26559 hit @var{count} times. To see how this is reflected in the output of
26560 the @samp{-break-list} command, see the description of the
26561 @samp{-break-list} command below.
26563 @subsubheading @value{GDBN} Command
26565 The corresponding @value{GDBN} command is @samp{ignore}.
26567 @subsubheading Example
26572 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26573 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26574 fullname="/home/foo/hello.c",line="5",times="0"@}
26581 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26582 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26583 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26584 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26585 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26586 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26587 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26588 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26589 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26590 line="5",times="0",ignore="3"@}]@}
26595 @subheading The @code{-break-catch} Command
26596 @findex -break-catch
26599 @subheading The @code{-break-commands} Command
26600 @findex -break-commands
26602 @subsubheading Synopsis
26605 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26608 Specifies the CLI commands that should be executed when breakpoint
26609 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26610 are the commands. If no command is specified, any previously-set
26611 commands are cleared. @xref{Break Commands}. Typical use of this
26612 functionality is tracing a program, that is, printing of values of
26613 some variables whenever breakpoint is hit and then continuing.
26615 @subsubheading @value{GDBN} Command
26617 The corresponding @value{GDBN} command is @samp{commands}.
26619 @subsubheading Example
26624 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26625 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26626 fullname="/home/foo/hello.c",line="5",times="0"@}
26628 -break-commands 1 "print v" "continue"
26633 @subheading The @code{-break-condition} Command
26634 @findex -break-condition
26636 @subsubheading Synopsis
26639 -break-condition @var{number} @var{expr}
26642 Breakpoint @var{number} will stop the program only if the condition in
26643 @var{expr} is true. The condition becomes part of the
26644 @samp{-break-list} output (see the description of the @samp{-break-list}
26647 @subsubheading @value{GDBN} Command
26649 The corresponding @value{GDBN} command is @samp{condition}.
26651 @subsubheading Example
26655 -break-condition 1 1
26659 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26660 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26661 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26662 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26663 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26664 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26665 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26666 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26667 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26668 line="5",cond="1",times="0",ignore="3"@}]@}
26672 @subheading The @code{-break-delete} Command
26673 @findex -break-delete
26675 @subsubheading Synopsis
26678 -break-delete ( @var{breakpoint} )+
26681 Delete the breakpoint(s) whose number(s) are specified in the argument
26682 list. This is obviously reflected in the breakpoint list.
26684 @subsubheading @value{GDBN} Command
26686 The corresponding @value{GDBN} command is @samp{delete}.
26688 @subsubheading Example
26696 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26697 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26698 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26699 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26700 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26701 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26702 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26707 @subheading The @code{-break-disable} Command
26708 @findex -break-disable
26710 @subsubheading Synopsis
26713 -break-disable ( @var{breakpoint} )+
26716 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26717 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26719 @subsubheading @value{GDBN} Command
26721 The corresponding @value{GDBN} command is @samp{disable}.
26723 @subsubheading Example
26731 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26732 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26733 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26734 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26735 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26736 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26737 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26738 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26739 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26740 line="5",times="0"@}]@}
26744 @subheading The @code{-break-enable} Command
26745 @findex -break-enable
26747 @subsubheading Synopsis
26750 -break-enable ( @var{breakpoint} )+
26753 Enable (previously disabled) @var{breakpoint}(s).
26755 @subsubheading @value{GDBN} Command
26757 The corresponding @value{GDBN} command is @samp{enable}.
26759 @subsubheading Example
26767 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26768 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26769 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26770 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26771 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26772 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26773 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26774 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26775 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26776 line="5",times="0"@}]@}
26780 @subheading The @code{-break-info} Command
26781 @findex -break-info
26783 @subsubheading Synopsis
26786 -break-info @var{breakpoint}
26790 Get information about a single breakpoint.
26792 @subsubheading @value{GDBN} Command
26794 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26796 @subsubheading Example
26799 @subheading The @code{-break-insert} Command
26800 @findex -break-insert
26802 @subsubheading Synopsis
26805 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26806 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26807 [ -p @var{thread} ] [ @var{location} ]
26811 If specified, @var{location}, can be one of:
26818 @item filename:linenum
26819 @item filename:function
26823 The possible optional parameters of this command are:
26827 Insert a temporary breakpoint.
26829 Insert a hardware breakpoint.
26830 @item -c @var{condition}
26831 Make the breakpoint conditional on @var{condition}.
26832 @item -i @var{ignore-count}
26833 Initialize the @var{ignore-count}.
26835 If @var{location} cannot be parsed (for example if it
26836 refers to unknown files or functions), create a pending
26837 breakpoint. Without this flag, @value{GDBN} will report
26838 an error, and won't create a breakpoint, if @var{location}
26841 Create a disabled breakpoint.
26843 Create a tracepoint. @xref{Tracepoints}. When this parameter
26844 is used together with @samp{-h}, a fast tracepoint is created.
26847 @subsubheading Result
26849 The result is in the form:
26852 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26853 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26854 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26855 times="@var{times}"@}
26859 where @var{number} is the @value{GDBN} number for this breakpoint,
26860 @var{funcname} is the name of the function where the breakpoint was
26861 inserted, @var{filename} is the name of the source file which contains
26862 this function, @var{lineno} is the source line number within that file
26863 and @var{times} the number of times that the breakpoint has been hit
26864 (always 0 for -break-insert but may be greater for -break-info or -break-list
26865 which use the same output).
26867 Note: this format is open to change.
26868 @c An out-of-band breakpoint instead of part of the result?
26870 @subsubheading @value{GDBN} Command
26872 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26873 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26875 @subsubheading Example
26880 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26881 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26883 -break-insert -t foo
26884 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26885 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26888 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26889 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26890 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26891 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26892 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26893 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26894 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26895 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26896 addr="0x0001072c", func="main",file="recursive2.c",
26897 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26898 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26899 addr="0x00010774",func="foo",file="recursive2.c",
26900 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26902 -break-insert -r foo.*
26903 ~int foo(int, int);
26904 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26905 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26909 @subheading The @code{-break-list} Command
26910 @findex -break-list
26912 @subsubheading Synopsis
26918 Displays the list of inserted breakpoints, showing the following fields:
26922 number of the breakpoint
26924 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26926 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26929 is the breakpoint enabled or no: @samp{y} or @samp{n}
26931 memory location at which the breakpoint is set
26933 logical location of the breakpoint, expressed by function name, file
26936 number of times the breakpoint has been hit
26939 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26940 @code{body} field is an empty list.
26942 @subsubheading @value{GDBN} Command
26944 The corresponding @value{GDBN} command is @samp{info break}.
26946 @subsubheading Example
26951 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26952 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26953 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26954 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26955 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26956 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26957 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26958 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26959 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26960 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26961 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26962 line="13",times="0"@}]@}
26966 Here's an example of the result when there are no breakpoints:
26971 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26972 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26973 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26974 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26975 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26976 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26977 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26982 @subheading The @code{-break-passcount} Command
26983 @findex -break-passcount
26985 @subsubheading Synopsis
26988 -break-passcount @var{tracepoint-number} @var{passcount}
26991 Set the passcount for tracepoint @var{tracepoint-number} to
26992 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26993 is not a tracepoint, error is emitted. This corresponds to CLI
26994 command @samp{passcount}.
26996 @subheading The @code{-break-watch} Command
26997 @findex -break-watch
26999 @subsubheading Synopsis
27002 -break-watch [ -a | -r ]
27005 Create a watchpoint. With the @samp{-a} option it will create an
27006 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27007 read from or on a write to the memory location. With the @samp{-r}
27008 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27009 trigger only when the memory location is accessed for reading. Without
27010 either of the options, the watchpoint created is a regular watchpoint,
27011 i.e., it will trigger when the memory location is accessed for writing.
27012 @xref{Set Watchpoints, , Setting Watchpoints}.
27014 Note that @samp{-break-list} will report a single list of watchpoints and
27015 breakpoints inserted.
27017 @subsubheading @value{GDBN} Command
27019 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27022 @subsubheading Example
27024 Setting a watchpoint on a variable in the @code{main} function:
27029 ^done,wpt=@{number="2",exp="x"@}
27034 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27035 value=@{old="-268439212",new="55"@},
27036 frame=@{func="main",args=[],file="recursive2.c",
27037 fullname="/home/foo/bar/recursive2.c",line="5"@}
27041 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27042 the program execution twice: first for the variable changing value, then
27043 for the watchpoint going out of scope.
27048 ^done,wpt=@{number="5",exp="C"@}
27053 *stopped,reason="watchpoint-trigger",
27054 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27055 frame=@{func="callee4",args=[],
27056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27057 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27062 *stopped,reason="watchpoint-scope",wpnum="5",
27063 frame=@{func="callee3",args=[@{name="strarg",
27064 value="0x11940 \"A string argument.\""@}],
27065 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27066 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27070 Listing breakpoints and watchpoints, at different points in the program
27071 execution. Note that once the watchpoint goes out of scope, it is
27077 ^done,wpt=@{number="2",exp="C"@}
27080 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27081 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27082 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27083 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27084 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27085 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27086 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27087 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27088 addr="0x00010734",func="callee4",
27089 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27090 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27091 bkpt=@{number="2",type="watchpoint",disp="keep",
27092 enabled="y",addr="",what="C",times="0"@}]@}
27097 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27098 value=@{old="-276895068",new="3"@},
27099 frame=@{func="callee4",args=[],
27100 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27101 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27104 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27105 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27106 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27107 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27108 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27109 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27110 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27111 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27112 addr="0x00010734",func="callee4",
27113 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27114 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27115 bkpt=@{number="2",type="watchpoint",disp="keep",
27116 enabled="y",addr="",what="C",times="-5"@}]@}
27120 ^done,reason="watchpoint-scope",wpnum="2",
27121 frame=@{func="callee3",args=[@{name="strarg",
27122 value="0x11940 \"A string argument.\""@}],
27123 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27124 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27127 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27128 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27129 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27130 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27131 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27132 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27133 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27134 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27135 addr="0x00010734",func="callee4",
27136 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27137 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27143 @node GDB/MI Program Context
27144 @section @sc{gdb/mi} Program Context
27146 @subheading The @code{-exec-arguments} Command
27147 @findex -exec-arguments
27150 @subsubheading Synopsis
27153 -exec-arguments @var{args}
27156 Set the inferior program arguments, to be used in the next
27159 @subsubheading @value{GDBN} Command
27161 The corresponding @value{GDBN} command is @samp{set args}.
27163 @subsubheading Example
27167 -exec-arguments -v word
27174 @subheading The @code{-exec-show-arguments} Command
27175 @findex -exec-show-arguments
27177 @subsubheading Synopsis
27180 -exec-show-arguments
27183 Print the arguments of the program.
27185 @subsubheading @value{GDBN} Command
27187 The corresponding @value{GDBN} command is @samp{show args}.
27189 @subsubheading Example
27194 @subheading The @code{-environment-cd} Command
27195 @findex -environment-cd
27197 @subsubheading Synopsis
27200 -environment-cd @var{pathdir}
27203 Set @value{GDBN}'s working directory.
27205 @subsubheading @value{GDBN} Command
27207 The corresponding @value{GDBN} command is @samp{cd}.
27209 @subsubheading Example
27213 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27219 @subheading The @code{-environment-directory} Command
27220 @findex -environment-directory
27222 @subsubheading Synopsis
27225 -environment-directory [ -r ] [ @var{pathdir} ]+
27228 Add directories @var{pathdir} to beginning of search path for source files.
27229 If the @samp{-r} option is used, the search path is reset to the default
27230 search path. If directories @var{pathdir} are supplied in addition to the
27231 @samp{-r} option, the search path is first reset and then addition
27233 Multiple directories may be specified, separated by blanks. Specifying
27234 multiple directories in a single command
27235 results in the directories added to the beginning of the
27236 search path in the same order they were presented in the command.
27237 If blanks are needed as
27238 part of a directory name, double-quotes should be used around
27239 the name. In the command output, the path will show up separated
27240 by the system directory-separator character. The directory-separator
27241 character must not be used
27242 in any directory name.
27243 If no directories are specified, the current search path is displayed.
27245 @subsubheading @value{GDBN} Command
27247 The corresponding @value{GDBN} command is @samp{dir}.
27249 @subsubheading Example
27253 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27254 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27256 -environment-directory ""
27257 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27259 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27260 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27262 -environment-directory -r
27263 ^done,source-path="$cdir:$cwd"
27268 @subheading The @code{-environment-path} Command
27269 @findex -environment-path
27271 @subsubheading Synopsis
27274 -environment-path [ -r ] [ @var{pathdir} ]+
27277 Add directories @var{pathdir} to beginning of search path for object files.
27278 If the @samp{-r} option is used, the search path is reset to the original
27279 search path that existed at gdb start-up. If directories @var{pathdir} are
27280 supplied in addition to the
27281 @samp{-r} option, the search path is first reset and then addition
27283 Multiple directories may be specified, separated by blanks. Specifying
27284 multiple directories in a single command
27285 results in the directories added to the beginning of the
27286 search path in the same order they were presented in the command.
27287 If blanks are needed as
27288 part of a directory name, double-quotes should be used around
27289 the name. In the command output, the path will show up separated
27290 by the system directory-separator character. The directory-separator
27291 character must not be used
27292 in any directory name.
27293 If no directories are specified, the current path is displayed.
27296 @subsubheading @value{GDBN} Command
27298 The corresponding @value{GDBN} command is @samp{path}.
27300 @subsubheading Example
27305 ^done,path="/usr/bin"
27307 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27308 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27310 -environment-path -r /usr/local/bin
27311 ^done,path="/usr/local/bin:/usr/bin"
27316 @subheading The @code{-environment-pwd} Command
27317 @findex -environment-pwd
27319 @subsubheading Synopsis
27325 Show the current working directory.
27327 @subsubheading @value{GDBN} Command
27329 The corresponding @value{GDBN} command is @samp{pwd}.
27331 @subsubheading Example
27336 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27340 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27341 @node GDB/MI Thread Commands
27342 @section @sc{gdb/mi} Thread Commands
27345 @subheading The @code{-thread-info} Command
27346 @findex -thread-info
27348 @subsubheading Synopsis
27351 -thread-info [ @var{thread-id} ]
27354 Reports information about either a specific thread, if
27355 the @var{thread-id} parameter is present, or about all
27356 threads. When printing information about all threads,
27357 also reports the current thread.
27359 @subsubheading @value{GDBN} Command
27361 The @samp{info thread} command prints the same information
27364 @subsubheading Result
27366 The result is a list of threads. The following attributes are
27367 defined for a given thread:
27371 This field exists only for the current thread. It has the value @samp{*}.
27374 The identifier that @value{GDBN} uses to refer to the thread.
27377 The identifier that the target uses to refer to the thread.
27380 Extra information about the thread, in a target-specific format. This
27384 The name of the thread. If the user specified a name using the
27385 @code{thread name} command, then this name is given. Otherwise, if
27386 @value{GDBN} can extract the thread name from the target, then that
27387 name is given. If @value{GDBN} cannot find the thread name, then this
27391 The stack frame currently executing in the thread.
27394 The thread's state. The @samp{state} field may have the following
27399 The thread is stopped. Frame information is available for stopped
27403 The thread is running. There's no frame information for running
27409 If @value{GDBN} can find the CPU core on which this thread is running,
27410 then this field is the core identifier. This field is optional.
27414 @subsubheading Example
27419 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27420 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27421 args=[]@},state="running"@},
27422 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27423 frame=@{level="0",addr="0x0804891f",func="foo",
27424 args=[@{name="i",value="10"@}],
27425 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27426 state="running"@}],
27427 current-thread-id="1"
27431 @subheading The @code{-thread-list-ids} Command
27432 @findex -thread-list-ids
27434 @subsubheading Synopsis
27440 Produces a list of the currently known @value{GDBN} thread ids. At the
27441 end of the list it also prints the total number of such threads.
27443 This command is retained for historical reasons, the
27444 @code{-thread-info} command should be used instead.
27446 @subsubheading @value{GDBN} Command
27448 Part of @samp{info threads} supplies the same information.
27450 @subsubheading Example
27455 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27456 current-thread-id="1",number-of-threads="3"
27461 @subheading The @code{-thread-select} Command
27462 @findex -thread-select
27464 @subsubheading Synopsis
27467 -thread-select @var{threadnum}
27470 Make @var{threadnum} the current thread. It prints the number of the new
27471 current thread, and the topmost frame for that thread.
27473 This command is deprecated in favor of explicitly using the
27474 @samp{--thread} option to each command.
27476 @subsubheading @value{GDBN} Command
27478 The corresponding @value{GDBN} command is @samp{thread}.
27480 @subsubheading Example
27487 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27488 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27492 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27493 number-of-threads="3"
27496 ^done,new-thread-id="3",
27497 frame=@{level="0",func="vprintf",
27498 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27499 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27504 @node GDB/MI Ada Tasking Commands
27505 @section @sc{gdb/mi} Ada Tasking Commands
27507 @subheading The @code{-ada-task-info} Command
27508 @findex -ada-task-info
27510 @subsubheading Synopsis
27513 -ada-task-info [ @var{task-id} ]
27516 Reports information about either a specific Ada task, if the
27517 @var{task-id} parameter is present, or about all Ada tasks.
27519 @subsubheading @value{GDBN} Command
27521 The @samp{info tasks} command prints the same information
27522 about all Ada tasks (@pxref{Ada Tasks}).
27524 @subsubheading Result
27526 The result is a table of Ada tasks. The following columns are
27527 defined for each Ada task:
27531 This field exists only for the current thread. It has the value @samp{*}.
27534 The identifier that @value{GDBN} uses to refer to the Ada task.
27537 The identifier that the target uses to refer to the Ada task.
27540 The identifier of the thread corresponding to the Ada task.
27542 This field should always exist, as Ada tasks are always implemented
27543 on top of a thread. But if @value{GDBN} cannot find this corresponding
27544 thread for any reason, the field is omitted.
27547 This field exists only when the task was created by another task.
27548 In this case, it provides the ID of the parent task.
27551 The base priority of the task.
27554 The current state of the task. For a detailed description of the
27555 possible states, see @ref{Ada Tasks}.
27558 The name of the task.
27562 @subsubheading Example
27566 ^done,tasks=@{nr_rows="3",nr_cols="8",
27567 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27568 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27569 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27570 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27571 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27572 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27573 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27574 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27575 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27576 state="Child Termination Wait",name="main_task"@}]@}
27580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27581 @node GDB/MI Program Execution
27582 @section @sc{gdb/mi} Program Execution
27584 These are the asynchronous commands which generate the out-of-band
27585 record @samp{*stopped}. Currently @value{GDBN} only really executes
27586 asynchronously with remote targets and this interaction is mimicked in
27589 @subheading The @code{-exec-continue} Command
27590 @findex -exec-continue
27592 @subsubheading Synopsis
27595 -exec-continue [--reverse] [--all|--thread-group N]
27598 Resumes the execution of the inferior program, which will continue
27599 to execute until it reaches a debugger stop event. If the
27600 @samp{--reverse} option is specified, execution resumes in reverse until
27601 it reaches a stop event. Stop events may include
27604 breakpoints or watchpoints
27606 signals or exceptions
27608 the end of the process (or its beginning under @samp{--reverse})
27610 the end or beginning of a replay log if one is being used.
27612 In all-stop mode (@pxref{All-Stop
27613 Mode}), may resume only one thread, or all threads, depending on the
27614 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27615 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27616 ignored in all-stop mode. If the @samp{--thread-group} options is
27617 specified, then all threads in that thread group are resumed.
27619 @subsubheading @value{GDBN} Command
27621 The corresponding @value{GDBN} corresponding is @samp{continue}.
27623 @subsubheading Example
27630 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27631 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27637 @subheading The @code{-exec-finish} Command
27638 @findex -exec-finish
27640 @subsubheading Synopsis
27643 -exec-finish [--reverse]
27646 Resumes the execution of the inferior program until the current
27647 function is exited. Displays the results returned by the function.
27648 If the @samp{--reverse} option is specified, resumes the reverse
27649 execution of the inferior program until the point where current
27650 function was called.
27652 @subsubheading @value{GDBN} Command
27654 The corresponding @value{GDBN} command is @samp{finish}.
27656 @subsubheading Example
27658 Function returning @code{void}.
27665 *stopped,reason="function-finished",frame=@{func="main",args=[],
27666 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27670 Function returning other than @code{void}. The name of the internal
27671 @value{GDBN} variable storing the result is printed, together with the
27678 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27679 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27680 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27681 gdb-result-var="$1",return-value="0"
27686 @subheading The @code{-exec-interrupt} Command
27687 @findex -exec-interrupt
27689 @subsubheading Synopsis
27692 -exec-interrupt [--all|--thread-group N]
27695 Interrupts the background execution of the target. Note how the token
27696 associated with the stop message is the one for the execution command
27697 that has been interrupted. The token for the interrupt itself only
27698 appears in the @samp{^done} output. If the user is trying to
27699 interrupt a non-running program, an error message will be printed.
27701 Note that when asynchronous execution is enabled, this command is
27702 asynchronous just like other execution commands. That is, first the
27703 @samp{^done} response will be printed, and the target stop will be
27704 reported after that using the @samp{*stopped} notification.
27706 In non-stop mode, only the context thread is interrupted by default.
27707 All threads (in all inferiors) will be interrupted if the
27708 @samp{--all} option is specified. If the @samp{--thread-group}
27709 option is specified, all threads in that group will be interrupted.
27711 @subsubheading @value{GDBN} Command
27713 The corresponding @value{GDBN} command is @samp{interrupt}.
27715 @subsubheading Example
27726 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27727 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27728 fullname="/home/foo/bar/try.c",line="13"@}
27733 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27737 @subheading The @code{-exec-jump} Command
27740 @subsubheading Synopsis
27743 -exec-jump @var{location}
27746 Resumes execution of the inferior program at the location specified by
27747 parameter. @xref{Specify Location}, for a description of the
27748 different forms of @var{location}.
27750 @subsubheading @value{GDBN} Command
27752 The corresponding @value{GDBN} command is @samp{jump}.
27754 @subsubheading Example
27757 -exec-jump foo.c:10
27758 *running,thread-id="all"
27763 @subheading The @code{-exec-next} Command
27766 @subsubheading Synopsis
27769 -exec-next [--reverse]
27772 Resumes execution of the inferior program, stopping when the beginning
27773 of the next source line is reached.
27775 If the @samp{--reverse} option is specified, resumes reverse execution
27776 of the inferior program, stopping at the beginning of the previous
27777 source line. If you issue this command on the first line of a
27778 function, it will take you back to the caller of that function, to the
27779 source line where the function was called.
27782 @subsubheading @value{GDBN} Command
27784 The corresponding @value{GDBN} command is @samp{next}.
27786 @subsubheading Example
27792 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27797 @subheading The @code{-exec-next-instruction} Command
27798 @findex -exec-next-instruction
27800 @subsubheading Synopsis
27803 -exec-next-instruction [--reverse]
27806 Executes one machine instruction. If the instruction is a function
27807 call, continues until the function returns. If the program stops at an
27808 instruction in the middle of a source line, the address will be
27811 If the @samp{--reverse} option is specified, resumes reverse execution
27812 of the inferior program, stopping at the previous instruction. If the
27813 previously executed instruction was a return from another function,
27814 it will continue to execute in reverse until the call to that function
27815 (from the current stack frame) is reached.
27817 @subsubheading @value{GDBN} Command
27819 The corresponding @value{GDBN} command is @samp{nexti}.
27821 @subsubheading Example
27825 -exec-next-instruction
27829 *stopped,reason="end-stepping-range",
27830 addr="0x000100d4",line="5",file="hello.c"
27835 @subheading The @code{-exec-return} Command
27836 @findex -exec-return
27838 @subsubheading Synopsis
27844 Makes current function return immediately. Doesn't execute the inferior.
27845 Displays the new current frame.
27847 @subsubheading @value{GDBN} Command
27849 The corresponding @value{GDBN} command is @samp{return}.
27851 @subsubheading Example
27855 200-break-insert callee4
27856 200^done,bkpt=@{number="1",addr="0x00010734",
27857 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27862 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27863 frame=@{func="callee4",args=[],
27864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27865 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27871 111^done,frame=@{level="0",func="callee3",
27872 args=[@{name="strarg",
27873 value="0x11940 \"A string argument.\""@}],
27874 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27875 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27880 @subheading The @code{-exec-run} Command
27883 @subsubheading Synopsis
27886 -exec-run [--all | --thread-group N]
27889 Starts execution of the inferior from the beginning. The inferior
27890 executes until either a breakpoint is encountered or the program
27891 exits. In the latter case the output will include an exit code, if
27892 the program has exited exceptionally.
27894 When no option is specified, the current inferior is started. If the
27895 @samp{--thread-group} option is specified, it should refer to a thread
27896 group of type @samp{process}, and that thread group will be started.
27897 If the @samp{--all} option is specified, then all inferiors will be started.
27899 @subsubheading @value{GDBN} Command
27901 The corresponding @value{GDBN} command is @samp{run}.
27903 @subsubheading Examples
27908 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27913 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27914 frame=@{func="main",args=[],file="recursive2.c",
27915 fullname="/home/foo/bar/recursive2.c",line="4"@}
27920 Program exited normally:
27928 *stopped,reason="exited-normally"
27933 Program exited exceptionally:
27941 *stopped,reason="exited",exit-code="01"
27945 Another way the program can terminate is if it receives a signal such as
27946 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27950 *stopped,reason="exited-signalled",signal-name="SIGINT",
27951 signal-meaning="Interrupt"
27955 @c @subheading -exec-signal
27958 @subheading The @code{-exec-step} Command
27961 @subsubheading Synopsis
27964 -exec-step [--reverse]
27967 Resumes execution of the inferior program, stopping when the beginning
27968 of the next source line is reached, if the next source line is not a
27969 function call. If it is, stop at the first instruction of the called
27970 function. If the @samp{--reverse} option is specified, resumes reverse
27971 execution of the inferior program, stopping at the beginning of the
27972 previously executed source line.
27974 @subsubheading @value{GDBN} Command
27976 The corresponding @value{GDBN} command is @samp{step}.
27978 @subsubheading Example
27980 Stepping into a function:
27986 *stopped,reason="end-stepping-range",
27987 frame=@{func="foo",args=[@{name="a",value="10"@},
27988 @{name="b",value="0"@}],file="recursive2.c",
27989 fullname="/home/foo/bar/recursive2.c",line="11"@}
27999 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28004 @subheading The @code{-exec-step-instruction} Command
28005 @findex -exec-step-instruction
28007 @subsubheading Synopsis
28010 -exec-step-instruction [--reverse]
28013 Resumes the inferior which executes one machine instruction. If the
28014 @samp{--reverse} option is specified, resumes reverse execution of the
28015 inferior program, stopping at the previously executed instruction.
28016 The output, once @value{GDBN} has stopped, will vary depending on
28017 whether we have stopped in the middle of a source line or not. In the
28018 former case, the address at which the program stopped will be printed
28021 @subsubheading @value{GDBN} Command
28023 The corresponding @value{GDBN} command is @samp{stepi}.
28025 @subsubheading Example
28029 -exec-step-instruction
28033 *stopped,reason="end-stepping-range",
28034 frame=@{func="foo",args=[],file="try.c",
28035 fullname="/home/foo/bar/try.c",line="10"@}
28037 -exec-step-instruction
28041 *stopped,reason="end-stepping-range",
28042 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28043 fullname="/home/foo/bar/try.c",line="10"@}
28048 @subheading The @code{-exec-until} Command
28049 @findex -exec-until
28051 @subsubheading Synopsis
28054 -exec-until [ @var{location} ]
28057 Executes the inferior until the @var{location} specified in the
28058 argument is reached. If there is no argument, the inferior executes
28059 until a source line greater than the current one is reached. The
28060 reason for stopping in this case will be @samp{location-reached}.
28062 @subsubheading @value{GDBN} Command
28064 The corresponding @value{GDBN} command is @samp{until}.
28066 @subsubheading Example
28070 -exec-until recursive2.c:6
28074 *stopped,reason="location-reached",frame=@{func="main",args=[],
28075 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28080 @subheading -file-clear
28081 Is this going away????
28084 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28085 @node GDB/MI Stack Manipulation
28086 @section @sc{gdb/mi} Stack Manipulation Commands
28089 @subheading The @code{-stack-info-frame} Command
28090 @findex -stack-info-frame
28092 @subsubheading Synopsis
28098 Get info on the selected frame.
28100 @subsubheading @value{GDBN} Command
28102 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28103 (without arguments).
28105 @subsubheading Example
28110 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28111 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28112 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28116 @subheading The @code{-stack-info-depth} Command
28117 @findex -stack-info-depth
28119 @subsubheading Synopsis
28122 -stack-info-depth [ @var{max-depth} ]
28125 Return the depth of the stack. If the integer argument @var{max-depth}
28126 is specified, do not count beyond @var{max-depth} frames.
28128 @subsubheading @value{GDBN} Command
28130 There's no equivalent @value{GDBN} command.
28132 @subsubheading Example
28134 For a stack with frame levels 0 through 11:
28141 -stack-info-depth 4
28144 -stack-info-depth 12
28147 -stack-info-depth 11
28150 -stack-info-depth 13
28155 @subheading The @code{-stack-list-arguments} Command
28156 @findex -stack-list-arguments
28158 @subsubheading Synopsis
28161 -stack-list-arguments @var{print-values}
28162 [ @var{low-frame} @var{high-frame} ]
28165 Display a list of the arguments for the frames between @var{low-frame}
28166 and @var{high-frame} (inclusive). If @var{low-frame} and
28167 @var{high-frame} are not provided, list the arguments for the whole
28168 call stack. If the two arguments are equal, show the single frame
28169 at the corresponding level. It is an error if @var{low-frame} is
28170 larger than the actual number of frames. On the other hand,
28171 @var{high-frame} may be larger than the actual number of frames, in
28172 which case only existing frames will be returned.
28174 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28175 the variables; if it is 1 or @code{--all-values}, print also their
28176 values; and if it is 2 or @code{--simple-values}, print the name,
28177 type and value for simple data types, and the name and type for arrays,
28178 structures and unions.
28180 Use of this command to obtain arguments in a single frame is
28181 deprecated in favor of the @samp{-stack-list-variables} command.
28183 @subsubheading @value{GDBN} Command
28185 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28186 @samp{gdb_get_args} command which partially overlaps with the
28187 functionality of @samp{-stack-list-arguments}.
28189 @subsubheading Example
28196 frame=@{level="0",addr="0x00010734",func="callee4",
28197 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28198 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28199 frame=@{level="1",addr="0x0001076c",func="callee3",
28200 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28201 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28202 frame=@{level="2",addr="0x0001078c",func="callee2",
28203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28204 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28205 frame=@{level="3",addr="0x000107b4",func="callee1",
28206 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28207 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28208 frame=@{level="4",addr="0x000107e0",func="main",
28209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28210 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28212 -stack-list-arguments 0
28215 frame=@{level="0",args=[]@},
28216 frame=@{level="1",args=[name="strarg"]@},
28217 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28218 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28219 frame=@{level="4",args=[]@}]
28221 -stack-list-arguments 1
28224 frame=@{level="0",args=[]@},
28226 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28227 frame=@{level="2",args=[
28228 @{name="intarg",value="2"@},
28229 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28230 @{frame=@{level="3",args=[
28231 @{name="intarg",value="2"@},
28232 @{name="strarg",value="0x11940 \"A string argument.\""@},
28233 @{name="fltarg",value="3.5"@}]@},
28234 frame=@{level="4",args=[]@}]
28236 -stack-list-arguments 0 2 2
28237 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28239 -stack-list-arguments 1 2 2
28240 ^done,stack-args=[frame=@{level="2",
28241 args=[@{name="intarg",value="2"@},
28242 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28246 @c @subheading -stack-list-exception-handlers
28249 @subheading The @code{-stack-list-frames} Command
28250 @findex -stack-list-frames
28252 @subsubheading Synopsis
28255 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28258 List the frames currently on the stack. For each frame it displays the
28263 The frame number, 0 being the topmost frame, i.e., the innermost function.
28265 The @code{$pc} value for that frame.
28269 File name of the source file where the function lives.
28270 @item @var{fullname}
28271 The full file name of the source file where the function lives.
28273 Line number corresponding to the @code{$pc}.
28275 The shared library where this function is defined. This is only given
28276 if the frame's function is not known.
28279 If invoked without arguments, this command prints a backtrace for the
28280 whole stack. If given two integer arguments, it shows the frames whose
28281 levels are between the two arguments (inclusive). If the two arguments
28282 are equal, it shows the single frame at the corresponding level. It is
28283 an error if @var{low-frame} is larger than the actual number of
28284 frames. On the other hand, @var{high-frame} may be larger than the
28285 actual number of frames, in which case only existing frames will be returned.
28287 @subsubheading @value{GDBN} Command
28289 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28291 @subsubheading Example
28293 Full stack backtrace:
28299 [frame=@{level="0",addr="0x0001076c",func="foo",
28300 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28301 frame=@{level="1",addr="0x000107a4",func="foo",
28302 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28303 frame=@{level="2",addr="0x000107a4",func="foo",
28304 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28305 frame=@{level="3",addr="0x000107a4",func="foo",
28306 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28307 frame=@{level="4",addr="0x000107a4",func="foo",
28308 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28309 frame=@{level="5",addr="0x000107a4",func="foo",
28310 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28311 frame=@{level="6",addr="0x000107a4",func="foo",
28312 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28313 frame=@{level="7",addr="0x000107a4",func="foo",
28314 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28315 frame=@{level="8",addr="0x000107a4",func="foo",
28316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28317 frame=@{level="9",addr="0x000107a4",func="foo",
28318 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28319 frame=@{level="10",addr="0x000107a4",func="foo",
28320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28321 frame=@{level="11",addr="0x00010738",func="main",
28322 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28326 Show frames between @var{low_frame} and @var{high_frame}:
28330 -stack-list-frames 3 5
28332 [frame=@{level="3",addr="0x000107a4",func="foo",
28333 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28334 frame=@{level="4",addr="0x000107a4",func="foo",
28335 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28336 frame=@{level="5",addr="0x000107a4",func="foo",
28337 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28341 Show a single frame:
28345 -stack-list-frames 3 3
28347 [frame=@{level="3",addr="0x000107a4",func="foo",
28348 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28353 @subheading The @code{-stack-list-locals} Command
28354 @findex -stack-list-locals
28356 @subsubheading Synopsis
28359 -stack-list-locals @var{print-values}
28362 Display the local variable names for the selected frame. If
28363 @var{print-values} is 0 or @code{--no-values}, print only the names of
28364 the variables; if it is 1 or @code{--all-values}, print also their
28365 values; and if it is 2 or @code{--simple-values}, print the name,
28366 type and value for simple data types, and the name and type for arrays,
28367 structures and unions. In this last case, a frontend can immediately
28368 display the value of simple data types and create variable objects for
28369 other data types when the user wishes to explore their values in
28372 This command is deprecated in favor of the
28373 @samp{-stack-list-variables} command.
28375 @subsubheading @value{GDBN} Command
28377 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28379 @subsubheading Example
28383 -stack-list-locals 0
28384 ^done,locals=[name="A",name="B",name="C"]
28386 -stack-list-locals --all-values
28387 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28388 @{name="C",value="@{1, 2, 3@}"@}]
28389 -stack-list-locals --simple-values
28390 ^done,locals=[@{name="A",type="int",value="1"@},
28391 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28395 @subheading The @code{-stack-list-variables} Command
28396 @findex -stack-list-variables
28398 @subsubheading Synopsis
28401 -stack-list-variables @var{print-values}
28404 Display the names of local variables and function arguments for the selected frame. If
28405 @var{print-values} is 0 or @code{--no-values}, print only the names of
28406 the variables; if it is 1 or @code{--all-values}, print also their
28407 values; and if it is 2 or @code{--simple-values}, print the name,
28408 type and value for simple data types, and the name and type for arrays,
28409 structures and unions.
28411 @subsubheading Example
28415 -stack-list-variables --thread 1 --frame 0 --all-values
28416 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28421 @subheading The @code{-stack-select-frame} Command
28422 @findex -stack-select-frame
28424 @subsubheading Synopsis
28427 -stack-select-frame @var{framenum}
28430 Change the selected frame. Select a different frame @var{framenum} on
28433 This command in deprecated in favor of passing the @samp{--frame}
28434 option to every command.
28436 @subsubheading @value{GDBN} Command
28438 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28439 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28441 @subsubheading Example
28445 -stack-select-frame 2
28450 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28451 @node GDB/MI Variable Objects
28452 @section @sc{gdb/mi} Variable Objects
28456 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28458 For the implementation of a variable debugger window (locals, watched
28459 expressions, etc.), we are proposing the adaptation of the existing code
28460 used by @code{Insight}.
28462 The two main reasons for that are:
28466 It has been proven in practice (it is already on its second generation).
28469 It will shorten development time (needless to say how important it is
28473 The original interface was designed to be used by Tcl code, so it was
28474 slightly changed so it could be used through @sc{gdb/mi}. This section
28475 describes the @sc{gdb/mi} operations that will be available and gives some
28476 hints about their use.
28478 @emph{Note}: In addition to the set of operations described here, we
28479 expect the @sc{gui} implementation of a variable window to require, at
28480 least, the following operations:
28483 @item @code{-gdb-show} @code{output-radix}
28484 @item @code{-stack-list-arguments}
28485 @item @code{-stack-list-locals}
28486 @item @code{-stack-select-frame}
28491 @subheading Introduction to Variable Objects
28493 @cindex variable objects in @sc{gdb/mi}
28495 Variable objects are "object-oriented" MI interface for examining and
28496 changing values of expressions. Unlike some other MI interfaces that
28497 work with expressions, variable objects are specifically designed for
28498 simple and efficient presentation in the frontend. A variable object
28499 is identified by string name. When a variable object is created, the
28500 frontend specifies the expression for that variable object. The
28501 expression can be a simple variable, or it can be an arbitrary complex
28502 expression, and can even involve CPU registers. After creating a
28503 variable object, the frontend can invoke other variable object
28504 operations---for example to obtain or change the value of a variable
28505 object, or to change display format.
28507 Variable objects have hierarchical tree structure. Any variable object
28508 that corresponds to a composite type, such as structure in C, has
28509 a number of child variable objects, for example corresponding to each
28510 element of a structure. A child variable object can itself have
28511 children, recursively. Recursion ends when we reach
28512 leaf variable objects, which always have built-in types. Child variable
28513 objects are created only by explicit request, so if a frontend
28514 is not interested in the children of a particular variable object, no
28515 child will be created.
28517 For a leaf variable object it is possible to obtain its value as a
28518 string, or set the value from a string. String value can be also
28519 obtained for a non-leaf variable object, but it's generally a string
28520 that only indicates the type of the object, and does not list its
28521 contents. Assignment to a non-leaf variable object is not allowed.
28523 A frontend does not need to read the values of all variable objects each time
28524 the program stops. Instead, MI provides an update command that lists all
28525 variable objects whose values has changed since the last update
28526 operation. This considerably reduces the amount of data that must
28527 be transferred to the frontend. As noted above, children variable
28528 objects are created on demand, and only leaf variable objects have a
28529 real value. As result, gdb will read target memory only for leaf
28530 variables that frontend has created.
28532 The automatic update is not always desirable. For example, a frontend
28533 might want to keep a value of some expression for future reference,
28534 and never update it. For another example, fetching memory is
28535 relatively slow for embedded targets, so a frontend might want
28536 to disable automatic update for the variables that are either not
28537 visible on the screen, or ``closed''. This is possible using so
28538 called ``frozen variable objects''. Such variable objects are never
28539 implicitly updated.
28541 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28542 fixed variable object, the expression is parsed when the variable
28543 object is created, including associating identifiers to specific
28544 variables. The meaning of expression never changes. For a floating
28545 variable object the values of variables whose names appear in the
28546 expressions are re-evaluated every time in the context of the current
28547 frame. Consider this example:
28552 struct work_state state;
28559 If a fixed variable object for the @code{state} variable is created in
28560 this function, and we enter the recursive call, the variable
28561 object will report the value of @code{state} in the top-level
28562 @code{do_work} invocation. On the other hand, a floating variable
28563 object will report the value of @code{state} in the current frame.
28565 If an expression specified when creating a fixed variable object
28566 refers to a local variable, the variable object becomes bound to the
28567 thread and frame in which the variable object is created. When such
28568 variable object is updated, @value{GDBN} makes sure that the
28569 thread/frame combination the variable object is bound to still exists,
28570 and re-evaluates the variable object in context of that thread/frame.
28572 The following is the complete set of @sc{gdb/mi} operations defined to
28573 access this functionality:
28575 @multitable @columnfractions .4 .6
28576 @item @strong{Operation}
28577 @tab @strong{Description}
28579 @item @code{-enable-pretty-printing}
28580 @tab enable Python-based pretty-printing
28581 @item @code{-var-create}
28582 @tab create a variable object
28583 @item @code{-var-delete}
28584 @tab delete the variable object and/or its children
28585 @item @code{-var-set-format}
28586 @tab set the display format of this variable
28587 @item @code{-var-show-format}
28588 @tab show the display format of this variable
28589 @item @code{-var-info-num-children}
28590 @tab tells how many children this object has
28591 @item @code{-var-list-children}
28592 @tab return a list of the object's children
28593 @item @code{-var-info-type}
28594 @tab show the type of this variable object
28595 @item @code{-var-info-expression}
28596 @tab print parent-relative expression that this variable object represents
28597 @item @code{-var-info-path-expression}
28598 @tab print full expression that this variable object represents
28599 @item @code{-var-show-attributes}
28600 @tab is this variable editable? does it exist here?
28601 @item @code{-var-evaluate-expression}
28602 @tab get the value of this variable
28603 @item @code{-var-assign}
28604 @tab set the value of this variable
28605 @item @code{-var-update}
28606 @tab update the variable and its children
28607 @item @code{-var-set-frozen}
28608 @tab set frozeness attribute
28609 @item @code{-var-set-update-range}
28610 @tab set range of children to display on update
28613 In the next subsection we describe each operation in detail and suggest
28614 how it can be used.
28616 @subheading Description And Use of Operations on Variable Objects
28618 @subheading The @code{-enable-pretty-printing} Command
28619 @findex -enable-pretty-printing
28622 -enable-pretty-printing
28625 @value{GDBN} allows Python-based visualizers to affect the output of the
28626 MI variable object commands. However, because there was no way to
28627 implement this in a fully backward-compatible way, a front end must
28628 request that this functionality be enabled.
28630 Once enabled, this feature cannot be disabled.
28632 Note that if Python support has not been compiled into @value{GDBN},
28633 this command will still succeed (and do nothing).
28635 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28636 may work differently in future versions of @value{GDBN}.
28638 @subheading The @code{-var-create} Command
28639 @findex -var-create
28641 @subsubheading Synopsis
28644 -var-create @{@var{name} | "-"@}
28645 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28648 This operation creates a variable object, which allows the monitoring of
28649 a variable, the result of an expression, a memory cell or a CPU
28652 The @var{name} parameter is the string by which the object can be
28653 referenced. It must be unique. If @samp{-} is specified, the varobj
28654 system will generate a string ``varNNNNNN'' automatically. It will be
28655 unique provided that one does not specify @var{name} of that format.
28656 The command fails if a duplicate name is found.
28658 The frame under which the expression should be evaluated can be
28659 specified by @var{frame-addr}. A @samp{*} indicates that the current
28660 frame should be used. A @samp{@@} indicates that a floating variable
28661 object must be created.
28663 @var{expression} is any expression valid on the current language set (must not
28664 begin with a @samp{*}), or one of the following:
28668 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28671 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28674 @samp{$@var{regname}} --- a CPU register name
28677 @cindex dynamic varobj
28678 A varobj's contents may be provided by a Python-based pretty-printer. In this
28679 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28680 have slightly different semantics in some cases. If the
28681 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28682 will never create a dynamic varobj. This ensures backward
28683 compatibility for existing clients.
28685 @subsubheading Result
28687 This operation returns attributes of the newly-created varobj. These
28692 The name of the varobj.
28695 The number of children of the varobj. This number is not necessarily
28696 reliable for a dynamic varobj. Instead, you must examine the
28697 @samp{has_more} attribute.
28700 The varobj's scalar value. For a varobj whose type is some sort of
28701 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28702 will not be interesting.
28705 The varobj's type. This is a string representation of the type, as
28706 would be printed by the @value{GDBN} CLI.
28709 If a variable object is bound to a specific thread, then this is the
28710 thread's identifier.
28713 For a dynamic varobj, this indicates whether there appear to be any
28714 children available. For a non-dynamic varobj, this will be 0.
28717 This attribute will be present and have the value @samp{1} if the
28718 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28719 then this attribute will not be present.
28722 A dynamic varobj can supply a display hint to the front end. The
28723 value comes directly from the Python pretty-printer object's
28724 @code{display_hint} method. @xref{Pretty Printing API}.
28727 Typical output will look like this:
28730 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28731 has_more="@var{has_more}"
28735 @subheading The @code{-var-delete} Command
28736 @findex -var-delete
28738 @subsubheading Synopsis
28741 -var-delete [ -c ] @var{name}
28744 Deletes a previously created variable object and all of its children.
28745 With the @samp{-c} option, just deletes the children.
28747 Returns an error if the object @var{name} is not found.
28750 @subheading The @code{-var-set-format} Command
28751 @findex -var-set-format
28753 @subsubheading Synopsis
28756 -var-set-format @var{name} @var{format-spec}
28759 Sets the output format for the value of the object @var{name} to be
28762 @anchor{-var-set-format}
28763 The syntax for the @var{format-spec} is as follows:
28766 @var{format-spec} @expansion{}
28767 @{binary | decimal | hexadecimal | octal | natural@}
28770 The natural format is the default format choosen automatically
28771 based on the variable type (like decimal for an @code{int}, hex
28772 for pointers, etc.).
28774 For a variable with children, the format is set only on the
28775 variable itself, and the children are not affected.
28777 @subheading The @code{-var-show-format} Command
28778 @findex -var-show-format
28780 @subsubheading Synopsis
28783 -var-show-format @var{name}
28786 Returns the format used to display the value of the object @var{name}.
28789 @var{format} @expansion{}
28794 @subheading The @code{-var-info-num-children} Command
28795 @findex -var-info-num-children
28797 @subsubheading Synopsis
28800 -var-info-num-children @var{name}
28803 Returns the number of children of a variable object @var{name}:
28809 Note that this number is not completely reliable for a dynamic varobj.
28810 It will return the current number of children, but more children may
28814 @subheading The @code{-var-list-children} Command
28815 @findex -var-list-children
28817 @subsubheading Synopsis
28820 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28822 @anchor{-var-list-children}
28824 Return a list of the children of the specified variable object and
28825 create variable objects for them, if they do not already exist. With
28826 a single argument or if @var{print-values} has a value of 0 or
28827 @code{--no-values}, print only the names of the variables; if
28828 @var{print-values} is 1 or @code{--all-values}, also print their
28829 values; and if it is 2 or @code{--simple-values} print the name and
28830 value for simple data types and just the name for arrays, structures
28833 @var{from} and @var{to}, if specified, indicate the range of children
28834 to report. If @var{from} or @var{to} is less than zero, the range is
28835 reset and all children will be reported. Otherwise, children starting
28836 at @var{from} (zero-based) and up to and excluding @var{to} will be
28839 If a child range is requested, it will only affect the current call to
28840 @code{-var-list-children}, but not future calls to @code{-var-update}.
28841 For this, you must instead use @code{-var-set-update-range}. The
28842 intent of this approach is to enable a front end to implement any
28843 update approach it likes; for example, scrolling a view may cause the
28844 front end to request more children with @code{-var-list-children}, and
28845 then the front end could call @code{-var-set-update-range} with a
28846 different range to ensure that future updates are restricted to just
28849 For each child the following results are returned:
28854 Name of the variable object created for this child.
28857 The expression to be shown to the user by the front end to designate this child.
28858 For example this may be the name of a structure member.
28860 For a dynamic varobj, this value cannot be used to form an
28861 expression. There is no way to do this at all with a dynamic varobj.
28863 For C/C@t{++} structures there are several pseudo children returned to
28864 designate access qualifiers. For these pseudo children @var{exp} is
28865 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28866 type and value are not present.
28868 A dynamic varobj will not report the access qualifying
28869 pseudo-children, regardless of the language. This information is not
28870 available at all with a dynamic varobj.
28873 Number of children this child has. For a dynamic varobj, this will be
28877 The type of the child.
28880 If values were requested, this is the value.
28883 If this variable object is associated with a thread, this is the thread id.
28884 Otherwise this result is not present.
28887 If the variable object is frozen, this variable will be present with a value of 1.
28890 The result may have its own attributes:
28894 A dynamic varobj can supply a display hint to the front end. The
28895 value comes directly from the Python pretty-printer object's
28896 @code{display_hint} method. @xref{Pretty Printing API}.
28899 This is an integer attribute which is nonzero if there are children
28900 remaining after the end of the selected range.
28903 @subsubheading Example
28907 -var-list-children n
28908 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28909 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28911 -var-list-children --all-values n
28912 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28913 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28917 @subheading The @code{-var-info-type} Command
28918 @findex -var-info-type
28920 @subsubheading Synopsis
28923 -var-info-type @var{name}
28926 Returns the type of the specified variable @var{name}. The type is
28927 returned as a string in the same format as it is output by the
28931 type=@var{typename}
28935 @subheading The @code{-var-info-expression} Command
28936 @findex -var-info-expression
28938 @subsubheading Synopsis
28941 -var-info-expression @var{name}
28944 Returns a string that is suitable for presenting this
28945 variable object in user interface. The string is generally
28946 not valid expression in the current language, and cannot be evaluated.
28948 For example, if @code{a} is an array, and variable object
28949 @code{A} was created for @code{a}, then we'll get this output:
28952 (gdb) -var-info-expression A.1
28953 ^done,lang="C",exp="1"
28957 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28959 Note that the output of the @code{-var-list-children} command also
28960 includes those expressions, so the @code{-var-info-expression} command
28963 @subheading The @code{-var-info-path-expression} Command
28964 @findex -var-info-path-expression
28966 @subsubheading Synopsis
28969 -var-info-path-expression @var{name}
28972 Returns an expression that can be evaluated in the current
28973 context and will yield the same value that a variable object has.
28974 Compare this with the @code{-var-info-expression} command, which
28975 result can be used only for UI presentation. Typical use of
28976 the @code{-var-info-path-expression} command is creating a
28977 watchpoint from a variable object.
28979 This command is currently not valid for children of a dynamic varobj,
28980 and will give an error when invoked on one.
28982 For example, suppose @code{C} is a C@t{++} class, derived from class
28983 @code{Base}, and that the @code{Base} class has a member called
28984 @code{m_size}. Assume a variable @code{c} is has the type of
28985 @code{C} and a variable object @code{C} was created for variable
28986 @code{c}. Then, we'll get this output:
28988 (gdb) -var-info-path-expression C.Base.public.m_size
28989 ^done,path_expr=((Base)c).m_size)
28992 @subheading The @code{-var-show-attributes} Command
28993 @findex -var-show-attributes
28995 @subsubheading Synopsis
28998 -var-show-attributes @var{name}
29001 List attributes of the specified variable object @var{name}:
29004 status=@var{attr} [ ( ,@var{attr} )* ]
29008 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29010 @subheading The @code{-var-evaluate-expression} Command
29011 @findex -var-evaluate-expression
29013 @subsubheading Synopsis
29016 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29019 Evaluates the expression that is represented by the specified variable
29020 object and returns its value as a string. The format of the string
29021 can be specified with the @samp{-f} option. The possible values of
29022 this option are the same as for @code{-var-set-format}
29023 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29024 the current display format will be used. The current display format
29025 can be changed using the @code{-var-set-format} command.
29031 Note that one must invoke @code{-var-list-children} for a variable
29032 before the value of a child variable can be evaluated.
29034 @subheading The @code{-var-assign} Command
29035 @findex -var-assign
29037 @subsubheading Synopsis
29040 -var-assign @var{name} @var{expression}
29043 Assigns the value of @var{expression} to the variable object specified
29044 by @var{name}. The object must be @samp{editable}. If the variable's
29045 value is altered by the assign, the variable will show up in any
29046 subsequent @code{-var-update} list.
29048 @subsubheading Example
29056 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29060 @subheading The @code{-var-update} Command
29061 @findex -var-update
29063 @subsubheading Synopsis
29066 -var-update [@var{print-values}] @{@var{name} | "*"@}
29069 Reevaluate the expressions corresponding to the variable object
29070 @var{name} and all its direct and indirect children, and return the
29071 list of variable objects whose values have changed; @var{name} must
29072 be a root variable object. Here, ``changed'' means that the result of
29073 @code{-var-evaluate-expression} before and after the
29074 @code{-var-update} is different. If @samp{*} is used as the variable
29075 object names, all existing variable objects are updated, except
29076 for frozen ones (@pxref{-var-set-frozen}). The option
29077 @var{print-values} determines whether both names and values, or just
29078 names are printed. The possible values of this option are the same
29079 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29080 recommended to use the @samp{--all-values} option, to reduce the
29081 number of MI commands needed on each program stop.
29083 With the @samp{*} parameter, if a variable object is bound to a
29084 currently running thread, it will not be updated, without any
29087 If @code{-var-set-update-range} was previously used on a varobj, then
29088 only the selected range of children will be reported.
29090 @code{-var-update} reports all the changed varobjs in a tuple named
29093 Each item in the change list is itself a tuple holding:
29097 The name of the varobj.
29100 If values were requested for this update, then this field will be
29101 present and will hold the value of the varobj.
29104 @anchor{-var-update}
29105 This field is a string which may take one of three values:
29109 The variable object's current value is valid.
29112 The variable object does not currently hold a valid value but it may
29113 hold one in the future if its associated expression comes back into
29117 The variable object no longer holds a valid value.
29118 This can occur when the executable file being debugged has changed,
29119 either through recompilation or by using the @value{GDBN} @code{file}
29120 command. The front end should normally choose to delete these variable
29124 In the future new values may be added to this list so the front should
29125 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29128 This is only present if the varobj is still valid. If the type
29129 changed, then this will be the string @samp{true}; otherwise it will
29133 If the varobj's type changed, then this field will be present and will
29136 @item new_num_children
29137 For a dynamic varobj, if the number of children changed, or if the
29138 type changed, this will be the new number of children.
29140 The @samp{numchild} field in other varobj responses is generally not
29141 valid for a dynamic varobj -- it will show the number of children that
29142 @value{GDBN} knows about, but because dynamic varobjs lazily
29143 instantiate their children, this will not reflect the number of
29144 children which may be available.
29146 The @samp{new_num_children} attribute only reports changes to the
29147 number of children known by @value{GDBN}. This is the only way to
29148 detect whether an update has removed children (which necessarily can
29149 only happen at the end of the update range).
29152 The display hint, if any.
29155 This is an integer value, which will be 1 if there are more children
29156 available outside the varobj's update range.
29159 This attribute will be present and have the value @samp{1} if the
29160 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29161 then this attribute will not be present.
29164 If new children were added to a dynamic varobj within the selected
29165 update range (as set by @code{-var-set-update-range}), then they will
29166 be listed in this attribute.
29169 @subsubheading Example
29176 -var-update --all-values var1
29177 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29178 type_changed="false"@}]
29182 @subheading The @code{-var-set-frozen} Command
29183 @findex -var-set-frozen
29184 @anchor{-var-set-frozen}
29186 @subsubheading Synopsis
29189 -var-set-frozen @var{name} @var{flag}
29192 Set the frozenness flag on the variable object @var{name}. The
29193 @var{flag} parameter should be either @samp{1} to make the variable
29194 frozen or @samp{0} to make it unfrozen. If a variable object is
29195 frozen, then neither itself, nor any of its children, are
29196 implicitly updated by @code{-var-update} of
29197 a parent variable or by @code{-var-update *}. Only
29198 @code{-var-update} of the variable itself will update its value and
29199 values of its children. After a variable object is unfrozen, it is
29200 implicitly updated by all subsequent @code{-var-update} operations.
29201 Unfreezing a variable does not update it, only subsequent
29202 @code{-var-update} does.
29204 @subsubheading Example
29208 -var-set-frozen V 1
29213 @subheading The @code{-var-set-update-range} command
29214 @findex -var-set-update-range
29215 @anchor{-var-set-update-range}
29217 @subsubheading Synopsis
29220 -var-set-update-range @var{name} @var{from} @var{to}
29223 Set the range of children to be returned by future invocations of
29224 @code{-var-update}.
29226 @var{from} and @var{to} indicate the range of children to report. If
29227 @var{from} or @var{to} is less than zero, the range is reset and all
29228 children will be reported. Otherwise, children starting at @var{from}
29229 (zero-based) and up to and excluding @var{to} will be reported.
29231 @subsubheading Example
29235 -var-set-update-range V 1 2
29239 @subheading The @code{-var-set-visualizer} command
29240 @findex -var-set-visualizer
29241 @anchor{-var-set-visualizer}
29243 @subsubheading Synopsis
29246 -var-set-visualizer @var{name} @var{visualizer}
29249 Set a visualizer for the variable object @var{name}.
29251 @var{visualizer} is the visualizer to use. The special value
29252 @samp{None} means to disable any visualizer in use.
29254 If not @samp{None}, @var{visualizer} must be a Python expression.
29255 This expression must evaluate to a callable object which accepts a
29256 single argument. @value{GDBN} will call this object with the value of
29257 the varobj @var{name} as an argument (this is done so that the same
29258 Python pretty-printing code can be used for both the CLI and MI).
29259 When called, this object must return an object which conforms to the
29260 pretty-printing interface (@pxref{Pretty Printing API}).
29262 The pre-defined function @code{gdb.default_visualizer} may be used to
29263 select a visualizer by following the built-in process
29264 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29265 a varobj is created, and so ordinarily is not needed.
29267 This feature is only available if Python support is enabled. The MI
29268 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29269 can be used to check this.
29271 @subsubheading Example
29273 Resetting the visualizer:
29277 -var-set-visualizer V None
29281 Reselecting the default (type-based) visualizer:
29285 -var-set-visualizer V gdb.default_visualizer
29289 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29290 can be used to instantiate this class for a varobj:
29294 -var-set-visualizer V "lambda val: SomeClass()"
29298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29299 @node GDB/MI Data Manipulation
29300 @section @sc{gdb/mi} Data Manipulation
29302 @cindex data manipulation, in @sc{gdb/mi}
29303 @cindex @sc{gdb/mi}, data manipulation
29304 This section describes the @sc{gdb/mi} commands that manipulate data:
29305 examine memory and registers, evaluate expressions, etc.
29307 @c REMOVED FROM THE INTERFACE.
29308 @c @subheading -data-assign
29309 @c Change the value of a program variable. Plenty of side effects.
29310 @c @subsubheading GDB Command
29312 @c @subsubheading Example
29315 @subheading The @code{-data-disassemble} Command
29316 @findex -data-disassemble
29318 @subsubheading Synopsis
29322 [ -s @var{start-addr} -e @var{end-addr} ]
29323 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29331 @item @var{start-addr}
29332 is the beginning address (or @code{$pc})
29333 @item @var{end-addr}
29335 @item @var{filename}
29336 is the name of the file to disassemble
29337 @item @var{linenum}
29338 is the line number to disassemble around
29340 is the number of disassembly lines to be produced. If it is -1,
29341 the whole function will be disassembled, in case no @var{end-addr} is
29342 specified. If @var{end-addr} is specified as a non-zero value, and
29343 @var{lines} is lower than the number of disassembly lines between
29344 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29345 displayed; if @var{lines} is higher than the number of lines between
29346 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29349 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29350 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29351 mixed source and disassembly with raw opcodes).
29354 @subsubheading Result
29356 The output for each instruction is composed of four fields:
29365 Note that whatever included in the instruction field, is not manipulated
29366 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29368 @subsubheading @value{GDBN} Command
29370 There's no direct mapping from this command to the CLI.
29372 @subsubheading Example
29374 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29378 -data-disassemble -s $pc -e "$pc + 20" -- 0
29381 @{address="0x000107c0",func-name="main",offset="4",
29382 inst="mov 2, %o0"@},
29383 @{address="0x000107c4",func-name="main",offset="8",
29384 inst="sethi %hi(0x11800), %o2"@},
29385 @{address="0x000107c8",func-name="main",offset="12",
29386 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29387 @{address="0x000107cc",func-name="main",offset="16",
29388 inst="sethi %hi(0x11800), %o2"@},
29389 @{address="0x000107d0",func-name="main",offset="20",
29390 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29394 Disassemble the whole @code{main} function. Line 32 is part of
29398 -data-disassemble -f basics.c -l 32 -- 0
29400 @{address="0x000107bc",func-name="main",offset="0",
29401 inst="save %sp, -112, %sp"@},
29402 @{address="0x000107c0",func-name="main",offset="4",
29403 inst="mov 2, %o0"@},
29404 @{address="0x000107c4",func-name="main",offset="8",
29405 inst="sethi %hi(0x11800), %o2"@},
29407 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29408 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29412 Disassemble 3 instructions from the start of @code{main}:
29416 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29418 @{address="0x000107bc",func-name="main",offset="0",
29419 inst="save %sp, -112, %sp"@},
29420 @{address="0x000107c0",func-name="main",offset="4",
29421 inst="mov 2, %o0"@},
29422 @{address="0x000107c4",func-name="main",offset="8",
29423 inst="sethi %hi(0x11800), %o2"@}]
29427 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29431 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29433 src_and_asm_line=@{line="31",
29434 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29435 testsuite/gdb.mi/basics.c",line_asm_insn=[
29436 @{address="0x000107bc",func-name="main",offset="0",
29437 inst="save %sp, -112, %sp"@}]@},
29438 src_and_asm_line=@{line="32",
29439 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29440 testsuite/gdb.mi/basics.c",line_asm_insn=[
29441 @{address="0x000107c0",func-name="main",offset="4",
29442 inst="mov 2, %o0"@},
29443 @{address="0x000107c4",func-name="main",offset="8",
29444 inst="sethi %hi(0x11800), %o2"@}]@}]
29449 @subheading The @code{-data-evaluate-expression} Command
29450 @findex -data-evaluate-expression
29452 @subsubheading Synopsis
29455 -data-evaluate-expression @var{expr}
29458 Evaluate @var{expr} as an expression. The expression could contain an
29459 inferior function call. The function call will execute synchronously.
29460 If the expression contains spaces, it must be enclosed in double quotes.
29462 @subsubheading @value{GDBN} Command
29464 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29465 @samp{call}. In @code{gdbtk} only, there's a corresponding
29466 @samp{gdb_eval} command.
29468 @subsubheading Example
29470 In the following example, the numbers that precede the commands are the
29471 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29472 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29476 211-data-evaluate-expression A
29479 311-data-evaluate-expression &A
29480 311^done,value="0xefffeb7c"
29482 411-data-evaluate-expression A+3
29485 511-data-evaluate-expression "A + 3"
29491 @subheading The @code{-data-list-changed-registers} Command
29492 @findex -data-list-changed-registers
29494 @subsubheading Synopsis
29497 -data-list-changed-registers
29500 Display a list of the registers that have changed.
29502 @subsubheading @value{GDBN} Command
29504 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29505 has the corresponding command @samp{gdb_changed_register_list}.
29507 @subsubheading Example
29509 On a PPC MBX board:
29517 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29518 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29521 -data-list-changed-registers
29522 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29523 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29524 "24","25","26","27","28","30","31","64","65","66","67","69"]
29529 @subheading The @code{-data-list-register-names} Command
29530 @findex -data-list-register-names
29532 @subsubheading Synopsis
29535 -data-list-register-names [ ( @var{regno} )+ ]
29538 Show a list of register names for the current target. If no arguments
29539 are given, it shows a list of the names of all the registers. If
29540 integer numbers are given as arguments, it will print a list of the
29541 names of the registers corresponding to the arguments. To ensure
29542 consistency between a register name and its number, the output list may
29543 include empty register names.
29545 @subsubheading @value{GDBN} Command
29547 @value{GDBN} does not have a command which corresponds to
29548 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29549 corresponding command @samp{gdb_regnames}.
29551 @subsubheading Example
29553 For the PPC MBX board:
29556 -data-list-register-names
29557 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29558 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29559 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29560 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29561 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29562 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29563 "", "pc","ps","cr","lr","ctr","xer"]
29565 -data-list-register-names 1 2 3
29566 ^done,register-names=["r1","r2","r3"]
29570 @subheading The @code{-data-list-register-values} Command
29571 @findex -data-list-register-values
29573 @subsubheading Synopsis
29576 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29579 Display the registers' contents. @var{fmt} is the format according to
29580 which the registers' contents are to be returned, followed by an optional
29581 list of numbers specifying the registers to display. A missing list of
29582 numbers indicates that the contents of all the registers must be returned.
29584 Allowed formats for @var{fmt} are:
29601 @subsubheading @value{GDBN} Command
29603 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29604 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29606 @subsubheading Example
29608 For a PPC MBX board (note: line breaks are for readability only, they
29609 don't appear in the actual output):
29613 -data-list-register-values r 64 65
29614 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29615 @{number="65",value="0x00029002"@}]
29617 -data-list-register-values x
29618 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29619 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29620 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29621 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29622 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29623 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29624 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29625 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29626 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29627 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29628 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29629 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29630 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29631 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29632 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29633 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29634 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29635 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29636 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29637 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29638 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29639 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29640 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29641 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29642 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29643 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29644 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29645 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29646 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29647 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29648 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29649 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29650 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29651 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29652 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29653 @{number="69",value="0x20002b03"@}]
29658 @subheading The @code{-data-read-memory} Command
29659 @findex -data-read-memory
29661 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29663 @subsubheading Synopsis
29666 -data-read-memory [ -o @var{byte-offset} ]
29667 @var{address} @var{word-format} @var{word-size}
29668 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29675 @item @var{address}
29676 An expression specifying the address of the first memory word to be
29677 read. Complex expressions containing embedded white space should be
29678 quoted using the C convention.
29680 @item @var{word-format}
29681 The format to be used to print the memory words. The notation is the
29682 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29685 @item @var{word-size}
29686 The size of each memory word in bytes.
29688 @item @var{nr-rows}
29689 The number of rows in the output table.
29691 @item @var{nr-cols}
29692 The number of columns in the output table.
29695 If present, indicates that each row should include an @sc{ascii} dump. The
29696 value of @var{aschar} is used as a padding character when a byte is not a
29697 member of the printable @sc{ascii} character set (printable @sc{ascii}
29698 characters are those whose code is between 32 and 126, inclusively).
29700 @item @var{byte-offset}
29701 An offset to add to the @var{address} before fetching memory.
29704 This command displays memory contents as a table of @var{nr-rows} by
29705 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29706 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29707 (returned as @samp{total-bytes}). Should less than the requested number
29708 of bytes be returned by the target, the missing words are identified
29709 using @samp{N/A}. The number of bytes read from the target is returned
29710 in @samp{nr-bytes} and the starting address used to read memory in
29713 The address of the next/previous row or page is available in
29714 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29717 @subsubheading @value{GDBN} Command
29719 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29720 @samp{gdb_get_mem} memory read command.
29722 @subsubheading Example
29724 Read six bytes of memory starting at @code{bytes+6} but then offset by
29725 @code{-6} bytes. Format as three rows of two columns. One byte per
29726 word. Display each word in hex.
29730 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29731 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29732 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29733 prev-page="0x0000138a",memory=[
29734 @{addr="0x00001390",data=["0x00","0x01"]@},
29735 @{addr="0x00001392",data=["0x02","0x03"]@},
29736 @{addr="0x00001394",data=["0x04","0x05"]@}]
29740 Read two bytes of memory starting at address @code{shorts + 64} and
29741 display as a single word formatted in decimal.
29745 5-data-read-memory shorts+64 d 2 1 1
29746 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29747 next-row="0x00001512",prev-row="0x0000150e",
29748 next-page="0x00001512",prev-page="0x0000150e",memory=[
29749 @{addr="0x00001510",data=["128"]@}]
29753 Read thirty two bytes of memory starting at @code{bytes+16} and format
29754 as eight rows of four columns. Include a string encoding with @samp{x}
29755 used as the non-printable character.
29759 4-data-read-memory bytes+16 x 1 8 4 x
29760 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29761 next-row="0x000013c0",prev-row="0x0000139c",
29762 next-page="0x000013c0",prev-page="0x00001380",memory=[
29763 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29764 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29765 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29766 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29767 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29768 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29769 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29770 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29774 @subheading The @code{-data-read-memory-bytes} Command
29775 @findex -data-read-memory-bytes
29777 @subsubheading Synopsis
29780 -data-read-memory-bytes [ -o @var{byte-offset} ]
29781 @var{address} @var{count}
29788 @item @var{address}
29789 An expression specifying the address of the first memory word to be
29790 read. Complex expressions containing embedded white space should be
29791 quoted using the C convention.
29794 The number of bytes to read. This should be an integer literal.
29796 @item @var{byte-offset}
29797 The offsets in bytes relative to @var{address} at which to start
29798 reading. This should be an integer literal. This option is provided
29799 so that a frontend is not required to first evaluate address and then
29800 perform address arithmetics itself.
29804 This command attempts to read all accessible memory regions in the
29805 specified range. First, all regions marked as unreadable in the memory
29806 map (if one is defined) will be skipped. @xref{Memory Region
29807 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29808 regions. For each one, if reading full region results in an errors,
29809 @value{GDBN} will try to read a subset of the region.
29811 In general, every single byte in the region may be readable or not,
29812 and the only way to read every readable byte is to try a read at
29813 every address, which is not practical. Therefore, @value{GDBN} will
29814 attempt to read all accessible bytes at either beginning or the end
29815 of the region, using a binary division scheme. This heuristic works
29816 well for reading accross a memory map boundary. Note that if a region
29817 has a readable range that is neither at the beginning or the end,
29818 @value{GDBN} will not read it.
29820 The result record (@pxref{GDB/MI Result Records}) that is output of
29821 the command includes a field named @samp{memory} whose content is a
29822 list of tuples. Each tuple represent a successfully read memory block
29823 and has the following fields:
29827 The start address of the memory block, as hexadecimal literal.
29830 The end address of the memory block, as hexadecimal literal.
29833 The offset of the memory block, as hexadecimal literal, relative to
29834 the start address passed to @code{-data-read-memory-bytes}.
29837 The contents of the memory block, in hex.
29843 @subsubheading @value{GDBN} Command
29845 The corresponding @value{GDBN} command is @samp{x}.
29847 @subsubheading Example
29851 -data-read-memory-bytes &a 10
29852 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29854 contents="01000000020000000300"@}]
29859 @subheading The @code{-data-write-memory-bytes} Command
29860 @findex -data-write-memory-bytes
29862 @subsubheading Synopsis
29865 -data-write-memory-bytes @var{address} @var{contents}
29872 @item @var{address}
29873 An expression specifying the address of the first memory word to be
29874 read. Complex expressions containing embedded white space should be
29875 quoted using the C convention.
29877 @item @var{contents}
29878 The hex-encoded bytes to write.
29882 @subsubheading @value{GDBN} Command
29884 There's no corresponding @value{GDBN} command.
29886 @subsubheading Example
29890 -data-write-memory-bytes &a "aabbccdd"
29896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29897 @node GDB/MI Tracepoint Commands
29898 @section @sc{gdb/mi} Tracepoint Commands
29900 The commands defined in this section implement MI support for
29901 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29903 @subheading The @code{-trace-find} Command
29904 @findex -trace-find
29906 @subsubheading Synopsis
29909 -trace-find @var{mode} [@var{parameters}@dots{}]
29912 Find a trace frame using criteria defined by @var{mode} and
29913 @var{parameters}. The following table lists permissible
29914 modes and their parameters. For details of operation, see @ref{tfind}.
29919 No parameters are required. Stops examining trace frames.
29922 An integer is required as parameter. Selects tracepoint frame with
29925 @item tracepoint-number
29926 An integer is required as parameter. Finds next
29927 trace frame that corresponds to tracepoint with the specified number.
29930 An address is required as parameter. Finds
29931 next trace frame that corresponds to any tracepoint at the specified
29934 @item pc-inside-range
29935 Two addresses are required as parameters. Finds next trace
29936 frame that corresponds to a tracepoint at an address inside the
29937 specified range. Both bounds are considered to be inside the range.
29939 @item pc-outside-range
29940 Two addresses are required as parameters. Finds
29941 next trace frame that corresponds to a tracepoint at an address outside
29942 the specified range. Both bounds are considered to be inside the range.
29945 Line specification is required as parameter. @xref{Specify Location}.
29946 Finds next trace frame that corresponds to a tracepoint at
29947 the specified location.
29951 If @samp{none} was passed as @var{mode}, the response does not
29952 have fields. Otherwise, the response may have the following fields:
29956 This field has either @samp{0} or @samp{1} as the value, depending
29957 on whether a matching tracepoint was found.
29960 The index of the found traceframe. This field is present iff
29961 the @samp{found} field has value of @samp{1}.
29964 The index of the found tracepoint. This field is present iff
29965 the @samp{found} field has value of @samp{1}.
29968 The information about the frame corresponding to the found trace
29969 frame. This field is present only if a trace frame was found.
29970 @xref{GDB/MI Frame Information}, for description of this field.
29974 @subsubheading @value{GDBN} Command
29976 The corresponding @value{GDBN} command is @samp{tfind}.
29978 @subheading -trace-define-variable
29979 @findex -trace-define-variable
29981 @subsubheading Synopsis
29984 -trace-define-variable @var{name} [ @var{value} ]
29987 Create trace variable @var{name} if it does not exist. If
29988 @var{value} is specified, sets the initial value of the specified
29989 trace variable to that value. Note that the @var{name} should start
29990 with the @samp{$} character.
29992 @subsubheading @value{GDBN} Command
29994 The corresponding @value{GDBN} command is @samp{tvariable}.
29996 @subheading -trace-list-variables
29997 @findex -trace-list-variables
29999 @subsubheading Synopsis
30002 -trace-list-variables
30005 Return a table of all defined trace variables. Each element of the
30006 table has the following fields:
30010 The name of the trace variable. This field is always present.
30013 The initial value. This is a 64-bit signed integer. This
30014 field is always present.
30017 The value the trace variable has at the moment. This is a 64-bit
30018 signed integer. This field is absent iff current value is
30019 not defined, for example if the trace was never run, or is
30024 @subsubheading @value{GDBN} Command
30026 The corresponding @value{GDBN} command is @samp{tvariables}.
30028 @subsubheading Example
30032 -trace-list-variables
30033 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30034 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30035 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30036 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30037 body=[variable=@{name="$trace_timestamp",initial="0"@}
30038 variable=@{name="$foo",initial="10",current="15"@}]@}
30042 @subheading -trace-save
30043 @findex -trace-save
30045 @subsubheading Synopsis
30048 -trace-save [-r ] @var{filename}
30051 Saves the collected trace data to @var{filename}. Without the
30052 @samp{-r} option, the data is downloaded from the target and saved
30053 in a local file. With the @samp{-r} option the target is asked
30054 to perform the save.
30056 @subsubheading @value{GDBN} Command
30058 The corresponding @value{GDBN} command is @samp{tsave}.
30061 @subheading -trace-start
30062 @findex -trace-start
30064 @subsubheading Synopsis
30070 Starts a tracing experiments. The result of this command does not
30073 @subsubheading @value{GDBN} Command
30075 The corresponding @value{GDBN} command is @samp{tstart}.
30077 @subheading -trace-status
30078 @findex -trace-status
30080 @subsubheading Synopsis
30086 Obtains the status of a tracing experiment. The result may include
30087 the following fields:
30092 May have a value of either @samp{0}, when no tracing operations are
30093 supported, @samp{1}, when all tracing operations are supported, or
30094 @samp{file} when examining trace file. In the latter case, examining
30095 of trace frame is possible but new tracing experiement cannot be
30096 started. This field is always present.
30099 May have a value of either @samp{0} or @samp{1} depending on whether
30100 tracing experiement is in progress on target. This field is present
30101 if @samp{supported} field is not @samp{0}.
30104 Report the reason why the tracing was stopped last time. This field
30105 may be absent iff tracing was never stopped on target yet. The
30106 value of @samp{request} means the tracing was stopped as result of
30107 the @code{-trace-stop} command. The value of @samp{overflow} means
30108 the tracing buffer is full. The value of @samp{disconnection} means
30109 tracing was automatically stopped when @value{GDBN} has disconnected.
30110 The value of @samp{passcount} means tracing was stopped when a
30111 tracepoint was passed a maximal number of times for that tracepoint.
30112 This field is present if @samp{supported} field is not @samp{0}.
30114 @item stopping-tracepoint
30115 The number of tracepoint whose passcount as exceeded. This field is
30116 present iff the @samp{stop-reason} field has the value of
30120 @itemx frames-created
30121 The @samp{frames} field is a count of the total number of trace frames
30122 in the trace buffer, while @samp{frames-created} is the total created
30123 during the run, including ones that were discarded, such as when a
30124 circular trace buffer filled up. Both fields are optional.
30128 These fields tell the current size of the tracing buffer and the
30129 remaining space. These fields are optional.
30132 The value of the circular trace buffer flag. @code{1} means that the
30133 trace buffer is circular and old trace frames will be discarded if
30134 necessary to make room, @code{0} means that the trace buffer is linear
30138 The value of the disconnected tracing flag. @code{1} means that
30139 tracing will continue after @value{GDBN} disconnects, @code{0} means
30140 that the trace run will stop.
30144 @subsubheading @value{GDBN} Command
30146 The corresponding @value{GDBN} command is @samp{tstatus}.
30148 @subheading -trace-stop
30149 @findex -trace-stop
30151 @subsubheading Synopsis
30157 Stops a tracing experiment. The result of this command has the same
30158 fields as @code{-trace-status}, except that the @samp{supported} and
30159 @samp{running} fields are not output.
30161 @subsubheading @value{GDBN} Command
30163 The corresponding @value{GDBN} command is @samp{tstop}.
30166 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30167 @node GDB/MI Symbol Query
30168 @section @sc{gdb/mi} Symbol Query Commands
30172 @subheading The @code{-symbol-info-address} Command
30173 @findex -symbol-info-address
30175 @subsubheading Synopsis
30178 -symbol-info-address @var{symbol}
30181 Describe where @var{symbol} is stored.
30183 @subsubheading @value{GDBN} Command
30185 The corresponding @value{GDBN} command is @samp{info address}.
30187 @subsubheading Example
30191 @subheading The @code{-symbol-info-file} Command
30192 @findex -symbol-info-file
30194 @subsubheading Synopsis
30200 Show the file for the symbol.
30202 @subsubheading @value{GDBN} Command
30204 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30205 @samp{gdb_find_file}.
30207 @subsubheading Example
30211 @subheading The @code{-symbol-info-function} Command
30212 @findex -symbol-info-function
30214 @subsubheading Synopsis
30217 -symbol-info-function
30220 Show which function the symbol lives in.
30222 @subsubheading @value{GDBN} Command
30224 @samp{gdb_get_function} in @code{gdbtk}.
30226 @subsubheading Example
30230 @subheading The @code{-symbol-info-line} Command
30231 @findex -symbol-info-line
30233 @subsubheading Synopsis
30239 Show the core addresses of the code for a source line.
30241 @subsubheading @value{GDBN} Command
30243 The corresponding @value{GDBN} command is @samp{info line}.
30244 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30246 @subsubheading Example
30250 @subheading The @code{-symbol-info-symbol} Command
30251 @findex -symbol-info-symbol
30253 @subsubheading Synopsis
30256 -symbol-info-symbol @var{addr}
30259 Describe what symbol is at location @var{addr}.
30261 @subsubheading @value{GDBN} Command
30263 The corresponding @value{GDBN} command is @samp{info symbol}.
30265 @subsubheading Example
30269 @subheading The @code{-symbol-list-functions} Command
30270 @findex -symbol-list-functions
30272 @subsubheading Synopsis
30275 -symbol-list-functions
30278 List the functions in the executable.
30280 @subsubheading @value{GDBN} Command
30282 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30283 @samp{gdb_search} in @code{gdbtk}.
30285 @subsubheading Example
30290 @subheading The @code{-symbol-list-lines} Command
30291 @findex -symbol-list-lines
30293 @subsubheading Synopsis
30296 -symbol-list-lines @var{filename}
30299 Print the list of lines that contain code and their associated program
30300 addresses for the given source filename. The entries are sorted in
30301 ascending PC order.
30303 @subsubheading @value{GDBN} Command
30305 There is no corresponding @value{GDBN} command.
30307 @subsubheading Example
30310 -symbol-list-lines basics.c
30311 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30317 @subheading The @code{-symbol-list-types} Command
30318 @findex -symbol-list-types
30320 @subsubheading Synopsis
30326 List all the type names.
30328 @subsubheading @value{GDBN} Command
30330 The corresponding commands are @samp{info types} in @value{GDBN},
30331 @samp{gdb_search} in @code{gdbtk}.
30333 @subsubheading Example
30337 @subheading The @code{-symbol-list-variables} Command
30338 @findex -symbol-list-variables
30340 @subsubheading Synopsis
30343 -symbol-list-variables
30346 List all the global and static variable names.
30348 @subsubheading @value{GDBN} Command
30350 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30352 @subsubheading Example
30356 @subheading The @code{-symbol-locate} Command
30357 @findex -symbol-locate
30359 @subsubheading Synopsis
30365 @subsubheading @value{GDBN} Command
30367 @samp{gdb_loc} in @code{gdbtk}.
30369 @subsubheading Example
30373 @subheading The @code{-symbol-type} Command
30374 @findex -symbol-type
30376 @subsubheading Synopsis
30379 -symbol-type @var{variable}
30382 Show type of @var{variable}.
30384 @subsubheading @value{GDBN} Command
30386 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30387 @samp{gdb_obj_variable}.
30389 @subsubheading Example
30394 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30395 @node GDB/MI File Commands
30396 @section @sc{gdb/mi} File Commands
30398 This section describes the GDB/MI commands to specify executable file names
30399 and to read in and obtain symbol table information.
30401 @subheading The @code{-file-exec-and-symbols} Command
30402 @findex -file-exec-and-symbols
30404 @subsubheading Synopsis
30407 -file-exec-and-symbols @var{file}
30410 Specify the executable file to be debugged. This file is the one from
30411 which the symbol table is also read. If no file is specified, the
30412 command clears the executable and symbol information. If breakpoints
30413 are set when using this command with no arguments, @value{GDBN} will produce
30414 error messages. Otherwise, no output is produced, except a completion
30417 @subsubheading @value{GDBN} Command
30419 The corresponding @value{GDBN} command is @samp{file}.
30421 @subsubheading Example
30425 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30431 @subheading The @code{-file-exec-file} Command
30432 @findex -file-exec-file
30434 @subsubheading Synopsis
30437 -file-exec-file @var{file}
30440 Specify the executable file to be debugged. Unlike
30441 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30442 from this file. If used without argument, @value{GDBN} clears the information
30443 about the executable file. No output is produced, except a completion
30446 @subsubheading @value{GDBN} Command
30448 The corresponding @value{GDBN} command is @samp{exec-file}.
30450 @subsubheading Example
30454 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30461 @subheading The @code{-file-list-exec-sections} Command
30462 @findex -file-list-exec-sections
30464 @subsubheading Synopsis
30467 -file-list-exec-sections
30470 List the sections of the current executable file.
30472 @subsubheading @value{GDBN} Command
30474 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30475 information as this command. @code{gdbtk} has a corresponding command
30476 @samp{gdb_load_info}.
30478 @subsubheading Example
30483 @subheading The @code{-file-list-exec-source-file} Command
30484 @findex -file-list-exec-source-file
30486 @subsubheading Synopsis
30489 -file-list-exec-source-file
30492 List the line number, the current source file, and the absolute path
30493 to the current source file for the current executable. The macro
30494 information field has a value of @samp{1} or @samp{0} depending on
30495 whether or not the file includes preprocessor macro information.
30497 @subsubheading @value{GDBN} Command
30499 The @value{GDBN} equivalent is @samp{info source}
30501 @subsubheading Example
30505 123-file-list-exec-source-file
30506 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30511 @subheading The @code{-file-list-exec-source-files} Command
30512 @findex -file-list-exec-source-files
30514 @subsubheading Synopsis
30517 -file-list-exec-source-files
30520 List the source files for the current executable.
30522 It will always output the filename, but only when @value{GDBN} can find
30523 the absolute file name of a source file, will it output the fullname.
30525 @subsubheading @value{GDBN} Command
30527 The @value{GDBN} equivalent is @samp{info sources}.
30528 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30530 @subsubheading Example
30533 -file-list-exec-source-files
30535 @{file=foo.c,fullname=/home/foo.c@},
30536 @{file=/home/bar.c,fullname=/home/bar.c@},
30537 @{file=gdb_could_not_find_fullpath.c@}]
30542 @subheading The @code{-file-list-shared-libraries} Command
30543 @findex -file-list-shared-libraries
30545 @subsubheading Synopsis
30548 -file-list-shared-libraries
30551 List the shared libraries in the program.
30553 @subsubheading @value{GDBN} Command
30555 The corresponding @value{GDBN} command is @samp{info shared}.
30557 @subsubheading Example
30561 @subheading The @code{-file-list-symbol-files} Command
30562 @findex -file-list-symbol-files
30564 @subsubheading Synopsis
30567 -file-list-symbol-files
30572 @subsubheading @value{GDBN} Command
30574 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30576 @subsubheading Example
30581 @subheading The @code{-file-symbol-file} Command
30582 @findex -file-symbol-file
30584 @subsubheading Synopsis
30587 -file-symbol-file @var{file}
30590 Read symbol table info from the specified @var{file} argument. When
30591 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30592 produced, except for a completion notification.
30594 @subsubheading @value{GDBN} Command
30596 The corresponding @value{GDBN} command is @samp{symbol-file}.
30598 @subsubheading Example
30602 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30608 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30609 @node GDB/MI Memory Overlay Commands
30610 @section @sc{gdb/mi} Memory Overlay Commands
30612 The memory overlay commands are not implemented.
30614 @c @subheading -overlay-auto
30616 @c @subheading -overlay-list-mapping-state
30618 @c @subheading -overlay-list-overlays
30620 @c @subheading -overlay-map
30622 @c @subheading -overlay-off
30624 @c @subheading -overlay-on
30626 @c @subheading -overlay-unmap
30628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30629 @node GDB/MI Signal Handling Commands
30630 @section @sc{gdb/mi} Signal Handling Commands
30632 Signal handling commands are not implemented.
30634 @c @subheading -signal-handle
30636 @c @subheading -signal-list-handle-actions
30638 @c @subheading -signal-list-signal-types
30642 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30643 @node GDB/MI Target Manipulation
30644 @section @sc{gdb/mi} Target Manipulation Commands
30647 @subheading The @code{-target-attach} Command
30648 @findex -target-attach
30650 @subsubheading Synopsis
30653 -target-attach @var{pid} | @var{gid} | @var{file}
30656 Attach to a process @var{pid} or a file @var{file} outside of
30657 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30658 group, the id previously returned by
30659 @samp{-list-thread-groups --available} must be used.
30661 @subsubheading @value{GDBN} Command
30663 The corresponding @value{GDBN} command is @samp{attach}.
30665 @subsubheading Example
30669 =thread-created,id="1"
30670 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30676 @subheading The @code{-target-compare-sections} Command
30677 @findex -target-compare-sections
30679 @subsubheading Synopsis
30682 -target-compare-sections [ @var{section} ]
30685 Compare data of section @var{section} on target to the exec file.
30686 Without the argument, all sections are compared.
30688 @subsubheading @value{GDBN} Command
30690 The @value{GDBN} equivalent is @samp{compare-sections}.
30692 @subsubheading Example
30697 @subheading The @code{-target-detach} Command
30698 @findex -target-detach
30700 @subsubheading Synopsis
30703 -target-detach [ @var{pid} | @var{gid} ]
30706 Detach from the remote target which normally resumes its execution.
30707 If either @var{pid} or @var{gid} is specified, detaches from either
30708 the specified process, or specified thread group. There's no output.
30710 @subsubheading @value{GDBN} Command
30712 The corresponding @value{GDBN} command is @samp{detach}.
30714 @subsubheading Example
30724 @subheading The @code{-target-disconnect} Command
30725 @findex -target-disconnect
30727 @subsubheading Synopsis
30733 Disconnect from the remote target. There's no output and the target is
30734 generally not resumed.
30736 @subsubheading @value{GDBN} Command
30738 The corresponding @value{GDBN} command is @samp{disconnect}.
30740 @subsubheading Example
30750 @subheading The @code{-target-download} Command
30751 @findex -target-download
30753 @subsubheading Synopsis
30759 Loads the executable onto the remote target.
30760 It prints out an update message every half second, which includes the fields:
30764 The name of the section.
30766 The size of what has been sent so far for that section.
30768 The size of the section.
30770 The total size of what was sent so far (the current and the previous sections).
30772 The size of the overall executable to download.
30776 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30777 @sc{gdb/mi} Output Syntax}).
30779 In addition, it prints the name and size of the sections, as they are
30780 downloaded. These messages include the following fields:
30784 The name of the section.
30786 The size of the section.
30788 The size of the overall executable to download.
30792 At the end, a summary is printed.
30794 @subsubheading @value{GDBN} Command
30796 The corresponding @value{GDBN} command is @samp{load}.
30798 @subsubheading Example
30800 Note: each status message appears on a single line. Here the messages
30801 have been broken down so that they can fit onto a page.
30806 +download,@{section=".text",section-size="6668",total-size="9880"@}
30807 +download,@{section=".text",section-sent="512",section-size="6668",
30808 total-sent="512",total-size="9880"@}
30809 +download,@{section=".text",section-sent="1024",section-size="6668",
30810 total-sent="1024",total-size="9880"@}
30811 +download,@{section=".text",section-sent="1536",section-size="6668",
30812 total-sent="1536",total-size="9880"@}
30813 +download,@{section=".text",section-sent="2048",section-size="6668",
30814 total-sent="2048",total-size="9880"@}
30815 +download,@{section=".text",section-sent="2560",section-size="6668",
30816 total-sent="2560",total-size="9880"@}
30817 +download,@{section=".text",section-sent="3072",section-size="6668",
30818 total-sent="3072",total-size="9880"@}
30819 +download,@{section=".text",section-sent="3584",section-size="6668",
30820 total-sent="3584",total-size="9880"@}
30821 +download,@{section=".text",section-sent="4096",section-size="6668",
30822 total-sent="4096",total-size="9880"@}
30823 +download,@{section=".text",section-sent="4608",section-size="6668",
30824 total-sent="4608",total-size="9880"@}
30825 +download,@{section=".text",section-sent="5120",section-size="6668",
30826 total-sent="5120",total-size="9880"@}
30827 +download,@{section=".text",section-sent="5632",section-size="6668",
30828 total-sent="5632",total-size="9880"@}
30829 +download,@{section=".text",section-sent="6144",section-size="6668",
30830 total-sent="6144",total-size="9880"@}
30831 +download,@{section=".text",section-sent="6656",section-size="6668",
30832 total-sent="6656",total-size="9880"@}
30833 +download,@{section=".init",section-size="28",total-size="9880"@}
30834 +download,@{section=".fini",section-size="28",total-size="9880"@}
30835 +download,@{section=".data",section-size="3156",total-size="9880"@}
30836 +download,@{section=".data",section-sent="512",section-size="3156",
30837 total-sent="7236",total-size="9880"@}
30838 +download,@{section=".data",section-sent="1024",section-size="3156",
30839 total-sent="7748",total-size="9880"@}
30840 +download,@{section=".data",section-sent="1536",section-size="3156",
30841 total-sent="8260",total-size="9880"@}
30842 +download,@{section=".data",section-sent="2048",section-size="3156",
30843 total-sent="8772",total-size="9880"@}
30844 +download,@{section=".data",section-sent="2560",section-size="3156",
30845 total-sent="9284",total-size="9880"@}
30846 +download,@{section=".data",section-sent="3072",section-size="3156",
30847 total-sent="9796",total-size="9880"@}
30848 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30855 @subheading The @code{-target-exec-status} Command
30856 @findex -target-exec-status
30858 @subsubheading Synopsis
30861 -target-exec-status
30864 Provide information on the state of the target (whether it is running or
30865 not, for instance).
30867 @subsubheading @value{GDBN} Command
30869 There's no equivalent @value{GDBN} command.
30871 @subsubheading Example
30875 @subheading The @code{-target-list-available-targets} Command
30876 @findex -target-list-available-targets
30878 @subsubheading Synopsis
30881 -target-list-available-targets
30884 List the possible targets to connect to.
30886 @subsubheading @value{GDBN} Command
30888 The corresponding @value{GDBN} command is @samp{help target}.
30890 @subsubheading Example
30894 @subheading The @code{-target-list-current-targets} Command
30895 @findex -target-list-current-targets
30897 @subsubheading Synopsis
30900 -target-list-current-targets
30903 Describe the current target.
30905 @subsubheading @value{GDBN} Command
30907 The corresponding information is printed by @samp{info file} (among
30910 @subsubheading Example
30914 @subheading The @code{-target-list-parameters} Command
30915 @findex -target-list-parameters
30917 @subsubheading Synopsis
30920 -target-list-parameters
30926 @subsubheading @value{GDBN} Command
30930 @subsubheading Example
30934 @subheading The @code{-target-select} Command
30935 @findex -target-select
30937 @subsubheading Synopsis
30940 -target-select @var{type} @var{parameters @dots{}}
30943 Connect @value{GDBN} to the remote target. This command takes two args:
30947 The type of target, for instance @samp{remote}, etc.
30948 @item @var{parameters}
30949 Device names, host names and the like. @xref{Target Commands, ,
30950 Commands for Managing Targets}, for more details.
30953 The output is a connection notification, followed by the address at
30954 which the target program is, in the following form:
30957 ^connected,addr="@var{address}",func="@var{function name}",
30958 args=[@var{arg list}]
30961 @subsubheading @value{GDBN} Command
30963 The corresponding @value{GDBN} command is @samp{target}.
30965 @subsubheading Example
30969 -target-select remote /dev/ttya
30970 ^connected,addr="0xfe00a300",func="??",args=[]
30974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30975 @node GDB/MI File Transfer Commands
30976 @section @sc{gdb/mi} File Transfer Commands
30979 @subheading The @code{-target-file-put} Command
30980 @findex -target-file-put
30982 @subsubheading Synopsis
30985 -target-file-put @var{hostfile} @var{targetfile}
30988 Copy file @var{hostfile} from the host system (the machine running
30989 @value{GDBN}) to @var{targetfile} on the target system.
30991 @subsubheading @value{GDBN} Command
30993 The corresponding @value{GDBN} command is @samp{remote put}.
30995 @subsubheading Example
30999 -target-file-put localfile remotefile
31005 @subheading The @code{-target-file-get} Command
31006 @findex -target-file-get
31008 @subsubheading Synopsis
31011 -target-file-get @var{targetfile} @var{hostfile}
31014 Copy file @var{targetfile} from the target system to @var{hostfile}
31015 on the host system.
31017 @subsubheading @value{GDBN} Command
31019 The corresponding @value{GDBN} command is @samp{remote get}.
31021 @subsubheading Example
31025 -target-file-get remotefile localfile
31031 @subheading The @code{-target-file-delete} Command
31032 @findex -target-file-delete
31034 @subsubheading Synopsis
31037 -target-file-delete @var{targetfile}
31040 Delete @var{targetfile} from the target system.
31042 @subsubheading @value{GDBN} Command
31044 The corresponding @value{GDBN} command is @samp{remote delete}.
31046 @subsubheading Example
31050 -target-file-delete remotefile
31056 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31057 @node GDB/MI Miscellaneous Commands
31058 @section Miscellaneous @sc{gdb/mi} Commands
31060 @c @subheading -gdb-complete
31062 @subheading The @code{-gdb-exit} Command
31065 @subsubheading Synopsis
31071 Exit @value{GDBN} immediately.
31073 @subsubheading @value{GDBN} Command
31075 Approximately corresponds to @samp{quit}.
31077 @subsubheading Example
31087 @subheading The @code{-exec-abort} Command
31088 @findex -exec-abort
31090 @subsubheading Synopsis
31096 Kill the inferior running program.
31098 @subsubheading @value{GDBN} Command
31100 The corresponding @value{GDBN} command is @samp{kill}.
31102 @subsubheading Example
31107 @subheading The @code{-gdb-set} Command
31110 @subsubheading Synopsis
31116 Set an internal @value{GDBN} variable.
31117 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31119 @subsubheading @value{GDBN} Command
31121 The corresponding @value{GDBN} command is @samp{set}.
31123 @subsubheading Example
31133 @subheading The @code{-gdb-show} Command
31136 @subsubheading Synopsis
31142 Show the current value of a @value{GDBN} variable.
31144 @subsubheading @value{GDBN} Command
31146 The corresponding @value{GDBN} command is @samp{show}.
31148 @subsubheading Example
31157 @c @subheading -gdb-source
31160 @subheading The @code{-gdb-version} Command
31161 @findex -gdb-version
31163 @subsubheading Synopsis
31169 Show version information for @value{GDBN}. Used mostly in testing.
31171 @subsubheading @value{GDBN} Command
31173 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31174 default shows this information when you start an interactive session.
31176 @subsubheading Example
31178 @c This example modifies the actual output from GDB to avoid overfull
31184 ~Copyright 2000 Free Software Foundation, Inc.
31185 ~GDB is free software, covered by the GNU General Public License, and
31186 ~you are welcome to change it and/or distribute copies of it under
31187 ~ certain conditions.
31188 ~Type "show copying" to see the conditions.
31189 ~There is absolutely no warranty for GDB. Type "show warranty" for
31191 ~This GDB was configured as
31192 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31197 @subheading The @code{-list-features} Command
31198 @findex -list-features
31200 Returns a list of particular features of the MI protocol that
31201 this version of gdb implements. A feature can be a command,
31202 or a new field in an output of some command, or even an
31203 important bugfix. While a frontend can sometimes detect presence
31204 of a feature at runtime, it is easier to perform detection at debugger
31207 The command returns a list of strings, with each string naming an
31208 available feature. Each returned string is just a name, it does not
31209 have any internal structure. The list of possible feature names
31215 (gdb) -list-features
31216 ^done,result=["feature1","feature2"]
31219 The current list of features is:
31222 @item frozen-varobjs
31223 Indicates support for the @code{-var-set-frozen} command, as well
31224 as possible presense of the @code{frozen} field in the output
31225 of @code{-varobj-create}.
31226 @item pending-breakpoints
31227 Indicates support for the @option{-f} option to the @code{-break-insert}
31230 Indicates Python scripting support, Python-based
31231 pretty-printing commands, and possible presence of the
31232 @samp{display_hint} field in the output of @code{-var-list-children}
31234 Indicates support for the @code{-thread-info} command.
31235 @item data-read-memory-bytes
31236 Indicates support for the @code{-data-read-memory-bytes} and the
31237 @code{-data-write-memory-bytes} commands.
31238 @item breakpoint-notifications
31239 Indicates that changes to breakpoints and breakpoints created via the
31240 CLI will be announced via async records.
31241 @item ada-task-info
31242 Indicates support for the @code{-ada-task-info} command.
31245 @subheading The @code{-list-target-features} Command
31246 @findex -list-target-features
31248 Returns a list of particular features that are supported by the
31249 target. Those features affect the permitted MI commands, but
31250 unlike the features reported by the @code{-list-features} command, the
31251 features depend on which target GDB is using at the moment. Whenever
31252 a target can change, due to commands such as @code{-target-select},
31253 @code{-target-attach} or @code{-exec-run}, the list of target features
31254 may change, and the frontend should obtain it again.
31258 (gdb) -list-features
31259 ^done,result=["async"]
31262 The current list of features is:
31266 Indicates that the target is capable of asynchronous command
31267 execution, which means that @value{GDBN} will accept further commands
31268 while the target is running.
31271 Indicates that the target is capable of reverse execution.
31272 @xref{Reverse Execution}, for more information.
31276 @subheading The @code{-list-thread-groups} Command
31277 @findex -list-thread-groups
31279 @subheading Synopsis
31282 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31285 Lists thread groups (@pxref{Thread groups}). When a single thread
31286 group is passed as the argument, lists the children of that group.
31287 When several thread group are passed, lists information about those
31288 thread groups. Without any parameters, lists information about all
31289 top-level thread groups.
31291 Normally, thread groups that are being debugged are reported.
31292 With the @samp{--available} option, @value{GDBN} reports thread groups
31293 available on the target.
31295 The output of this command may have either a @samp{threads} result or
31296 a @samp{groups} result. The @samp{thread} result has a list of tuples
31297 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31298 Information}). The @samp{groups} result has a list of tuples as value,
31299 each tuple describing a thread group. If top-level groups are
31300 requested (that is, no parameter is passed), or when several groups
31301 are passed, the output always has a @samp{groups} result. The format
31302 of the @samp{group} result is described below.
31304 To reduce the number of roundtrips it's possible to list thread groups
31305 together with their children, by passing the @samp{--recurse} option
31306 and the recursion depth. Presently, only recursion depth of 1 is
31307 permitted. If this option is present, then every reported thread group
31308 will also include its children, either as @samp{group} or
31309 @samp{threads} field.
31311 In general, any combination of option and parameters is permitted, with
31312 the following caveats:
31316 When a single thread group is passed, the output will typically
31317 be the @samp{threads} result. Because threads may not contain
31318 anything, the @samp{recurse} option will be ignored.
31321 When the @samp{--available} option is passed, limited information may
31322 be available. In particular, the list of threads of a process might
31323 be inaccessible. Further, specifying specific thread groups might
31324 not give any performance advantage over listing all thread groups.
31325 The frontend should assume that @samp{-list-thread-groups --available}
31326 is always an expensive operation and cache the results.
31330 The @samp{groups} result is a list of tuples, where each tuple may
31331 have the following fields:
31335 Identifier of the thread group. This field is always present.
31336 The identifier is an opaque string; frontends should not try to
31337 convert it to an integer, even though it might look like one.
31340 The type of the thread group. At present, only @samp{process} is a
31344 The target-specific process identifier. This field is only present
31345 for thread groups of type @samp{process} and only if the process exists.
31348 The number of children this thread group has. This field may be
31349 absent for an available thread group.
31352 This field has a list of tuples as value, each tuple describing a
31353 thread. It may be present if the @samp{--recurse} option is
31354 specified, and it's actually possible to obtain the threads.
31357 This field is a list of integers, each identifying a core that one
31358 thread of the group is running on. This field may be absent if
31359 such information is not available.
31362 The name of the executable file that corresponds to this thread group.
31363 The field is only present for thread groups of type @samp{process},
31364 and only if there is a corresponding executable file.
31368 @subheading Example
31372 -list-thread-groups
31373 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31374 -list-thread-groups 17
31375 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31376 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31377 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31378 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31379 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31380 -list-thread-groups --available
31381 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31382 -list-thread-groups --available --recurse 1
31383 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31384 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31385 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31386 -list-thread-groups --available --recurse 1 17 18
31387 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31388 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31389 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31393 @subheading The @code{-add-inferior} Command
31394 @findex -add-inferior
31396 @subheading Synopsis
31402 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31403 inferior is not associated with any executable. Such association may
31404 be established with the @samp{-file-exec-and-symbols} command
31405 (@pxref{GDB/MI File Commands}). The command response has a single
31406 field, @samp{thread-group}, whose value is the identifier of the
31407 thread group corresponding to the new inferior.
31409 @subheading Example
31414 ^done,thread-group="i3"
31417 @subheading The @code{-interpreter-exec} Command
31418 @findex -interpreter-exec
31420 @subheading Synopsis
31423 -interpreter-exec @var{interpreter} @var{command}
31425 @anchor{-interpreter-exec}
31427 Execute the specified @var{command} in the given @var{interpreter}.
31429 @subheading @value{GDBN} Command
31431 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31433 @subheading Example
31437 -interpreter-exec console "break main"
31438 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31439 &"During symbol reading, bad structure-type format.\n"
31440 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31445 @subheading The @code{-inferior-tty-set} Command
31446 @findex -inferior-tty-set
31448 @subheading Synopsis
31451 -inferior-tty-set /dev/pts/1
31454 Set terminal for future runs of the program being debugged.
31456 @subheading @value{GDBN} Command
31458 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31460 @subheading Example
31464 -inferior-tty-set /dev/pts/1
31469 @subheading The @code{-inferior-tty-show} Command
31470 @findex -inferior-tty-show
31472 @subheading Synopsis
31478 Show terminal for future runs of program being debugged.
31480 @subheading @value{GDBN} Command
31482 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31484 @subheading Example
31488 -inferior-tty-set /dev/pts/1
31492 ^done,inferior_tty_terminal="/dev/pts/1"
31496 @subheading The @code{-enable-timings} Command
31497 @findex -enable-timings
31499 @subheading Synopsis
31502 -enable-timings [yes | no]
31505 Toggle the printing of the wallclock, user and system times for an MI
31506 command as a field in its output. This command is to help frontend
31507 developers optimize the performance of their code. No argument is
31508 equivalent to @samp{yes}.
31510 @subheading @value{GDBN} Command
31514 @subheading Example
31522 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31523 addr="0x080484ed",func="main",file="myprog.c",
31524 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31525 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31533 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31534 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31535 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31536 fullname="/home/nickrob/myprog.c",line="73"@}
31541 @chapter @value{GDBN} Annotations
31543 This chapter describes annotations in @value{GDBN}. Annotations were
31544 designed to interface @value{GDBN} to graphical user interfaces or other
31545 similar programs which want to interact with @value{GDBN} at a
31546 relatively high level.
31548 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31552 This is Edition @value{EDITION}, @value{DATE}.
31556 * Annotations Overview:: What annotations are; the general syntax.
31557 * Server Prefix:: Issuing a command without affecting user state.
31558 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31559 * Errors:: Annotations for error messages.
31560 * Invalidation:: Some annotations describe things now invalid.
31561 * Annotations for Running::
31562 Whether the program is running, how it stopped, etc.
31563 * Source Annotations:: Annotations describing source code.
31566 @node Annotations Overview
31567 @section What is an Annotation?
31568 @cindex annotations
31570 Annotations start with a newline character, two @samp{control-z}
31571 characters, and the name of the annotation. If there is no additional
31572 information associated with this annotation, the name of the annotation
31573 is followed immediately by a newline. If there is additional
31574 information, the name of the annotation is followed by a space, the
31575 additional information, and a newline. The additional information
31576 cannot contain newline characters.
31578 Any output not beginning with a newline and two @samp{control-z}
31579 characters denotes literal output from @value{GDBN}. Currently there is
31580 no need for @value{GDBN} to output a newline followed by two
31581 @samp{control-z} characters, but if there was such a need, the
31582 annotations could be extended with an @samp{escape} annotation which
31583 means those three characters as output.
31585 The annotation @var{level}, which is specified using the
31586 @option{--annotate} command line option (@pxref{Mode Options}), controls
31587 how much information @value{GDBN} prints together with its prompt,
31588 values of expressions, source lines, and other types of output. Level 0
31589 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31590 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31591 for programs that control @value{GDBN}, and level 2 annotations have
31592 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31593 Interface, annotate, GDB's Obsolete Annotations}).
31596 @kindex set annotate
31597 @item set annotate @var{level}
31598 The @value{GDBN} command @code{set annotate} sets the level of
31599 annotations to the specified @var{level}.
31601 @item show annotate
31602 @kindex show annotate
31603 Show the current annotation level.
31606 This chapter describes level 3 annotations.
31608 A simple example of starting up @value{GDBN} with annotations is:
31611 $ @kbd{gdb --annotate=3}
31613 Copyright 2003 Free Software Foundation, Inc.
31614 GDB is free software, covered by the GNU General Public License,
31615 and you are welcome to change it and/or distribute copies of it
31616 under certain conditions.
31617 Type "show copying" to see the conditions.
31618 There is absolutely no warranty for GDB. Type "show warranty"
31620 This GDB was configured as "i386-pc-linux-gnu"
31631 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31632 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31633 denotes a @samp{control-z} character) are annotations; the rest is
31634 output from @value{GDBN}.
31636 @node Server Prefix
31637 @section The Server Prefix
31638 @cindex server prefix
31640 If you prefix a command with @samp{server } then it will not affect
31641 the command history, nor will it affect @value{GDBN}'s notion of which
31642 command to repeat if @key{RET} is pressed on a line by itself. This
31643 means that commands can be run behind a user's back by a front-end in
31644 a transparent manner.
31646 The @code{server } prefix does not affect the recording of values into
31647 the value history; to print a value without recording it into the
31648 value history, use the @code{output} command instead of the
31649 @code{print} command.
31651 Using this prefix also disables confirmation requests
31652 (@pxref{confirmation requests}).
31655 @section Annotation for @value{GDBN} Input
31657 @cindex annotations for prompts
31658 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31659 to know when to send output, when the output from a given command is
31662 Different kinds of input each have a different @dfn{input type}. Each
31663 input type has three annotations: a @code{pre-} annotation, which
31664 denotes the beginning of any prompt which is being output, a plain
31665 annotation, which denotes the end of the prompt, and then a @code{post-}
31666 annotation which denotes the end of any echo which may (or may not) be
31667 associated with the input. For example, the @code{prompt} input type
31668 features the following annotations:
31676 The input types are
31679 @findex pre-prompt annotation
31680 @findex prompt annotation
31681 @findex post-prompt annotation
31683 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31685 @findex pre-commands annotation
31686 @findex commands annotation
31687 @findex post-commands annotation
31689 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31690 command. The annotations are repeated for each command which is input.
31692 @findex pre-overload-choice annotation
31693 @findex overload-choice annotation
31694 @findex post-overload-choice annotation
31695 @item overload-choice
31696 When @value{GDBN} wants the user to select between various overloaded functions.
31698 @findex pre-query annotation
31699 @findex query annotation
31700 @findex post-query annotation
31702 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31704 @findex pre-prompt-for-continue annotation
31705 @findex prompt-for-continue annotation
31706 @findex post-prompt-for-continue annotation
31707 @item prompt-for-continue
31708 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31709 expect this to work well; instead use @code{set height 0} to disable
31710 prompting. This is because the counting of lines is buggy in the
31711 presence of annotations.
31716 @cindex annotations for errors, warnings and interrupts
31718 @findex quit annotation
31723 This annotation occurs right before @value{GDBN} responds to an interrupt.
31725 @findex error annotation
31730 This annotation occurs right before @value{GDBN} responds to an error.
31732 Quit and error annotations indicate that any annotations which @value{GDBN} was
31733 in the middle of may end abruptly. For example, if a
31734 @code{value-history-begin} annotation is followed by a @code{error}, one
31735 cannot expect to receive the matching @code{value-history-end}. One
31736 cannot expect not to receive it either, however; an error annotation
31737 does not necessarily mean that @value{GDBN} is immediately returning all the way
31740 @findex error-begin annotation
31741 A quit or error annotation may be preceded by
31747 Any output between that and the quit or error annotation is the error
31750 Warning messages are not yet annotated.
31751 @c If we want to change that, need to fix warning(), type_error(),
31752 @c range_error(), and possibly other places.
31755 @section Invalidation Notices
31757 @cindex annotations for invalidation messages
31758 The following annotations say that certain pieces of state may have
31762 @findex frames-invalid annotation
31763 @item ^Z^Zframes-invalid
31765 The frames (for example, output from the @code{backtrace} command) may
31768 @findex breakpoints-invalid annotation
31769 @item ^Z^Zbreakpoints-invalid
31771 The breakpoints may have changed. For example, the user just added or
31772 deleted a breakpoint.
31775 @node Annotations for Running
31776 @section Running the Program
31777 @cindex annotations for running programs
31779 @findex starting annotation
31780 @findex stopping annotation
31781 When the program starts executing due to a @value{GDBN} command such as
31782 @code{step} or @code{continue},
31788 is output. When the program stops,
31794 is output. Before the @code{stopped} annotation, a variety of
31795 annotations describe how the program stopped.
31798 @findex exited annotation
31799 @item ^Z^Zexited @var{exit-status}
31800 The program exited, and @var{exit-status} is the exit status (zero for
31801 successful exit, otherwise nonzero).
31803 @findex signalled annotation
31804 @findex signal-name annotation
31805 @findex signal-name-end annotation
31806 @findex signal-string annotation
31807 @findex signal-string-end annotation
31808 @item ^Z^Zsignalled
31809 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31810 annotation continues:
31816 ^Z^Zsignal-name-end
31820 ^Z^Zsignal-string-end
31825 where @var{name} is the name of the signal, such as @code{SIGILL} or
31826 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31827 as @code{Illegal Instruction} or @code{Segmentation fault}.
31828 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31829 user's benefit and have no particular format.
31831 @findex signal annotation
31833 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31834 just saying that the program received the signal, not that it was
31835 terminated with it.
31837 @findex breakpoint annotation
31838 @item ^Z^Zbreakpoint @var{number}
31839 The program hit breakpoint number @var{number}.
31841 @findex watchpoint annotation
31842 @item ^Z^Zwatchpoint @var{number}
31843 The program hit watchpoint number @var{number}.
31846 @node Source Annotations
31847 @section Displaying Source
31848 @cindex annotations for source display
31850 @findex source annotation
31851 The following annotation is used instead of displaying source code:
31854 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31857 where @var{filename} is an absolute file name indicating which source
31858 file, @var{line} is the line number within that file (where 1 is the
31859 first line in the file), @var{character} is the character position
31860 within the file (where 0 is the first character in the file) (for most
31861 debug formats this will necessarily point to the beginning of a line),
31862 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31863 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31864 @var{addr} is the address in the target program associated with the
31865 source which is being displayed. @var{addr} is in the form @samp{0x}
31866 followed by one or more lowercase hex digits (note that this does not
31867 depend on the language).
31869 @node JIT Interface
31870 @chapter JIT Compilation Interface
31871 @cindex just-in-time compilation
31872 @cindex JIT compilation interface
31874 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31875 interface. A JIT compiler is a program or library that generates native
31876 executable code at runtime and executes it, usually in order to achieve good
31877 performance while maintaining platform independence.
31879 Programs that use JIT compilation are normally difficult to debug because
31880 portions of their code are generated at runtime, instead of being loaded from
31881 object files, which is where @value{GDBN} normally finds the program's symbols
31882 and debug information. In order to debug programs that use JIT compilation,
31883 @value{GDBN} has an interface that allows the program to register in-memory
31884 symbol files with @value{GDBN} at runtime.
31886 If you are using @value{GDBN} to debug a program that uses this interface, then
31887 it should work transparently so long as you have not stripped the binary. If
31888 you are developing a JIT compiler, then the interface is documented in the rest
31889 of this chapter. At this time, the only known client of this interface is the
31892 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31893 JIT compiler communicates with @value{GDBN} by writing data into a global
31894 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31895 attaches, it reads a linked list of symbol files from the global variable to
31896 find existing code, and puts a breakpoint in the function so that it can find
31897 out about additional code.
31900 * Declarations:: Relevant C struct declarations
31901 * Registering Code:: Steps to register code
31902 * Unregistering Code:: Steps to unregister code
31903 * Custom Debug Info:: Emit debug information in a custom format
31907 @section JIT Declarations
31909 These are the relevant struct declarations that a C program should include to
31910 implement the interface:
31920 struct jit_code_entry
31922 struct jit_code_entry *next_entry;
31923 struct jit_code_entry *prev_entry;
31924 const char *symfile_addr;
31925 uint64_t symfile_size;
31928 struct jit_descriptor
31931 /* This type should be jit_actions_t, but we use uint32_t
31932 to be explicit about the bitwidth. */
31933 uint32_t action_flag;
31934 struct jit_code_entry *relevant_entry;
31935 struct jit_code_entry *first_entry;
31938 /* GDB puts a breakpoint in this function. */
31939 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31941 /* Make sure to specify the version statically, because the
31942 debugger may check the version before we can set it. */
31943 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31946 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31947 modifications to this global data properly, which can easily be done by putting
31948 a global mutex around modifications to these structures.
31950 @node Registering Code
31951 @section Registering Code
31953 To register code with @value{GDBN}, the JIT should follow this protocol:
31957 Generate an object file in memory with symbols and other desired debug
31958 information. The file must include the virtual addresses of the sections.
31961 Create a code entry for the file, which gives the start and size of the symbol
31965 Add it to the linked list in the JIT descriptor.
31968 Point the relevant_entry field of the descriptor at the entry.
31971 Set @code{action_flag} to @code{JIT_REGISTER} and call
31972 @code{__jit_debug_register_code}.
31975 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31976 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31977 new code. However, the linked list must still be maintained in order to allow
31978 @value{GDBN} to attach to a running process and still find the symbol files.
31980 @node Unregistering Code
31981 @section Unregistering Code
31983 If code is freed, then the JIT should use the following protocol:
31987 Remove the code entry corresponding to the code from the linked list.
31990 Point the @code{relevant_entry} field of the descriptor at the code entry.
31993 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31994 @code{__jit_debug_register_code}.
31997 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31998 and the JIT will leak the memory used for the associated symbol files.
32000 @node Custom Debug Info
32001 @section Custom Debug Info
32002 @cindex custom JIT debug info
32003 @cindex JIT debug info reader
32005 Generating debug information in platform-native file formats (like ELF
32006 or COFF) may be an overkill for JIT compilers; especially if all the
32007 debug info is used for is displaying a meaningful backtrace. The
32008 issue can be resolved by having the JIT writers decide on a debug info
32009 format and also provide a reader that parses the debug info generated
32010 by the JIT compiler. This section gives a brief overview on writing
32011 such a parser. More specific details can be found in the source file
32012 @file{gdb/jit-reader.in}, which is also installed as a header at
32013 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32015 The reader is implemented as a shared object (so this functionality is
32016 not available on platforms which don't allow loading shared objects at
32017 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32018 @code{jit-reader-unload} are provided, to be used to load and unload
32019 the readers from a preconfigured directory. Once loaded, the shared
32020 object is used the parse the debug information emitted by the JIT
32024 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32025 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32028 @node Using JIT Debug Info Readers
32029 @subsection Using JIT Debug Info Readers
32030 @kindex jit-reader-load
32031 @kindex jit-reader-unload
32033 Readers can be loaded and unloaded using the @code{jit-reader-load}
32034 and @code{jit-reader-unload} commands.
32037 @item jit-reader-load @var{reader-name}
32038 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32039 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32040 @var{libdir} is the system library directory, usually
32041 @file{/usr/local/lib}. Only one reader can be active at a time;
32042 trying to load a second reader when one is already loaded will result
32043 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32044 first unloading the current one using @code{jit-reader-load} and then
32045 invoking @code{jit-reader-load}.
32047 @item jit-reader-unload
32048 Unload the currently loaded JIT reader.
32052 @node Writing JIT Debug Info Readers
32053 @subsection Writing JIT Debug Info Readers
32054 @cindex writing JIT debug info readers
32056 As mentioned, a reader is essentially a shared object conforming to a
32057 certain ABI. This ABI is described in @file{jit-reader.h}.
32059 @file{jit-reader.h} defines the structures, macros and functions
32060 required to write a reader. It is installed (along with
32061 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32062 the system include directory.
32064 Readers need to be released under a GPL compatible license. A reader
32065 can be declared as released under such a license by placing the macro
32066 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32068 The entry point for readers is the symbol @code{gdb_init_reader},
32069 which is expected to be a function with the prototype
32071 @findex gdb_init_reader
32073 extern struct gdb_reader_funcs *gdb_init_reader (void);
32076 @cindex @code{struct gdb_reader_funcs}
32078 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32079 functions. These functions are executed to read the debug info
32080 generated by the JIT compiler (@code{read}), to unwind stack frames
32081 (@code{unwind}) and to create canonical frame IDs
32082 (@code{get_Frame_id}). It also has a callback that is called when the
32083 reader is being unloaded (@code{destroy}). The struct looks like this
32086 struct gdb_reader_funcs
32088 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32089 int reader_version;
32091 /* For use by the reader. */
32094 gdb_read_debug_info *read;
32095 gdb_unwind_frame *unwind;
32096 gdb_get_frame_id *get_frame_id;
32097 gdb_destroy_reader *destroy;
32101 @cindex @code{struct gdb_symbol_callbacks}
32102 @cindex @code{struct gdb_unwind_callbacks}
32104 The callbacks are provided with another set of callbacks by
32105 @value{GDBN} to do their job. For @code{read}, these callbacks are
32106 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32107 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32108 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32109 files and new symbol tables inside those object files. @code{struct
32110 gdb_unwind_callbacks} has callbacks to read registers off the current
32111 frame and to write out the values of the registers in the previous
32112 frame. Both have a callback (@code{target_read}) to read bytes off the
32113 target's address space.
32116 @chapter Reporting Bugs in @value{GDBN}
32117 @cindex bugs in @value{GDBN}
32118 @cindex reporting bugs in @value{GDBN}
32120 Your bug reports play an essential role in making @value{GDBN} reliable.
32122 Reporting a bug may help you by bringing a solution to your problem, or it
32123 may not. But in any case the principal function of a bug report is to help
32124 the entire community by making the next version of @value{GDBN} work better. Bug
32125 reports are your contribution to the maintenance of @value{GDBN}.
32127 In order for a bug report to serve its purpose, you must include the
32128 information that enables us to fix the bug.
32131 * Bug Criteria:: Have you found a bug?
32132 * Bug Reporting:: How to report bugs
32136 @section Have You Found a Bug?
32137 @cindex bug criteria
32139 If you are not sure whether you have found a bug, here are some guidelines:
32142 @cindex fatal signal
32143 @cindex debugger crash
32144 @cindex crash of debugger
32146 If the debugger gets a fatal signal, for any input whatever, that is a
32147 @value{GDBN} bug. Reliable debuggers never crash.
32149 @cindex error on valid input
32151 If @value{GDBN} produces an error message for valid input, that is a
32152 bug. (Note that if you're cross debugging, the problem may also be
32153 somewhere in the connection to the target.)
32155 @cindex invalid input
32157 If @value{GDBN} does not produce an error message for invalid input,
32158 that is a bug. However, you should note that your idea of
32159 ``invalid input'' might be our idea of ``an extension'' or ``support
32160 for traditional practice''.
32163 If you are an experienced user of debugging tools, your suggestions
32164 for improvement of @value{GDBN} are welcome in any case.
32167 @node Bug Reporting
32168 @section How to Report Bugs
32169 @cindex bug reports
32170 @cindex @value{GDBN} bugs, reporting
32172 A number of companies and individuals offer support for @sc{gnu} products.
32173 If you obtained @value{GDBN} from a support organization, we recommend you
32174 contact that organization first.
32176 You can find contact information for many support companies and
32177 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32179 @c should add a web page ref...
32182 @ifset BUGURL_DEFAULT
32183 In any event, we also recommend that you submit bug reports for
32184 @value{GDBN}. The preferred method is to submit them directly using
32185 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32186 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32189 @strong{Do not send bug reports to @samp{info-gdb}, or to
32190 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32191 not want to receive bug reports. Those that do have arranged to receive
32194 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32195 serves as a repeater. The mailing list and the newsgroup carry exactly
32196 the same messages. Often people think of posting bug reports to the
32197 newsgroup instead of mailing them. This appears to work, but it has one
32198 problem which can be crucial: a newsgroup posting often lacks a mail
32199 path back to the sender. Thus, if we need to ask for more information,
32200 we may be unable to reach you. For this reason, it is better to send
32201 bug reports to the mailing list.
32203 @ifclear BUGURL_DEFAULT
32204 In any event, we also recommend that you submit bug reports for
32205 @value{GDBN} to @value{BUGURL}.
32209 The fundamental principle of reporting bugs usefully is this:
32210 @strong{report all the facts}. If you are not sure whether to state a
32211 fact or leave it out, state it!
32213 Often people omit facts because they think they know what causes the
32214 problem and assume that some details do not matter. Thus, you might
32215 assume that the name of the variable you use in an example does not matter.
32216 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32217 stray memory reference which happens to fetch from the location where that
32218 name is stored in memory; perhaps, if the name were different, the contents
32219 of that location would fool the debugger into doing the right thing despite
32220 the bug. Play it safe and give a specific, complete example. That is the
32221 easiest thing for you to do, and the most helpful.
32223 Keep in mind that the purpose of a bug report is to enable us to fix the
32224 bug. It may be that the bug has been reported previously, but neither
32225 you nor we can know that unless your bug report is complete and
32228 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32229 bell?'' Those bug reports are useless, and we urge everyone to
32230 @emph{refuse to respond to them} except to chide the sender to report
32233 To enable us to fix the bug, you should include all these things:
32237 The version of @value{GDBN}. @value{GDBN} announces it if you start
32238 with no arguments; you can also print it at any time using @code{show
32241 Without this, we will not know whether there is any point in looking for
32242 the bug in the current version of @value{GDBN}.
32245 The type of machine you are using, and the operating system name and
32249 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32250 ``@value{GCC}--2.8.1''.
32253 What compiler (and its version) was used to compile the program you are
32254 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32255 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32256 to get this information; for other compilers, see the documentation for
32260 The command arguments you gave the compiler to compile your example and
32261 observe the bug. For example, did you use @samp{-O}? To guarantee
32262 you will not omit something important, list them all. A copy of the
32263 Makefile (or the output from make) is sufficient.
32265 If we were to try to guess the arguments, we would probably guess wrong
32266 and then we might not encounter the bug.
32269 A complete input script, and all necessary source files, that will
32273 A description of what behavior you observe that you believe is
32274 incorrect. For example, ``It gets a fatal signal.''
32276 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32277 will certainly notice it. But if the bug is incorrect output, we might
32278 not notice unless it is glaringly wrong. You might as well not give us
32279 a chance to make a mistake.
32281 Even if the problem you experience is a fatal signal, you should still
32282 say so explicitly. Suppose something strange is going on, such as, your
32283 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32284 the C library on your system. (This has happened!) Your copy might
32285 crash and ours would not. If you told us to expect a crash, then when
32286 ours fails to crash, we would know that the bug was not happening for
32287 us. If you had not told us to expect a crash, then we would not be able
32288 to draw any conclusion from our observations.
32291 @cindex recording a session script
32292 To collect all this information, you can use a session recording program
32293 such as @command{script}, which is available on many Unix systems.
32294 Just run your @value{GDBN} session inside @command{script} and then
32295 include the @file{typescript} file with your bug report.
32297 Another way to record a @value{GDBN} session is to run @value{GDBN}
32298 inside Emacs and then save the entire buffer to a file.
32301 If you wish to suggest changes to the @value{GDBN} source, send us context
32302 diffs. If you even discuss something in the @value{GDBN} source, refer to
32303 it by context, not by line number.
32305 The line numbers in our development sources will not match those in your
32306 sources. Your line numbers would convey no useful information to us.
32310 Here are some things that are not necessary:
32314 A description of the envelope of the bug.
32316 Often people who encounter a bug spend a lot of time investigating
32317 which changes to the input file will make the bug go away and which
32318 changes will not affect it.
32320 This is often time consuming and not very useful, because the way we
32321 will find the bug is by running a single example under the debugger
32322 with breakpoints, not by pure deduction from a series of examples.
32323 We recommend that you save your time for something else.
32325 Of course, if you can find a simpler example to report @emph{instead}
32326 of the original one, that is a convenience for us. Errors in the
32327 output will be easier to spot, running under the debugger will take
32328 less time, and so on.
32330 However, simplification is not vital; if you do not want to do this,
32331 report the bug anyway and send us the entire test case you used.
32334 A patch for the bug.
32336 A patch for the bug does help us if it is a good one. But do not omit
32337 the necessary information, such as the test case, on the assumption that
32338 a patch is all we need. We might see problems with your patch and decide
32339 to fix the problem another way, or we might not understand it at all.
32341 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32342 construct an example that will make the program follow a certain path
32343 through the code. If you do not send us the example, we will not be able
32344 to construct one, so we will not be able to verify that the bug is fixed.
32346 And if we cannot understand what bug you are trying to fix, or why your
32347 patch should be an improvement, we will not install it. A test case will
32348 help us to understand.
32351 A guess about what the bug is or what it depends on.
32353 Such guesses are usually wrong. Even we cannot guess right about such
32354 things without first using the debugger to find the facts.
32357 @c The readline documentation is distributed with the readline code
32358 @c and consists of the two following files:
32361 @c Use -I with makeinfo to point to the appropriate directory,
32362 @c environment var TEXINPUTS with TeX.
32363 @ifclear SYSTEM_READLINE
32364 @include rluser.texi
32365 @include hsuser.texi
32369 @appendix In Memoriam
32371 The @value{GDBN} project mourns the loss of the following long-time
32376 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32377 to Free Software in general. Outside of @value{GDBN}, he was known in
32378 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32380 @item Michael Snyder
32381 Michael was one of the Global Maintainers of the @value{GDBN} project,
32382 with contributions recorded as early as 1996, until 2011. In addition
32383 to his day to day participation, he was a large driving force behind
32384 adding Reverse Debugging to @value{GDBN}.
32387 Beyond their technical contributions to the project, they were also
32388 enjoyable members of the Free Software Community. We will miss them.
32390 @node Formatting Documentation
32391 @appendix Formatting Documentation
32393 @cindex @value{GDBN} reference card
32394 @cindex reference card
32395 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32396 for printing with PostScript or Ghostscript, in the @file{gdb}
32397 subdirectory of the main source directory@footnote{In
32398 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32399 release.}. If you can use PostScript or Ghostscript with your printer,
32400 you can print the reference card immediately with @file{refcard.ps}.
32402 The release also includes the source for the reference card. You
32403 can format it, using @TeX{}, by typing:
32409 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32410 mode on US ``letter'' size paper;
32411 that is, on a sheet 11 inches wide by 8.5 inches
32412 high. You will need to specify this form of printing as an option to
32413 your @sc{dvi} output program.
32415 @cindex documentation
32417 All the documentation for @value{GDBN} comes as part of the machine-readable
32418 distribution. The documentation is written in Texinfo format, which is
32419 a documentation system that uses a single source file to produce both
32420 on-line information and a printed manual. You can use one of the Info
32421 formatting commands to create the on-line version of the documentation
32422 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32424 @value{GDBN} includes an already formatted copy of the on-line Info
32425 version of this manual in the @file{gdb} subdirectory. The main Info
32426 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32427 subordinate files matching @samp{gdb.info*} in the same directory. If
32428 necessary, you can print out these files, or read them with any editor;
32429 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32430 Emacs or the standalone @code{info} program, available as part of the
32431 @sc{gnu} Texinfo distribution.
32433 If you want to format these Info files yourself, you need one of the
32434 Info formatting programs, such as @code{texinfo-format-buffer} or
32437 If you have @code{makeinfo} installed, and are in the top level
32438 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32439 version @value{GDBVN}), you can make the Info file by typing:
32446 If you want to typeset and print copies of this manual, you need @TeX{},
32447 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32448 Texinfo definitions file.
32450 @TeX{} is a typesetting program; it does not print files directly, but
32451 produces output files called @sc{dvi} files. To print a typeset
32452 document, you need a program to print @sc{dvi} files. If your system
32453 has @TeX{} installed, chances are it has such a program. The precise
32454 command to use depends on your system; @kbd{lpr -d} is common; another
32455 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32456 require a file name without any extension or a @samp{.dvi} extension.
32458 @TeX{} also requires a macro definitions file called
32459 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32460 written in Texinfo format. On its own, @TeX{} cannot either read or
32461 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32462 and is located in the @file{gdb-@var{version-number}/texinfo}
32465 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32466 typeset and print this manual. First switch to the @file{gdb}
32467 subdirectory of the main source directory (for example, to
32468 @file{gdb-@value{GDBVN}/gdb}) and type:
32474 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32476 @node Installing GDB
32477 @appendix Installing @value{GDBN}
32478 @cindex installation
32481 * Requirements:: Requirements for building @value{GDBN}
32482 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32483 * Separate Objdir:: Compiling @value{GDBN} in another directory
32484 * Config Names:: Specifying names for hosts and targets
32485 * Configure Options:: Summary of options for configure
32486 * System-wide configuration:: Having a system-wide init file
32490 @section Requirements for Building @value{GDBN}
32491 @cindex building @value{GDBN}, requirements for
32493 Building @value{GDBN} requires various tools and packages to be available.
32494 Other packages will be used only if they are found.
32496 @heading Tools/Packages Necessary for Building @value{GDBN}
32498 @item ISO C90 compiler
32499 @value{GDBN} is written in ISO C90. It should be buildable with any
32500 working C90 compiler, e.g.@: GCC.
32504 @heading Tools/Packages Optional for Building @value{GDBN}
32508 @value{GDBN} can use the Expat XML parsing library. This library may be
32509 included with your operating system distribution; if it is not, you
32510 can get the latest version from @url{http://expat.sourceforge.net}.
32511 The @file{configure} script will search for this library in several
32512 standard locations; if it is installed in an unusual path, you can
32513 use the @option{--with-libexpat-prefix} option to specify its location.
32519 Remote protocol memory maps (@pxref{Memory Map Format})
32521 Target descriptions (@pxref{Target Descriptions})
32523 Remote shared library lists (@xref{Library List Format},
32524 or alternatively @pxref{Library List Format for SVR4 Targets})
32526 MS-Windows shared libraries (@pxref{Shared Libraries})
32528 Traceframe info (@pxref{Traceframe Info Format})
32532 @cindex compressed debug sections
32533 @value{GDBN} will use the @samp{zlib} library, if available, to read
32534 compressed debug sections. Some linkers, such as GNU gold, are capable
32535 of producing binaries with compressed debug sections. If @value{GDBN}
32536 is compiled with @samp{zlib}, it will be able to read the debug
32537 information in such binaries.
32539 The @samp{zlib} library is likely included with your operating system
32540 distribution; if it is not, you can get the latest version from
32541 @url{http://zlib.net}.
32544 @value{GDBN}'s features related to character sets (@pxref{Character
32545 Sets}) require a functioning @code{iconv} implementation. If you are
32546 on a GNU system, then this is provided by the GNU C Library. Some
32547 other systems also provide a working @code{iconv}.
32549 If @value{GDBN} is using the @code{iconv} program which is installed
32550 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32551 This is done with @option{--with-iconv-bin} which specifies the
32552 directory that contains the @code{iconv} program.
32554 On systems without @code{iconv}, you can install GNU Libiconv. If you
32555 have previously installed Libiconv, you can use the
32556 @option{--with-libiconv-prefix} option to configure.
32558 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32559 arrange to build Libiconv if a directory named @file{libiconv} appears
32560 in the top-most source directory. If Libiconv is built this way, and
32561 if the operating system does not provide a suitable @code{iconv}
32562 implementation, then the just-built library will automatically be used
32563 by @value{GDBN}. One easy way to set this up is to download GNU
32564 Libiconv, unpack it, and then rename the directory holding the
32565 Libiconv source code to @samp{libiconv}.
32568 @node Running Configure
32569 @section Invoking the @value{GDBN} @file{configure} Script
32570 @cindex configuring @value{GDBN}
32571 @value{GDBN} comes with a @file{configure} script that automates the process
32572 of preparing @value{GDBN} for installation; you can then use @code{make} to
32573 build the @code{gdb} program.
32575 @c irrelevant in info file; it's as current as the code it lives with.
32576 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32577 look at the @file{README} file in the sources; we may have improved the
32578 installation procedures since publishing this manual.}
32581 The @value{GDBN} distribution includes all the source code you need for
32582 @value{GDBN} in a single directory, whose name is usually composed by
32583 appending the version number to @samp{gdb}.
32585 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32586 @file{gdb-@value{GDBVN}} directory. That directory contains:
32589 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32590 script for configuring @value{GDBN} and all its supporting libraries
32592 @item gdb-@value{GDBVN}/gdb
32593 the source specific to @value{GDBN} itself
32595 @item gdb-@value{GDBVN}/bfd
32596 source for the Binary File Descriptor library
32598 @item gdb-@value{GDBVN}/include
32599 @sc{gnu} include files
32601 @item gdb-@value{GDBVN}/libiberty
32602 source for the @samp{-liberty} free software library
32604 @item gdb-@value{GDBVN}/opcodes
32605 source for the library of opcode tables and disassemblers
32607 @item gdb-@value{GDBVN}/readline
32608 source for the @sc{gnu} command-line interface
32610 @item gdb-@value{GDBVN}/glob
32611 source for the @sc{gnu} filename pattern-matching subroutine
32613 @item gdb-@value{GDBVN}/mmalloc
32614 source for the @sc{gnu} memory-mapped malloc package
32617 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32618 from the @file{gdb-@var{version-number}} source directory, which in
32619 this example is the @file{gdb-@value{GDBVN}} directory.
32621 First switch to the @file{gdb-@var{version-number}} source directory
32622 if you are not already in it; then run @file{configure}. Pass the
32623 identifier for the platform on which @value{GDBN} will run as an
32629 cd gdb-@value{GDBVN}
32630 ./configure @var{host}
32635 where @var{host} is an identifier such as @samp{sun4} or
32636 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32637 (You can often leave off @var{host}; @file{configure} tries to guess the
32638 correct value by examining your system.)
32640 Running @samp{configure @var{host}} and then running @code{make} builds the
32641 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32642 libraries, then @code{gdb} itself. The configured source files, and the
32643 binaries, are left in the corresponding source directories.
32646 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32647 system does not recognize this automatically when you run a different
32648 shell, you may need to run @code{sh} on it explicitly:
32651 sh configure @var{host}
32654 If you run @file{configure} from a directory that contains source
32655 directories for multiple libraries or programs, such as the
32656 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32658 creates configuration files for every directory level underneath (unless
32659 you tell it not to, with the @samp{--norecursion} option).
32661 You should run the @file{configure} script from the top directory in the
32662 source tree, the @file{gdb-@var{version-number}} directory. If you run
32663 @file{configure} from one of the subdirectories, you will configure only
32664 that subdirectory. That is usually not what you want. In particular,
32665 if you run the first @file{configure} from the @file{gdb} subdirectory
32666 of the @file{gdb-@var{version-number}} directory, you will omit the
32667 configuration of @file{bfd}, @file{readline}, and other sibling
32668 directories of the @file{gdb} subdirectory. This leads to build errors
32669 about missing include files such as @file{bfd/bfd.h}.
32671 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32672 However, you should make sure that the shell on your path (named by
32673 the @samp{SHELL} environment variable) is publicly readable. Remember
32674 that @value{GDBN} uses the shell to start your program---some systems refuse to
32675 let @value{GDBN} debug child processes whose programs are not readable.
32677 @node Separate Objdir
32678 @section Compiling @value{GDBN} in Another Directory
32680 If you want to run @value{GDBN} versions for several host or target machines,
32681 you need a different @code{gdb} compiled for each combination of
32682 host and target. @file{configure} is designed to make this easy by
32683 allowing you to generate each configuration in a separate subdirectory,
32684 rather than in the source directory. If your @code{make} program
32685 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32686 @code{make} in each of these directories builds the @code{gdb}
32687 program specified there.
32689 To build @code{gdb} in a separate directory, run @file{configure}
32690 with the @samp{--srcdir} option to specify where to find the source.
32691 (You also need to specify a path to find @file{configure}
32692 itself from your working directory. If the path to @file{configure}
32693 would be the same as the argument to @samp{--srcdir}, you can leave out
32694 the @samp{--srcdir} option; it is assumed.)
32696 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32697 separate directory for a Sun 4 like this:
32701 cd gdb-@value{GDBVN}
32704 ../gdb-@value{GDBVN}/configure sun4
32709 When @file{configure} builds a configuration using a remote source
32710 directory, it creates a tree for the binaries with the same structure
32711 (and using the same names) as the tree under the source directory. In
32712 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32713 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32714 @file{gdb-sun4/gdb}.
32716 Make sure that your path to the @file{configure} script has just one
32717 instance of @file{gdb} in it. If your path to @file{configure} looks
32718 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32719 one subdirectory of @value{GDBN}, not the whole package. This leads to
32720 build errors about missing include files such as @file{bfd/bfd.h}.
32722 One popular reason to build several @value{GDBN} configurations in separate
32723 directories is to configure @value{GDBN} for cross-compiling (where
32724 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32725 programs that run on another machine---the @dfn{target}).
32726 You specify a cross-debugging target by
32727 giving the @samp{--target=@var{target}} option to @file{configure}.
32729 When you run @code{make} to build a program or library, you must run
32730 it in a configured directory---whatever directory you were in when you
32731 called @file{configure} (or one of its subdirectories).
32733 The @code{Makefile} that @file{configure} generates in each source
32734 directory also runs recursively. If you type @code{make} in a source
32735 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32736 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32737 will build all the required libraries, and then build GDB.
32739 When you have multiple hosts or targets configured in separate
32740 directories, you can run @code{make} on them in parallel (for example,
32741 if they are NFS-mounted on each of the hosts); they will not interfere
32745 @section Specifying Names for Hosts and Targets
32747 The specifications used for hosts and targets in the @file{configure}
32748 script are based on a three-part naming scheme, but some short predefined
32749 aliases are also supported. The full naming scheme encodes three pieces
32750 of information in the following pattern:
32753 @var{architecture}-@var{vendor}-@var{os}
32756 For example, you can use the alias @code{sun4} as a @var{host} argument,
32757 or as the value for @var{target} in a @code{--target=@var{target}}
32758 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32760 The @file{configure} script accompanying @value{GDBN} does not provide
32761 any query facility to list all supported host and target names or
32762 aliases. @file{configure} calls the Bourne shell script
32763 @code{config.sub} to map abbreviations to full names; you can read the
32764 script, if you wish, or you can use it to test your guesses on
32765 abbreviations---for example:
32768 % sh config.sub i386-linux
32770 % sh config.sub alpha-linux
32771 alpha-unknown-linux-gnu
32772 % sh config.sub hp9k700
32774 % sh config.sub sun4
32775 sparc-sun-sunos4.1.1
32776 % sh config.sub sun3
32777 m68k-sun-sunos4.1.1
32778 % sh config.sub i986v
32779 Invalid configuration `i986v': machine `i986v' not recognized
32783 @code{config.sub} is also distributed in the @value{GDBN} source
32784 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32786 @node Configure Options
32787 @section @file{configure} Options
32789 Here is a summary of the @file{configure} options and arguments that
32790 are most often useful for building @value{GDBN}. @file{configure} also has
32791 several other options not listed here. @inforef{What Configure
32792 Does,,configure.info}, for a full explanation of @file{configure}.
32795 configure @r{[}--help@r{]}
32796 @r{[}--prefix=@var{dir}@r{]}
32797 @r{[}--exec-prefix=@var{dir}@r{]}
32798 @r{[}--srcdir=@var{dirname}@r{]}
32799 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32800 @r{[}--target=@var{target}@r{]}
32805 You may introduce options with a single @samp{-} rather than
32806 @samp{--} if you prefer; but you may abbreviate option names if you use
32811 Display a quick summary of how to invoke @file{configure}.
32813 @item --prefix=@var{dir}
32814 Configure the source to install programs and files under directory
32817 @item --exec-prefix=@var{dir}
32818 Configure the source to install programs under directory
32821 @c avoid splitting the warning from the explanation:
32823 @item --srcdir=@var{dirname}
32824 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32825 @code{make} that implements the @code{VPATH} feature.}@*
32826 Use this option to make configurations in directories separate from the
32827 @value{GDBN} source directories. Among other things, you can use this to
32828 build (or maintain) several configurations simultaneously, in separate
32829 directories. @file{configure} writes configuration-specific files in
32830 the current directory, but arranges for them to use the source in the
32831 directory @var{dirname}. @file{configure} creates directories under
32832 the working directory in parallel to the source directories below
32835 @item --norecursion
32836 Configure only the directory level where @file{configure} is executed; do not
32837 propagate configuration to subdirectories.
32839 @item --target=@var{target}
32840 Configure @value{GDBN} for cross-debugging programs running on the specified
32841 @var{target}. Without this option, @value{GDBN} is configured to debug
32842 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32844 There is no convenient way to generate a list of all available targets.
32846 @item @var{host} @dots{}
32847 Configure @value{GDBN} to run on the specified @var{host}.
32849 There is no convenient way to generate a list of all available hosts.
32852 There are many other options available as well, but they are generally
32853 needed for special purposes only.
32855 @node System-wide configuration
32856 @section System-wide configuration and settings
32857 @cindex system-wide init file
32859 @value{GDBN} can be configured to have a system-wide init file;
32860 this file will be read and executed at startup (@pxref{Startup, , What
32861 @value{GDBN} does during startup}).
32863 Here is the corresponding configure option:
32866 @item --with-system-gdbinit=@var{file}
32867 Specify that the default location of the system-wide init file is
32871 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32872 it may be subject to relocation. Two possible cases:
32876 If the default location of this init file contains @file{$prefix},
32877 it will be subject to relocation. Suppose that the configure options
32878 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32879 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32880 init file is looked for as @file{$install/etc/gdbinit} instead of
32881 @file{$prefix/etc/gdbinit}.
32884 By contrast, if the default location does not contain the prefix,
32885 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32886 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32887 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32888 wherever @value{GDBN} is installed.
32891 @node Maintenance Commands
32892 @appendix Maintenance Commands
32893 @cindex maintenance commands
32894 @cindex internal commands
32896 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32897 includes a number of commands intended for @value{GDBN} developers,
32898 that are not documented elsewhere in this manual. These commands are
32899 provided here for reference. (For commands that turn on debugging
32900 messages, see @ref{Debugging Output}.)
32903 @kindex maint agent
32904 @kindex maint agent-eval
32905 @item maint agent @var{expression}
32906 @itemx maint agent-eval @var{expression}
32907 Translate the given @var{expression} into remote agent bytecodes.
32908 This command is useful for debugging the Agent Expression mechanism
32909 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32910 expression useful for data collection, such as by tracepoints, while
32911 @samp{maint agent-eval} produces an expression that evaluates directly
32912 to a result. For instance, a collection expression for @code{globa +
32913 globb} will include bytecodes to record four bytes of memory at each
32914 of the addresses of @code{globa} and @code{globb}, while discarding
32915 the result of the addition, while an evaluation expression will do the
32916 addition and return the sum.
32918 @kindex maint info breakpoints
32919 @item @anchor{maint info breakpoints}maint info breakpoints
32920 Using the same format as @samp{info breakpoints}, display both the
32921 breakpoints you've set explicitly, and those @value{GDBN} is using for
32922 internal purposes. Internal breakpoints are shown with negative
32923 breakpoint numbers. The type column identifies what kind of breakpoint
32928 Normal, explicitly set breakpoint.
32931 Normal, explicitly set watchpoint.
32934 Internal breakpoint, used to handle correctly stepping through
32935 @code{longjmp} calls.
32937 @item longjmp resume
32938 Internal breakpoint at the target of a @code{longjmp}.
32941 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32944 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32947 Shared library events.
32951 @kindex set displaced-stepping
32952 @kindex show displaced-stepping
32953 @cindex displaced stepping support
32954 @cindex out-of-line single-stepping
32955 @item set displaced-stepping
32956 @itemx show displaced-stepping
32957 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32958 if the target supports it. Displaced stepping is a way to single-step
32959 over breakpoints without removing them from the inferior, by executing
32960 an out-of-line copy of the instruction that was originally at the
32961 breakpoint location. It is also known as out-of-line single-stepping.
32964 @item set displaced-stepping on
32965 If the target architecture supports it, @value{GDBN} will use
32966 displaced stepping to step over breakpoints.
32968 @item set displaced-stepping off
32969 @value{GDBN} will not use displaced stepping to step over breakpoints,
32970 even if such is supported by the target architecture.
32972 @cindex non-stop mode, and @samp{set displaced-stepping}
32973 @item set displaced-stepping auto
32974 This is the default mode. @value{GDBN} will use displaced stepping
32975 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32976 architecture supports displaced stepping.
32979 @kindex maint check-symtabs
32980 @item maint check-symtabs
32981 Check the consistency of psymtabs and symtabs.
32983 @kindex maint cplus first_component
32984 @item maint cplus first_component @var{name}
32985 Print the first C@t{++} class/namespace component of @var{name}.
32987 @kindex maint cplus namespace
32988 @item maint cplus namespace
32989 Print the list of possible C@t{++} namespaces.
32991 @kindex maint demangle
32992 @item maint demangle @var{name}
32993 Demangle a C@t{++} or Objective-C mangled @var{name}.
32995 @kindex maint deprecate
32996 @kindex maint undeprecate
32997 @cindex deprecated commands
32998 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32999 @itemx maint undeprecate @var{command}
33000 Deprecate or undeprecate the named @var{command}. Deprecated commands
33001 cause @value{GDBN} to issue a warning when you use them. The optional
33002 argument @var{replacement} says which newer command should be used in
33003 favor of the deprecated one; if it is given, @value{GDBN} will mention
33004 the replacement as part of the warning.
33006 @kindex maint dump-me
33007 @item maint dump-me
33008 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33009 Cause a fatal signal in the debugger and force it to dump its core.
33010 This is supported only on systems which support aborting a program
33011 with the @code{SIGQUIT} signal.
33013 @kindex maint internal-error
33014 @kindex maint internal-warning
33015 @item maint internal-error @r{[}@var{message-text}@r{]}
33016 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33017 Cause @value{GDBN} to call the internal function @code{internal_error}
33018 or @code{internal_warning} and hence behave as though an internal error
33019 or internal warning has been detected. In addition to reporting the
33020 internal problem, these functions give the user the opportunity to
33021 either quit @value{GDBN} or create a core file of the current
33022 @value{GDBN} session.
33024 These commands take an optional parameter @var{message-text} that is
33025 used as the text of the error or warning message.
33027 Here's an example of using @code{internal-error}:
33030 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33031 @dots{}/maint.c:121: internal-error: testing, 1, 2
33032 A problem internal to GDB has been detected. Further
33033 debugging may prove unreliable.
33034 Quit this debugging session? (y or n) @kbd{n}
33035 Create a core file? (y or n) @kbd{n}
33039 @cindex @value{GDBN} internal error
33040 @cindex internal errors, control of @value{GDBN} behavior
33042 @kindex maint set internal-error
33043 @kindex maint show internal-error
33044 @kindex maint set internal-warning
33045 @kindex maint show internal-warning
33046 @item maint set internal-error @var{action} [ask|yes|no]
33047 @itemx maint show internal-error @var{action}
33048 @itemx maint set internal-warning @var{action} [ask|yes|no]
33049 @itemx maint show internal-warning @var{action}
33050 When @value{GDBN} reports an internal problem (error or warning) it
33051 gives the user the opportunity to both quit @value{GDBN} and create a
33052 core file of the current @value{GDBN} session. These commands let you
33053 override the default behaviour for each particular @var{action},
33054 described in the table below.
33058 You can specify that @value{GDBN} should always (yes) or never (no)
33059 quit. The default is to ask the user what to do.
33062 You can specify that @value{GDBN} should always (yes) or never (no)
33063 create a core file. The default is to ask the user what to do.
33066 @kindex maint packet
33067 @item maint packet @var{text}
33068 If @value{GDBN} is talking to an inferior via the serial protocol,
33069 then this command sends the string @var{text} to the inferior, and
33070 displays the response packet. @value{GDBN} supplies the initial
33071 @samp{$} character, the terminating @samp{#} character, and the
33074 @kindex maint print architecture
33075 @item maint print architecture @r{[}@var{file}@r{]}
33076 Print the entire architecture configuration. The optional argument
33077 @var{file} names the file where the output goes.
33079 @kindex maint print c-tdesc
33080 @item maint print c-tdesc
33081 Print the current target description (@pxref{Target Descriptions}) as
33082 a C source file. The created source file can be used in @value{GDBN}
33083 when an XML parser is not available to parse the description.
33085 @kindex maint print dummy-frames
33086 @item maint print dummy-frames
33087 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33090 (@value{GDBP}) @kbd{b add}
33092 (@value{GDBP}) @kbd{print add(2,3)}
33093 Breakpoint 2, add (a=2, b=3) at @dots{}
33095 The program being debugged stopped while in a function called from GDB.
33097 (@value{GDBP}) @kbd{maint print dummy-frames}
33098 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33099 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33100 call_lo=0x01014000 call_hi=0x01014001
33104 Takes an optional file parameter.
33106 @kindex maint print registers
33107 @kindex maint print raw-registers
33108 @kindex maint print cooked-registers
33109 @kindex maint print register-groups
33110 @kindex maint print remote-registers
33111 @item maint print registers @r{[}@var{file}@r{]}
33112 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33113 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33114 @itemx maint print register-groups @r{[}@var{file}@r{]}
33115 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33116 Print @value{GDBN}'s internal register data structures.
33118 The command @code{maint print raw-registers} includes the contents of
33119 the raw register cache; the command @code{maint print
33120 cooked-registers} includes the (cooked) value of all registers,
33121 including registers which aren't available on the target nor visible
33122 to user; the command @code{maint print register-groups} includes the
33123 groups that each register is a member of; and the command @code{maint
33124 print remote-registers} includes the remote target's register numbers
33125 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33126 @value{GDBN} Internals}.
33128 These commands take an optional parameter, a file name to which to
33129 write the information.
33131 @kindex maint print reggroups
33132 @item maint print reggroups @r{[}@var{file}@r{]}
33133 Print @value{GDBN}'s internal register group data structures. The
33134 optional argument @var{file} tells to what file to write the
33137 The register groups info looks like this:
33140 (@value{GDBP}) @kbd{maint print reggroups}
33153 This command forces @value{GDBN} to flush its internal register cache.
33155 @kindex maint print objfiles
33156 @cindex info for known object files
33157 @item maint print objfiles
33158 Print a dump of all known object files. For each object file, this
33159 command prints its name, address in memory, and all of its psymtabs
33162 @kindex maint print section-scripts
33163 @cindex info for known .debug_gdb_scripts-loaded scripts
33164 @item maint print section-scripts [@var{regexp}]
33165 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33166 If @var{regexp} is specified, only print scripts loaded by object files
33167 matching @var{regexp}.
33168 For each script, this command prints its name as specified in the objfile,
33169 and the full path if known.
33170 @xref{.debug_gdb_scripts section}.
33172 @kindex maint print statistics
33173 @cindex bcache statistics
33174 @item maint print statistics
33175 This command prints, for each object file in the program, various data
33176 about that object file followed by the byte cache (@dfn{bcache})
33177 statistics for the object file. The objfile data includes the number
33178 of minimal, partial, full, and stabs symbols, the number of types
33179 defined by the objfile, the number of as yet unexpanded psym tables,
33180 the number of line tables and string tables, and the amount of memory
33181 used by the various tables. The bcache statistics include the counts,
33182 sizes, and counts of duplicates of all and unique objects, max,
33183 average, and median entry size, total memory used and its overhead and
33184 savings, and various measures of the hash table size and chain
33187 @kindex maint print target-stack
33188 @cindex target stack description
33189 @item maint print target-stack
33190 A @dfn{target} is an interface between the debugger and a particular
33191 kind of file or process. Targets can be stacked in @dfn{strata},
33192 so that more than one target can potentially respond to a request.
33193 In particular, memory accesses will walk down the stack of targets
33194 until they find a target that is interested in handling that particular
33197 This command prints a short description of each layer that was pushed on
33198 the @dfn{target stack}, starting from the top layer down to the bottom one.
33200 @kindex maint print type
33201 @cindex type chain of a data type
33202 @item maint print type @var{expr}
33203 Print the type chain for a type specified by @var{expr}. The argument
33204 can be either a type name or a symbol. If it is a symbol, the type of
33205 that symbol is described. The type chain produced by this command is
33206 a recursive definition of the data type as stored in @value{GDBN}'s
33207 data structures, including its flags and contained types.
33209 @kindex maint set dwarf2 always-disassemble
33210 @kindex maint show dwarf2 always-disassemble
33211 @item maint set dwarf2 always-disassemble
33212 @item maint show dwarf2 always-disassemble
33213 Control the behavior of @code{info address} when using DWARF debugging
33216 The default is @code{off}, which means that @value{GDBN} should try to
33217 describe a variable's location in an easily readable format. When
33218 @code{on}, @value{GDBN} will instead display the DWARF location
33219 expression in an assembly-like format. Note that some locations are
33220 too complex for @value{GDBN} to describe simply; in this case you will
33221 always see the disassembly form.
33223 Here is an example of the resulting disassembly:
33226 (gdb) info addr argc
33227 Symbol "argc" is a complex DWARF expression:
33231 For more information on these expressions, see
33232 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33234 @kindex maint set dwarf2 max-cache-age
33235 @kindex maint show dwarf2 max-cache-age
33236 @item maint set dwarf2 max-cache-age
33237 @itemx maint show dwarf2 max-cache-age
33238 Control the DWARF 2 compilation unit cache.
33240 @cindex DWARF 2 compilation units cache
33241 In object files with inter-compilation-unit references, such as those
33242 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33243 reader needs to frequently refer to previously read compilation units.
33244 This setting controls how long a compilation unit will remain in the
33245 cache if it is not referenced. A higher limit means that cached
33246 compilation units will be stored in memory longer, and more total
33247 memory will be used. Setting it to zero disables caching, which will
33248 slow down @value{GDBN} startup, but reduce memory consumption.
33250 @kindex maint set profile
33251 @kindex maint show profile
33252 @cindex profiling GDB
33253 @item maint set profile
33254 @itemx maint show profile
33255 Control profiling of @value{GDBN}.
33257 Profiling will be disabled until you use the @samp{maint set profile}
33258 command to enable it. When you enable profiling, the system will begin
33259 collecting timing and execution count data; when you disable profiling or
33260 exit @value{GDBN}, the results will be written to a log file. Remember that
33261 if you use profiling, @value{GDBN} will overwrite the profiling log file
33262 (often called @file{gmon.out}). If you have a record of important profiling
33263 data in a @file{gmon.out} file, be sure to move it to a safe location.
33265 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33266 compiled with the @samp{-pg} compiler option.
33268 @kindex maint set show-debug-regs
33269 @kindex maint show show-debug-regs
33270 @cindex hardware debug registers
33271 @item maint set show-debug-regs
33272 @itemx maint show show-debug-regs
33273 Control whether to show variables that mirror the hardware debug
33274 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33275 enabled, the debug registers values are shown when @value{GDBN} inserts or
33276 removes a hardware breakpoint or watchpoint, and when the inferior
33277 triggers a hardware-assisted breakpoint or watchpoint.
33279 @kindex maint set show-all-tib
33280 @kindex maint show show-all-tib
33281 @item maint set show-all-tib
33282 @itemx maint show show-all-tib
33283 Control whether to show all non zero areas within a 1k block starting
33284 at thread local base, when using the @samp{info w32 thread-information-block}
33287 @kindex maint space
33288 @cindex memory used by commands
33290 Control whether to display memory usage for each command. If set to a
33291 nonzero value, @value{GDBN} will display how much memory each command
33292 took, following the command's own output. This can also be requested
33293 by invoking @value{GDBN} with the @option{--statistics} command-line
33294 switch (@pxref{Mode Options}).
33297 @cindex time of command execution
33299 Control whether to display the execution time of @value{GDBN} for each command.
33300 If set to a nonzero value, @value{GDBN} will display how much time it
33301 took to execute each command, following the command's own output.
33302 Both CPU time and wallclock time are printed.
33303 Printing both is useful when trying to determine whether the cost is
33304 CPU or, e.g., disk/network, latency.
33305 Note that the CPU time printed is for @value{GDBN} only, it does not include
33306 the execution time of the inferior because there's no mechanism currently
33307 to compute how much time was spent by @value{GDBN} and how much time was
33308 spent by the program been debugged.
33309 This can also be requested by invoking @value{GDBN} with the
33310 @option{--statistics} command-line switch (@pxref{Mode Options}).
33312 @kindex maint translate-address
33313 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33314 Find the symbol stored at the location specified by the address
33315 @var{addr} and an optional section name @var{section}. If found,
33316 @value{GDBN} prints the name of the closest symbol and an offset from
33317 the symbol's location to the specified address. This is similar to
33318 the @code{info address} command (@pxref{Symbols}), except that this
33319 command also allows to find symbols in other sections.
33321 If section was not specified, the section in which the symbol was found
33322 is also printed. For dynamically linked executables, the name of
33323 executable or shared library containing the symbol is printed as well.
33327 The following command is useful for non-interactive invocations of
33328 @value{GDBN}, such as in the test suite.
33331 @item set watchdog @var{nsec}
33332 @kindex set watchdog
33333 @cindex watchdog timer
33334 @cindex timeout for commands
33335 Set the maximum number of seconds @value{GDBN} will wait for the
33336 target operation to finish. If this time expires, @value{GDBN}
33337 reports and error and the command is aborted.
33339 @item show watchdog
33340 Show the current setting of the target wait timeout.
33343 @node Remote Protocol
33344 @appendix @value{GDBN} Remote Serial Protocol
33349 * Stop Reply Packets::
33350 * General Query Packets::
33351 * Architecture-Specific Protocol Details::
33352 * Tracepoint Packets::
33353 * Host I/O Packets::
33355 * Notification Packets::
33356 * Remote Non-Stop::
33357 * Packet Acknowledgment::
33359 * File-I/O Remote Protocol Extension::
33360 * Library List Format::
33361 * Library List Format for SVR4 Targets::
33362 * Memory Map Format::
33363 * Thread List Format::
33364 * Traceframe Info Format::
33370 There may be occasions when you need to know something about the
33371 protocol---for example, if there is only one serial port to your target
33372 machine, you might want your program to do something special if it
33373 recognizes a packet meant for @value{GDBN}.
33375 In the examples below, @samp{->} and @samp{<-} are used to indicate
33376 transmitted and received data, respectively.
33378 @cindex protocol, @value{GDBN} remote serial
33379 @cindex serial protocol, @value{GDBN} remote
33380 @cindex remote serial protocol
33381 All @value{GDBN} commands and responses (other than acknowledgments
33382 and notifications, see @ref{Notification Packets}) are sent as a
33383 @var{packet}. A @var{packet} is introduced with the character
33384 @samp{$}, the actual @var{packet-data}, and the terminating character
33385 @samp{#} followed by a two-digit @var{checksum}:
33388 @code{$}@var{packet-data}@code{#}@var{checksum}
33392 @cindex checksum, for @value{GDBN} remote
33394 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33395 characters between the leading @samp{$} and the trailing @samp{#} (an
33396 eight bit unsigned checksum).
33398 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33399 specification also included an optional two-digit @var{sequence-id}:
33402 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33405 @cindex sequence-id, for @value{GDBN} remote
33407 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33408 has never output @var{sequence-id}s. Stubs that handle packets added
33409 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33411 When either the host or the target machine receives a packet, the first
33412 response expected is an acknowledgment: either @samp{+} (to indicate
33413 the package was received correctly) or @samp{-} (to request
33417 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33422 The @samp{+}/@samp{-} acknowledgments can be disabled
33423 once a connection is established.
33424 @xref{Packet Acknowledgment}, for details.
33426 The host (@value{GDBN}) sends @var{command}s, and the target (the
33427 debugging stub incorporated in your program) sends a @var{response}. In
33428 the case of step and continue @var{command}s, the response is only sent
33429 when the operation has completed, and the target has again stopped all
33430 threads in all attached processes. This is the default all-stop mode
33431 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33432 execution mode; see @ref{Remote Non-Stop}, for details.
33434 @var{packet-data} consists of a sequence of characters with the
33435 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33438 @cindex remote protocol, field separator
33439 Fields within the packet should be separated using @samp{,} @samp{;} or
33440 @samp{:}. Except where otherwise noted all numbers are represented in
33441 @sc{hex} with leading zeros suppressed.
33443 Implementors should note that prior to @value{GDBN} 5.0, the character
33444 @samp{:} could not appear as the third character in a packet (as it
33445 would potentially conflict with the @var{sequence-id}).
33447 @cindex remote protocol, binary data
33448 @anchor{Binary Data}
33449 Binary data in most packets is encoded either as two hexadecimal
33450 digits per byte of binary data. This allowed the traditional remote
33451 protocol to work over connections which were only seven-bit clean.
33452 Some packets designed more recently assume an eight-bit clean
33453 connection, and use a more efficient encoding to send and receive
33456 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33457 as an escape character. Any escaped byte is transmitted as the escape
33458 character followed by the original character XORed with @code{0x20}.
33459 For example, the byte @code{0x7d} would be transmitted as the two
33460 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33461 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33462 @samp{@}}) must always be escaped. Responses sent by the stub
33463 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33464 is not interpreted as the start of a run-length encoded sequence
33467 Response @var{data} can be run-length encoded to save space.
33468 Run-length encoding replaces runs of identical characters with one
33469 instance of the repeated character, followed by a @samp{*} and a
33470 repeat count. The repeat count is itself sent encoded, to avoid
33471 binary characters in @var{data}: a value of @var{n} is sent as
33472 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33473 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33474 code 32) for a repeat count of 3. (This is because run-length
33475 encoding starts to win for counts 3 or more.) Thus, for example,
33476 @samp{0* } is a run-length encoding of ``0000'': the space character
33477 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33480 The printable characters @samp{#} and @samp{$} or with a numeric value
33481 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33482 seven repeats (@samp{$}) can be expanded using a repeat count of only
33483 five (@samp{"}). For example, @samp{00000000} can be encoded as
33486 The error response returned for some packets includes a two character
33487 error number. That number is not well defined.
33489 @cindex empty response, for unsupported packets
33490 For any @var{command} not supported by the stub, an empty response
33491 (@samp{$#00}) should be returned. That way it is possible to extend the
33492 protocol. A newer @value{GDBN} can tell if a packet is supported based
33495 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33496 commands for register access, and the @samp{m} and @samp{M} commands
33497 for memory access. Stubs that only control single-threaded targets
33498 can implement run control with the @samp{c} (continue), and @samp{s}
33499 (step) commands. Stubs that support multi-threading targets should
33500 support the @samp{vCont} command. All other commands are optional.
33505 The following table provides a complete list of all currently defined
33506 @var{command}s and their corresponding response @var{data}.
33507 @xref{File-I/O Remote Protocol Extension}, for details about the File
33508 I/O extension of the remote protocol.
33510 Each packet's description has a template showing the packet's overall
33511 syntax, followed by an explanation of the packet's meaning. We
33512 include spaces in some of the templates for clarity; these are not
33513 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33514 separate its components. For example, a template like @samp{foo
33515 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33516 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33517 @var{baz}. @value{GDBN} does not transmit a space character between the
33518 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33521 @cindex @var{thread-id}, in remote protocol
33522 @anchor{thread-id syntax}
33523 Several packets and replies include a @var{thread-id} field to identify
33524 a thread. Normally these are positive numbers with a target-specific
33525 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33526 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33529 In addition, the remote protocol supports a multiprocess feature in
33530 which the @var{thread-id} syntax is extended to optionally include both
33531 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33532 The @var{pid} (process) and @var{tid} (thread) components each have the
33533 format described above: a positive number with target-specific
33534 interpretation formatted as a big-endian hex string, literal @samp{-1}
33535 to indicate all processes or threads (respectively), or @samp{0} to
33536 indicate an arbitrary process or thread. Specifying just a process, as
33537 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33538 error to specify all processes but a specific thread, such as
33539 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33540 for those packets and replies explicitly documented to include a process
33541 ID, rather than a @var{thread-id}.
33543 The multiprocess @var{thread-id} syntax extensions are only used if both
33544 @value{GDBN} and the stub report support for the @samp{multiprocess}
33545 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33548 Note that all packet forms beginning with an upper- or lower-case
33549 letter, other than those described here, are reserved for future use.
33551 Here are the packet descriptions.
33556 @cindex @samp{!} packet
33557 @anchor{extended mode}
33558 Enable extended mode. In extended mode, the remote server is made
33559 persistent. The @samp{R} packet is used to restart the program being
33565 The remote target both supports and has enabled extended mode.
33569 @cindex @samp{?} packet
33570 Indicate the reason the target halted. The reply is the same as for
33571 step and continue. This packet has a special interpretation when the
33572 target is in non-stop mode; see @ref{Remote Non-Stop}.
33575 @xref{Stop Reply Packets}, for the reply specifications.
33577 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33578 @cindex @samp{A} packet
33579 Initialized @code{argv[]} array passed into program. @var{arglen}
33580 specifies the number of bytes in the hex encoded byte stream
33581 @var{arg}. See @code{gdbserver} for more details.
33586 The arguments were set.
33592 @cindex @samp{b} packet
33593 (Don't use this packet; its behavior is not well-defined.)
33594 Change the serial line speed to @var{baud}.
33596 JTC: @emph{When does the transport layer state change? When it's
33597 received, or after the ACK is transmitted. In either case, there are
33598 problems if the command or the acknowledgment packet is dropped.}
33600 Stan: @emph{If people really wanted to add something like this, and get
33601 it working for the first time, they ought to modify ser-unix.c to send
33602 some kind of out-of-band message to a specially-setup stub and have the
33603 switch happen "in between" packets, so that from remote protocol's point
33604 of view, nothing actually happened.}
33606 @item B @var{addr},@var{mode}
33607 @cindex @samp{B} packet
33608 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33609 breakpoint at @var{addr}.
33611 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33612 (@pxref{insert breakpoint or watchpoint packet}).
33614 @cindex @samp{bc} packet
33617 Backward continue. Execute the target system in reverse. No parameter.
33618 @xref{Reverse Execution}, for more information.
33621 @xref{Stop Reply Packets}, for the reply specifications.
33623 @cindex @samp{bs} packet
33626 Backward single step. Execute one instruction in reverse. No parameter.
33627 @xref{Reverse Execution}, for more information.
33630 @xref{Stop Reply Packets}, for the reply specifications.
33632 @item c @r{[}@var{addr}@r{]}
33633 @cindex @samp{c} packet
33634 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33635 resume at current address.
33637 This packet is deprecated for multi-threading support. @xref{vCont
33641 @xref{Stop Reply Packets}, for the reply specifications.
33643 @item C @var{sig}@r{[};@var{addr}@r{]}
33644 @cindex @samp{C} packet
33645 Continue with signal @var{sig} (hex signal number). If
33646 @samp{;@var{addr}} is omitted, resume at same address.
33648 This packet is deprecated for multi-threading support. @xref{vCont
33652 @xref{Stop Reply Packets}, for the reply specifications.
33655 @cindex @samp{d} packet
33658 Don't use this packet; instead, define a general set packet
33659 (@pxref{General Query Packets}).
33663 @cindex @samp{D} packet
33664 The first form of the packet is used to detach @value{GDBN} from the
33665 remote system. It is sent to the remote target
33666 before @value{GDBN} disconnects via the @code{detach} command.
33668 The second form, including a process ID, is used when multiprocess
33669 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33670 detach only a specific process. The @var{pid} is specified as a
33671 big-endian hex string.
33681 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33682 @cindex @samp{F} packet
33683 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33684 This is part of the File-I/O protocol extension. @xref{File-I/O
33685 Remote Protocol Extension}, for the specification.
33688 @anchor{read registers packet}
33689 @cindex @samp{g} packet
33690 Read general registers.
33694 @item @var{XX@dots{}}
33695 Each byte of register data is described by two hex digits. The bytes
33696 with the register are transmitted in target byte order. The size of
33697 each register and their position within the @samp{g} packet are
33698 determined by the @value{GDBN} internal gdbarch functions
33699 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33700 specification of several standard @samp{g} packets is specified below.
33702 When reading registers from a trace frame (@pxref{Analyze Collected
33703 Data,,Using the Collected Data}), the stub may also return a string of
33704 literal @samp{x}'s in place of the register data digits, to indicate
33705 that the corresponding register has not been collected, thus its value
33706 is unavailable. For example, for an architecture with 4 registers of
33707 4 bytes each, the following reply indicates to @value{GDBN} that
33708 registers 0 and 2 have not been collected, while registers 1 and 3
33709 have been collected, and both have zero value:
33713 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33720 @item G @var{XX@dots{}}
33721 @cindex @samp{G} packet
33722 Write general registers. @xref{read registers packet}, for a
33723 description of the @var{XX@dots{}} data.
33733 @item H @var{op} @var{thread-id}
33734 @cindex @samp{H} packet
33735 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33736 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33737 it should be @samp{c} for step and continue operations (note that this
33738 is deprecated, supporting the @samp{vCont} command is a better
33739 option), @samp{g} for other operations. The thread designator
33740 @var{thread-id} has the format and interpretation described in
33741 @ref{thread-id syntax}.
33752 @c 'H': How restrictive (or permissive) is the thread model. If a
33753 @c thread is selected and stopped, are other threads allowed
33754 @c to continue to execute? As I mentioned above, I think the
33755 @c semantics of each command when a thread is selected must be
33756 @c described. For example:
33758 @c 'g': If the stub supports threads and a specific thread is
33759 @c selected, returns the register block from that thread;
33760 @c otherwise returns current registers.
33762 @c 'G' If the stub supports threads and a specific thread is
33763 @c selected, sets the registers of the register block of
33764 @c that thread; otherwise sets current registers.
33766 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33767 @anchor{cycle step packet}
33768 @cindex @samp{i} packet
33769 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33770 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33771 step starting at that address.
33774 @cindex @samp{I} packet
33775 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33779 @cindex @samp{k} packet
33782 FIXME: @emph{There is no description of how to operate when a specific
33783 thread context has been selected (i.e.@: does 'k' kill only that
33786 @item m @var{addr},@var{length}
33787 @cindex @samp{m} packet
33788 Read @var{length} bytes of memory starting at address @var{addr}.
33789 Note that @var{addr} may not be aligned to any particular boundary.
33791 The stub need not use any particular size or alignment when gathering
33792 data from memory for the response; even if @var{addr} is word-aligned
33793 and @var{length} is a multiple of the word size, the stub is free to
33794 use byte accesses, or not. For this reason, this packet may not be
33795 suitable for accessing memory-mapped I/O devices.
33796 @cindex alignment of remote memory accesses
33797 @cindex size of remote memory accesses
33798 @cindex memory, alignment and size of remote accesses
33802 @item @var{XX@dots{}}
33803 Memory contents; each byte is transmitted as a two-digit hexadecimal
33804 number. The reply may contain fewer bytes than requested if the
33805 server was able to read only part of the region of memory.
33810 @item M @var{addr},@var{length}:@var{XX@dots{}}
33811 @cindex @samp{M} packet
33812 Write @var{length} bytes of memory starting at address @var{addr}.
33813 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33814 hexadecimal number.
33821 for an error (this includes the case where only part of the data was
33826 @cindex @samp{p} packet
33827 Read the value of register @var{n}; @var{n} is in hex.
33828 @xref{read registers packet}, for a description of how the returned
33829 register value is encoded.
33833 @item @var{XX@dots{}}
33834 the register's value
33838 Indicating an unrecognized @var{query}.
33841 @item P @var{n@dots{}}=@var{r@dots{}}
33842 @anchor{write register packet}
33843 @cindex @samp{P} packet
33844 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33845 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33846 digits for each byte in the register (target byte order).
33856 @item q @var{name} @var{params}@dots{}
33857 @itemx Q @var{name} @var{params}@dots{}
33858 @cindex @samp{q} packet
33859 @cindex @samp{Q} packet
33860 General query (@samp{q}) and set (@samp{Q}). These packets are
33861 described fully in @ref{General Query Packets}.
33864 @cindex @samp{r} packet
33865 Reset the entire system.
33867 Don't use this packet; use the @samp{R} packet instead.
33870 @cindex @samp{R} packet
33871 Restart the program being debugged. @var{XX}, while needed, is ignored.
33872 This packet is only available in extended mode (@pxref{extended mode}).
33874 The @samp{R} packet has no reply.
33876 @item s @r{[}@var{addr}@r{]}
33877 @cindex @samp{s} packet
33878 Single step. @var{addr} is the address at which to resume. If
33879 @var{addr} is omitted, resume at same address.
33881 This packet is deprecated for multi-threading support. @xref{vCont
33885 @xref{Stop Reply Packets}, for the reply specifications.
33887 @item S @var{sig}@r{[};@var{addr}@r{]}
33888 @anchor{step with signal packet}
33889 @cindex @samp{S} packet
33890 Step with signal. This is analogous to the @samp{C} packet, but
33891 requests a single-step, rather than a normal resumption of execution.
33893 This packet is deprecated for multi-threading support. @xref{vCont
33897 @xref{Stop Reply Packets}, for the reply specifications.
33899 @item t @var{addr}:@var{PP},@var{MM}
33900 @cindex @samp{t} packet
33901 Search backwards starting at address @var{addr} for a match with pattern
33902 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33903 @var{addr} must be at least 3 digits.
33905 @item T @var{thread-id}
33906 @cindex @samp{T} packet
33907 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33912 thread is still alive
33918 Packets starting with @samp{v} are identified by a multi-letter name,
33919 up to the first @samp{;} or @samp{?} (or the end of the packet).
33921 @item vAttach;@var{pid}
33922 @cindex @samp{vAttach} packet
33923 Attach to a new process with the specified process ID @var{pid}.
33924 The process ID is a
33925 hexadecimal integer identifying the process. In all-stop mode, all
33926 threads in the attached process are stopped; in non-stop mode, it may be
33927 attached without being stopped if that is supported by the target.
33929 @c In non-stop mode, on a successful vAttach, the stub should set the
33930 @c current thread to a thread of the newly-attached process. After
33931 @c attaching, GDB queries for the attached process's thread ID with qC.
33932 @c Also note that, from a user perspective, whether or not the
33933 @c target is stopped on attach in non-stop mode depends on whether you
33934 @c use the foreground or background version of the attach command, not
33935 @c on what vAttach does; GDB does the right thing with respect to either
33936 @c stopping or restarting threads.
33938 This packet is only available in extended mode (@pxref{extended mode}).
33944 @item @r{Any stop packet}
33945 for success in all-stop mode (@pxref{Stop Reply Packets})
33947 for success in non-stop mode (@pxref{Remote Non-Stop})
33950 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33951 @cindex @samp{vCont} packet
33952 @anchor{vCont packet}
33953 Resume the inferior, specifying different actions for each thread.
33954 If an action is specified with no @var{thread-id}, then it is applied to any
33955 threads that don't have a specific action specified; if no default action is
33956 specified then other threads should remain stopped in all-stop mode and
33957 in their current state in non-stop mode.
33958 Specifying multiple
33959 default actions is an error; specifying no actions is also an error.
33960 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33962 Currently supported actions are:
33968 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33972 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33977 The optional argument @var{addr} normally associated with the
33978 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33979 not supported in @samp{vCont}.
33981 The @samp{t} action is only relevant in non-stop mode
33982 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33983 A stop reply should be generated for any affected thread not already stopped.
33984 When a thread is stopped by means of a @samp{t} action,
33985 the corresponding stop reply should indicate that the thread has stopped with
33986 signal @samp{0}, regardless of whether the target uses some other signal
33987 as an implementation detail.
33990 @xref{Stop Reply Packets}, for the reply specifications.
33993 @cindex @samp{vCont?} packet
33994 Request a list of actions supported by the @samp{vCont} packet.
33998 @item vCont@r{[};@var{action}@dots{}@r{]}
33999 The @samp{vCont} packet is supported. Each @var{action} is a supported
34000 command in the @samp{vCont} packet.
34002 The @samp{vCont} packet is not supported.
34005 @item vFile:@var{operation}:@var{parameter}@dots{}
34006 @cindex @samp{vFile} packet
34007 Perform a file operation on the target system. For details,
34008 see @ref{Host I/O Packets}.
34010 @item vFlashErase:@var{addr},@var{length}
34011 @cindex @samp{vFlashErase} packet
34012 Direct the stub to erase @var{length} bytes of flash starting at
34013 @var{addr}. The region may enclose any number of flash blocks, but
34014 its start and end must fall on block boundaries, as indicated by the
34015 flash block size appearing in the memory map (@pxref{Memory Map
34016 Format}). @value{GDBN} groups flash memory programming operations
34017 together, and sends a @samp{vFlashDone} request after each group; the
34018 stub is allowed to delay erase operation until the @samp{vFlashDone}
34019 packet is received.
34021 The stub must support @samp{vCont} if it reports support for
34022 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34023 this case @samp{vCont} actions can be specified to apply to all threads
34024 in a process by using the @samp{p@var{pid}.-1} form of the
34035 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34036 @cindex @samp{vFlashWrite} packet
34037 Direct the stub to write data to flash address @var{addr}. The data
34038 is passed in binary form using the same encoding as for the @samp{X}
34039 packet (@pxref{Binary Data}). The memory ranges specified by
34040 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34041 not overlap, and must appear in order of increasing addresses
34042 (although @samp{vFlashErase} packets for higher addresses may already
34043 have been received; the ordering is guaranteed only between
34044 @samp{vFlashWrite} packets). If a packet writes to an address that was
34045 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34046 target-specific method, the results are unpredictable.
34054 for vFlashWrite addressing non-flash memory
34060 @cindex @samp{vFlashDone} packet
34061 Indicate to the stub that flash programming operation is finished.
34062 The stub is permitted to delay or batch the effects of a group of
34063 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34064 @samp{vFlashDone} packet is received. The contents of the affected
34065 regions of flash memory are unpredictable until the @samp{vFlashDone}
34066 request is completed.
34068 @item vKill;@var{pid}
34069 @cindex @samp{vKill} packet
34070 Kill the process with the specified process ID. @var{pid} is a
34071 hexadecimal integer identifying the process. This packet is used in
34072 preference to @samp{k} when multiprocess protocol extensions are
34073 supported; see @ref{multiprocess extensions}.
34083 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34084 @cindex @samp{vRun} packet
34085 Run the program @var{filename}, passing it each @var{argument} on its
34086 command line. The file and arguments are hex-encoded strings. If
34087 @var{filename} is an empty string, the stub may use a default program
34088 (e.g.@: the last program run). The program is created in the stopped
34091 @c FIXME: What about non-stop mode?
34093 This packet is only available in extended mode (@pxref{extended mode}).
34099 @item @r{Any stop packet}
34100 for success (@pxref{Stop Reply Packets})
34104 @anchor{vStopped packet}
34105 @cindex @samp{vStopped} packet
34107 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34108 reply and prompt for the stub to report another one.
34112 @item @r{Any stop packet}
34113 if there is another unreported stop event (@pxref{Stop Reply Packets})
34115 if there are no unreported stop events
34118 @item X @var{addr},@var{length}:@var{XX@dots{}}
34120 @cindex @samp{X} packet
34121 Write data to memory, where the data is transmitted in binary.
34122 @var{addr} is address, @var{length} is number of bytes,
34123 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34133 @item z @var{type},@var{addr},@var{kind}
34134 @itemx Z @var{type},@var{addr},@var{kind}
34135 @anchor{insert breakpoint or watchpoint packet}
34136 @cindex @samp{z} packet
34137 @cindex @samp{Z} packets
34138 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34139 watchpoint starting at address @var{address} of kind @var{kind}.
34141 Each breakpoint and watchpoint packet @var{type} is documented
34144 @emph{Implementation notes: A remote target shall return an empty string
34145 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34146 remote target shall support either both or neither of a given
34147 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34148 avoid potential problems with duplicate packets, the operations should
34149 be implemented in an idempotent way.}
34151 @item z0,@var{addr},@var{kind}
34152 @itemx Z0,@var{addr},@var{kind}
34153 @cindex @samp{z0} packet
34154 @cindex @samp{Z0} packet
34155 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34156 @var{addr} of type @var{kind}.
34158 A memory breakpoint is implemented by replacing the instruction at
34159 @var{addr} with a software breakpoint or trap instruction. The
34160 @var{kind} is target-specific and typically indicates the size of
34161 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34162 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34163 architectures have additional meanings for @var{kind};
34164 see @ref{Architecture-Specific Protocol Details}.
34166 @emph{Implementation note: It is possible for a target to copy or move
34167 code that contains memory breakpoints (e.g., when implementing
34168 overlays). The behavior of this packet, in the presence of such a
34169 target, is not defined.}
34181 @item z1,@var{addr},@var{kind}
34182 @itemx Z1,@var{addr},@var{kind}
34183 @cindex @samp{z1} packet
34184 @cindex @samp{Z1} packet
34185 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34186 address @var{addr}.
34188 A hardware breakpoint is implemented using a mechanism that is not
34189 dependant on being able to modify the target's memory. @var{kind}
34190 has the same meaning as in @samp{Z0} packets.
34192 @emph{Implementation note: A hardware breakpoint is not affected by code
34205 @item z2,@var{addr},@var{kind}
34206 @itemx Z2,@var{addr},@var{kind}
34207 @cindex @samp{z2} packet
34208 @cindex @samp{Z2} packet
34209 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34210 @var{kind} is interpreted as the number of bytes to watch.
34222 @item z3,@var{addr},@var{kind}
34223 @itemx Z3,@var{addr},@var{kind}
34224 @cindex @samp{z3} packet
34225 @cindex @samp{Z3} packet
34226 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34227 @var{kind} is interpreted as the number of bytes to watch.
34239 @item z4,@var{addr},@var{kind}
34240 @itemx Z4,@var{addr},@var{kind}
34241 @cindex @samp{z4} packet
34242 @cindex @samp{Z4} packet
34243 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34244 @var{kind} is interpreted as the number of bytes to watch.
34258 @node Stop Reply Packets
34259 @section Stop Reply Packets
34260 @cindex stop reply packets
34262 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34263 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34264 receive any of the below as a reply. Except for @samp{?}
34265 and @samp{vStopped}, that reply is only returned
34266 when the target halts. In the below the exact meaning of @dfn{signal
34267 number} is defined by the header @file{include/gdb/signals.h} in the
34268 @value{GDBN} source code.
34270 As in the description of request packets, we include spaces in the
34271 reply templates for clarity; these are not part of the reply packet's
34272 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34278 The program received signal number @var{AA} (a two-digit hexadecimal
34279 number). This is equivalent to a @samp{T} response with no
34280 @var{n}:@var{r} pairs.
34282 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34283 @cindex @samp{T} packet reply
34284 The program received signal number @var{AA} (a two-digit hexadecimal
34285 number). This is equivalent to an @samp{S} response, except that the
34286 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34287 and other information directly in the stop reply packet, reducing
34288 round-trip latency. Single-step and breakpoint traps are reported
34289 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34293 If @var{n} is a hexadecimal number, it is a register number, and the
34294 corresponding @var{r} gives that register's value. @var{r} is a
34295 series of bytes in target byte order, with each byte given by a
34296 two-digit hex number.
34299 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34300 the stopped thread, as specified in @ref{thread-id syntax}.
34303 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34304 the core on which the stop event was detected.
34307 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34308 specific event that stopped the target. The currently defined stop
34309 reasons are listed below. @var{aa} should be @samp{05}, the trap
34310 signal. At most one stop reason should be present.
34313 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34314 and go on to the next; this allows us to extend the protocol in the
34318 The currently defined stop reasons are:
34324 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34327 @cindex shared library events, remote reply
34329 The packet indicates that the loaded libraries have changed.
34330 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34331 list of loaded libraries. @var{r} is ignored.
34333 @cindex replay log events, remote reply
34335 The packet indicates that the target cannot continue replaying
34336 logged execution events, because it has reached the end (or the
34337 beginning when executing backward) of the log. The value of @var{r}
34338 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34339 for more information.
34343 @itemx W @var{AA} ; process:@var{pid}
34344 The process exited, and @var{AA} is the exit status. This is only
34345 applicable to certain targets.
34347 The second form of the response, including the process ID of the exited
34348 process, can be used only when @value{GDBN} has reported support for
34349 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34350 The @var{pid} is formatted as a big-endian hex string.
34353 @itemx X @var{AA} ; process:@var{pid}
34354 The process terminated with signal @var{AA}.
34356 The second form of the response, including the process ID of the
34357 terminated process, can be used only when @value{GDBN} has reported
34358 support for multiprocess protocol extensions; see @ref{multiprocess
34359 extensions}. The @var{pid} is formatted as a big-endian hex string.
34361 @item O @var{XX}@dots{}
34362 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34363 written as the program's console output. This can happen at any time
34364 while the program is running and the debugger should continue to wait
34365 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34367 @item F @var{call-id},@var{parameter}@dots{}
34368 @var{call-id} is the identifier which says which host system call should
34369 be called. This is just the name of the function. Translation into the
34370 correct system call is only applicable as it's defined in @value{GDBN}.
34371 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34374 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34375 this very system call.
34377 The target replies with this packet when it expects @value{GDBN} to
34378 call a host system call on behalf of the target. @value{GDBN} replies
34379 with an appropriate @samp{F} packet and keeps up waiting for the next
34380 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34381 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34382 Protocol Extension}, for more details.
34386 @node General Query Packets
34387 @section General Query Packets
34388 @cindex remote query requests
34390 Packets starting with @samp{q} are @dfn{general query packets};
34391 packets starting with @samp{Q} are @dfn{general set packets}. General
34392 query and set packets are a semi-unified form for retrieving and
34393 sending information to and from the stub.
34395 The initial letter of a query or set packet is followed by a name
34396 indicating what sort of thing the packet applies to. For example,
34397 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34398 definitions with the stub. These packet names follow some
34403 The name must not contain commas, colons or semicolons.
34405 Most @value{GDBN} query and set packets have a leading upper case
34408 The names of custom vendor packets should use a company prefix, in
34409 lower case, followed by a period. For example, packets designed at
34410 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34411 foos) or @samp{Qacme.bar} (for setting bars).
34414 The name of a query or set packet should be separated from any
34415 parameters by a @samp{:}; the parameters themselves should be
34416 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34417 full packet name, and check for a separator or the end of the packet,
34418 in case two packet names share a common prefix. New packets should not begin
34419 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34420 packets predate these conventions, and have arguments without any terminator
34421 for the packet name; we suspect they are in widespread use in places that
34422 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34423 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34426 Like the descriptions of the other packets, each description here
34427 has a template showing the packet's overall syntax, followed by an
34428 explanation of the packet's meaning. We include spaces in some of the
34429 templates for clarity; these are not part of the packet's syntax. No
34430 @value{GDBN} packet uses spaces to separate its components.
34432 Here are the currently defined query and set packets:
34436 @item QAllow:@var{op}:@var{val}@dots{}
34437 @cindex @samp{QAllow} packet
34438 Specify which operations @value{GDBN} expects to request of the
34439 target, as a semicolon-separated list of operation name and value
34440 pairs. Possible values for @var{op} include @samp{WriteReg},
34441 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34442 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34443 indicating that @value{GDBN} will not request the operation, or 1,
34444 indicating that it may. (The target can then use this to set up its
34445 own internals optimally, for instance if the debugger never expects to
34446 insert breakpoints, it may not need to install its own trap handler.)
34449 @cindex current thread, remote request
34450 @cindex @samp{qC} packet
34451 Return the current thread ID.
34455 @item QC @var{thread-id}
34456 Where @var{thread-id} is a thread ID as documented in
34457 @ref{thread-id syntax}.
34458 @item @r{(anything else)}
34459 Any other reply implies the old thread ID.
34462 @item qCRC:@var{addr},@var{length}
34463 @cindex CRC of memory block, remote request
34464 @cindex @samp{qCRC} packet
34465 Compute the CRC checksum of a block of memory using CRC-32 defined in
34466 IEEE 802.3. The CRC is computed byte at a time, taking the most
34467 significant bit of each byte first. The initial pattern code
34468 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34470 @emph{Note:} This is the same CRC used in validating separate debug
34471 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34472 Files}). However the algorithm is slightly different. When validating
34473 separate debug files, the CRC is computed taking the @emph{least}
34474 significant bit of each byte first, and the final result is inverted to
34475 detect trailing zeros.
34480 An error (such as memory fault)
34481 @item C @var{crc32}
34482 The specified memory region's checksum is @var{crc32}.
34485 @item QDisableRandomization:@var{value}
34486 @cindex disable address space randomization, remote request
34487 @cindex @samp{QDisableRandomization} packet
34488 Some target operating systems will randomize the virtual address space
34489 of the inferior process as a security feature, but provide a feature
34490 to disable such randomization, e.g.@: to allow for a more deterministic
34491 debugging experience. On such systems, this packet with a @var{value}
34492 of 1 directs the target to disable address space randomization for
34493 processes subsequently started via @samp{vRun} packets, while a packet
34494 with a @var{value} of 0 tells the target to enable address space
34497 This packet is only available in extended mode (@pxref{extended mode}).
34502 The request succeeded.
34505 An error occurred. @var{nn} are hex digits.
34508 An empty reply indicates that @samp{QDisableRandomization} is not supported
34512 This packet is not probed by default; the remote stub must request it,
34513 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34514 This should only be done on targets that actually support disabling
34515 address space randomization.
34518 @itemx qsThreadInfo
34519 @cindex list active threads, remote request
34520 @cindex @samp{qfThreadInfo} packet
34521 @cindex @samp{qsThreadInfo} packet
34522 Obtain a list of all active thread IDs from the target (OS). Since there
34523 may be too many active threads to fit into one reply packet, this query
34524 works iteratively: it may require more than one query/reply sequence to
34525 obtain the entire list of threads. The first query of the sequence will
34526 be the @samp{qfThreadInfo} query; subsequent queries in the
34527 sequence will be the @samp{qsThreadInfo} query.
34529 NOTE: This packet replaces the @samp{qL} query (see below).
34533 @item m @var{thread-id}
34535 @item m @var{thread-id},@var{thread-id}@dots{}
34536 a comma-separated list of thread IDs
34538 (lower case letter @samp{L}) denotes end of list.
34541 In response to each query, the target will reply with a list of one or
34542 more thread IDs, separated by commas.
34543 @value{GDBN} will respond to each reply with a request for more thread
34544 ids (using the @samp{qs} form of the query), until the target responds
34545 with @samp{l} (lower-case ell, for @dfn{last}).
34546 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34549 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34550 @cindex get thread-local storage address, remote request
34551 @cindex @samp{qGetTLSAddr} packet
34552 Fetch the address associated with thread local storage specified
34553 by @var{thread-id}, @var{offset}, and @var{lm}.
34555 @var{thread-id} is the thread ID associated with the
34556 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34558 @var{offset} is the (big endian, hex encoded) offset associated with the
34559 thread local variable. (This offset is obtained from the debug
34560 information associated with the variable.)
34562 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34563 load module associated with the thread local storage. For example,
34564 a @sc{gnu}/Linux system will pass the link map address of the shared
34565 object associated with the thread local storage under consideration.
34566 Other operating environments may choose to represent the load module
34567 differently, so the precise meaning of this parameter will vary.
34571 @item @var{XX}@dots{}
34572 Hex encoded (big endian) bytes representing the address of the thread
34573 local storage requested.
34576 An error occurred. @var{nn} are hex digits.
34579 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34582 @item qGetTIBAddr:@var{thread-id}
34583 @cindex get thread information block address
34584 @cindex @samp{qGetTIBAddr} packet
34585 Fetch address of the Windows OS specific Thread Information Block.
34587 @var{thread-id} is the thread ID associated with the thread.
34591 @item @var{XX}@dots{}
34592 Hex encoded (big endian) bytes representing the linear address of the
34593 thread information block.
34596 An error occured. This means that either the thread was not found, or the
34597 address could not be retrieved.
34600 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34603 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34604 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34605 digit) is one to indicate the first query and zero to indicate a
34606 subsequent query; @var{threadcount} (two hex digits) is the maximum
34607 number of threads the response packet can contain; and @var{nextthread}
34608 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34609 returned in the response as @var{argthread}.
34611 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34615 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34616 Where: @var{count} (two hex digits) is the number of threads being
34617 returned; @var{done} (one hex digit) is zero to indicate more threads
34618 and one indicates no further threads; @var{argthreadid} (eight hex
34619 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34620 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34621 digits). See @code{remote.c:parse_threadlist_response()}.
34625 @cindex section offsets, remote request
34626 @cindex @samp{qOffsets} packet
34627 Get section offsets that the target used when relocating the downloaded
34632 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34633 Relocate the @code{Text} section by @var{xxx} from its original address.
34634 Relocate the @code{Data} section by @var{yyy} from its original address.
34635 If the object file format provides segment information (e.g.@: @sc{elf}
34636 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34637 segments by the supplied offsets.
34639 @emph{Note: while a @code{Bss} offset may be included in the response,
34640 @value{GDBN} ignores this and instead applies the @code{Data} offset
34641 to the @code{Bss} section.}
34643 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34644 Relocate the first segment of the object file, which conventionally
34645 contains program code, to a starting address of @var{xxx}. If
34646 @samp{DataSeg} is specified, relocate the second segment, which
34647 conventionally contains modifiable data, to a starting address of
34648 @var{yyy}. @value{GDBN} will report an error if the object file
34649 does not contain segment information, or does not contain at least
34650 as many segments as mentioned in the reply. Extra segments are
34651 kept at fixed offsets relative to the last relocated segment.
34654 @item qP @var{mode} @var{thread-id}
34655 @cindex thread information, remote request
34656 @cindex @samp{qP} packet
34657 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34658 encoded 32 bit mode; @var{thread-id} is a thread ID
34659 (@pxref{thread-id syntax}).
34661 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34664 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34668 @cindex non-stop mode, remote request
34669 @cindex @samp{QNonStop} packet
34671 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34672 @xref{Remote Non-Stop}, for more information.
34677 The request succeeded.
34680 An error occurred. @var{nn} are hex digits.
34683 An empty reply indicates that @samp{QNonStop} is not supported by
34687 This packet is not probed by default; the remote stub must request it,
34688 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34689 Use of this packet is controlled by the @code{set non-stop} command;
34690 @pxref{Non-Stop Mode}.
34692 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34693 @cindex pass signals to inferior, remote request
34694 @cindex @samp{QPassSignals} packet
34695 @anchor{QPassSignals}
34696 Each listed @var{signal} should be passed directly to the inferior process.
34697 Signals are numbered identically to continue packets and stop replies
34698 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34699 strictly greater than the previous item. These signals do not need to stop
34700 the inferior, or be reported to @value{GDBN}. All other signals should be
34701 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34702 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34703 new list. This packet improves performance when using @samp{handle
34704 @var{signal} nostop noprint pass}.
34709 The request succeeded.
34712 An error occurred. @var{nn} are hex digits.
34715 An empty reply indicates that @samp{QPassSignals} is not supported by
34719 Use of this packet is controlled by the @code{set remote pass-signals}
34720 command (@pxref{Remote Configuration, set remote pass-signals}).
34721 This packet is not probed by default; the remote stub must request it,
34722 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34724 @item qRcmd,@var{command}
34725 @cindex execute remote command, remote request
34726 @cindex @samp{qRcmd} packet
34727 @var{command} (hex encoded) is passed to the local interpreter for
34728 execution. Invalid commands should be reported using the output
34729 string. Before the final result packet, the target may also respond
34730 with a number of intermediate @samp{O@var{output}} console output
34731 packets. @emph{Implementors should note that providing access to a
34732 stubs's interpreter may have security implications}.
34737 A command response with no output.
34739 A command response with the hex encoded output string @var{OUTPUT}.
34741 Indicate a badly formed request.
34743 An empty reply indicates that @samp{qRcmd} is not recognized.
34746 (Note that the @code{qRcmd} packet's name is separated from the
34747 command by a @samp{,}, not a @samp{:}, contrary to the naming
34748 conventions above. Please don't use this packet as a model for new
34751 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34752 @cindex searching memory, in remote debugging
34753 @cindex @samp{qSearch:memory} packet
34754 @anchor{qSearch memory}
34755 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34756 @var{address} and @var{length} are encoded in hex.
34757 @var{search-pattern} is a sequence of bytes, hex encoded.
34762 The pattern was not found.
34764 The pattern was found at @var{address}.
34766 A badly formed request or an error was encountered while searching memory.
34768 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34771 @item QStartNoAckMode
34772 @cindex @samp{QStartNoAckMode} packet
34773 @anchor{QStartNoAckMode}
34774 Request that the remote stub disable the normal @samp{+}/@samp{-}
34775 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34780 The stub has switched to no-acknowledgment mode.
34781 @value{GDBN} acknowledges this reponse,
34782 but neither the stub nor @value{GDBN} shall send or expect further
34783 @samp{+}/@samp{-} acknowledgments in the current connection.
34785 An empty reply indicates that the stub does not support no-acknowledgment mode.
34788 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34789 @cindex supported packets, remote query
34790 @cindex features of the remote protocol
34791 @cindex @samp{qSupported} packet
34792 @anchor{qSupported}
34793 Tell the remote stub about features supported by @value{GDBN}, and
34794 query the stub for features it supports. This packet allows
34795 @value{GDBN} and the remote stub to take advantage of each others'
34796 features. @samp{qSupported} also consolidates multiple feature probes
34797 at startup, to improve @value{GDBN} performance---a single larger
34798 packet performs better than multiple smaller probe packets on
34799 high-latency links. Some features may enable behavior which must not
34800 be on by default, e.g.@: because it would confuse older clients or
34801 stubs. Other features may describe packets which could be
34802 automatically probed for, but are not. These features must be
34803 reported before @value{GDBN} will use them. This ``default
34804 unsupported'' behavior is not appropriate for all packets, but it
34805 helps to keep the initial connection time under control with new
34806 versions of @value{GDBN} which support increasing numbers of packets.
34810 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34811 The stub supports or does not support each returned @var{stubfeature},
34812 depending on the form of each @var{stubfeature} (see below for the
34815 An empty reply indicates that @samp{qSupported} is not recognized,
34816 or that no features needed to be reported to @value{GDBN}.
34819 The allowed forms for each feature (either a @var{gdbfeature} in the
34820 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34824 @item @var{name}=@var{value}
34825 The remote protocol feature @var{name} is supported, and associated
34826 with the specified @var{value}. The format of @var{value} depends
34827 on the feature, but it must not include a semicolon.
34829 The remote protocol feature @var{name} is supported, and does not
34830 need an associated value.
34832 The remote protocol feature @var{name} is not supported.
34834 The remote protocol feature @var{name} may be supported, and
34835 @value{GDBN} should auto-detect support in some other way when it is
34836 needed. This form will not be used for @var{gdbfeature} notifications,
34837 but may be used for @var{stubfeature} responses.
34840 Whenever the stub receives a @samp{qSupported} request, the
34841 supplied set of @value{GDBN} features should override any previous
34842 request. This allows @value{GDBN} to put the stub in a known
34843 state, even if the stub had previously been communicating with
34844 a different version of @value{GDBN}.
34846 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34851 This feature indicates whether @value{GDBN} supports multiprocess
34852 extensions to the remote protocol. @value{GDBN} does not use such
34853 extensions unless the stub also reports that it supports them by
34854 including @samp{multiprocess+} in its @samp{qSupported} reply.
34855 @xref{multiprocess extensions}, for details.
34858 This feature indicates that @value{GDBN} supports the XML target
34859 description. If the stub sees @samp{xmlRegisters=} with target
34860 specific strings separated by a comma, it will report register
34864 This feature indicates whether @value{GDBN} supports the
34865 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34866 instruction reply packet}).
34869 Stubs should ignore any unknown values for
34870 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34871 packet supports receiving packets of unlimited length (earlier
34872 versions of @value{GDBN} may reject overly long responses). Additional values
34873 for @var{gdbfeature} may be defined in the future to let the stub take
34874 advantage of new features in @value{GDBN}, e.g.@: incompatible
34875 improvements in the remote protocol---the @samp{multiprocess} feature is
34876 an example of such a feature. The stub's reply should be independent
34877 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34878 describes all the features it supports, and then the stub replies with
34879 all the features it supports.
34881 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34882 responses, as long as each response uses one of the standard forms.
34884 Some features are flags. A stub which supports a flag feature
34885 should respond with a @samp{+} form response. Other features
34886 require values, and the stub should respond with an @samp{=}
34889 Each feature has a default value, which @value{GDBN} will use if
34890 @samp{qSupported} is not available or if the feature is not mentioned
34891 in the @samp{qSupported} response. The default values are fixed; a
34892 stub is free to omit any feature responses that match the defaults.
34894 Not all features can be probed, but for those which can, the probing
34895 mechanism is useful: in some cases, a stub's internal
34896 architecture may not allow the protocol layer to know some information
34897 about the underlying target in advance. This is especially common in
34898 stubs which may be configured for multiple targets.
34900 These are the currently defined stub features and their properties:
34902 @multitable @columnfractions 0.35 0.2 0.12 0.2
34903 @c NOTE: The first row should be @headitem, but we do not yet require
34904 @c a new enough version of Texinfo (4.7) to use @headitem.
34906 @tab Value Required
34910 @item @samp{PacketSize}
34915 @item @samp{qXfer:auxv:read}
34920 @item @samp{qXfer:features:read}
34925 @item @samp{qXfer:libraries:read}
34930 @item @samp{qXfer:memory-map:read}
34935 @item @samp{qXfer:sdata:read}
34940 @item @samp{qXfer:spu:read}
34945 @item @samp{qXfer:spu:write}
34950 @item @samp{qXfer:siginfo:read}
34955 @item @samp{qXfer:siginfo:write}
34960 @item @samp{qXfer:threads:read}
34965 @item @samp{qXfer:traceframe-info:read}
34970 @item @samp{qXfer:fdpic:read}
34975 @item @samp{QNonStop}
34980 @item @samp{QPassSignals}
34985 @item @samp{QStartNoAckMode}
34990 @item @samp{multiprocess}
34995 @item @samp{ConditionalTracepoints}
35000 @item @samp{ReverseContinue}
35005 @item @samp{ReverseStep}
35010 @item @samp{TracepointSource}
35015 @item @samp{QAllow}
35020 @item @samp{QDisableRandomization}
35025 @item @samp{EnableDisableTracepoints}
35030 @item @samp{tracenz}
35037 These are the currently defined stub features, in more detail:
35040 @cindex packet size, remote protocol
35041 @item PacketSize=@var{bytes}
35042 The remote stub can accept packets up to at least @var{bytes} in
35043 length. @value{GDBN} will send packets up to this size for bulk
35044 transfers, and will never send larger packets. This is a limit on the
35045 data characters in the packet, including the frame and checksum.
35046 There is no trailing NUL byte in a remote protocol packet; if the stub
35047 stores packets in a NUL-terminated format, it should allow an extra
35048 byte in its buffer for the NUL. If this stub feature is not supported,
35049 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35051 @item qXfer:auxv:read
35052 The remote stub understands the @samp{qXfer:auxv:read} packet
35053 (@pxref{qXfer auxiliary vector read}).
35055 @item qXfer:features:read
35056 The remote stub understands the @samp{qXfer:features:read} packet
35057 (@pxref{qXfer target description read}).
35059 @item qXfer:libraries:read
35060 The remote stub understands the @samp{qXfer:libraries:read} packet
35061 (@pxref{qXfer library list read}).
35063 @item qXfer:libraries-svr4:read
35064 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35065 (@pxref{qXfer svr4 library list read}).
35067 @item qXfer:memory-map:read
35068 The remote stub understands the @samp{qXfer:memory-map:read} packet
35069 (@pxref{qXfer memory map read}).
35071 @item qXfer:sdata:read
35072 The remote stub understands the @samp{qXfer:sdata:read} packet
35073 (@pxref{qXfer sdata read}).
35075 @item qXfer:spu:read
35076 The remote stub understands the @samp{qXfer:spu:read} packet
35077 (@pxref{qXfer spu read}).
35079 @item qXfer:spu:write
35080 The remote stub understands the @samp{qXfer:spu:write} packet
35081 (@pxref{qXfer spu write}).
35083 @item qXfer:siginfo:read
35084 The remote stub understands the @samp{qXfer:siginfo:read} packet
35085 (@pxref{qXfer siginfo read}).
35087 @item qXfer:siginfo:write
35088 The remote stub understands the @samp{qXfer:siginfo:write} packet
35089 (@pxref{qXfer siginfo write}).
35091 @item qXfer:threads:read
35092 The remote stub understands the @samp{qXfer:threads:read} packet
35093 (@pxref{qXfer threads read}).
35095 @item qXfer:traceframe-info:read
35096 The remote stub understands the @samp{qXfer:traceframe-info:read}
35097 packet (@pxref{qXfer traceframe info read}).
35099 @item qXfer:fdpic:read
35100 The remote stub understands the @samp{qXfer:fdpic:read}
35101 packet (@pxref{qXfer fdpic loadmap read}).
35104 The remote stub understands the @samp{QNonStop} packet
35105 (@pxref{QNonStop}).
35108 The remote stub understands the @samp{QPassSignals} packet
35109 (@pxref{QPassSignals}).
35111 @item QStartNoAckMode
35112 The remote stub understands the @samp{QStartNoAckMode} packet and
35113 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35116 @anchor{multiprocess extensions}
35117 @cindex multiprocess extensions, in remote protocol
35118 The remote stub understands the multiprocess extensions to the remote
35119 protocol syntax. The multiprocess extensions affect the syntax of
35120 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35121 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35122 replies. Note that reporting this feature indicates support for the
35123 syntactic extensions only, not that the stub necessarily supports
35124 debugging of more than one process at a time. The stub must not use
35125 multiprocess extensions in packet replies unless @value{GDBN} has also
35126 indicated it supports them in its @samp{qSupported} request.
35128 @item qXfer:osdata:read
35129 The remote stub understands the @samp{qXfer:osdata:read} packet
35130 ((@pxref{qXfer osdata read}).
35132 @item ConditionalTracepoints
35133 The remote stub accepts and implements conditional expressions defined
35134 for tracepoints (@pxref{Tracepoint Conditions}).
35136 @item ReverseContinue
35137 The remote stub accepts and implements the reverse continue packet
35141 The remote stub accepts and implements the reverse step packet
35144 @item TracepointSource
35145 The remote stub understands the @samp{QTDPsrc} packet that supplies
35146 the source form of tracepoint definitions.
35149 The remote stub understands the @samp{QAllow} packet.
35151 @item QDisableRandomization
35152 The remote stub understands the @samp{QDisableRandomization} packet.
35154 @item StaticTracepoint
35155 @cindex static tracepoints, in remote protocol
35156 The remote stub supports static tracepoints.
35158 @item InstallInTrace
35159 @anchor{install tracepoint in tracing}
35160 The remote stub supports installing tracepoint in tracing.
35162 @item EnableDisableTracepoints
35163 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35164 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35165 to be enabled and disabled while a trace experiment is running.
35168 @cindex string tracing, in remote protocol
35169 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35170 See @ref{Bytecode Descriptions} for details about the bytecode.
35175 @cindex symbol lookup, remote request
35176 @cindex @samp{qSymbol} packet
35177 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35178 requests. Accept requests from the target for the values of symbols.
35183 The target does not need to look up any (more) symbols.
35184 @item qSymbol:@var{sym_name}
35185 The target requests the value of symbol @var{sym_name} (hex encoded).
35186 @value{GDBN} may provide the value by using the
35187 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35191 @item qSymbol:@var{sym_value}:@var{sym_name}
35192 Set the value of @var{sym_name} to @var{sym_value}.
35194 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35195 target has previously requested.
35197 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35198 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35204 The target does not need to look up any (more) symbols.
35205 @item qSymbol:@var{sym_name}
35206 The target requests the value of a new symbol @var{sym_name} (hex
35207 encoded). @value{GDBN} will continue to supply the values of symbols
35208 (if available), until the target ceases to request them.
35213 @item QTDisconnected
35220 @itemx qTMinFTPILen
35222 @xref{Tracepoint Packets}.
35224 @item qThreadExtraInfo,@var{thread-id}
35225 @cindex thread attributes info, remote request
35226 @cindex @samp{qThreadExtraInfo} packet
35227 Obtain a printable string description of a thread's attributes from
35228 the target OS. @var{thread-id} is a thread ID;
35229 see @ref{thread-id syntax}. This
35230 string may contain anything that the target OS thinks is interesting
35231 for @value{GDBN} to tell the user about the thread. The string is
35232 displayed in @value{GDBN}'s @code{info threads} display. Some
35233 examples of possible thread extra info strings are @samp{Runnable}, or
35234 @samp{Blocked on Mutex}.
35238 @item @var{XX}@dots{}
35239 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35240 comprising the printable string containing the extra information about
35241 the thread's attributes.
35244 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35245 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35246 conventions above. Please don't use this packet as a model for new
35265 @xref{Tracepoint Packets}.
35267 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35268 @cindex read special object, remote request
35269 @cindex @samp{qXfer} packet
35270 @anchor{qXfer read}
35271 Read uninterpreted bytes from the target's special data area
35272 identified by the keyword @var{object}. Request @var{length} bytes
35273 starting at @var{offset} bytes into the data. The content and
35274 encoding of @var{annex} is specific to @var{object}; it can supply
35275 additional details about what data to access.
35277 Here are the specific requests of this form defined so far. All
35278 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35279 formats, listed below.
35282 @item qXfer:auxv:read::@var{offset},@var{length}
35283 @anchor{qXfer auxiliary vector read}
35284 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35285 auxiliary vector}. Note @var{annex} must be empty.
35287 This packet is not probed by default; the remote stub must request it,
35288 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35290 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35291 @anchor{qXfer target description read}
35292 Access the @dfn{target description}. @xref{Target Descriptions}. The
35293 annex specifies which XML document to access. The main description is
35294 always loaded from the @samp{target.xml} annex.
35296 This packet is not probed by default; the remote stub must request it,
35297 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35299 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35300 @anchor{qXfer library list read}
35301 Access the target's list of loaded libraries. @xref{Library List Format}.
35302 The annex part of the generic @samp{qXfer} packet must be empty
35303 (@pxref{qXfer read}).
35305 Targets which maintain a list of libraries in the program's memory do
35306 not need to implement this packet; it is designed for platforms where
35307 the operating system manages the list of loaded libraries.
35309 This packet is not probed by default; the remote stub must request it,
35310 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35312 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35313 @anchor{qXfer svr4 library list read}
35314 Access the target's list of loaded libraries when the target is an SVR4
35315 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35316 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35318 This packet is optional for better performance on SVR4 targets.
35319 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35321 This packet is not probed by default; the remote stub must request it,
35322 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35324 @item qXfer:memory-map:read::@var{offset},@var{length}
35325 @anchor{qXfer memory map read}
35326 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35327 annex part of the generic @samp{qXfer} packet must be empty
35328 (@pxref{qXfer read}).
35330 This packet is not probed by default; the remote stub must request it,
35331 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35333 @item qXfer:sdata:read::@var{offset},@var{length}
35334 @anchor{qXfer sdata read}
35336 Read contents of the extra collected static tracepoint marker
35337 information. The annex part of the generic @samp{qXfer} packet must
35338 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35341 This packet is not probed by default; the remote stub must request it,
35342 by supplying an appropriate @samp{qSupported} response
35343 (@pxref{qSupported}).
35345 @item qXfer:siginfo:read::@var{offset},@var{length}
35346 @anchor{qXfer siginfo read}
35347 Read contents of the extra signal information on the target
35348 system. The annex part of the generic @samp{qXfer} packet must be
35349 empty (@pxref{qXfer read}).
35351 This packet is not probed by default; the remote stub must request it,
35352 by supplying an appropriate @samp{qSupported} response
35353 (@pxref{qSupported}).
35355 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35356 @anchor{qXfer spu read}
35357 Read contents of an @code{spufs} file on the target system. The
35358 annex specifies which file to read; it must be of the form
35359 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35360 in the target process, and @var{name} identifes the @code{spufs} file
35361 in that context to be accessed.
35363 This packet is not probed by default; the remote stub must request it,
35364 by supplying an appropriate @samp{qSupported} response
35365 (@pxref{qSupported}).
35367 @item qXfer:threads:read::@var{offset},@var{length}
35368 @anchor{qXfer threads read}
35369 Access the list of threads on target. @xref{Thread List Format}. The
35370 annex part of the generic @samp{qXfer} packet must be empty
35371 (@pxref{qXfer read}).
35373 This packet is not probed by default; the remote stub must request it,
35374 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35376 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35377 @anchor{qXfer traceframe info read}
35379 Return a description of the current traceframe's contents.
35380 @xref{Traceframe Info Format}. The annex part of the generic
35381 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35383 This packet is not probed by default; the remote stub must request it,
35384 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35386 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35387 @anchor{qXfer fdpic loadmap read}
35388 Read contents of @code{loadmap}s on the target system. The
35389 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35390 executable @code{loadmap} or interpreter @code{loadmap} to read.
35392 This packet is not probed by default; the remote stub must request it,
35393 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35395 @item qXfer:osdata:read::@var{offset},@var{length}
35396 @anchor{qXfer osdata read}
35397 Access the target's @dfn{operating system information}.
35398 @xref{Operating System Information}.
35405 Data @var{data} (@pxref{Binary Data}) has been read from the
35406 target. There may be more data at a higher address (although
35407 it is permitted to return @samp{m} even for the last valid
35408 block of data, as long as at least one byte of data was read).
35409 @var{data} may have fewer bytes than the @var{length} in the
35413 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35414 There is no more data to be read. @var{data} may have fewer bytes
35415 than the @var{length} in the request.
35418 The @var{offset} in the request is at the end of the data.
35419 There is no more data to be read.
35422 The request was malformed, or @var{annex} was invalid.
35425 The offset was invalid, or there was an error encountered reading the data.
35426 @var{nn} is a hex-encoded @code{errno} value.
35429 An empty reply indicates the @var{object} string was not recognized by
35430 the stub, or that the object does not support reading.
35433 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35434 @cindex write data into object, remote request
35435 @anchor{qXfer write}
35436 Write uninterpreted bytes into the target's special data area
35437 identified by the keyword @var{object}, starting at @var{offset} bytes
35438 into the data. @var{data}@dots{} is the binary-encoded data
35439 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35440 is specific to @var{object}; it can supply additional details about what data
35443 Here are the specific requests of this form defined so far. All
35444 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35445 formats, listed below.
35448 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35449 @anchor{qXfer siginfo write}
35450 Write @var{data} to the extra signal information on the target system.
35451 The annex part of the generic @samp{qXfer} packet must be
35452 empty (@pxref{qXfer write}).
35454 This packet is not probed by default; the remote stub must request it,
35455 by supplying an appropriate @samp{qSupported} response
35456 (@pxref{qSupported}).
35458 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35459 @anchor{qXfer spu write}
35460 Write @var{data} to an @code{spufs} file on the target system. The
35461 annex specifies which file to write; it must be of the form
35462 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35463 in the target process, and @var{name} identifes the @code{spufs} file
35464 in that context to be accessed.
35466 This packet is not probed by default; the remote stub must request it,
35467 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35473 @var{nn} (hex encoded) is the number of bytes written.
35474 This may be fewer bytes than supplied in the request.
35477 The request was malformed, or @var{annex} was invalid.
35480 The offset was invalid, or there was an error encountered writing the data.
35481 @var{nn} is a hex-encoded @code{errno} value.
35484 An empty reply indicates the @var{object} string was not
35485 recognized by the stub, or that the object does not support writing.
35488 @item qXfer:@var{object}:@var{operation}:@dots{}
35489 Requests of this form may be added in the future. When a stub does
35490 not recognize the @var{object} keyword, or its support for
35491 @var{object} does not recognize the @var{operation} keyword, the stub
35492 must respond with an empty packet.
35494 @item qAttached:@var{pid}
35495 @cindex query attached, remote request
35496 @cindex @samp{qAttached} packet
35497 Return an indication of whether the remote server attached to an
35498 existing process or created a new process. When the multiprocess
35499 protocol extensions are supported (@pxref{multiprocess extensions}),
35500 @var{pid} is an integer in hexadecimal format identifying the target
35501 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35502 the query packet will be simplified as @samp{qAttached}.
35504 This query is used, for example, to know whether the remote process
35505 should be detached or killed when a @value{GDBN} session is ended with
35506 the @code{quit} command.
35511 The remote server attached to an existing process.
35513 The remote server created a new process.
35515 A badly formed request or an error was encountered.
35520 @node Architecture-Specific Protocol Details
35521 @section Architecture-Specific Protocol Details
35523 This section describes how the remote protocol is applied to specific
35524 target architectures. Also see @ref{Standard Target Features}, for
35525 details of XML target descriptions for each architecture.
35529 @subsubsection Breakpoint Kinds
35531 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35536 16-bit Thumb mode breakpoint.
35539 32-bit Thumb mode (Thumb-2) breakpoint.
35542 32-bit ARM mode breakpoint.
35548 @subsubsection Register Packet Format
35550 The following @code{g}/@code{G} packets have previously been defined.
35551 In the below, some thirty-two bit registers are transferred as
35552 sixty-four bits. Those registers should be zero/sign extended (which?)
35553 to fill the space allocated. Register bytes are transferred in target
35554 byte order. The two nibbles within a register byte are transferred
35555 most-significant - least-significant.
35561 All registers are transferred as thirty-two bit quantities in the order:
35562 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35563 registers; fsr; fir; fp.
35567 All registers are transferred as sixty-four bit quantities (including
35568 thirty-two bit registers such as @code{sr}). The ordering is the same
35573 @node Tracepoint Packets
35574 @section Tracepoint Packets
35575 @cindex tracepoint packets
35576 @cindex packets, tracepoint
35578 Here we describe the packets @value{GDBN} uses to implement
35579 tracepoints (@pxref{Tracepoints}).
35583 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35584 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35585 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35586 the tracepoint is disabled. @var{step} is the tracepoint's step
35587 count, and @var{pass} is its pass count. If an @samp{F} is present,
35588 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35589 the number of bytes that the target should copy elsewhere to make room
35590 for the tracepoint. If an @samp{X} is present, it introduces a
35591 tracepoint condition, which consists of a hexadecimal length, followed
35592 by a comma and hex-encoded bytes, in a manner similar to action
35593 encodings as described below. If the trailing @samp{-} is present,
35594 further @samp{QTDP} packets will follow to specify this tracepoint's
35600 The packet was understood and carried out.
35602 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35604 The packet was not recognized.
35607 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35608 Define actions to be taken when a tracepoint is hit. @var{n} and
35609 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35610 this tracepoint. This packet may only be sent immediately after
35611 another @samp{QTDP} packet that ended with a @samp{-}. If the
35612 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35613 specifying more actions for this tracepoint.
35615 In the series of action packets for a given tracepoint, at most one
35616 can have an @samp{S} before its first @var{action}. If such a packet
35617 is sent, it and the following packets define ``while-stepping''
35618 actions. Any prior packets define ordinary actions --- that is, those
35619 taken when the tracepoint is first hit. If no action packet has an
35620 @samp{S}, then all the packets in the series specify ordinary
35621 tracepoint actions.
35623 The @samp{@var{action}@dots{}} portion of the packet is a series of
35624 actions, concatenated without separators. Each action has one of the
35630 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35631 a hexadecimal number whose @var{i}'th bit is set if register number
35632 @var{i} should be collected. (The least significant bit is numbered
35633 zero.) Note that @var{mask} may be any number of digits long; it may
35634 not fit in a 32-bit word.
35636 @item M @var{basereg},@var{offset},@var{len}
35637 Collect @var{len} bytes of memory starting at the address in register
35638 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35639 @samp{-1}, then the range has a fixed address: @var{offset} is the
35640 address of the lowest byte to collect. The @var{basereg},
35641 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35642 values (the @samp{-1} value for @var{basereg} is a special case).
35644 @item X @var{len},@var{expr}
35645 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35646 it directs. @var{expr} is an agent expression, as described in
35647 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35648 two-digit hex number in the packet; @var{len} is the number of bytes
35649 in the expression (and thus one-half the number of hex digits in the
35654 Any number of actions may be packed together in a single @samp{QTDP}
35655 packet, as long as the packet does not exceed the maximum packet
35656 length (400 bytes, for many stubs). There may be only one @samp{R}
35657 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35658 actions. Any registers referred to by @samp{M} and @samp{X} actions
35659 must be collected by a preceding @samp{R} action. (The
35660 ``while-stepping'' actions are treated as if they were attached to a
35661 separate tracepoint, as far as these restrictions are concerned.)
35666 The packet was understood and carried out.
35668 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35670 The packet was not recognized.
35673 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35674 @cindex @samp{QTDPsrc} packet
35675 Specify a source string of tracepoint @var{n} at address @var{addr}.
35676 This is useful to get accurate reproduction of the tracepoints
35677 originally downloaded at the beginning of the trace run. @var{type}
35678 is the name of the tracepoint part, such as @samp{cond} for the
35679 tracepoint's conditional expression (see below for a list of types), while
35680 @var{bytes} is the string, encoded in hexadecimal.
35682 @var{start} is the offset of the @var{bytes} within the overall source
35683 string, while @var{slen} is the total length of the source string.
35684 This is intended for handling source strings that are longer than will
35685 fit in a single packet.
35686 @c Add detailed example when this info is moved into a dedicated
35687 @c tracepoint descriptions section.
35689 The available string types are @samp{at} for the location,
35690 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35691 @value{GDBN} sends a separate packet for each command in the action
35692 list, in the same order in which the commands are stored in the list.
35694 The target does not need to do anything with source strings except
35695 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35698 Although this packet is optional, and @value{GDBN} will only send it
35699 if the target replies with @samp{TracepointSource} @xref{General
35700 Query Packets}, it makes both disconnected tracing and trace files
35701 much easier to use. Otherwise the user must be careful that the
35702 tracepoints in effect while looking at trace frames are identical to
35703 the ones in effect during the trace run; even a small discrepancy
35704 could cause @samp{tdump} not to work, or a particular trace frame not
35707 @item QTDV:@var{n}:@var{value}
35708 @cindex define trace state variable, remote request
35709 @cindex @samp{QTDV} packet
35710 Create a new trace state variable, number @var{n}, with an initial
35711 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35712 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35713 the option of not using this packet for initial values of zero; the
35714 target should simply create the trace state variables as they are
35715 mentioned in expressions.
35717 @item QTFrame:@var{n}
35718 Select the @var{n}'th tracepoint frame from the buffer, and use the
35719 register and memory contents recorded there to answer subsequent
35720 request packets from @value{GDBN}.
35722 A successful reply from the stub indicates that the stub has found the
35723 requested frame. The response is a series of parts, concatenated
35724 without separators, describing the frame we selected. Each part has
35725 one of the following forms:
35729 The selected frame is number @var{n} in the trace frame buffer;
35730 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35731 was no frame matching the criteria in the request packet.
35734 The selected trace frame records a hit of tracepoint number @var{t};
35735 @var{t} is a hexadecimal number.
35739 @item QTFrame:pc:@var{addr}
35740 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35741 currently selected frame whose PC is @var{addr};
35742 @var{addr} is a hexadecimal number.
35744 @item QTFrame:tdp:@var{t}
35745 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35746 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35747 is a hexadecimal number.
35749 @item QTFrame:range:@var{start}:@var{end}
35750 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35751 currently selected frame whose PC is between @var{start} (inclusive)
35752 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35755 @item QTFrame:outside:@var{start}:@var{end}
35756 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35757 frame @emph{outside} the given range of addresses (exclusive).
35760 This packet requests the minimum length of instruction at which a fast
35761 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35762 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35763 it depends on the target system being able to create trampolines in
35764 the first 64K of memory, which might or might not be possible for that
35765 system. So the reply to this packet will be 4 if it is able to
35772 The minimum instruction length is currently unknown.
35774 The minimum instruction length is @var{length}, where @var{length} is greater
35775 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35776 that a fast tracepoint may be placed on any instruction regardless of size.
35778 An error has occurred.
35780 An empty reply indicates that the request is not supported by the stub.
35784 Begin the tracepoint experiment. Begin collecting data from
35785 tracepoint hits in the trace frame buffer. This packet supports the
35786 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35787 instruction reply packet}).
35790 End the tracepoint experiment. Stop collecting trace frames.
35792 @item QTEnable:@var{n}:@var{addr}
35794 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35795 experiment. If the tracepoint was previously disabled, then collection
35796 of data from it will resume.
35798 @item QTDisable:@var{n}:@var{addr}
35800 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35801 experiment. No more data will be collected from the tracepoint unless
35802 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35805 Clear the table of tracepoints, and empty the trace frame buffer.
35807 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35808 Establish the given ranges of memory as ``transparent''. The stub
35809 will answer requests for these ranges from memory's current contents,
35810 if they were not collected as part of the tracepoint hit.
35812 @value{GDBN} uses this to mark read-only regions of memory, like those
35813 containing program code. Since these areas never change, they should
35814 still have the same contents they did when the tracepoint was hit, so
35815 there's no reason for the stub to refuse to provide their contents.
35817 @item QTDisconnected:@var{value}
35818 Set the choice to what to do with the tracing run when @value{GDBN}
35819 disconnects from the target. A @var{value} of 1 directs the target to
35820 continue the tracing run, while 0 tells the target to stop tracing if
35821 @value{GDBN} is no longer in the picture.
35824 Ask the stub if there is a trace experiment running right now.
35826 The reply has the form:
35830 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35831 @var{running} is a single digit @code{1} if the trace is presently
35832 running, or @code{0} if not. It is followed by semicolon-separated
35833 optional fields that an agent may use to report additional status.
35837 If the trace is not running, the agent may report any of several
35838 explanations as one of the optional fields:
35843 No trace has been run yet.
35845 @item tstop[:@var{text}]:0
35846 The trace was stopped by a user-originated stop command. The optional
35847 @var{text} field is a user-supplied string supplied as part of the
35848 stop command (for instance, an explanation of why the trace was
35849 stopped manually). It is hex-encoded.
35852 The trace stopped because the trace buffer filled up.
35854 @item tdisconnected:0
35855 The trace stopped because @value{GDBN} disconnected from the target.
35857 @item tpasscount:@var{tpnum}
35858 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35860 @item terror:@var{text}:@var{tpnum}
35861 The trace stopped because tracepoint @var{tpnum} had an error. The
35862 string @var{text} is available to describe the nature of the error
35863 (for instance, a divide by zero in the condition expression).
35864 @var{text} is hex encoded.
35867 The trace stopped for some other reason.
35871 Additional optional fields supply statistical and other information.
35872 Although not required, they are extremely useful for users monitoring
35873 the progress of a trace run. If a trace has stopped, and these
35874 numbers are reported, they must reflect the state of the just-stopped
35879 @item tframes:@var{n}
35880 The number of trace frames in the buffer.
35882 @item tcreated:@var{n}
35883 The total number of trace frames created during the run. This may
35884 be larger than the trace frame count, if the buffer is circular.
35886 @item tsize:@var{n}
35887 The total size of the trace buffer, in bytes.
35889 @item tfree:@var{n}
35890 The number of bytes still unused in the buffer.
35892 @item circular:@var{n}
35893 The value of the circular trace buffer flag. @code{1} means that the
35894 trace buffer is circular and old trace frames will be discarded if
35895 necessary to make room, @code{0} means that the trace buffer is linear
35898 @item disconn:@var{n}
35899 The value of the disconnected tracing flag. @code{1} means that
35900 tracing will continue after @value{GDBN} disconnects, @code{0} means
35901 that the trace run will stop.
35905 @item qTP:@var{tp}:@var{addr}
35906 @cindex tracepoint status, remote request
35907 @cindex @samp{qTP} packet
35908 Ask the stub for the current state of tracepoint number @var{tp} at
35909 address @var{addr}.
35913 @item V@var{hits}:@var{usage}
35914 The tracepoint has been hit @var{hits} times so far during the trace
35915 run, and accounts for @var{usage} in the trace buffer. Note that
35916 @code{while-stepping} steps are not counted as separate hits, but the
35917 steps' space consumption is added into the usage number.
35921 @item qTV:@var{var}
35922 @cindex trace state variable value, remote request
35923 @cindex @samp{qTV} packet
35924 Ask the stub for the value of the trace state variable number @var{var}.
35929 The value of the variable is @var{value}. This will be the current
35930 value of the variable if the user is examining a running target, or a
35931 saved value if the variable was collected in the trace frame that the
35932 user is looking at. Note that multiple requests may result in
35933 different reply values, such as when requesting values while the
35934 program is running.
35937 The value of the variable is unknown. This would occur, for example,
35938 if the user is examining a trace frame in which the requested variable
35944 These packets request data about tracepoints that are being used by
35945 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35946 of data, and multiple @code{qTsP} to get additional pieces. Replies
35947 to these packets generally take the form of the @code{QTDP} packets
35948 that define tracepoints. (FIXME add detailed syntax)
35952 These packets request data about trace state variables that are on the
35953 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35954 and multiple @code{qTsV} to get additional variables. Replies to
35955 these packets follow the syntax of the @code{QTDV} packets that define
35956 trace state variables.
35960 These packets request data about static tracepoint markers that exist
35961 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35962 first piece of data, and multiple @code{qTsSTM} to get additional
35963 pieces. Replies to these packets take the following form:
35967 @item m @var{address}:@var{id}:@var{extra}
35969 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35970 a comma-separated list of markers
35972 (lower case letter @samp{L}) denotes end of list.
35974 An error occurred. @var{nn} are hex digits.
35976 An empty reply indicates that the request is not supported by the
35980 @var{address} is encoded in hex.
35981 @var{id} and @var{extra} are strings encoded in hex.
35983 In response to each query, the target will reply with a list of one or
35984 more markers, separated by commas. @value{GDBN} will respond to each
35985 reply with a request for more markers (using the @samp{qs} form of the
35986 query), until the target responds with @samp{l} (lower-case ell, for
35989 @item qTSTMat:@var{address}
35990 This packets requests data about static tracepoint markers in the
35991 target program at @var{address}. Replies to this packet follow the
35992 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35993 tracepoint markers.
35995 @item QTSave:@var{filename}
35996 This packet directs the target to save trace data to the file name
35997 @var{filename} in the target's filesystem. @var{filename} is encoded
35998 as a hex string; the interpretation of the file name (relative vs
35999 absolute, wild cards, etc) is up to the target.
36001 @item qTBuffer:@var{offset},@var{len}
36002 Return up to @var{len} bytes of the current contents of trace buffer,
36003 starting at @var{offset}. The trace buffer is treated as if it were
36004 a contiguous collection of traceframes, as per the trace file format.
36005 The reply consists as many hex-encoded bytes as the target can deliver
36006 in a packet; it is not an error to return fewer than were asked for.
36007 A reply consisting of just @code{l} indicates that no bytes are
36010 @item QTBuffer:circular:@var{value}
36011 This packet directs the target to use a circular trace buffer if
36012 @var{value} is 1, or a linear buffer if the value is 0.
36014 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36015 This packet adds optional textual notes to the trace run. Allowable
36016 types include @code{user}, @code{notes}, and @code{tstop}, the
36017 @var{text} fields are arbitrary strings, hex-encoded.
36021 @subsection Relocate instruction reply packet
36022 When installing fast tracepoints in memory, the target may need to
36023 relocate the instruction currently at the tracepoint address to a
36024 different address in memory. For most instructions, a simple copy is
36025 enough, but, for example, call instructions that implicitly push the
36026 return address on the stack, and relative branches or other
36027 PC-relative instructions require offset adjustment, so that the effect
36028 of executing the instruction at a different address is the same as if
36029 it had executed in the original location.
36031 In response to several of the tracepoint packets, the target may also
36032 respond with a number of intermediate @samp{qRelocInsn} request
36033 packets before the final result packet, to have @value{GDBN} handle
36034 this relocation operation. If a packet supports this mechanism, its
36035 documentation will explicitly say so. See for example the above
36036 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36037 format of the request is:
36040 @item qRelocInsn:@var{from};@var{to}
36042 This requests @value{GDBN} to copy instruction at address @var{from}
36043 to address @var{to}, possibly adjusted so that executing the
36044 instruction at @var{to} has the same effect as executing it at
36045 @var{from}. @value{GDBN} writes the adjusted instruction to target
36046 memory starting at @var{to}.
36051 @item qRelocInsn:@var{adjusted_size}
36052 Informs the stub the relocation is complete. @var{adjusted_size} is
36053 the length in bytes of resulting relocated instruction sequence.
36055 A badly formed request was detected, or an error was encountered while
36056 relocating the instruction.
36059 @node Host I/O Packets
36060 @section Host I/O Packets
36061 @cindex Host I/O, remote protocol
36062 @cindex file transfer, remote protocol
36064 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36065 operations on the far side of a remote link. For example, Host I/O is
36066 used to upload and download files to a remote target with its own
36067 filesystem. Host I/O uses the same constant values and data structure
36068 layout as the target-initiated File-I/O protocol. However, the
36069 Host I/O packets are structured differently. The target-initiated
36070 protocol relies on target memory to store parameters and buffers.
36071 Host I/O requests are initiated by @value{GDBN}, and the
36072 target's memory is not involved. @xref{File-I/O Remote Protocol
36073 Extension}, for more details on the target-initiated protocol.
36075 The Host I/O request packets all encode a single operation along with
36076 its arguments. They have this format:
36080 @item vFile:@var{operation}: @var{parameter}@dots{}
36081 @var{operation} is the name of the particular request; the target
36082 should compare the entire packet name up to the second colon when checking
36083 for a supported operation. The format of @var{parameter} depends on
36084 the operation. Numbers are always passed in hexadecimal. Negative
36085 numbers have an explicit minus sign (i.e.@: two's complement is not
36086 used). Strings (e.g.@: filenames) are encoded as a series of
36087 hexadecimal bytes. The last argument to a system call may be a
36088 buffer of escaped binary data (@pxref{Binary Data}).
36092 The valid responses to Host I/O packets are:
36096 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36097 @var{result} is the integer value returned by this operation, usually
36098 non-negative for success and -1 for errors. If an error has occured,
36099 @var{errno} will be included in the result. @var{errno} will have a
36100 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36101 operations which return data, @var{attachment} supplies the data as a
36102 binary buffer. Binary buffers in response packets are escaped in the
36103 normal way (@pxref{Binary Data}). See the individual packet
36104 documentation for the interpretation of @var{result} and
36108 An empty response indicates that this operation is not recognized.
36112 These are the supported Host I/O operations:
36115 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36116 Open a file at @var{pathname} and return a file descriptor for it, or
36117 return -1 if an error occurs. @var{pathname} is a string,
36118 @var{flags} is an integer indicating a mask of open flags
36119 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36120 of mode bits to use if the file is created (@pxref{mode_t Values}).
36121 @xref{open}, for details of the open flags and mode values.
36123 @item vFile:close: @var{fd}
36124 Close the open file corresponding to @var{fd} and return 0, or
36125 -1 if an error occurs.
36127 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36128 Read data from the open file corresponding to @var{fd}. Up to
36129 @var{count} bytes will be read from the file, starting at @var{offset}
36130 relative to the start of the file. The target may read fewer bytes;
36131 common reasons include packet size limits and an end-of-file
36132 condition. The number of bytes read is returned. Zero should only be
36133 returned for a successful read at the end of the file, or if
36134 @var{count} was zero.
36136 The data read should be returned as a binary attachment on success.
36137 If zero bytes were read, the response should include an empty binary
36138 attachment (i.e.@: a trailing semicolon). The return value is the
36139 number of target bytes read; the binary attachment may be longer if
36140 some characters were escaped.
36142 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36143 Write @var{data} (a binary buffer) to the open file corresponding
36144 to @var{fd}. Start the write at @var{offset} from the start of the
36145 file. Unlike many @code{write} system calls, there is no
36146 separate @var{count} argument; the length of @var{data} in the
36147 packet is used. @samp{vFile:write} returns the number of bytes written,
36148 which may be shorter than the length of @var{data}, or -1 if an
36151 @item vFile:unlink: @var{pathname}
36152 Delete the file at @var{pathname} on the target. Return 0,
36153 or -1 if an error occurs. @var{pathname} is a string.
36158 @section Interrupts
36159 @cindex interrupts (remote protocol)
36161 When a program on the remote target is running, @value{GDBN} may
36162 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36163 a @code{BREAK} followed by @code{g},
36164 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36166 The precise meaning of @code{BREAK} is defined by the transport
36167 mechanism and may, in fact, be undefined. @value{GDBN} does not
36168 currently define a @code{BREAK} mechanism for any of the network
36169 interfaces except for TCP, in which case @value{GDBN} sends the
36170 @code{telnet} BREAK sequence.
36172 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36173 transport mechanisms. It is represented by sending the single byte
36174 @code{0x03} without any of the usual packet overhead described in
36175 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36176 transmitted as part of a packet, it is considered to be packet data
36177 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36178 (@pxref{X packet}), used for binary downloads, may include an unescaped
36179 @code{0x03} as part of its packet.
36181 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36182 When Linux kernel receives this sequence from serial port,
36183 it stops execution and connects to gdb.
36185 Stubs are not required to recognize these interrupt mechanisms and the
36186 precise meaning associated with receipt of the interrupt is
36187 implementation defined. If the target supports debugging of multiple
36188 threads and/or processes, it should attempt to interrupt all
36189 currently-executing threads and processes.
36190 If the stub is successful at interrupting the
36191 running program, it should send one of the stop
36192 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36193 of successfully stopping the program in all-stop mode, and a stop reply
36194 for each stopped thread in non-stop mode.
36195 Interrupts received while the
36196 program is stopped are discarded.
36198 @node Notification Packets
36199 @section Notification Packets
36200 @cindex notification packets
36201 @cindex packets, notification
36203 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36204 packets that require no acknowledgment. Both the GDB and the stub
36205 may send notifications (although the only notifications defined at
36206 present are sent by the stub). Notifications carry information
36207 without incurring the round-trip latency of an acknowledgment, and so
36208 are useful for low-impact communications where occasional packet loss
36211 A notification packet has the form @samp{% @var{data} #
36212 @var{checksum}}, where @var{data} is the content of the notification,
36213 and @var{checksum} is a checksum of @var{data}, computed and formatted
36214 as for ordinary @value{GDBN} packets. A notification's @var{data}
36215 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36216 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36217 to acknowledge the notification's receipt or to report its corruption.
36219 Every notification's @var{data} begins with a name, which contains no
36220 colon characters, followed by a colon character.
36222 Recipients should silently ignore corrupted notifications and
36223 notifications they do not understand. Recipients should restart
36224 timeout periods on receipt of a well-formed notification, whether or
36225 not they understand it.
36227 Senders should only send the notifications described here when this
36228 protocol description specifies that they are permitted. In the
36229 future, we may extend the protocol to permit existing notifications in
36230 new contexts; this rule helps older senders avoid confusing newer
36233 (Older versions of @value{GDBN} ignore bytes received until they see
36234 the @samp{$} byte that begins an ordinary packet, so new stubs may
36235 transmit notifications without fear of confusing older clients. There
36236 are no notifications defined for @value{GDBN} to send at the moment, but we
36237 assume that most older stubs would ignore them, as well.)
36239 The following notification packets from the stub to @value{GDBN} are
36243 @item Stop: @var{reply}
36244 Report an asynchronous stop event in non-stop mode.
36245 The @var{reply} has the form of a stop reply, as
36246 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36247 for information on how these notifications are acknowledged by
36251 @node Remote Non-Stop
36252 @section Remote Protocol Support for Non-Stop Mode
36254 @value{GDBN}'s remote protocol supports non-stop debugging of
36255 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36256 supports non-stop mode, it should report that to @value{GDBN} by including
36257 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36259 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36260 establishing a new connection with the stub. Entering non-stop mode
36261 does not alter the state of any currently-running threads, but targets
36262 must stop all threads in any already-attached processes when entering
36263 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36264 probe the target state after a mode change.
36266 In non-stop mode, when an attached process encounters an event that
36267 would otherwise be reported with a stop reply, it uses the
36268 asynchronous notification mechanism (@pxref{Notification Packets}) to
36269 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36270 in all processes are stopped when a stop reply is sent, in non-stop
36271 mode only the thread reporting the stop event is stopped. That is,
36272 when reporting a @samp{S} or @samp{T} response to indicate completion
36273 of a step operation, hitting a breakpoint, or a fault, only the
36274 affected thread is stopped; any other still-running threads continue
36275 to run. When reporting a @samp{W} or @samp{X} response, all running
36276 threads belonging to other attached processes continue to run.
36278 Only one stop reply notification at a time may be pending; if
36279 additional stop events occur before @value{GDBN} has acknowledged the
36280 previous notification, they must be queued by the stub for later
36281 synchronous transmission in response to @samp{vStopped} packets from
36282 @value{GDBN}. Because the notification mechanism is unreliable,
36283 the stub is permitted to resend a stop reply notification
36284 if it believes @value{GDBN} may not have received it. @value{GDBN}
36285 ignores additional stop reply notifications received before it has
36286 finished processing a previous notification and the stub has completed
36287 sending any queued stop events.
36289 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36290 notification at any time. Specifically, they may appear when
36291 @value{GDBN} is not otherwise reading input from the stub, or when
36292 @value{GDBN} is expecting to read a normal synchronous response or a
36293 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36294 Notification packets are distinct from any other communication from
36295 the stub so there is no ambiguity.
36297 After receiving a stop reply notification, @value{GDBN} shall
36298 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36299 as a regular, synchronous request to the stub. Such acknowledgment
36300 is not required to happen immediately, as @value{GDBN} is permitted to
36301 send other, unrelated packets to the stub first, which the stub should
36304 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36305 stop events to report to @value{GDBN}, it shall respond by sending a
36306 normal stop reply response. @value{GDBN} shall then send another
36307 @samp{vStopped} packet to solicit further responses; again, it is
36308 permitted to send other, unrelated packets as well which the stub
36309 should process normally.
36311 If the stub receives a @samp{vStopped} packet and there are no
36312 additional stop events to report, the stub shall return an @samp{OK}
36313 response. At this point, if further stop events occur, the stub shall
36314 send a new stop reply notification, @value{GDBN} shall accept the
36315 notification, and the process shall be repeated.
36317 In non-stop mode, the target shall respond to the @samp{?} packet as
36318 follows. First, any incomplete stop reply notification/@samp{vStopped}
36319 sequence in progress is abandoned. The target must begin a new
36320 sequence reporting stop events for all stopped threads, whether or not
36321 it has previously reported those events to @value{GDBN}. The first
36322 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36323 subsequent stop replies are sent as responses to @samp{vStopped} packets
36324 using the mechanism described above. The target must not send
36325 asynchronous stop reply notifications until the sequence is complete.
36326 If all threads are running when the target receives the @samp{?} packet,
36327 or if the target is not attached to any process, it shall respond
36330 @node Packet Acknowledgment
36331 @section Packet Acknowledgment
36333 @cindex acknowledgment, for @value{GDBN} remote
36334 @cindex packet acknowledgment, for @value{GDBN} remote
36335 By default, when either the host or the target machine receives a packet,
36336 the first response expected is an acknowledgment: either @samp{+} (to indicate
36337 the package was received correctly) or @samp{-} (to request retransmission).
36338 This mechanism allows the @value{GDBN} remote protocol to operate over
36339 unreliable transport mechanisms, such as a serial line.
36341 In cases where the transport mechanism is itself reliable (such as a pipe or
36342 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36343 It may be desirable to disable them in that case to reduce communication
36344 overhead, or for other reasons. This can be accomplished by means of the
36345 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36347 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36348 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36349 and response format still includes the normal checksum, as described in
36350 @ref{Overview}, but the checksum may be ignored by the receiver.
36352 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36353 no-acknowledgment mode, it should report that to @value{GDBN}
36354 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36355 @pxref{qSupported}.
36356 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36357 disabled via the @code{set remote noack-packet off} command
36358 (@pxref{Remote Configuration}),
36359 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36360 Only then may the stub actually turn off packet acknowledgments.
36361 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36362 response, which can be safely ignored by the stub.
36364 Note that @code{set remote noack-packet} command only affects negotiation
36365 between @value{GDBN} and the stub when subsequent connections are made;
36366 it does not affect the protocol acknowledgment state for any current
36368 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36369 new connection is established,
36370 there is also no protocol request to re-enable the acknowledgments
36371 for the current connection, once disabled.
36376 Example sequence of a target being re-started. Notice how the restart
36377 does not get any direct output:
36382 @emph{target restarts}
36385 <- @code{T001:1234123412341234}
36389 Example sequence of a target being stepped by a single instruction:
36392 -> @code{G1445@dots{}}
36397 <- @code{T001:1234123412341234}
36401 <- @code{1455@dots{}}
36405 @node File-I/O Remote Protocol Extension
36406 @section File-I/O Remote Protocol Extension
36407 @cindex File-I/O remote protocol extension
36410 * File-I/O Overview::
36411 * Protocol Basics::
36412 * The F Request Packet::
36413 * The F Reply Packet::
36414 * The Ctrl-C Message::
36416 * List of Supported Calls::
36417 * Protocol-specific Representation of Datatypes::
36419 * File-I/O Examples::
36422 @node File-I/O Overview
36423 @subsection File-I/O Overview
36424 @cindex file-i/o overview
36426 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36427 target to use the host's file system and console I/O to perform various
36428 system calls. System calls on the target system are translated into a
36429 remote protocol packet to the host system, which then performs the needed
36430 actions and returns a response packet to the target system.
36431 This simulates file system operations even on targets that lack file systems.
36433 The protocol is defined to be independent of both the host and target systems.
36434 It uses its own internal representation of datatypes and values. Both
36435 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36436 translating the system-dependent value representations into the internal
36437 protocol representations when data is transmitted.
36439 The communication is synchronous. A system call is possible only when
36440 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36441 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36442 the target is stopped to allow deterministic access to the target's
36443 memory. Therefore File-I/O is not interruptible by target signals. On
36444 the other hand, it is possible to interrupt File-I/O by a user interrupt
36445 (@samp{Ctrl-C}) within @value{GDBN}.
36447 The target's request to perform a host system call does not finish
36448 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36449 after finishing the system call, the target returns to continuing the
36450 previous activity (continue, step). No additional continue or step
36451 request from @value{GDBN} is required.
36454 (@value{GDBP}) continue
36455 <- target requests 'system call X'
36456 target is stopped, @value{GDBN} executes system call
36457 -> @value{GDBN} returns result
36458 ... target continues, @value{GDBN} returns to wait for the target
36459 <- target hits breakpoint and sends a Txx packet
36462 The protocol only supports I/O on the console and to regular files on
36463 the host file system. Character or block special devices, pipes,
36464 named pipes, sockets or any other communication method on the host
36465 system are not supported by this protocol.
36467 File I/O is not supported in non-stop mode.
36469 @node Protocol Basics
36470 @subsection Protocol Basics
36471 @cindex protocol basics, file-i/o
36473 The File-I/O protocol uses the @code{F} packet as the request as well
36474 as reply packet. Since a File-I/O system call can only occur when
36475 @value{GDBN} is waiting for a response from the continuing or stepping target,
36476 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36477 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36478 This @code{F} packet contains all information needed to allow @value{GDBN}
36479 to call the appropriate host system call:
36483 A unique identifier for the requested system call.
36486 All parameters to the system call. Pointers are given as addresses
36487 in the target memory address space. Pointers to strings are given as
36488 pointer/length pair. Numerical values are given as they are.
36489 Numerical control flags are given in a protocol-specific representation.
36493 At this point, @value{GDBN} has to perform the following actions.
36497 If the parameters include pointer values to data needed as input to a
36498 system call, @value{GDBN} requests this data from the target with a
36499 standard @code{m} packet request. This additional communication has to be
36500 expected by the target implementation and is handled as any other @code{m}
36504 @value{GDBN} translates all value from protocol representation to host
36505 representation as needed. Datatypes are coerced into the host types.
36508 @value{GDBN} calls the system call.
36511 It then coerces datatypes back to protocol representation.
36514 If the system call is expected to return data in buffer space specified
36515 by pointer parameters to the call, the data is transmitted to the
36516 target using a @code{M} or @code{X} packet. This packet has to be expected
36517 by the target implementation and is handled as any other @code{M} or @code{X}
36522 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36523 necessary information for the target to continue. This at least contains
36530 @code{errno}, if has been changed by the system call.
36537 After having done the needed type and value coercion, the target continues
36538 the latest continue or step action.
36540 @node The F Request Packet
36541 @subsection The @code{F} Request Packet
36542 @cindex file-i/o request packet
36543 @cindex @code{F} request packet
36545 The @code{F} request packet has the following format:
36548 @item F@var{call-id},@var{parameter@dots{}}
36550 @var{call-id} is the identifier to indicate the host system call to be called.
36551 This is just the name of the function.
36553 @var{parameter@dots{}} are the parameters to the system call.
36554 Parameters are hexadecimal integer values, either the actual values in case
36555 of scalar datatypes, pointers to target buffer space in case of compound
36556 datatypes and unspecified memory areas, or pointer/length pairs in case
36557 of string parameters. These are appended to the @var{call-id} as a
36558 comma-delimited list. All values are transmitted in ASCII
36559 string representation, pointer/length pairs separated by a slash.
36565 @node The F Reply Packet
36566 @subsection The @code{F} Reply Packet
36567 @cindex file-i/o reply packet
36568 @cindex @code{F} reply packet
36570 The @code{F} reply packet has the following format:
36574 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36576 @var{retcode} is the return code of the system call as hexadecimal value.
36578 @var{errno} is the @code{errno} set by the call, in protocol-specific
36580 This parameter can be omitted if the call was successful.
36582 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36583 case, @var{errno} must be sent as well, even if the call was successful.
36584 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36591 or, if the call was interrupted before the host call has been performed:
36598 assuming 4 is the protocol-specific representation of @code{EINTR}.
36603 @node The Ctrl-C Message
36604 @subsection The @samp{Ctrl-C} Message
36605 @cindex ctrl-c message, in file-i/o protocol
36607 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36608 reply packet (@pxref{The F Reply Packet}),
36609 the target should behave as if it had
36610 gotten a break message. The meaning for the target is ``system call
36611 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36612 (as with a break message) and return to @value{GDBN} with a @code{T02}
36615 It's important for the target to know in which
36616 state the system call was interrupted. There are two possible cases:
36620 The system call hasn't been performed on the host yet.
36623 The system call on the host has been finished.
36627 These two states can be distinguished by the target by the value of the
36628 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36629 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36630 on POSIX systems. In any other case, the target may presume that the
36631 system call has been finished --- successfully or not --- and should behave
36632 as if the break message arrived right after the system call.
36634 @value{GDBN} must behave reliably. If the system call has not been called
36635 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36636 @code{errno} in the packet. If the system call on the host has been finished
36637 before the user requests a break, the full action must be finished by
36638 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36639 The @code{F} packet may only be sent when either nothing has happened
36640 or the full action has been completed.
36643 @subsection Console I/O
36644 @cindex console i/o as part of file-i/o
36646 By default and if not explicitly closed by the target system, the file
36647 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36648 on the @value{GDBN} console is handled as any other file output operation
36649 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36650 by @value{GDBN} so that after the target read request from file descriptor
36651 0 all following typing is buffered until either one of the following
36656 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36658 system call is treated as finished.
36661 The user presses @key{RET}. This is treated as end of input with a trailing
36665 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36666 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36670 If the user has typed more characters than fit in the buffer given to
36671 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36672 either another @code{read(0, @dots{})} is requested by the target, or debugging
36673 is stopped at the user's request.
36676 @node List of Supported Calls
36677 @subsection List of Supported Calls
36678 @cindex list of supported file-i/o calls
36695 @unnumberedsubsubsec open
36696 @cindex open, file-i/o system call
36701 int open(const char *pathname, int flags);
36702 int open(const char *pathname, int flags, mode_t mode);
36706 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36709 @var{flags} is the bitwise @code{OR} of the following values:
36713 If the file does not exist it will be created. The host
36714 rules apply as far as file ownership and time stamps
36718 When used with @code{O_CREAT}, if the file already exists it is
36719 an error and open() fails.
36722 If the file already exists and the open mode allows
36723 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36724 truncated to zero length.
36727 The file is opened in append mode.
36730 The file is opened for reading only.
36733 The file is opened for writing only.
36736 The file is opened for reading and writing.
36740 Other bits are silently ignored.
36744 @var{mode} is the bitwise @code{OR} of the following values:
36748 User has read permission.
36751 User has write permission.
36754 Group has read permission.
36757 Group has write permission.
36760 Others have read permission.
36763 Others have write permission.
36767 Other bits are silently ignored.
36770 @item Return value:
36771 @code{open} returns the new file descriptor or -1 if an error
36778 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36781 @var{pathname} refers to a directory.
36784 The requested access is not allowed.
36787 @var{pathname} was too long.
36790 A directory component in @var{pathname} does not exist.
36793 @var{pathname} refers to a device, pipe, named pipe or socket.
36796 @var{pathname} refers to a file on a read-only filesystem and
36797 write access was requested.
36800 @var{pathname} is an invalid pointer value.
36803 No space on device to create the file.
36806 The process already has the maximum number of files open.
36809 The limit on the total number of files open on the system
36813 The call was interrupted by the user.
36819 @unnumberedsubsubsec close
36820 @cindex close, file-i/o system call
36829 @samp{Fclose,@var{fd}}
36831 @item Return value:
36832 @code{close} returns zero on success, or -1 if an error occurred.
36838 @var{fd} isn't a valid open file descriptor.
36841 The call was interrupted by the user.
36847 @unnumberedsubsubsec read
36848 @cindex read, file-i/o system call
36853 int read(int fd, void *buf, unsigned int count);
36857 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36859 @item Return value:
36860 On success, the number of bytes read is returned.
36861 Zero indicates end of file. If count is zero, read
36862 returns zero as well. On error, -1 is returned.
36868 @var{fd} is not a valid file descriptor or is not open for
36872 @var{bufptr} is an invalid pointer value.
36875 The call was interrupted by the user.
36881 @unnumberedsubsubsec write
36882 @cindex write, file-i/o system call
36887 int write(int fd, const void *buf, unsigned int count);
36891 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36893 @item Return value:
36894 On success, the number of bytes written are returned.
36895 Zero indicates nothing was written. On error, -1
36902 @var{fd} is not a valid file descriptor or is not open for
36906 @var{bufptr} is an invalid pointer value.
36909 An attempt was made to write a file that exceeds the
36910 host-specific maximum file size allowed.
36913 No space on device to write the data.
36916 The call was interrupted by the user.
36922 @unnumberedsubsubsec lseek
36923 @cindex lseek, file-i/o system call
36928 long lseek (int fd, long offset, int flag);
36932 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36934 @var{flag} is one of:
36938 The offset is set to @var{offset} bytes.
36941 The offset is set to its current location plus @var{offset}
36945 The offset is set to the size of the file plus @var{offset}
36949 @item Return value:
36950 On success, the resulting unsigned offset in bytes from
36951 the beginning of the file is returned. Otherwise, a
36952 value of -1 is returned.
36958 @var{fd} is not a valid open file descriptor.
36961 @var{fd} is associated with the @value{GDBN} console.
36964 @var{flag} is not a proper value.
36967 The call was interrupted by the user.
36973 @unnumberedsubsubsec rename
36974 @cindex rename, file-i/o system call
36979 int rename(const char *oldpath, const char *newpath);
36983 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36985 @item Return value:
36986 On success, zero is returned. On error, -1 is returned.
36992 @var{newpath} is an existing directory, but @var{oldpath} is not a
36996 @var{newpath} is a non-empty directory.
36999 @var{oldpath} or @var{newpath} is a directory that is in use by some
37003 An attempt was made to make a directory a subdirectory
37007 A component used as a directory in @var{oldpath} or new
37008 path is not a directory. Or @var{oldpath} is a directory
37009 and @var{newpath} exists but is not a directory.
37012 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37015 No access to the file or the path of the file.
37019 @var{oldpath} or @var{newpath} was too long.
37022 A directory component in @var{oldpath} or @var{newpath} does not exist.
37025 The file is on a read-only filesystem.
37028 The device containing the file has no room for the new
37032 The call was interrupted by the user.
37038 @unnumberedsubsubsec unlink
37039 @cindex unlink, file-i/o system call
37044 int unlink(const char *pathname);
37048 @samp{Funlink,@var{pathnameptr}/@var{len}}
37050 @item Return value:
37051 On success, zero is returned. On error, -1 is returned.
37057 No access to the file or the path of the file.
37060 The system does not allow unlinking of directories.
37063 The file @var{pathname} cannot be unlinked because it's
37064 being used by another process.
37067 @var{pathnameptr} is an invalid pointer value.
37070 @var{pathname} was too long.
37073 A directory component in @var{pathname} does not exist.
37076 A component of the path is not a directory.
37079 The file is on a read-only filesystem.
37082 The call was interrupted by the user.
37088 @unnumberedsubsubsec stat/fstat
37089 @cindex fstat, file-i/o system call
37090 @cindex stat, file-i/o system call
37095 int stat(const char *pathname, struct stat *buf);
37096 int fstat(int fd, struct stat *buf);
37100 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37101 @samp{Ffstat,@var{fd},@var{bufptr}}
37103 @item Return value:
37104 On success, zero is returned. On error, -1 is returned.
37110 @var{fd} is not a valid open file.
37113 A directory component in @var{pathname} does not exist or the
37114 path is an empty string.
37117 A component of the path is not a directory.
37120 @var{pathnameptr} is an invalid pointer value.
37123 No access to the file or the path of the file.
37126 @var{pathname} was too long.
37129 The call was interrupted by the user.
37135 @unnumberedsubsubsec gettimeofday
37136 @cindex gettimeofday, file-i/o system call
37141 int gettimeofday(struct timeval *tv, void *tz);
37145 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37147 @item Return value:
37148 On success, 0 is returned, -1 otherwise.
37154 @var{tz} is a non-NULL pointer.
37157 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37163 @unnumberedsubsubsec isatty
37164 @cindex isatty, file-i/o system call
37169 int isatty(int fd);
37173 @samp{Fisatty,@var{fd}}
37175 @item Return value:
37176 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37182 The call was interrupted by the user.
37187 Note that the @code{isatty} call is treated as a special case: it returns
37188 1 to the target if the file descriptor is attached
37189 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37190 would require implementing @code{ioctl} and would be more complex than
37195 @unnumberedsubsubsec system
37196 @cindex system, file-i/o system call
37201 int system(const char *command);
37205 @samp{Fsystem,@var{commandptr}/@var{len}}
37207 @item Return value:
37208 If @var{len} is zero, the return value indicates whether a shell is
37209 available. A zero return value indicates a shell is not available.
37210 For non-zero @var{len}, the value returned is -1 on error and the
37211 return status of the command otherwise. Only the exit status of the
37212 command is returned, which is extracted from the host's @code{system}
37213 return value by calling @code{WEXITSTATUS(retval)}. In case
37214 @file{/bin/sh} could not be executed, 127 is returned.
37220 The call was interrupted by the user.
37225 @value{GDBN} takes over the full task of calling the necessary host calls
37226 to perform the @code{system} call. The return value of @code{system} on
37227 the host is simplified before it's returned
37228 to the target. Any termination signal information from the child process
37229 is discarded, and the return value consists
37230 entirely of the exit status of the called command.
37232 Due to security concerns, the @code{system} call is by default refused
37233 by @value{GDBN}. The user has to allow this call explicitly with the
37234 @code{set remote system-call-allowed 1} command.
37237 @item set remote system-call-allowed
37238 @kindex set remote system-call-allowed
37239 Control whether to allow the @code{system} calls in the File I/O
37240 protocol for the remote target. The default is zero (disabled).
37242 @item show remote system-call-allowed
37243 @kindex show remote system-call-allowed
37244 Show whether the @code{system} calls are allowed in the File I/O
37248 @node Protocol-specific Representation of Datatypes
37249 @subsection Protocol-specific Representation of Datatypes
37250 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37253 * Integral Datatypes::
37255 * Memory Transfer::
37260 @node Integral Datatypes
37261 @unnumberedsubsubsec Integral Datatypes
37262 @cindex integral datatypes, in file-i/o protocol
37264 The integral datatypes used in the system calls are @code{int},
37265 @code{unsigned int}, @code{long}, @code{unsigned long},
37266 @code{mode_t}, and @code{time_t}.
37268 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37269 implemented as 32 bit values in this protocol.
37271 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37273 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37274 in @file{limits.h}) to allow range checking on host and target.
37276 @code{time_t} datatypes are defined as seconds since the Epoch.
37278 All integral datatypes transferred as part of a memory read or write of a
37279 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37282 @node Pointer Values
37283 @unnumberedsubsubsec Pointer Values
37284 @cindex pointer values, in file-i/o protocol
37286 Pointers to target data are transmitted as they are. An exception
37287 is made for pointers to buffers for which the length isn't
37288 transmitted as part of the function call, namely strings. Strings
37289 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37296 which is a pointer to data of length 18 bytes at position 0x1aaf.
37297 The length is defined as the full string length in bytes, including
37298 the trailing null byte. For example, the string @code{"hello world"}
37299 at address 0x123456 is transmitted as
37305 @node Memory Transfer
37306 @unnumberedsubsubsec Memory Transfer
37307 @cindex memory transfer, in file-i/o protocol
37309 Structured data which is transferred using a memory read or write (for
37310 example, a @code{struct stat}) is expected to be in a protocol-specific format
37311 with all scalar multibyte datatypes being big endian. Translation to
37312 this representation needs to be done both by the target before the @code{F}
37313 packet is sent, and by @value{GDBN} before
37314 it transfers memory to the target. Transferred pointers to structured
37315 data should point to the already-coerced data at any time.
37319 @unnumberedsubsubsec struct stat
37320 @cindex struct stat, in file-i/o protocol
37322 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37323 is defined as follows:
37327 unsigned int st_dev; /* device */
37328 unsigned int st_ino; /* inode */
37329 mode_t st_mode; /* protection */
37330 unsigned int st_nlink; /* number of hard links */
37331 unsigned int st_uid; /* user ID of owner */
37332 unsigned int st_gid; /* group ID of owner */
37333 unsigned int st_rdev; /* device type (if inode device) */
37334 unsigned long st_size; /* total size, in bytes */
37335 unsigned long st_blksize; /* blocksize for filesystem I/O */
37336 unsigned long st_blocks; /* number of blocks allocated */
37337 time_t st_atime; /* time of last access */
37338 time_t st_mtime; /* time of last modification */
37339 time_t st_ctime; /* time of last change */
37343 The integral datatypes conform to the definitions given in the
37344 appropriate section (see @ref{Integral Datatypes}, for details) so this
37345 structure is of size 64 bytes.
37347 The values of several fields have a restricted meaning and/or
37353 A value of 0 represents a file, 1 the console.
37356 No valid meaning for the target. Transmitted unchanged.
37359 Valid mode bits are described in @ref{Constants}. Any other
37360 bits have currently no meaning for the target.
37365 No valid meaning for the target. Transmitted unchanged.
37370 These values have a host and file system dependent
37371 accuracy. Especially on Windows hosts, the file system may not
37372 support exact timing values.
37375 The target gets a @code{struct stat} of the above representation and is
37376 responsible for coercing it to the target representation before
37379 Note that due to size differences between the host, target, and protocol
37380 representations of @code{struct stat} members, these members could eventually
37381 get truncated on the target.
37383 @node struct timeval
37384 @unnumberedsubsubsec struct timeval
37385 @cindex struct timeval, in file-i/o protocol
37387 The buffer of type @code{struct timeval} used by the File-I/O protocol
37388 is defined as follows:
37392 time_t tv_sec; /* second */
37393 long tv_usec; /* microsecond */
37397 The integral datatypes conform to the definitions given in the
37398 appropriate section (see @ref{Integral Datatypes}, for details) so this
37399 structure is of size 8 bytes.
37402 @subsection Constants
37403 @cindex constants, in file-i/o protocol
37405 The following values are used for the constants inside of the
37406 protocol. @value{GDBN} and target are responsible for translating these
37407 values before and after the call as needed.
37418 @unnumberedsubsubsec Open Flags
37419 @cindex open flags, in file-i/o protocol
37421 All values are given in hexadecimal representation.
37433 @node mode_t Values
37434 @unnumberedsubsubsec mode_t Values
37435 @cindex mode_t values, in file-i/o protocol
37437 All values are given in octal representation.
37454 @unnumberedsubsubsec Errno Values
37455 @cindex errno values, in file-i/o protocol
37457 All values are given in decimal representation.
37482 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37483 any error value not in the list of supported error numbers.
37486 @unnumberedsubsubsec Lseek Flags
37487 @cindex lseek flags, in file-i/o protocol
37496 @unnumberedsubsubsec Limits
37497 @cindex limits, in file-i/o protocol
37499 All values are given in decimal representation.
37502 INT_MIN -2147483648
37504 UINT_MAX 4294967295
37505 LONG_MIN -9223372036854775808
37506 LONG_MAX 9223372036854775807
37507 ULONG_MAX 18446744073709551615
37510 @node File-I/O Examples
37511 @subsection File-I/O Examples
37512 @cindex file-i/o examples
37514 Example sequence of a write call, file descriptor 3, buffer is at target
37515 address 0x1234, 6 bytes should be written:
37518 <- @code{Fwrite,3,1234,6}
37519 @emph{request memory read from target}
37522 @emph{return "6 bytes written"}
37526 Example sequence of a read call, file descriptor 3, buffer is at target
37527 address 0x1234, 6 bytes should be read:
37530 <- @code{Fread,3,1234,6}
37531 @emph{request memory write to target}
37532 -> @code{X1234,6:XXXXXX}
37533 @emph{return "6 bytes read"}
37537 Example sequence of a read call, call fails on the host due to invalid
37538 file descriptor (@code{EBADF}):
37541 <- @code{Fread,3,1234,6}
37545 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37549 <- @code{Fread,3,1234,6}
37554 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37558 <- @code{Fread,3,1234,6}
37559 -> @code{X1234,6:XXXXXX}
37563 @node Library List Format
37564 @section Library List Format
37565 @cindex library list format, remote protocol
37567 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37568 same process as your application to manage libraries. In this case,
37569 @value{GDBN} can use the loader's symbol table and normal memory
37570 operations to maintain a list of shared libraries. On other
37571 platforms, the operating system manages loaded libraries.
37572 @value{GDBN} can not retrieve the list of currently loaded libraries
37573 through memory operations, so it uses the @samp{qXfer:libraries:read}
37574 packet (@pxref{qXfer library list read}) instead. The remote stub
37575 queries the target's operating system and reports which libraries
37578 The @samp{qXfer:libraries:read} packet returns an XML document which
37579 lists loaded libraries and their offsets. Each library has an
37580 associated name and one or more segment or section base addresses,
37581 which report where the library was loaded in memory.
37583 For the common case of libraries that are fully linked binaries, the
37584 library should have a list of segments. If the target supports
37585 dynamic linking of a relocatable object file, its library XML element
37586 should instead include a list of allocated sections. The segment or
37587 section bases are start addresses, not relocation offsets; they do not
37588 depend on the library's link-time base addresses.
37590 @value{GDBN} must be linked with the Expat library to support XML
37591 library lists. @xref{Expat}.
37593 A simple memory map, with one loaded library relocated by a single
37594 offset, looks like this:
37598 <library name="/lib/libc.so.6">
37599 <segment address="0x10000000"/>
37604 Another simple memory map, with one loaded library with three
37605 allocated sections (.text, .data, .bss), looks like this:
37609 <library name="sharedlib.o">
37610 <section address="0x10000000"/>
37611 <section address="0x20000000"/>
37612 <section address="0x30000000"/>
37617 The format of a library list is described by this DTD:
37620 <!-- library-list: Root element with versioning -->
37621 <!ELEMENT library-list (library)*>
37622 <!ATTLIST library-list version CDATA #FIXED "1.0">
37623 <!ELEMENT library (segment*, section*)>
37624 <!ATTLIST library name CDATA #REQUIRED>
37625 <!ELEMENT segment EMPTY>
37626 <!ATTLIST segment address CDATA #REQUIRED>
37627 <!ELEMENT section EMPTY>
37628 <!ATTLIST section address CDATA #REQUIRED>
37631 In addition, segments and section descriptors cannot be mixed within a
37632 single library element, and you must supply at least one segment or
37633 section for each library.
37635 @node Library List Format for SVR4 Targets
37636 @section Library List Format for SVR4 Targets
37637 @cindex library list format, remote protocol
37639 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37640 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37641 shared libraries. Still a special library list provided by this packet is
37642 more efficient for the @value{GDBN} remote protocol.
37644 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37645 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37646 target, the following parameters are reported:
37650 @code{name}, the absolute file name from the @code{l_name} field of
37651 @code{struct link_map}.
37653 @code{lm} with address of @code{struct link_map} used for TLS
37654 (Thread Local Storage) access.
37656 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37657 @code{struct link_map}. For prelinked libraries this is not an absolute
37658 memory address. It is a displacement of absolute memory address against
37659 address the file was prelinked to during the library load.
37661 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37664 Additionally the single @code{main-lm} attribute specifies address of
37665 @code{struct link_map} used for the main executable. This parameter is used
37666 for TLS access and its presence is optional.
37668 @value{GDBN} must be linked with the Expat library to support XML
37669 SVR4 library lists. @xref{Expat}.
37671 A simple memory map, with two loaded libraries (which do not use prelink),
37675 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37676 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37678 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37680 </library-list-svr>
37683 The format of an SVR4 library list is described by this DTD:
37686 <!-- library-list-svr4: Root element with versioning -->
37687 <!ELEMENT library-list-svr4 (library)*>
37688 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37689 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37690 <!ELEMENT library EMPTY>
37691 <!ATTLIST library name CDATA #REQUIRED>
37692 <!ATTLIST library lm CDATA #REQUIRED>
37693 <!ATTLIST library l_addr CDATA #REQUIRED>
37694 <!ATTLIST library l_ld CDATA #REQUIRED>
37697 @node Memory Map Format
37698 @section Memory Map Format
37699 @cindex memory map format
37701 To be able to write into flash memory, @value{GDBN} needs to obtain a
37702 memory map from the target. This section describes the format of the
37705 The memory map is obtained using the @samp{qXfer:memory-map:read}
37706 (@pxref{qXfer memory map read}) packet and is an XML document that
37707 lists memory regions.
37709 @value{GDBN} must be linked with the Expat library to support XML
37710 memory maps. @xref{Expat}.
37712 The top-level structure of the document is shown below:
37715 <?xml version="1.0"?>
37716 <!DOCTYPE memory-map
37717 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37718 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37724 Each region can be either:
37729 A region of RAM starting at @var{addr} and extending for @var{length}
37733 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37738 A region of read-only memory:
37741 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37746 A region of flash memory, with erasure blocks @var{blocksize}
37750 <memory type="flash" start="@var{addr}" length="@var{length}">
37751 <property name="blocksize">@var{blocksize}</property>
37757 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37758 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37759 packets to write to addresses in such ranges.
37761 The formal DTD for memory map format is given below:
37764 <!-- ................................................... -->
37765 <!-- Memory Map XML DTD ................................ -->
37766 <!-- File: memory-map.dtd .............................. -->
37767 <!-- .................................... .............. -->
37768 <!-- memory-map.dtd -->
37769 <!-- memory-map: Root element with versioning -->
37770 <!ELEMENT memory-map (memory | property)>
37771 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37772 <!ELEMENT memory (property)>
37773 <!-- memory: Specifies a memory region,
37774 and its type, or device. -->
37775 <!ATTLIST memory type CDATA #REQUIRED
37776 start CDATA #REQUIRED
37777 length CDATA #REQUIRED
37778 device CDATA #IMPLIED>
37779 <!-- property: Generic attribute tag -->
37780 <!ELEMENT property (#PCDATA | property)*>
37781 <!ATTLIST property name CDATA #REQUIRED>
37784 @node Thread List Format
37785 @section Thread List Format
37786 @cindex thread list format
37788 To efficiently update the list of threads and their attributes,
37789 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37790 (@pxref{qXfer threads read}) and obtains the XML document with
37791 the following structure:
37794 <?xml version="1.0"?>
37796 <thread id="id" core="0">
37797 ... description ...
37802 Each @samp{thread} element must have the @samp{id} attribute that
37803 identifies the thread (@pxref{thread-id syntax}). The
37804 @samp{core} attribute, if present, specifies which processor core
37805 the thread was last executing on. The content of the of @samp{thread}
37806 element is interpreted as human-readable auxilliary information.
37808 @node Traceframe Info Format
37809 @section Traceframe Info Format
37810 @cindex traceframe info format
37812 To be able to know which objects in the inferior can be examined when
37813 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37814 memory ranges, registers and trace state variables that have been
37815 collected in a traceframe.
37817 This list is obtained using the @samp{qXfer:traceframe-info:read}
37818 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37820 @value{GDBN} must be linked with the Expat library to support XML
37821 traceframe info discovery. @xref{Expat}.
37823 The top-level structure of the document is shown below:
37826 <?xml version="1.0"?>
37827 <!DOCTYPE traceframe-info
37828 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37829 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37835 Each traceframe block can be either:
37840 A region of collected memory starting at @var{addr} and extending for
37841 @var{length} bytes from there:
37844 <memory start="@var{addr}" length="@var{length}"/>
37849 The formal DTD for the traceframe info format is given below:
37852 <!ELEMENT traceframe-info (memory)* >
37853 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37855 <!ELEMENT memory EMPTY>
37856 <!ATTLIST memory start CDATA #REQUIRED
37857 length CDATA #REQUIRED>
37860 @include agentexpr.texi
37862 @node Target Descriptions
37863 @appendix Target Descriptions
37864 @cindex target descriptions
37866 One of the challenges of using @value{GDBN} to debug embedded systems
37867 is that there are so many minor variants of each processor
37868 architecture in use. It is common practice for vendors to start with
37869 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37870 and then make changes to adapt it to a particular market niche. Some
37871 architectures have hundreds of variants, available from dozens of
37872 vendors. This leads to a number of problems:
37876 With so many different customized processors, it is difficult for
37877 the @value{GDBN} maintainers to keep up with the changes.
37879 Since individual variants may have short lifetimes or limited
37880 audiences, it may not be worthwhile to carry information about every
37881 variant in the @value{GDBN} source tree.
37883 When @value{GDBN} does support the architecture of the embedded system
37884 at hand, the task of finding the correct architecture name to give the
37885 @command{set architecture} command can be error-prone.
37888 To address these problems, the @value{GDBN} remote protocol allows a
37889 target system to not only identify itself to @value{GDBN}, but to
37890 actually describe its own features. This lets @value{GDBN} support
37891 processor variants it has never seen before --- to the extent that the
37892 descriptions are accurate, and that @value{GDBN} understands them.
37894 @value{GDBN} must be linked with the Expat library to support XML
37895 target descriptions. @xref{Expat}.
37898 * Retrieving Descriptions:: How descriptions are fetched from a target.
37899 * Target Description Format:: The contents of a target description.
37900 * Predefined Target Types:: Standard types available for target
37902 * Standard Target Features:: Features @value{GDBN} knows about.
37905 @node Retrieving Descriptions
37906 @section Retrieving Descriptions
37908 Target descriptions can be read from the target automatically, or
37909 specified by the user manually. The default behavior is to read the
37910 description from the target. @value{GDBN} retrieves it via the remote
37911 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37912 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37913 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37914 XML document, of the form described in @ref{Target Description
37917 Alternatively, you can specify a file to read for the target description.
37918 If a file is set, the target will not be queried. The commands to
37919 specify a file are:
37922 @cindex set tdesc filename
37923 @item set tdesc filename @var{path}
37924 Read the target description from @var{path}.
37926 @cindex unset tdesc filename
37927 @item unset tdesc filename
37928 Do not read the XML target description from a file. @value{GDBN}
37929 will use the description supplied by the current target.
37931 @cindex show tdesc filename
37932 @item show tdesc filename
37933 Show the filename to read for a target description, if any.
37937 @node Target Description Format
37938 @section Target Description Format
37939 @cindex target descriptions, XML format
37941 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37942 document which complies with the Document Type Definition provided in
37943 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37944 means you can use generally available tools like @command{xmllint} to
37945 check that your feature descriptions are well-formed and valid.
37946 However, to help people unfamiliar with XML write descriptions for
37947 their targets, we also describe the grammar here.
37949 Target descriptions can identify the architecture of the remote target
37950 and (for some architectures) provide information about custom register
37951 sets. They can also identify the OS ABI of the remote target.
37952 @value{GDBN} can use this information to autoconfigure for your
37953 target, or to warn you if you connect to an unsupported target.
37955 Here is a simple target description:
37958 <target version="1.0">
37959 <architecture>i386:x86-64</architecture>
37964 This minimal description only says that the target uses
37965 the x86-64 architecture.
37967 A target description has the following overall form, with [ ] marking
37968 optional elements and @dots{} marking repeatable elements. The elements
37969 are explained further below.
37972 <?xml version="1.0"?>
37973 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37974 <target version="1.0">
37975 @r{[}@var{architecture}@r{]}
37976 @r{[}@var{osabi}@r{]}
37977 @r{[}@var{compatible}@r{]}
37978 @r{[}@var{feature}@dots{}@r{]}
37983 The description is generally insensitive to whitespace and line
37984 breaks, under the usual common-sense rules. The XML version
37985 declaration and document type declaration can generally be omitted
37986 (@value{GDBN} does not require them), but specifying them may be
37987 useful for XML validation tools. The @samp{version} attribute for
37988 @samp{<target>} may also be omitted, but we recommend
37989 including it; if future versions of @value{GDBN} use an incompatible
37990 revision of @file{gdb-target.dtd}, they will detect and report
37991 the version mismatch.
37993 @subsection Inclusion
37994 @cindex target descriptions, inclusion
37997 @cindex <xi:include>
38000 It can sometimes be valuable to split a target description up into
38001 several different annexes, either for organizational purposes, or to
38002 share files between different possible target descriptions. You can
38003 divide a description into multiple files by replacing any element of
38004 the target description with an inclusion directive of the form:
38007 <xi:include href="@var{document}"/>
38011 When @value{GDBN} encounters an element of this form, it will retrieve
38012 the named XML @var{document}, and replace the inclusion directive with
38013 the contents of that document. If the current description was read
38014 using @samp{qXfer}, then so will be the included document;
38015 @var{document} will be interpreted as the name of an annex. If the
38016 current description was read from a file, @value{GDBN} will look for
38017 @var{document} as a file in the same directory where it found the
38018 original description.
38020 @subsection Architecture
38021 @cindex <architecture>
38023 An @samp{<architecture>} element has this form:
38026 <architecture>@var{arch}</architecture>
38029 @var{arch} is one of the architectures from the set accepted by
38030 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38033 @cindex @code{<osabi>}
38035 This optional field was introduced in @value{GDBN} version 7.0.
38036 Previous versions of @value{GDBN} ignore it.
38038 An @samp{<osabi>} element has this form:
38041 <osabi>@var{abi-name}</osabi>
38044 @var{abi-name} is an OS ABI name from the same selection accepted by
38045 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38047 @subsection Compatible Architecture
38048 @cindex @code{<compatible>}
38050 This optional field was introduced in @value{GDBN} version 7.0.
38051 Previous versions of @value{GDBN} ignore it.
38053 A @samp{<compatible>} element has this form:
38056 <compatible>@var{arch}</compatible>
38059 @var{arch} is one of the architectures from the set accepted by
38060 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38062 A @samp{<compatible>} element is used to specify that the target
38063 is able to run binaries in some other than the main target architecture
38064 given by the @samp{<architecture>} element. For example, on the
38065 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38066 or @code{powerpc:common64}, but the system is able to run binaries
38067 in the @code{spu} architecture as well. The way to describe this
38068 capability with @samp{<compatible>} is as follows:
38071 <architecture>powerpc:common</architecture>
38072 <compatible>spu</compatible>
38075 @subsection Features
38078 Each @samp{<feature>} describes some logical portion of the target
38079 system. Features are currently used to describe available CPU
38080 registers and the types of their contents. A @samp{<feature>} element
38084 <feature name="@var{name}">
38085 @r{[}@var{type}@dots{}@r{]}
38091 Each feature's name should be unique within the description. The name
38092 of a feature does not matter unless @value{GDBN} has some special
38093 knowledge of the contents of that feature; if it does, the feature
38094 should have its standard name. @xref{Standard Target Features}.
38098 Any register's value is a collection of bits which @value{GDBN} must
38099 interpret. The default interpretation is a two's complement integer,
38100 but other types can be requested by name in the register description.
38101 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38102 Target Types}), and the description can define additional composite types.
38104 Each type element must have an @samp{id} attribute, which gives
38105 a unique (within the containing @samp{<feature>}) name to the type.
38106 Types must be defined before they are used.
38109 Some targets offer vector registers, which can be treated as arrays
38110 of scalar elements. These types are written as @samp{<vector>} elements,
38111 specifying the array element type, @var{type}, and the number of elements,
38115 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38119 If a register's value is usefully viewed in multiple ways, define it
38120 with a union type containing the useful representations. The
38121 @samp{<union>} element contains one or more @samp{<field>} elements,
38122 each of which has a @var{name} and a @var{type}:
38125 <union id="@var{id}">
38126 <field name="@var{name}" type="@var{type}"/>
38132 If a register's value is composed from several separate values, define
38133 it with a structure type. There are two forms of the @samp{<struct>}
38134 element; a @samp{<struct>} element must either contain only bitfields
38135 or contain no bitfields. If the structure contains only bitfields,
38136 its total size in bytes must be specified, each bitfield must have an
38137 explicit start and end, and bitfields are automatically assigned an
38138 integer type. The field's @var{start} should be less than or
38139 equal to its @var{end}, and zero represents the least significant bit.
38142 <struct id="@var{id}" size="@var{size}">
38143 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38148 If the structure contains no bitfields, then each field has an
38149 explicit type, and no implicit padding is added.
38152 <struct id="@var{id}">
38153 <field name="@var{name}" type="@var{type}"/>
38159 If a register's value is a series of single-bit flags, define it with
38160 a flags type. The @samp{<flags>} element has an explicit @var{size}
38161 and contains one or more @samp{<field>} elements. Each field has a
38162 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38166 <flags id="@var{id}" size="@var{size}">
38167 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38172 @subsection Registers
38175 Each register is represented as an element with this form:
38178 <reg name="@var{name}"
38179 bitsize="@var{size}"
38180 @r{[}regnum="@var{num}"@r{]}
38181 @r{[}save-restore="@var{save-restore}"@r{]}
38182 @r{[}type="@var{type}"@r{]}
38183 @r{[}group="@var{group}"@r{]}/>
38187 The components are as follows:
38192 The register's name; it must be unique within the target description.
38195 The register's size, in bits.
38198 The register's number. If omitted, a register's number is one greater
38199 than that of the previous register (either in the current feature or in
38200 a preceding feature); the first register in the target description
38201 defaults to zero. This register number is used to read or write
38202 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38203 packets, and registers appear in the @code{g} and @code{G} packets
38204 in order of increasing register number.
38207 Whether the register should be preserved across inferior function
38208 calls; this must be either @code{yes} or @code{no}. The default is
38209 @code{yes}, which is appropriate for most registers except for
38210 some system control registers; this is not related to the target's
38214 The type of the register. @var{type} may be a predefined type, a type
38215 defined in the current feature, or one of the special types @code{int}
38216 and @code{float}. @code{int} is an integer type of the correct size
38217 for @var{bitsize}, and @code{float} is a floating point type (in the
38218 architecture's normal floating point format) of the correct size for
38219 @var{bitsize}. The default is @code{int}.
38222 The register group to which this register belongs. @var{group} must
38223 be either @code{general}, @code{float}, or @code{vector}. If no
38224 @var{group} is specified, @value{GDBN} will not display the register
38225 in @code{info registers}.
38229 @node Predefined Target Types
38230 @section Predefined Target Types
38231 @cindex target descriptions, predefined types
38233 Type definitions in the self-description can build up composite types
38234 from basic building blocks, but can not define fundamental types. Instead,
38235 standard identifiers are provided by @value{GDBN} for the fundamental
38236 types. The currently supported types are:
38245 Signed integer types holding the specified number of bits.
38252 Unsigned integer types holding the specified number of bits.
38256 Pointers to unspecified code and data. The program counter and
38257 any dedicated return address register may be marked as code
38258 pointers; printing a code pointer converts it into a symbolic
38259 address. The stack pointer and any dedicated address registers
38260 may be marked as data pointers.
38263 Single precision IEEE floating point.
38266 Double precision IEEE floating point.
38269 The 12-byte extended precision format used by ARM FPA registers.
38272 The 10-byte extended precision format used by x87 registers.
38275 32bit @sc{eflags} register used by x86.
38278 32bit @sc{mxcsr} register used by x86.
38282 @node Standard Target Features
38283 @section Standard Target Features
38284 @cindex target descriptions, standard features
38286 A target description must contain either no registers or all the
38287 target's registers. If the description contains no registers, then
38288 @value{GDBN} will assume a default register layout, selected based on
38289 the architecture. If the description contains any registers, the
38290 default layout will not be used; the standard registers must be
38291 described in the target description, in such a way that @value{GDBN}
38292 can recognize them.
38294 This is accomplished by giving specific names to feature elements
38295 which contain standard registers. @value{GDBN} will look for features
38296 with those names and verify that they contain the expected registers;
38297 if any known feature is missing required registers, or if any required
38298 feature is missing, @value{GDBN} will reject the target
38299 description. You can add additional registers to any of the
38300 standard features --- @value{GDBN} will display them just as if
38301 they were added to an unrecognized feature.
38303 This section lists the known features and their expected contents.
38304 Sample XML documents for these features are included in the
38305 @value{GDBN} source tree, in the directory @file{gdb/features}.
38307 Names recognized by @value{GDBN} should include the name of the
38308 company or organization which selected the name, and the overall
38309 architecture to which the feature applies; so e.g.@: the feature
38310 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38312 The names of registers are not case sensitive for the purpose
38313 of recognizing standard features, but @value{GDBN} will only display
38314 registers using the capitalization used in the description.
38321 * PowerPC Features::
38327 @subsection ARM Features
38328 @cindex target descriptions, ARM features
38330 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38332 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38333 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38335 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38336 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38337 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38340 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38341 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38343 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38344 it should contain at least registers @samp{wR0} through @samp{wR15} and
38345 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38346 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38348 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38349 should contain at least registers @samp{d0} through @samp{d15}. If
38350 they are present, @samp{d16} through @samp{d31} should also be included.
38351 @value{GDBN} will synthesize the single-precision registers from
38352 halves of the double-precision registers.
38354 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38355 need to contain registers; it instructs @value{GDBN} to display the
38356 VFP double-precision registers as vectors and to synthesize the
38357 quad-precision registers from pairs of double-precision registers.
38358 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38359 be present and include 32 double-precision registers.
38361 @node i386 Features
38362 @subsection i386 Features
38363 @cindex target descriptions, i386 features
38365 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38366 targets. It should describe the following registers:
38370 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38372 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38374 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38375 @samp{fs}, @samp{gs}
38377 @samp{st0} through @samp{st7}
38379 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38380 @samp{foseg}, @samp{fooff} and @samp{fop}
38383 The register sets may be different, depending on the target.
38385 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38386 describe registers:
38390 @samp{xmm0} through @samp{xmm7} for i386
38392 @samp{xmm0} through @samp{xmm15} for amd64
38397 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38398 @samp{org.gnu.gdb.i386.sse} feature. It should
38399 describe the upper 128 bits of @sc{ymm} registers:
38403 @samp{ymm0h} through @samp{ymm7h} for i386
38405 @samp{ymm0h} through @samp{ymm15h} for amd64
38408 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38409 describe a single register, @samp{orig_eax}.
38411 @node MIPS Features
38412 @subsection MIPS Features
38413 @cindex target descriptions, MIPS features
38415 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38416 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38417 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38420 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38421 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38422 registers. They may be 32-bit or 64-bit depending on the target.
38424 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38425 it may be optional in a future version of @value{GDBN}. It should
38426 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38427 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38429 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38430 contain a single register, @samp{restart}, which is used by the
38431 Linux kernel to control restartable syscalls.
38433 @node M68K Features
38434 @subsection M68K Features
38435 @cindex target descriptions, M68K features
38438 @item @samp{org.gnu.gdb.m68k.core}
38439 @itemx @samp{org.gnu.gdb.coldfire.core}
38440 @itemx @samp{org.gnu.gdb.fido.core}
38441 One of those features must be always present.
38442 The feature that is present determines which flavor of m68k is
38443 used. The feature that is present should contain registers
38444 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38445 @samp{sp}, @samp{ps} and @samp{pc}.
38447 @item @samp{org.gnu.gdb.coldfire.fp}
38448 This feature is optional. If present, it should contain registers
38449 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38453 @node PowerPC Features
38454 @subsection PowerPC Features
38455 @cindex target descriptions, PowerPC features
38457 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38458 targets. It should contain registers @samp{r0} through @samp{r31},
38459 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38460 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38462 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38463 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38465 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38466 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38469 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38470 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38471 will combine these registers with the floating point registers
38472 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38473 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38474 through @samp{vs63}, the set of vector registers for POWER7.
38476 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38477 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38478 @samp{spefscr}. SPE targets should provide 32-bit registers in
38479 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38480 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38481 these to present registers @samp{ev0} through @samp{ev31} to the
38484 @node TIC6x Features
38485 @subsection TMS320C6x Features
38486 @cindex target descriptions, TIC6x features
38487 @cindex target descriptions, TMS320C6x features
38488 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38489 targets. It should contain registers @samp{A0} through @samp{A15},
38490 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38492 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38493 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38494 through @samp{B31}.
38496 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38497 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38499 @node Operating System Information
38500 @appendix Operating System Information
38501 @cindex operating system information
38507 Users of @value{GDBN} often wish to obtain information about the state of
38508 the operating system running on the target---for example the list of
38509 processes, or the list of open files. This section describes the
38510 mechanism that makes it possible. This mechanism is similar to the
38511 target features mechanism (@pxref{Target Descriptions}), but focuses
38512 on a different aspect of target.
38514 Operating system information is retrived from the target via the
38515 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38516 read}). The object name in the request should be @samp{osdata}, and
38517 the @var{annex} identifies the data to be fetched.
38520 @appendixsection Process list
38521 @cindex operating system information, process list
38523 When requesting the process list, the @var{annex} field in the
38524 @samp{qXfer} request should be @samp{processes}. The returned data is
38525 an XML document. The formal syntax of this document is defined in
38526 @file{gdb/features/osdata.dtd}.
38528 An example document is:
38531 <?xml version="1.0"?>
38532 <!DOCTYPE target SYSTEM "osdata.dtd">
38533 <osdata type="processes">
38535 <column name="pid">1</column>
38536 <column name="user">root</column>
38537 <column name="command">/sbin/init</column>
38538 <column name="cores">1,2,3</column>
38543 Each item should include a column whose name is @samp{pid}. The value
38544 of that column should identify the process on the target. The
38545 @samp{user} and @samp{command} columns are optional, and will be
38546 displayed by @value{GDBN}. The @samp{cores} column, if present,
38547 should contain a comma-separated list of cores that this process
38548 is running on. Target may provide additional columns,
38549 which @value{GDBN} currently ignores.
38551 @node Trace File Format
38552 @appendix Trace File Format
38553 @cindex trace file format
38555 The trace file comes in three parts: a header, a textual description
38556 section, and a trace frame section with binary data.
38558 The header has the form @code{\x7fTRACE0\n}. The first byte is
38559 @code{0x7f} so as to indicate that the file contains binary data,
38560 while the @code{0} is a version number that may have different values
38563 The description section consists of multiple lines of @sc{ascii} text
38564 separated by newline characters (@code{0xa}). The lines may include a
38565 variety of optional descriptive or context-setting information, such
38566 as tracepoint definitions or register set size. @value{GDBN} will
38567 ignore any line that it does not recognize. An empty line marks the end
38570 @c FIXME add some specific types of data
38572 The trace frame section consists of a number of consecutive frames.
38573 Each frame begins with a two-byte tracepoint number, followed by a
38574 four-byte size giving the amount of data in the frame. The data in
38575 the frame consists of a number of blocks, each introduced by a
38576 character indicating its type (at least register, memory, and trace
38577 state variable). The data in this section is raw binary, not a
38578 hexadecimal or other encoding; its endianness matches the target's
38581 @c FIXME bi-arch may require endianness/arch info in description section
38584 @item R @var{bytes}
38585 Register block. The number and ordering of bytes matches that of a
38586 @code{g} packet in the remote protocol. Note that these are the
38587 actual bytes, in target order and @value{GDBN} register order, not a
38588 hexadecimal encoding.
38590 @item M @var{address} @var{length} @var{bytes}...
38591 Memory block. This is a contiguous block of memory, at the 8-byte
38592 address @var{address}, with a 2-byte length @var{length}, followed by
38593 @var{length} bytes.
38595 @item V @var{number} @var{value}
38596 Trace state variable block. This records the 8-byte signed value
38597 @var{value} of trace state variable numbered @var{number}.
38601 Future enhancements of the trace file format may include additional types
38604 @node Index Section Format
38605 @appendix @code{.gdb_index} section format
38606 @cindex .gdb_index section format
38607 @cindex index section format
38609 This section documents the index section that is created by @code{save
38610 gdb-index} (@pxref{Index Files}). The index section is
38611 DWARF-specific; some knowledge of DWARF is assumed in this
38614 The mapped index file format is designed to be directly
38615 @code{mmap}able on any architecture. In most cases, a datum is
38616 represented using a little-endian 32-bit integer value, called an
38617 @code{offset_type}. Big endian machines must byte-swap the values
38618 before using them. Exceptions to this rule are noted. The data is
38619 laid out such that alignment is always respected.
38621 A mapped index consists of several areas, laid out in order.
38625 The file header. This is a sequence of values, of @code{offset_type}
38626 unless otherwise noted:
38630 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38631 Version 4 differs by its hashing function.
38634 The offset, from the start of the file, of the CU list.
38637 The offset, from the start of the file, of the types CU list. Note
38638 that this area can be empty, in which case this offset will be equal
38639 to the next offset.
38642 The offset, from the start of the file, of the address area.
38645 The offset, from the start of the file, of the symbol table.
38648 The offset, from the start of the file, of the constant pool.
38652 The CU list. This is a sequence of pairs of 64-bit little-endian
38653 values, sorted by the CU offset. The first element in each pair is
38654 the offset of a CU in the @code{.debug_info} section. The second
38655 element in each pair is the length of that CU. References to a CU
38656 elsewhere in the map are done using a CU index, which is just the
38657 0-based index into this table. Note that if there are type CUs, then
38658 conceptually CUs and type CUs form a single list for the purposes of
38662 The types CU list. This is a sequence of triplets of 64-bit
38663 little-endian values. In a triplet, the first value is the CU offset,
38664 the second value is the type offset in the CU, and the third value is
38665 the type signature. The types CU list is not sorted.
38668 The address area. The address area consists of a sequence of address
38669 entries. Each address entry has three elements:
38673 The low address. This is a 64-bit little-endian value.
38676 The high address. This is a 64-bit little-endian value. Like
38677 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38680 The CU index. This is an @code{offset_type} value.
38684 The symbol table. This is an open-addressed hash table. The size of
38685 the hash table is always a power of 2.
38687 Each slot in the hash table consists of a pair of @code{offset_type}
38688 values. The first value is the offset of the symbol's name in the
38689 constant pool. The second value is the offset of the CU vector in the
38692 If both values are 0, then this slot in the hash table is empty. This
38693 is ok because while 0 is a valid constant pool index, it cannot be a
38694 valid index for both a string and a CU vector.
38696 The hash value for a table entry is computed by applying an
38697 iterative hash function to the symbol's name. Starting with an
38698 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38699 the string is incorporated into the hash using the formula depending on the
38704 The formula is @code{r = r * 67 + c - 113}.
38707 The formula is @code{r = r * 67 + tolower (c) - 113}.
38710 The terminating @samp{\0} is not incorporated into the hash.
38712 The step size used in the hash table is computed via
38713 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38714 value, and @samp{size} is the size of the hash table. The step size
38715 is used to find the next candidate slot when handling a hash
38718 The names of C@t{++} symbols in the hash table are canonicalized. We
38719 don't currently have a simple description of the canonicalization
38720 algorithm; if you intend to create new index sections, you must read
38724 The constant pool. This is simply a bunch of bytes. It is organized
38725 so that alignment is correct: CU vectors are stored first, followed by
38728 A CU vector in the constant pool is a sequence of @code{offset_type}
38729 values. The first value is the number of CU indices in the vector.
38730 Each subsequent value is the index of a CU in the CU list. This
38731 element in the hash table is used to indicate which CUs define the
38734 A string in the constant pool is zero-terminated.
38739 @node GNU Free Documentation License
38740 @appendix GNU Free Documentation License
38749 % I think something like @colophon should be in texinfo. In the
38751 \long\def\colophon{\hbox to0pt{}\vfill
38752 \centerline{The body of this manual is set in}
38753 \centerline{\fontname\tenrm,}
38754 \centerline{with headings in {\bf\fontname\tenbf}}
38755 \centerline{and examples in {\tt\fontname\tentt}.}
38756 \centerline{{\it\fontname\tenit\/},}
38757 \centerline{{\bf\fontname\tenbf}, and}
38758 \centerline{{\sl\fontname\tensl\/}}
38759 \centerline{are used for emphasis.}\vfill}
38761 % Blame: doc@cygnus.com, 1991.