1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @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_delete to_fputs to_put to_rewind
1596 to_data to_flush to_isatty to_read to_write
1600 This is because the @code{gdb_stdout} is a variable of the type
1601 @code{struct ui_file} that is defined in @value{GDBN} sources as
1608 ui_file_flush_ftype *to_flush;
1609 ui_file_write_ftype *to_write;
1610 ui_file_fputs_ftype *to_fputs;
1611 ui_file_read_ftype *to_read;
1612 ui_file_delete_ftype *to_delete;
1613 ui_file_isatty_ftype *to_isatty;
1614 ui_file_rewind_ftype *to_rewind;
1615 ui_file_put_ftype *to_put;
1622 @section Getting Help
1623 @cindex online documentation
1626 You can always ask @value{GDBN} itself for information on its commands,
1627 using the command @code{help}.
1630 @kindex h @r{(@code{help})}
1633 You can use @code{help} (abbreviated @code{h}) with no arguments to
1634 display a short list of named classes of commands:
1638 List of classes of commands:
1640 aliases -- Aliases of other commands
1641 breakpoints -- Making program stop at certain points
1642 data -- Examining data
1643 files -- Specifying and examining files
1644 internals -- Maintenance commands
1645 obscure -- Obscure features
1646 running -- Running the program
1647 stack -- Examining the stack
1648 status -- Status inquiries
1649 support -- Support facilities
1650 tracepoints -- Tracing of program execution without
1651 stopping the program
1652 user-defined -- User-defined commands
1654 Type "help" followed by a class name for a list of
1655 commands in that class.
1656 Type "help" followed by command name for full
1658 Command name abbreviations are allowed if unambiguous.
1661 @c the above line break eliminates huge line overfull...
1663 @item help @var{class}
1664 Using one of the general help classes as an argument, you can get a
1665 list of the individual commands in that class. For example, here is the
1666 help display for the class @code{status}:
1669 (@value{GDBP}) help status
1674 @c Line break in "show" line falsifies real output, but needed
1675 @c to fit in smallbook page size.
1676 info -- Generic command for showing things
1677 about the program being debugged
1678 show -- Generic command for showing things
1681 Type "help" followed by command name for full
1683 Command name abbreviations are allowed if unambiguous.
1687 @item help @var{command}
1688 With a command name as @code{help} argument, @value{GDBN} displays a
1689 short paragraph on how to use that command.
1692 @item apropos @var{args}
1693 The @code{apropos} command searches through all of the @value{GDBN}
1694 commands, and their documentation, for the regular expression specified in
1695 @var{args}. It prints out all matches found. For example:
1706 set symbol-reloading -- Set dynamic symbol table reloading
1707 multiple times in one run
1708 show symbol-reloading -- Show dynamic symbol table reloading
1709 multiple times in one run
1714 @item complete @var{args}
1715 The @code{complete @var{args}} command lists all the possible completions
1716 for the beginning of a command. Use @var{args} to specify the beginning of the
1717 command you want completed. For example:
1723 @noindent results in:
1734 @noindent This is intended for use by @sc{gnu} Emacs.
1737 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1738 and @code{show} to inquire about the state of your program, or the state
1739 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1740 manual introduces each of them in the appropriate context. The listings
1741 under @code{info} and under @code{show} in the Index point to
1742 all the sub-commands. @xref{Index}.
1747 @kindex i @r{(@code{info})}
1749 This command (abbreviated @code{i}) is for describing the state of your
1750 program. For example, you can show the arguments passed to a function
1751 with @code{info args}, list the registers currently in use with @code{info
1752 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1753 You can get a complete list of the @code{info} sub-commands with
1754 @w{@code{help info}}.
1758 You can assign the result of an expression to an environment variable with
1759 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1760 @code{set prompt $}.
1764 In contrast to @code{info}, @code{show} is for describing the state of
1765 @value{GDBN} itself.
1766 You can change most of the things you can @code{show}, by using the
1767 related command @code{set}; for example, you can control what number
1768 system is used for displays with @code{set radix}, or simply inquire
1769 which is currently in use with @code{show radix}.
1772 To display all the settable parameters and their current
1773 values, you can use @code{show} with no arguments; you may also use
1774 @code{info set}. Both commands produce the same display.
1775 @c FIXME: "info set" violates the rule that "info" is for state of
1776 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1777 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1781 Here are three miscellaneous @code{show} subcommands, all of which are
1782 exceptional in lacking corresponding @code{set} commands:
1785 @kindex show version
1786 @cindex @value{GDBN} version number
1788 Show what version of @value{GDBN} is running. You should include this
1789 information in @value{GDBN} bug-reports. If multiple versions of
1790 @value{GDBN} are in use at your site, you may need to determine which
1791 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1792 commands are introduced, and old ones may wither away. Also, many
1793 system vendors ship variant versions of @value{GDBN}, and there are
1794 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1795 The version number is the same as the one announced when you start
1798 @kindex show copying
1799 @kindex info copying
1800 @cindex display @value{GDBN} copyright
1803 Display information about permission for copying @value{GDBN}.
1805 @kindex show warranty
1806 @kindex info warranty
1808 @itemx info warranty
1809 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1810 if your version of @value{GDBN} comes with one.
1815 @chapter Running Programs Under @value{GDBN}
1817 When you run a program under @value{GDBN}, you must first generate
1818 debugging information when you compile it.
1820 You may start @value{GDBN} with its arguments, if any, in an environment
1821 of your choice. If you are doing native debugging, you may redirect
1822 your program's input and output, debug an already running process, or
1823 kill a child process.
1826 * Compilation:: Compiling for debugging
1827 * Starting:: Starting your program
1828 * Arguments:: Your program's arguments
1829 * Environment:: Your program's environment
1831 * Working Directory:: Your program's working directory
1832 * Input/Output:: Your program's input and output
1833 * Attach:: Debugging an already-running process
1834 * Kill Process:: Killing the child process
1836 * Inferiors and Programs:: Debugging multiple inferiors and programs
1837 * Threads:: Debugging programs with multiple threads
1838 * Forks:: Debugging forks
1839 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1843 @section Compiling for Debugging
1845 In order to debug a program effectively, you need to generate
1846 debugging information when you compile it. This debugging information
1847 is stored in the object file; it describes the data type of each
1848 variable or function and the correspondence between source line numbers
1849 and addresses in the executable code.
1851 To request debugging information, specify the @samp{-g} option when you run
1854 Programs that are to be shipped to your customers are compiled with
1855 optimizations, using the @samp{-O} compiler option. However, some
1856 compilers are unable to handle the @samp{-g} and @samp{-O} options
1857 together. Using those compilers, you cannot generate optimized
1858 executables containing debugging information.
1860 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1861 without @samp{-O}, making it possible to debug optimized code. We
1862 recommend that you @emph{always} use @samp{-g} whenever you compile a
1863 program. You may think your program is correct, but there is no sense
1864 in pushing your luck. For more information, see @ref{Optimized Code}.
1866 Older versions of the @sc{gnu} C compiler permitted a variant option
1867 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1868 format; if your @sc{gnu} C compiler has this option, do not use it.
1870 @value{GDBN} knows about preprocessor macros and can show you their
1871 expansion (@pxref{Macros}). Most compilers do not include information
1872 about preprocessor macros in the debugging information if you specify
1873 the @option{-g} flag alone, because this information is rather large.
1874 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1875 provides macro information if you specify the options
1876 @option{-gdwarf-2} and @option{-g3}; the former option requests
1877 debugging information in the Dwarf 2 format, and the latter requests
1878 ``extra information''. In the future, we hope to find more compact
1879 ways to represent macro information, so that it can be included with
1884 @section Starting your Program
1890 @kindex r @r{(@code{run})}
1893 Use the @code{run} command to start your program under @value{GDBN}.
1894 You must first specify the program name (except on VxWorks) with an
1895 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1896 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1897 (@pxref{Files, ,Commands to Specify Files}).
1901 If you are running your program in an execution environment that
1902 supports processes, @code{run} creates an inferior process and makes
1903 that process run your program. In some environments without processes,
1904 @code{run} jumps to the start of your program. Other targets,
1905 like @samp{remote}, are always running. If you get an error
1906 message like this one:
1909 The "remote" target does not support "run".
1910 Try "help target" or "continue".
1914 then use @code{continue} to run your program. You may need @code{load}
1915 first (@pxref{load}).
1917 The execution of a program is affected by certain information it
1918 receives from its superior. @value{GDBN} provides ways to specify this
1919 information, which you must do @emph{before} starting your program. (You
1920 can change it after starting your program, but such changes only affect
1921 your program the next time you start it.) This information may be
1922 divided into four categories:
1925 @item The @emph{arguments.}
1926 Specify the arguments to give your program as the arguments of the
1927 @code{run} command. If a shell is available on your target, the shell
1928 is used to pass the arguments, so that you may use normal conventions
1929 (such as wildcard expansion or variable substitution) in describing
1931 In Unix systems, you can control which shell is used with the
1932 @code{SHELL} environment variable.
1933 @xref{Arguments, ,Your Program's Arguments}.
1935 @item The @emph{environment.}
1936 Your program normally inherits its environment from @value{GDBN}, but you can
1937 use the @value{GDBN} commands @code{set environment} and @code{unset
1938 environment} to change parts of the environment that affect
1939 your program. @xref{Environment, ,Your Program's Environment}.
1941 @item The @emph{working directory.}
1942 Your program inherits its working directory from @value{GDBN}. You can set
1943 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1944 @xref{Working Directory, ,Your Program's Working Directory}.
1946 @item The @emph{standard input and output.}
1947 Your program normally uses the same device for standard input and
1948 standard output as @value{GDBN} is using. You can redirect input and output
1949 in the @code{run} command line, or you can use the @code{tty} command to
1950 set a different device for your program.
1951 @xref{Input/Output, ,Your Program's Input and Output}.
1954 @emph{Warning:} While input and output redirection work, you cannot use
1955 pipes to pass the output of the program you are debugging to another
1956 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1960 When you issue the @code{run} command, your program begins to execute
1961 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1962 of how to arrange for your program to stop. Once your program has
1963 stopped, you may call functions in your program, using the @code{print}
1964 or @code{call} commands. @xref{Data, ,Examining Data}.
1966 If the modification time of your symbol file has changed since the last
1967 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1968 table, and reads it again. When it does this, @value{GDBN} tries to retain
1969 your current breakpoints.
1974 @cindex run to main procedure
1975 The name of the main procedure can vary from language to language.
1976 With C or C@t{++}, the main procedure name is always @code{main}, but
1977 other languages such as Ada do not require a specific name for their
1978 main procedure. The debugger provides a convenient way to start the
1979 execution of the program and to stop at the beginning of the main
1980 procedure, depending on the language used.
1982 The @samp{start} command does the equivalent of setting a temporary
1983 breakpoint at the beginning of the main procedure and then invoking
1984 the @samp{run} command.
1986 @cindex elaboration phase
1987 Some programs contain an @dfn{elaboration} phase where some startup code is
1988 executed before the main procedure is called. This depends on the
1989 languages used to write your program. In C@t{++}, for instance,
1990 constructors for static and global objects are executed before
1991 @code{main} is called. It is therefore possible that the debugger stops
1992 before reaching the main procedure. However, the temporary breakpoint
1993 will remain to halt execution.
1995 Specify the arguments to give to your program as arguments to the
1996 @samp{start} command. These arguments will be given verbatim to the
1997 underlying @samp{run} command. Note that the same arguments will be
1998 reused if no argument is provided during subsequent calls to
1999 @samp{start} or @samp{run}.
2001 It is sometimes necessary to debug the program during elaboration. In
2002 these cases, using the @code{start} command would stop the execution of
2003 your program too late, as the program would have already completed the
2004 elaboration phase. Under these circumstances, insert breakpoints in your
2005 elaboration code before running your program.
2007 @kindex set exec-wrapper
2008 @item set exec-wrapper @var{wrapper}
2009 @itemx show exec-wrapper
2010 @itemx unset exec-wrapper
2011 When @samp{exec-wrapper} is set, the specified wrapper is used to
2012 launch programs for debugging. @value{GDBN} starts your program
2013 with a shell command of the form @kbd{exec @var{wrapper}
2014 @var{program}}. Quoting is added to @var{program} and its
2015 arguments, but not to @var{wrapper}, so you should add quotes if
2016 appropriate for your shell. The wrapper runs until it executes
2017 your program, and then @value{GDBN} takes control.
2019 You can use any program that eventually calls @code{execve} with
2020 its arguments as a wrapper. Several standard Unix utilities do
2021 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2022 with @code{exec "$@@"} will also work.
2024 For example, you can use @code{env} to pass an environment variable to
2025 the debugged program, without setting the variable in your shell's
2029 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2033 This command is available when debugging locally on most targets, excluding
2034 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2036 @kindex set disable-randomization
2037 @item set disable-randomization
2038 @itemx set disable-randomization on
2039 This option (enabled by default in @value{GDBN}) will turn off the native
2040 randomization of the virtual address space of the started program. This option
2041 is useful for multiple debugging sessions to make the execution better
2042 reproducible and memory addresses reusable across debugging sessions.
2044 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2048 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2051 @item set disable-randomization off
2052 Leave the behavior of the started executable unchanged. Some bugs rear their
2053 ugly heads only when the program is loaded at certain addresses. If your bug
2054 disappears when you run the program under @value{GDBN}, that might be because
2055 @value{GDBN} by default disables the address randomization on platforms, such
2056 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2057 disable-randomization off} to try to reproduce such elusive bugs.
2059 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2060 It protects the programs against some kinds of security attacks. In these
2061 cases the attacker needs to know the exact location of a concrete executable
2062 code. Randomizing its location makes it impossible to inject jumps misusing
2063 a code at its expected addresses.
2065 Prelinking shared libraries provides a startup performance advantage but it
2066 makes addresses in these libraries predictable for privileged processes by
2067 having just unprivileged access at the target system. Reading the shared
2068 library binary gives enough information for assembling the malicious code
2069 misusing it. Still even a prelinked shared library can get loaded at a new
2070 random address just requiring the regular relocation process during the
2071 startup. Shared libraries not already prelinked are always loaded at
2072 a randomly chosen address.
2074 Position independent executables (PIE) contain position independent code
2075 similar to the shared libraries and therefore such executables get loaded at
2076 a randomly chosen address upon startup. PIE executables always load even
2077 already prelinked shared libraries at a random address. You can build such
2078 executable using @command{gcc -fPIE -pie}.
2080 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2081 (as long as the randomization is enabled).
2083 @item show disable-randomization
2084 Show the current setting of the explicit disable of the native randomization of
2085 the virtual address space of the started program.
2090 @section Your Program's Arguments
2092 @cindex arguments (to your program)
2093 The arguments to your program can be specified by the arguments of the
2095 They are passed to a shell, which expands wildcard characters and
2096 performs redirection of I/O, and thence to your program. Your
2097 @code{SHELL} environment variable (if it exists) specifies what shell
2098 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2099 the default shell (@file{/bin/sh} on Unix).
2101 On non-Unix systems, the program is usually invoked directly by
2102 @value{GDBN}, which emulates I/O redirection via the appropriate system
2103 calls, and the wildcard characters are expanded by the startup code of
2104 the program, not by the shell.
2106 @code{run} with no arguments uses the same arguments used by the previous
2107 @code{run}, or those set by the @code{set args} command.
2112 Specify the arguments to be used the next time your program is run. If
2113 @code{set args} has no arguments, @code{run} executes your program
2114 with no arguments. Once you have run your program with arguments,
2115 using @code{set args} before the next @code{run} is the only way to run
2116 it again without arguments.
2120 Show the arguments to give your program when it is started.
2124 @section Your Program's Environment
2126 @cindex environment (of your program)
2127 The @dfn{environment} consists of a set of environment variables and
2128 their values. Environment variables conventionally record such things as
2129 your user name, your home directory, your terminal type, and your search
2130 path for programs to run. Usually you set up environment variables with
2131 the shell and they are inherited by all the other programs you run. When
2132 debugging, it can be useful to try running your program with a modified
2133 environment without having to start @value{GDBN} over again.
2137 @item path @var{directory}
2138 Add @var{directory} to the front of the @code{PATH} environment variable
2139 (the search path for executables) that will be passed to your program.
2140 The value of @code{PATH} used by @value{GDBN} does not change.
2141 You may specify several directory names, separated by whitespace or by a
2142 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2143 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2144 is moved to the front, so it is searched sooner.
2146 You can use the string @samp{$cwd} to refer to whatever is the current
2147 working directory at the time @value{GDBN} searches the path. If you
2148 use @samp{.} instead, it refers to the directory where you executed the
2149 @code{path} command. @value{GDBN} replaces @samp{.} in the
2150 @var{directory} argument (with the current path) before adding
2151 @var{directory} to the search path.
2152 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2153 @c document that, since repeating it would be a no-op.
2157 Display the list of search paths for executables (the @code{PATH}
2158 environment variable).
2160 @kindex show environment
2161 @item show environment @r{[}@var{varname}@r{]}
2162 Print the value of environment variable @var{varname} to be given to
2163 your program when it starts. If you do not supply @var{varname},
2164 print the names and values of all environment variables to be given to
2165 your program. You can abbreviate @code{environment} as @code{env}.
2167 @kindex set environment
2168 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2169 Set environment variable @var{varname} to @var{value}. The value
2170 changes for your program only, not for @value{GDBN} itself. @var{value} may
2171 be any string; the values of environment variables are just strings, and
2172 any interpretation is supplied by your program itself. The @var{value}
2173 parameter is optional; if it is eliminated, the variable is set to a
2175 @c "any string" here does not include leading, trailing
2176 @c blanks. Gnu asks: does anyone care?
2178 For example, this command:
2185 tells the debugged program, when subsequently run, that its user is named
2186 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2187 are not actually required.)
2189 @kindex unset environment
2190 @item unset environment @var{varname}
2191 Remove variable @var{varname} from the environment to be passed to your
2192 program. This is different from @samp{set env @var{varname} =};
2193 @code{unset environment} removes the variable from the environment,
2194 rather than assigning it an empty value.
2197 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2199 by your @code{SHELL} environment variable if it exists (or
2200 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2201 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2202 @file{.bashrc} for BASH---any variables you set in that file affect
2203 your program. You may wish to move setting of environment variables to
2204 files that are only run when you sign on, such as @file{.login} or
2207 @node Working Directory
2208 @section Your Program's Working Directory
2210 @cindex working directory (of your program)
2211 Each time you start your program with @code{run}, it inherits its
2212 working directory from the current working directory of @value{GDBN}.
2213 The @value{GDBN} working directory is initially whatever it inherited
2214 from its parent process (typically the shell), but you can specify a new
2215 working directory in @value{GDBN} with the @code{cd} command.
2217 The @value{GDBN} working directory also serves as a default for the commands
2218 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2223 @cindex change working directory
2224 @item cd @var{directory}
2225 Set the @value{GDBN} working directory to @var{directory}.
2229 Print the @value{GDBN} working directory.
2232 It is generally impossible to find the current working directory of
2233 the process being debugged (since a program can change its directory
2234 during its run). If you work on a system where @value{GDBN} is
2235 configured with the @file{/proc} support, you can use the @code{info
2236 proc} command (@pxref{SVR4 Process Information}) to find out the
2237 current working directory of the debuggee.
2240 @section Your Program's Input and Output
2245 By default, the program you run under @value{GDBN} does input and output to
2246 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2247 to its own terminal modes to interact with you, but it records the terminal
2248 modes your program was using and switches back to them when you continue
2249 running your program.
2252 @kindex info terminal
2254 Displays information recorded by @value{GDBN} about the terminal modes your
2258 You can redirect your program's input and/or output using shell
2259 redirection with the @code{run} command. For example,
2266 starts your program, diverting its output to the file @file{outfile}.
2269 @cindex controlling terminal
2270 Another way to specify where your program should do input and output is
2271 with the @code{tty} command. This command accepts a file name as
2272 argument, and causes this file to be the default for future @code{run}
2273 commands. It also resets the controlling terminal for the child
2274 process, for future @code{run} commands. For example,
2281 directs that processes started with subsequent @code{run} commands
2282 default to do input and output on the terminal @file{/dev/ttyb} and have
2283 that as their controlling terminal.
2285 An explicit redirection in @code{run} overrides the @code{tty} command's
2286 effect on the input/output device, but not its effect on the controlling
2289 When you use the @code{tty} command or redirect input in the @code{run}
2290 command, only the input @emph{for your program} is affected. The input
2291 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2292 for @code{set inferior-tty}.
2294 @cindex inferior tty
2295 @cindex set inferior controlling terminal
2296 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2297 display the name of the terminal that will be used for future runs of your
2301 @item set inferior-tty /dev/ttyb
2302 @kindex set inferior-tty
2303 Set the tty for the program being debugged to /dev/ttyb.
2305 @item show inferior-tty
2306 @kindex show inferior-tty
2307 Show the current tty for the program being debugged.
2311 @section Debugging an Already-running Process
2316 @item attach @var{process-id}
2317 This command attaches to a running process---one that was started
2318 outside @value{GDBN}. (@code{info files} shows your active
2319 targets.) The command takes as argument a process ID. The usual way to
2320 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2321 or with the @samp{jobs -l} shell command.
2323 @code{attach} does not repeat if you press @key{RET} a second time after
2324 executing the command.
2327 To use @code{attach}, your program must be running in an environment
2328 which supports processes; for example, @code{attach} does not work for
2329 programs on bare-board targets that lack an operating system. You must
2330 also have permission to send the process a signal.
2332 When you use @code{attach}, the debugger finds the program running in
2333 the process first by looking in the current working directory, then (if
2334 the program is not found) by using the source file search path
2335 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2336 the @code{file} command to load the program. @xref{Files, ,Commands to
2339 The first thing @value{GDBN} does after arranging to debug the specified
2340 process is to stop it. You can examine and modify an attached process
2341 with all the @value{GDBN} commands that are ordinarily available when
2342 you start processes with @code{run}. You can insert breakpoints; you
2343 can step and continue; you can modify storage. If you would rather the
2344 process continue running, you may use the @code{continue} command after
2345 attaching @value{GDBN} to the process.
2350 When you have finished debugging the attached process, you can use the
2351 @code{detach} command to release it from @value{GDBN} control. Detaching
2352 the process continues its execution. After the @code{detach} command,
2353 that process and @value{GDBN} become completely independent once more, and you
2354 are ready to @code{attach} another process or start one with @code{run}.
2355 @code{detach} does not repeat if you press @key{RET} again after
2356 executing the command.
2359 If you exit @value{GDBN} while you have an attached process, you detach
2360 that process. If you use the @code{run} command, you kill that process.
2361 By default, @value{GDBN} asks for confirmation if you try to do either of these
2362 things; you can control whether or not you need to confirm by using the
2363 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2367 @section Killing the Child Process
2372 Kill the child process in which your program is running under @value{GDBN}.
2375 This command is useful if you wish to debug a core dump instead of a
2376 running process. @value{GDBN} ignores any core dump file while your program
2379 On some operating systems, a program cannot be executed outside @value{GDBN}
2380 while you have breakpoints set on it inside @value{GDBN}. You can use the
2381 @code{kill} command in this situation to permit running your program
2382 outside the debugger.
2384 The @code{kill} command is also useful if you wish to recompile and
2385 relink your program, since on many systems it is impossible to modify an
2386 executable file while it is running in a process. In this case, when you
2387 next type @code{run}, @value{GDBN} notices that the file has changed, and
2388 reads the symbol table again (while trying to preserve your current
2389 breakpoint settings).
2391 @node Inferiors and Programs
2392 @section Debugging Multiple Inferiors and Programs
2394 @value{GDBN} lets you run and debug multiple programs in a single
2395 session. In addition, @value{GDBN} on some systems may let you run
2396 several programs simultaneously (otherwise you have to exit from one
2397 before starting another). In the most general case, you can have
2398 multiple threads of execution in each of multiple processes, launched
2399 from multiple executables.
2402 @value{GDBN} represents the state of each program execution with an
2403 object called an @dfn{inferior}. An inferior typically corresponds to
2404 a process, but is more general and applies also to targets that do not
2405 have processes. Inferiors may be created before a process runs, and
2406 may be retained after a process exits. Inferiors have unique
2407 identifiers that are different from process ids. Usually each
2408 inferior will also have its own distinct address space, although some
2409 embedded targets may have several inferiors running in different parts
2410 of a single address space. Each inferior may in turn have multiple
2411 threads running in it.
2413 To find out what inferiors exist at any moment, use @w{@code{info
2417 @kindex info inferiors
2418 @item info inferiors
2419 Print a list of all inferiors currently being managed by @value{GDBN}.
2421 @value{GDBN} displays for each inferior (in this order):
2425 the inferior number assigned by @value{GDBN}
2428 the target system's inferior identifier
2431 the name of the executable the inferior is running.
2436 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2437 indicates the current inferior.
2441 @c end table here to get a little more width for example
2444 (@value{GDBP}) info inferiors
2445 Num Description Executable
2446 2 process 2307 hello
2447 * 1 process 3401 goodbye
2450 To switch focus between inferiors, use the @code{inferior} command:
2453 @kindex inferior @var{infno}
2454 @item inferior @var{infno}
2455 Make inferior number @var{infno} the current inferior. The argument
2456 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2457 in the first field of the @samp{info inferiors} display.
2461 You can get multiple executables into a debugging session via the
2462 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2463 systems @value{GDBN} can add inferiors to the debug session
2464 automatically by following calls to @code{fork} and @code{exec}. To
2465 remove inferiors from the debugging session use the
2466 @w{@code{remove-inferiors}} command.
2469 @kindex add-inferior
2470 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2471 Adds @var{n} inferiors to be run using @var{executable} as the
2472 executable. @var{n} defaults to 1. If no executable is specified,
2473 the inferiors begins empty, with no program. You can still assign or
2474 change the program assigned to the inferior at any time by using the
2475 @code{file} command with the executable name as its argument.
2477 @kindex clone-inferior
2478 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2479 Adds @var{n} inferiors ready to execute the same program as inferior
2480 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2481 number of the current inferior. This is a convenient command when you
2482 want to run another instance of the inferior you are debugging.
2485 (@value{GDBP}) info inferiors
2486 Num Description Executable
2487 * 1 process 29964 helloworld
2488 (@value{GDBP}) clone-inferior
2491 (@value{GDBP}) info inferiors
2492 Num Description Executable
2494 * 1 process 29964 helloworld
2497 You can now simply switch focus to inferior 2 and run it.
2499 @kindex remove-inferiors
2500 @item remove-inferiors @var{infno}@dots{}
2501 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2502 possible to remove an inferior that is running with this command. For
2503 those, use the @code{kill} or @code{detach} command first.
2507 To quit debugging one of the running inferiors that is not the current
2508 inferior, you can either detach from it by using the @w{@code{detach
2509 inferior}} command (allowing it to run independently), or kill it
2510 using the @w{@code{kill inferiors}} command:
2513 @kindex detach inferiors @var{infno}@dots{}
2514 @item detach inferior @var{infno}@dots{}
2515 Detach from the inferior or inferiors identified by @value{GDBN}
2516 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2517 still stays on the list of inferiors shown by @code{info inferiors},
2518 but its Description will show @samp{<null>}.
2520 @kindex kill inferiors @var{infno}@dots{}
2521 @item kill inferiors @var{infno}@dots{}
2522 Kill the inferior or inferiors identified by @value{GDBN} inferior
2523 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2524 stays on the list of inferiors shown by @code{info inferiors}, but its
2525 Description will show @samp{<null>}.
2528 After the successful completion of a command such as @code{detach},
2529 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2530 a normal process exit, the inferior is still valid and listed with
2531 @code{info inferiors}, ready to be restarted.
2534 To be notified when inferiors are started or exit under @value{GDBN}'s
2535 control use @w{@code{set print inferior-events}}:
2538 @kindex set print inferior-events
2539 @cindex print messages on inferior start and exit
2540 @item set print inferior-events
2541 @itemx set print inferior-events on
2542 @itemx set print inferior-events off
2543 The @code{set print inferior-events} command allows you to enable or
2544 disable printing of messages when @value{GDBN} notices that new
2545 inferiors have started or that inferiors have exited or have been
2546 detached. By default, these messages will not be printed.
2548 @kindex show print inferior-events
2549 @item show print inferior-events
2550 Show whether messages will be printed when @value{GDBN} detects that
2551 inferiors have started, exited or have been detached.
2554 Many commands will work the same with multiple programs as with a
2555 single program: e.g., @code{print myglobal} will simply display the
2556 value of @code{myglobal} in the current inferior.
2559 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2560 get more info about the relationship of inferiors, programs, address
2561 spaces in a debug session. You can do that with the @w{@code{maint
2562 info program-spaces}} command.
2565 @kindex maint info program-spaces
2566 @item maint info program-spaces
2567 Print a list of all program spaces currently being managed by
2570 @value{GDBN} displays for each program space (in this order):
2574 the program space number assigned by @value{GDBN}
2577 the name of the executable loaded into the program space, with e.g.,
2578 the @code{file} command.
2583 An asterisk @samp{*} preceding the @value{GDBN} program space number
2584 indicates the current program space.
2586 In addition, below each program space line, @value{GDBN} prints extra
2587 information that isn't suitable to display in tabular form. For
2588 example, the list of inferiors bound to the program space.
2591 (@value{GDBP}) maint info program-spaces
2594 Bound inferiors: ID 1 (process 21561)
2598 Here we can see that no inferior is running the program @code{hello},
2599 while @code{process 21561} is running the program @code{goodbye}. On
2600 some targets, it is possible that multiple inferiors are bound to the
2601 same program space. The most common example is that of debugging both
2602 the parent and child processes of a @code{vfork} call. For example,
2605 (@value{GDBP}) maint info program-spaces
2608 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2611 Here, both inferior 2 and inferior 1 are running in the same program
2612 space as a result of inferior 1 having executed a @code{vfork} call.
2616 @section Debugging Programs with Multiple Threads
2618 @cindex threads of execution
2619 @cindex multiple threads
2620 @cindex switching threads
2621 In some operating systems, such as HP-UX and Solaris, a single program
2622 may have more than one @dfn{thread} of execution. The precise semantics
2623 of threads differ from one operating system to another, but in general
2624 the threads of a single program are akin to multiple processes---except
2625 that they share one address space (that is, they can all examine and
2626 modify the same variables). On the other hand, each thread has its own
2627 registers and execution stack, and perhaps private memory.
2629 @value{GDBN} provides these facilities for debugging multi-thread
2633 @item automatic notification of new threads
2634 @item @samp{thread @var{threadno}}, a command to switch among threads
2635 @item @samp{info threads}, a command to inquire about existing threads
2636 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2637 a command to apply a command to a list of threads
2638 @item thread-specific breakpoints
2639 @item @samp{set print thread-events}, which controls printing of
2640 messages on thread start and exit.
2641 @item @samp{set libthread-db-search-path @var{path}}, which lets
2642 the user specify which @code{libthread_db} to use if the default choice
2643 isn't compatible with the program.
2647 @emph{Warning:} These facilities are not yet available on every
2648 @value{GDBN} configuration where the operating system supports threads.
2649 If your @value{GDBN} does not support threads, these commands have no
2650 effect. For example, a system without thread support shows no output
2651 from @samp{info threads}, and always rejects the @code{thread} command,
2655 (@value{GDBP}) info threads
2656 (@value{GDBP}) thread 1
2657 Thread ID 1 not known. Use the "info threads" command to
2658 see the IDs of currently known threads.
2660 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2661 @c doesn't support threads"?
2664 @cindex focus of debugging
2665 @cindex current thread
2666 The @value{GDBN} thread debugging facility allows you to observe all
2667 threads while your program runs---but whenever @value{GDBN} takes
2668 control, one thread in particular is always the focus of debugging.
2669 This thread is called the @dfn{current thread}. Debugging commands show
2670 program information from the perspective of the current thread.
2672 @cindex @code{New} @var{systag} message
2673 @cindex thread identifier (system)
2674 @c FIXME-implementors!! It would be more helpful if the [New...] message
2675 @c included GDB's numeric thread handle, so you could just go to that
2676 @c thread without first checking `info threads'.
2677 Whenever @value{GDBN} detects a new thread in your program, it displays
2678 the target system's identification for the thread with a message in the
2679 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2680 whose form varies depending on the particular system. For example, on
2681 @sc{gnu}/Linux, you might see
2684 [New Thread 0x41e02940 (LWP 25582)]
2688 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2689 the @var{systag} is simply something like @samp{process 368}, with no
2692 @c FIXME!! (1) Does the [New...] message appear even for the very first
2693 @c thread of a program, or does it only appear for the
2694 @c second---i.e.@: when it becomes obvious we have a multithread
2696 @c (2) *Is* there necessarily a first thread always? Or do some
2697 @c multithread systems permit starting a program with multiple
2698 @c threads ab initio?
2700 @cindex thread number
2701 @cindex thread identifier (GDB)
2702 For debugging purposes, @value{GDBN} associates its own thread
2703 number---always a single integer---with each thread in your program.
2706 @kindex info threads
2707 @item info threads @r{[}@var{id}@dots{}@r{]}
2708 Display a summary of all threads currently in your program. Optional
2709 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2710 means to print information only about the specified thread or threads.
2711 @value{GDBN} displays for each thread (in this order):
2715 the thread number assigned by @value{GDBN}
2718 the target system's thread identifier (@var{systag})
2721 the thread's name, if one is known. A thread can either be named by
2722 the user (see @code{thread name}, below), or, in some cases, by the
2726 the current stack frame summary for that thread
2730 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2731 indicates the current thread.
2735 @c end table here to get a little more width for example
2738 (@value{GDBP}) info threads
2740 3 process 35 thread 27 0x34e5 in sigpause ()
2741 2 process 35 thread 23 0x34e5 in sigpause ()
2742 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2746 On Solaris, you can display more information about user threads with a
2747 Solaris-specific command:
2750 @item maint info sol-threads
2751 @kindex maint info sol-threads
2752 @cindex thread info (Solaris)
2753 Display info on Solaris user threads.
2757 @kindex thread @var{threadno}
2758 @item thread @var{threadno}
2759 Make thread number @var{threadno} the current thread. The command
2760 argument @var{threadno} is the internal @value{GDBN} thread number, as
2761 shown in the first field of the @samp{info threads} display.
2762 @value{GDBN} responds by displaying the system identifier of the thread
2763 you selected, and its current stack frame summary:
2766 (@value{GDBP}) thread 2
2767 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2768 #0 some_function (ignore=0x0) at example.c:8
2769 8 printf ("hello\n");
2773 As with the @samp{[New @dots{}]} message, the form of the text after
2774 @samp{Switching to} depends on your system's conventions for identifying
2777 @vindex $_thread@r{, convenience variable}
2778 The debugger convenience variable @samp{$_thread} contains the number
2779 of the current thread. You may find this useful in writing breakpoint
2780 conditional expressions, command scripts, and so forth. See
2781 @xref{Convenience Vars,, Convenience Variables}, for general
2782 information on convenience variables.
2784 @kindex thread apply
2785 @cindex apply command to several threads
2786 @item thread apply [@var{threadno} | all] @var{command}
2787 The @code{thread apply} command allows you to apply the named
2788 @var{command} to one or more threads. Specify the numbers of the
2789 threads that you want affected with the command argument
2790 @var{threadno}. It can be a single thread number, one of the numbers
2791 shown in the first field of the @samp{info threads} display; or it
2792 could be a range of thread numbers, as in @code{2-4}. To apply a
2793 command to all threads, type @kbd{thread apply all @var{command}}.
2796 @cindex name a thread
2797 @item thread name [@var{name}]
2798 This command assigns a name to the current thread. If no argument is
2799 given, any existing user-specified name is removed. The thread name
2800 appears in the @samp{info threads} display.
2802 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2803 determine the name of the thread as given by the OS. On these
2804 systems, a name specified with @samp{thread name} will override the
2805 system-give name, and removing the user-specified name will cause
2806 @value{GDBN} to once again display the system-specified name.
2809 @cindex search for a thread
2810 @item thread find [@var{regexp}]
2811 Search for and display thread ids whose name or @var{systag}
2812 matches the supplied regular expression.
2814 As well as being the complement to the @samp{thread name} command,
2815 this command also allows you to identify a thread by its target
2816 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2820 (@value{GDBN}) thread find 26688
2821 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2822 (@value{GDBN}) info thread 4
2824 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2827 @kindex set print thread-events
2828 @cindex print messages on thread start and exit
2829 @item set print thread-events
2830 @itemx set print thread-events on
2831 @itemx set print thread-events off
2832 The @code{set print thread-events} command allows you to enable or
2833 disable printing of messages when @value{GDBN} notices that new threads have
2834 started or that threads have exited. By default, these messages will
2835 be printed if detection of these events is supported by the target.
2836 Note that these messages cannot be disabled on all targets.
2838 @kindex show print thread-events
2839 @item show print thread-events
2840 Show whether messages will be printed when @value{GDBN} detects that threads
2841 have started and exited.
2844 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2845 more information about how @value{GDBN} behaves when you stop and start
2846 programs with multiple threads.
2848 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2849 watchpoints in programs with multiple threads.
2852 @kindex set libthread-db-search-path
2853 @cindex search path for @code{libthread_db}
2854 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2855 If this variable is set, @var{path} is a colon-separated list of
2856 directories @value{GDBN} will use to search for @code{libthread_db}.
2857 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2860 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2861 @code{libthread_db} library to obtain information about threads in the
2862 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2863 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2864 with default system shared library directories, and finally the directory
2865 from which @code{libpthread} was loaded in the inferior process.
2867 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2868 @value{GDBN} attempts to initialize it with the current inferior process.
2869 If this initialization fails (which could happen because of a version
2870 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2871 will unload @code{libthread_db}, and continue with the next directory.
2872 If none of @code{libthread_db} libraries initialize successfully,
2873 @value{GDBN} will issue a warning and thread debugging will be disabled.
2875 Setting @code{libthread-db-search-path} is currently implemented
2876 only on some platforms.
2878 @kindex show libthread-db-search-path
2879 @item show libthread-db-search-path
2880 Display current libthread_db search path.
2882 @kindex set debug libthread-db
2883 @kindex show debug libthread-db
2884 @cindex debugging @code{libthread_db}
2885 @item set debug libthread-db
2886 @itemx show debug libthread-db
2887 Turns on or off display of @code{libthread_db}-related events.
2888 Use @code{1} to enable, @code{0} to disable.
2892 @section Debugging Forks
2894 @cindex fork, debugging programs which call
2895 @cindex multiple processes
2896 @cindex processes, multiple
2897 On most systems, @value{GDBN} has no special support for debugging
2898 programs which create additional processes using the @code{fork}
2899 function. When a program forks, @value{GDBN} will continue to debug the
2900 parent process and the child process will run unimpeded. If you have
2901 set a breakpoint in any code which the child then executes, the child
2902 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2903 will cause it to terminate.
2905 However, if you want to debug the child process there is a workaround
2906 which isn't too painful. Put a call to @code{sleep} in the code which
2907 the child process executes after the fork. It may be useful to sleep
2908 only if a certain environment variable is set, or a certain file exists,
2909 so that the delay need not occur when you don't want to run @value{GDBN}
2910 on the child. While the child is sleeping, use the @code{ps} program to
2911 get its process ID. Then tell @value{GDBN} (a new invocation of
2912 @value{GDBN} if you are also debugging the parent process) to attach to
2913 the child process (@pxref{Attach}). From that point on you can debug
2914 the child process just like any other process which you attached to.
2916 On some systems, @value{GDBN} provides support for debugging programs that
2917 create additional processes using the @code{fork} or @code{vfork} functions.
2918 Currently, the only platforms with this feature are HP-UX (11.x and later
2919 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2921 By default, when a program forks, @value{GDBN} will continue to debug
2922 the parent process and the child process will run unimpeded.
2924 If you want to follow the child process instead of the parent process,
2925 use the command @w{@code{set follow-fork-mode}}.
2928 @kindex set follow-fork-mode
2929 @item set follow-fork-mode @var{mode}
2930 Set the debugger response to a program call of @code{fork} or
2931 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2932 process. The @var{mode} argument can be:
2936 The original process is debugged after a fork. The child process runs
2937 unimpeded. This is the default.
2940 The new process is debugged after a fork. The parent process runs
2945 @kindex show follow-fork-mode
2946 @item show follow-fork-mode
2947 Display the current debugger response to a @code{fork} or @code{vfork} call.
2950 @cindex debugging multiple processes
2951 On Linux, if you want to debug both the parent and child processes, use the
2952 command @w{@code{set detach-on-fork}}.
2955 @kindex set detach-on-fork
2956 @item set detach-on-fork @var{mode}
2957 Tells gdb whether to detach one of the processes after a fork, or
2958 retain debugger control over them both.
2962 The child process (or parent process, depending on the value of
2963 @code{follow-fork-mode}) will be detached and allowed to run
2964 independently. This is the default.
2967 Both processes will be held under the control of @value{GDBN}.
2968 One process (child or parent, depending on the value of
2969 @code{follow-fork-mode}) is debugged as usual, while the other
2974 @kindex show detach-on-fork
2975 @item show detach-on-fork
2976 Show whether detach-on-fork mode is on/off.
2979 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2980 will retain control of all forked processes (including nested forks).
2981 You can list the forked processes under the control of @value{GDBN} by
2982 using the @w{@code{info inferiors}} command, and switch from one fork
2983 to another by using the @code{inferior} command (@pxref{Inferiors and
2984 Programs, ,Debugging Multiple Inferiors and Programs}).
2986 To quit debugging one of the forked processes, you can either detach
2987 from it by using the @w{@code{detach inferiors}} command (allowing it
2988 to run independently), or kill it using the @w{@code{kill inferiors}}
2989 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2992 If you ask to debug a child process and a @code{vfork} is followed by an
2993 @code{exec}, @value{GDBN} executes the new target up to the first
2994 breakpoint in the new target. If you have a breakpoint set on
2995 @code{main} in your original program, the breakpoint will also be set on
2996 the child process's @code{main}.
2998 On some systems, when a child process is spawned by @code{vfork}, you
2999 cannot debug the child or parent until an @code{exec} call completes.
3001 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3002 call executes, the new target restarts. To restart the parent
3003 process, use the @code{file} command with the parent executable name
3004 as its argument. By default, after an @code{exec} call executes,
3005 @value{GDBN} discards the symbols of the previous executable image.
3006 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3010 @kindex set follow-exec-mode
3011 @item set follow-exec-mode @var{mode}
3013 Set debugger response to a program call of @code{exec}. An
3014 @code{exec} call replaces the program image of a process.
3016 @code{follow-exec-mode} can be:
3020 @value{GDBN} creates a new inferior and rebinds the process to this
3021 new inferior. The program the process was running before the
3022 @code{exec} call can be restarted afterwards by restarting the
3028 (@value{GDBP}) info inferiors
3030 Id Description Executable
3033 process 12020 is executing new program: prog2
3034 Program exited normally.
3035 (@value{GDBP}) info inferiors
3036 Id Description Executable
3042 @value{GDBN} keeps the process bound to the same inferior. The new
3043 executable image replaces the previous executable loaded in the
3044 inferior. Restarting the inferior after the @code{exec} call, with
3045 e.g., the @code{run} command, restarts the executable the process was
3046 running after the @code{exec} call. This is the default mode.
3051 (@value{GDBP}) info inferiors
3052 Id Description Executable
3055 process 12020 is executing new program: prog2
3056 Program exited normally.
3057 (@value{GDBP}) info inferiors
3058 Id Description Executable
3065 You can use the @code{catch} command to make @value{GDBN} stop whenever
3066 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3067 Catchpoints, ,Setting Catchpoints}.
3069 @node Checkpoint/Restart
3070 @section Setting a @emph{Bookmark} to Return to Later
3075 @cindex snapshot of a process
3076 @cindex rewind program state
3078 On certain operating systems@footnote{Currently, only
3079 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3080 program's state, called a @dfn{checkpoint}, and come back to it
3083 Returning to a checkpoint effectively undoes everything that has
3084 happened in the program since the @code{checkpoint} was saved. This
3085 includes changes in memory, registers, and even (within some limits)
3086 system state. Effectively, it is like going back in time to the
3087 moment when the checkpoint was saved.
3089 Thus, if you're stepping thru a program and you think you're
3090 getting close to the point where things go wrong, you can save
3091 a checkpoint. Then, if you accidentally go too far and miss
3092 the critical statement, instead of having to restart your program
3093 from the beginning, you can just go back to the checkpoint and
3094 start again from there.
3096 This can be especially useful if it takes a lot of time or
3097 steps to reach the point where you think the bug occurs.
3099 To use the @code{checkpoint}/@code{restart} method of debugging:
3104 Save a snapshot of the debugged program's current execution state.
3105 The @code{checkpoint} command takes no arguments, but each checkpoint
3106 is assigned a small integer id, similar to a breakpoint id.
3108 @kindex info checkpoints
3109 @item info checkpoints
3110 List the checkpoints that have been saved in the current debugging
3111 session. For each checkpoint, the following information will be
3118 @item Source line, or label
3121 @kindex restart @var{checkpoint-id}
3122 @item restart @var{checkpoint-id}
3123 Restore the program state that was saved as checkpoint number
3124 @var{checkpoint-id}. All program variables, registers, stack frames
3125 etc.@: will be returned to the values that they had when the checkpoint
3126 was saved. In essence, gdb will ``wind back the clock'' to the point
3127 in time when the checkpoint was saved.
3129 Note that breakpoints, @value{GDBN} variables, command history etc.
3130 are not affected by restoring a checkpoint. In general, a checkpoint
3131 only restores things that reside in the program being debugged, not in
3134 @kindex delete checkpoint @var{checkpoint-id}
3135 @item delete checkpoint @var{checkpoint-id}
3136 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3140 Returning to a previously saved checkpoint will restore the user state
3141 of the program being debugged, plus a significant subset of the system
3142 (OS) state, including file pointers. It won't ``un-write'' data from
3143 a file, but it will rewind the file pointer to the previous location,
3144 so that the previously written data can be overwritten. For files
3145 opened in read mode, the pointer will also be restored so that the
3146 previously read data can be read again.
3148 Of course, characters that have been sent to a printer (or other
3149 external device) cannot be ``snatched back'', and characters received
3150 from eg.@: a serial device can be removed from internal program buffers,
3151 but they cannot be ``pushed back'' into the serial pipeline, ready to
3152 be received again. Similarly, the actual contents of files that have
3153 been changed cannot be restored (at this time).
3155 However, within those constraints, you actually can ``rewind'' your
3156 program to a previously saved point in time, and begin debugging it
3157 again --- and you can change the course of events so as to debug a
3158 different execution path this time.
3160 @cindex checkpoints and process id
3161 Finally, there is one bit of internal program state that will be
3162 different when you return to a checkpoint --- the program's process
3163 id. Each checkpoint will have a unique process id (or @var{pid}),
3164 and each will be different from the program's original @var{pid}.
3165 If your program has saved a local copy of its process id, this could
3166 potentially pose a problem.
3168 @subsection A Non-obvious Benefit of Using Checkpoints
3170 On some systems such as @sc{gnu}/Linux, address space randomization
3171 is performed on new processes for security reasons. This makes it
3172 difficult or impossible to set a breakpoint, or watchpoint, on an
3173 absolute address if you have to restart the program, since the
3174 absolute location of a symbol will change from one execution to the
3177 A checkpoint, however, is an @emph{identical} copy of a process.
3178 Therefore if you create a checkpoint at (eg.@:) the start of main,
3179 and simply return to that checkpoint instead of restarting the
3180 process, you can avoid the effects of address randomization and
3181 your symbols will all stay in the same place.
3184 @chapter Stopping and Continuing
3186 The principal purposes of using a debugger are so that you can stop your
3187 program before it terminates; or so that, if your program runs into
3188 trouble, you can investigate and find out why.
3190 Inside @value{GDBN}, your program may stop for any of several reasons,
3191 such as a signal, a breakpoint, or reaching a new line after a
3192 @value{GDBN} command such as @code{step}. You may then examine and
3193 change variables, set new breakpoints or remove old ones, and then
3194 continue execution. Usually, the messages shown by @value{GDBN} provide
3195 ample explanation of the status of your program---but you can also
3196 explicitly request this information at any time.
3199 @kindex info program
3201 Display information about the status of your program: whether it is
3202 running or not, what process it is, and why it stopped.
3206 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3207 * Continuing and Stepping:: Resuming execution
3209 * Thread Stops:: Stopping and starting multi-thread programs
3213 @section Breakpoints, Watchpoints, and Catchpoints
3216 A @dfn{breakpoint} makes your program stop whenever a certain point in
3217 the program is reached. For each breakpoint, you can add conditions to
3218 control in finer detail whether your program stops. You can set
3219 breakpoints with the @code{break} command and its variants (@pxref{Set
3220 Breaks, ,Setting Breakpoints}), to specify the place where your program
3221 should stop by line number, function name or exact address in the
3224 On some systems, you can set breakpoints in shared libraries before
3225 the executable is run. There is a minor limitation on HP-UX systems:
3226 you must wait until the executable is run in order to set breakpoints
3227 in shared library routines that are not called directly by the program
3228 (for example, routines that are arguments in a @code{pthread_create}
3232 @cindex data breakpoints
3233 @cindex memory tracing
3234 @cindex breakpoint on memory address
3235 @cindex breakpoint on variable modification
3236 A @dfn{watchpoint} is a special breakpoint that stops your program
3237 when the value of an expression changes. The expression may be a value
3238 of a variable, or it could involve values of one or more variables
3239 combined by operators, such as @samp{a + b}. This is sometimes called
3240 @dfn{data breakpoints}. You must use a different command to set
3241 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3242 from that, you can manage a watchpoint like any other breakpoint: you
3243 enable, disable, and delete both breakpoints and watchpoints using the
3246 You can arrange to have values from your program displayed automatically
3247 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3251 @cindex breakpoint on events
3252 A @dfn{catchpoint} is another special breakpoint that stops your program
3253 when a certain kind of event occurs, such as the throwing of a C@t{++}
3254 exception or the loading of a library. As with watchpoints, you use a
3255 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3256 Catchpoints}), but aside from that, you can manage a catchpoint like any
3257 other breakpoint. (To stop when your program receives a signal, use the
3258 @code{handle} command; see @ref{Signals, ,Signals}.)
3260 @cindex breakpoint numbers
3261 @cindex numbers for breakpoints
3262 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3263 catchpoint when you create it; these numbers are successive integers
3264 starting with one. In many of the commands for controlling various
3265 features of breakpoints you use the breakpoint number to say which
3266 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3267 @dfn{disabled}; if disabled, it has no effect on your program until you
3270 @cindex breakpoint ranges
3271 @cindex ranges of breakpoints
3272 Some @value{GDBN} commands accept a range of breakpoints on which to
3273 operate. A breakpoint range is either a single breakpoint number, like
3274 @samp{5}, or two such numbers, in increasing order, separated by a
3275 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3276 all breakpoints in that range are operated on.
3279 * Set Breaks:: Setting breakpoints
3280 * Set Watchpoints:: Setting watchpoints
3281 * Set Catchpoints:: Setting catchpoints
3282 * Delete Breaks:: Deleting breakpoints
3283 * Disabling:: Disabling breakpoints
3284 * Conditions:: Break conditions
3285 * Break Commands:: Breakpoint command lists
3286 * Save Breakpoints:: How to save breakpoints in a file
3287 * Error in Breakpoints:: ``Cannot insert breakpoints''
3288 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3292 @subsection Setting Breakpoints
3294 @c FIXME LMB what does GDB do if no code on line of breakpt?
3295 @c consider in particular declaration with/without initialization.
3297 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3300 @kindex b @r{(@code{break})}
3301 @vindex $bpnum@r{, convenience variable}
3302 @cindex latest breakpoint
3303 Breakpoints are set with the @code{break} command (abbreviated
3304 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3305 number of the breakpoint you've set most recently; see @ref{Convenience
3306 Vars,, Convenience Variables}, for a discussion of what you can do with
3307 convenience variables.
3310 @item break @var{location}
3311 Set a breakpoint at the given @var{location}, which can specify a
3312 function name, a line number, or an address of an instruction.
3313 (@xref{Specify Location}, for a list of all the possible ways to
3314 specify a @var{location}.) The breakpoint will stop your program just
3315 before it executes any of the code in the specified @var{location}.
3317 When using source languages that permit overloading of symbols, such as
3318 C@t{++}, a function name may refer to more than one possible place to break.
3319 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3322 It is also possible to insert a breakpoint that will stop the program
3323 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3324 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3327 When called without any arguments, @code{break} sets a breakpoint at
3328 the next instruction to be executed in the selected stack frame
3329 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3330 innermost, this makes your program stop as soon as control
3331 returns to that frame. This is similar to the effect of a
3332 @code{finish} command in the frame inside the selected frame---except
3333 that @code{finish} does not leave an active breakpoint. If you use
3334 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3335 the next time it reaches the current location; this may be useful
3338 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3339 least one instruction has been executed. If it did not do this, you
3340 would be unable to proceed past a breakpoint without first disabling the
3341 breakpoint. This rule applies whether or not the breakpoint already
3342 existed when your program stopped.
3344 @item break @dots{} if @var{cond}
3345 Set a breakpoint with condition @var{cond}; evaluate the expression
3346 @var{cond} each time the breakpoint is reached, and stop only if the
3347 value is nonzero---that is, if @var{cond} evaluates as true.
3348 @samp{@dots{}} stands for one of the possible arguments described
3349 above (or no argument) specifying where to break. @xref{Conditions,
3350 ,Break Conditions}, for more information on breakpoint conditions.
3353 @item tbreak @var{args}
3354 Set a breakpoint enabled only for one stop. @var{args} are the
3355 same as for the @code{break} command, and the breakpoint is set in the same
3356 way, but the breakpoint is automatically deleted after the first time your
3357 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3360 @cindex hardware breakpoints
3361 @item hbreak @var{args}
3362 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3363 @code{break} command and the breakpoint is set in the same way, but the
3364 breakpoint requires hardware support and some target hardware may not
3365 have this support. The main purpose of this is EPROM/ROM code
3366 debugging, so you can set a breakpoint at an instruction without
3367 changing the instruction. This can be used with the new trap-generation
3368 provided by SPARClite DSU and most x86-based targets. These targets
3369 will generate traps when a program accesses some data or instruction
3370 address that is assigned to the debug registers. However the hardware
3371 breakpoint registers can take a limited number of breakpoints. For
3372 example, on the DSU, only two data breakpoints can be set at a time, and
3373 @value{GDBN} will reject this command if more than two are used. Delete
3374 or disable unused hardware breakpoints before setting new ones
3375 (@pxref{Disabling, ,Disabling Breakpoints}).
3376 @xref{Conditions, ,Break Conditions}.
3377 For remote targets, you can restrict the number of hardware
3378 breakpoints @value{GDBN} will use, see @ref{set remote
3379 hardware-breakpoint-limit}.
3382 @item thbreak @var{args}
3383 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3384 are the same as for the @code{hbreak} command and the breakpoint is set in
3385 the same way. However, like the @code{tbreak} command,
3386 the breakpoint is automatically deleted after the
3387 first time your program stops there. Also, like the @code{hbreak}
3388 command, the breakpoint requires hardware support and some target hardware
3389 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3390 See also @ref{Conditions, ,Break Conditions}.
3393 @cindex regular expression
3394 @cindex breakpoints at functions matching a regexp
3395 @cindex set breakpoints in many functions
3396 @item rbreak @var{regex}
3397 Set breakpoints on all functions matching the regular expression
3398 @var{regex}. This command sets an unconditional breakpoint on all
3399 matches, printing a list of all breakpoints it set. Once these
3400 breakpoints are set, they are treated just like the breakpoints set with
3401 the @code{break} command. You can delete them, disable them, or make
3402 them conditional the same way as any other breakpoint.
3404 The syntax of the regular expression is the standard one used with tools
3405 like @file{grep}. Note that this is different from the syntax used by
3406 shells, so for instance @code{foo*} matches all functions that include
3407 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3408 @code{.*} leading and trailing the regular expression you supply, so to
3409 match only functions that begin with @code{foo}, use @code{^foo}.
3411 @cindex non-member C@t{++} functions, set breakpoint in
3412 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3413 breakpoints on overloaded functions that are not members of any special
3416 @cindex set breakpoints on all functions
3417 The @code{rbreak} command can be used to set breakpoints in
3418 @strong{all} the functions in a program, like this:
3421 (@value{GDBP}) rbreak .
3424 @item rbreak @var{file}:@var{regex}
3425 If @code{rbreak} is called with a filename qualification, it limits
3426 the search for functions matching the given regular expression to the
3427 specified @var{file}. This can be used, for example, to set breakpoints on
3428 every function in a given file:
3431 (@value{GDBP}) rbreak file.c:.
3434 The colon separating the filename qualifier from the regex may
3435 optionally be surrounded by spaces.
3437 @kindex info breakpoints
3438 @cindex @code{$_} and @code{info breakpoints}
3439 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3440 @itemx info break @r{[}@var{n}@dots{}@r{]}
3441 Print a table of all breakpoints, watchpoints, and catchpoints set and
3442 not deleted. Optional argument @var{n} means print information only
3443 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3444 For each breakpoint, following columns are printed:
3447 @item Breakpoint Numbers
3449 Breakpoint, watchpoint, or catchpoint.
3451 Whether the breakpoint is marked to be disabled or deleted when hit.
3452 @item Enabled or Disabled
3453 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3454 that are not enabled.
3456 Where the breakpoint is in your program, as a memory address. For a
3457 pending breakpoint whose address is not yet known, this field will
3458 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3459 library that has the symbol or line referred by breakpoint is loaded.
3460 See below for details. A breakpoint with several locations will
3461 have @samp{<MULTIPLE>} in this field---see below for details.
3463 Where the breakpoint is in the source for your program, as a file and
3464 line number. For a pending breakpoint, the original string passed to
3465 the breakpoint command will be listed as it cannot be resolved until
3466 the appropriate shared library is loaded in the future.
3470 If a breakpoint is conditional, @code{info break} shows the condition on
3471 the line following the affected breakpoint; breakpoint commands, if any,
3472 are listed after that. A pending breakpoint is allowed to have a condition
3473 specified for it. The condition is not parsed for validity until a shared
3474 library is loaded that allows the pending breakpoint to resolve to a
3478 @code{info break} with a breakpoint
3479 number @var{n} as argument lists only that breakpoint. The
3480 convenience variable @code{$_} and the default examining-address for
3481 the @code{x} command are set to the address of the last breakpoint
3482 listed (@pxref{Memory, ,Examining Memory}).
3485 @code{info break} displays a count of the number of times the breakpoint
3486 has been hit. This is especially useful in conjunction with the
3487 @code{ignore} command. You can ignore a large number of breakpoint
3488 hits, look at the breakpoint info to see how many times the breakpoint
3489 was hit, and then run again, ignoring one less than that number. This
3490 will get you quickly to the last hit of that breakpoint.
3493 @value{GDBN} allows you to set any number of breakpoints at the same place in
3494 your program. There is nothing silly or meaningless about this. When
3495 the breakpoints are conditional, this is even useful
3496 (@pxref{Conditions, ,Break Conditions}).
3498 @cindex multiple locations, breakpoints
3499 @cindex breakpoints, multiple locations
3500 It is possible that a breakpoint corresponds to several locations
3501 in your program. Examples of this situation are:
3505 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3506 instances of the function body, used in different cases.
3509 For a C@t{++} template function, a given line in the function can
3510 correspond to any number of instantiations.
3513 For an inlined function, a given source line can correspond to
3514 several places where that function is inlined.
3517 In all those cases, @value{GDBN} will insert a breakpoint at all
3518 the relevant locations@footnote{
3519 As of this writing, multiple-location breakpoints work only if there's
3520 line number information for all the locations. This means that they
3521 will generally not work in system libraries, unless you have debug
3522 info with line numbers for them.}.
3524 A breakpoint with multiple locations is displayed in the breakpoint
3525 table using several rows---one header row, followed by one row for
3526 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3527 address column. The rows for individual locations contain the actual
3528 addresses for locations, and show the functions to which those
3529 locations belong. The number column for a location is of the form
3530 @var{breakpoint-number}.@var{location-number}.
3535 Num Type Disp Enb Address What
3536 1 breakpoint keep y <MULTIPLE>
3538 breakpoint already hit 1 time
3539 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3540 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3543 Each location can be individually enabled or disabled by passing
3544 @var{breakpoint-number}.@var{location-number} as argument to the
3545 @code{enable} and @code{disable} commands. Note that you cannot
3546 delete the individual locations from the list, you can only delete the
3547 entire list of locations that belong to their parent breakpoint (with
3548 the @kbd{delete @var{num}} command, where @var{num} is the number of
3549 the parent breakpoint, 1 in the above example). Disabling or enabling
3550 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3551 that belong to that breakpoint.
3553 @cindex pending breakpoints
3554 It's quite common to have a breakpoint inside a shared library.
3555 Shared libraries can be loaded and unloaded explicitly,
3556 and possibly repeatedly, as the program is executed. To support
3557 this use case, @value{GDBN} updates breakpoint locations whenever
3558 any shared library is loaded or unloaded. Typically, you would
3559 set a breakpoint in a shared library at the beginning of your
3560 debugging session, when the library is not loaded, and when the
3561 symbols from the library are not available. When you try to set
3562 breakpoint, @value{GDBN} will ask you if you want to set
3563 a so called @dfn{pending breakpoint}---breakpoint whose address
3564 is not yet resolved.
3566 After the program is run, whenever a new shared library is loaded,
3567 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3568 shared library contains the symbol or line referred to by some
3569 pending breakpoint, that breakpoint is resolved and becomes an
3570 ordinary breakpoint. When a library is unloaded, all breakpoints
3571 that refer to its symbols or source lines become pending again.
3573 This logic works for breakpoints with multiple locations, too. For
3574 example, if you have a breakpoint in a C@t{++} template function, and
3575 a newly loaded shared library has an instantiation of that template,
3576 a new location is added to the list of locations for the breakpoint.
3578 Except for having unresolved address, pending breakpoints do not
3579 differ from regular breakpoints. You can set conditions or commands,
3580 enable and disable them and perform other breakpoint operations.
3582 @value{GDBN} provides some additional commands for controlling what
3583 happens when the @samp{break} command cannot resolve breakpoint
3584 address specification to an address:
3586 @kindex set breakpoint pending
3587 @kindex show breakpoint pending
3589 @item set breakpoint pending auto
3590 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3591 location, it queries you whether a pending breakpoint should be created.
3593 @item set breakpoint pending on
3594 This indicates that an unrecognized breakpoint location should automatically
3595 result in a pending breakpoint being created.
3597 @item set breakpoint pending off
3598 This indicates that pending breakpoints are not to be created. Any
3599 unrecognized breakpoint location results in an error. This setting does
3600 not affect any pending breakpoints previously created.
3602 @item show breakpoint pending
3603 Show the current behavior setting for creating pending breakpoints.
3606 The settings above only affect the @code{break} command and its
3607 variants. Once breakpoint is set, it will be automatically updated
3608 as shared libraries are loaded and unloaded.
3610 @cindex automatic hardware breakpoints
3611 For some targets, @value{GDBN} can automatically decide if hardware or
3612 software breakpoints should be used, depending on whether the
3613 breakpoint address is read-only or read-write. This applies to
3614 breakpoints set with the @code{break} command as well as to internal
3615 breakpoints set by commands like @code{next} and @code{finish}. For
3616 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3619 You can control this automatic behaviour with the following commands::
3621 @kindex set breakpoint auto-hw
3622 @kindex show breakpoint auto-hw
3624 @item set breakpoint auto-hw on
3625 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3626 will try to use the target memory map to decide if software or hardware
3627 breakpoint must be used.
3629 @item set breakpoint auto-hw off
3630 This indicates @value{GDBN} should not automatically select breakpoint
3631 type. If the target provides a memory map, @value{GDBN} will warn when
3632 trying to set software breakpoint at a read-only address.
3635 @value{GDBN} normally implements breakpoints by replacing the program code
3636 at the breakpoint address with a special instruction, which, when
3637 executed, given control to the debugger. By default, the program
3638 code is so modified only when the program is resumed. As soon as
3639 the program stops, @value{GDBN} restores the original instructions. This
3640 behaviour guards against leaving breakpoints inserted in the
3641 target should gdb abrubptly disconnect. However, with slow remote
3642 targets, inserting and removing breakpoint can reduce the performance.
3643 This behavior can be controlled with the following commands::
3645 @kindex set breakpoint always-inserted
3646 @kindex show breakpoint always-inserted
3648 @item set breakpoint always-inserted off
3649 All breakpoints, including newly added by the user, are inserted in
3650 the target only when the target is resumed. All breakpoints are
3651 removed from the target when it stops.
3653 @item set breakpoint always-inserted on
3654 Causes all breakpoints to be inserted in the target at all times. If
3655 the user adds a new breakpoint, or changes an existing breakpoint, the
3656 breakpoints in the target are updated immediately. A breakpoint is
3657 removed from the target only when breakpoint itself is removed.
3659 @cindex non-stop mode, and @code{breakpoint always-inserted}
3660 @item set breakpoint always-inserted auto
3661 This is the default mode. If @value{GDBN} is controlling the inferior
3662 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3663 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3664 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3665 @code{breakpoint always-inserted} mode is off.
3668 @cindex negative breakpoint numbers
3669 @cindex internal @value{GDBN} breakpoints
3670 @value{GDBN} itself sometimes sets breakpoints in your program for
3671 special purposes, such as proper handling of @code{longjmp} (in C
3672 programs). These internal breakpoints are assigned negative numbers,
3673 starting with @code{-1}; @samp{info breakpoints} does not display them.
3674 You can see these breakpoints with the @value{GDBN} maintenance command
3675 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3678 @node Set Watchpoints
3679 @subsection Setting Watchpoints
3681 @cindex setting watchpoints
3682 You can use a watchpoint to stop execution whenever the value of an
3683 expression changes, without having to predict a particular place where
3684 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3685 The expression may be as simple as the value of a single variable, or
3686 as complex as many variables combined by operators. Examples include:
3690 A reference to the value of a single variable.
3693 An address cast to an appropriate data type. For example,
3694 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3695 address (assuming an @code{int} occupies 4 bytes).
3698 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3699 expression can use any operators valid in the program's native
3700 language (@pxref{Languages}).
3703 You can set a watchpoint on an expression even if the expression can
3704 not be evaluated yet. For instance, you can set a watchpoint on
3705 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3706 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3707 the expression produces a valid value. If the expression becomes
3708 valid in some other way than changing a variable (e.g.@: if the memory
3709 pointed to by @samp{*global_ptr} becomes readable as the result of a
3710 @code{malloc} call), @value{GDBN} may not stop until the next time
3711 the expression changes.
3713 @cindex software watchpoints
3714 @cindex hardware watchpoints
3715 Depending on your system, watchpoints may be implemented in software or
3716 hardware. @value{GDBN} does software watchpointing by single-stepping your
3717 program and testing the variable's value each time, which is hundreds of
3718 times slower than normal execution. (But this may still be worth it, to
3719 catch errors where you have no clue what part of your program is the
3722 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3723 x86-based targets, @value{GDBN} includes support for hardware
3724 watchpoints, which do not slow down the running of your program.
3728 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3729 Set a watchpoint for an expression. @value{GDBN} will break when the
3730 expression @var{expr} is written into by the program and its value
3731 changes. The simplest (and the most popular) use of this command is
3732 to watch the value of a single variable:
3735 (@value{GDBP}) watch foo
3738 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3739 argument, @value{GDBN} breaks only when the thread identified by
3740 @var{threadnum} changes the value of @var{expr}. If any other threads
3741 change the value of @var{expr}, @value{GDBN} will not break. Note
3742 that watchpoints restricted to a single thread in this way only work
3743 with Hardware Watchpoints.
3745 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3746 (see below). The @code{-location} argument tells @value{GDBN} to
3747 instead watch the memory referred to by @var{expr}. In this case,
3748 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3749 and watch the memory at that address. The type of the result is used
3750 to determine the size of the watched memory. If the expression's
3751 result does not have an address, then @value{GDBN} will print an
3754 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3755 of masked watchpoints, if the current architecture supports this
3756 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3757 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3758 to an address to watch. The mask specifies that some bits of an address
3759 (the bits which are reset in the mask) should be ignored when matching
3760 the address accessed by the inferior against the watchpoint address.
3761 Thus, a masked watchpoint watches many addresses simultaneously---those
3762 addresses whose unmasked bits are identical to the unmasked bits in the
3763 watchpoint address. The @code{mask} argument implies @code{-location}.
3767 (@value{GDBP}) watch foo mask 0xffff00ff
3768 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3772 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3773 Set a watchpoint that will break when the value of @var{expr} is read
3777 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3778 Set a watchpoint that will break when @var{expr} is either read from
3779 or written into by the program.
3781 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3782 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3783 This command prints a list of watchpoints, using the same format as
3784 @code{info break} (@pxref{Set Breaks}).
3787 If you watch for a change in a numerically entered address you need to
3788 dereference it, as the address itself is just a constant number which will
3789 never change. @value{GDBN} refuses to create a watchpoint that watches
3790 a never-changing value:
3793 (@value{GDBP}) watch 0x600850
3794 Cannot watch constant value 0x600850.
3795 (@value{GDBP}) watch *(int *) 0x600850
3796 Watchpoint 1: *(int *) 6293584
3799 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3800 watchpoints execute very quickly, and the debugger reports a change in
3801 value at the exact instruction where the change occurs. If @value{GDBN}
3802 cannot set a hardware watchpoint, it sets a software watchpoint, which
3803 executes more slowly and reports the change in value at the next
3804 @emph{statement}, not the instruction, after the change occurs.
3806 @cindex use only software watchpoints
3807 You can force @value{GDBN} to use only software watchpoints with the
3808 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3809 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3810 the underlying system supports them. (Note that hardware-assisted
3811 watchpoints that were set @emph{before} setting
3812 @code{can-use-hw-watchpoints} to zero will still use the hardware
3813 mechanism of watching expression values.)
3816 @item set can-use-hw-watchpoints
3817 @kindex set can-use-hw-watchpoints
3818 Set whether or not to use hardware watchpoints.
3820 @item show can-use-hw-watchpoints
3821 @kindex show can-use-hw-watchpoints
3822 Show the current mode of using hardware watchpoints.
3825 For remote targets, you can restrict the number of hardware
3826 watchpoints @value{GDBN} will use, see @ref{set remote
3827 hardware-breakpoint-limit}.
3829 When you issue the @code{watch} command, @value{GDBN} reports
3832 Hardware watchpoint @var{num}: @var{expr}
3836 if it was able to set a hardware watchpoint.
3838 Currently, the @code{awatch} and @code{rwatch} commands can only set
3839 hardware watchpoints, because accesses to data that don't change the
3840 value of the watched expression cannot be detected without examining
3841 every instruction as it is being executed, and @value{GDBN} does not do
3842 that currently. If @value{GDBN} finds that it is unable to set a
3843 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3844 will print a message like this:
3847 Expression cannot be implemented with read/access watchpoint.
3850 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3851 data type of the watched expression is wider than what a hardware
3852 watchpoint on the target machine can handle. For example, some systems
3853 can only watch regions that are up to 4 bytes wide; on such systems you
3854 cannot set hardware watchpoints for an expression that yields a
3855 double-precision floating-point number (which is typically 8 bytes
3856 wide). As a work-around, it might be possible to break the large region
3857 into a series of smaller ones and watch them with separate watchpoints.
3859 If you set too many hardware watchpoints, @value{GDBN} might be unable
3860 to insert all of them when you resume the execution of your program.
3861 Since the precise number of active watchpoints is unknown until such
3862 time as the program is about to be resumed, @value{GDBN} might not be
3863 able to warn you about this when you set the watchpoints, and the
3864 warning will be printed only when the program is resumed:
3867 Hardware watchpoint @var{num}: Could not insert watchpoint
3871 If this happens, delete or disable some of the watchpoints.
3873 Watching complex expressions that reference many variables can also
3874 exhaust the resources available for hardware-assisted watchpoints.
3875 That's because @value{GDBN} needs to watch every variable in the
3876 expression with separately allocated resources.
3878 If you call a function interactively using @code{print} or @code{call},
3879 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3880 kind of breakpoint or the call completes.
3882 @value{GDBN} automatically deletes watchpoints that watch local
3883 (automatic) variables, or expressions that involve such variables, when
3884 they go out of scope, that is, when the execution leaves the block in
3885 which these variables were defined. In particular, when the program
3886 being debugged terminates, @emph{all} local variables go out of scope,
3887 and so only watchpoints that watch global variables remain set. If you
3888 rerun the program, you will need to set all such watchpoints again. One
3889 way of doing that would be to set a code breakpoint at the entry to the
3890 @code{main} function and when it breaks, set all the watchpoints.
3892 @cindex watchpoints and threads
3893 @cindex threads and watchpoints
3894 In multi-threaded programs, watchpoints will detect changes to the
3895 watched expression from every thread.
3898 @emph{Warning:} In multi-threaded programs, software watchpoints
3899 have only limited usefulness. If @value{GDBN} creates a software
3900 watchpoint, it can only watch the value of an expression @emph{in a
3901 single thread}. If you are confident that the expression can only
3902 change due to the current thread's activity (and if you are also
3903 confident that no other thread can become current), then you can use
3904 software watchpoints as usual. However, @value{GDBN} may not notice
3905 when a non-current thread's activity changes the expression. (Hardware
3906 watchpoints, in contrast, watch an expression in all threads.)
3909 @xref{set remote hardware-watchpoint-limit}.
3911 @node Set Catchpoints
3912 @subsection Setting Catchpoints
3913 @cindex catchpoints, setting
3914 @cindex exception handlers
3915 @cindex event handling
3917 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3918 kinds of program events, such as C@t{++} exceptions or the loading of a
3919 shared library. Use the @code{catch} command to set a catchpoint.
3923 @item catch @var{event}
3924 Stop when @var{event} occurs. @var{event} can be any of the following:
3927 @cindex stop on C@t{++} exceptions
3928 The throwing of a C@t{++} exception.
3931 The catching of a C@t{++} exception.
3934 @cindex Ada exception catching
3935 @cindex catch Ada exceptions
3936 An Ada exception being raised. If an exception name is specified
3937 at the end of the command (eg @code{catch exception Program_Error}),
3938 the debugger will stop only when this specific exception is raised.
3939 Otherwise, the debugger stops execution when any Ada exception is raised.
3941 When inserting an exception catchpoint on a user-defined exception whose
3942 name is identical to one of the exceptions defined by the language, the
3943 fully qualified name must be used as the exception name. Otherwise,
3944 @value{GDBN} will assume that it should stop on the pre-defined exception
3945 rather than the user-defined one. For instance, assuming an exception
3946 called @code{Constraint_Error} is defined in package @code{Pck}, then
3947 the command to use to catch such exceptions is @kbd{catch exception
3948 Pck.Constraint_Error}.
3950 @item exception unhandled
3951 An exception that was raised but is not handled by the program.
3954 A failed Ada assertion.
3957 @cindex break on fork/exec
3958 A call to @code{exec}. This is currently only available for HP-UX
3962 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3963 @cindex break on a system call.
3964 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3965 syscall is a mechanism for application programs to request a service
3966 from the operating system (OS) or one of the OS system services.
3967 @value{GDBN} can catch some or all of the syscalls issued by the
3968 debuggee, and show the related information for each syscall. If no
3969 argument is specified, calls to and returns from all system calls
3972 @var{name} can be any system call name that is valid for the
3973 underlying OS. Just what syscalls are valid depends on the OS. On
3974 GNU and Unix systems, you can find the full list of valid syscall
3975 names on @file{/usr/include/asm/unistd.h}.
3977 @c For MS-Windows, the syscall names and the corresponding numbers
3978 @c can be found, e.g., on this URL:
3979 @c http://www.metasploit.com/users/opcode/syscalls.html
3980 @c but we don't support Windows syscalls yet.
3982 Normally, @value{GDBN} knows in advance which syscalls are valid for
3983 each OS, so you can use the @value{GDBN} command-line completion
3984 facilities (@pxref{Completion,, command completion}) to list the
3987 You may also specify the system call numerically. A syscall's
3988 number is the value passed to the OS's syscall dispatcher to
3989 identify the requested service. When you specify the syscall by its
3990 name, @value{GDBN} uses its database of syscalls to convert the name
3991 into the corresponding numeric code, but using the number directly
3992 may be useful if @value{GDBN}'s database does not have the complete
3993 list of syscalls on your system (e.g., because @value{GDBN} lags
3994 behind the OS upgrades).
3996 The example below illustrates how this command works if you don't provide
4000 (@value{GDBP}) catch syscall
4001 Catchpoint 1 (syscall)
4003 Starting program: /tmp/catch-syscall
4005 Catchpoint 1 (call to syscall 'close'), \
4006 0xffffe424 in __kernel_vsyscall ()
4010 Catchpoint 1 (returned from syscall 'close'), \
4011 0xffffe424 in __kernel_vsyscall ()
4015 Here is an example of catching a system call by name:
4018 (@value{GDBP}) catch syscall chroot
4019 Catchpoint 1 (syscall 'chroot' [61])
4021 Starting program: /tmp/catch-syscall
4023 Catchpoint 1 (call to syscall 'chroot'), \
4024 0xffffe424 in __kernel_vsyscall ()
4028 Catchpoint 1 (returned from syscall 'chroot'), \
4029 0xffffe424 in __kernel_vsyscall ()
4033 An example of specifying a system call numerically. In the case
4034 below, the syscall number has a corresponding entry in the XML
4035 file, so @value{GDBN} finds its name and prints it:
4038 (@value{GDBP}) catch syscall 252
4039 Catchpoint 1 (syscall(s) 'exit_group')
4041 Starting program: /tmp/catch-syscall
4043 Catchpoint 1 (call to syscall 'exit_group'), \
4044 0xffffe424 in __kernel_vsyscall ()
4048 Program exited normally.
4052 However, there can be situations when there is no corresponding name
4053 in XML file for that syscall number. In this case, @value{GDBN} prints
4054 a warning message saying that it was not able to find the syscall name,
4055 but the catchpoint will be set anyway. See the example below:
4058 (@value{GDBP}) catch syscall 764
4059 warning: The number '764' does not represent a known syscall.
4060 Catchpoint 2 (syscall 764)
4064 If you configure @value{GDBN} using the @samp{--without-expat} option,
4065 it will not be able to display syscall names. Also, if your
4066 architecture does not have an XML file describing its system calls,
4067 you will not be able to see the syscall names. It is important to
4068 notice that these two features are used for accessing the syscall
4069 name database. In either case, you will see a warning like this:
4072 (@value{GDBP}) catch syscall
4073 warning: Could not open "syscalls/i386-linux.xml"
4074 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4075 GDB will not be able to display syscall names.
4076 Catchpoint 1 (syscall)
4080 Of course, the file name will change depending on your architecture and system.
4082 Still using the example above, you can also try to catch a syscall by its
4083 number. In this case, you would see something like:
4086 (@value{GDBP}) catch syscall 252
4087 Catchpoint 1 (syscall(s) 252)
4090 Again, in this case @value{GDBN} would not be able to display syscall's names.
4093 A call to @code{fork}. This is currently only available for HP-UX
4097 A call to @code{vfork}. This is currently only available for HP-UX
4102 @item tcatch @var{event}
4103 Set a catchpoint that is enabled only for one stop. The catchpoint is
4104 automatically deleted after the first time the event is caught.
4108 Use the @code{info break} command to list the current catchpoints.
4110 There are currently some limitations to C@t{++} exception handling
4111 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4115 If you call a function interactively, @value{GDBN} normally returns
4116 control to you when the function has finished executing. If the call
4117 raises an exception, however, the call may bypass the mechanism that
4118 returns control to you and cause your program either to abort or to
4119 simply continue running until it hits a breakpoint, catches a signal
4120 that @value{GDBN} is listening for, or exits. This is the case even if
4121 you set a catchpoint for the exception; catchpoints on exceptions are
4122 disabled within interactive calls.
4125 You cannot raise an exception interactively.
4128 You cannot install an exception handler interactively.
4131 @cindex raise exceptions
4132 Sometimes @code{catch} is not the best way to debug exception handling:
4133 if you need to know exactly where an exception is raised, it is better to
4134 stop @emph{before} the exception handler is called, since that way you
4135 can see the stack before any unwinding takes place. If you set a
4136 breakpoint in an exception handler instead, it may not be easy to find
4137 out where the exception was raised.
4139 To stop just before an exception handler is called, you need some
4140 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4141 raised by calling a library function named @code{__raise_exception}
4142 which has the following ANSI C interface:
4145 /* @var{addr} is where the exception identifier is stored.
4146 @var{id} is the exception identifier. */
4147 void __raise_exception (void **addr, void *id);
4151 To make the debugger catch all exceptions before any stack
4152 unwinding takes place, set a breakpoint on @code{__raise_exception}
4153 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4155 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4156 that depends on the value of @var{id}, you can stop your program when
4157 a specific exception is raised. You can use multiple conditional
4158 breakpoints to stop your program when any of a number of exceptions are
4163 @subsection Deleting Breakpoints
4165 @cindex clearing breakpoints, watchpoints, catchpoints
4166 @cindex deleting breakpoints, watchpoints, catchpoints
4167 It is often necessary to eliminate a breakpoint, watchpoint, or
4168 catchpoint once it has done its job and you no longer want your program
4169 to stop there. This is called @dfn{deleting} the breakpoint. A
4170 breakpoint that has been deleted no longer exists; it is forgotten.
4172 With the @code{clear} command you can delete breakpoints according to
4173 where they are in your program. With the @code{delete} command you can
4174 delete individual breakpoints, watchpoints, or catchpoints by specifying
4175 their breakpoint numbers.
4177 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4178 automatically ignores breakpoints on the first instruction to be executed
4179 when you continue execution without changing the execution address.
4184 Delete any breakpoints at the next instruction to be executed in the
4185 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4186 the innermost frame is selected, this is a good way to delete a
4187 breakpoint where your program just stopped.
4189 @item clear @var{location}
4190 Delete any breakpoints set at the specified @var{location}.
4191 @xref{Specify Location}, for the various forms of @var{location}; the
4192 most useful ones are listed below:
4195 @item clear @var{function}
4196 @itemx clear @var{filename}:@var{function}
4197 Delete any breakpoints set at entry to the named @var{function}.
4199 @item clear @var{linenum}
4200 @itemx clear @var{filename}:@var{linenum}
4201 Delete any breakpoints set at or within the code of the specified
4202 @var{linenum} of the specified @var{filename}.
4205 @cindex delete breakpoints
4207 @kindex d @r{(@code{delete})}
4208 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4209 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4210 ranges specified as arguments. If no argument is specified, delete all
4211 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4212 confirm off}). You can abbreviate this command as @code{d}.
4216 @subsection Disabling Breakpoints
4218 @cindex enable/disable a breakpoint
4219 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4220 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4221 it had been deleted, but remembers the information on the breakpoint so
4222 that you can @dfn{enable} it again later.
4224 You disable and enable breakpoints, watchpoints, and catchpoints with
4225 the @code{enable} and @code{disable} commands, optionally specifying
4226 one or more breakpoint numbers as arguments. Use @code{info break} to
4227 print a list of all breakpoints, watchpoints, and catchpoints if you
4228 do not know which numbers to use.
4230 Disabling and enabling a breakpoint that has multiple locations
4231 affects all of its locations.
4233 A breakpoint, watchpoint, or catchpoint can have any of four different
4234 states of enablement:
4238 Enabled. The breakpoint stops your program. A breakpoint set
4239 with the @code{break} command starts out in this state.
4241 Disabled. The breakpoint has no effect on your program.
4243 Enabled once. The breakpoint stops your program, but then becomes
4246 Enabled for deletion. The breakpoint stops your program, but
4247 immediately after it does so it is deleted permanently. A breakpoint
4248 set with the @code{tbreak} command starts out in this state.
4251 You can use the following commands to enable or disable breakpoints,
4252 watchpoints, and catchpoints:
4256 @kindex dis @r{(@code{disable})}
4257 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4258 Disable the specified breakpoints---or all breakpoints, if none are
4259 listed. A disabled breakpoint has no effect but is not forgotten. All
4260 options such as ignore-counts, conditions and commands are remembered in
4261 case the breakpoint is enabled again later. You may abbreviate
4262 @code{disable} as @code{dis}.
4265 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4266 Enable the specified breakpoints (or all defined breakpoints). They
4267 become effective once again in stopping your program.
4269 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4270 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4271 of these breakpoints immediately after stopping your program.
4273 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4274 Enable the specified breakpoints to work once, then die. @value{GDBN}
4275 deletes any of these breakpoints as soon as your program stops there.
4276 Breakpoints set by the @code{tbreak} command start out in this state.
4279 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4280 @c confusing: tbreak is also initially enabled.
4281 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4282 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4283 subsequently, they become disabled or enabled only when you use one of
4284 the commands above. (The command @code{until} can set and delete a
4285 breakpoint of its own, but it does not change the state of your other
4286 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4290 @subsection Break Conditions
4291 @cindex conditional breakpoints
4292 @cindex breakpoint conditions
4294 @c FIXME what is scope of break condition expr? Context where wanted?
4295 @c in particular for a watchpoint?
4296 The simplest sort of breakpoint breaks every time your program reaches a
4297 specified place. You can also specify a @dfn{condition} for a
4298 breakpoint. A condition is just a Boolean expression in your
4299 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4300 a condition evaluates the expression each time your program reaches it,
4301 and your program stops only if the condition is @emph{true}.
4303 This is the converse of using assertions for program validation; in that
4304 situation, you want to stop when the assertion is violated---that is,
4305 when the condition is false. In C, if you want to test an assertion expressed
4306 by the condition @var{assert}, you should set the condition
4307 @samp{! @var{assert}} on the appropriate breakpoint.
4309 Conditions are also accepted for watchpoints; you may not need them,
4310 since a watchpoint is inspecting the value of an expression anyhow---but
4311 it might be simpler, say, to just set a watchpoint on a variable name,
4312 and specify a condition that tests whether the new value is an interesting
4315 Break conditions can have side effects, and may even call functions in
4316 your program. This can be useful, for example, to activate functions
4317 that log program progress, or to use your own print functions to
4318 format special data structures. The effects are completely predictable
4319 unless there is another enabled breakpoint at the same address. (In
4320 that case, @value{GDBN} might see the other breakpoint first and stop your
4321 program without checking the condition of this one.) Note that
4322 breakpoint commands are usually more convenient and flexible than break
4324 purpose of performing side effects when a breakpoint is reached
4325 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4327 Break conditions can be specified when a breakpoint is set, by using
4328 @samp{if} in the arguments to the @code{break} command. @xref{Set
4329 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4330 with the @code{condition} command.
4332 You can also use the @code{if} keyword with the @code{watch} command.
4333 The @code{catch} command does not recognize the @code{if} keyword;
4334 @code{condition} is the only way to impose a further condition on a
4339 @item condition @var{bnum} @var{expression}
4340 Specify @var{expression} as the break condition for breakpoint,
4341 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4342 breakpoint @var{bnum} stops your program only if the value of
4343 @var{expression} is true (nonzero, in C). When you use
4344 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4345 syntactic correctness, and to determine whether symbols in it have
4346 referents in the context of your breakpoint. If @var{expression} uses
4347 symbols not referenced in the context of the breakpoint, @value{GDBN}
4348 prints an error message:
4351 No symbol "foo" in current context.
4356 not actually evaluate @var{expression} at the time the @code{condition}
4357 command (or a command that sets a breakpoint with a condition, like
4358 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4360 @item condition @var{bnum}
4361 Remove the condition from breakpoint number @var{bnum}. It becomes
4362 an ordinary unconditional breakpoint.
4365 @cindex ignore count (of breakpoint)
4366 A special case of a breakpoint condition is to stop only when the
4367 breakpoint has been reached a certain number of times. This is so
4368 useful that there is a special way to do it, using the @dfn{ignore
4369 count} of the breakpoint. Every breakpoint has an ignore count, which
4370 is an integer. Most of the time, the ignore count is zero, and
4371 therefore has no effect. But if your program reaches a breakpoint whose
4372 ignore count is positive, then instead of stopping, it just decrements
4373 the ignore count by one and continues. As a result, if the ignore count
4374 value is @var{n}, the breakpoint does not stop the next @var{n} times
4375 your program reaches it.
4379 @item ignore @var{bnum} @var{count}
4380 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4381 The next @var{count} times the breakpoint is reached, your program's
4382 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4385 To make the breakpoint stop the next time it is reached, specify
4388 When you use @code{continue} to resume execution of your program from a
4389 breakpoint, you can specify an ignore count directly as an argument to
4390 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4391 Stepping,,Continuing and Stepping}.
4393 If a breakpoint has a positive ignore count and a condition, the
4394 condition is not checked. Once the ignore count reaches zero,
4395 @value{GDBN} resumes checking the condition.
4397 You could achieve the effect of the ignore count with a condition such
4398 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4399 is decremented each time. @xref{Convenience Vars, ,Convenience
4403 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4406 @node Break Commands
4407 @subsection Breakpoint Command Lists
4409 @cindex breakpoint commands
4410 You can give any breakpoint (or watchpoint or catchpoint) a series of
4411 commands to execute when your program stops due to that breakpoint. For
4412 example, you might want to print the values of certain expressions, or
4413 enable other breakpoints.
4417 @kindex end@r{ (breakpoint commands)}
4418 @item commands @r{[}@var{range}@dots{}@r{]}
4419 @itemx @dots{} @var{command-list} @dots{}
4421 Specify a list of commands for the given breakpoints. The commands
4422 themselves appear on the following lines. Type a line containing just
4423 @code{end} to terminate the commands.
4425 To remove all commands from a breakpoint, type @code{commands} and
4426 follow it immediately with @code{end}; that is, give no commands.
4428 With no argument, @code{commands} refers to the last breakpoint,
4429 watchpoint, or catchpoint set (not to the breakpoint most recently
4430 encountered). If the most recent breakpoints were set with a single
4431 command, then the @code{commands} will apply to all the breakpoints
4432 set by that command. This applies to breakpoints set by
4433 @code{rbreak}, and also applies when a single @code{break} command
4434 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4438 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4439 disabled within a @var{command-list}.
4441 You can use breakpoint commands to start your program up again. Simply
4442 use the @code{continue} command, or @code{step}, or any other command
4443 that resumes execution.
4445 Any other commands in the command list, after a command that resumes
4446 execution, are ignored. This is because any time you resume execution
4447 (even with a simple @code{next} or @code{step}), you may encounter
4448 another breakpoint---which could have its own command list, leading to
4449 ambiguities about which list to execute.
4452 If the first command you specify in a command list is @code{silent}, the
4453 usual message about stopping at a breakpoint is not printed. This may
4454 be desirable for breakpoints that are to print a specific message and
4455 then continue. If none of the remaining commands print anything, you
4456 see no sign that the breakpoint was reached. @code{silent} is
4457 meaningful only at the beginning of a breakpoint command list.
4459 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4460 print precisely controlled output, and are often useful in silent
4461 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4463 For example, here is how you could use breakpoint commands to print the
4464 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4470 printf "x is %d\n",x
4475 One application for breakpoint commands is to compensate for one bug so
4476 you can test for another. Put a breakpoint just after the erroneous line
4477 of code, give it a condition to detect the case in which something
4478 erroneous has been done, and give it commands to assign correct values
4479 to any variables that need them. End with the @code{continue} command
4480 so that your program does not stop, and start with the @code{silent}
4481 command so that no output is produced. Here is an example:
4492 @node Save Breakpoints
4493 @subsection How to save breakpoints to a file
4495 To save breakpoint definitions to a file use the @w{@code{save
4496 breakpoints}} command.
4499 @kindex save breakpoints
4500 @cindex save breakpoints to a file for future sessions
4501 @item save breakpoints [@var{filename}]
4502 This command saves all current breakpoint definitions together with
4503 their commands and ignore counts, into a file @file{@var{filename}}
4504 suitable for use in a later debugging session. This includes all
4505 types of breakpoints (breakpoints, watchpoints, catchpoints,
4506 tracepoints). To read the saved breakpoint definitions, use the
4507 @code{source} command (@pxref{Command Files}). Note that watchpoints
4508 with expressions involving local variables may fail to be recreated
4509 because it may not be possible to access the context where the
4510 watchpoint is valid anymore. Because the saved breakpoint definitions
4511 are simply a sequence of @value{GDBN} commands that recreate the
4512 breakpoints, you can edit the file in your favorite editing program,
4513 and remove the breakpoint definitions you're not interested in, or
4514 that can no longer be recreated.
4517 @c @ifclear BARETARGET
4518 @node Error in Breakpoints
4519 @subsection ``Cannot insert breakpoints''
4521 If you request too many active hardware-assisted breakpoints and
4522 watchpoints, you will see this error message:
4524 @c FIXME: the precise wording of this message may change; the relevant
4525 @c source change is not committed yet (Sep 3, 1999).
4527 Stopped; cannot insert breakpoints.
4528 You may have requested too many hardware breakpoints and watchpoints.
4532 This message is printed when you attempt to resume the program, since
4533 only then @value{GDBN} knows exactly how many hardware breakpoints and
4534 watchpoints it needs to insert.
4536 When this message is printed, you need to disable or remove some of the
4537 hardware-assisted breakpoints and watchpoints, and then continue.
4539 @node Breakpoint-related Warnings
4540 @subsection ``Breakpoint address adjusted...''
4541 @cindex breakpoint address adjusted
4543 Some processor architectures place constraints on the addresses at
4544 which breakpoints may be placed. For architectures thus constrained,
4545 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4546 with the constraints dictated by the architecture.
4548 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4549 a VLIW architecture in which a number of RISC-like instructions may be
4550 bundled together for parallel execution. The FR-V architecture
4551 constrains the location of a breakpoint instruction within such a
4552 bundle to the instruction with the lowest address. @value{GDBN}
4553 honors this constraint by adjusting a breakpoint's address to the
4554 first in the bundle.
4556 It is not uncommon for optimized code to have bundles which contain
4557 instructions from different source statements, thus it may happen that
4558 a breakpoint's address will be adjusted from one source statement to
4559 another. Since this adjustment may significantly alter @value{GDBN}'s
4560 breakpoint related behavior from what the user expects, a warning is
4561 printed when the breakpoint is first set and also when the breakpoint
4564 A warning like the one below is printed when setting a breakpoint
4565 that's been subject to address adjustment:
4568 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4571 Such warnings are printed both for user settable and @value{GDBN}'s
4572 internal breakpoints. If you see one of these warnings, you should
4573 verify that a breakpoint set at the adjusted address will have the
4574 desired affect. If not, the breakpoint in question may be removed and
4575 other breakpoints may be set which will have the desired behavior.
4576 E.g., it may be sufficient to place the breakpoint at a later
4577 instruction. A conditional breakpoint may also be useful in some
4578 cases to prevent the breakpoint from triggering too often.
4580 @value{GDBN} will also issue a warning when stopping at one of these
4581 adjusted breakpoints:
4584 warning: Breakpoint 1 address previously adjusted from 0x00010414
4588 When this warning is encountered, it may be too late to take remedial
4589 action except in cases where the breakpoint is hit earlier or more
4590 frequently than expected.
4592 @node Continuing and Stepping
4593 @section Continuing and Stepping
4597 @cindex resuming execution
4598 @dfn{Continuing} means resuming program execution until your program
4599 completes normally. In contrast, @dfn{stepping} means executing just
4600 one more ``step'' of your program, where ``step'' may mean either one
4601 line of source code, or one machine instruction (depending on what
4602 particular command you use). Either when continuing or when stepping,
4603 your program may stop even sooner, due to a breakpoint or a signal. (If
4604 it stops due to a signal, you may want to use @code{handle}, or use
4605 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4609 @kindex c @r{(@code{continue})}
4610 @kindex fg @r{(resume foreground execution)}
4611 @item continue @r{[}@var{ignore-count}@r{]}
4612 @itemx c @r{[}@var{ignore-count}@r{]}
4613 @itemx fg @r{[}@var{ignore-count}@r{]}
4614 Resume program execution, at the address where your program last stopped;
4615 any breakpoints set at that address are bypassed. The optional argument
4616 @var{ignore-count} allows you to specify a further number of times to
4617 ignore a breakpoint at this location; its effect is like that of
4618 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4620 The argument @var{ignore-count} is meaningful only when your program
4621 stopped due to a breakpoint. At other times, the argument to
4622 @code{continue} is ignored.
4624 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4625 debugged program is deemed to be the foreground program) are provided
4626 purely for convenience, and have exactly the same behavior as
4630 To resume execution at a different place, you can use @code{return}
4631 (@pxref{Returning, ,Returning from a Function}) to go back to the
4632 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4633 Different Address}) to go to an arbitrary location in your program.
4635 A typical technique for using stepping is to set a breakpoint
4636 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4637 beginning of the function or the section of your program where a problem
4638 is believed to lie, run your program until it stops at that breakpoint,
4639 and then step through the suspect area, examining the variables that are
4640 interesting, until you see the problem happen.
4644 @kindex s @r{(@code{step})}
4646 Continue running your program until control reaches a different source
4647 line, then stop it and return control to @value{GDBN}. This command is
4648 abbreviated @code{s}.
4651 @c "without debugging information" is imprecise; actually "without line
4652 @c numbers in the debugging information". (gcc -g1 has debugging info but
4653 @c not line numbers). But it seems complex to try to make that
4654 @c distinction here.
4655 @emph{Warning:} If you use the @code{step} command while control is
4656 within a function that was compiled without debugging information,
4657 execution proceeds until control reaches a function that does have
4658 debugging information. Likewise, it will not step into a function which
4659 is compiled without debugging information. To step through functions
4660 without debugging information, use the @code{stepi} command, described
4664 The @code{step} command only stops at the first instruction of a source
4665 line. This prevents the multiple stops that could otherwise occur in
4666 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4667 to stop if a function that has debugging information is called within
4668 the line. In other words, @code{step} @emph{steps inside} any functions
4669 called within the line.
4671 Also, the @code{step} command only enters a function if there is line
4672 number information for the function. Otherwise it acts like the
4673 @code{next} command. This avoids problems when using @code{cc -gl}
4674 on MIPS machines. Previously, @code{step} entered subroutines if there
4675 was any debugging information about the routine.
4677 @item step @var{count}
4678 Continue running as in @code{step}, but do so @var{count} times. If a
4679 breakpoint is reached, or a signal not related to stepping occurs before
4680 @var{count} steps, stepping stops right away.
4683 @kindex n @r{(@code{next})}
4684 @item next @r{[}@var{count}@r{]}
4685 Continue to the next source line in the current (innermost) stack frame.
4686 This is similar to @code{step}, but function calls that appear within
4687 the line of code are executed without stopping. Execution stops when
4688 control reaches a different line of code at the original stack level
4689 that was executing when you gave the @code{next} command. This command
4690 is abbreviated @code{n}.
4692 An argument @var{count} is a repeat count, as for @code{step}.
4695 @c FIX ME!! Do we delete this, or is there a way it fits in with
4696 @c the following paragraph? --- Vctoria
4698 @c @code{next} within a function that lacks debugging information acts like
4699 @c @code{step}, but any function calls appearing within the code of the
4700 @c function are executed without stopping.
4702 The @code{next} command only stops at the first instruction of a
4703 source line. This prevents multiple stops that could otherwise occur in
4704 @code{switch} statements, @code{for} loops, etc.
4706 @kindex set step-mode
4708 @cindex functions without line info, and stepping
4709 @cindex stepping into functions with no line info
4710 @itemx set step-mode on
4711 The @code{set step-mode on} command causes the @code{step} command to
4712 stop at the first instruction of a function which contains no debug line
4713 information rather than stepping over it.
4715 This is useful in cases where you may be interested in inspecting the
4716 machine instructions of a function which has no symbolic info and do not
4717 want @value{GDBN} to automatically skip over this function.
4719 @item set step-mode off
4720 Causes the @code{step} command to step over any functions which contains no
4721 debug information. This is the default.
4723 @item show step-mode
4724 Show whether @value{GDBN} will stop in or step over functions without
4725 source line debug information.
4728 @kindex fin @r{(@code{finish})}
4730 Continue running until just after function in the selected stack frame
4731 returns. Print the returned value (if any). This command can be
4732 abbreviated as @code{fin}.
4734 Contrast this with the @code{return} command (@pxref{Returning,
4735 ,Returning from a Function}).
4738 @kindex u @r{(@code{until})}
4739 @cindex run until specified location
4742 Continue running until a source line past the current line, in the
4743 current stack frame, is reached. This command is used to avoid single
4744 stepping through a loop more than once. It is like the @code{next}
4745 command, except that when @code{until} encounters a jump, it
4746 automatically continues execution until the program counter is greater
4747 than the address of the jump.
4749 This means that when you reach the end of a loop after single stepping
4750 though it, @code{until} makes your program continue execution until it
4751 exits the loop. In contrast, a @code{next} command at the end of a loop
4752 simply steps back to the beginning of the loop, which forces you to step
4753 through the next iteration.
4755 @code{until} always stops your program if it attempts to exit the current
4758 @code{until} may produce somewhat counterintuitive results if the order
4759 of machine code does not match the order of the source lines. For
4760 example, in the following excerpt from a debugging session, the @code{f}
4761 (@code{frame}) command shows that execution is stopped at line
4762 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4766 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4768 (@value{GDBP}) until
4769 195 for ( ; argc > 0; NEXTARG) @{
4772 This happened because, for execution efficiency, the compiler had
4773 generated code for the loop closure test at the end, rather than the
4774 start, of the loop---even though the test in a C @code{for}-loop is
4775 written before the body of the loop. The @code{until} command appeared
4776 to step back to the beginning of the loop when it advanced to this
4777 expression; however, it has not really gone to an earlier
4778 statement---not in terms of the actual machine code.
4780 @code{until} with no argument works by means of single
4781 instruction stepping, and hence is slower than @code{until} with an
4784 @item until @var{location}
4785 @itemx u @var{location}
4786 Continue running your program until either the specified location is
4787 reached, or the current stack frame returns. @var{location} is any of
4788 the forms described in @ref{Specify Location}.
4789 This form of the command uses temporary breakpoints, and
4790 hence is quicker than @code{until} without an argument. The specified
4791 location is actually reached only if it is in the current frame. This
4792 implies that @code{until} can be used to skip over recursive function
4793 invocations. For instance in the code below, if the current location is
4794 line @code{96}, issuing @code{until 99} will execute the program up to
4795 line @code{99} in the same invocation of factorial, i.e., after the inner
4796 invocations have returned.
4799 94 int factorial (int value)
4801 96 if (value > 1) @{
4802 97 value *= factorial (value - 1);
4809 @kindex advance @var{location}
4810 @itemx advance @var{location}
4811 Continue running the program up to the given @var{location}. An argument is
4812 required, which should be of one of the forms described in
4813 @ref{Specify Location}.
4814 Execution will also stop upon exit from the current stack
4815 frame. This command is similar to @code{until}, but @code{advance} will
4816 not skip over recursive function calls, and the target location doesn't
4817 have to be in the same frame as the current one.
4821 @kindex si @r{(@code{stepi})}
4823 @itemx stepi @var{arg}
4825 Execute one machine instruction, then stop and return to the debugger.
4827 It is often useful to do @samp{display/i $pc} when stepping by machine
4828 instructions. This makes @value{GDBN} automatically display the next
4829 instruction to be executed, each time your program stops. @xref{Auto
4830 Display,, Automatic Display}.
4832 An argument is a repeat count, as in @code{step}.
4836 @kindex ni @r{(@code{nexti})}
4838 @itemx nexti @var{arg}
4840 Execute one machine instruction, but if it is a function call,
4841 proceed until the function returns.
4843 An argument is a repeat count, as in @code{next}.
4850 A signal is an asynchronous event that can happen in a program. The
4851 operating system defines the possible kinds of signals, and gives each
4852 kind a name and a number. For example, in Unix @code{SIGINT} is the
4853 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4854 @code{SIGSEGV} is the signal a program gets from referencing a place in
4855 memory far away from all the areas in use; @code{SIGALRM} occurs when
4856 the alarm clock timer goes off (which happens only if your program has
4857 requested an alarm).
4859 @cindex fatal signals
4860 Some signals, including @code{SIGALRM}, are a normal part of the
4861 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4862 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4863 program has not specified in advance some other way to handle the signal.
4864 @code{SIGINT} does not indicate an error in your program, but it is normally
4865 fatal so it can carry out the purpose of the interrupt: to kill the program.
4867 @value{GDBN} has the ability to detect any occurrence of a signal in your
4868 program. You can tell @value{GDBN} in advance what to do for each kind of
4871 @cindex handling signals
4872 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4873 @code{SIGALRM} be silently passed to your program
4874 (so as not to interfere with their role in the program's functioning)
4875 but to stop your program immediately whenever an error signal happens.
4876 You can change these settings with the @code{handle} command.
4879 @kindex info signals
4883 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4884 handle each one. You can use this to see the signal numbers of all
4885 the defined types of signals.
4887 @item info signals @var{sig}
4888 Similar, but print information only about the specified signal number.
4890 @code{info handle} is an alias for @code{info signals}.
4893 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4894 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4895 can be the number of a signal or its name (with or without the
4896 @samp{SIG} at the beginning); a list of signal numbers of the form
4897 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4898 known signals. Optional arguments @var{keywords}, described below,
4899 say what change to make.
4903 The keywords allowed by the @code{handle} command can be abbreviated.
4904 Their full names are:
4908 @value{GDBN} should not stop your program when this signal happens. It may
4909 still print a message telling you that the signal has come in.
4912 @value{GDBN} should stop your program when this signal happens. This implies
4913 the @code{print} keyword as well.
4916 @value{GDBN} should print a message when this signal happens.
4919 @value{GDBN} should not mention the occurrence of the signal at all. This
4920 implies the @code{nostop} keyword as well.
4924 @value{GDBN} should allow your program to see this signal; your program
4925 can handle the signal, or else it may terminate if the signal is fatal
4926 and not handled. @code{pass} and @code{noignore} are synonyms.
4930 @value{GDBN} should not allow your program to see this signal.
4931 @code{nopass} and @code{ignore} are synonyms.
4935 When a signal stops your program, the signal is not visible to the
4937 continue. Your program sees the signal then, if @code{pass} is in
4938 effect for the signal in question @emph{at that time}. In other words,
4939 after @value{GDBN} reports a signal, you can use the @code{handle}
4940 command with @code{pass} or @code{nopass} to control whether your
4941 program sees that signal when you continue.
4943 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4944 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4945 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4948 You can also use the @code{signal} command to prevent your program from
4949 seeing a signal, or cause it to see a signal it normally would not see,
4950 or to give it any signal at any time. For example, if your program stopped
4951 due to some sort of memory reference error, you might store correct
4952 values into the erroneous variables and continue, hoping to see more
4953 execution; but your program would probably terminate immediately as
4954 a result of the fatal signal once it saw the signal. To prevent this,
4955 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4958 @cindex extra signal information
4959 @anchor{extra signal information}
4961 On some targets, @value{GDBN} can inspect extra signal information
4962 associated with the intercepted signal, before it is actually
4963 delivered to the program being debugged. This information is exported
4964 by the convenience variable @code{$_siginfo}, and consists of data
4965 that is passed by the kernel to the signal handler at the time of the
4966 receipt of a signal. The data type of the information itself is
4967 target dependent. You can see the data type using the @code{ptype
4968 $_siginfo} command. On Unix systems, it typically corresponds to the
4969 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4972 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4973 referenced address that raised a segmentation fault.
4977 (@value{GDBP}) continue
4978 Program received signal SIGSEGV, Segmentation fault.
4979 0x0000000000400766 in main ()
4981 (@value{GDBP}) ptype $_siginfo
4988 struct @{...@} _kill;
4989 struct @{...@} _timer;
4991 struct @{...@} _sigchld;
4992 struct @{...@} _sigfault;
4993 struct @{...@} _sigpoll;
4996 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5000 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5001 $1 = (void *) 0x7ffff7ff7000
5005 Depending on target support, @code{$_siginfo} may also be writable.
5008 @section Stopping and Starting Multi-thread Programs
5010 @cindex stopped threads
5011 @cindex threads, stopped
5013 @cindex continuing threads
5014 @cindex threads, continuing
5016 @value{GDBN} supports debugging programs with multiple threads
5017 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5018 are two modes of controlling execution of your program within the
5019 debugger. In the default mode, referred to as @dfn{all-stop mode},
5020 when any thread in your program stops (for example, at a breakpoint
5021 or while being stepped), all other threads in the program are also stopped by
5022 @value{GDBN}. On some targets, @value{GDBN} also supports
5023 @dfn{non-stop mode}, in which other threads can continue to run freely while
5024 you examine the stopped thread in the debugger.
5027 * All-Stop Mode:: All threads stop when GDB takes control
5028 * Non-Stop Mode:: Other threads continue to execute
5029 * Background Execution:: Running your program asynchronously
5030 * Thread-Specific Breakpoints:: Controlling breakpoints
5031 * Interrupted System Calls:: GDB may interfere with system calls
5032 * Observer Mode:: GDB does not alter program behavior
5036 @subsection All-Stop Mode
5038 @cindex all-stop mode
5040 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5041 @emph{all} threads of execution stop, not just the current thread. This
5042 allows you to examine the overall state of the program, including
5043 switching between threads, without worrying that things may change
5046 Conversely, whenever you restart the program, @emph{all} threads start
5047 executing. @emph{This is true even when single-stepping} with commands
5048 like @code{step} or @code{next}.
5050 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5051 Since thread scheduling is up to your debugging target's operating
5052 system (not controlled by @value{GDBN}), other threads may
5053 execute more than one statement while the current thread completes a
5054 single step. Moreover, in general other threads stop in the middle of a
5055 statement, rather than at a clean statement boundary, when the program
5058 You might even find your program stopped in another thread after
5059 continuing or even single-stepping. This happens whenever some other
5060 thread runs into a breakpoint, a signal, or an exception before the
5061 first thread completes whatever you requested.
5063 @cindex automatic thread selection
5064 @cindex switching threads automatically
5065 @cindex threads, automatic switching
5066 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5067 signal, it automatically selects the thread where that breakpoint or
5068 signal happened. @value{GDBN} alerts you to the context switch with a
5069 message such as @samp{[Switching to Thread @var{n}]} to identify the
5072 On some OSes, you can modify @value{GDBN}'s default behavior by
5073 locking the OS scheduler to allow only a single thread to run.
5076 @item set scheduler-locking @var{mode}
5077 @cindex scheduler locking mode
5078 @cindex lock scheduler
5079 Set the scheduler locking mode. If it is @code{off}, then there is no
5080 locking and any thread may run at any time. If @code{on}, then only the
5081 current thread may run when the inferior is resumed. The @code{step}
5082 mode optimizes for single-stepping; it prevents other threads
5083 from preempting the current thread while you are stepping, so that
5084 the focus of debugging does not change unexpectedly.
5085 Other threads only rarely (or never) get a chance to run
5086 when you step. They are more likely to run when you @samp{next} over a
5087 function call, and they are completely free to run when you use commands
5088 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5089 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5090 the current thread away from the thread that you are debugging.
5092 @item show scheduler-locking
5093 Display the current scheduler locking mode.
5096 @cindex resume threads of multiple processes simultaneously
5097 By default, when you issue one of the execution commands such as
5098 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5099 threads of the current inferior to run. For example, if @value{GDBN}
5100 is attached to two inferiors, each with two threads, the
5101 @code{continue} command resumes only the two threads of the current
5102 inferior. This is useful, for example, when you debug a program that
5103 forks and you want to hold the parent stopped (so that, for instance,
5104 it doesn't run to exit), while you debug the child. In other
5105 situations, you may not be interested in inspecting the current state
5106 of any of the processes @value{GDBN} is attached to, and you may want
5107 to resume them all until some breakpoint is hit. In the latter case,
5108 you can instruct @value{GDBN} to allow all threads of all the
5109 inferiors to run with the @w{@code{set schedule-multiple}} command.
5112 @kindex set schedule-multiple
5113 @item set schedule-multiple
5114 Set the mode for allowing threads of multiple processes to be resumed
5115 when an execution command is issued. When @code{on}, all threads of
5116 all processes are allowed to run. When @code{off}, only the threads
5117 of the current process are resumed. The default is @code{off}. The
5118 @code{scheduler-locking} mode takes precedence when set to @code{on},
5119 or while you are stepping and set to @code{step}.
5121 @item show schedule-multiple
5122 Display the current mode for resuming the execution of threads of
5127 @subsection Non-Stop Mode
5129 @cindex non-stop mode
5131 @c This section is really only a place-holder, and needs to be expanded
5132 @c with more details.
5134 For some multi-threaded targets, @value{GDBN} supports an optional
5135 mode of operation in which you can examine stopped program threads in
5136 the debugger while other threads continue to execute freely. This
5137 minimizes intrusion when debugging live systems, such as programs
5138 where some threads have real-time constraints or must continue to
5139 respond to external events. This is referred to as @dfn{non-stop} mode.
5141 In non-stop mode, when a thread stops to report a debugging event,
5142 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5143 threads as well, in contrast to the all-stop mode behavior. Additionally,
5144 execution commands such as @code{continue} and @code{step} apply by default
5145 only to the current thread in non-stop mode, rather than all threads as
5146 in all-stop mode. This allows you to control threads explicitly in
5147 ways that are not possible in all-stop mode --- for example, stepping
5148 one thread while allowing others to run freely, stepping
5149 one thread while holding all others stopped, or stepping several threads
5150 independently and simultaneously.
5152 To enter non-stop mode, use this sequence of commands before you run
5153 or attach to your program:
5156 # Enable the async interface.
5159 # If using the CLI, pagination breaks non-stop.
5162 # Finally, turn it on!
5166 You can use these commands to manipulate the non-stop mode setting:
5169 @kindex set non-stop
5170 @item set non-stop on
5171 Enable selection of non-stop mode.
5172 @item set non-stop off
5173 Disable selection of non-stop mode.
5174 @kindex show non-stop
5176 Show the current non-stop enablement setting.
5179 Note these commands only reflect whether non-stop mode is enabled,
5180 not whether the currently-executing program is being run in non-stop mode.
5181 In particular, the @code{set non-stop} preference is only consulted when
5182 @value{GDBN} starts or connects to the target program, and it is generally
5183 not possible to switch modes once debugging has started. Furthermore,
5184 since not all targets support non-stop mode, even when you have enabled
5185 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5188 In non-stop mode, all execution commands apply only to the current thread
5189 by default. That is, @code{continue} only continues one thread.
5190 To continue all threads, issue @code{continue -a} or @code{c -a}.
5192 You can use @value{GDBN}'s background execution commands
5193 (@pxref{Background Execution}) to run some threads in the background
5194 while you continue to examine or step others from @value{GDBN}.
5195 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5196 always executed asynchronously in non-stop mode.
5198 Suspending execution is done with the @code{interrupt} command when
5199 running in the background, or @kbd{Ctrl-c} during foreground execution.
5200 In all-stop mode, this stops the whole process;
5201 but in non-stop mode the interrupt applies only to the current thread.
5202 To stop the whole program, use @code{interrupt -a}.
5204 Other execution commands do not currently support the @code{-a} option.
5206 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5207 that thread current, as it does in all-stop mode. This is because the
5208 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5209 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5210 changed to a different thread just as you entered a command to operate on the
5211 previously current thread.
5213 @node Background Execution
5214 @subsection Background Execution
5216 @cindex foreground execution
5217 @cindex background execution
5218 @cindex asynchronous execution
5219 @cindex execution, foreground, background and asynchronous
5221 @value{GDBN}'s execution commands have two variants: the normal
5222 foreground (synchronous) behavior, and a background
5223 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5224 the program to report that some thread has stopped before prompting for
5225 another command. In background execution, @value{GDBN} immediately gives
5226 a command prompt so that you can issue other commands while your program runs.
5228 You need to explicitly enable asynchronous mode before you can use
5229 background execution commands. You can use these commands to
5230 manipulate the asynchronous mode setting:
5233 @kindex set target-async
5234 @item set target-async on
5235 Enable asynchronous mode.
5236 @item set target-async off
5237 Disable asynchronous mode.
5238 @kindex show target-async
5239 @item show target-async
5240 Show the current target-async setting.
5243 If the target doesn't support async mode, @value{GDBN} issues an error
5244 message if you attempt to use the background execution commands.
5246 To specify background execution, add a @code{&} to the command. For example,
5247 the background form of the @code{continue} command is @code{continue&}, or
5248 just @code{c&}. The execution commands that accept background execution
5254 @xref{Starting, , Starting your Program}.
5258 @xref{Attach, , Debugging an Already-running Process}.
5262 @xref{Continuing and Stepping, step}.
5266 @xref{Continuing and Stepping, stepi}.
5270 @xref{Continuing and Stepping, next}.
5274 @xref{Continuing and Stepping, nexti}.
5278 @xref{Continuing and Stepping, continue}.
5282 @xref{Continuing and Stepping, finish}.
5286 @xref{Continuing and Stepping, until}.
5290 Background execution is especially useful in conjunction with non-stop
5291 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5292 However, you can also use these commands in the normal all-stop mode with
5293 the restriction that you cannot issue another execution command until the
5294 previous one finishes. Examples of commands that are valid in all-stop
5295 mode while the program is running include @code{help} and @code{info break}.
5297 You can interrupt your program while it is running in the background by
5298 using the @code{interrupt} command.
5305 Suspend execution of the running program. In all-stop mode,
5306 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5307 only the current thread. To stop the whole program in non-stop mode,
5308 use @code{interrupt -a}.
5311 @node Thread-Specific Breakpoints
5312 @subsection Thread-Specific Breakpoints
5314 When your program has multiple threads (@pxref{Threads,, Debugging
5315 Programs with Multiple Threads}), you can choose whether to set
5316 breakpoints on all threads, or on a particular thread.
5319 @cindex breakpoints and threads
5320 @cindex thread breakpoints
5321 @kindex break @dots{} thread @var{threadno}
5322 @item break @var{linespec} thread @var{threadno}
5323 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5324 @var{linespec} specifies source lines; there are several ways of
5325 writing them (@pxref{Specify Location}), but the effect is always to
5326 specify some source line.
5328 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5329 to specify that you only want @value{GDBN} to stop the program when a
5330 particular thread reaches this breakpoint. @var{threadno} is one of the
5331 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5332 column of the @samp{info threads} display.
5334 If you do not specify @samp{thread @var{threadno}} when you set a
5335 breakpoint, the breakpoint applies to @emph{all} threads of your
5338 You can use the @code{thread} qualifier on conditional breakpoints as
5339 well; in this case, place @samp{thread @var{threadno}} before or
5340 after the breakpoint condition, like this:
5343 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5348 @node Interrupted System Calls
5349 @subsection Interrupted System Calls
5351 @cindex thread breakpoints and system calls
5352 @cindex system calls and thread breakpoints
5353 @cindex premature return from system calls
5354 There is an unfortunate side effect when using @value{GDBN} to debug
5355 multi-threaded programs. If one thread stops for a
5356 breakpoint, or for some other reason, and another thread is blocked in a
5357 system call, then the system call may return prematurely. This is a
5358 consequence of the interaction between multiple threads and the signals
5359 that @value{GDBN} uses to implement breakpoints and other events that
5362 To handle this problem, your program should check the return value of
5363 each system call and react appropriately. This is good programming
5366 For example, do not write code like this:
5372 The call to @code{sleep} will return early if a different thread stops
5373 at a breakpoint or for some other reason.
5375 Instead, write this:
5380 unslept = sleep (unslept);
5383 A system call is allowed to return early, so the system is still
5384 conforming to its specification. But @value{GDBN} does cause your
5385 multi-threaded program to behave differently than it would without
5388 Also, @value{GDBN} uses internal breakpoints in the thread library to
5389 monitor certain events such as thread creation and thread destruction.
5390 When such an event happens, a system call in another thread may return
5391 prematurely, even though your program does not appear to stop.
5394 @subsection Observer Mode
5396 If you want to build on non-stop mode and observe program behavior
5397 without any chance of disruption by @value{GDBN}, you can set
5398 variables to disable all of the debugger's attempts to modify state,
5399 whether by writing memory, inserting breakpoints, etc. These operate
5400 at a low level, intercepting operations from all commands.
5402 When all of these are set to @code{off}, then @value{GDBN} is said to
5403 be @dfn{observer mode}. As a convenience, the variable
5404 @code{observer} can be set to disable these, plus enable non-stop
5407 Note that @value{GDBN} will not prevent you from making nonsensical
5408 combinations of these settings. For instance, if you have enabled
5409 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5410 then breakpoints that work by writing trap instructions into the code
5411 stream will still not be able to be placed.
5416 @item set observer on
5417 @itemx set observer off
5418 When set to @code{on}, this disables all the permission variables
5419 below (except for @code{insert-fast-tracepoints}), plus enables
5420 non-stop debugging. Setting this to @code{off} switches back to
5421 normal debugging, though remaining in non-stop mode.
5424 Show whether observer mode is on or off.
5426 @kindex may-write-registers
5427 @item set may-write-registers on
5428 @itemx set may-write-registers off
5429 This controls whether @value{GDBN} will attempt to alter the values of
5430 registers, such as with assignment expressions in @code{print}, or the
5431 @code{jump} command. It defaults to @code{on}.
5433 @item show may-write-registers
5434 Show the current permission to write registers.
5436 @kindex may-write-memory
5437 @item set may-write-memory on
5438 @itemx set may-write-memory off
5439 This controls whether @value{GDBN} will attempt to alter the contents
5440 of memory, such as with assignment expressions in @code{print}. It
5441 defaults to @code{on}.
5443 @item show may-write-memory
5444 Show the current permission to write memory.
5446 @kindex may-insert-breakpoints
5447 @item set may-insert-breakpoints on
5448 @itemx set may-insert-breakpoints off
5449 This controls whether @value{GDBN} will attempt to insert breakpoints.
5450 This affects all breakpoints, including internal breakpoints defined
5451 by @value{GDBN}. It defaults to @code{on}.
5453 @item show may-insert-breakpoints
5454 Show the current permission to insert breakpoints.
5456 @kindex may-insert-tracepoints
5457 @item set may-insert-tracepoints on
5458 @itemx set may-insert-tracepoints off
5459 This controls whether @value{GDBN} will attempt to insert (regular)
5460 tracepoints at the beginning of a tracing experiment. It affects only
5461 non-fast tracepoints, fast tracepoints being under the control of
5462 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5464 @item show may-insert-tracepoints
5465 Show the current permission to insert tracepoints.
5467 @kindex may-insert-fast-tracepoints
5468 @item set may-insert-fast-tracepoints on
5469 @itemx set may-insert-fast-tracepoints off
5470 This controls whether @value{GDBN} will attempt to insert fast
5471 tracepoints at the beginning of a tracing experiment. It affects only
5472 fast tracepoints, regular (non-fast) tracepoints being under the
5473 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5475 @item show may-insert-fast-tracepoints
5476 Show the current permission to insert fast tracepoints.
5478 @kindex may-interrupt
5479 @item set may-interrupt on
5480 @itemx set may-interrupt off
5481 This controls whether @value{GDBN} will attempt to interrupt or stop
5482 program execution. When this variable is @code{off}, the
5483 @code{interrupt} command will have no effect, nor will
5484 @kbd{Ctrl-c}. It defaults to @code{on}.
5486 @item show may-interrupt
5487 Show the current permission to interrupt or stop the program.
5491 @node Reverse Execution
5492 @chapter Running programs backward
5493 @cindex reverse execution
5494 @cindex running programs backward
5496 When you are debugging a program, it is not unusual to realize that
5497 you have gone too far, and some event of interest has already happened.
5498 If the target environment supports it, @value{GDBN} can allow you to
5499 ``rewind'' the program by running it backward.
5501 A target environment that supports reverse execution should be able
5502 to ``undo'' the changes in machine state that have taken place as the
5503 program was executing normally. Variables, registers etc.@: should
5504 revert to their previous values. Obviously this requires a great
5505 deal of sophistication on the part of the target environment; not
5506 all target environments can support reverse execution.
5508 When a program is executed in reverse, the instructions that
5509 have most recently been executed are ``un-executed'', in reverse
5510 order. The program counter runs backward, following the previous
5511 thread of execution in reverse. As each instruction is ``un-executed'',
5512 the values of memory and/or registers that were changed by that
5513 instruction are reverted to their previous states. After executing
5514 a piece of source code in reverse, all side effects of that code
5515 should be ``undone'', and all variables should be returned to their
5516 prior values@footnote{
5517 Note that some side effects are easier to undo than others. For instance,
5518 memory and registers are relatively easy, but device I/O is hard. Some
5519 targets may be able undo things like device I/O, and some may not.
5521 The contract between @value{GDBN} and the reverse executing target
5522 requires only that the target do something reasonable when
5523 @value{GDBN} tells it to execute backwards, and then report the
5524 results back to @value{GDBN}. Whatever the target reports back to
5525 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5526 assumes that the memory and registers that the target reports are in a
5527 consistant state, but @value{GDBN} accepts whatever it is given.
5530 If you are debugging in a target environment that supports
5531 reverse execution, @value{GDBN} provides the following commands.
5534 @kindex reverse-continue
5535 @kindex rc @r{(@code{reverse-continue})}
5536 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5537 @itemx rc @r{[}@var{ignore-count}@r{]}
5538 Beginning at the point where your program last stopped, start executing
5539 in reverse. Reverse execution will stop for breakpoints and synchronous
5540 exceptions (signals), just like normal execution. Behavior of
5541 asynchronous signals depends on the target environment.
5543 @kindex reverse-step
5544 @kindex rs @r{(@code{step})}
5545 @item reverse-step @r{[}@var{count}@r{]}
5546 Run the program backward until control reaches the start of a
5547 different source line; then stop it, and return control to @value{GDBN}.
5549 Like the @code{step} command, @code{reverse-step} will only stop
5550 at the beginning of a source line. It ``un-executes'' the previously
5551 executed source line. If the previous source line included calls to
5552 debuggable functions, @code{reverse-step} will step (backward) into
5553 the called function, stopping at the beginning of the @emph{last}
5554 statement in the called function (typically a return statement).
5556 Also, as with the @code{step} command, if non-debuggable functions are
5557 called, @code{reverse-step} will run thru them backward without stopping.
5559 @kindex reverse-stepi
5560 @kindex rsi @r{(@code{reverse-stepi})}
5561 @item reverse-stepi @r{[}@var{count}@r{]}
5562 Reverse-execute one machine instruction. Note that the instruction
5563 to be reverse-executed is @emph{not} the one pointed to by the program
5564 counter, but the instruction executed prior to that one. For instance,
5565 if the last instruction was a jump, @code{reverse-stepi} will take you
5566 back from the destination of the jump to the jump instruction itself.
5568 @kindex reverse-next
5569 @kindex rn @r{(@code{reverse-next})}
5570 @item reverse-next @r{[}@var{count}@r{]}
5571 Run backward to the beginning of the previous line executed in
5572 the current (innermost) stack frame. If the line contains function
5573 calls, they will be ``un-executed'' without stopping. Starting from
5574 the first line of a function, @code{reverse-next} will take you back
5575 to the caller of that function, @emph{before} the function was called,
5576 just as the normal @code{next} command would take you from the last
5577 line of a function back to its return to its caller
5578 @footnote{Unless the code is too heavily optimized.}.
5580 @kindex reverse-nexti
5581 @kindex rni @r{(@code{reverse-nexti})}
5582 @item reverse-nexti @r{[}@var{count}@r{]}
5583 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5584 in reverse, except that called functions are ``un-executed'' atomically.
5585 That is, if the previously executed instruction was a return from
5586 another function, @code{reverse-nexti} will continue to execute
5587 in reverse until the call to that function (from the current stack
5590 @kindex reverse-finish
5591 @item reverse-finish
5592 Just as the @code{finish} command takes you to the point where the
5593 current function returns, @code{reverse-finish} takes you to the point
5594 where it was called. Instead of ending up at the end of the current
5595 function invocation, you end up at the beginning.
5597 @kindex set exec-direction
5598 @item set exec-direction
5599 Set the direction of target execution.
5600 @itemx set exec-direction reverse
5601 @cindex execute forward or backward in time
5602 @value{GDBN} will perform all execution commands in reverse, until the
5603 exec-direction mode is changed to ``forward''. Affected commands include
5604 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5605 command cannot be used in reverse mode.
5606 @item set exec-direction forward
5607 @value{GDBN} will perform all execution commands in the normal fashion.
5608 This is the default.
5612 @node Process Record and Replay
5613 @chapter Recording Inferior's Execution and Replaying It
5614 @cindex process record and replay
5615 @cindex recording inferior's execution and replaying it
5617 On some platforms, @value{GDBN} provides a special @dfn{process record
5618 and replay} target that can record a log of the process execution, and
5619 replay it later with both forward and reverse execution commands.
5622 When this target is in use, if the execution log includes the record
5623 for the next instruction, @value{GDBN} will debug in @dfn{replay
5624 mode}. In the replay mode, the inferior does not really execute code
5625 instructions. Instead, all the events that normally happen during
5626 code execution are taken from the execution log. While code is not
5627 really executed in replay mode, the values of registers (including the
5628 program counter register) and the memory of the inferior are still
5629 changed as they normally would. Their contents are taken from the
5633 If the record for the next instruction is not in the execution log,
5634 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5635 inferior executes normally, and @value{GDBN} records the execution log
5638 The process record and replay target supports reverse execution
5639 (@pxref{Reverse Execution}), even if the platform on which the
5640 inferior runs does not. However, the reverse execution is limited in
5641 this case by the range of the instructions recorded in the execution
5642 log. In other words, reverse execution on platforms that don't
5643 support it directly can only be done in the replay mode.
5645 When debugging in the reverse direction, @value{GDBN} will work in
5646 replay mode as long as the execution log includes the record for the
5647 previous instruction; otherwise, it will work in record mode, if the
5648 platform supports reverse execution, or stop if not.
5650 For architecture environments that support process record and replay,
5651 @value{GDBN} provides the following commands:
5654 @kindex target record
5658 This command starts the process record and replay target. The process
5659 record and replay target can only debug a process that is already
5660 running. Therefore, you need first to start the process with the
5661 @kbd{run} or @kbd{start} commands, and then start the recording with
5662 the @kbd{target record} command.
5664 Both @code{record} and @code{rec} are aliases of @code{target record}.
5666 @cindex displaced stepping, and process record and replay
5667 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5668 will be automatically disabled when process record and replay target
5669 is started. That's because the process record and replay target
5670 doesn't support displaced stepping.
5672 @cindex non-stop mode, and process record and replay
5673 @cindex asynchronous execution, and process record and replay
5674 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5675 the asynchronous execution mode (@pxref{Background Execution}), the
5676 process record and replay target cannot be started because it doesn't
5677 support these two modes.
5682 Stop the process record and replay target. When process record and
5683 replay target stops, the entire execution log will be deleted and the
5684 inferior will either be terminated, or will remain in its final state.
5686 When you stop the process record and replay target in record mode (at
5687 the end of the execution log), the inferior will be stopped at the
5688 next instruction that would have been recorded. In other words, if
5689 you record for a while and then stop recording, the inferior process
5690 will be left in the same state as if the recording never happened.
5692 On the other hand, if the process record and replay target is stopped
5693 while in replay mode (that is, not at the end of the execution log,
5694 but at some earlier point), the inferior process will become ``live''
5695 at that earlier state, and it will then be possible to continue the
5696 usual ``live'' debugging of the process from that state.
5698 When the inferior process exits, or @value{GDBN} detaches from it,
5699 process record and replay target will automatically stop itself.
5702 @item record save @var{filename}
5703 Save the execution log to a file @file{@var{filename}}.
5704 Default filename is @file{gdb_record.@var{process_id}}, where
5705 @var{process_id} is the process ID of the inferior.
5707 @kindex record restore
5708 @item record restore @var{filename}
5709 Restore the execution log from a file @file{@var{filename}}.
5710 File must have been created with @code{record save}.
5712 @kindex set record insn-number-max
5713 @item set record insn-number-max @var{limit}
5714 Set the limit of instructions to be recorded. Default value is 200000.
5716 If @var{limit} is a positive number, then @value{GDBN} will start
5717 deleting instructions from the log once the number of the record
5718 instructions becomes greater than @var{limit}. For every new recorded
5719 instruction, @value{GDBN} will delete the earliest recorded
5720 instruction to keep the number of recorded instructions at the limit.
5721 (Since deleting recorded instructions loses information, @value{GDBN}
5722 lets you control what happens when the limit is reached, by means of
5723 the @code{stop-at-limit} option, described below.)
5725 If @var{limit} is zero, @value{GDBN} will never delete recorded
5726 instructions from the execution log. The number of recorded
5727 instructions is unlimited in this case.
5729 @kindex show record insn-number-max
5730 @item show record insn-number-max
5731 Show the limit of instructions to be recorded.
5733 @kindex set record stop-at-limit
5734 @item set record stop-at-limit
5735 Control the behavior when the number of recorded instructions reaches
5736 the limit. If ON (the default), @value{GDBN} will stop when the limit
5737 is reached for the first time and ask you whether you want to stop the
5738 inferior or continue running it and recording the execution log. If
5739 you decide to continue recording, each new recorded instruction will
5740 cause the oldest one to be deleted.
5742 If this option is OFF, @value{GDBN} will automatically delete the
5743 oldest record to make room for each new one, without asking.
5745 @kindex show record stop-at-limit
5746 @item show record stop-at-limit
5747 Show the current setting of @code{stop-at-limit}.
5749 @kindex set record memory-query
5750 @item set record memory-query
5751 Control the behavior when @value{GDBN} is unable to record memory
5752 changes caused by an instruction. If ON, @value{GDBN} will query
5753 whether to stop the inferior in that case.
5755 If this option is OFF (the default), @value{GDBN} will automatically
5756 ignore the effect of such instructions on memory. Later, when
5757 @value{GDBN} replays this execution log, it will mark the log of this
5758 instruction as not accessible, and it will not affect the replay
5761 @kindex show record memory-query
5762 @item show record memory-query
5763 Show the current setting of @code{memory-query}.
5767 Show various statistics about the state of process record and its
5768 in-memory execution log buffer, including:
5772 Whether in record mode or replay mode.
5774 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5776 Highest recorded instruction number.
5778 Current instruction about to be replayed (if in replay mode).
5780 Number of instructions contained in the execution log.
5782 Maximum number of instructions that may be contained in the execution log.
5785 @kindex record delete
5788 When record target runs in replay mode (``in the past''), delete the
5789 subsequent execution log and begin to record a new execution log starting
5790 from the current address. This means you will abandon the previously
5791 recorded ``future'' and begin recording a new ``future''.
5796 @chapter Examining the Stack
5798 When your program has stopped, the first thing you need to know is where it
5799 stopped and how it got there.
5802 Each time your program performs a function call, information about the call
5804 That information includes the location of the call in your program,
5805 the arguments of the call,
5806 and the local variables of the function being called.
5807 The information is saved in a block of data called a @dfn{stack frame}.
5808 The stack frames are allocated in a region of memory called the @dfn{call
5811 When your program stops, the @value{GDBN} commands for examining the
5812 stack allow you to see all of this information.
5814 @cindex selected frame
5815 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5816 @value{GDBN} commands refer implicitly to the selected frame. In
5817 particular, whenever you ask @value{GDBN} for the value of a variable in
5818 your program, the value is found in the selected frame. There are
5819 special @value{GDBN} commands to select whichever frame you are
5820 interested in. @xref{Selection, ,Selecting a Frame}.
5822 When your program stops, @value{GDBN} automatically selects the
5823 currently executing frame and describes it briefly, similar to the
5824 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5827 * Frames:: Stack frames
5828 * Backtrace:: Backtraces
5829 * Selection:: Selecting a frame
5830 * Frame Info:: Information on a frame
5835 @section Stack Frames
5837 @cindex frame, definition
5839 The call stack is divided up into contiguous pieces called @dfn{stack
5840 frames}, or @dfn{frames} for short; each frame is the data associated
5841 with one call to one function. The frame contains the arguments given
5842 to the function, the function's local variables, and the address at
5843 which the function is executing.
5845 @cindex initial frame
5846 @cindex outermost frame
5847 @cindex innermost frame
5848 When your program is started, the stack has only one frame, that of the
5849 function @code{main}. This is called the @dfn{initial} frame or the
5850 @dfn{outermost} frame. Each time a function is called, a new frame is
5851 made. Each time a function returns, the frame for that function invocation
5852 is eliminated. If a function is recursive, there can be many frames for
5853 the same function. The frame for the function in which execution is
5854 actually occurring is called the @dfn{innermost} frame. This is the most
5855 recently created of all the stack frames that still exist.
5857 @cindex frame pointer
5858 Inside your program, stack frames are identified by their addresses. A
5859 stack frame consists of many bytes, each of which has its own address; each
5860 kind of computer has a convention for choosing one byte whose
5861 address serves as the address of the frame. Usually this address is kept
5862 in a register called the @dfn{frame pointer register}
5863 (@pxref{Registers, $fp}) while execution is going on in that frame.
5865 @cindex frame number
5866 @value{GDBN} assigns numbers to all existing stack frames, starting with
5867 zero for the innermost frame, one for the frame that called it,
5868 and so on upward. These numbers do not really exist in your program;
5869 they are assigned by @value{GDBN} to give you a way of designating stack
5870 frames in @value{GDBN} commands.
5872 @c The -fomit-frame-pointer below perennially causes hbox overflow
5873 @c underflow problems.
5874 @cindex frameless execution
5875 Some compilers provide a way to compile functions so that they operate
5876 without stack frames. (For example, the @value{NGCC} option
5878 @samp{-fomit-frame-pointer}
5880 generates functions without a frame.)
5881 This is occasionally done with heavily used library functions to save
5882 the frame setup time. @value{GDBN} has limited facilities for dealing
5883 with these function invocations. If the innermost function invocation
5884 has no stack frame, @value{GDBN} nevertheless regards it as though
5885 it had a separate frame, which is numbered zero as usual, allowing
5886 correct tracing of the function call chain. However, @value{GDBN} has
5887 no provision for frameless functions elsewhere in the stack.
5890 @kindex frame@r{, command}
5891 @cindex current stack frame
5892 @item frame @var{args}
5893 The @code{frame} command allows you to move from one stack frame to another,
5894 and to print the stack frame you select. @var{args} may be either the
5895 address of the frame or the stack frame number. Without an argument,
5896 @code{frame} prints the current stack frame.
5898 @kindex select-frame
5899 @cindex selecting frame silently
5901 The @code{select-frame} command allows you to move from one stack frame
5902 to another without printing the frame. This is the silent version of
5910 @cindex call stack traces
5911 A backtrace is a summary of how your program got where it is. It shows one
5912 line per frame, for many frames, starting with the currently executing
5913 frame (frame zero), followed by its caller (frame one), and on up the
5918 @kindex bt @r{(@code{backtrace})}
5921 Print a backtrace of the entire stack: one line per frame for all
5922 frames in the stack.
5924 You can stop the backtrace at any time by typing the system interrupt
5925 character, normally @kbd{Ctrl-c}.
5927 @item backtrace @var{n}
5929 Similar, but print only the innermost @var{n} frames.
5931 @item backtrace -@var{n}
5933 Similar, but print only the outermost @var{n} frames.
5935 @item backtrace full
5937 @itemx bt full @var{n}
5938 @itemx bt full -@var{n}
5939 Print the values of the local variables also. @var{n} specifies the
5940 number of frames to print, as described above.
5945 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5946 are additional aliases for @code{backtrace}.
5948 @cindex multiple threads, backtrace
5949 In a multi-threaded program, @value{GDBN} by default shows the
5950 backtrace only for the current thread. To display the backtrace for
5951 several or all of the threads, use the command @code{thread apply}
5952 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5953 apply all backtrace}, @value{GDBN} will display the backtrace for all
5954 the threads; this is handy when you debug a core dump of a
5955 multi-threaded program.
5957 Each line in the backtrace shows the frame number and the function name.
5958 The program counter value is also shown---unless you use @code{set
5959 print address off}. The backtrace also shows the source file name and
5960 line number, as well as the arguments to the function. The program
5961 counter value is omitted if it is at the beginning of the code for that
5964 Here is an example of a backtrace. It was made with the command
5965 @samp{bt 3}, so it shows the innermost three frames.
5969 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5971 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5972 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5974 (More stack frames follow...)
5979 The display for frame zero does not begin with a program counter
5980 value, indicating that your program has stopped at the beginning of the
5981 code for line @code{993} of @code{builtin.c}.
5984 The value of parameter @code{data} in frame 1 has been replaced by
5985 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5986 only if it is a scalar (integer, pointer, enumeration, etc). See command
5987 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5988 on how to configure the way function parameter values are printed.
5990 @cindex optimized out, in backtrace
5991 @cindex function call arguments, optimized out
5992 If your program was compiled with optimizations, some compilers will
5993 optimize away arguments passed to functions if those arguments are
5994 never used after the call. Such optimizations generate code that
5995 passes arguments through registers, but doesn't store those arguments
5996 in the stack frame. @value{GDBN} has no way of displaying such
5997 arguments in stack frames other than the innermost one. Here's what
5998 such a backtrace might look like:
6002 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6004 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6005 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6007 (More stack frames follow...)
6012 The values of arguments that were not saved in their stack frames are
6013 shown as @samp{<optimized out>}.
6015 If you need to display the values of such optimized-out arguments,
6016 either deduce that from other variables whose values depend on the one
6017 you are interested in, or recompile without optimizations.
6019 @cindex backtrace beyond @code{main} function
6020 @cindex program entry point
6021 @cindex startup code, and backtrace
6022 Most programs have a standard user entry point---a place where system
6023 libraries and startup code transition into user code. For C this is
6024 @code{main}@footnote{
6025 Note that embedded programs (the so-called ``free-standing''
6026 environment) are not required to have a @code{main} function as the
6027 entry point. They could even have multiple entry points.}.
6028 When @value{GDBN} finds the entry function in a backtrace
6029 it will terminate the backtrace, to avoid tracing into highly
6030 system-specific (and generally uninteresting) code.
6032 If you need to examine the startup code, or limit the number of levels
6033 in a backtrace, you can change this behavior:
6036 @item set backtrace past-main
6037 @itemx set backtrace past-main on
6038 @kindex set backtrace
6039 Backtraces will continue past the user entry point.
6041 @item set backtrace past-main off
6042 Backtraces will stop when they encounter the user entry point. This is the
6045 @item show backtrace past-main
6046 @kindex show backtrace
6047 Display the current user entry point backtrace policy.
6049 @item set backtrace past-entry
6050 @itemx set backtrace past-entry on
6051 Backtraces will continue past the internal entry point of an application.
6052 This entry point is encoded by the linker when the application is built,
6053 and is likely before the user entry point @code{main} (or equivalent) is called.
6055 @item set backtrace past-entry off
6056 Backtraces will stop when they encounter the internal entry point of an
6057 application. This is the default.
6059 @item show backtrace past-entry
6060 Display the current internal entry point backtrace policy.
6062 @item set backtrace limit @var{n}
6063 @itemx set backtrace limit 0
6064 @cindex backtrace limit
6065 Limit the backtrace to @var{n} levels. A value of zero means
6068 @item show backtrace limit
6069 Display the current limit on backtrace levels.
6073 @section Selecting a Frame
6075 Most commands for examining the stack and other data in your program work on
6076 whichever stack frame is selected at the moment. Here are the commands for
6077 selecting a stack frame; all of them finish by printing a brief description
6078 of the stack frame just selected.
6081 @kindex frame@r{, selecting}
6082 @kindex f @r{(@code{frame})}
6085 Select frame number @var{n}. Recall that frame zero is the innermost
6086 (currently executing) frame, frame one is the frame that called the
6087 innermost one, and so on. The highest-numbered frame is the one for
6090 @item frame @var{addr}
6092 Select the frame at address @var{addr}. This is useful mainly if the
6093 chaining of stack frames has been damaged by a bug, making it
6094 impossible for @value{GDBN} to assign numbers properly to all frames. In
6095 addition, this can be useful when your program has multiple stacks and
6096 switches between them.
6098 On the SPARC architecture, @code{frame} needs two addresses to
6099 select an arbitrary frame: a frame pointer and a stack pointer.
6101 On the MIPS and Alpha architecture, it needs two addresses: a stack
6102 pointer and a program counter.
6104 On the 29k architecture, it needs three addresses: a register stack
6105 pointer, a program counter, and a memory stack pointer.
6109 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6110 advances toward the outermost frame, to higher frame numbers, to frames
6111 that have existed longer. @var{n} defaults to one.
6114 @kindex do @r{(@code{down})}
6116 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6117 advances toward the innermost frame, to lower frame numbers, to frames
6118 that were created more recently. @var{n} defaults to one. You may
6119 abbreviate @code{down} as @code{do}.
6122 All of these commands end by printing two lines of output describing the
6123 frame. The first line shows the frame number, the function name, the
6124 arguments, and the source file and line number of execution in that
6125 frame. The second line shows the text of that source line.
6133 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6135 10 read_input_file (argv[i]);
6139 After such a printout, the @code{list} command with no arguments
6140 prints ten lines centered on the point of execution in the frame.
6141 You can also edit the program at the point of execution with your favorite
6142 editing program by typing @code{edit}.
6143 @xref{List, ,Printing Source Lines},
6147 @kindex down-silently
6149 @item up-silently @var{n}
6150 @itemx down-silently @var{n}
6151 These two commands are variants of @code{up} and @code{down},
6152 respectively; they differ in that they do their work silently, without
6153 causing display of the new frame. They are intended primarily for use
6154 in @value{GDBN} command scripts, where the output might be unnecessary and
6159 @section Information About a Frame
6161 There are several other commands to print information about the selected
6167 When used without any argument, this command does not change which
6168 frame is selected, but prints a brief description of the currently
6169 selected stack frame. It can be abbreviated @code{f}. With an
6170 argument, this command is used to select a stack frame.
6171 @xref{Selection, ,Selecting a Frame}.
6174 @kindex info f @r{(@code{info frame})}
6177 This command prints a verbose description of the selected stack frame,
6182 the address of the frame
6184 the address of the next frame down (called by this frame)
6186 the address of the next frame up (caller of this frame)
6188 the language in which the source code corresponding to this frame is written
6190 the address of the frame's arguments
6192 the address of the frame's local variables
6194 the program counter saved in it (the address of execution in the caller frame)
6196 which registers were saved in the frame
6199 @noindent The verbose description is useful when
6200 something has gone wrong that has made the stack format fail to fit
6201 the usual conventions.
6203 @item info frame @var{addr}
6204 @itemx info f @var{addr}
6205 Print a verbose description of the frame at address @var{addr}, without
6206 selecting that frame. The selected frame remains unchanged by this
6207 command. This requires the same kind of address (more than one for some
6208 architectures) that you specify in the @code{frame} command.
6209 @xref{Selection, ,Selecting a Frame}.
6213 Print the arguments of the selected frame, each on a separate line.
6217 Print the local variables of the selected frame, each on a separate
6218 line. These are all variables (declared either static or automatic)
6219 accessible at the point of execution of the selected frame.
6222 @cindex catch exceptions, list active handlers
6223 @cindex exception handlers, how to list
6225 Print a list of all the exception handlers that are active in the
6226 current stack frame at the current point of execution. To see other
6227 exception handlers, visit the associated frame (using the @code{up},
6228 @code{down}, or @code{frame} commands); then type @code{info catch}.
6229 @xref{Set Catchpoints, , Setting Catchpoints}.
6235 @chapter Examining Source Files
6237 @value{GDBN} can print parts of your program's source, since the debugging
6238 information recorded in the program tells @value{GDBN} what source files were
6239 used to build it. When your program stops, @value{GDBN} spontaneously prints
6240 the line where it stopped. Likewise, when you select a stack frame
6241 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6242 execution in that frame has stopped. You can print other portions of
6243 source files by explicit command.
6245 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6246 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6247 @value{GDBN} under @sc{gnu} Emacs}.
6250 * List:: Printing source lines
6251 * Specify Location:: How to specify code locations
6252 * Edit:: Editing source files
6253 * Search:: Searching source files
6254 * Source Path:: Specifying source directories
6255 * Machine Code:: Source and machine code
6259 @section Printing Source Lines
6262 @kindex l @r{(@code{list})}
6263 To print lines from a source file, use the @code{list} command
6264 (abbreviated @code{l}). By default, ten lines are printed.
6265 There are several ways to specify what part of the file you want to
6266 print; see @ref{Specify Location}, for the full list.
6268 Here are the forms of the @code{list} command most commonly used:
6271 @item list @var{linenum}
6272 Print lines centered around line number @var{linenum} in the
6273 current source file.
6275 @item list @var{function}
6276 Print lines centered around the beginning of function
6280 Print more lines. If the last lines printed were printed with a
6281 @code{list} command, this prints lines following the last lines
6282 printed; however, if the last line printed was a solitary line printed
6283 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6284 Stack}), this prints lines centered around that line.
6287 Print lines just before the lines last printed.
6290 @cindex @code{list}, how many lines to display
6291 By default, @value{GDBN} prints ten source lines with any of these forms of
6292 the @code{list} command. You can change this using @code{set listsize}:
6295 @kindex set listsize
6296 @item set listsize @var{count}
6297 Make the @code{list} command display @var{count} source lines (unless
6298 the @code{list} argument explicitly specifies some other number).
6300 @kindex show listsize
6302 Display the number of lines that @code{list} prints.
6305 Repeating a @code{list} command with @key{RET} discards the argument,
6306 so it is equivalent to typing just @code{list}. This is more useful
6307 than listing the same lines again. An exception is made for an
6308 argument of @samp{-}; that argument is preserved in repetition so that
6309 each repetition moves up in the source file.
6311 In general, the @code{list} command expects you to supply zero, one or two
6312 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6313 of writing them (@pxref{Specify Location}), but the effect is always
6314 to specify some source line.
6316 Here is a complete description of the possible arguments for @code{list}:
6319 @item list @var{linespec}
6320 Print lines centered around the line specified by @var{linespec}.
6322 @item list @var{first},@var{last}
6323 Print lines from @var{first} to @var{last}. Both arguments are
6324 linespecs. When a @code{list} command has two linespecs, and the
6325 source file of the second linespec is omitted, this refers to
6326 the same source file as the first linespec.
6328 @item list ,@var{last}
6329 Print lines ending with @var{last}.
6331 @item list @var{first},
6332 Print lines starting with @var{first}.
6335 Print lines just after the lines last printed.
6338 Print lines just before the lines last printed.
6341 As described in the preceding table.
6344 @node Specify Location
6345 @section Specifying a Location
6346 @cindex specifying location
6349 Several @value{GDBN} commands accept arguments that specify a location
6350 of your program's code. Since @value{GDBN} is a source-level
6351 debugger, a location usually specifies some line in the source code;
6352 for that reason, locations are also known as @dfn{linespecs}.
6354 Here are all the different ways of specifying a code location that
6355 @value{GDBN} understands:
6359 Specifies the line number @var{linenum} of the current source file.
6362 @itemx +@var{offset}
6363 Specifies the line @var{offset} lines before or after the @dfn{current
6364 line}. For the @code{list} command, the current line is the last one
6365 printed; for the breakpoint commands, this is the line at which
6366 execution stopped in the currently selected @dfn{stack frame}
6367 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6368 used as the second of the two linespecs in a @code{list} command,
6369 this specifies the line @var{offset} lines up or down from the first
6372 @item @var{filename}:@var{linenum}
6373 Specifies the line @var{linenum} in the source file @var{filename}.
6375 @item @var{function}
6376 Specifies the line that begins the body of the function @var{function}.
6377 For example, in C, this is the line with the open brace.
6379 @item @var{function}:@var{label}
6380 Specifies the line where @var{label} appears in @var{function}.
6382 @item @var{filename}:@var{function}
6383 Specifies the line that begins the body of the function @var{function}
6384 in the file @var{filename}. You only need the file name with a
6385 function name to avoid ambiguity when there are identically named
6386 functions in different source files.
6389 Specifies the line at which the label named @var{label} appears.
6390 @value{GDBN} searches for the label in the function corresponding to
6391 the currently selected stack frame. If there is no current selected
6392 stack frame (for instance, if the inferior is not running), then
6393 @value{GDBN} will not search for a label.
6395 @item *@var{address}
6396 Specifies the program address @var{address}. For line-oriented
6397 commands, such as @code{list} and @code{edit}, this specifies a source
6398 line that contains @var{address}. For @code{break} and other
6399 breakpoint oriented commands, this can be used to set breakpoints in
6400 parts of your program which do not have debugging information or
6403 Here @var{address} may be any expression valid in the current working
6404 language (@pxref{Languages, working language}) that specifies a code
6405 address. In addition, as a convenience, @value{GDBN} extends the
6406 semantics of expressions used in locations to cover the situations
6407 that frequently happen during debugging. Here are the various forms
6411 @item @var{expression}
6412 Any expression valid in the current working language.
6414 @item @var{funcaddr}
6415 An address of a function or procedure derived from its name. In C,
6416 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6417 simply the function's name @var{function} (and actually a special case
6418 of a valid expression). In Pascal and Modula-2, this is
6419 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6420 (although the Pascal form also works).
6422 This form specifies the address of the function's first instruction,
6423 before the stack frame and arguments have been set up.
6425 @item '@var{filename}'::@var{funcaddr}
6426 Like @var{funcaddr} above, but also specifies the name of the source
6427 file explicitly. This is useful if the name of the function does not
6428 specify the function unambiguously, e.g., if there are several
6429 functions with identical names in different source files.
6436 @section Editing Source Files
6437 @cindex editing source files
6440 @kindex e @r{(@code{edit})}
6441 To edit the lines in a source file, use the @code{edit} command.
6442 The editing program of your choice
6443 is invoked with the current line set to
6444 the active line in the program.
6445 Alternatively, there are several ways to specify what part of the file you
6446 want to print if you want to see other parts of the program:
6449 @item edit @var{location}
6450 Edit the source file specified by @code{location}. Editing starts at
6451 that @var{location}, e.g., at the specified source line of the
6452 specified file. @xref{Specify Location}, for all the possible forms
6453 of the @var{location} argument; here are the forms of the @code{edit}
6454 command most commonly used:
6457 @item edit @var{number}
6458 Edit the current source file with @var{number} as the active line number.
6460 @item edit @var{function}
6461 Edit the file containing @var{function} at the beginning of its definition.
6466 @subsection Choosing your Editor
6467 You can customize @value{GDBN} to use any editor you want
6469 The only restriction is that your editor (say @code{ex}), recognizes the
6470 following command-line syntax:
6472 ex +@var{number} file
6474 The optional numeric value +@var{number} specifies the number of the line in
6475 the file where to start editing.}.
6476 By default, it is @file{@value{EDITOR}}, but you can change this
6477 by setting the environment variable @code{EDITOR} before using
6478 @value{GDBN}. For example, to configure @value{GDBN} to use the
6479 @code{vi} editor, you could use these commands with the @code{sh} shell:
6485 or in the @code{csh} shell,
6487 setenv EDITOR /usr/bin/vi
6492 @section Searching Source Files
6493 @cindex searching source files
6495 There are two commands for searching through the current source file for a
6500 @kindex forward-search
6501 @item forward-search @var{regexp}
6502 @itemx search @var{regexp}
6503 The command @samp{forward-search @var{regexp}} checks each line,
6504 starting with the one following the last line listed, for a match for
6505 @var{regexp}. It lists the line that is found. You can use the
6506 synonym @samp{search @var{regexp}} or abbreviate the command name as
6509 @kindex reverse-search
6510 @item reverse-search @var{regexp}
6511 The command @samp{reverse-search @var{regexp}} checks each line, starting
6512 with the one before the last line listed and going backward, for a match
6513 for @var{regexp}. It lists the line that is found. You can abbreviate
6514 this command as @code{rev}.
6518 @section Specifying Source Directories
6521 @cindex directories for source files
6522 Executable programs sometimes do not record the directories of the source
6523 files from which they were compiled, just the names. Even when they do,
6524 the directories could be moved between the compilation and your debugging
6525 session. @value{GDBN} has a list of directories to search for source files;
6526 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6527 it tries all the directories in the list, in the order they are present
6528 in the list, until it finds a file with the desired name.
6530 For example, suppose an executable references the file
6531 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6532 @file{/mnt/cross}. The file is first looked up literally; if this
6533 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6534 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6535 message is printed. @value{GDBN} does not look up the parts of the
6536 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6537 Likewise, the subdirectories of the source path are not searched: if
6538 the source path is @file{/mnt/cross}, and the binary refers to
6539 @file{foo.c}, @value{GDBN} would not find it under
6540 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6542 Plain file names, relative file names with leading directories, file
6543 names containing dots, etc.@: are all treated as described above; for
6544 instance, if the source path is @file{/mnt/cross}, and the source file
6545 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6546 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6547 that---@file{/mnt/cross/foo.c}.
6549 Note that the executable search path is @emph{not} used to locate the
6552 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6553 any information it has cached about where source files are found and where
6554 each line is in the file.
6558 When you start @value{GDBN}, its source path includes only @samp{cdir}
6559 and @samp{cwd}, in that order.
6560 To add other directories, use the @code{directory} command.
6562 The search path is used to find both program source files and @value{GDBN}
6563 script files (read using the @samp{-command} option and @samp{source} command).
6565 In addition to the source path, @value{GDBN} provides a set of commands
6566 that manage a list of source path substitution rules. A @dfn{substitution
6567 rule} specifies how to rewrite source directories stored in the program's
6568 debug information in case the sources were moved to a different
6569 directory between compilation and debugging. A rule is made of
6570 two strings, the first specifying what needs to be rewritten in
6571 the path, and the second specifying how it should be rewritten.
6572 In @ref{set substitute-path}, we name these two parts @var{from} and
6573 @var{to} respectively. @value{GDBN} does a simple string replacement
6574 of @var{from} with @var{to} at the start of the directory part of the
6575 source file name, and uses that result instead of the original file
6576 name to look up the sources.
6578 Using the previous example, suppose the @file{foo-1.0} tree has been
6579 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6580 @value{GDBN} to replace @file{/usr/src} in all source path names with
6581 @file{/mnt/cross}. The first lookup will then be
6582 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6583 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6584 substitution rule, use the @code{set substitute-path} command
6585 (@pxref{set substitute-path}).
6587 To avoid unexpected substitution results, a rule is applied only if the
6588 @var{from} part of the directory name ends at a directory separator.
6589 For instance, a rule substituting @file{/usr/source} into
6590 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6591 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6592 is applied only at the beginning of the directory name, this rule will
6593 not be applied to @file{/root/usr/source/baz.c} either.
6595 In many cases, you can achieve the same result using the @code{directory}
6596 command. However, @code{set substitute-path} can be more efficient in
6597 the case where the sources are organized in a complex tree with multiple
6598 subdirectories. With the @code{directory} command, you need to add each
6599 subdirectory of your project. If you moved the entire tree while
6600 preserving its internal organization, then @code{set substitute-path}
6601 allows you to direct the debugger to all the sources with one single
6604 @code{set substitute-path} is also more than just a shortcut command.
6605 The source path is only used if the file at the original location no
6606 longer exists. On the other hand, @code{set substitute-path} modifies
6607 the debugger behavior to look at the rewritten location instead. So, if
6608 for any reason a source file that is not relevant to your executable is
6609 located at the original location, a substitution rule is the only
6610 method available to point @value{GDBN} at the new location.
6612 @cindex @samp{--with-relocated-sources}
6613 @cindex default source path substitution
6614 You can configure a default source path substitution rule by
6615 configuring @value{GDBN} with the
6616 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6617 should be the name of a directory under @value{GDBN}'s configured
6618 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6619 directory names in debug information under @var{dir} will be adjusted
6620 automatically if the installed @value{GDBN} is moved to a new
6621 location. This is useful if @value{GDBN}, libraries or executables
6622 with debug information and corresponding source code are being moved
6626 @item directory @var{dirname} @dots{}
6627 @item dir @var{dirname} @dots{}
6628 Add directory @var{dirname} to the front of the source path. Several
6629 directory names may be given to this command, separated by @samp{:}
6630 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6631 part of absolute file names) or
6632 whitespace. You may specify a directory that is already in the source
6633 path; this moves it forward, so @value{GDBN} searches it sooner.
6637 @vindex $cdir@r{, convenience variable}
6638 @vindex $cwd@r{, convenience variable}
6639 @cindex compilation directory
6640 @cindex current directory
6641 @cindex working directory
6642 @cindex directory, current
6643 @cindex directory, compilation
6644 You can use the string @samp{$cdir} to refer to the compilation
6645 directory (if one is recorded), and @samp{$cwd} to refer to the current
6646 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6647 tracks the current working directory as it changes during your @value{GDBN}
6648 session, while the latter is immediately expanded to the current
6649 directory at the time you add an entry to the source path.
6652 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6654 @c RET-repeat for @code{directory} is explicitly disabled, but since
6655 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6657 @item set directories @var{path-list}
6658 @kindex set directories
6659 Set the source path to @var{path-list}.
6660 @samp{$cdir:$cwd} are added if missing.
6662 @item show directories
6663 @kindex show directories
6664 Print the source path: show which directories it contains.
6666 @anchor{set substitute-path}
6667 @item set substitute-path @var{from} @var{to}
6668 @kindex set substitute-path
6669 Define a source path substitution rule, and add it at the end of the
6670 current list of existing substitution rules. If a rule with the same
6671 @var{from} was already defined, then the old rule is also deleted.
6673 For example, if the file @file{/foo/bar/baz.c} was moved to
6674 @file{/mnt/cross/baz.c}, then the command
6677 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6681 will tell @value{GDBN} to replace @samp{/usr/src} with
6682 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6683 @file{baz.c} even though it was moved.
6685 In the case when more than one substitution rule have been defined,
6686 the rules are evaluated one by one in the order where they have been
6687 defined. The first one matching, if any, is selected to perform
6690 For instance, if we had entered the following commands:
6693 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6694 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6698 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6699 @file{/mnt/include/defs.h} by using the first rule. However, it would
6700 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6701 @file{/mnt/src/lib/foo.c}.
6704 @item unset substitute-path [path]
6705 @kindex unset substitute-path
6706 If a path is specified, search the current list of substitution rules
6707 for a rule that would rewrite that path. Delete that rule if found.
6708 A warning is emitted by the debugger if no rule could be found.
6710 If no path is specified, then all substitution rules are deleted.
6712 @item show substitute-path [path]
6713 @kindex show substitute-path
6714 If a path is specified, then print the source path substitution rule
6715 which would rewrite that path, if any.
6717 If no path is specified, then print all existing source path substitution
6722 If your source path is cluttered with directories that are no longer of
6723 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6724 versions of source. You can correct the situation as follows:
6728 Use @code{directory} with no argument to reset the source path to its default value.
6731 Use @code{directory} with suitable arguments to reinstall the
6732 directories you want in the source path. You can add all the
6733 directories in one command.
6737 @section Source and Machine Code
6738 @cindex source line and its code address
6740 You can use the command @code{info line} to map source lines to program
6741 addresses (and vice versa), and the command @code{disassemble} to display
6742 a range of addresses as machine instructions. You can use the command
6743 @code{set disassemble-next-line} to set whether to disassemble next
6744 source line when execution stops. When run under @sc{gnu} Emacs
6745 mode, the @code{info line} command causes the arrow to point to the
6746 line specified. Also, @code{info line} prints addresses in symbolic form as
6751 @item info line @var{linespec}
6752 Print the starting and ending addresses of the compiled code for
6753 source line @var{linespec}. You can specify source lines in any of
6754 the ways documented in @ref{Specify Location}.
6757 For example, we can use @code{info line} to discover the location of
6758 the object code for the first line of function
6759 @code{m4_changequote}:
6761 @c FIXME: I think this example should also show the addresses in
6762 @c symbolic form, as they usually would be displayed.
6764 (@value{GDBP}) info line m4_changequote
6765 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6769 @cindex code address and its source line
6770 We can also inquire (using @code{*@var{addr}} as the form for
6771 @var{linespec}) what source line covers a particular address:
6773 (@value{GDBP}) info line *0x63ff
6774 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6777 @cindex @code{$_} and @code{info line}
6778 @cindex @code{x} command, default address
6779 @kindex x@r{(examine), and} info line
6780 After @code{info line}, the default address for the @code{x} command
6781 is changed to the starting address of the line, so that @samp{x/i} is
6782 sufficient to begin examining the machine code (@pxref{Memory,
6783 ,Examining Memory}). Also, this address is saved as the value of the
6784 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6789 @cindex assembly instructions
6790 @cindex instructions, assembly
6791 @cindex machine instructions
6792 @cindex listing machine instructions
6794 @itemx disassemble /m
6795 @itemx disassemble /r
6796 This specialized command dumps a range of memory as machine
6797 instructions. It can also print mixed source+disassembly by specifying
6798 the @code{/m} modifier and print the raw instructions in hex as well as
6799 in symbolic form by specifying the @code{/r}.
6800 The default memory range is the function surrounding the
6801 program counter of the selected frame. A single argument to this
6802 command is a program counter value; @value{GDBN} dumps the function
6803 surrounding this value. When two arguments are given, they should
6804 be separated by a comma, possibly surrounded by whitespace. The
6805 arguments specify a range of addresses to dump, in one of two forms:
6808 @item @var{start},@var{end}
6809 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6810 @item @var{start},+@var{length}
6811 the addresses from @var{start} (inclusive) to
6812 @code{@var{start}+@var{length}} (exclusive).
6816 When 2 arguments are specified, the name of the function is also
6817 printed (since there could be several functions in the given range).
6819 The argument(s) can be any expression yielding a numeric value, such as
6820 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6822 If the range of memory being disassembled contains current program counter,
6823 the instruction at that location is shown with a @code{=>} marker.
6826 The following example shows the disassembly of a range of addresses of
6827 HP PA-RISC 2.0 code:
6830 (@value{GDBP}) disas 0x32c4, 0x32e4
6831 Dump of assembler code from 0x32c4 to 0x32e4:
6832 0x32c4 <main+204>: addil 0,dp
6833 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6834 0x32cc <main+212>: ldil 0x3000,r31
6835 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6836 0x32d4 <main+220>: ldo 0(r31),rp
6837 0x32d8 <main+224>: addil -0x800,dp
6838 0x32dc <main+228>: ldo 0x588(r1),r26
6839 0x32e0 <main+232>: ldil 0x3000,r31
6840 End of assembler dump.
6843 Here is an example showing mixed source+assembly for Intel x86, when the
6844 program is stopped just after function prologue:
6847 (@value{GDBP}) disas /m main
6848 Dump of assembler code for function main:
6850 0x08048330 <+0>: push %ebp
6851 0x08048331 <+1>: mov %esp,%ebp
6852 0x08048333 <+3>: sub $0x8,%esp
6853 0x08048336 <+6>: and $0xfffffff0,%esp
6854 0x08048339 <+9>: sub $0x10,%esp
6856 6 printf ("Hello.\n");
6857 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6858 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6862 0x08048348 <+24>: mov $0x0,%eax
6863 0x0804834d <+29>: leave
6864 0x0804834e <+30>: ret
6866 End of assembler dump.
6869 Here is another example showing raw instructions in hex for AMD x86-64,
6872 (gdb) disas /r 0x400281,+10
6873 Dump of assembler code from 0x400281 to 0x40028b:
6874 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6875 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6876 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6877 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6878 End of assembler dump.
6881 Some architectures have more than one commonly-used set of instruction
6882 mnemonics or other syntax.
6884 For programs that were dynamically linked and use shared libraries,
6885 instructions that call functions or branch to locations in the shared
6886 libraries might show a seemingly bogus location---it's actually a
6887 location of the relocation table. On some architectures, @value{GDBN}
6888 might be able to resolve these to actual function names.
6891 @kindex set disassembly-flavor
6892 @cindex Intel disassembly flavor
6893 @cindex AT&T disassembly flavor
6894 @item set disassembly-flavor @var{instruction-set}
6895 Select the instruction set to use when disassembling the
6896 program via the @code{disassemble} or @code{x/i} commands.
6898 Currently this command is only defined for the Intel x86 family. You
6899 can set @var{instruction-set} to either @code{intel} or @code{att}.
6900 The default is @code{att}, the AT&T flavor used by default by Unix
6901 assemblers for x86-based targets.
6903 @kindex show disassembly-flavor
6904 @item show disassembly-flavor
6905 Show the current setting of the disassembly flavor.
6909 @kindex set disassemble-next-line
6910 @kindex show disassemble-next-line
6911 @item set disassemble-next-line
6912 @itemx show disassemble-next-line
6913 Control whether or not @value{GDBN} will disassemble the next source
6914 line or instruction when execution stops. If ON, @value{GDBN} will
6915 display disassembly of the next source line when execution of the
6916 program being debugged stops. This is @emph{in addition} to
6917 displaying the source line itself, which @value{GDBN} always does if
6918 possible. If the next source line cannot be displayed for some reason
6919 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6920 info in the debug info), @value{GDBN} will display disassembly of the
6921 next @emph{instruction} instead of showing the next source line. If
6922 AUTO, @value{GDBN} will display disassembly of next instruction only
6923 if the source line cannot be displayed. This setting causes
6924 @value{GDBN} to display some feedback when you step through a function
6925 with no line info or whose source file is unavailable. The default is
6926 OFF, which means never display the disassembly of the next line or
6932 @chapter Examining Data
6934 @cindex printing data
6935 @cindex examining data
6938 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6939 @c document because it is nonstandard... Under Epoch it displays in a
6940 @c different window or something like that.
6941 The usual way to examine data in your program is with the @code{print}
6942 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6943 evaluates and prints the value of an expression of the language your
6944 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6945 Different Languages}). It may also print the expression using a
6946 Python-based pretty-printer (@pxref{Pretty Printing}).
6949 @item print @var{expr}
6950 @itemx print /@var{f} @var{expr}
6951 @var{expr} is an expression (in the source language). By default the
6952 value of @var{expr} is printed in a format appropriate to its data type;
6953 you can choose a different format by specifying @samp{/@var{f}}, where
6954 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6958 @itemx print /@var{f}
6959 @cindex reprint the last value
6960 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6961 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6962 conveniently inspect the same value in an alternative format.
6965 A more low-level way of examining data is with the @code{x} command.
6966 It examines data in memory at a specified address and prints it in a
6967 specified format. @xref{Memory, ,Examining Memory}.
6969 If you are interested in information about types, or about how the
6970 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6971 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6975 * Expressions:: Expressions
6976 * Ambiguous Expressions:: Ambiguous Expressions
6977 * Variables:: Program variables
6978 * Arrays:: Artificial arrays
6979 * Output Formats:: Output formats
6980 * Memory:: Examining memory
6981 * Auto Display:: Automatic display
6982 * Print Settings:: Print settings
6983 * Pretty Printing:: Python pretty printing
6984 * Value History:: Value history
6985 * Convenience Vars:: Convenience variables
6986 * Registers:: Registers
6987 * Floating Point Hardware:: Floating point hardware
6988 * Vector Unit:: Vector Unit
6989 * OS Information:: Auxiliary data provided by operating system
6990 * Memory Region Attributes:: Memory region attributes
6991 * Dump/Restore Files:: Copy between memory and a file
6992 * Core File Generation:: Cause a program dump its core
6993 * Character Sets:: Debugging programs that use a different
6994 character set than GDB does
6995 * Caching Remote Data:: Data caching for remote targets
6996 * Searching Memory:: Searching memory for a sequence of bytes
7000 @section Expressions
7003 @code{print} and many other @value{GDBN} commands accept an expression and
7004 compute its value. Any kind of constant, variable or operator defined
7005 by the programming language you are using is valid in an expression in
7006 @value{GDBN}. This includes conditional expressions, function calls,
7007 casts, and string constants. It also includes preprocessor macros, if
7008 you compiled your program to include this information; see
7011 @cindex arrays in expressions
7012 @value{GDBN} supports array constants in expressions input by
7013 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7014 you can use the command @code{print @{1, 2, 3@}} to create an array
7015 of three integers. If you pass an array to a function or assign it
7016 to a program variable, @value{GDBN} copies the array to memory that
7017 is @code{malloc}ed in the target program.
7019 Because C is so widespread, most of the expressions shown in examples in
7020 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7021 Languages}, for information on how to use expressions in other
7024 In this section, we discuss operators that you can use in @value{GDBN}
7025 expressions regardless of your programming language.
7027 @cindex casts, in expressions
7028 Casts are supported in all languages, not just in C, because it is so
7029 useful to cast a number into a pointer in order to examine a structure
7030 at that address in memory.
7031 @c FIXME: casts supported---Mod2 true?
7033 @value{GDBN} supports these operators, in addition to those common
7034 to programming languages:
7038 @samp{@@} is a binary operator for treating parts of memory as arrays.
7039 @xref{Arrays, ,Artificial Arrays}, for more information.
7042 @samp{::} allows you to specify a variable in terms of the file or
7043 function where it is defined. @xref{Variables, ,Program Variables}.
7045 @cindex @{@var{type}@}
7046 @cindex type casting memory
7047 @cindex memory, viewing as typed object
7048 @cindex casts, to view memory
7049 @item @{@var{type}@} @var{addr}
7050 Refers to an object of type @var{type} stored at address @var{addr} in
7051 memory. @var{addr} may be any expression whose value is an integer or
7052 pointer (but parentheses are required around binary operators, just as in
7053 a cast). This construct is allowed regardless of what kind of data is
7054 normally supposed to reside at @var{addr}.
7057 @node Ambiguous Expressions
7058 @section Ambiguous Expressions
7059 @cindex ambiguous expressions
7061 Expressions can sometimes contain some ambiguous elements. For instance,
7062 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7063 a single function name to be defined several times, for application in
7064 different contexts. This is called @dfn{overloading}. Another example
7065 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7066 templates and is typically instantiated several times, resulting in
7067 the same function name being defined in different contexts.
7069 In some cases and depending on the language, it is possible to adjust
7070 the expression to remove the ambiguity. For instance in C@t{++}, you
7071 can specify the signature of the function you want to break on, as in
7072 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7073 qualified name of your function often makes the expression unambiguous
7076 When an ambiguity that needs to be resolved is detected, the debugger
7077 has the capability to display a menu of numbered choices for each
7078 possibility, and then waits for the selection with the prompt @samp{>}.
7079 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7080 aborts the current command. If the command in which the expression was
7081 used allows more than one choice to be selected, the next option in the
7082 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7085 For example, the following session excerpt shows an attempt to set a
7086 breakpoint at the overloaded symbol @code{String::after}.
7087 We choose three particular definitions of that function name:
7089 @c FIXME! This is likely to change to show arg type lists, at least
7092 (@value{GDBP}) b String::after
7095 [2] file:String.cc; line number:867
7096 [3] file:String.cc; line number:860
7097 [4] file:String.cc; line number:875
7098 [5] file:String.cc; line number:853
7099 [6] file:String.cc; line number:846
7100 [7] file:String.cc; line number:735
7102 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7103 Breakpoint 2 at 0xb344: file String.cc, line 875.
7104 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7105 Multiple breakpoints were set.
7106 Use the "delete" command to delete unwanted
7113 @kindex set multiple-symbols
7114 @item set multiple-symbols @var{mode}
7115 @cindex multiple-symbols menu
7117 This option allows you to adjust the debugger behavior when an expression
7120 By default, @var{mode} is set to @code{all}. If the command with which
7121 the expression is used allows more than one choice, then @value{GDBN}
7122 automatically selects all possible choices. For instance, inserting
7123 a breakpoint on a function using an ambiguous name results in a breakpoint
7124 inserted on each possible match. However, if a unique choice must be made,
7125 then @value{GDBN} uses the menu to help you disambiguate the expression.
7126 For instance, printing the address of an overloaded function will result
7127 in the use of the menu.
7129 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7130 when an ambiguity is detected.
7132 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7133 an error due to the ambiguity and the command is aborted.
7135 @kindex show multiple-symbols
7136 @item show multiple-symbols
7137 Show the current value of the @code{multiple-symbols} setting.
7141 @section Program Variables
7143 The most common kind of expression to use is the name of a variable
7146 Variables in expressions are understood in the selected stack frame
7147 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7151 global (or file-static)
7158 visible according to the scope rules of the
7159 programming language from the point of execution in that frame
7162 @noindent This means that in the function
7177 you can examine and use the variable @code{a} whenever your program is
7178 executing within the function @code{foo}, but you can only use or
7179 examine the variable @code{b} while your program is executing inside
7180 the block where @code{b} is declared.
7182 @cindex variable name conflict
7183 There is an exception: you can refer to a variable or function whose
7184 scope is a single source file even if the current execution point is not
7185 in this file. But it is possible to have more than one such variable or
7186 function with the same name (in different source files). If that
7187 happens, referring to that name has unpredictable effects. If you wish,
7188 you can specify a static variable in a particular function or file,
7189 using the colon-colon (@code{::}) notation:
7191 @cindex colon-colon, context for variables/functions
7193 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7194 @cindex @code{::}, context for variables/functions
7197 @var{file}::@var{variable}
7198 @var{function}::@var{variable}
7202 Here @var{file} or @var{function} is the name of the context for the
7203 static @var{variable}. In the case of file names, you can use quotes to
7204 make sure @value{GDBN} parses the file name as a single word---for example,
7205 to print a global value of @code{x} defined in @file{f2.c}:
7208 (@value{GDBP}) p 'f2.c'::x
7211 @cindex C@t{++} scope resolution
7212 This use of @samp{::} is very rarely in conflict with the very similar
7213 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7214 scope resolution operator in @value{GDBN} expressions.
7215 @c FIXME: Um, so what happens in one of those rare cases where it's in
7218 @cindex wrong values
7219 @cindex variable values, wrong
7220 @cindex function entry/exit, wrong values of variables
7221 @cindex optimized code, wrong values of variables
7223 @emph{Warning:} Occasionally, a local variable may appear to have the
7224 wrong value at certain points in a function---just after entry to a new
7225 scope, and just before exit.
7227 You may see this problem when you are stepping by machine instructions.
7228 This is because, on most machines, it takes more than one instruction to
7229 set up a stack frame (including local variable definitions); if you are
7230 stepping by machine instructions, variables may appear to have the wrong
7231 values until the stack frame is completely built. On exit, it usually
7232 also takes more than one machine instruction to destroy a stack frame;
7233 after you begin stepping through that group of instructions, local
7234 variable definitions may be gone.
7236 This may also happen when the compiler does significant optimizations.
7237 To be sure of always seeing accurate values, turn off all optimization
7240 @cindex ``No symbol "foo" in current context''
7241 Another possible effect of compiler optimizations is to optimize
7242 unused variables out of existence, or assign variables to registers (as
7243 opposed to memory addresses). Depending on the support for such cases
7244 offered by the debug info format used by the compiler, @value{GDBN}
7245 might not be able to display values for such local variables. If that
7246 happens, @value{GDBN} will print a message like this:
7249 No symbol "foo" in current context.
7252 To solve such problems, either recompile without optimizations, or use a
7253 different debug info format, if the compiler supports several such
7254 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7255 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7256 produces debug info in a format that is superior to formats such as
7257 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7258 an effective form for debug info. @xref{Debugging Options,,Options
7259 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7260 Compiler Collection (GCC)}.
7261 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7262 that are best suited to C@t{++} programs.
7264 If you ask to print an object whose contents are unknown to
7265 @value{GDBN}, e.g., because its data type is not completely specified
7266 by the debug information, @value{GDBN} will say @samp{<incomplete
7267 type>}. @xref{Symbols, incomplete type}, for more about this.
7269 Strings are identified as arrays of @code{char} values without specified
7270 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7271 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7272 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7273 defines literal string type @code{"char"} as @code{char} without a sign.
7278 signed char var1[] = "A";
7281 You get during debugging
7286 $2 = @{65 'A', 0 '\0'@}
7290 @section Artificial Arrays
7292 @cindex artificial array
7294 @kindex @@@r{, referencing memory as an array}
7295 It is often useful to print out several successive objects of the
7296 same type in memory; a section of an array, or an array of
7297 dynamically determined size for which only a pointer exists in the
7300 You can do this by referring to a contiguous span of memory as an
7301 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7302 operand of @samp{@@} should be the first element of the desired array
7303 and be an individual object. The right operand should be the desired length
7304 of the array. The result is an array value whose elements are all of
7305 the type of the left argument. The first element is actually the left
7306 argument; the second element comes from bytes of memory immediately
7307 following those that hold the first element, and so on. Here is an
7308 example. If a program says
7311 int *array = (int *) malloc (len * sizeof (int));
7315 you can print the contents of @code{array} with
7321 The left operand of @samp{@@} must reside in memory. Array values made
7322 with @samp{@@} in this way behave just like other arrays in terms of
7323 subscripting, and are coerced to pointers when used in expressions.
7324 Artificial arrays most often appear in expressions via the value history
7325 (@pxref{Value History, ,Value History}), after printing one out.
7327 Another way to create an artificial array is to use a cast.
7328 This re-interprets a value as if it were an array.
7329 The value need not be in memory:
7331 (@value{GDBP}) p/x (short[2])0x12345678
7332 $1 = @{0x1234, 0x5678@}
7335 As a convenience, if you leave the array length out (as in
7336 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7337 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7339 (@value{GDBP}) p/x (short[])0x12345678
7340 $2 = @{0x1234, 0x5678@}
7343 Sometimes the artificial array mechanism is not quite enough; in
7344 moderately complex data structures, the elements of interest may not
7345 actually be adjacent---for example, if you are interested in the values
7346 of pointers in an array. One useful work-around in this situation is
7347 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7348 Variables}) as a counter in an expression that prints the first
7349 interesting value, and then repeat that expression via @key{RET}. For
7350 instance, suppose you have an array @code{dtab} of pointers to
7351 structures, and you are interested in the values of a field @code{fv}
7352 in each structure. Here is an example of what you might type:
7362 @node Output Formats
7363 @section Output Formats
7365 @cindex formatted output
7366 @cindex output formats
7367 By default, @value{GDBN} prints a value according to its data type. Sometimes
7368 this is not what you want. For example, you might want to print a number
7369 in hex, or a pointer in decimal. Or you might want to view data in memory
7370 at a certain address as a character string or as an instruction. To do
7371 these things, specify an @dfn{output format} when you print a value.
7373 The simplest use of output formats is to say how to print a value
7374 already computed. This is done by starting the arguments of the
7375 @code{print} command with a slash and a format letter. The format
7376 letters supported are:
7380 Regard the bits of the value as an integer, and print the integer in
7384 Print as integer in signed decimal.
7387 Print as integer in unsigned decimal.
7390 Print as integer in octal.
7393 Print as integer in binary. The letter @samp{t} stands for ``two''.
7394 @footnote{@samp{b} cannot be used because these format letters are also
7395 used with the @code{x} command, where @samp{b} stands for ``byte'';
7396 see @ref{Memory,,Examining Memory}.}
7399 @cindex unknown address, locating
7400 @cindex locate address
7401 Print as an address, both absolute in hexadecimal and as an offset from
7402 the nearest preceding symbol. You can use this format used to discover
7403 where (in what function) an unknown address is located:
7406 (@value{GDBP}) p/a 0x54320
7407 $3 = 0x54320 <_initialize_vx+396>
7411 The command @code{info symbol 0x54320} yields similar results.
7412 @xref{Symbols, info symbol}.
7415 Regard as an integer and print it as a character constant. This
7416 prints both the numerical value and its character representation. The
7417 character representation is replaced with the octal escape @samp{\nnn}
7418 for characters outside the 7-bit @sc{ascii} range.
7420 Without this format, @value{GDBN} displays @code{char},
7421 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7422 constants. Single-byte members of vectors are displayed as integer
7426 Regard the bits of the value as a floating point number and print
7427 using typical floating point syntax.
7430 @cindex printing strings
7431 @cindex printing byte arrays
7432 Regard as a string, if possible. With this format, pointers to single-byte
7433 data are displayed as null-terminated strings and arrays of single-byte data
7434 are displayed as fixed-length strings. Other values are displayed in their
7437 Without this format, @value{GDBN} displays pointers to and arrays of
7438 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7439 strings. Single-byte members of a vector are displayed as an integer
7443 @cindex raw printing
7444 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7445 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7446 Printing}). This typically results in a higher-level display of the
7447 value's contents. The @samp{r} format bypasses any Python
7448 pretty-printer which might exist.
7451 For example, to print the program counter in hex (@pxref{Registers}), type
7458 Note that no space is required before the slash; this is because command
7459 names in @value{GDBN} cannot contain a slash.
7461 To reprint the last value in the value history with a different format,
7462 you can use the @code{print} command with just a format and no
7463 expression. For example, @samp{p/x} reprints the last value in hex.
7466 @section Examining Memory
7468 You can use the command @code{x} (for ``examine'') to examine memory in
7469 any of several formats, independently of your program's data types.
7471 @cindex examining memory
7473 @kindex x @r{(examine memory)}
7474 @item x/@var{nfu} @var{addr}
7477 Use the @code{x} command to examine memory.
7480 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7481 much memory to display and how to format it; @var{addr} is an
7482 expression giving the address where you want to start displaying memory.
7483 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7484 Several commands set convenient defaults for @var{addr}.
7487 @item @var{n}, the repeat count
7488 The repeat count is a decimal integer; the default is 1. It specifies
7489 how much memory (counting by units @var{u}) to display.
7490 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7493 @item @var{f}, the display format
7494 The display format is one of the formats used by @code{print}
7495 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7496 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7497 The default is @samp{x} (hexadecimal) initially. The default changes
7498 each time you use either @code{x} or @code{print}.
7500 @item @var{u}, the unit size
7501 The unit size is any of
7507 Halfwords (two bytes).
7509 Words (four bytes). This is the initial default.
7511 Giant words (eight bytes).
7514 Each time you specify a unit size with @code{x}, that size becomes the
7515 default unit the next time you use @code{x}. For the @samp{i} format,
7516 the unit size is ignored and is normally not written. For the @samp{s} format,
7517 the unit size defaults to @samp{b}, unless it is explicitly given.
7518 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7519 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7520 Note that the results depend on the programming language of the
7521 current compilation unit. If the language is C, the @samp{s}
7522 modifier will use the UTF-16 encoding while @samp{w} will use
7523 UTF-32. The encoding is set by the programming language and cannot
7526 @item @var{addr}, starting display address
7527 @var{addr} is the address where you want @value{GDBN} to begin displaying
7528 memory. The expression need not have a pointer value (though it may);
7529 it is always interpreted as an integer address of a byte of memory.
7530 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7531 @var{addr} is usually just after the last address examined---but several
7532 other commands also set the default address: @code{info breakpoints} (to
7533 the address of the last breakpoint listed), @code{info line} (to the
7534 starting address of a line), and @code{print} (if you use it to display
7535 a value from memory).
7538 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7539 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7540 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7541 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7542 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7544 Since the letters indicating unit sizes are all distinct from the
7545 letters specifying output formats, you do not have to remember whether
7546 unit size or format comes first; either order works. The output
7547 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7548 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7550 Even though the unit size @var{u} is ignored for the formats @samp{s}
7551 and @samp{i}, you might still want to use a count @var{n}; for example,
7552 @samp{3i} specifies that you want to see three machine instructions,
7553 including any operands. For convenience, especially when used with
7554 the @code{display} command, the @samp{i} format also prints branch delay
7555 slot instructions, if any, beyond the count specified, which immediately
7556 follow the last instruction that is within the count. The command
7557 @code{disassemble} gives an alternative way of inspecting machine
7558 instructions; see @ref{Machine Code,,Source and Machine Code}.
7560 All the defaults for the arguments to @code{x} are designed to make it
7561 easy to continue scanning memory with minimal specifications each time
7562 you use @code{x}. For example, after you have inspected three machine
7563 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7564 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7565 the repeat count @var{n} is used again; the other arguments default as
7566 for successive uses of @code{x}.
7568 When examining machine instructions, the instruction at current program
7569 counter is shown with a @code{=>} marker. For example:
7572 (@value{GDBP}) x/5i $pc-6
7573 0x804837f <main+11>: mov %esp,%ebp
7574 0x8048381 <main+13>: push %ecx
7575 0x8048382 <main+14>: sub $0x4,%esp
7576 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7577 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7580 @cindex @code{$_}, @code{$__}, and value history
7581 The addresses and contents printed by the @code{x} command are not saved
7582 in the value history because there is often too much of them and they
7583 would get in the way. Instead, @value{GDBN} makes these values available for
7584 subsequent use in expressions as values of the convenience variables
7585 @code{$_} and @code{$__}. After an @code{x} command, the last address
7586 examined is available for use in expressions in the convenience variable
7587 @code{$_}. The contents of that address, as examined, are available in
7588 the convenience variable @code{$__}.
7590 If the @code{x} command has a repeat count, the address and contents saved
7591 are from the last memory unit printed; this is not the same as the last
7592 address printed if several units were printed on the last line of output.
7594 @cindex remote memory comparison
7595 @cindex verify remote memory image
7596 When you are debugging a program running on a remote target machine
7597 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7598 remote machine's memory against the executable file you downloaded to
7599 the target. The @code{compare-sections} command is provided for such
7603 @kindex compare-sections
7604 @item compare-sections @r{[}@var{section-name}@r{]}
7605 Compare the data of a loadable section @var{section-name} in the
7606 executable file of the program being debugged with the same section in
7607 the remote machine's memory, and report any mismatches. With no
7608 arguments, compares all loadable sections. This command's
7609 availability depends on the target's support for the @code{"qCRC"}
7614 @section Automatic Display
7615 @cindex automatic display
7616 @cindex display of expressions
7618 If you find that you want to print the value of an expression frequently
7619 (to see how it changes), you might want to add it to the @dfn{automatic
7620 display list} so that @value{GDBN} prints its value each time your program stops.
7621 Each expression added to the list is given a number to identify it;
7622 to remove an expression from the list, you specify that number.
7623 The automatic display looks like this:
7627 3: bar[5] = (struct hack *) 0x3804
7631 This display shows item numbers, expressions and their current values. As with
7632 displays you request manually using @code{x} or @code{print}, you can
7633 specify the output format you prefer; in fact, @code{display} decides
7634 whether to use @code{print} or @code{x} depending your format
7635 specification---it uses @code{x} if you specify either the @samp{i}
7636 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7640 @item display @var{expr}
7641 Add the expression @var{expr} to the list of expressions to display
7642 each time your program stops. @xref{Expressions, ,Expressions}.
7644 @code{display} does not repeat if you press @key{RET} again after using it.
7646 @item display/@var{fmt} @var{expr}
7647 For @var{fmt} specifying only a display format and not a size or
7648 count, add the expression @var{expr} to the auto-display list but
7649 arrange to display it each time in the specified format @var{fmt}.
7650 @xref{Output Formats,,Output Formats}.
7652 @item display/@var{fmt} @var{addr}
7653 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7654 number of units, add the expression @var{addr} as a memory address to
7655 be examined each time your program stops. Examining means in effect
7656 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7659 For example, @samp{display/i $pc} can be helpful, to see the machine
7660 instruction about to be executed each time execution stops (@samp{$pc}
7661 is a common name for the program counter; @pxref{Registers, ,Registers}).
7664 @kindex delete display
7666 @item undisplay @var{dnums}@dots{}
7667 @itemx delete display @var{dnums}@dots{}
7668 Remove items from the list of expressions to display. Specify the
7669 numbers of the displays that you want affected with the command
7670 argument @var{dnums}. It can be a single display number, one of the
7671 numbers shown in the first field of the @samp{info display} display;
7672 or it could be a range of display numbers, as in @code{2-4}.
7674 @code{undisplay} does not repeat if you press @key{RET} after using it.
7675 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7677 @kindex disable display
7678 @item disable display @var{dnums}@dots{}
7679 Disable the display of item numbers @var{dnums}. A disabled display
7680 item is not printed automatically, but is not forgotten. It may be
7681 enabled again later. Specify the numbers of the displays that you
7682 want affected with the command argument @var{dnums}. It can be a
7683 single display number, one of the numbers shown in the first field of
7684 the @samp{info display} display; or it could be a range of display
7685 numbers, as in @code{2-4}.
7687 @kindex enable display
7688 @item enable display @var{dnums}@dots{}
7689 Enable display of item numbers @var{dnums}. It becomes effective once
7690 again in auto display of its expression, until you specify otherwise.
7691 Specify the numbers of the displays that you want affected with the
7692 command argument @var{dnums}. It can be a single display number, one
7693 of the numbers shown in the first field of the @samp{info display}
7694 display; or it could be a range of display numbers, as in @code{2-4}.
7697 Display the current values of the expressions on the list, just as is
7698 done when your program stops.
7700 @kindex info display
7702 Print the list of expressions previously set up to display
7703 automatically, each one with its item number, but without showing the
7704 values. This includes disabled expressions, which are marked as such.
7705 It also includes expressions which would not be displayed right now
7706 because they refer to automatic variables not currently available.
7709 @cindex display disabled out of scope
7710 If a display expression refers to local variables, then it does not make
7711 sense outside the lexical context for which it was set up. Such an
7712 expression is disabled when execution enters a context where one of its
7713 variables is not defined. For example, if you give the command
7714 @code{display last_char} while inside a function with an argument
7715 @code{last_char}, @value{GDBN} displays this argument while your program
7716 continues to stop inside that function. When it stops elsewhere---where
7717 there is no variable @code{last_char}---the display is disabled
7718 automatically. The next time your program stops where @code{last_char}
7719 is meaningful, you can enable the display expression once again.
7721 @node Print Settings
7722 @section Print Settings
7724 @cindex format options
7725 @cindex print settings
7726 @value{GDBN} provides the following ways to control how arrays, structures,
7727 and symbols are printed.
7730 These settings are useful for debugging programs in any language:
7734 @item set print address
7735 @itemx set print address on
7736 @cindex print/don't print memory addresses
7737 @value{GDBN} prints memory addresses showing the location of stack
7738 traces, structure values, pointer values, breakpoints, and so forth,
7739 even when it also displays the contents of those addresses. The default
7740 is @code{on}. For example, this is what a stack frame display looks like with
7741 @code{set print address on}:
7746 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7748 530 if (lquote != def_lquote)
7752 @item set print address off
7753 Do not print addresses when displaying their contents. For example,
7754 this is the same stack frame displayed with @code{set print address off}:
7758 (@value{GDBP}) set print addr off
7760 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7761 530 if (lquote != def_lquote)
7765 You can use @samp{set print address off} to eliminate all machine
7766 dependent displays from the @value{GDBN} interface. For example, with
7767 @code{print address off}, you should get the same text for backtraces on
7768 all machines---whether or not they involve pointer arguments.
7771 @item show print address
7772 Show whether or not addresses are to be printed.
7775 When @value{GDBN} prints a symbolic address, it normally prints the
7776 closest earlier symbol plus an offset. If that symbol does not uniquely
7777 identify the address (for example, it is a name whose scope is a single
7778 source file), you may need to clarify. One way to do this is with
7779 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7780 you can set @value{GDBN} to print the source file and line number when
7781 it prints a symbolic address:
7784 @item set print symbol-filename on
7785 @cindex source file and line of a symbol
7786 @cindex symbol, source file and line
7787 Tell @value{GDBN} to print the source file name and line number of a
7788 symbol in the symbolic form of an address.
7790 @item set print symbol-filename off
7791 Do not print source file name and line number of a symbol. This is the
7794 @item show print symbol-filename
7795 Show whether or not @value{GDBN} will print the source file name and
7796 line number of a symbol in the symbolic form of an address.
7799 Another situation where it is helpful to show symbol filenames and line
7800 numbers is when disassembling code; @value{GDBN} shows you the line
7801 number and source file that corresponds to each instruction.
7803 Also, you may wish to see the symbolic form only if the address being
7804 printed is reasonably close to the closest earlier symbol:
7807 @item set print max-symbolic-offset @var{max-offset}
7808 @cindex maximum value for offset of closest symbol
7809 Tell @value{GDBN} to only display the symbolic form of an address if the
7810 offset between the closest earlier symbol and the address is less than
7811 @var{max-offset}. The default is 0, which tells @value{GDBN}
7812 to always print the symbolic form of an address if any symbol precedes it.
7814 @item show print max-symbolic-offset
7815 Ask how large the maximum offset is that @value{GDBN} prints in a
7819 @cindex wild pointer, interpreting
7820 @cindex pointer, finding referent
7821 If you have a pointer and you are not sure where it points, try
7822 @samp{set print symbol-filename on}. Then you can determine the name
7823 and source file location of the variable where it points, using
7824 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7825 For example, here @value{GDBN} shows that a variable @code{ptt} points
7826 at another variable @code{t}, defined in @file{hi2.c}:
7829 (@value{GDBP}) set print symbol-filename on
7830 (@value{GDBP}) p/a ptt
7831 $4 = 0xe008 <t in hi2.c>
7835 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7836 does not show the symbol name and filename of the referent, even with
7837 the appropriate @code{set print} options turned on.
7840 Other settings control how different kinds of objects are printed:
7843 @item set print array
7844 @itemx set print array on
7845 @cindex pretty print arrays
7846 Pretty print arrays. This format is more convenient to read,
7847 but uses more space. The default is off.
7849 @item set print array off
7850 Return to compressed format for arrays.
7852 @item show print array
7853 Show whether compressed or pretty format is selected for displaying
7856 @cindex print array indexes
7857 @item set print array-indexes
7858 @itemx set print array-indexes on
7859 Print the index of each element when displaying arrays. May be more
7860 convenient to locate a given element in the array or quickly find the
7861 index of a given element in that printed array. The default is off.
7863 @item set print array-indexes off
7864 Stop printing element indexes when displaying arrays.
7866 @item show print array-indexes
7867 Show whether the index of each element is printed when displaying
7870 @item set print elements @var{number-of-elements}
7871 @cindex number of array elements to print
7872 @cindex limit on number of printed array elements
7873 Set a limit on how many elements of an array @value{GDBN} will print.
7874 If @value{GDBN} is printing a large array, it stops printing after it has
7875 printed the number of elements set by the @code{set print elements} command.
7876 This limit also applies to the display of strings.
7877 When @value{GDBN} starts, this limit is set to 200.
7878 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7880 @item show print elements
7881 Display the number of elements of a large array that @value{GDBN} will print.
7882 If the number is 0, then the printing is unlimited.
7884 @item set print frame-arguments @var{value}
7885 @kindex set print frame-arguments
7886 @cindex printing frame argument values
7887 @cindex print all frame argument values
7888 @cindex print frame argument values for scalars only
7889 @cindex do not print frame argument values
7890 This command allows to control how the values of arguments are printed
7891 when the debugger prints a frame (@pxref{Frames}). The possible
7896 The values of all arguments are printed.
7899 Print the value of an argument only if it is a scalar. The value of more
7900 complex arguments such as arrays, structures, unions, etc, is replaced
7901 by @code{@dots{}}. This is the default. Here is an example where
7902 only scalar arguments are shown:
7905 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7910 None of the argument values are printed. Instead, the value of each argument
7911 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7914 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7919 By default, only scalar arguments are printed. This command can be used
7920 to configure the debugger to print the value of all arguments, regardless
7921 of their type. However, it is often advantageous to not print the value
7922 of more complex parameters. For instance, it reduces the amount of
7923 information printed in each frame, making the backtrace more readable.
7924 Also, it improves performance when displaying Ada frames, because
7925 the computation of large arguments can sometimes be CPU-intensive,
7926 especially in large applications. Setting @code{print frame-arguments}
7927 to @code{scalars} (the default) or @code{none} avoids this computation,
7928 thus speeding up the display of each Ada frame.
7930 @item show print frame-arguments
7931 Show how the value of arguments should be displayed when printing a frame.
7933 @item set print repeats
7934 @cindex repeated array elements
7935 Set the threshold for suppressing display of repeated array
7936 elements. When the number of consecutive identical elements of an
7937 array exceeds the threshold, @value{GDBN} prints the string
7938 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7939 identical repetitions, instead of displaying the identical elements
7940 themselves. Setting the threshold to zero will cause all elements to
7941 be individually printed. The default threshold is 10.
7943 @item show print repeats
7944 Display the current threshold for printing repeated identical
7947 @item set print null-stop
7948 @cindex @sc{null} elements in arrays
7949 Cause @value{GDBN} to stop printing the characters of an array when the first
7950 @sc{null} is encountered. This is useful when large arrays actually
7951 contain only short strings.
7954 @item show print null-stop
7955 Show whether @value{GDBN} stops printing an array on the first
7956 @sc{null} character.
7958 @item set print pretty on
7959 @cindex print structures in indented form
7960 @cindex indentation in structure display
7961 Cause @value{GDBN} to print structures in an indented format with one member
7962 per line, like this:
7977 @item set print pretty off
7978 Cause @value{GDBN} to print structures in a compact format, like this:
7982 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7983 meat = 0x54 "Pork"@}
7988 This is the default format.
7990 @item show print pretty
7991 Show which format @value{GDBN} is using to print structures.
7993 @item set print sevenbit-strings on
7994 @cindex eight-bit characters in strings
7995 @cindex octal escapes in strings
7996 Print using only seven-bit characters; if this option is set,
7997 @value{GDBN} displays any eight-bit characters (in strings or
7998 character values) using the notation @code{\}@var{nnn}. This setting is
7999 best if you are working in English (@sc{ascii}) and you use the
8000 high-order bit of characters as a marker or ``meta'' bit.
8002 @item set print sevenbit-strings off
8003 Print full eight-bit characters. This allows the use of more
8004 international character sets, and is the default.
8006 @item show print sevenbit-strings
8007 Show whether or not @value{GDBN} is printing only seven-bit characters.
8009 @item set print union on
8010 @cindex unions in structures, printing
8011 Tell @value{GDBN} to print unions which are contained in structures
8012 and other unions. This is the default setting.
8014 @item set print union off
8015 Tell @value{GDBN} not to print unions which are contained in
8016 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8019 @item show print union
8020 Ask @value{GDBN} whether or not it will print unions which are contained in
8021 structures and other unions.
8023 For example, given the declarations
8026 typedef enum @{Tree, Bug@} Species;
8027 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8028 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8039 struct thing foo = @{Tree, @{Acorn@}@};
8043 with @code{set print union on} in effect @samp{p foo} would print
8046 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8050 and with @code{set print union off} in effect it would print
8053 $1 = @{it = Tree, form = @{...@}@}
8057 @code{set print union} affects programs written in C-like languages
8063 These settings are of interest when debugging C@t{++} programs:
8066 @cindex demangling C@t{++} names
8067 @item set print demangle
8068 @itemx set print demangle on
8069 Print C@t{++} names in their source form rather than in the encoded
8070 (``mangled'') form passed to the assembler and linker for type-safe
8071 linkage. The default is on.
8073 @item show print demangle
8074 Show whether C@t{++} names are printed in mangled or demangled form.
8076 @item set print asm-demangle
8077 @itemx set print asm-demangle on
8078 Print C@t{++} names in their source form rather than their mangled form, even
8079 in assembler code printouts such as instruction disassemblies.
8082 @item show print asm-demangle
8083 Show whether C@t{++} names in assembly listings are printed in mangled
8086 @cindex C@t{++} symbol decoding style
8087 @cindex symbol decoding style, C@t{++}
8088 @kindex set demangle-style
8089 @item set demangle-style @var{style}
8090 Choose among several encoding schemes used by different compilers to
8091 represent C@t{++} names. The choices for @var{style} are currently:
8095 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8098 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8099 This is the default.
8102 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8105 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8108 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8109 @strong{Warning:} this setting alone is not sufficient to allow
8110 debugging @code{cfront}-generated executables. @value{GDBN} would
8111 require further enhancement to permit that.
8114 If you omit @var{style}, you will see a list of possible formats.
8116 @item show demangle-style
8117 Display the encoding style currently in use for decoding C@t{++} symbols.
8119 @item set print object
8120 @itemx set print object on
8121 @cindex derived type of an object, printing
8122 @cindex display derived types
8123 When displaying a pointer to an object, identify the @emph{actual}
8124 (derived) type of the object rather than the @emph{declared} type, using
8125 the virtual function table.
8127 @item set print object off
8128 Display only the declared type of objects, without reference to the
8129 virtual function table. This is the default setting.
8131 @item show print object
8132 Show whether actual, or declared, object types are displayed.
8134 @item set print static-members
8135 @itemx set print static-members on
8136 @cindex static members of C@t{++} objects
8137 Print static members when displaying a C@t{++} object. The default is on.
8139 @item set print static-members off
8140 Do not print static members when displaying a C@t{++} object.
8142 @item show print static-members
8143 Show whether C@t{++} static members are printed or not.
8145 @item set print pascal_static-members
8146 @itemx set print pascal_static-members on
8147 @cindex static members of Pascal objects
8148 @cindex Pascal objects, static members display
8149 Print static members when displaying a Pascal object. The default is on.
8151 @item set print pascal_static-members off
8152 Do not print static members when displaying a Pascal object.
8154 @item show print pascal_static-members
8155 Show whether Pascal static members are printed or not.
8157 @c These don't work with HP ANSI C++ yet.
8158 @item set print vtbl
8159 @itemx set print vtbl on
8160 @cindex pretty print C@t{++} virtual function tables
8161 @cindex virtual functions (C@t{++}) display
8162 @cindex VTBL display
8163 Pretty print C@t{++} virtual function tables. The default is off.
8164 (The @code{vtbl} commands do not work on programs compiled with the HP
8165 ANSI C@t{++} compiler (@code{aCC}).)
8167 @item set print vtbl off
8168 Do not pretty print C@t{++} virtual function tables.
8170 @item show print vtbl
8171 Show whether C@t{++} virtual function tables are pretty printed, or not.
8174 @node Pretty Printing
8175 @section Pretty Printing
8177 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8178 Python code. It greatly simplifies the display of complex objects. This
8179 mechanism works for both MI and the CLI.
8182 * Pretty-Printer Introduction:: Introduction to pretty-printers
8183 * Pretty-Printer Example:: An example pretty-printer
8184 * Pretty-Printer Commands:: Pretty-printer commands
8187 @node Pretty-Printer Introduction
8188 @subsection Pretty-Printer Introduction
8190 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8191 registered for the value. If there is then @value{GDBN} invokes the
8192 pretty-printer to print the value. Otherwise the value is printed normally.
8194 Pretty-printers are normally named. This makes them easy to manage.
8195 The @samp{info pretty-printer} command will list all the installed
8196 pretty-printers with their names.
8197 If a pretty-printer can handle multiple data types, then its
8198 @dfn{subprinters} are the printers for the individual data types.
8199 Each such subprinter has its own name.
8200 The format of the name is @var{printer-name};@var{subprinter-name}.
8202 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8203 Typically they are automatically loaded and registered when the corresponding
8204 debug information is loaded, thus making them available without having to
8205 do anything special.
8207 There are three places where a pretty-printer can be registered.
8211 Pretty-printers registered globally are available when debugging
8215 Pretty-printers registered with a program space are available only
8216 when debugging that program.
8217 @xref{Progspaces In Python}, for more details on program spaces in Python.
8220 Pretty-printers registered with an objfile are loaded and unloaded
8221 with the corresponding objfile (e.g., shared library).
8222 @xref{Objfiles In Python}, for more details on objfiles in Python.
8225 @xref{Selecting Pretty-Printers}, for further information on how
8226 pretty-printers are selected,
8228 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8231 @node Pretty-Printer Example
8232 @subsection Pretty-Printer Example
8234 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8237 (@value{GDBP}) print s
8239 static npos = 4294967295,
8241 <std::allocator<char>> = @{
8242 <__gnu_cxx::new_allocator<char>> = @{
8243 <No data fields>@}, <No data fields>
8245 members of std::basic_string<char, std::char_traits<char>,
8246 std::allocator<char> >::_Alloc_hider:
8247 _M_p = 0x804a014 "abcd"
8252 With a pretty-printer for @code{std::string} only the contents are printed:
8255 (@value{GDBP}) print s
8259 @node Pretty-Printer Commands
8260 @subsection Pretty-Printer Commands
8261 @cindex pretty-printer commands
8264 @kindex info pretty-printer
8265 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8266 Print the list of installed pretty-printers.
8267 This includes disabled pretty-printers, which are marked as such.
8269 @var{object-regexp} is a regular expression matching the objects
8270 whose pretty-printers to list.
8271 Objects can be @code{global}, the program space's file
8272 (@pxref{Progspaces In Python}),
8273 and the object files within that program space (@pxref{Objfiles In Python}).
8274 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8275 looks up a printer from these three objects.
8277 @var{name-regexp} is a regular expression matching the name of the printers
8280 @kindex disable pretty-printer
8281 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8282 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8283 A disabled pretty-printer is not forgotten, it may be enabled again later.
8285 @kindex enable pretty-printer
8286 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8287 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8292 Suppose we have three pretty-printers installed: one from library1.so
8293 named @code{foo} that prints objects of type @code{foo}, and
8294 another from library2.so named @code{bar} that prints two types of objects,
8295 @code{bar1} and @code{bar2}.
8298 (gdb) info pretty-printer
8305 (gdb) info pretty-printer library2
8310 (gdb) disable pretty-printer library1
8312 2 of 3 printers enabled
8313 (gdb) info pretty-printer
8320 (gdb) disable pretty-printer library2 bar:bar1
8322 1 of 3 printers enabled
8323 (gdb) info pretty-printer library2
8330 (gdb) disable pretty-printer library2 bar
8332 0 of 3 printers enabled
8333 (gdb) info pretty-printer library2
8342 Note that for @code{bar} the entire printer can be disabled,
8343 as can each individual subprinter.
8346 @section Value History
8348 @cindex value history
8349 @cindex history of values printed by @value{GDBN}
8350 Values printed by the @code{print} command are saved in the @value{GDBN}
8351 @dfn{value history}. This allows you to refer to them in other expressions.
8352 Values are kept until the symbol table is re-read or discarded
8353 (for example with the @code{file} or @code{symbol-file} commands).
8354 When the symbol table changes, the value history is discarded,
8355 since the values may contain pointers back to the types defined in the
8360 @cindex history number
8361 The values printed are given @dfn{history numbers} by which you can
8362 refer to them. These are successive integers starting with one.
8363 @code{print} shows you the history number assigned to a value by
8364 printing @samp{$@var{num} = } before the value; here @var{num} is the
8367 To refer to any previous value, use @samp{$} followed by the value's
8368 history number. The way @code{print} labels its output is designed to
8369 remind you of this. Just @code{$} refers to the most recent value in
8370 the history, and @code{$$} refers to the value before that.
8371 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8372 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8373 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8375 For example, suppose you have just printed a pointer to a structure and
8376 want to see the contents of the structure. It suffices to type
8382 If you have a chain of structures where the component @code{next} points
8383 to the next one, you can print the contents of the next one with this:
8390 You can print successive links in the chain by repeating this
8391 command---which you can do by just typing @key{RET}.
8393 Note that the history records values, not expressions. If the value of
8394 @code{x} is 4 and you type these commands:
8402 then the value recorded in the value history by the @code{print} command
8403 remains 4 even though the value of @code{x} has changed.
8408 Print the last ten values in the value history, with their item numbers.
8409 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8410 values} does not change the history.
8412 @item show values @var{n}
8413 Print ten history values centered on history item number @var{n}.
8416 Print ten history values just after the values last printed. If no more
8417 values are available, @code{show values +} produces no display.
8420 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8421 same effect as @samp{show values +}.
8423 @node Convenience Vars
8424 @section Convenience Variables
8426 @cindex convenience variables
8427 @cindex user-defined variables
8428 @value{GDBN} provides @dfn{convenience variables} that you can use within
8429 @value{GDBN} to hold on to a value and refer to it later. These variables
8430 exist entirely within @value{GDBN}; they are not part of your program, and
8431 setting a convenience variable has no direct effect on further execution
8432 of your program. That is why you can use them freely.
8434 Convenience variables are prefixed with @samp{$}. Any name preceded by
8435 @samp{$} can be used for a convenience variable, unless it is one of
8436 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8437 (Value history references, in contrast, are @emph{numbers} preceded
8438 by @samp{$}. @xref{Value History, ,Value History}.)
8440 You can save a value in a convenience variable with an assignment
8441 expression, just as you would set a variable in your program.
8445 set $foo = *object_ptr
8449 would save in @code{$foo} the value contained in the object pointed to by
8452 Using a convenience variable for the first time creates it, but its
8453 value is @code{void} until you assign a new value. You can alter the
8454 value with another assignment at any time.
8456 Convenience variables have no fixed types. You can assign a convenience
8457 variable any type of value, including structures and arrays, even if
8458 that variable already has a value of a different type. The convenience
8459 variable, when used as an expression, has the type of its current value.
8462 @kindex show convenience
8463 @cindex show all user variables
8464 @item show convenience
8465 Print a list of convenience variables used so far, and their values.
8466 Abbreviated @code{show conv}.
8468 @kindex init-if-undefined
8469 @cindex convenience variables, initializing
8470 @item init-if-undefined $@var{variable} = @var{expression}
8471 Set a convenience variable if it has not already been set. This is useful
8472 for user-defined commands that keep some state. It is similar, in concept,
8473 to using local static variables with initializers in C (except that
8474 convenience variables are global). It can also be used to allow users to
8475 override default values used in a command script.
8477 If the variable is already defined then the expression is not evaluated so
8478 any side-effects do not occur.
8481 One of the ways to use a convenience variable is as a counter to be
8482 incremented or a pointer to be advanced. For example, to print
8483 a field from successive elements of an array of structures:
8487 print bar[$i++]->contents
8491 Repeat that command by typing @key{RET}.
8493 Some convenience variables are created automatically by @value{GDBN} and given
8494 values likely to be useful.
8497 @vindex $_@r{, convenience variable}
8499 The variable @code{$_} is automatically set by the @code{x} command to
8500 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8501 commands which provide a default address for @code{x} to examine also
8502 set @code{$_} to that address; these commands include @code{info line}
8503 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8504 except when set by the @code{x} command, in which case it is a pointer
8505 to the type of @code{$__}.
8507 @vindex $__@r{, convenience variable}
8509 The variable @code{$__} is automatically set by the @code{x} command
8510 to the value found in the last address examined. Its type is chosen
8511 to match the format in which the data was printed.
8514 @vindex $_exitcode@r{, convenience variable}
8515 The variable @code{$_exitcode} is automatically set to the exit code when
8516 the program being debugged terminates.
8519 @vindex $_sdata@r{, inspect, convenience variable}
8520 The variable @code{$_sdata} contains extra collected static tracepoint
8521 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8522 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8523 if extra static tracepoint data has not been collected.
8526 @vindex $_siginfo@r{, convenience variable}
8527 The variable @code{$_siginfo} contains extra signal information
8528 (@pxref{extra signal information}). Note that @code{$_siginfo}
8529 could be empty, if the application has not yet received any signals.
8530 For example, it will be empty before you execute the @code{run} command.
8533 @vindex $_tlb@r{, convenience variable}
8534 The variable @code{$_tlb} is automatically set when debugging
8535 applications running on MS-Windows in native mode or connected to
8536 gdbserver that supports the @code{qGetTIBAddr} request.
8537 @xref{General Query Packets}.
8538 This variable contains the address of the thread information block.
8542 On HP-UX systems, if you refer to a function or variable name that
8543 begins with a dollar sign, @value{GDBN} searches for a user or system
8544 name first, before it searches for a convenience variable.
8546 @cindex convenience functions
8547 @value{GDBN} also supplies some @dfn{convenience functions}. These
8548 have a syntax similar to convenience variables. A convenience
8549 function can be used in an expression just like an ordinary function;
8550 however, a convenience function is implemented internally to
8555 @kindex help function
8556 @cindex show all convenience functions
8557 Print a list of all convenience functions.
8564 You can refer to machine register contents, in expressions, as variables
8565 with names starting with @samp{$}. The names of registers are different
8566 for each machine; use @code{info registers} to see the names used on
8570 @kindex info registers
8571 @item info registers
8572 Print the names and values of all registers except floating-point
8573 and vector registers (in the selected stack frame).
8575 @kindex info all-registers
8576 @cindex floating point registers
8577 @item info all-registers
8578 Print the names and values of all registers, including floating-point
8579 and vector registers (in the selected stack frame).
8581 @item info registers @var{regname} @dots{}
8582 Print the @dfn{relativized} value of each specified register @var{regname}.
8583 As discussed in detail below, register values are normally relative to
8584 the selected stack frame. @var{regname} may be any register name valid on
8585 the machine you are using, with or without the initial @samp{$}.
8588 @cindex stack pointer register
8589 @cindex program counter register
8590 @cindex process status register
8591 @cindex frame pointer register
8592 @cindex standard registers
8593 @value{GDBN} has four ``standard'' register names that are available (in
8594 expressions) on most machines---whenever they do not conflict with an
8595 architecture's canonical mnemonics for registers. The register names
8596 @code{$pc} and @code{$sp} are used for the program counter register and
8597 the stack pointer. @code{$fp} is used for a register that contains a
8598 pointer to the current stack frame, and @code{$ps} is used for a
8599 register that contains the processor status. For example,
8600 you could print the program counter in hex with
8607 or print the instruction to be executed next with
8614 or add four to the stack pointer@footnote{This is a way of removing
8615 one word from the stack, on machines where stacks grow downward in
8616 memory (most machines, nowadays). This assumes that the innermost
8617 stack frame is selected; setting @code{$sp} is not allowed when other
8618 stack frames are selected. To pop entire frames off the stack,
8619 regardless of machine architecture, use @code{return};
8620 see @ref{Returning, ,Returning from a Function}.} with
8626 Whenever possible, these four standard register names are available on
8627 your machine even though the machine has different canonical mnemonics,
8628 so long as there is no conflict. The @code{info registers} command
8629 shows the canonical names. For example, on the SPARC, @code{info
8630 registers} displays the processor status register as @code{$psr} but you
8631 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8632 is an alias for the @sc{eflags} register.
8634 @value{GDBN} always considers the contents of an ordinary register as an
8635 integer when the register is examined in this way. Some machines have
8636 special registers which can hold nothing but floating point; these
8637 registers are considered to have floating point values. There is no way
8638 to refer to the contents of an ordinary register as floating point value
8639 (although you can @emph{print} it as a floating point value with
8640 @samp{print/f $@var{regname}}).
8642 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8643 means that the data format in which the register contents are saved by
8644 the operating system is not the same one that your program normally
8645 sees. For example, the registers of the 68881 floating point
8646 coprocessor are always saved in ``extended'' (raw) format, but all C
8647 programs expect to work with ``double'' (virtual) format. In such
8648 cases, @value{GDBN} normally works with the virtual format only (the format
8649 that makes sense for your program), but the @code{info registers} command
8650 prints the data in both formats.
8652 @cindex SSE registers (x86)
8653 @cindex MMX registers (x86)
8654 Some machines have special registers whose contents can be interpreted
8655 in several different ways. For example, modern x86-based machines
8656 have SSE and MMX registers that can hold several values packed
8657 together in several different formats. @value{GDBN} refers to such
8658 registers in @code{struct} notation:
8661 (@value{GDBP}) print $xmm1
8663 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8664 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8665 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8666 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8667 v4_int32 = @{0, 20657912, 11, 13@},
8668 v2_int64 = @{88725056443645952, 55834574859@},
8669 uint128 = 0x0000000d0000000b013b36f800000000
8674 To set values of such registers, you need to tell @value{GDBN} which
8675 view of the register you wish to change, as if you were assigning
8676 value to a @code{struct} member:
8679 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8682 Normally, register values are relative to the selected stack frame
8683 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8684 value that the register would contain if all stack frames farther in
8685 were exited and their saved registers restored. In order to see the
8686 true contents of hardware registers, you must select the innermost
8687 frame (with @samp{frame 0}).
8689 However, @value{GDBN} must deduce where registers are saved, from the machine
8690 code generated by your compiler. If some registers are not saved, or if
8691 @value{GDBN} is unable to locate the saved registers, the selected stack
8692 frame makes no difference.
8694 @node Floating Point Hardware
8695 @section Floating Point Hardware
8696 @cindex floating point
8698 Depending on the configuration, @value{GDBN} may be able to give
8699 you more information about the status of the floating point hardware.
8704 Display hardware-dependent information about the floating
8705 point unit. The exact contents and layout vary depending on the
8706 floating point chip. Currently, @samp{info float} is supported on
8707 the ARM and x86 machines.
8711 @section Vector Unit
8714 Depending on the configuration, @value{GDBN} may be able to give you
8715 more information about the status of the vector unit.
8720 Display information about the vector unit. The exact contents and
8721 layout vary depending on the hardware.
8724 @node OS Information
8725 @section Operating System Auxiliary Information
8726 @cindex OS information
8728 @value{GDBN} provides interfaces to useful OS facilities that can help
8729 you debug your program.
8731 @cindex @code{ptrace} system call
8732 @cindex @code{struct user} contents
8733 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8734 machines), it interfaces with the inferior via the @code{ptrace}
8735 system call. The operating system creates a special sata structure,
8736 called @code{struct user}, for this interface. You can use the
8737 command @code{info udot} to display the contents of this data
8743 Display the contents of the @code{struct user} maintained by the OS
8744 kernel for the program being debugged. @value{GDBN} displays the
8745 contents of @code{struct user} as a list of hex numbers, similar to
8746 the @code{examine} command.
8749 @cindex auxiliary vector
8750 @cindex vector, auxiliary
8751 Some operating systems supply an @dfn{auxiliary vector} to programs at
8752 startup. This is akin to the arguments and environment that you
8753 specify for a program, but contains a system-dependent variety of
8754 binary values that tell system libraries important details about the
8755 hardware, operating system, and process. Each value's purpose is
8756 identified by an integer tag; the meanings are well-known but system-specific.
8757 Depending on the configuration and operating system facilities,
8758 @value{GDBN} may be able to show you this information. For remote
8759 targets, this functionality may further depend on the remote stub's
8760 support of the @samp{qXfer:auxv:read} packet, see
8761 @ref{qXfer auxiliary vector read}.
8766 Display the auxiliary vector of the inferior, which can be either a
8767 live process or a core dump file. @value{GDBN} prints each tag value
8768 numerically, and also shows names and text descriptions for recognized
8769 tags. Some values in the vector are numbers, some bit masks, and some
8770 pointers to strings or other data. @value{GDBN} displays each value in the
8771 most appropriate form for a recognized tag, and in hexadecimal for
8772 an unrecognized tag.
8775 On some targets, @value{GDBN} can access operating-system-specific information
8776 and display it to user, without interpretation. For remote targets,
8777 this functionality depends on the remote stub's support of the
8778 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8783 List the types of OS information available for the target. If the
8784 target does not return a list of possible types, this command will
8787 @kindex info os processes
8788 @item info os processes
8789 Display the list of processes on the target. For each process,
8790 @value{GDBN} prints the process identifier, the name of the user, and
8791 the command corresponding to the process.
8794 @node Memory Region Attributes
8795 @section Memory Region Attributes
8796 @cindex memory region attributes
8798 @dfn{Memory region attributes} allow you to describe special handling
8799 required by regions of your target's memory. @value{GDBN} uses
8800 attributes to determine whether to allow certain types of memory
8801 accesses; whether to use specific width accesses; and whether to cache
8802 target memory. By default the description of memory regions is
8803 fetched from the target (if the current target supports this), but the
8804 user can override the fetched regions.
8806 Defined memory regions can be individually enabled and disabled. When a
8807 memory region is disabled, @value{GDBN} uses the default attributes when
8808 accessing memory in that region. Similarly, if no memory regions have
8809 been defined, @value{GDBN} uses the default attributes when accessing
8812 When a memory region is defined, it is given a number to identify it;
8813 to enable, disable, or remove a memory region, you specify that number.
8817 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8818 Define a memory region bounded by @var{lower} and @var{upper} with
8819 attributes @var{attributes}@dots{}, and add it to the list of regions
8820 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8821 case: it is treated as the target's maximum memory address.
8822 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8825 Discard any user changes to the memory regions and use target-supplied
8826 regions, if available, or no regions if the target does not support.
8829 @item delete mem @var{nums}@dots{}
8830 Remove memory regions @var{nums}@dots{} from the list of regions
8831 monitored by @value{GDBN}.
8834 @item disable mem @var{nums}@dots{}
8835 Disable monitoring of memory regions @var{nums}@dots{}.
8836 A disabled memory region is not forgotten.
8837 It may be enabled again later.
8840 @item enable mem @var{nums}@dots{}
8841 Enable monitoring of memory regions @var{nums}@dots{}.
8845 Print a table of all defined memory regions, with the following columns
8849 @item Memory Region Number
8850 @item Enabled or Disabled.
8851 Enabled memory regions are marked with @samp{y}.
8852 Disabled memory regions are marked with @samp{n}.
8855 The address defining the inclusive lower bound of the memory region.
8858 The address defining the exclusive upper bound of the memory region.
8861 The list of attributes set for this memory region.
8866 @subsection Attributes
8868 @subsubsection Memory Access Mode
8869 The access mode attributes set whether @value{GDBN} may make read or
8870 write accesses to a memory region.
8872 While these attributes prevent @value{GDBN} from performing invalid
8873 memory accesses, they do nothing to prevent the target system, I/O DMA,
8874 etc.@: from accessing memory.
8878 Memory is read only.
8880 Memory is write only.
8882 Memory is read/write. This is the default.
8885 @subsubsection Memory Access Size
8886 The access size attribute tells @value{GDBN} to use specific sized
8887 accesses in the memory region. Often memory mapped device registers
8888 require specific sized accesses. If no access size attribute is
8889 specified, @value{GDBN} may use accesses of any size.
8893 Use 8 bit memory accesses.
8895 Use 16 bit memory accesses.
8897 Use 32 bit memory accesses.
8899 Use 64 bit memory accesses.
8902 @c @subsubsection Hardware/Software Breakpoints
8903 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8904 @c will use hardware or software breakpoints for the internal breakpoints
8905 @c used by the step, next, finish, until, etc. commands.
8909 @c Always use hardware breakpoints
8910 @c @item swbreak (default)
8913 @subsubsection Data Cache
8914 The data cache attributes set whether @value{GDBN} will cache target
8915 memory. While this generally improves performance by reducing debug
8916 protocol overhead, it can lead to incorrect results because @value{GDBN}
8917 does not know about volatile variables or memory mapped device
8922 Enable @value{GDBN} to cache target memory.
8924 Disable @value{GDBN} from caching target memory. This is the default.
8927 @subsection Memory Access Checking
8928 @value{GDBN} can be instructed to refuse accesses to memory that is
8929 not explicitly described. This can be useful if accessing such
8930 regions has undesired effects for a specific target, or to provide
8931 better error checking. The following commands control this behaviour.
8934 @kindex set mem inaccessible-by-default
8935 @item set mem inaccessible-by-default [on|off]
8936 If @code{on} is specified, make @value{GDBN} treat memory not
8937 explicitly described by the memory ranges as non-existent and refuse accesses
8938 to such memory. The checks are only performed if there's at least one
8939 memory range defined. If @code{off} is specified, make @value{GDBN}
8940 treat the memory not explicitly described by the memory ranges as RAM.
8941 The default value is @code{on}.
8942 @kindex show mem inaccessible-by-default
8943 @item show mem inaccessible-by-default
8944 Show the current handling of accesses to unknown memory.
8948 @c @subsubsection Memory Write Verification
8949 @c The memory write verification attributes set whether @value{GDBN}
8950 @c will re-reads data after each write to verify the write was successful.
8954 @c @item noverify (default)
8957 @node Dump/Restore Files
8958 @section Copy Between Memory and a File
8959 @cindex dump/restore files
8960 @cindex append data to a file
8961 @cindex dump data to a file
8962 @cindex restore data from a file
8964 You can use the commands @code{dump}, @code{append}, and
8965 @code{restore} to copy data between target memory and a file. The
8966 @code{dump} and @code{append} commands write data to a file, and the
8967 @code{restore} command reads data from a file back into the inferior's
8968 memory. Files may be in binary, Motorola S-record, Intel hex, or
8969 Tektronix Hex format; however, @value{GDBN} can only append to binary
8975 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8976 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8977 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8978 or the value of @var{expr}, to @var{filename} in the given format.
8980 The @var{format} parameter may be any one of:
8987 Motorola S-record format.
8989 Tektronix Hex format.
8992 @value{GDBN} uses the same definitions of these formats as the
8993 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8994 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8998 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8999 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9000 Append the contents of memory from @var{start_addr} to @var{end_addr},
9001 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9002 (@value{GDBN} can only append data to files in raw binary form.)
9005 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9006 Restore the contents of file @var{filename} into memory. The
9007 @code{restore} command can automatically recognize any known @sc{bfd}
9008 file format, except for raw binary. To restore a raw binary file you
9009 must specify the optional keyword @code{binary} after the filename.
9011 If @var{bias} is non-zero, its value will be added to the addresses
9012 contained in the file. Binary files always start at address zero, so
9013 they will be restored at address @var{bias}. Other bfd files have
9014 a built-in location; they will be restored at offset @var{bias}
9017 If @var{start} and/or @var{end} are non-zero, then only data between
9018 file offset @var{start} and file offset @var{end} will be restored.
9019 These offsets are relative to the addresses in the file, before
9020 the @var{bias} argument is applied.
9024 @node Core File Generation
9025 @section How to Produce a Core File from Your Program
9026 @cindex dump core from inferior
9028 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9029 image of a running process and its process status (register values
9030 etc.). Its primary use is post-mortem debugging of a program that
9031 crashed while it ran outside a debugger. A program that crashes
9032 automatically produces a core file, unless this feature is disabled by
9033 the user. @xref{Files}, for information on invoking @value{GDBN} in
9034 the post-mortem debugging mode.
9036 Occasionally, you may wish to produce a core file of the program you
9037 are debugging in order to preserve a snapshot of its state.
9038 @value{GDBN} has a special command for that.
9042 @kindex generate-core-file
9043 @item generate-core-file [@var{file}]
9044 @itemx gcore [@var{file}]
9045 Produce a core dump of the inferior process. The optional argument
9046 @var{file} specifies the file name where to put the core dump. If not
9047 specified, the file name defaults to @file{core.@var{pid}}, where
9048 @var{pid} is the inferior process ID.
9050 Note that this command is implemented only for some systems (as of
9051 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9054 @node Character Sets
9055 @section Character Sets
9056 @cindex character sets
9058 @cindex translating between character sets
9059 @cindex host character set
9060 @cindex target character set
9062 If the program you are debugging uses a different character set to
9063 represent characters and strings than the one @value{GDBN} uses itself,
9064 @value{GDBN} can automatically translate between the character sets for
9065 you. The character set @value{GDBN} uses we call the @dfn{host
9066 character set}; the one the inferior program uses we call the
9067 @dfn{target character set}.
9069 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9070 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9071 remote protocol (@pxref{Remote Debugging}) to debug a program
9072 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9073 then the host character set is Latin-1, and the target character set is
9074 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9075 target-charset EBCDIC-US}, then @value{GDBN} translates between
9076 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9077 character and string literals in expressions.
9079 @value{GDBN} has no way to automatically recognize which character set
9080 the inferior program uses; you must tell it, using the @code{set
9081 target-charset} command, described below.
9083 Here are the commands for controlling @value{GDBN}'s character set
9087 @item set target-charset @var{charset}
9088 @kindex set target-charset
9089 Set the current target character set to @var{charset}. To display the
9090 list of supported target character sets, type
9091 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9093 @item set host-charset @var{charset}
9094 @kindex set host-charset
9095 Set the current host character set to @var{charset}.
9097 By default, @value{GDBN} uses a host character set appropriate to the
9098 system it is running on; you can override that default using the
9099 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9100 automatically determine the appropriate host character set. In this
9101 case, @value{GDBN} uses @samp{UTF-8}.
9103 @value{GDBN} can only use certain character sets as its host character
9104 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9105 @value{GDBN} will list the host character sets it supports.
9107 @item set charset @var{charset}
9109 Set the current host and target character sets to @var{charset}. As
9110 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9111 @value{GDBN} will list the names of the character sets that can be used
9112 for both host and target.
9115 @kindex show charset
9116 Show the names of the current host and target character sets.
9118 @item show host-charset
9119 @kindex show host-charset
9120 Show the name of the current host character set.
9122 @item show target-charset
9123 @kindex show target-charset
9124 Show the name of the current target character set.
9126 @item set target-wide-charset @var{charset}
9127 @kindex set target-wide-charset
9128 Set the current target's wide character set to @var{charset}. This is
9129 the character set used by the target's @code{wchar_t} type. To
9130 display the list of supported wide character sets, type
9131 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9133 @item show target-wide-charset
9134 @kindex show target-wide-charset
9135 Show the name of the current target's wide character set.
9138 Here is an example of @value{GDBN}'s character set support in action.
9139 Assume that the following source code has been placed in the file
9140 @file{charset-test.c}:
9146 = @{72, 101, 108, 108, 111, 44, 32, 119,
9147 111, 114, 108, 100, 33, 10, 0@};
9148 char ibm1047_hello[]
9149 = @{200, 133, 147, 147, 150, 107, 64, 166,
9150 150, 153, 147, 132, 90, 37, 0@};
9154 printf ("Hello, world!\n");
9158 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9159 containing the string @samp{Hello, world!} followed by a newline,
9160 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9162 We compile the program, and invoke the debugger on it:
9165 $ gcc -g charset-test.c -o charset-test
9166 $ gdb -nw charset-test
9167 GNU gdb 2001-12-19-cvs
9168 Copyright 2001 Free Software Foundation, Inc.
9173 We can use the @code{show charset} command to see what character sets
9174 @value{GDBN} is currently using to interpret and display characters and
9178 (@value{GDBP}) show charset
9179 The current host and target character set is `ISO-8859-1'.
9183 For the sake of printing this manual, let's use @sc{ascii} as our
9184 initial character set:
9186 (@value{GDBP}) set charset ASCII
9187 (@value{GDBP}) show charset
9188 The current host and target character set is `ASCII'.
9192 Let's assume that @sc{ascii} is indeed the correct character set for our
9193 host system --- in other words, let's assume that if @value{GDBN} prints
9194 characters using the @sc{ascii} character set, our terminal will display
9195 them properly. Since our current target character set is also
9196 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9199 (@value{GDBP}) print ascii_hello
9200 $1 = 0x401698 "Hello, world!\n"
9201 (@value{GDBP}) print ascii_hello[0]
9206 @value{GDBN} uses the target character set for character and string
9207 literals you use in expressions:
9210 (@value{GDBP}) print '+'
9215 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9218 @value{GDBN} relies on the user to tell it which character set the
9219 target program uses. If we print @code{ibm1047_hello} while our target
9220 character set is still @sc{ascii}, we get jibberish:
9223 (@value{GDBP}) print ibm1047_hello
9224 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9225 (@value{GDBP}) print ibm1047_hello[0]
9230 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9231 @value{GDBN} tells us the character sets it supports:
9234 (@value{GDBP}) set target-charset
9235 ASCII EBCDIC-US IBM1047 ISO-8859-1
9236 (@value{GDBP}) set target-charset
9239 We can select @sc{ibm1047} as our target character set, and examine the
9240 program's strings again. Now the @sc{ascii} string is wrong, but
9241 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9242 target character set, @sc{ibm1047}, to the host character set,
9243 @sc{ascii}, and they display correctly:
9246 (@value{GDBP}) set target-charset IBM1047
9247 (@value{GDBP}) show charset
9248 The current host character set is `ASCII'.
9249 The current target character set is `IBM1047'.
9250 (@value{GDBP}) print ascii_hello
9251 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9252 (@value{GDBP}) print ascii_hello[0]
9254 (@value{GDBP}) print ibm1047_hello
9255 $8 = 0x4016a8 "Hello, world!\n"
9256 (@value{GDBP}) print ibm1047_hello[0]
9261 As above, @value{GDBN} uses the target character set for character and
9262 string literals you use in expressions:
9265 (@value{GDBP}) print '+'
9270 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9273 @node Caching Remote Data
9274 @section Caching Data of Remote Targets
9275 @cindex caching data of remote targets
9277 @value{GDBN} caches data exchanged between the debugger and a
9278 remote target (@pxref{Remote Debugging}). Such caching generally improves
9279 performance, because it reduces the overhead of the remote protocol by
9280 bundling memory reads and writes into large chunks. Unfortunately, simply
9281 caching everything would lead to incorrect results, since @value{GDBN}
9282 does not necessarily know anything about volatile values, memory-mapped I/O
9283 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9284 memory can be changed @emph{while} a gdb command is executing.
9285 Therefore, by default, @value{GDBN} only caches data
9286 known to be on the stack@footnote{In non-stop mode, it is moderately
9287 rare for a running thread to modify the stack of a stopped thread
9288 in a way that would interfere with a backtrace, and caching of
9289 stack reads provides a significant speed up of remote backtraces.}.
9290 Other regions of memory can be explicitly marked as
9291 cacheable; see @pxref{Memory Region Attributes}.
9294 @kindex set remotecache
9295 @item set remotecache on
9296 @itemx set remotecache off
9297 This option no longer does anything; it exists for compatibility
9300 @kindex show remotecache
9301 @item show remotecache
9302 Show the current state of the obsolete remotecache flag.
9304 @kindex set stack-cache
9305 @item set stack-cache on
9306 @itemx set stack-cache off
9307 Enable or disable caching of stack accesses. When @code{ON}, use
9308 caching. By default, this option is @code{ON}.
9310 @kindex show stack-cache
9311 @item show stack-cache
9312 Show the current state of data caching for memory accesses.
9315 @item info dcache @r{[}line@r{]}
9316 Print the information about the data cache performance. The
9317 information displayed includes the dcache width and depth, and for
9318 each cache line, its number, address, and how many times it was
9319 referenced. This command is useful for debugging the data cache
9322 If a line number is specified, the contents of that line will be
9326 @node Searching Memory
9327 @section Search Memory
9328 @cindex searching memory
9330 Memory can be searched for a particular sequence of bytes with the
9331 @code{find} command.
9335 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9336 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9337 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9338 etc. The search begins at address @var{start_addr} and continues for either
9339 @var{len} bytes or through to @var{end_addr} inclusive.
9342 @var{s} and @var{n} are optional parameters.
9343 They may be specified in either order, apart or together.
9346 @item @var{s}, search query size
9347 The size of each search query value.
9353 halfwords (two bytes)
9357 giant words (eight bytes)
9360 All values are interpreted in the current language.
9361 This means, for example, that if the current source language is C/C@t{++}
9362 then searching for the string ``hello'' includes the trailing '\0'.
9364 If the value size is not specified, it is taken from the
9365 value's type in the current language.
9366 This is useful when one wants to specify the search
9367 pattern as a mixture of types.
9368 Note that this means, for example, that in the case of C-like languages
9369 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9370 which is typically four bytes.
9372 @item @var{n}, maximum number of finds
9373 The maximum number of matches to print. The default is to print all finds.
9376 You can use strings as search values. Quote them with double-quotes
9378 The string value is copied into the search pattern byte by byte,
9379 regardless of the endianness of the target and the size specification.
9381 The address of each match found is printed as well as a count of the
9382 number of matches found.
9384 The address of the last value found is stored in convenience variable
9386 A count of the number of matches is stored in @samp{$numfound}.
9388 For example, if stopped at the @code{printf} in this function:
9394 static char hello[] = "hello-hello";
9395 static struct @{ char c; short s; int i; @}
9396 __attribute__ ((packed)) mixed
9397 = @{ 'c', 0x1234, 0x87654321 @};
9398 printf ("%s\n", hello);
9403 you get during debugging:
9406 (gdb) find &hello[0], +sizeof(hello), "hello"
9407 0x804956d <hello.1620+6>
9409 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9410 0x8049567 <hello.1620>
9411 0x804956d <hello.1620+6>
9413 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9414 0x8049567 <hello.1620>
9416 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9417 0x8049560 <mixed.1625>
9419 (gdb) print $numfound
9422 $2 = (void *) 0x8049560
9425 @node Optimized Code
9426 @chapter Debugging Optimized Code
9427 @cindex optimized code, debugging
9428 @cindex debugging optimized code
9430 Almost all compilers support optimization. With optimization
9431 disabled, the compiler generates assembly code that corresponds
9432 directly to your source code, in a simplistic way. As the compiler
9433 applies more powerful optimizations, the generated assembly code
9434 diverges from your original source code. With help from debugging
9435 information generated by the compiler, @value{GDBN} can map from
9436 the running program back to constructs from your original source.
9438 @value{GDBN} is more accurate with optimization disabled. If you
9439 can recompile without optimization, it is easier to follow the
9440 progress of your program during debugging. But, there are many cases
9441 where you may need to debug an optimized version.
9443 When you debug a program compiled with @samp{-g -O}, remember that the
9444 optimizer has rearranged your code; the debugger shows you what is
9445 really there. Do not be too surprised when the execution path does not
9446 exactly match your source file! An extreme example: if you define a
9447 variable, but never use it, @value{GDBN} never sees that
9448 variable---because the compiler optimizes it out of existence.
9450 Some things do not work as well with @samp{-g -O} as with just
9451 @samp{-g}, particularly on machines with instruction scheduling. If in
9452 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9453 please report it to us as a bug (including a test case!).
9454 @xref{Variables}, for more information about debugging optimized code.
9457 * Inline Functions:: How @value{GDBN} presents inlining
9460 @node Inline Functions
9461 @section Inline Functions
9462 @cindex inline functions, debugging
9464 @dfn{Inlining} is an optimization that inserts a copy of the function
9465 body directly at each call site, instead of jumping to a shared
9466 routine. @value{GDBN} displays inlined functions just like
9467 non-inlined functions. They appear in backtraces. You can view their
9468 arguments and local variables, step into them with @code{step}, skip
9469 them with @code{next}, and escape from them with @code{finish}.
9470 You can check whether a function was inlined by using the
9471 @code{info frame} command.
9473 For @value{GDBN} to support inlined functions, the compiler must
9474 record information about inlining in the debug information ---
9475 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9476 other compilers do also. @value{GDBN} only supports inlined functions
9477 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9478 do not emit two required attributes (@samp{DW_AT_call_file} and
9479 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9480 function calls with earlier versions of @value{NGCC}. It instead
9481 displays the arguments and local variables of inlined functions as
9482 local variables in the caller.
9484 The body of an inlined function is directly included at its call site;
9485 unlike a non-inlined function, there are no instructions devoted to
9486 the call. @value{GDBN} still pretends that the call site and the
9487 start of the inlined function are different instructions. Stepping to
9488 the call site shows the call site, and then stepping again shows
9489 the first line of the inlined function, even though no additional
9490 instructions are executed.
9492 This makes source-level debugging much clearer; you can see both the
9493 context of the call and then the effect of the call. Only stepping by
9494 a single instruction using @code{stepi} or @code{nexti} does not do
9495 this; single instruction steps always show the inlined body.
9497 There are some ways that @value{GDBN} does not pretend that inlined
9498 function calls are the same as normal calls:
9502 You cannot set breakpoints on inlined functions. @value{GDBN}
9503 either reports that there is no symbol with that name, or else sets the
9504 breakpoint only on non-inlined copies of the function. This limitation
9505 will be removed in a future version of @value{GDBN}; until then,
9506 set a breakpoint by line number on the first line of the inlined
9510 Setting breakpoints at the call site of an inlined function may not
9511 work, because the call site does not contain any code. @value{GDBN}
9512 may incorrectly move the breakpoint to the next line of the enclosing
9513 function, after the call. This limitation will be removed in a future
9514 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9515 or inside the inlined function instead.
9518 @value{GDBN} cannot locate the return value of inlined calls after
9519 using the @code{finish} command. This is a limitation of compiler-generated
9520 debugging information; after @code{finish}, you can step to the next line
9521 and print a variable where your program stored the return value.
9527 @chapter C Preprocessor Macros
9529 Some languages, such as C and C@t{++}, provide a way to define and invoke
9530 ``preprocessor macros'' which expand into strings of tokens.
9531 @value{GDBN} can evaluate expressions containing macro invocations, show
9532 the result of macro expansion, and show a macro's definition, including
9533 where it was defined.
9535 You may need to compile your program specially to provide @value{GDBN}
9536 with information about preprocessor macros. Most compilers do not
9537 include macros in their debugging information, even when you compile
9538 with the @option{-g} flag. @xref{Compilation}.
9540 A program may define a macro at one point, remove that definition later,
9541 and then provide a different definition after that. Thus, at different
9542 points in the program, a macro may have different definitions, or have
9543 no definition at all. If there is a current stack frame, @value{GDBN}
9544 uses the macros in scope at that frame's source code line. Otherwise,
9545 @value{GDBN} uses the macros in scope at the current listing location;
9548 Whenever @value{GDBN} evaluates an expression, it always expands any
9549 macro invocations present in the expression. @value{GDBN} also provides
9550 the following commands for working with macros explicitly.
9554 @kindex macro expand
9555 @cindex macro expansion, showing the results of preprocessor
9556 @cindex preprocessor macro expansion, showing the results of
9557 @cindex expanding preprocessor macros
9558 @item macro expand @var{expression}
9559 @itemx macro exp @var{expression}
9560 Show the results of expanding all preprocessor macro invocations in
9561 @var{expression}. Since @value{GDBN} simply expands macros, but does
9562 not parse the result, @var{expression} need not be a valid expression;
9563 it can be any string of tokens.
9566 @item macro expand-once @var{expression}
9567 @itemx macro exp1 @var{expression}
9568 @cindex expand macro once
9569 @i{(This command is not yet implemented.)} Show the results of
9570 expanding those preprocessor macro invocations that appear explicitly in
9571 @var{expression}. Macro invocations appearing in that expansion are
9572 left unchanged. This command allows you to see the effect of a
9573 particular macro more clearly, without being confused by further
9574 expansions. Since @value{GDBN} simply expands macros, but does not
9575 parse the result, @var{expression} need not be a valid expression; it
9576 can be any string of tokens.
9579 @cindex macro definition, showing
9580 @cindex definition, showing a macro's
9581 @item info macro @var{macro}
9582 Show the definition of the macro named @var{macro}, and describe the
9583 source location or compiler command-line where that definition was established.
9585 @kindex macro define
9586 @cindex user-defined macros
9587 @cindex defining macros interactively
9588 @cindex macros, user-defined
9589 @item macro define @var{macro} @var{replacement-list}
9590 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9591 Introduce a definition for a preprocessor macro named @var{macro},
9592 invocations of which are replaced by the tokens given in
9593 @var{replacement-list}. The first form of this command defines an
9594 ``object-like'' macro, which takes no arguments; the second form
9595 defines a ``function-like'' macro, which takes the arguments given in
9598 A definition introduced by this command is in scope in every
9599 expression evaluated in @value{GDBN}, until it is removed with the
9600 @code{macro undef} command, described below. The definition overrides
9601 all definitions for @var{macro} present in the program being debugged,
9602 as well as any previous user-supplied definition.
9605 @item macro undef @var{macro}
9606 Remove any user-supplied definition for the macro named @var{macro}.
9607 This command only affects definitions provided with the @code{macro
9608 define} command, described above; it cannot remove definitions present
9609 in the program being debugged.
9613 List all the macros defined using the @code{macro define} command.
9616 @cindex macros, example of debugging with
9617 Here is a transcript showing the above commands in action. First, we
9618 show our source files:
9626 #define ADD(x) (M + x)
9631 printf ("Hello, world!\n");
9633 printf ("We're so creative.\n");
9635 printf ("Goodbye, world!\n");
9642 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9643 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9644 compiler includes information about preprocessor macros in the debugging
9648 $ gcc -gdwarf-2 -g3 sample.c -o sample
9652 Now, we start @value{GDBN} on our sample program:
9656 GNU gdb 2002-05-06-cvs
9657 Copyright 2002 Free Software Foundation, Inc.
9658 GDB is free software, @dots{}
9662 We can expand macros and examine their definitions, even when the
9663 program is not running. @value{GDBN} uses the current listing position
9664 to decide which macro definitions are in scope:
9667 (@value{GDBP}) list main
9670 5 #define ADD(x) (M + x)
9675 10 printf ("Hello, world!\n");
9677 12 printf ("We're so creative.\n");
9678 (@value{GDBP}) info macro ADD
9679 Defined at /home/jimb/gdb/macros/play/sample.c:5
9680 #define ADD(x) (M + x)
9681 (@value{GDBP}) info macro Q
9682 Defined at /home/jimb/gdb/macros/play/sample.h:1
9683 included at /home/jimb/gdb/macros/play/sample.c:2
9685 (@value{GDBP}) macro expand ADD(1)
9686 expands to: (42 + 1)
9687 (@value{GDBP}) macro expand-once ADD(1)
9688 expands to: once (M + 1)
9692 In the example above, note that @code{macro expand-once} expands only
9693 the macro invocation explicit in the original text --- the invocation of
9694 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9695 which was introduced by @code{ADD}.
9697 Once the program is running, @value{GDBN} uses the macro definitions in
9698 force at the source line of the current stack frame:
9701 (@value{GDBP}) break main
9702 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9704 Starting program: /home/jimb/gdb/macros/play/sample
9706 Breakpoint 1, main () at sample.c:10
9707 10 printf ("Hello, world!\n");
9711 At line 10, the definition of the macro @code{N} at line 9 is in force:
9714 (@value{GDBP}) info macro N
9715 Defined at /home/jimb/gdb/macros/play/sample.c:9
9717 (@value{GDBP}) macro expand N Q M
9719 (@value{GDBP}) print N Q M
9724 As we step over directives that remove @code{N}'s definition, and then
9725 give it a new definition, @value{GDBN} finds the definition (or lack
9726 thereof) in force at each point:
9731 12 printf ("We're so creative.\n");
9732 (@value{GDBP}) info macro N
9733 The symbol `N' has no definition as a C/C++ preprocessor macro
9734 at /home/jimb/gdb/macros/play/sample.c:12
9737 14 printf ("Goodbye, world!\n");
9738 (@value{GDBP}) info macro N
9739 Defined at /home/jimb/gdb/macros/play/sample.c:13
9741 (@value{GDBP}) macro expand N Q M
9742 expands to: 1729 < 42
9743 (@value{GDBP}) print N Q M
9748 In addition to source files, macros can be defined on the compilation command
9749 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9750 such a way, @value{GDBN} displays the location of their definition as line zero
9751 of the source file submitted to the compiler.
9754 (@value{GDBP}) info macro __STDC__
9755 Defined at /home/jimb/gdb/macros/play/sample.c:0
9762 @chapter Tracepoints
9763 @c This chapter is based on the documentation written by Michael
9764 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9767 In some applications, it is not feasible for the debugger to interrupt
9768 the program's execution long enough for the developer to learn
9769 anything helpful about its behavior. If the program's correctness
9770 depends on its real-time behavior, delays introduced by a debugger
9771 might cause the program to change its behavior drastically, or perhaps
9772 fail, even when the code itself is correct. It is useful to be able
9773 to observe the program's behavior without interrupting it.
9775 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9776 specify locations in the program, called @dfn{tracepoints}, and
9777 arbitrary expressions to evaluate when those tracepoints are reached.
9778 Later, using the @code{tfind} command, you can examine the values
9779 those expressions had when the program hit the tracepoints. The
9780 expressions may also denote objects in memory---structures or arrays,
9781 for example---whose values @value{GDBN} should record; while visiting
9782 a particular tracepoint, you may inspect those objects as if they were
9783 in memory at that moment. However, because @value{GDBN} records these
9784 values without interacting with you, it can do so quickly and
9785 unobtrusively, hopefully not disturbing the program's behavior.
9787 The tracepoint facility is currently available only for remote
9788 targets. @xref{Targets}. In addition, your remote target must know
9789 how to collect trace data. This functionality is implemented in the
9790 remote stub; however, none of the stubs distributed with @value{GDBN}
9791 support tracepoints as of this writing. The format of the remote
9792 packets used to implement tracepoints are described in @ref{Tracepoint
9795 It is also possible to get trace data from a file, in a manner reminiscent
9796 of corefiles; you specify the filename, and use @code{tfind} to search
9797 through the file. @xref{Trace Files}, for more details.
9799 This chapter describes the tracepoint commands and features.
9803 * Analyze Collected Data::
9804 * Tracepoint Variables::
9808 @node Set Tracepoints
9809 @section Commands to Set Tracepoints
9811 Before running such a @dfn{trace experiment}, an arbitrary number of
9812 tracepoints can be set. A tracepoint is actually a special type of
9813 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9814 standard breakpoint commands. For instance, as with breakpoints,
9815 tracepoint numbers are successive integers starting from one, and many
9816 of the commands associated with tracepoints take the tracepoint number
9817 as their argument, to identify which tracepoint to work on.
9819 For each tracepoint, you can specify, in advance, some arbitrary set
9820 of data that you want the target to collect in the trace buffer when
9821 it hits that tracepoint. The collected data can include registers,
9822 local variables, or global data. Later, you can use @value{GDBN}
9823 commands to examine the values these data had at the time the
9826 Tracepoints do not support every breakpoint feature. Ignore counts on
9827 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9828 commands when they are hit. Tracepoints may not be thread-specific
9831 @cindex fast tracepoints
9832 Some targets may support @dfn{fast tracepoints}, which are inserted in
9833 a different way (such as with a jump instead of a trap), that is
9834 faster but possibly restricted in where they may be installed.
9836 @cindex static tracepoints
9837 @cindex markers, static tracepoints
9838 @cindex probing markers, static tracepoints
9839 Regular and fast tracepoints are dynamic tracing facilities, meaning
9840 that they can be used to insert tracepoints at (almost) any location
9841 in the target. Some targets may also support controlling @dfn{static
9842 tracepoints} from @value{GDBN}. With static tracing, a set of
9843 instrumentation points, also known as @dfn{markers}, are embedded in
9844 the target program, and can be activated or deactivated by name or
9845 address. These are usually placed at locations which facilitate
9846 investigating what the target is actually doing. @value{GDBN}'s
9847 support for static tracing includes being able to list instrumentation
9848 points, and attach them with @value{GDBN} defined high level
9849 tracepoints that expose the whole range of convenience of
9850 @value{GDBN}'s tracepoints support. Namely, support for collecting
9851 registers values and values of global or local (to the instrumentation
9852 point) variables; tracepoint conditions and trace state variables.
9853 The act of installing a @value{GDBN} static tracepoint on an
9854 instrumentation point, or marker, is referred to as @dfn{probing} a
9855 static tracepoint marker.
9857 @code{gdbserver} supports tracepoints on some target systems.
9858 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9860 This section describes commands to set tracepoints and associated
9861 conditions and actions.
9864 * Create and Delete Tracepoints::
9865 * Enable and Disable Tracepoints::
9866 * Tracepoint Passcounts::
9867 * Tracepoint Conditions::
9868 * Trace State Variables::
9869 * Tracepoint Actions::
9870 * Listing Tracepoints::
9871 * Listing Static Tracepoint Markers::
9872 * Starting and Stopping Trace Experiments::
9873 * Tracepoint Restrictions::
9876 @node Create and Delete Tracepoints
9877 @subsection Create and Delete Tracepoints
9880 @cindex set tracepoint
9882 @item trace @var{location}
9883 The @code{trace} command is very similar to the @code{break} command.
9884 Its argument @var{location} can be a source line, a function name, or
9885 an address in the target program. @xref{Specify Location}. The
9886 @code{trace} command defines a tracepoint, which is a point in the
9887 target program where the debugger will briefly stop, collect some
9888 data, and then allow the program to continue. Setting a tracepoint or
9889 changing its actions doesn't take effect until the next @code{tstart}
9890 command, and once a trace experiment is running, further changes will
9891 not have any effect until the next trace experiment starts.
9893 Here are some examples of using the @code{trace} command:
9896 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9898 (@value{GDBP}) @b{trace +2} // 2 lines forward
9900 (@value{GDBP}) @b{trace my_function} // first source line of function
9902 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9904 (@value{GDBP}) @b{trace *0x2117c4} // an address
9908 You can abbreviate @code{trace} as @code{tr}.
9910 @item trace @var{location} if @var{cond}
9911 Set a tracepoint with condition @var{cond}; evaluate the expression
9912 @var{cond} each time the tracepoint is reached, and collect data only
9913 if the value is nonzero---that is, if @var{cond} evaluates as true.
9914 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9915 information on tracepoint conditions.
9917 @item ftrace @var{location} [ if @var{cond} ]
9918 @cindex set fast tracepoint
9919 @cindex fast tracepoints, setting
9921 The @code{ftrace} command sets a fast tracepoint. For targets that
9922 support them, fast tracepoints will use a more efficient but possibly
9923 less general technique to trigger data collection, such as a jump
9924 instruction instead of a trap, or some sort of hardware support. It
9925 may not be possible to create a fast tracepoint at the desired
9926 location, in which case the command will exit with an explanatory
9929 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9932 @item strace @var{location} [ if @var{cond} ]
9933 @cindex set static tracepoint
9934 @cindex static tracepoints, setting
9935 @cindex probe static tracepoint marker
9937 The @code{strace} command sets a static tracepoint. For targets that
9938 support it, setting a static tracepoint probes a static
9939 instrumentation point, or marker, found at @var{location}. It may not
9940 be possible to set a static tracepoint at the desired location, in
9941 which case the command will exit with an explanatory message.
9943 @value{GDBN} handles arguments to @code{strace} exactly as for
9944 @code{trace}, with the addition that the user can also specify
9945 @code{-m @var{marker}} as @var{location}. This probes the marker
9946 identified by the @var{marker} string identifier. This identifier
9947 depends on the static tracepoint backend library your program is
9948 using. You can find all the marker identifiers in the @samp{ID} field
9949 of the @code{info static-tracepoint-markers} command output.
9950 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9951 Markers}. For example, in the following small program using the UST
9957 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9962 the marker id is composed of joining the first two arguments to the
9963 @code{trace_mark} call with a slash, which translates to:
9966 (@value{GDBP}) info static-tracepoint-markers
9967 Cnt Enb ID Address What
9968 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9974 so you may probe the marker above with:
9977 (@value{GDBP}) strace -m ust/bar33
9980 Static tracepoints accept an extra collect action --- @code{collect
9981 $_sdata}. This collects arbitrary user data passed in the probe point
9982 call to the tracing library. In the UST example above, you'll see
9983 that the third argument to @code{trace_mark} is a printf-like format
9984 string. The user data is then the result of running that formating
9985 string against the following arguments. Note that @code{info
9986 static-tracepoint-markers} command output lists that format string in
9987 the @samp{Data:} field.
9989 You can inspect this data when analyzing the trace buffer, by printing
9990 the $_sdata variable like any other variable available to
9991 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9994 @cindex last tracepoint number
9995 @cindex recent tracepoint number
9996 @cindex tracepoint number
9997 The convenience variable @code{$tpnum} records the tracepoint number
9998 of the most recently set tracepoint.
10000 @kindex delete tracepoint
10001 @cindex tracepoint deletion
10002 @item delete tracepoint @r{[}@var{num}@r{]}
10003 Permanently delete one or more tracepoints. With no argument, the
10004 default is to delete all tracepoints. Note that the regular
10005 @code{delete} command can remove tracepoints also.
10010 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10012 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10016 You can abbreviate this command as @code{del tr}.
10019 @node Enable and Disable Tracepoints
10020 @subsection Enable and Disable Tracepoints
10022 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10025 @kindex disable tracepoint
10026 @item disable tracepoint @r{[}@var{num}@r{]}
10027 Disable tracepoint @var{num}, or all tracepoints if no argument
10028 @var{num} is given. A disabled tracepoint will have no effect during
10029 the next trace experiment, but it is not forgotten. You can re-enable
10030 a disabled tracepoint using the @code{enable tracepoint} command.
10032 @kindex enable tracepoint
10033 @item enable tracepoint @r{[}@var{num}@r{]}
10034 Enable tracepoint @var{num}, or all tracepoints. The enabled
10035 tracepoints will become effective the next time a trace experiment is
10039 @node Tracepoint Passcounts
10040 @subsection Tracepoint Passcounts
10044 @cindex tracepoint pass count
10045 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10046 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10047 automatically stop a trace experiment. If a tracepoint's passcount is
10048 @var{n}, then the trace experiment will be automatically stopped on
10049 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10050 @var{num} is not specified, the @code{passcount} command sets the
10051 passcount of the most recently defined tracepoint. If no passcount is
10052 given, the trace experiment will run until stopped explicitly by the
10058 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10059 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10061 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10062 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10063 (@value{GDBP}) @b{trace foo}
10064 (@value{GDBP}) @b{pass 3}
10065 (@value{GDBP}) @b{trace bar}
10066 (@value{GDBP}) @b{pass 2}
10067 (@value{GDBP}) @b{trace baz}
10068 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10069 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10070 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10071 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10075 @node Tracepoint Conditions
10076 @subsection Tracepoint Conditions
10077 @cindex conditional tracepoints
10078 @cindex tracepoint conditions
10080 The simplest sort of tracepoint collects data every time your program
10081 reaches a specified place. You can also specify a @dfn{condition} for
10082 a tracepoint. A condition is just a Boolean expression in your
10083 programming language (@pxref{Expressions, ,Expressions}). A
10084 tracepoint with a condition evaluates the expression each time your
10085 program reaches it, and data collection happens only if the condition
10088 Tracepoint conditions can be specified when a tracepoint is set, by
10089 using @samp{if} in the arguments to the @code{trace} command.
10090 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10091 also be set or changed at any time with the @code{condition} command,
10092 just as with breakpoints.
10094 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10095 the conditional expression itself. Instead, @value{GDBN} encodes the
10096 expression into an agent expression (@pxref{Agent Expressions})
10097 suitable for execution on the target, independently of @value{GDBN}.
10098 Global variables become raw memory locations, locals become stack
10099 accesses, and so forth.
10101 For instance, suppose you have a function that is usually called
10102 frequently, but should not be called after an error has occurred. You
10103 could use the following tracepoint command to collect data about calls
10104 of that function that happen while the error code is propagating
10105 through the program; an unconditional tracepoint could end up
10106 collecting thousands of useless trace frames that you would have to
10110 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10113 @node Trace State Variables
10114 @subsection Trace State Variables
10115 @cindex trace state variables
10117 A @dfn{trace state variable} is a special type of variable that is
10118 created and managed by target-side code. The syntax is the same as
10119 that for GDB's convenience variables (a string prefixed with ``$''),
10120 but they are stored on the target. They must be created explicitly,
10121 using a @code{tvariable} command. They are always 64-bit signed
10124 Trace state variables are remembered by @value{GDBN}, and downloaded
10125 to the target along with tracepoint information when the trace
10126 experiment starts. There are no intrinsic limits on the number of
10127 trace state variables, beyond memory limitations of the target.
10129 @cindex convenience variables, and trace state variables
10130 Although trace state variables are managed by the target, you can use
10131 them in print commands and expressions as if they were convenience
10132 variables; @value{GDBN} will get the current value from the target
10133 while the trace experiment is running. Trace state variables share
10134 the same namespace as other ``$'' variables, which means that you
10135 cannot have trace state variables with names like @code{$23} or
10136 @code{$pc}, nor can you have a trace state variable and a convenience
10137 variable with the same name.
10141 @item tvariable $@var{name} [ = @var{expression} ]
10143 The @code{tvariable} command creates a new trace state variable named
10144 @code{$@var{name}}, and optionally gives it an initial value of
10145 @var{expression}. @var{expression} is evaluated when this command is
10146 entered; the result will be converted to an integer if possible,
10147 otherwise @value{GDBN} will report an error. A subsequent
10148 @code{tvariable} command specifying the same name does not create a
10149 variable, but instead assigns the supplied initial value to the
10150 existing variable of that name, overwriting any previous initial
10151 value. The default initial value is 0.
10153 @item info tvariables
10154 @kindex info tvariables
10155 List all the trace state variables along with their initial values.
10156 Their current values may also be displayed, if the trace experiment is
10159 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10160 @kindex delete tvariable
10161 Delete the given trace state variables, or all of them if no arguments
10166 @node Tracepoint Actions
10167 @subsection Tracepoint Action Lists
10171 @cindex tracepoint actions
10172 @item actions @r{[}@var{num}@r{]}
10173 This command will prompt for a list of actions to be taken when the
10174 tracepoint is hit. If the tracepoint number @var{num} is not
10175 specified, this command sets the actions for the one that was most
10176 recently defined (so that you can define a tracepoint and then say
10177 @code{actions} without bothering about its number). You specify the
10178 actions themselves on the following lines, one action at a time, and
10179 terminate the actions list with a line containing just @code{end}. So
10180 far, the only defined actions are @code{collect}, @code{teval}, and
10181 @code{while-stepping}.
10183 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10184 Commands, ,Breakpoint Command Lists}), except that only the defined
10185 actions are allowed; any other @value{GDBN} command is rejected.
10187 @cindex remove actions from a tracepoint
10188 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10189 and follow it immediately with @samp{end}.
10192 (@value{GDBP}) @b{collect @var{data}} // collect some data
10194 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10196 (@value{GDBP}) @b{end} // signals the end of actions.
10199 In the following example, the action list begins with @code{collect}
10200 commands indicating the things to be collected when the tracepoint is
10201 hit. Then, in order to single-step and collect additional data
10202 following the tracepoint, a @code{while-stepping} command is used,
10203 followed by the list of things to be collected after each step in a
10204 sequence of single steps. The @code{while-stepping} command is
10205 terminated by its own separate @code{end} command. Lastly, the action
10206 list is terminated by an @code{end} command.
10209 (@value{GDBP}) @b{trace foo}
10210 (@value{GDBP}) @b{actions}
10211 Enter actions for tracepoint 1, one per line:
10214 > while-stepping 12
10215 > collect $pc, arr[i]
10220 @kindex collect @r{(tracepoints)}
10221 @item collect @var{expr1}, @var{expr2}, @dots{}
10222 Collect values of the given expressions when the tracepoint is hit.
10223 This command accepts a comma-separated list of any valid expressions.
10224 In addition to global, static, or local variables, the following
10225 special arguments are supported:
10229 Collect all registers.
10232 Collect all function arguments.
10235 Collect all local variables.
10238 @vindex $_sdata@r{, collect}
10239 Collect static tracepoint marker specific data. Only available for
10240 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10241 Lists}. On the UST static tracepoints library backend, an
10242 instrumentation point resembles a @code{printf} function call. The
10243 tracing library is able to collect user specified data formatted to a
10244 character string using the format provided by the programmer that
10245 instrumented the program. Other backends have similar mechanisms.
10246 Here's an example of a UST marker call:
10249 const char master_name[] = "$your_name";
10250 trace_mark(channel1, marker1, "hello %s", master_name)
10253 In this case, collecting @code{$_sdata} collects the string
10254 @samp{hello $yourname}. When analyzing the trace buffer, you can
10255 inspect @samp{$_sdata} like any other variable available to
10259 You can give several consecutive @code{collect} commands, each one
10260 with a single argument, or one @code{collect} command with several
10261 arguments separated by commas; the effect is the same.
10263 The command @code{info scope} (@pxref{Symbols, info scope}) is
10264 particularly useful for figuring out what data to collect.
10266 @kindex teval @r{(tracepoints)}
10267 @item teval @var{expr1}, @var{expr2}, @dots{}
10268 Evaluate the given expressions when the tracepoint is hit. This
10269 command accepts a comma-separated list of expressions. The results
10270 are discarded, so this is mainly useful for assigning values to trace
10271 state variables (@pxref{Trace State Variables}) without adding those
10272 values to the trace buffer, as would be the case if the @code{collect}
10275 @kindex while-stepping @r{(tracepoints)}
10276 @item while-stepping @var{n}
10277 Perform @var{n} single-step instruction traces after the tracepoint,
10278 collecting new data after each step. The @code{while-stepping}
10279 command is followed by the list of what to collect while stepping
10280 (followed by its own @code{end} command):
10283 > while-stepping 12
10284 > collect $regs, myglobal
10290 Note that @code{$pc} is not automatically collected by
10291 @code{while-stepping}; you need to explicitly collect that register if
10292 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10295 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10296 @kindex set default-collect
10297 @cindex default collection action
10298 This variable is a list of expressions to collect at each tracepoint
10299 hit. It is effectively an additional @code{collect} action prepended
10300 to every tracepoint action list. The expressions are parsed
10301 individually for each tracepoint, so for instance a variable named
10302 @code{xyz} may be interpreted as a global for one tracepoint, and a
10303 local for another, as appropriate to the tracepoint's location.
10305 @item show default-collect
10306 @kindex show default-collect
10307 Show the list of expressions that are collected by default at each
10312 @node Listing Tracepoints
10313 @subsection Listing Tracepoints
10316 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10317 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10318 @cindex information about tracepoints
10319 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10320 Display information about the tracepoint @var{num}. If you don't
10321 specify a tracepoint number, displays information about all the
10322 tracepoints defined so far. The format is similar to that used for
10323 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10324 command, simply restricting itself to tracepoints.
10326 A tracepoint's listing may include additional information specific to
10331 its passcount as given by the @code{passcount @var{n}} command
10335 (@value{GDBP}) @b{info trace}
10336 Num Type Disp Enb Address What
10337 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10339 collect globfoo, $regs
10348 This command can be abbreviated @code{info tp}.
10351 @node Listing Static Tracepoint Markers
10352 @subsection Listing Static Tracepoint Markers
10355 @kindex info static-tracepoint-markers
10356 @cindex information about static tracepoint markers
10357 @item info static-tracepoint-markers
10358 Display information about all static tracepoint markers defined in the
10361 For each marker, the following columns are printed:
10365 An incrementing counter, output to help readability. This is not a
10368 The marker ID, as reported by the target.
10369 @item Enabled or Disabled
10370 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10371 that are not enabled.
10373 Where the marker is in your program, as a memory address.
10375 Where the marker is in the source for your program, as a file and line
10376 number. If the debug information included in the program does not
10377 allow @value{GDBN} to locate the source of the marker, this column
10378 will be left blank.
10382 In addition, the following information may be printed for each marker:
10386 User data passed to the tracing library by the marker call. In the
10387 UST backend, this is the format string passed as argument to the
10389 @item Static tracepoints probing the marker
10390 The list of static tracepoints attached to the marker.
10394 (@value{GDBP}) info static-tracepoint-markers
10395 Cnt ID Enb Address What
10396 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10397 Data: number1 %d number2 %d
10398 Probed by static tracepoints: #2
10399 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10405 @node Starting and Stopping Trace Experiments
10406 @subsection Starting and Stopping Trace Experiments
10410 @cindex start a new trace experiment
10411 @cindex collected data discarded
10413 This command takes no arguments. It starts the trace experiment, and
10414 begins collecting data. This has the side effect of discarding all
10415 the data collected in the trace buffer during the previous trace
10419 @cindex stop a running trace experiment
10421 This command takes no arguments. It ends the trace experiment, and
10422 stops collecting data.
10424 @strong{Note}: a trace experiment and data collection may stop
10425 automatically if any tracepoint's passcount is reached
10426 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10429 @cindex status of trace data collection
10430 @cindex trace experiment, status of
10432 This command displays the status of the current trace data
10436 Here is an example of the commands we described so far:
10439 (@value{GDBP}) @b{trace gdb_c_test}
10440 (@value{GDBP}) @b{actions}
10441 Enter actions for tracepoint #1, one per line.
10442 > collect $regs,$locals,$args
10443 > while-stepping 11
10447 (@value{GDBP}) @b{tstart}
10448 [time passes @dots{}]
10449 (@value{GDBP}) @b{tstop}
10452 @anchor{disconnected tracing}
10453 @cindex disconnected tracing
10454 You can choose to continue running the trace experiment even if
10455 @value{GDBN} disconnects from the target, voluntarily or
10456 involuntarily. For commands such as @code{detach}, the debugger will
10457 ask what you want to do with the trace. But for unexpected
10458 terminations (@value{GDBN} crash, network outage), it would be
10459 unfortunate to lose hard-won trace data, so the variable
10460 @code{disconnected-tracing} lets you decide whether the trace should
10461 continue running without @value{GDBN}.
10464 @item set disconnected-tracing on
10465 @itemx set disconnected-tracing off
10466 @kindex set disconnected-tracing
10467 Choose whether a tracing run should continue to run if @value{GDBN}
10468 has disconnected from the target. Note that @code{detach} or
10469 @code{quit} will ask you directly what to do about a running trace no
10470 matter what this variable's setting, so the variable is mainly useful
10471 for handling unexpected situations, such as loss of the network.
10473 @item show disconnected-tracing
10474 @kindex show disconnected-tracing
10475 Show the current choice for disconnected tracing.
10479 When you reconnect to the target, the trace experiment may or may not
10480 still be running; it might have filled the trace buffer in the
10481 meantime, or stopped for one of the other reasons. If it is running,
10482 it will continue after reconnection.
10484 Upon reconnection, the target will upload information about the
10485 tracepoints in effect. @value{GDBN} will then compare that
10486 information to the set of tracepoints currently defined, and attempt
10487 to match them up, allowing for the possibility that the numbers may
10488 have changed due to creation and deletion in the meantime. If one of
10489 the target's tracepoints does not match any in @value{GDBN}, the
10490 debugger will create a new tracepoint, so that you have a number with
10491 which to specify that tracepoint. This matching-up process is
10492 necessarily heuristic, and it may result in useless tracepoints being
10493 created; you may simply delete them if they are of no use.
10495 @cindex circular trace buffer
10496 If your target agent supports a @dfn{circular trace buffer}, then you
10497 can run a trace experiment indefinitely without filling the trace
10498 buffer; when space runs out, the agent deletes already-collected trace
10499 frames, oldest first, until there is enough room to continue
10500 collecting. This is especially useful if your tracepoints are being
10501 hit too often, and your trace gets terminated prematurely because the
10502 buffer is full. To ask for a circular trace buffer, simply set
10503 @samp{circular-trace-buffer} to on. You can set this at any time,
10504 including during tracing; if the agent can do it, it will change
10505 buffer handling on the fly, otherwise it will not take effect until
10509 @item set circular-trace-buffer on
10510 @itemx set circular-trace-buffer off
10511 @kindex set circular-trace-buffer
10512 Choose whether a tracing run should use a linear or circular buffer
10513 for trace data. A linear buffer will not lose any trace data, but may
10514 fill up prematurely, while a circular buffer will discard old trace
10515 data, but it will have always room for the latest tracepoint hits.
10517 @item show circular-trace-buffer
10518 @kindex show circular-trace-buffer
10519 Show the current choice for the trace buffer. Note that this may not
10520 match the agent's current buffer handling, nor is it guaranteed to
10521 match the setting that might have been in effect during a past run,
10522 for instance if you are looking at frames from a trace file.
10526 @node Tracepoint Restrictions
10527 @subsection Tracepoint Restrictions
10529 @cindex tracepoint restrictions
10530 There are a number of restrictions on the use of tracepoints. As
10531 described above, tracepoint data gathering occurs on the target
10532 without interaction from @value{GDBN}. Thus the full capabilities of
10533 the debugger are not available during data gathering, and then at data
10534 examination time, you will be limited by only having what was
10535 collected. The following items describe some common problems, but it
10536 is not exhaustive, and you may run into additional difficulties not
10542 Tracepoint expressions are intended to gather objects (lvalues). Thus
10543 the full flexibility of GDB's expression evaluator is not available.
10544 You cannot call functions, cast objects to aggregate types, access
10545 convenience variables or modify values (except by assignment to trace
10546 state variables). Some language features may implicitly call
10547 functions (for instance Objective-C fields with accessors), and therefore
10548 cannot be collected either.
10551 Collection of local variables, either individually or in bulk with
10552 @code{$locals} or @code{$args}, during @code{while-stepping} may
10553 behave erratically. The stepping action may enter a new scope (for
10554 instance by stepping into a function), or the location of the variable
10555 may change (for instance it is loaded into a register). The
10556 tracepoint data recorded uses the location information for the
10557 variables that is correct for the tracepoint location. When the
10558 tracepoint is created, it is not possible, in general, to determine
10559 where the steps of a @code{while-stepping} sequence will advance the
10560 program---particularly if a conditional branch is stepped.
10563 Collection of an incompletely-initialized or partially-destroyed object
10564 may result in something that @value{GDBN} cannot display, or displays
10565 in a misleading way.
10568 When @value{GDBN} displays a pointer to character it automatically
10569 dereferences the pointer to also display characters of the string
10570 being pointed to. However, collecting the pointer during tracing does
10571 not automatically collect the string. You need to explicitly
10572 dereference the pointer and provide size information if you want to
10573 collect not only the pointer, but the memory pointed to. For example,
10574 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10578 It is not possible to collect a complete stack backtrace at a
10579 tracepoint. Instead, you may collect the registers and a few hundred
10580 bytes from the stack pointer with something like @code{*$esp@@300}
10581 (adjust to use the name of the actual stack pointer register on your
10582 target architecture, and the amount of stack you wish to capture).
10583 Then the @code{backtrace} command will show a partial backtrace when
10584 using a trace frame. The number of stack frames that can be examined
10585 depends on the sizes of the frames in the collected stack. Note that
10586 if you ask for a block so large that it goes past the bottom of the
10587 stack, the target agent may report an error trying to read from an
10591 If you do not collect registers at a tracepoint, @value{GDBN} can
10592 infer that the value of @code{$pc} must be the same as the address of
10593 the tracepoint and use that when you are looking at a trace frame
10594 for that tracepoint. However, this cannot work if the tracepoint has
10595 multiple locations (for instance if it was set in a function that was
10596 inlined), or if it has a @code{while-stepping} loop. In those cases
10597 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10602 @node Analyze Collected Data
10603 @section Using the Collected Data
10605 After the tracepoint experiment ends, you use @value{GDBN} commands
10606 for examining the trace data. The basic idea is that each tracepoint
10607 collects a trace @dfn{snapshot} every time it is hit and another
10608 snapshot every time it single-steps. All these snapshots are
10609 consecutively numbered from zero and go into a buffer, and you can
10610 examine them later. The way you examine them is to @dfn{focus} on a
10611 specific trace snapshot. When the remote stub is focused on a trace
10612 snapshot, it will respond to all @value{GDBN} requests for memory and
10613 registers by reading from the buffer which belongs to that snapshot,
10614 rather than from @emph{real} memory or registers of the program being
10615 debugged. This means that @strong{all} @value{GDBN} commands
10616 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10617 behave as if we were currently debugging the program state as it was
10618 when the tracepoint occurred. Any requests for data that are not in
10619 the buffer will fail.
10622 * tfind:: How to select a trace snapshot
10623 * tdump:: How to display all data for a snapshot
10624 * save tracepoints:: How to save tracepoints for a future run
10628 @subsection @code{tfind @var{n}}
10631 @cindex select trace snapshot
10632 @cindex find trace snapshot
10633 The basic command for selecting a trace snapshot from the buffer is
10634 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10635 counting from zero. If no argument @var{n} is given, the next
10636 snapshot is selected.
10638 Here are the various forms of using the @code{tfind} command.
10642 Find the first snapshot in the buffer. This is a synonym for
10643 @code{tfind 0} (since 0 is the number of the first snapshot).
10646 Stop debugging trace snapshots, resume @emph{live} debugging.
10649 Same as @samp{tfind none}.
10652 No argument means find the next trace snapshot.
10655 Find the previous trace snapshot before the current one. This permits
10656 retracing earlier steps.
10658 @item tfind tracepoint @var{num}
10659 Find the next snapshot associated with tracepoint @var{num}. Search
10660 proceeds forward from the last examined trace snapshot. If no
10661 argument @var{num} is given, it means find the next snapshot collected
10662 for the same tracepoint as the current snapshot.
10664 @item tfind pc @var{addr}
10665 Find the next snapshot associated with the value @var{addr} of the
10666 program counter. Search proceeds forward from the last examined trace
10667 snapshot. If no argument @var{addr} is given, it means find the next
10668 snapshot with the same value of PC as the current snapshot.
10670 @item tfind outside @var{addr1}, @var{addr2}
10671 Find the next snapshot whose PC is outside the given range of
10672 addresses (exclusive).
10674 @item tfind range @var{addr1}, @var{addr2}
10675 Find the next snapshot whose PC is between @var{addr1} and
10676 @var{addr2} (inclusive).
10678 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10679 Find the next snapshot associated with the source line @var{n}. If
10680 the optional argument @var{file} is given, refer to line @var{n} in
10681 that source file. Search proceeds forward from the last examined
10682 trace snapshot. If no argument @var{n} is given, it means find the
10683 next line other than the one currently being examined; thus saying
10684 @code{tfind line} repeatedly can appear to have the same effect as
10685 stepping from line to line in a @emph{live} debugging session.
10688 The default arguments for the @code{tfind} commands are specifically
10689 designed to make it easy to scan through the trace buffer. For
10690 instance, @code{tfind} with no argument selects the next trace
10691 snapshot, and @code{tfind -} with no argument selects the previous
10692 trace snapshot. So, by giving one @code{tfind} command, and then
10693 simply hitting @key{RET} repeatedly you can examine all the trace
10694 snapshots in order. Or, by saying @code{tfind -} and then hitting
10695 @key{RET} repeatedly you can examine the snapshots in reverse order.
10696 The @code{tfind line} command with no argument selects the snapshot
10697 for the next source line executed. The @code{tfind pc} command with
10698 no argument selects the next snapshot with the same program counter
10699 (PC) as the current frame. The @code{tfind tracepoint} command with
10700 no argument selects the next trace snapshot collected by the same
10701 tracepoint as the current one.
10703 In addition to letting you scan through the trace buffer manually,
10704 these commands make it easy to construct @value{GDBN} scripts that
10705 scan through the trace buffer and print out whatever collected data
10706 you are interested in. Thus, if we want to examine the PC, FP, and SP
10707 registers from each trace frame in the buffer, we can say this:
10710 (@value{GDBP}) @b{tfind start}
10711 (@value{GDBP}) @b{while ($trace_frame != -1)}
10712 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10713 $trace_frame, $pc, $sp, $fp
10717 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10718 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10719 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10720 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10721 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10722 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10723 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10724 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10725 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10726 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10727 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10730 Or, if we want to examine the variable @code{X} at each source line in
10734 (@value{GDBP}) @b{tfind start}
10735 (@value{GDBP}) @b{while ($trace_frame != -1)}
10736 > printf "Frame %d, X == %d\n", $trace_frame, X
10746 @subsection @code{tdump}
10748 @cindex dump all data collected at tracepoint
10749 @cindex tracepoint data, display
10751 This command takes no arguments. It prints all the data collected at
10752 the current trace snapshot.
10755 (@value{GDBP}) @b{trace 444}
10756 (@value{GDBP}) @b{actions}
10757 Enter actions for tracepoint #2, one per line:
10758 > collect $regs, $locals, $args, gdb_long_test
10761 (@value{GDBP}) @b{tstart}
10763 (@value{GDBP}) @b{tfind line 444}
10764 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10766 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10768 (@value{GDBP}) @b{tdump}
10769 Data collected at tracepoint 2, trace frame 1:
10770 d0 0xc4aa0085 -995491707
10774 d4 0x71aea3d 119204413
10777 d7 0x380035 3670069
10778 a0 0x19e24a 1696330
10779 a1 0x3000668 50333288
10781 a3 0x322000 3284992
10782 a4 0x3000698 50333336
10783 a5 0x1ad3cc 1758156
10784 fp 0x30bf3c 0x30bf3c
10785 sp 0x30bf34 0x30bf34
10787 pc 0x20b2c8 0x20b2c8
10791 p = 0x20e5b4 "gdb-test"
10798 gdb_long_test = 17 '\021'
10803 @code{tdump} works by scanning the tracepoint's current collection
10804 actions and printing the value of each expression listed. So
10805 @code{tdump} can fail, if after a run, you change the tracepoint's
10806 actions to mention variables that were not collected during the run.
10808 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10809 uses the collected value of @code{$pc} to distinguish between trace
10810 frames that were collected at the tracepoint hit, and frames that were
10811 collected while stepping. This allows it to correctly choose whether
10812 to display the basic list of collections, or the collections from the
10813 body of the while-stepping loop. However, if @code{$pc} was not collected,
10814 then @code{tdump} will always attempt to dump using the basic collection
10815 list, and may fail if a while-stepping frame does not include all the
10816 same data that is collected at the tracepoint hit.
10817 @c This is getting pretty arcane, example would be good.
10819 @node save tracepoints
10820 @subsection @code{save tracepoints @var{filename}}
10821 @kindex save tracepoints
10822 @kindex save-tracepoints
10823 @cindex save tracepoints for future sessions
10825 This command saves all current tracepoint definitions together with
10826 their actions and passcounts, into a file @file{@var{filename}}
10827 suitable for use in a later debugging session. To read the saved
10828 tracepoint definitions, use the @code{source} command (@pxref{Command
10829 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10830 alias for @w{@code{save tracepoints}}
10832 @node Tracepoint Variables
10833 @section Convenience Variables for Tracepoints
10834 @cindex tracepoint variables
10835 @cindex convenience variables for tracepoints
10838 @vindex $trace_frame
10839 @item (int) $trace_frame
10840 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10841 snapshot is selected.
10843 @vindex $tracepoint
10844 @item (int) $tracepoint
10845 The tracepoint for the current trace snapshot.
10847 @vindex $trace_line
10848 @item (int) $trace_line
10849 The line number for the current trace snapshot.
10851 @vindex $trace_file
10852 @item (char []) $trace_file
10853 The source file for the current trace snapshot.
10855 @vindex $trace_func
10856 @item (char []) $trace_func
10857 The name of the function containing @code{$tracepoint}.
10860 Note: @code{$trace_file} is not suitable for use in @code{printf},
10861 use @code{output} instead.
10863 Here's a simple example of using these convenience variables for
10864 stepping through all the trace snapshots and printing some of their
10865 data. Note that these are not the same as trace state variables,
10866 which are managed by the target.
10869 (@value{GDBP}) @b{tfind start}
10871 (@value{GDBP}) @b{while $trace_frame != -1}
10872 > output $trace_file
10873 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10879 @section Using Trace Files
10880 @cindex trace files
10882 In some situations, the target running a trace experiment may no
10883 longer be available; perhaps it crashed, or the hardware was needed
10884 for a different activity. To handle these cases, you can arrange to
10885 dump the trace data into a file, and later use that file as a source
10886 of trace data, via the @code{target tfile} command.
10891 @item tsave [ -r ] @var{filename}
10892 Save the trace data to @var{filename}. By default, this command
10893 assumes that @var{filename} refers to the host filesystem, so if
10894 necessary @value{GDBN} will copy raw trace data up from the target and
10895 then save it. If the target supports it, you can also supply the
10896 optional argument @code{-r} (``remote'') to direct the target to save
10897 the data directly into @var{filename} in its own filesystem, which may be
10898 more efficient if the trace buffer is very large. (Note, however, that
10899 @code{target tfile} can only read from files accessible to the host.)
10901 @kindex target tfile
10903 @item target tfile @var{filename}
10904 Use the file named @var{filename} as a source of trace data. Commands
10905 that examine data work as they do with a live target, but it is not
10906 possible to run any new trace experiments. @code{tstatus} will report
10907 the state of the trace run at the moment the data was saved, as well
10908 as the current trace frame you are examining. @var{filename} must be
10909 on a filesystem accessible to the host.
10914 @chapter Debugging Programs That Use Overlays
10917 If your program is too large to fit completely in your target system's
10918 memory, you can sometimes use @dfn{overlays} to work around this
10919 problem. @value{GDBN} provides some support for debugging programs that
10923 * How Overlays Work:: A general explanation of overlays.
10924 * Overlay Commands:: Managing overlays in @value{GDBN}.
10925 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10926 mapped by asking the inferior.
10927 * Overlay Sample Program:: A sample program using overlays.
10930 @node How Overlays Work
10931 @section How Overlays Work
10932 @cindex mapped overlays
10933 @cindex unmapped overlays
10934 @cindex load address, overlay's
10935 @cindex mapped address
10936 @cindex overlay area
10938 Suppose you have a computer whose instruction address space is only 64
10939 kilobytes long, but which has much more memory which can be accessed by
10940 other means: special instructions, segment registers, or memory
10941 management hardware, for example. Suppose further that you want to
10942 adapt a program which is larger than 64 kilobytes to run on this system.
10944 One solution is to identify modules of your program which are relatively
10945 independent, and need not call each other directly; call these modules
10946 @dfn{overlays}. Separate the overlays from the main program, and place
10947 their machine code in the larger memory. Place your main program in
10948 instruction memory, but leave at least enough space there to hold the
10949 largest overlay as well.
10951 Now, to call a function located in an overlay, you must first copy that
10952 overlay's machine code from the large memory into the space set aside
10953 for it in the instruction memory, and then jump to its entry point
10956 @c NB: In the below the mapped area's size is greater or equal to the
10957 @c size of all overlays. This is intentional to remind the developer
10958 @c that overlays don't necessarily need to be the same size.
10962 Data Instruction Larger
10963 Address Space Address Space Address Space
10964 +-----------+ +-----------+ +-----------+
10966 +-----------+ +-----------+ +-----------+<-- overlay 1
10967 | program | | main | .----| overlay 1 | load address
10968 | variables | | program | | +-----------+
10969 | and heap | | | | | |
10970 +-----------+ | | | +-----------+<-- overlay 2
10971 | | +-----------+ | | | load address
10972 +-----------+ | | | .-| overlay 2 |
10974 mapped --->+-----------+ | | +-----------+
10975 address | | | | | |
10976 | overlay | <-' | | |
10977 | area | <---' +-----------+<-- overlay 3
10978 | | <---. | | load address
10979 +-----------+ `--| overlay 3 |
10986 @anchor{A code overlay}A code overlay
10990 The diagram (@pxref{A code overlay}) shows a system with separate data
10991 and instruction address spaces. To map an overlay, the program copies
10992 its code from the larger address space to the instruction address space.
10993 Since the overlays shown here all use the same mapped address, only one
10994 may be mapped at a time. For a system with a single address space for
10995 data and instructions, the diagram would be similar, except that the
10996 program variables and heap would share an address space with the main
10997 program and the overlay area.
10999 An overlay loaded into instruction memory and ready for use is called a
11000 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11001 instruction memory. An overlay not present (or only partially present)
11002 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11003 is its address in the larger memory. The mapped address is also called
11004 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11005 called the @dfn{load memory address}, or @dfn{LMA}.
11007 Unfortunately, overlays are not a completely transparent way to adapt a
11008 program to limited instruction memory. They introduce a new set of
11009 global constraints you must keep in mind as you design your program:
11014 Before calling or returning to a function in an overlay, your program
11015 must make sure that overlay is actually mapped. Otherwise, the call or
11016 return will transfer control to the right address, but in the wrong
11017 overlay, and your program will probably crash.
11020 If the process of mapping an overlay is expensive on your system, you
11021 will need to choose your overlays carefully to minimize their effect on
11022 your program's performance.
11025 The executable file you load onto your system must contain each
11026 overlay's instructions, appearing at the overlay's load address, not its
11027 mapped address. However, each overlay's instructions must be relocated
11028 and its symbols defined as if the overlay were at its mapped address.
11029 You can use GNU linker scripts to specify different load and relocation
11030 addresses for pieces of your program; see @ref{Overlay Description,,,
11031 ld.info, Using ld: the GNU linker}.
11034 The procedure for loading executable files onto your system must be able
11035 to load their contents into the larger address space as well as the
11036 instruction and data spaces.
11040 The overlay system described above is rather simple, and could be
11041 improved in many ways:
11046 If your system has suitable bank switch registers or memory management
11047 hardware, you could use those facilities to make an overlay's load area
11048 contents simply appear at their mapped address in instruction space.
11049 This would probably be faster than copying the overlay to its mapped
11050 area in the usual way.
11053 If your overlays are small enough, you could set aside more than one
11054 overlay area, and have more than one overlay mapped at a time.
11057 You can use overlays to manage data, as well as instructions. In
11058 general, data overlays are even less transparent to your design than
11059 code overlays: whereas code overlays only require care when you call or
11060 return to functions, data overlays require care every time you access
11061 the data. Also, if you change the contents of a data overlay, you
11062 must copy its contents back out to its load address before you can copy a
11063 different data overlay into the same mapped area.
11068 @node Overlay Commands
11069 @section Overlay Commands
11071 To use @value{GDBN}'s overlay support, each overlay in your program must
11072 correspond to a separate section of the executable file. The section's
11073 virtual memory address and load memory address must be the overlay's
11074 mapped and load addresses. Identifying overlays with sections allows
11075 @value{GDBN} to determine the appropriate address of a function or
11076 variable, depending on whether the overlay is mapped or not.
11078 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11079 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11084 Disable @value{GDBN}'s overlay support. When overlay support is
11085 disabled, @value{GDBN} assumes that all functions and variables are
11086 always present at their mapped addresses. By default, @value{GDBN}'s
11087 overlay support is disabled.
11089 @item overlay manual
11090 @cindex manual overlay debugging
11091 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11092 relies on you to tell it which overlays are mapped, and which are not,
11093 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11094 commands described below.
11096 @item overlay map-overlay @var{overlay}
11097 @itemx overlay map @var{overlay}
11098 @cindex map an overlay
11099 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11100 be the name of the object file section containing the overlay. When an
11101 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11102 functions and variables at their mapped addresses. @value{GDBN} assumes
11103 that any other overlays whose mapped ranges overlap that of
11104 @var{overlay} are now unmapped.
11106 @item overlay unmap-overlay @var{overlay}
11107 @itemx overlay unmap @var{overlay}
11108 @cindex unmap an overlay
11109 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11110 must be the name of the object file section containing the overlay.
11111 When an overlay is unmapped, @value{GDBN} assumes it can find the
11112 overlay's functions and variables at their load addresses.
11115 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11116 consults a data structure the overlay manager maintains in the inferior
11117 to see which overlays are mapped. For details, see @ref{Automatic
11118 Overlay Debugging}.
11120 @item overlay load-target
11121 @itemx overlay load
11122 @cindex reloading the overlay table
11123 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11124 re-reads the table @value{GDBN} automatically each time the inferior
11125 stops, so this command should only be necessary if you have changed the
11126 overlay mapping yourself using @value{GDBN}. This command is only
11127 useful when using automatic overlay debugging.
11129 @item overlay list-overlays
11130 @itemx overlay list
11131 @cindex listing mapped overlays
11132 Display a list of the overlays currently mapped, along with their mapped
11133 addresses, load addresses, and sizes.
11137 Normally, when @value{GDBN} prints a code address, it includes the name
11138 of the function the address falls in:
11141 (@value{GDBP}) print main
11142 $3 = @{int ()@} 0x11a0 <main>
11145 When overlay debugging is enabled, @value{GDBN} recognizes code in
11146 unmapped overlays, and prints the names of unmapped functions with
11147 asterisks around them. For example, if @code{foo} is a function in an
11148 unmapped overlay, @value{GDBN} prints it this way:
11151 (@value{GDBP}) overlay list
11152 No sections are mapped.
11153 (@value{GDBP}) print foo
11154 $5 = @{int (int)@} 0x100000 <*foo*>
11157 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11161 (@value{GDBP}) overlay list
11162 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11163 mapped at 0x1016 - 0x104a
11164 (@value{GDBP}) print foo
11165 $6 = @{int (int)@} 0x1016 <foo>
11168 When overlay debugging is enabled, @value{GDBN} can find the correct
11169 address for functions and variables in an overlay, whether or not the
11170 overlay is mapped. This allows most @value{GDBN} commands, like
11171 @code{break} and @code{disassemble}, to work normally, even on unmapped
11172 code. However, @value{GDBN}'s breakpoint support has some limitations:
11176 @cindex breakpoints in overlays
11177 @cindex overlays, setting breakpoints in
11178 You can set breakpoints in functions in unmapped overlays, as long as
11179 @value{GDBN} can write to the overlay at its load address.
11181 @value{GDBN} can not set hardware or simulator-based breakpoints in
11182 unmapped overlays. However, if you set a breakpoint at the end of your
11183 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11184 you are using manual overlay management), @value{GDBN} will re-set its
11185 breakpoints properly.
11189 @node Automatic Overlay Debugging
11190 @section Automatic Overlay Debugging
11191 @cindex automatic overlay debugging
11193 @value{GDBN} can automatically track which overlays are mapped and which
11194 are not, given some simple co-operation from the overlay manager in the
11195 inferior. If you enable automatic overlay debugging with the
11196 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11197 looks in the inferior's memory for certain variables describing the
11198 current state of the overlays.
11200 Here are the variables your overlay manager must define to support
11201 @value{GDBN}'s automatic overlay debugging:
11205 @item @code{_ovly_table}:
11206 This variable must be an array of the following structures:
11211 /* The overlay's mapped address. */
11214 /* The size of the overlay, in bytes. */
11215 unsigned long size;
11217 /* The overlay's load address. */
11220 /* Non-zero if the overlay is currently mapped;
11222 unsigned long mapped;
11226 @item @code{_novlys}:
11227 This variable must be a four-byte signed integer, holding the total
11228 number of elements in @code{_ovly_table}.
11232 To decide whether a particular overlay is mapped or not, @value{GDBN}
11233 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11234 @code{lma} members equal the VMA and LMA of the overlay's section in the
11235 executable file. When @value{GDBN} finds a matching entry, it consults
11236 the entry's @code{mapped} member to determine whether the overlay is
11239 In addition, your overlay manager may define a function called
11240 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11241 will silently set a breakpoint there. If the overlay manager then
11242 calls this function whenever it has changed the overlay table, this
11243 will enable @value{GDBN} to accurately keep track of which overlays
11244 are in program memory, and update any breakpoints that may be set
11245 in overlays. This will allow breakpoints to work even if the
11246 overlays are kept in ROM or other non-writable memory while they
11247 are not being executed.
11249 @node Overlay Sample Program
11250 @section Overlay Sample Program
11251 @cindex overlay example program
11253 When linking a program which uses overlays, you must place the overlays
11254 at their load addresses, while relocating them to run at their mapped
11255 addresses. To do this, you must write a linker script (@pxref{Overlay
11256 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11257 since linker scripts are specific to a particular host system, target
11258 architecture, and target memory layout, this manual cannot provide
11259 portable sample code demonstrating @value{GDBN}'s overlay support.
11261 However, the @value{GDBN} source distribution does contain an overlaid
11262 program, with linker scripts for a few systems, as part of its test
11263 suite. The program consists of the following files from
11264 @file{gdb/testsuite/gdb.base}:
11268 The main program file.
11270 A simple overlay manager, used by @file{overlays.c}.
11275 Overlay modules, loaded and used by @file{overlays.c}.
11278 Linker scripts for linking the test program on the @code{d10v-elf}
11279 and @code{m32r-elf} targets.
11282 You can build the test program using the @code{d10v-elf} GCC
11283 cross-compiler like this:
11286 $ d10v-elf-gcc -g -c overlays.c
11287 $ d10v-elf-gcc -g -c ovlymgr.c
11288 $ d10v-elf-gcc -g -c foo.c
11289 $ d10v-elf-gcc -g -c bar.c
11290 $ d10v-elf-gcc -g -c baz.c
11291 $ d10v-elf-gcc -g -c grbx.c
11292 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11293 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11296 The build process is identical for any other architecture, except that
11297 you must substitute the appropriate compiler and linker script for the
11298 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11302 @chapter Using @value{GDBN} with Different Languages
11305 Although programming languages generally have common aspects, they are
11306 rarely expressed in the same manner. For instance, in ANSI C,
11307 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11308 Modula-2, it is accomplished by @code{p^}. Values can also be
11309 represented (and displayed) differently. Hex numbers in C appear as
11310 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11312 @cindex working language
11313 Language-specific information is built into @value{GDBN} for some languages,
11314 allowing you to express operations like the above in your program's
11315 native language, and allowing @value{GDBN} to output values in a manner
11316 consistent with the syntax of your program's native language. The
11317 language you use to build expressions is called the @dfn{working
11321 * Setting:: Switching between source languages
11322 * Show:: Displaying the language
11323 * Checks:: Type and range checks
11324 * Supported Languages:: Supported languages
11325 * Unsupported Languages:: Unsupported languages
11329 @section Switching Between Source Languages
11331 There are two ways to control the working language---either have @value{GDBN}
11332 set it automatically, or select it manually yourself. You can use the
11333 @code{set language} command for either purpose. On startup, @value{GDBN}
11334 defaults to setting the language automatically. The working language is
11335 used to determine how expressions you type are interpreted, how values
11338 In addition to the working language, every source file that
11339 @value{GDBN} knows about has its own working language. For some object
11340 file formats, the compiler might indicate which language a particular
11341 source file is in. However, most of the time @value{GDBN} infers the
11342 language from the name of the file. The language of a source file
11343 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11344 show each frame appropriately for its own language. There is no way to
11345 set the language of a source file from within @value{GDBN}, but you can
11346 set the language associated with a filename extension. @xref{Show, ,
11347 Displaying the Language}.
11349 This is most commonly a problem when you use a program, such
11350 as @code{cfront} or @code{f2c}, that generates C but is written in
11351 another language. In that case, make the
11352 program use @code{#line} directives in its C output; that way
11353 @value{GDBN} will know the correct language of the source code of the original
11354 program, and will display that source code, not the generated C code.
11357 * Filenames:: Filename extensions and languages.
11358 * Manually:: Setting the working language manually
11359 * Automatically:: Having @value{GDBN} infer the source language
11363 @subsection List of Filename Extensions and Languages
11365 If a source file name ends in one of the following extensions, then
11366 @value{GDBN} infers that its language is the one indicated.
11384 C@t{++} source file
11390 Objective-C source file
11394 Fortran source file
11397 Modula-2 source file
11401 Assembler source file. This actually behaves almost like C, but
11402 @value{GDBN} does not skip over function prologues when stepping.
11405 In addition, you may set the language associated with a filename
11406 extension. @xref{Show, , Displaying the Language}.
11409 @subsection Setting the Working Language
11411 If you allow @value{GDBN} to set the language automatically,
11412 expressions are interpreted the same way in your debugging session and
11415 @kindex set language
11416 If you wish, you may set the language manually. To do this, issue the
11417 command @samp{set language @var{lang}}, where @var{lang} is the name of
11418 a language, such as
11419 @code{c} or @code{modula-2}.
11420 For a list of the supported languages, type @samp{set language}.
11422 Setting the language manually prevents @value{GDBN} from updating the working
11423 language automatically. This can lead to confusion if you try
11424 to debug a program when the working language is not the same as the
11425 source language, when an expression is acceptable to both
11426 languages---but means different things. For instance, if the current
11427 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11435 might not have the effect you intended. In C, this means to add
11436 @code{b} and @code{c} and place the result in @code{a}. The result
11437 printed would be the value of @code{a}. In Modula-2, this means to compare
11438 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11440 @node Automatically
11441 @subsection Having @value{GDBN} Infer the Source Language
11443 To have @value{GDBN} set the working language automatically, use
11444 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11445 then infers the working language. That is, when your program stops in a
11446 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11447 working language to the language recorded for the function in that
11448 frame. If the language for a frame is unknown (that is, if the function
11449 or block corresponding to the frame was defined in a source file that
11450 does not have a recognized extension), the current working language is
11451 not changed, and @value{GDBN} issues a warning.
11453 This may not seem necessary for most programs, which are written
11454 entirely in one source language. However, program modules and libraries
11455 written in one source language can be used by a main program written in
11456 a different source language. Using @samp{set language auto} in this
11457 case frees you from having to set the working language manually.
11460 @section Displaying the Language
11462 The following commands help you find out which language is the
11463 working language, and also what language source files were written in.
11466 @item show language
11467 @kindex show language
11468 Display the current working language. This is the
11469 language you can use with commands such as @code{print} to
11470 build and compute expressions that may involve variables in your program.
11473 @kindex info frame@r{, show the source language}
11474 Display the source language for this frame. This language becomes the
11475 working language if you use an identifier from this frame.
11476 @xref{Frame Info, ,Information about a Frame}, to identify the other
11477 information listed here.
11480 @kindex info source@r{, show the source language}
11481 Display the source language of this source file.
11482 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11483 information listed here.
11486 In unusual circumstances, you may have source files with extensions
11487 not in the standard list. You can then set the extension associated
11488 with a language explicitly:
11491 @item set extension-language @var{ext} @var{language}
11492 @kindex set extension-language
11493 Tell @value{GDBN} that source files with extension @var{ext} are to be
11494 assumed as written in the source language @var{language}.
11496 @item info extensions
11497 @kindex info extensions
11498 List all the filename extensions and the associated languages.
11502 @section Type and Range Checking
11505 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11506 checking are included, but they do not yet have any effect. This
11507 section documents the intended facilities.
11509 @c FIXME remove warning when type/range code added
11511 Some languages are designed to guard you against making seemingly common
11512 errors through a series of compile- and run-time checks. These include
11513 checking the type of arguments to functions and operators, and making
11514 sure mathematical overflows are caught at run time. Checks such as
11515 these help to ensure a program's correctness once it has been compiled
11516 by eliminating type mismatches, and providing active checks for range
11517 errors when your program is running.
11519 @value{GDBN} can check for conditions like the above if you wish.
11520 Although @value{GDBN} does not check the statements in your program,
11521 it can check expressions entered directly into @value{GDBN} for
11522 evaluation via the @code{print} command, for example. As with the
11523 working language, @value{GDBN} can also decide whether or not to check
11524 automatically based on your program's source language.
11525 @xref{Supported Languages, ,Supported Languages}, for the default
11526 settings of supported languages.
11529 * Type Checking:: An overview of type checking
11530 * Range Checking:: An overview of range checking
11533 @cindex type checking
11534 @cindex checks, type
11535 @node Type Checking
11536 @subsection An Overview of Type Checking
11538 Some languages, such as Modula-2, are strongly typed, meaning that the
11539 arguments to operators and functions have to be of the correct type,
11540 otherwise an error occurs. These checks prevent type mismatch
11541 errors from ever causing any run-time problems. For example,
11549 The second example fails because the @code{CARDINAL} 1 is not
11550 type-compatible with the @code{REAL} 2.3.
11552 For the expressions you use in @value{GDBN} commands, you can tell the
11553 @value{GDBN} type checker to skip checking;
11554 to treat any mismatches as errors and abandon the expression;
11555 or to only issue warnings when type mismatches occur,
11556 but evaluate the expression anyway. When you choose the last of
11557 these, @value{GDBN} evaluates expressions like the second example above, but
11558 also issues a warning.
11560 Even if you turn type checking off, there may be other reasons
11561 related to type that prevent @value{GDBN} from evaluating an expression.
11562 For instance, @value{GDBN} does not know how to add an @code{int} and
11563 a @code{struct foo}. These particular type errors have nothing to do
11564 with the language in use, and usually arise from expressions, such as
11565 the one described above, which make little sense to evaluate anyway.
11567 Each language defines to what degree it is strict about type. For
11568 instance, both Modula-2 and C require the arguments to arithmetical
11569 operators to be numbers. In C, enumerated types and pointers can be
11570 represented as numbers, so that they are valid arguments to mathematical
11571 operators. @xref{Supported Languages, ,Supported Languages}, for further
11572 details on specific languages.
11574 @value{GDBN} provides some additional commands for controlling the type checker:
11576 @kindex set check type
11577 @kindex show check type
11579 @item set check type auto
11580 Set type checking on or off based on the current working language.
11581 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11584 @item set check type on
11585 @itemx set check type off
11586 Set type checking on or off, overriding the default setting for the
11587 current working language. Issue a warning if the setting does not
11588 match the language default. If any type mismatches occur in
11589 evaluating an expression while type checking is on, @value{GDBN} prints a
11590 message and aborts evaluation of the expression.
11592 @item set check type warn
11593 Cause the type checker to issue warnings, but to always attempt to
11594 evaluate the expression. Evaluating the expression may still
11595 be impossible for other reasons. For example, @value{GDBN} cannot add
11596 numbers and structures.
11599 Show the current setting of the type checker, and whether or not @value{GDBN}
11600 is setting it automatically.
11603 @cindex range checking
11604 @cindex checks, range
11605 @node Range Checking
11606 @subsection An Overview of Range Checking
11608 In some languages (such as Modula-2), it is an error to exceed the
11609 bounds of a type; this is enforced with run-time checks. Such range
11610 checking is meant to ensure program correctness by making sure
11611 computations do not overflow, or indices on an array element access do
11612 not exceed the bounds of the array.
11614 For expressions you use in @value{GDBN} commands, you can tell
11615 @value{GDBN} to treat range errors in one of three ways: ignore them,
11616 always treat them as errors and abandon the expression, or issue
11617 warnings but evaluate the expression anyway.
11619 A range error can result from numerical overflow, from exceeding an
11620 array index bound, or when you type a constant that is not a member
11621 of any type. Some languages, however, do not treat overflows as an
11622 error. In many implementations of C, mathematical overflow causes the
11623 result to ``wrap around'' to lower values---for example, if @var{m} is
11624 the largest integer value, and @var{s} is the smallest, then
11627 @var{m} + 1 @result{} @var{s}
11630 This, too, is specific to individual languages, and in some cases
11631 specific to individual compilers or machines. @xref{Supported Languages, ,
11632 Supported Languages}, for further details on specific languages.
11634 @value{GDBN} provides some additional commands for controlling the range checker:
11636 @kindex set check range
11637 @kindex show check range
11639 @item set check range auto
11640 Set range checking on or off based on the current working language.
11641 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11644 @item set check range on
11645 @itemx set check range off
11646 Set range checking on or off, overriding the default setting for the
11647 current working language. A warning is issued if the setting does not
11648 match the language default. If a range error occurs and range checking is on,
11649 then a message is printed and evaluation of the expression is aborted.
11651 @item set check range warn
11652 Output messages when the @value{GDBN} range checker detects a range error,
11653 but attempt to evaluate the expression anyway. Evaluating the
11654 expression may still be impossible for other reasons, such as accessing
11655 memory that the process does not own (a typical example from many Unix
11659 Show the current setting of the range checker, and whether or not it is
11660 being set automatically by @value{GDBN}.
11663 @node Supported Languages
11664 @section Supported Languages
11666 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11667 assembly, Modula-2, and Ada.
11668 @c This is false ...
11669 Some @value{GDBN} features may be used in expressions regardless of the
11670 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11671 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11672 ,Expressions}) can be used with the constructs of any supported
11675 The following sections detail to what degree each source language is
11676 supported by @value{GDBN}. These sections are not meant to be language
11677 tutorials or references, but serve only as a reference guide to what the
11678 @value{GDBN} expression parser accepts, and what input and output
11679 formats should look like for different languages. There are many good
11680 books written on each of these languages; please look to these for a
11681 language reference or tutorial.
11684 * C:: C and C@t{++}
11686 * Objective-C:: Objective-C
11687 * OpenCL C:: OpenCL C
11688 * Fortran:: Fortran
11690 * Modula-2:: Modula-2
11695 @subsection C and C@t{++}
11697 @cindex C and C@t{++}
11698 @cindex expressions in C or C@t{++}
11700 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11701 to both languages. Whenever this is the case, we discuss those languages
11705 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11706 @cindex @sc{gnu} C@t{++}
11707 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11708 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11709 effectively, you must compile your C@t{++} programs with a supported
11710 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11711 compiler (@code{aCC}).
11713 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11714 format; if it doesn't work on your system, try the stabs+ debugging
11715 format. You can select those formats explicitly with the @code{g++}
11716 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11717 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11718 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11721 * C Operators:: C and C@t{++} operators
11722 * C Constants:: C and C@t{++} constants
11723 * C Plus Plus Expressions:: C@t{++} expressions
11724 * C Defaults:: Default settings for C and C@t{++}
11725 * C Checks:: C and C@t{++} type and range checks
11726 * Debugging C:: @value{GDBN} and C
11727 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11728 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11732 @subsubsection C and C@t{++} Operators
11734 @cindex C and C@t{++} operators
11736 Operators must be defined on values of specific types. For instance,
11737 @code{+} is defined on numbers, but not on structures. Operators are
11738 often defined on groups of types.
11740 For the purposes of C and C@t{++}, the following definitions hold:
11745 @emph{Integral types} include @code{int} with any of its storage-class
11746 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11749 @emph{Floating-point types} include @code{float}, @code{double}, and
11750 @code{long double} (if supported by the target platform).
11753 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11756 @emph{Scalar types} include all of the above.
11761 The following operators are supported. They are listed here
11762 in order of increasing precedence:
11766 The comma or sequencing operator. Expressions in a comma-separated list
11767 are evaluated from left to right, with the result of the entire
11768 expression being the last expression evaluated.
11771 Assignment. The value of an assignment expression is the value
11772 assigned. Defined on scalar types.
11775 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11776 and translated to @w{@code{@var{a} = @var{a op b}}}.
11777 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11778 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11779 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11782 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11783 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11787 Logical @sc{or}. Defined on integral types.
11790 Logical @sc{and}. Defined on integral types.
11793 Bitwise @sc{or}. Defined on integral types.
11796 Bitwise exclusive-@sc{or}. Defined on integral types.
11799 Bitwise @sc{and}. Defined on integral types.
11802 Equality and inequality. Defined on scalar types. The value of these
11803 expressions is 0 for false and non-zero for true.
11805 @item <@r{, }>@r{, }<=@r{, }>=
11806 Less than, greater than, less than or equal, greater than or equal.
11807 Defined on scalar types. The value of these expressions is 0 for false
11808 and non-zero for true.
11811 left shift, and right shift. Defined on integral types.
11814 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11817 Addition and subtraction. Defined on integral types, floating-point types and
11820 @item *@r{, }/@r{, }%
11821 Multiplication, division, and modulus. Multiplication and division are
11822 defined on integral and floating-point types. Modulus is defined on
11826 Increment and decrement. When appearing before a variable, the
11827 operation is performed before the variable is used in an expression;
11828 when appearing after it, the variable's value is used before the
11829 operation takes place.
11832 Pointer dereferencing. Defined on pointer types. Same precedence as
11836 Address operator. Defined on variables. Same precedence as @code{++}.
11838 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11839 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11840 to examine the address
11841 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11845 Negative. Defined on integral and floating-point types. Same
11846 precedence as @code{++}.
11849 Logical negation. Defined on integral types. Same precedence as
11853 Bitwise complement operator. Defined on integral types. Same precedence as
11858 Structure member, and pointer-to-structure member. For convenience,
11859 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11860 pointer based on the stored type information.
11861 Defined on @code{struct} and @code{union} data.
11864 Dereferences of pointers to members.
11867 Array indexing. @code{@var{a}[@var{i}]} is defined as
11868 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11871 Function parameter list. Same precedence as @code{->}.
11874 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11875 and @code{class} types.
11878 Doubled colons also represent the @value{GDBN} scope operator
11879 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11883 If an operator is redefined in the user code, @value{GDBN} usually
11884 attempts to invoke the redefined version instead of using the operator's
11885 predefined meaning.
11888 @subsubsection C and C@t{++} Constants
11890 @cindex C and C@t{++} constants
11892 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11897 Integer constants are a sequence of digits. Octal constants are
11898 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11899 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11900 @samp{l}, specifying that the constant should be treated as a
11904 Floating point constants are a sequence of digits, followed by a decimal
11905 point, followed by a sequence of digits, and optionally followed by an
11906 exponent. An exponent is of the form:
11907 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11908 sequence of digits. The @samp{+} is optional for positive exponents.
11909 A floating-point constant may also end with a letter @samp{f} or
11910 @samp{F}, specifying that the constant should be treated as being of
11911 the @code{float} (as opposed to the default @code{double}) type; or with
11912 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11916 Enumerated constants consist of enumerated identifiers, or their
11917 integral equivalents.
11920 Character constants are a single character surrounded by single quotes
11921 (@code{'}), or a number---the ordinal value of the corresponding character
11922 (usually its @sc{ascii} value). Within quotes, the single character may
11923 be represented by a letter or by @dfn{escape sequences}, which are of
11924 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11925 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11926 @samp{@var{x}} is a predefined special character---for example,
11927 @samp{\n} for newline.
11930 String constants are a sequence of character constants surrounded by
11931 double quotes (@code{"}). Any valid character constant (as described
11932 above) may appear. Double quotes within the string must be preceded by
11933 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11937 Pointer constants are an integral value. You can also write pointers
11938 to constants using the C operator @samp{&}.
11941 Array constants are comma-separated lists surrounded by braces @samp{@{}
11942 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11943 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11944 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11947 @node C Plus Plus Expressions
11948 @subsubsection C@t{++} Expressions
11950 @cindex expressions in C@t{++}
11951 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11953 @cindex debugging C@t{++} programs
11954 @cindex C@t{++} compilers
11955 @cindex debug formats and C@t{++}
11956 @cindex @value{NGCC} and C@t{++}
11958 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11959 proper compiler and the proper debug format. Currently, @value{GDBN}
11960 works best when debugging C@t{++} code that is compiled with
11961 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11962 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11963 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11964 stabs+ as their default debug format, so you usually don't need to
11965 specify a debug format explicitly. Other compilers and/or debug formats
11966 are likely to work badly or not at all when using @value{GDBN} to debug
11972 @cindex member functions
11974 Member function calls are allowed; you can use expressions like
11977 count = aml->GetOriginal(x, y)
11980 @vindex this@r{, inside C@t{++} member functions}
11981 @cindex namespace in C@t{++}
11983 While a member function is active (in the selected stack frame), your
11984 expressions have the same namespace available as the member function;
11985 that is, @value{GDBN} allows implicit references to the class instance
11986 pointer @code{this} following the same rules as C@t{++}.
11988 @cindex call overloaded functions
11989 @cindex overloaded functions, calling
11990 @cindex type conversions in C@t{++}
11992 You can call overloaded functions; @value{GDBN} resolves the function
11993 call to the right definition, with some restrictions. @value{GDBN} does not
11994 perform overload resolution involving user-defined type conversions,
11995 calls to constructors, or instantiations of templates that do not exist
11996 in the program. It also cannot handle ellipsis argument lists or
11999 It does perform integral conversions and promotions, floating-point
12000 promotions, arithmetic conversions, pointer conversions, conversions of
12001 class objects to base classes, and standard conversions such as those of
12002 functions or arrays to pointers; it requires an exact match on the
12003 number of function arguments.
12005 Overload resolution is always performed, unless you have specified
12006 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12007 ,@value{GDBN} Features for C@t{++}}.
12009 You must specify @code{set overload-resolution off} in order to use an
12010 explicit function signature to call an overloaded function, as in
12012 p 'foo(char,int)'('x', 13)
12015 The @value{GDBN} command-completion facility can simplify this;
12016 see @ref{Completion, ,Command Completion}.
12018 @cindex reference declarations
12020 @value{GDBN} understands variables declared as C@t{++} references; you can use
12021 them in expressions just as you do in C@t{++} source---they are automatically
12024 In the parameter list shown when @value{GDBN} displays a frame, the values of
12025 reference variables are not displayed (unlike other variables); this
12026 avoids clutter, since references are often used for large structures.
12027 The @emph{address} of a reference variable is always shown, unless
12028 you have specified @samp{set print address off}.
12031 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12032 expressions can use it just as expressions in your program do. Since
12033 one scope may be defined in another, you can use @code{::} repeatedly if
12034 necessary, for example in an expression like
12035 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12036 resolving name scope by reference to source files, in both C and C@t{++}
12037 debugging (@pxref{Variables, ,Program Variables}).
12040 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12041 calling virtual functions correctly, printing out virtual bases of
12042 objects, calling functions in a base subobject, casting objects, and
12043 invoking user-defined operators.
12046 @subsubsection C and C@t{++} Defaults
12048 @cindex C and C@t{++} defaults
12050 If you allow @value{GDBN} to set type and range checking automatically, they
12051 both default to @code{off} whenever the working language changes to
12052 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12053 selects the working language.
12055 If you allow @value{GDBN} to set the language automatically, it
12056 recognizes source files whose names end with @file{.c}, @file{.C}, or
12057 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12058 these files, it sets the working language to C or C@t{++}.
12059 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12060 for further details.
12062 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12063 @c unimplemented. If (b) changes, it might make sense to let this node
12064 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12067 @subsubsection C and C@t{++} Type and Range Checks
12069 @cindex C and C@t{++} checks
12071 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12072 is not used. However, if you turn type checking on, @value{GDBN}
12073 considers two variables type equivalent if:
12077 The two variables are structured and have the same structure, union, or
12081 The two variables have the same type name, or types that have been
12082 declared equivalent through @code{typedef}.
12085 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12088 The two @code{struct}, @code{union}, or @code{enum} variables are
12089 declared in the same declaration. (Note: this may not be true for all C
12094 Range checking, if turned on, is done on mathematical operations. Array
12095 indices are not checked, since they are often used to index a pointer
12096 that is not itself an array.
12099 @subsubsection @value{GDBN} and C
12101 The @code{set print union} and @code{show print union} commands apply to
12102 the @code{union} type. When set to @samp{on}, any @code{union} that is
12103 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12104 appears as @samp{@{...@}}.
12106 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12107 with pointers and a memory allocation function. @xref{Expressions,
12110 @node Debugging C Plus Plus
12111 @subsubsection @value{GDBN} Features for C@t{++}
12113 @cindex commands for C@t{++}
12115 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12116 designed specifically for use with C@t{++}. Here is a summary:
12119 @cindex break in overloaded functions
12120 @item @r{breakpoint menus}
12121 When you want a breakpoint in a function whose name is overloaded,
12122 @value{GDBN} has the capability to display a menu of possible breakpoint
12123 locations to help you specify which function definition you want.
12124 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12126 @cindex overloading in C@t{++}
12127 @item rbreak @var{regex}
12128 Setting breakpoints using regular expressions is helpful for setting
12129 breakpoints on overloaded functions that are not members of any special
12131 @xref{Set Breaks, ,Setting Breakpoints}.
12133 @cindex C@t{++} exception handling
12136 Debug C@t{++} exception handling using these commands. @xref{Set
12137 Catchpoints, , Setting Catchpoints}.
12139 @cindex inheritance
12140 @item ptype @var{typename}
12141 Print inheritance relationships as well as other information for type
12143 @xref{Symbols, ,Examining the Symbol Table}.
12145 @cindex C@t{++} symbol display
12146 @item set print demangle
12147 @itemx show print demangle
12148 @itemx set print asm-demangle
12149 @itemx show print asm-demangle
12150 Control whether C@t{++} symbols display in their source form, both when
12151 displaying code as C@t{++} source and when displaying disassemblies.
12152 @xref{Print Settings, ,Print Settings}.
12154 @item set print object
12155 @itemx show print object
12156 Choose whether to print derived (actual) or declared types of objects.
12157 @xref{Print Settings, ,Print Settings}.
12159 @item set print vtbl
12160 @itemx show print vtbl
12161 Control the format for printing virtual function tables.
12162 @xref{Print Settings, ,Print Settings}.
12163 (The @code{vtbl} commands do not work on programs compiled with the HP
12164 ANSI C@t{++} compiler (@code{aCC}).)
12166 @kindex set overload-resolution
12167 @cindex overloaded functions, overload resolution
12168 @item set overload-resolution on
12169 Enable overload resolution for C@t{++} expression evaluation. The default
12170 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12171 and searches for a function whose signature matches the argument types,
12172 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12173 Expressions, ,C@t{++} Expressions}, for details).
12174 If it cannot find a match, it emits a message.
12176 @item set overload-resolution off
12177 Disable overload resolution for C@t{++} expression evaluation. For
12178 overloaded functions that are not class member functions, @value{GDBN}
12179 chooses the first function of the specified name that it finds in the
12180 symbol table, whether or not its arguments are of the correct type. For
12181 overloaded functions that are class member functions, @value{GDBN}
12182 searches for a function whose signature @emph{exactly} matches the
12185 @kindex show overload-resolution
12186 @item show overload-resolution
12187 Show the current setting of overload resolution.
12189 @item @r{Overloaded symbol names}
12190 You can specify a particular definition of an overloaded symbol, using
12191 the same notation that is used to declare such symbols in C@t{++}: type
12192 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12193 also use the @value{GDBN} command-line word completion facilities to list the
12194 available choices, or to finish the type list for you.
12195 @xref{Completion,, Command Completion}, for details on how to do this.
12198 @node Decimal Floating Point
12199 @subsubsection Decimal Floating Point format
12200 @cindex decimal floating point format
12202 @value{GDBN} can examine, set and perform computations with numbers in
12203 decimal floating point format, which in the C language correspond to the
12204 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12205 specified by the extension to support decimal floating-point arithmetic.
12207 There are two encodings in use, depending on the architecture: BID (Binary
12208 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12209 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12212 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12213 to manipulate decimal floating point numbers, it is not possible to convert
12214 (using a cast, for example) integers wider than 32-bit to decimal float.
12216 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12217 point computations, error checking in decimal float operations ignores
12218 underflow, overflow and divide by zero exceptions.
12220 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12221 to inspect @code{_Decimal128} values stored in floating point registers.
12222 See @ref{PowerPC,,PowerPC} for more details.
12228 @value{GDBN} can be used to debug programs written in D and compiled with
12229 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12230 specific feature --- dynamic arrays.
12233 @subsection Objective-C
12235 @cindex Objective-C
12236 This section provides information about some commands and command
12237 options that are useful for debugging Objective-C code. See also
12238 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12239 few more commands specific to Objective-C support.
12242 * Method Names in Commands::
12243 * The Print Command with Objective-C::
12246 @node Method Names in Commands
12247 @subsubsection Method Names in Commands
12249 The following commands have been extended to accept Objective-C method
12250 names as line specifications:
12252 @kindex clear@r{, and Objective-C}
12253 @kindex break@r{, and Objective-C}
12254 @kindex info line@r{, and Objective-C}
12255 @kindex jump@r{, and Objective-C}
12256 @kindex list@r{, and Objective-C}
12260 @item @code{info line}
12265 A fully qualified Objective-C method name is specified as
12268 -[@var{Class} @var{methodName}]
12271 where the minus sign is used to indicate an instance method and a
12272 plus sign (not shown) is used to indicate a class method. The class
12273 name @var{Class} and method name @var{methodName} are enclosed in
12274 brackets, similar to the way messages are specified in Objective-C
12275 source code. For example, to set a breakpoint at the @code{create}
12276 instance method of class @code{Fruit} in the program currently being
12280 break -[Fruit create]
12283 To list ten program lines around the @code{initialize} class method,
12287 list +[NSText initialize]
12290 In the current version of @value{GDBN}, the plus or minus sign is
12291 required. In future versions of @value{GDBN}, the plus or minus
12292 sign will be optional, but you can use it to narrow the search. It
12293 is also possible to specify just a method name:
12299 You must specify the complete method name, including any colons. If
12300 your program's source files contain more than one @code{create} method,
12301 you'll be presented with a numbered list of classes that implement that
12302 method. Indicate your choice by number, or type @samp{0} to exit if
12305 As another example, to clear a breakpoint established at the
12306 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12309 clear -[NSWindow makeKeyAndOrderFront:]
12312 @node The Print Command with Objective-C
12313 @subsubsection The Print Command With Objective-C
12314 @cindex Objective-C, print objects
12315 @kindex print-object
12316 @kindex po @r{(@code{print-object})}
12318 The print command has also been extended to accept methods. For example:
12321 print -[@var{object} hash]
12324 @cindex print an Objective-C object description
12325 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12327 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12328 and print the result. Also, an additional command has been added,
12329 @code{print-object} or @code{po} for short, which is meant to print
12330 the description of an object. However, this command may only work
12331 with certain Objective-C libraries that have a particular hook
12332 function, @code{_NSPrintForDebugger}, defined.
12335 @subsection OpenCL C
12338 This section provides information about @value{GDBN}s OpenCL C support.
12341 * OpenCL C Datatypes::
12342 * OpenCL C Expressions::
12343 * OpenCL C Operators::
12346 @node OpenCL C Datatypes
12347 @subsubsection OpenCL C Datatypes
12349 @cindex OpenCL C Datatypes
12350 @value{GDBN} supports the builtin scalar and vector datatypes specified
12351 by OpenCL 1.1. In addition the half- and double-precision floating point
12352 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12353 extensions are also known to @value{GDBN}.
12355 @node OpenCL C Expressions
12356 @subsubsection OpenCL C Expressions
12358 @cindex OpenCL C Expressions
12359 @value{GDBN} supports accesses to vector components including the access as
12360 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12361 supported by @value{GDBN} can be used as well.
12363 @node OpenCL C Operators
12364 @subsubsection OpenCL C Operators
12366 @cindex OpenCL C Operators
12367 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12371 @subsection Fortran
12372 @cindex Fortran-specific support in @value{GDBN}
12374 @value{GDBN} can be used to debug programs written in Fortran, but it
12375 currently supports only the features of Fortran 77 language.
12377 @cindex trailing underscore, in Fortran symbols
12378 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12379 among them) append an underscore to the names of variables and
12380 functions. When you debug programs compiled by those compilers, you
12381 will need to refer to variables and functions with a trailing
12385 * Fortran Operators:: Fortran operators and expressions
12386 * Fortran Defaults:: Default settings for Fortran
12387 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12390 @node Fortran Operators
12391 @subsubsection Fortran Operators and Expressions
12393 @cindex Fortran operators and expressions
12395 Operators must be defined on values of specific types. For instance,
12396 @code{+} is defined on numbers, but not on characters or other non-
12397 arithmetic types. Operators are often defined on groups of types.
12401 The exponentiation operator. It raises the first operand to the power
12405 The range operator. Normally used in the form of array(low:high) to
12406 represent a section of array.
12409 The access component operator. Normally used to access elements in derived
12410 types. Also suitable for unions. As unions aren't part of regular Fortran,
12411 this can only happen when accessing a register that uses a gdbarch-defined
12415 @node Fortran Defaults
12416 @subsubsection Fortran Defaults
12418 @cindex Fortran Defaults
12420 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12421 default uses case-insensitive matches for Fortran symbols. You can
12422 change that with the @samp{set case-insensitive} command, see
12423 @ref{Symbols}, for the details.
12425 @node Special Fortran Commands
12426 @subsubsection Special Fortran Commands
12428 @cindex Special Fortran commands
12430 @value{GDBN} has some commands to support Fortran-specific features,
12431 such as displaying common blocks.
12434 @cindex @code{COMMON} blocks, Fortran
12435 @kindex info common
12436 @item info common @r{[}@var{common-name}@r{]}
12437 This command prints the values contained in the Fortran @code{COMMON}
12438 block whose name is @var{common-name}. With no argument, the names of
12439 all @code{COMMON} blocks visible at the current program location are
12446 @cindex Pascal support in @value{GDBN}, limitations
12447 Debugging Pascal programs which use sets, subranges, file variables, or
12448 nested functions does not currently work. @value{GDBN} does not support
12449 entering expressions, printing values, or similar features using Pascal
12452 The Pascal-specific command @code{set print pascal_static-members}
12453 controls whether static members of Pascal objects are displayed.
12454 @xref{Print Settings, pascal_static-members}.
12457 @subsection Modula-2
12459 @cindex Modula-2, @value{GDBN} support
12461 The extensions made to @value{GDBN} to support Modula-2 only support
12462 output from the @sc{gnu} Modula-2 compiler (which is currently being
12463 developed). Other Modula-2 compilers are not currently supported, and
12464 attempting to debug executables produced by them is most likely
12465 to give an error as @value{GDBN} reads in the executable's symbol
12468 @cindex expressions in Modula-2
12470 * M2 Operators:: Built-in operators
12471 * Built-In Func/Proc:: Built-in functions and procedures
12472 * M2 Constants:: Modula-2 constants
12473 * M2 Types:: Modula-2 types
12474 * M2 Defaults:: Default settings for Modula-2
12475 * Deviations:: Deviations from standard Modula-2
12476 * M2 Checks:: Modula-2 type and range checks
12477 * M2 Scope:: The scope operators @code{::} and @code{.}
12478 * GDB/M2:: @value{GDBN} and Modula-2
12482 @subsubsection Operators
12483 @cindex Modula-2 operators
12485 Operators must be defined on values of specific types. For instance,
12486 @code{+} is defined on numbers, but not on structures. Operators are
12487 often defined on groups of types. For the purposes of Modula-2, the
12488 following definitions hold:
12493 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12497 @emph{Character types} consist of @code{CHAR} and its subranges.
12500 @emph{Floating-point types} consist of @code{REAL}.
12503 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12507 @emph{Scalar types} consist of all of the above.
12510 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12513 @emph{Boolean types} consist of @code{BOOLEAN}.
12517 The following operators are supported, and appear in order of
12518 increasing precedence:
12522 Function argument or array index separator.
12525 Assignment. The value of @var{var} @code{:=} @var{value} is
12529 Less than, greater than on integral, floating-point, or enumerated
12533 Less than or equal to, greater than or equal to
12534 on integral, floating-point and enumerated types, or set inclusion on
12535 set types. Same precedence as @code{<}.
12537 @item =@r{, }<>@r{, }#
12538 Equality and two ways of expressing inequality, valid on scalar types.
12539 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12540 available for inequality, since @code{#} conflicts with the script
12544 Set membership. Defined on set types and the types of their members.
12545 Same precedence as @code{<}.
12548 Boolean disjunction. Defined on boolean types.
12551 Boolean conjunction. Defined on boolean types.
12554 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12557 Addition and subtraction on integral and floating-point types, or union
12558 and difference on set types.
12561 Multiplication on integral and floating-point types, or set intersection
12565 Division on floating-point types, or symmetric set difference on set
12566 types. Same precedence as @code{*}.
12569 Integer division and remainder. Defined on integral types. Same
12570 precedence as @code{*}.
12573 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12576 Pointer dereferencing. Defined on pointer types.
12579 Boolean negation. Defined on boolean types. Same precedence as
12583 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12584 precedence as @code{^}.
12587 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12590 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12594 @value{GDBN} and Modula-2 scope operators.
12598 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12599 treats the use of the operator @code{IN}, or the use of operators
12600 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12601 @code{<=}, and @code{>=} on sets as an error.
12605 @node Built-In Func/Proc
12606 @subsubsection Built-in Functions and Procedures
12607 @cindex Modula-2 built-ins
12609 Modula-2 also makes available several built-in procedures and functions.
12610 In describing these, the following metavariables are used:
12615 represents an @code{ARRAY} variable.
12618 represents a @code{CHAR} constant or variable.
12621 represents a variable or constant of integral type.
12624 represents an identifier that belongs to a set. Generally used in the
12625 same function with the metavariable @var{s}. The type of @var{s} should
12626 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12629 represents a variable or constant of integral or floating-point type.
12632 represents a variable or constant of floating-point type.
12638 represents a variable.
12641 represents a variable or constant of one of many types. See the
12642 explanation of the function for details.
12645 All Modula-2 built-in procedures also return a result, described below.
12649 Returns the absolute value of @var{n}.
12652 If @var{c} is a lower case letter, it returns its upper case
12653 equivalent, otherwise it returns its argument.
12656 Returns the character whose ordinal value is @var{i}.
12659 Decrements the value in the variable @var{v} by one. Returns the new value.
12661 @item DEC(@var{v},@var{i})
12662 Decrements the value in the variable @var{v} by @var{i}. Returns the
12665 @item EXCL(@var{m},@var{s})
12666 Removes the element @var{m} from the set @var{s}. Returns the new
12669 @item FLOAT(@var{i})
12670 Returns the floating point equivalent of the integer @var{i}.
12672 @item HIGH(@var{a})
12673 Returns the index of the last member of @var{a}.
12676 Increments the value in the variable @var{v} by one. Returns the new value.
12678 @item INC(@var{v},@var{i})
12679 Increments the value in the variable @var{v} by @var{i}. Returns the
12682 @item INCL(@var{m},@var{s})
12683 Adds the element @var{m} to the set @var{s} if it is not already
12684 there. Returns the new set.
12687 Returns the maximum value of the type @var{t}.
12690 Returns the minimum value of the type @var{t}.
12693 Returns boolean TRUE if @var{i} is an odd number.
12696 Returns the ordinal value of its argument. For example, the ordinal
12697 value of a character is its @sc{ascii} value (on machines supporting the
12698 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12699 integral, character and enumerated types.
12701 @item SIZE(@var{x})
12702 Returns the size of its argument. @var{x} can be a variable or a type.
12704 @item TRUNC(@var{r})
12705 Returns the integral part of @var{r}.
12707 @item TSIZE(@var{x})
12708 Returns the size of its argument. @var{x} can be a variable or a type.
12710 @item VAL(@var{t},@var{i})
12711 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12715 @emph{Warning:} Sets and their operations are not yet supported, so
12716 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12720 @cindex Modula-2 constants
12722 @subsubsection Constants
12724 @value{GDBN} allows you to express the constants of Modula-2 in the following
12730 Integer constants are simply a sequence of digits. When used in an
12731 expression, a constant is interpreted to be type-compatible with the
12732 rest of the expression. Hexadecimal integers are specified by a
12733 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12736 Floating point constants appear as a sequence of digits, followed by a
12737 decimal point and another sequence of digits. An optional exponent can
12738 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12739 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12740 digits of the floating point constant must be valid decimal (base 10)
12744 Character constants consist of a single character enclosed by a pair of
12745 like quotes, either single (@code{'}) or double (@code{"}). They may
12746 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12747 followed by a @samp{C}.
12750 String constants consist of a sequence of characters enclosed by a
12751 pair of like quotes, either single (@code{'}) or double (@code{"}).
12752 Escape sequences in the style of C are also allowed. @xref{C
12753 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12757 Enumerated constants consist of an enumerated identifier.
12760 Boolean constants consist of the identifiers @code{TRUE} and
12764 Pointer constants consist of integral values only.
12767 Set constants are not yet supported.
12771 @subsubsection Modula-2 Types
12772 @cindex Modula-2 types
12774 Currently @value{GDBN} can print the following data types in Modula-2
12775 syntax: array types, record types, set types, pointer types, procedure
12776 types, enumerated types, subrange types and base types. You can also
12777 print the contents of variables declared using these type.
12778 This section gives a number of simple source code examples together with
12779 sample @value{GDBN} sessions.
12781 The first example contains the following section of code:
12790 and you can request @value{GDBN} to interrogate the type and value of
12791 @code{r} and @code{s}.
12794 (@value{GDBP}) print s
12796 (@value{GDBP}) ptype s
12798 (@value{GDBP}) print r
12800 (@value{GDBP}) ptype r
12805 Likewise if your source code declares @code{s} as:
12809 s: SET ['A'..'Z'] ;
12813 then you may query the type of @code{s} by:
12816 (@value{GDBP}) ptype s
12817 type = SET ['A'..'Z']
12821 Note that at present you cannot interactively manipulate set
12822 expressions using the debugger.
12824 The following example shows how you might declare an array in Modula-2
12825 and how you can interact with @value{GDBN} to print its type and contents:
12829 s: ARRAY [-10..10] OF CHAR ;
12833 (@value{GDBP}) ptype s
12834 ARRAY [-10..10] OF CHAR
12837 Note that the array handling is not yet complete and although the type
12838 is printed correctly, expression handling still assumes that all
12839 arrays have a lower bound of zero and not @code{-10} as in the example
12842 Here are some more type related Modula-2 examples:
12846 colour = (blue, red, yellow, green) ;
12847 t = [blue..yellow] ;
12855 The @value{GDBN} interaction shows how you can query the data type
12856 and value of a variable.
12859 (@value{GDBP}) print s
12861 (@value{GDBP}) ptype t
12862 type = [blue..yellow]
12866 In this example a Modula-2 array is declared and its contents
12867 displayed. Observe that the contents are written in the same way as
12868 their @code{C} counterparts.
12872 s: ARRAY [1..5] OF CARDINAL ;
12878 (@value{GDBP}) print s
12879 $1 = @{1, 0, 0, 0, 0@}
12880 (@value{GDBP}) ptype s
12881 type = ARRAY [1..5] OF CARDINAL
12884 The Modula-2 language interface to @value{GDBN} also understands
12885 pointer types as shown in this example:
12889 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12896 and you can request that @value{GDBN} describes the type of @code{s}.
12899 (@value{GDBP}) ptype s
12900 type = POINTER TO ARRAY [1..5] OF CARDINAL
12903 @value{GDBN} handles compound types as we can see in this example.
12904 Here we combine array types, record types, pointer types and subrange
12915 myarray = ARRAY myrange OF CARDINAL ;
12916 myrange = [-2..2] ;
12918 s: POINTER TO ARRAY myrange OF foo ;
12922 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12926 (@value{GDBP}) ptype s
12927 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12930 f3 : ARRAY [-2..2] OF CARDINAL;
12935 @subsubsection Modula-2 Defaults
12936 @cindex Modula-2 defaults
12938 If type and range checking are set automatically by @value{GDBN}, they
12939 both default to @code{on} whenever the working language changes to
12940 Modula-2. This happens regardless of whether you or @value{GDBN}
12941 selected the working language.
12943 If you allow @value{GDBN} to set the language automatically, then entering
12944 code compiled from a file whose name ends with @file{.mod} sets the
12945 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12946 Infer the Source Language}, for further details.
12949 @subsubsection Deviations from Standard Modula-2
12950 @cindex Modula-2, deviations from
12952 A few changes have been made to make Modula-2 programs easier to debug.
12953 This is done primarily via loosening its type strictness:
12957 Unlike in standard Modula-2, pointer constants can be formed by
12958 integers. This allows you to modify pointer variables during
12959 debugging. (In standard Modula-2, the actual address contained in a
12960 pointer variable is hidden from you; it can only be modified
12961 through direct assignment to another pointer variable or expression that
12962 returned a pointer.)
12965 C escape sequences can be used in strings and characters to represent
12966 non-printable characters. @value{GDBN} prints out strings with these
12967 escape sequences embedded. Single non-printable characters are
12968 printed using the @samp{CHR(@var{nnn})} format.
12971 The assignment operator (@code{:=}) returns the value of its right-hand
12975 All built-in procedures both modify @emph{and} return their argument.
12979 @subsubsection Modula-2 Type and Range Checks
12980 @cindex Modula-2 checks
12983 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12986 @c FIXME remove warning when type/range checks added
12988 @value{GDBN} considers two Modula-2 variables type equivalent if:
12992 They are of types that have been declared equivalent via a @code{TYPE
12993 @var{t1} = @var{t2}} statement
12996 They have been declared on the same line. (Note: This is true of the
12997 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13000 As long as type checking is enabled, any attempt to combine variables
13001 whose types are not equivalent is an error.
13003 Range checking is done on all mathematical operations, assignment, array
13004 index bounds, and all built-in functions and procedures.
13007 @subsubsection The Scope Operators @code{::} and @code{.}
13009 @cindex @code{.}, Modula-2 scope operator
13010 @cindex colon, doubled as scope operator
13012 @vindex colon-colon@r{, in Modula-2}
13013 @c Info cannot handle :: but TeX can.
13016 @vindex ::@r{, in Modula-2}
13019 There are a few subtle differences between the Modula-2 scope operator
13020 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13025 @var{module} . @var{id}
13026 @var{scope} :: @var{id}
13030 where @var{scope} is the name of a module or a procedure,
13031 @var{module} the name of a module, and @var{id} is any declared
13032 identifier within your program, except another module.
13034 Using the @code{::} operator makes @value{GDBN} search the scope
13035 specified by @var{scope} for the identifier @var{id}. If it is not
13036 found in the specified scope, then @value{GDBN} searches all scopes
13037 enclosing the one specified by @var{scope}.
13039 Using the @code{.} operator makes @value{GDBN} search the current scope for
13040 the identifier specified by @var{id} that was imported from the
13041 definition module specified by @var{module}. With this operator, it is
13042 an error if the identifier @var{id} was not imported from definition
13043 module @var{module}, or if @var{id} is not an identifier in
13047 @subsubsection @value{GDBN} and Modula-2
13049 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13050 Five subcommands of @code{set print} and @code{show print} apply
13051 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13052 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13053 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13054 analogue in Modula-2.
13056 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13057 with any language, is not useful with Modula-2. Its
13058 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13059 created in Modula-2 as they can in C or C@t{++}. However, because an
13060 address can be specified by an integral constant, the construct
13061 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13063 @cindex @code{#} in Modula-2
13064 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13065 interpreted as the beginning of a comment. Use @code{<>} instead.
13071 The extensions made to @value{GDBN} for Ada only support
13072 output from the @sc{gnu} Ada (GNAT) compiler.
13073 Other Ada compilers are not currently supported, and
13074 attempting to debug executables produced by them is most likely
13078 @cindex expressions in Ada
13080 * Ada Mode Intro:: General remarks on the Ada syntax
13081 and semantics supported by Ada mode
13083 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13084 * Additions to Ada:: Extensions of the Ada expression syntax.
13085 * Stopping Before Main Program:: Debugging the program during elaboration.
13086 * Ada Tasks:: Listing and setting breakpoints in tasks.
13087 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13088 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13090 * Ada Glitches:: Known peculiarities of Ada mode.
13093 @node Ada Mode Intro
13094 @subsubsection Introduction
13095 @cindex Ada mode, general
13097 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13098 syntax, with some extensions.
13099 The philosophy behind the design of this subset is
13103 That @value{GDBN} should provide basic literals and access to operations for
13104 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13105 leaving more sophisticated computations to subprograms written into the
13106 program (which therefore may be called from @value{GDBN}).
13109 That type safety and strict adherence to Ada language restrictions
13110 are not particularly important to the @value{GDBN} user.
13113 That brevity is important to the @value{GDBN} user.
13116 Thus, for brevity, the debugger acts as if all names declared in
13117 user-written packages are directly visible, even if they are not visible
13118 according to Ada rules, thus making it unnecessary to fully qualify most
13119 names with their packages, regardless of context. Where this causes
13120 ambiguity, @value{GDBN} asks the user's intent.
13122 The debugger will start in Ada mode if it detects an Ada main program.
13123 As for other languages, it will enter Ada mode when stopped in a program that
13124 was translated from an Ada source file.
13126 While in Ada mode, you may use `@t{--}' for comments. This is useful
13127 mostly for documenting command files. The standard @value{GDBN} comment
13128 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13129 middle (to allow based literals).
13131 The debugger supports limited overloading. Given a subprogram call in which
13132 the function symbol has multiple definitions, it will use the number of
13133 actual parameters and some information about their types to attempt to narrow
13134 the set of definitions. It also makes very limited use of context, preferring
13135 procedures to functions in the context of the @code{call} command, and
13136 functions to procedures elsewhere.
13138 @node Omissions from Ada
13139 @subsubsection Omissions from Ada
13140 @cindex Ada, omissions from
13142 Here are the notable omissions from the subset:
13146 Only a subset of the attributes are supported:
13150 @t{'First}, @t{'Last}, and @t{'Length}
13151 on array objects (not on types and subtypes).
13154 @t{'Min} and @t{'Max}.
13157 @t{'Pos} and @t{'Val}.
13163 @t{'Range} on array objects (not subtypes), but only as the right
13164 operand of the membership (@code{in}) operator.
13167 @t{'Access}, @t{'Unchecked_Access}, and
13168 @t{'Unrestricted_Access} (a GNAT extension).
13176 @code{Characters.Latin_1} are not available and
13177 concatenation is not implemented. Thus, escape characters in strings are
13178 not currently available.
13181 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13182 equality of representations. They will generally work correctly
13183 for strings and arrays whose elements have integer or enumeration types.
13184 They may not work correctly for arrays whose element
13185 types have user-defined equality, for arrays of real values
13186 (in particular, IEEE-conformant floating point, because of negative
13187 zeroes and NaNs), and for arrays whose elements contain unused bits with
13188 indeterminate values.
13191 The other component-by-component array operations (@code{and}, @code{or},
13192 @code{xor}, @code{not}, and relational tests other than equality)
13193 are not implemented.
13196 @cindex array aggregates (Ada)
13197 @cindex record aggregates (Ada)
13198 @cindex aggregates (Ada)
13199 There is limited support for array and record aggregates. They are
13200 permitted only on the right sides of assignments, as in these examples:
13203 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13204 (@value{GDBP}) set An_Array := (1, others => 0)
13205 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13206 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13207 (@value{GDBP}) set A_Record := (1, "Peter", True);
13208 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13212 discriminant's value by assigning an aggregate has an
13213 undefined effect if that discriminant is used within the record.
13214 However, you can first modify discriminants by directly assigning to
13215 them (which normally would not be allowed in Ada), and then performing an
13216 aggregate assignment. For example, given a variable @code{A_Rec}
13217 declared to have a type such as:
13220 type Rec (Len : Small_Integer := 0) is record
13222 Vals : IntArray (1 .. Len);
13226 you can assign a value with a different size of @code{Vals} with two
13230 (@value{GDBP}) set A_Rec.Len := 4
13231 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13234 As this example also illustrates, @value{GDBN} is very loose about the usual
13235 rules concerning aggregates. You may leave out some of the
13236 components of an array or record aggregate (such as the @code{Len}
13237 component in the assignment to @code{A_Rec} above); they will retain their
13238 original values upon assignment. You may freely use dynamic values as
13239 indices in component associations. You may even use overlapping or
13240 redundant component associations, although which component values are
13241 assigned in such cases is not defined.
13244 Calls to dispatching subprograms are not implemented.
13247 The overloading algorithm is much more limited (i.e., less selective)
13248 than that of real Ada. It makes only limited use of the context in
13249 which a subexpression appears to resolve its meaning, and it is much
13250 looser in its rules for allowing type matches. As a result, some
13251 function calls will be ambiguous, and the user will be asked to choose
13252 the proper resolution.
13255 The @code{new} operator is not implemented.
13258 Entry calls are not implemented.
13261 Aside from printing, arithmetic operations on the native VAX floating-point
13262 formats are not supported.
13265 It is not possible to slice a packed array.
13268 The names @code{True} and @code{False}, when not part of a qualified name,
13269 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13271 Should your program
13272 redefine these names in a package or procedure (at best a dubious practice),
13273 you will have to use fully qualified names to access their new definitions.
13276 @node Additions to Ada
13277 @subsubsection Additions to Ada
13278 @cindex Ada, deviations from
13280 As it does for other languages, @value{GDBN} makes certain generic
13281 extensions to Ada (@pxref{Expressions}):
13285 If the expression @var{E} is a variable residing in memory (typically
13286 a local variable or array element) and @var{N} is a positive integer,
13287 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13288 @var{N}-1 adjacent variables following it in memory as an array. In
13289 Ada, this operator is generally not necessary, since its prime use is
13290 in displaying parts of an array, and slicing will usually do this in
13291 Ada. However, there are occasional uses when debugging programs in
13292 which certain debugging information has been optimized away.
13295 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13296 appears in function or file @var{B}.'' When @var{B} is a file name,
13297 you must typically surround it in single quotes.
13300 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13301 @var{type} that appears at address @var{addr}.''
13304 A name starting with @samp{$} is a convenience variable
13305 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13308 In addition, @value{GDBN} provides a few other shortcuts and outright
13309 additions specific to Ada:
13313 The assignment statement is allowed as an expression, returning
13314 its right-hand operand as its value. Thus, you may enter
13317 (@value{GDBP}) set x := y + 3
13318 (@value{GDBP}) print A(tmp := y + 1)
13322 The semicolon is allowed as an ``operator,'' returning as its value
13323 the value of its right-hand operand.
13324 This allows, for example,
13325 complex conditional breaks:
13328 (@value{GDBP}) break f
13329 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13333 Rather than use catenation and symbolic character names to introduce special
13334 characters into strings, one may instead use a special bracket notation,
13335 which is also used to print strings. A sequence of characters of the form
13336 @samp{["@var{XX}"]} within a string or character literal denotes the
13337 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13338 sequence of characters @samp{["""]} also denotes a single quotation mark
13339 in strings. For example,
13341 "One line.["0a"]Next line.["0a"]"
13344 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13348 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13349 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13353 (@value{GDBP}) print 'max(x, y)
13357 When printing arrays, @value{GDBN} uses positional notation when the
13358 array has a lower bound of 1, and uses a modified named notation otherwise.
13359 For example, a one-dimensional array of three integers with a lower bound
13360 of 3 might print as
13367 That is, in contrast to valid Ada, only the first component has a @code{=>}
13371 You may abbreviate attributes in expressions with any unique,
13372 multi-character subsequence of
13373 their names (an exact match gets preference).
13374 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13375 in place of @t{a'length}.
13378 @cindex quoting Ada internal identifiers
13379 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13380 to lower case. The GNAT compiler uses upper-case characters for
13381 some of its internal identifiers, which are normally of no interest to users.
13382 For the rare occasions when you actually have to look at them,
13383 enclose them in angle brackets to avoid the lower-case mapping.
13386 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13390 Printing an object of class-wide type or dereferencing an
13391 access-to-class-wide value will display all the components of the object's
13392 specific type (as indicated by its run-time tag). Likewise, component
13393 selection on such a value will operate on the specific type of the
13398 @node Stopping Before Main Program
13399 @subsubsection Stopping at the Very Beginning
13401 @cindex breakpointing Ada elaboration code
13402 It is sometimes necessary to debug the program during elaboration, and
13403 before reaching the main procedure.
13404 As defined in the Ada Reference
13405 Manual, the elaboration code is invoked from a procedure called
13406 @code{adainit}. To run your program up to the beginning of
13407 elaboration, simply use the following two commands:
13408 @code{tbreak adainit} and @code{run}.
13411 @subsubsection Extensions for Ada Tasks
13412 @cindex Ada, tasking
13414 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13415 @value{GDBN} provides the following task-related commands:
13420 This command shows a list of current Ada tasks, as in the following example:
13427 (@value{GDBP}) info tasks
13428 ID TID P-ID Pri State Name
13429 1 8088000 0 15 Child Activation Wait main_task
13430 2 80a4000 1 15 Accept Statement b
13431 3 809a800 1 15 Child Activation Wait a
13432 * 4 80ae800 3 15 Runnable c
13437 In this listing, the asterisk before the last task indicates it to be the
13438 task currently being inspected.
13442 Represents @value{GDBN}'s internal task number.
13448 The parent's task ID (@value{GDBN}'s internal task number).
13451 The base priority of the task.
13454 Current state of the task.
13458 The task has been created but has not been activated. It cannot be
13462 The task is not blocked for any reason known to Ada. (It may be waiting
13463 for a mutex, though.) It is conceptually "executing" in normal mode.
13466 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13467 that were waiting on terminate alternatives have been awakened and have
13468 terminated themselves.
13470 @item Child Activation Wait
13471 The task is waiting for created tasks to complete activation.
13473 @item Accept Statement
13474 The task is waiting on an accept or selective wait statement.
13476 @item Waiting on entry call
13477 The task is waiting on an entry call.
13479 @item Async Select Wait
13480 The task is waiting to start the abortable part of an asynchronous
13484 The task is waiting on a select statement with only a delay
13487 @item Child Termination Wait
13488 The task is sleeping having completed a master within itself, and is
13489 waiting for the tasks dependent on that master to become terminated or
13490 waiting on a terminate Phase.
13492 @item Wait Child in Term Alt
13493 The task is sleeping waiting for tasks on terminate alternatives to
13494 finish terminating.
13496 @item Accepting RV with @var{taskno}
13497 The task is accepting a rendez-vous with the task @var{taskno}.
13501 Name of the task in the program.
13505 @kindex info task @var{taskno}
13506 @item info task @var{taskno}
13507 This command shows detailled informations on the specified task, as in
13508 the following example:
13513 (@value{GDBP}) info tasks
13514 ID TID P-ID Pri State Name
13515 1 8077880 0 15 Child Activation Wait main_task
13516 * 2 807c468 1 15 Runnable task_1
13517 (@value{GDBP}) info task 2
13518 Ada Task: 0x807c468
13521 Parent: 1 (main_task)
13527 @kindex task@r{ (Ada)}
13528 @cindex current Ada task ID
13529 This command prints the ID of the current task.
13535 (@value{GDBP}) info tasks
13536 ID TID P-ID Pri State Name
13537 1 8077870 0 15 Child Activation Wait main_task
13538 * 2 807c458 1 15 Runnable t
13539 (@value{GDBP}) task
13540 [Current task is 2]
13543 @item task @var{taskno}
13544 @cindex Ada task switching
13545 This command is like the @code{thread @var{threadno}}
13546 command (@pxref{Threads}). It switches the context of debugging
13547 from the current task to the given task.
13553 (@value{GDBP}) info tasks
13554 ID TID P-ID Pri State Name
13555 1 8077870 0 15 Child Activation Wait main_task
13556 * 2 807c458 1 15 Runnable t
13557 (@value{GDBP}) task 1
13558 [Switching to task 1]
13559 #0 0x8067726 in pthread_cond_wait ()
13561 #0 0x8067726 in pthread_cond_wait ()
13562 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13563 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13564 #3 0x806153e in system.tasking.stages.activate_tasks ()
13565 #4 0x804aacc in un () at un.adb:5
13568 @item break @var{linespec} task @var{taskno}
13569 @itemx break @var{linespec} task @var{taskno} if @dots{}
13570 @cindex breakpoints and tasks, in Ada
13571 @cindex task breakpoints, in Ada
13572 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13573 These commands are like the @code{break @dots{} thread @dots{}}
13574 command (@pxref{Thread Stops}).
13575 @var{linespec} specifies source lines, as described
13576 in @ref{Specify Location}.
13578 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13579 to specify that you only want @value{GDBN} to stop the program when a
13580 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13581 numeric task identifiers assigned by @value{GDBN}, shown in the first
13582 column of the @samp{info tasks} display.
13584 If you do not specify @samp{task @var{taskno}} when you set a
13585 breakpoint, the breakpoint applies to @emph{all} tasks of your
13588 You can use the @code{task} qualifier on conditional breakpoints as
13589 well; in this case, place @samp{task @var{taskno}} before the
13590 breakpoint condition (before the @code{if}).
13598 (@value{GDBP}) info tasks
13599 ID TID P-ID Pri State Name
13600 1 140022020 0 15 Child Activation Wait main_task
13601 2 140045060 1 15 Accept/Select Wait t2
13602 3 140044840 1 15 Runnable t1
13603 * 4 140056040 1 15 Runnable t3
13604 (@value{GDBP}) b 15 task 2
13605 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13606 (@value{GDBP}) cont
13611 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13613 (@value{GDBP}) info tasks
13614 ID TID P-ID Pri State Name
13615 1 140022020 0 15 Child Activation Wait main_task
13616 * 2 140045060 1 15 Runnable t2
13617 3 140044840 1 15 Runnable t1
13618 4 140056040 1 15 Delay Sleep t3
13622 @node Ada Tasks and Core Files
13623 @subsubsection Tasking Support when Debugging Core Files
13624 @cindex Ada tasking and core file debugging
13626 When inspecting a core file, as opposed to debugging a live program,
13627 tasking support may be limited or even unavailable, depending on
13628 the platform being used.
13629 For instance, on x86-linux, the list of tasks is available, but task
13630 switching is not supported. On Tru64, however, task switching will work
13633 On certain platforms, including Tru64, the debugger needs to perform some
13634 memory writes in order to provide Ada tasking support. When inspecting
13635 a core file, this means that the core file must be opened with read-write
13636 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13637 Under these circumstances, you should make a backup copy of the core
13638 file before inspecting it with @value{GDBN}.
13640 @node Ravenscar Profile
13641 @subsubsection Tasking Support when using the Ravenscar Profile
13642 @cindex Ravenscar Profile
13644 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13645 specifically designed for systems with safety-critical real-time
13649 @kindex set ravenscar task-switching on
13650 @cindex task switching with program using Ravenscar Profile
13651 @item set ravenscar task-switching on
13652 Allows task switching when debugging a program that uses the Ravenscar
13653 Profile. This is the default.
13655 @kindex set ravenscar task-switching off
13656 @item set ravenscar task-switching off
13657 Turn off task switching when debugging a program that uses the Ravenscar
13658 Profile. This is mostly intended to disable the code that adds support
13659 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13660 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13661 To be effective, this command should be run before the program is started.
13663 @kindex show ravenscar task-switching
13664 @item show ravenscar task-switching
13665 Show whether it is possible to switch from task to task in a program
13666 using the Ravenscar Profile.
13671 @subsubsection Known Peculiarities of Ada Mode
13672 @cindex Ada, problems
13674 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13675 we know of several problems with and limitations of Ada mode in
13677 some of which will be fixed with planned future releases of the debugger
13678 and the GNU Ada compiler.
13682 Static constants that the compiler chooses not to materialize as objects in
13683 storage are invisible to the debugger.
13686 Named parameter associations in function argument lists are ignored (the
13687 argument lists are treated as positional).
13690 Many useful library packages are currently invisible to the debugger.
13693 Fixed-point arithmetic, conversions, input, and output is carried out using
13694 floating-point arithmetic, and may give results that only approximate those on
13698 The GNAT compiler never generates the prefix @code{Standard} for any of
13699 the standard symbols defined by the Ada language. @value{GDBN} knows about
13700 this: it will strip the prefix from names when you use it, and will never
13701 look for a name you have so qualified among local symbols, nor match against
13702 symbols in other packages or subprograms. If you have
13703 defined entities anywhere in your program other than parameters and
13704 local variables whose simple names match names in @code{Standard},
13705 GNAT's lack of qualification here can cause confusion. When this happens,
13706 you can usually resolve the confusion
13707 by qualifying the problematic names with package
13708 @code{Standard} explicitly.
13711 Older versions of the compiler sometimes generate erroneous debugging
13712 information, resulting in the debugger incorrectly printing the value
13713 of affected entities. In some cases, the debugger is able to work
13714 around an issue automatically. In other cases, the debugger is able
13715 to work around the issue, but the work-around has to be specifically
13718 @kindex set ada trust-PAD-over-XVS
13719 @kindex show ada trust-PAD-over-XVS
13722 @item set ada trust-PAD-over-XVS on
13723 Configure GDB to strictly follow the GNAT encoding when computing the
13724 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13725 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13726 a complete description of the encoding used by the GNAT compiler).
13727 This is the default.
13729 @item set ada trust-PAD-over-XVS off
13730 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13731 sometimes prints the wrong value for certain entities, changing @code{ada
13732 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13733 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13734 @code{off}, but this incurs a slight performance penalty, so it is
13735 recommended to leave this setting to @code{on} unless necessary.
13739 @node Unsupported Languages
13740 @section Unsupported Languages
13742 @cindex unsupported languages
13743 @cindex minimal language
13744 In addition to the other fully-supported programming languages,
13745 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13746 It does not represent a real programming language, but provides a set
13747 of capabilities close to what the C or assembly languages provide.
13748 This should allow most simple operations to be performed while debugging
13749 an application that uses a language currently not supported by @value{GDBN}.
13751 If the language is set to @code{auto}, @value{GDBN} will automatically
13752 select this language if the current frame corresponds to an unsupported
13756 @chapter Examining the Symbol Table
13758 The commands described in this chapter allow you to inquire about the
13759 symbols (names of variables, functions and types) defined in your
13760 program. This information is inherent in the text of your program and
13761 does not change as your program executes. @value{GDBN} finds it in your
13762 program's symbol table, in the file indicated when you started @value{GDBN}
13763 (@pxref{File Options, ,Choosing Files}), or by one of the
13764 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13766 @cindex symbol names
13767 @cindex names of symbols
13768 @cindex quoting names
13769 Occasionally, you may need to refer to symbols that contain unusual
13770 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13771 most frequent case is in referring to static variables in other
13772 source files (@pxref{Variables,,Program Variables}). File names
13773 are recorded in object files as debugging symbols, but @value{GDBN} would
13774 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13775 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13776 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13783 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13786 @cindex case-insensitive symbol names
13787 @cindex case sensitivity in symbol names
13788 @kindex set case-sensitive
13789 @item set case-sensitive on
13790 @itemx set case-sensitive off
13791 @itemx set case-sensitive auto
13792 Normally, when @value{GDBN} looks up symbols, it matches their names
13793 with case sensitivity determined by the current source language.
13794 Occasionally, you may wish to control that. The command @code{set
13795 case-sensitive} lets you do that by specifying @code{on} for
13796 case-sensitive matches or @code{off} for case-insensitive ones. If
13797 you specify @code{auto}, case sensitivity is reset to the default
13798 suitable for the source language. The default is case-sensitive
13799 matches for all languages except for Fortran, for which the default is
13800 case-insensitive matches.
13802 @kindex show case-sensitive
13803 @item show case-sensitive
13804 This command shows the current setting of case sensitivity for symbols
13807 @kindex info address
13808 @cindex address of a symbol
13809 @item info address @var{symbol}
13810 Describe where the data for @var{symbol} is stored. For a register
13811 variable, this says which register it is kept in. For a non-register
13812 local variable, this prints the stack-frame offset at which the variable
13815 Note the contrast with @samp{print &@var{symbol}}, which does not work
13816 at all for a register variable, and for a stack local variable prints
13817 the exact address of the current instantiation of the variable.
13819 @kindex info symbol
13820 @cindex symbol from address
13821 @cindex closest symbol and offset for an address
13822 @item info symbol @var{addr}
13823 Print the name of a symbol which is stored at the address @var{addr}.
13824 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13825 nearest symbol and an offset from it:
13828 (@value{GDBP}) info symbol 0x54320
13829 _initialize_vx + 396 in section .text
13833 This is the opposite of the @code{info address} command. You can use
13834 it to find out the name of a variable or a function given its address.
13836 For dynamically linked executables, the name of executable or shared
13837 library containing the symbol is also printed:
13840 (@value{GDBP}) info symbol 0x400225
13841 _start + 5 in section .text of /tmp/a.out
13842 (@value{GDBP}) info symbol 0x2aaaac2811cf
13843 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13847 @item whatis [@var{arg}]
13848 Print the data type of @var{arg}, which can be either an expression or
13849 a data type. With no argument, print the data type of @code{$}, the
13850 last value in the value history. If @var{arg} is an expression, it is
13851 not actually evaluated, and any side-effecting operations (such as
13852 assignments or function calls) inside it do not take place. If
13853 @var{arg} is a type name, it may be the name of a type or typedef, or
13854 for C code it may have the form @samp{class @var{class-name}},
13855 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13856 @samp{enum @var{enum-tag}}.
13857 @xref{Expressions, ,Expressions}.
13860 @item ptype [@var{arg}]
13861 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13862 detailed description of the type, instead of just the name of the type.
13863 @xref{Expressions, ,Expressions}.
13865 For example, for this variable declaration:
13868 struct complex @{double real; double imag;@} v;
13872 the two commands give this output:
13876 (@value{GDBP}) whatis v
13877 type = struct complex
13878 (@value{GDBP}) ptype v
13879 type = struct complex @{
13887 As with @code{whatis}, using @code{ptype} without an argument refers to
13888 the type of @code{$}, the last value in the value history.
13890 @cindex incomplete type
13891 Sometimes, programs use opaque data types or incomplete specifications
13892 of complex data structure. If the debug information included in the
13893 program does not allow @value{GDBN} to display a full declaration of
13894 the data type, it will say @samp{<incomplete type>}. For example,
13895 given these declarations:
13899 struct foo *fooptr;
13903 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13906 (@value{GDBP}) ptype foo
13907 $1 = <incomplete type>
13911 ``Incomplete type'' is C terminology for data types that are not
13912 completely specified.
13915 @item info types @var{regexp}
13917 Print a brief description of all types whose names match the regular
13918 expression @var{regexp} (or all types in your program, if you supply
13919 no argument). Each complete typename is matched as though it were a
13920 complete line; thus, @samp{i type value} gives information on all
13921 types in your program whose names include the string @code{value}, but
13922 @samp{i type ^value$} gives information only on types whose complete
13923 name is @code{value}.
13925 This command differs from @code{ptype} in two ways: first, like
13926 @code{whatis}, it does not print a detailed description; second, it
13927 lists all source files where a type is defined.
13930 @cindex local variables
13931 @item info scope @var{location}
13932 List all the variables local to a particular scope. This command
13933 accepts a @var{location} argument---a function name, a source line, or
13934 an address preceded by a @samp{*}, and prints all the variables local
13935 to the scope defined by that location. (@xref{Specify Location}, for
13936 details about supported forms of @var{location}.) For example:
13939 (@value{GDBP}) @b{info scope command_line_handler}
13940 Scope for command_line_handler:
13941 Symbol rl is an argument at stack/frame offset 8, length 4.
13942 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13943 Symbol linelength is in static storage at address 0x150a1c, length 4.
13944 Symbol p is a local variable in register $esi, length 4.
13945 Symbol p1 is a local variable in register $ebx, length 4.
13946 Symbol nline is a local variable in register $edx, length 4.
13947 Symbol repeat is a local variable at frame offset -8, length 4.
13951 This command is especially useful for determining what data to collect
13952 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13955 @kindex info source
13957 Show information about the current source file---that is, the source file for
13958 the function containing the current point of execution:
13961 the name of the source file, and the directory containing it,
13963 the directory it was compiled in,
13965 its length, in lines,
13967 which programming language it is written in,
13969 whether the executable includes debugging information for that file, and
13970 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13972 whether the debugging information includes information about
13973 preprocessor macros.
13977 @kindex info sources
13979 Print the names of all source files in your program for which there is
13980 debugging information, organized into two lists: files whose symbols
13981 have already been read, and files whose symbols will be read when needed.
13983 @kindex info functions
13984 @item info functions
13985 Print the names and data types of all defined functions.
13987 @item info functions @var{regexp}
13988 Print the names and data types of all defined functions
13989 whose names contain a match for regular expression @var{regexp}.
13990 Thus, @samp{info fun step} finds all functions whose names
13991 include @code{step}; @samp{info fun ^step} finds those whose names
13992 start with @code{step}. If a function name contains characters
13993 that conflict with the regular expression language (e.g.@:
13994 @samp{operator*()}), they may be quoted with a backslash.
13996 @kindex info variables
13997 @item info variables
13998 Print the names and data types of all variables that are defined
13999 outside of functions (i.e.@: excluding local variables).
14001 @item info variables @var{regexp}
14002 Print the names and data types of all variables (except for local
14003 variables) whose names contain a match for regular expression
14006 @kindex info classes
14007 @cindex Objective-C, classes and selectors
14009 @itemx info classes @var{regexp}
14010 Display all Objective-C classes in your program, or
14011 (with the @var{regexp} argument) all those matching a particular regular
14014 @kindex info selectors
14015 @item info selectors
14016 @itemx info selectors @var{regexp}
14017 Display all Objective-C selectors in your program, or
14018 (with the @var{regexp} argument) all those matching a particular regular
14022 This was never implemented.
14023 @kindex info methods
14025 @itemx info methods @var{regexp}
14026 The @code{info methods} command permits the user to examine all defined
14027 methods within C@t{++} program, or (with the @var{regexp} argument) a
14028 specific set of methods found in the various C@t{++} classes. Many
14029 C@t{++} classes provide a large number of methods. Thus, the output
14030 from the @code{ptype} command can be overwhelming and hard to use. The
14031 @code{info-methods} command filters the methods, printing only those
14032 which match the regular-expression @var{regexp}.
14035 @cindex reloading symbols
14036 Some systems allow individual object files that make up your program to
14037 be replaced without stopping and restarting your program. For example,
14038 in VxWorks you can simply recompile a defective object file and keep on
14039 running. If you are running on one of these systems, you can allow
14040 @value{GDBN} to reload the symbols for automatically relinked modules:
14043 @kindex set symbol-reloading
14044 @item set symbol-reloading on
14045 Replace symbol definitions for the corresponding source file when an
14046 object file with a particular name is seen again.
14048 @item set symbol-reloading off
14049 Do not replace symbol definitions when encountering object files of the
14050 same name more than once. This is the default state; if you are not
14051 running on a system that permits automatic relinking of modules, you
14052 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14053 may discard symbols when linking large programs, that may contain
14054 several modules (from different directories or libraries) with the same
14057 @kindex show symbol-reloading
14058 @item show symbol-reloading
14059 Show the current @code{on} or @code{off} setting.
14062 @cindex opaque data types
14063 @kindex set opaque-type-resolution
14064 @item set opaque-type-resolution on
14065 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14066 declared as a pointer to a @code{struct}, @code{class}, or
14067 @code{union}---for example, @code{struct MyType *}---that is used in one
14068 source file although the full declaration of @code{struct MyType} is in
14069 another source file. The default is on.
14071 A change in the setting of this subcommand will not take effect until
14072 the next time symbols for a file are loaded.
14074 @item set opaque-type-resolution off
14075 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14076 is printed as follows:
14078 @{<no data fields>@}
14081 @kindex show opaque-type-resolution
14082 @item show opaque-type-resolution
14083 Show whether opaque types are resolved or not.
14085 @kindex maint print symbols
14086 @cindex symbol dump
14087 @kindex maint print psymbols
14088 @cindex partial symbol dump
14089 @item maint print symbols @var{filename}
14090 @itemx maint print psymbols @var{filename}
14091 @itemx maint print msymbols @var{filename}
14092 Write a dump of debugging symbol data into the file @var{filename}.
14093 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14094 symbols with debugging data are included. If you use @samp{maint print
14095 symbols}, @value{GDBN} includes all the symbols for which it has already
14096 collected full details: that is, @var{filename} reflects symbols for
14097 only those files whose symbols @value{GDBN} has read. You can use the
14098 command @code{info sources} to find out which files these are. If you
14099 use @samp{maint print psymbols} instead, the dump shows information about
14100 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14101 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14102 @samp{maint print msymbols} dumps just the minimal symbol information
14103 required for each object file from which @value{GDBN} has read some symbols.
14104 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14105 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14107 @kindex maint info symtabs
14108 @kindex maint info psymtabs
14109 @cindex listing @value{GDBN}'s internal symbol tables
14110 @cindex symbol tables, listing @value{GDBN}'s internal
14111 @cindex full symbol tables, listing @value{GDBN}'s internal
14112 @cindex partial symbol tables, listing @value{GDBN}'s internal
14113 @item maint info symtabs @r{[} @var{regexp} @r{]}
14114 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14116 List the @code{struct symtab} or @code{struct partial_symtab}
14117 structures whose names match @var{regexp}. If @var{regexp} is not
14118 given, list them all. The output includes expressions which you can
14119 copy into a @value{GDBN} debugging this one to examine a particular
14120 structure in more detail. For example:
14123 (@value{GDBP}) maint info psymtabs dwarf2read
14124 @{ objfile /home/gnu/build/gdb/gdb
14125 ((struct objfile *) 0x82e69d0)
14126 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14127 ((struct partial_symtab *) 0x8474b10)
14130 text addresses 0x814d3c8 -- 0x8158074
14131 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14132 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14133 dependencies (none)
14136 (@value{GDBP}) maint info symtabs
14140 We see that there is one partial symbol table whose filename contains
14141 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14142 and we see that @value{GDBN} has not read in any symtabs yet at all.
14143 If we set a breakpoint on a function, that will cause @value{GDBN} to
14144 read the symtab for the compilation unit containing that function:
14147 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14148 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14150 (@value{GDBP}) maint info symtabs
14151 @{ objfile /home/gnu/build/gdb/gdb
14152 ((struct objfile *) 0x82e69d0)
14153 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14154 ((struct symtab *) 0x86c1f38)
14157 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14158 linetable ((struct linetable *) 0x8370fa0)
14159 debugformat DWARF 2
14168 @chapter Altering Execution
14170 Once you think you have found an error in your program, you might want to
14171 find out for certain whether correcting the apparent error would lead to
14172 correct results in the rest of the run. You can find the answer by
14173 experiment, using the @value{GDBN} features for altering execution of the
14176 For example, you can store new values into variables or memory
14177 locations, give your program a signal, restart it at a different
14178 address, or even return prematurely from a function.
14181 * Assignment:: Assignment to variables
14182 * Jumping:: Continuing at a different address
14183 * Signaling:: Giving your program a signal
14184 * Returning:: Returning from a function
14185 * Calling:: Calling your program's functions
14186 * Patching:: Patching your program
14190 @section Assignment to Variables
14193 @cindex setting variables
14194 To alter the value of a variable, evaluate an assignment expression.
14195 @xref{Expressions, ,Expressions}. For example,
14202 stores the value 4 into the variable @code{x}, and then prints the
14203 value of the assignment expression (which is 4).
14204 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14205 information on operators in supported languages.
14207 @kindex set variable
14208 @cindex variables, setting
14209 If you are not interested in seeing the value of the assignment, use the
14210 @code{set} command instead of the @code{print} command. @code{set} is
14211 really the same as @code{print} except that the expression's value is
14212 not printed and is not put in the value history (@pxref{Value History,
14213 ,Value History}). The expression is evaluated only for its effects.
14215 If the beginning of the argument string of the @code{set} command
14216 appears identical to a @code{set} subcommand, use the @code{set
14217 variable} command instead of just @code{set}. This command is identical
14218 to @code{set} except for its lack of subcommands. For example, if your
14219 program has a variable @code{width}, you get an error if you try to set
14220 a new value with just @samp{set width=13}, because @value{GDBN} has the
14221 command @code{set width}:
14224 (@value{GDBP}) whatis width
14226 (@value{GDBP}) p width
14228 (@value{GDBP}) set width=47
14229 Invalid syntax in expression.
14233 The invalid expression, of course, is @samp{=47}. In
14234 order to actually set the program's variable @code{width}, use
14237 (@value{GDBP}) set var width=47
14240 Because the @code{set} command has many subcommands that can conflict
14241 with the names of program variables, it is a good idea to use the
14242 @code{set variable} command instead of just @code{set}. For example, if
14243 your program has a variable @code{g}, you run into problems if you try
14244 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14245 the command @code{set gnutarget}, abbreviated @code{set g}:
14249 (@value{GDBP}) whatis g
14253 (@value{GDBP}) set g=4
14257 The program being debugged has been started already.
14258 Start it from the beginning? (y or n) y
14259 Starting program: /home/smith/cc_progs/a.out
14260 "/home/smith/cc_progs/a.out": can't open to read symbols:
14261 Invalid bfd target.
14262 (@value{GDBP}) show g
14263 The current BFD target is "=4".
14268 The program variable @code{g} did not change, and you silently set the
14269 @code{gnutarget} to an invalid value. In order to set the variable
14273 (@value{GDBP}) set var g=4
14276 @value{GDBN} allows more implicit conversions in assignments than C; you can
14277 freely store an integer value into a pointer variable or vice versa,
14278 and you can convert any structure to any other structure that is the
14279 same length or shorter.
14280 @comment FIXME: how do structs align/pad in these conversions?
14281 @comment /doc@cygnus.com 18dec1990
14283 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14284 construct to generate a value of specified type at a specified address
14285 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14286 to memory location @code{0x83040} as an integer (which implies a certain size
14287 and representation in memory), and
14290 set @{int@}0x83040 = 4
14294 stores the value 4 into that memory location.
14297 @section Continuing at a Different Address
14299 Ordinarily, when you continue your program, you do so at the place where
14300 it stopped, with the @code{continue} command. You can instead continue at
14301 an address of your own choosing, with the following commands:
14305 @item jump @var{linespec}
14306 @itemx jump @var{location}
14307 Resume execution at line @var{linespec} or at address given by
14308 @var{location}. Execution stops again immediately if there is a
14309 breakpoint there. @xref{Specify Location}, for a description of the
14310 different forms of @var{linespec} and @var{location}. It is common
14311 practice to use the @code{tbreak} command in conjunction with
14312 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14314 The @code{jump} command does not change the current stack frame, or
14315 the stack pointer, or the contents of any memory location or any
14316 register other than the program counter. If line @var{linespec} is in
14317 a different function from the one currently executing, the results may
14318 be bizarre if the two functions expect different patterns of arguments or
14319 of local variables. For this reason, the @code{jump} command requests
14320 confirmation if the specified line is not in the function currently
14321 executing. However, even bizarre results are predictable if you are
14322 well acquainted with the machine-language code of your program.
14325 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14326 On many systems, you can get much the same effect as the @code{jump}
14327 command by storing a new value into the register @code{$pc}. The
14328 difference is that this does not start your program running; it only
14329 changes the address of where it @emph{will} run when you continue. For
14337 makes the next @code{continue} command or stepping command execute at
14338 address @code{0x485}, rather than at the address where your program stopped.
14339 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14341 The most common occasion to use the @code{jump} command is to back
14342 up---perhaps with more breakpoints set---over a portion of a program
14343 that has already executed, in order to examine its execution in more
14348 @section Giving your Program a Signal
14349 @cindex deliver a signal to a program
14353 @item signal @var{signal}
14354 Resume execution where your program stopped, but immediately give it the
14355 signal @var{signal}. @var{signal} can be the name or the number of a
14356 signal. For example, on many systems @code{signal 2} and @code{signal
14357 SIGINT} are both ways of sending an interrupt signal.
14359 Alternatively, if @var{signal} is zero, continue execution without
14360 giving a signal. This is useful when your program stopped on account of
14361 a signal and would ordinary see the signal when resumed with the
14362 @code{continue} command; @samp{signal 0} causes it to resume without a
14365 @code{signal} does not repeat when you press @key{RET} a second time
14366 after executing the command.
14370 Invoking the @code{signal} command is not the same as invoking the
14371 @code{kill} utility from the shell. Sending a signal with @code{kill}
14372 causes @value{GDBN} to decide what to do with the signal depending on
14373 the signal handling tables (@pxref{Signals}). The @code{signal} command
14374 passes the signal directly to your program.
14378 @section Returning from a Function
14381 @cindex returning from a function
14384 @itemx return @var{expression}
14385 You can cancel execution of a function call with the @code{return}
14386 command. If you give an
14387 @var{expression} argument, its value is used as the function's return
14391 When you use @code{return}, @value{GDBN} discards the selected stack frame
14392 (and all frames within it). You can think of this as making the
14393 discarded frame return prematurely. If you wish to specify a value to
14394 be returned, give that value as the argument to @code{return}.
14396 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14397 Frame}), and any other frames inside of it, leaving its caller as the
14398 innermost remaining frame. That frame becomes selected. The
14399 specified value is stored in the registers used for returning values
14402 The @code{return} command does not resume execution; it leaves the
14403 program stopped in the state that would exist if the function had just
14404 returned. In contrast, the @code{finish} command (@pxref{Continuing
14405 and Stepping, ,Continuing and Stepping}) resumes execution until the
14406 selected stack frame returns naturally.
14408 @value{GDBN} needs to know how the @var{expression} argument should be set for
14409 the inferior. The concrete registers assignment depends on the OS ABI and the
14410 type being returned by the selected stack frame. For example it is common for
14411 OS ABI to return floating point values in FPU registers while integer values in
14412 CPU registers. Still some ABIs return even floating point values in CPU
14413 registers. Larger integer widths (such as @code{long long int}) also have
14414 specific placement rules. @value{GDBN} already knows the OS ABI from its
14415 current target so it needs to find out also the type being returned to make the
14416 assignment into the right register(s).
14418 Normally, the selected stack frame has debug info. @value{GDBN} will always
14419 use the debug info instead of the implicit type of @var{expression} when the
14420 debug info is available. For example, if you type @kbd{return -1}, and the
14421 function in the current stack frame is declared to return a @code{long long
14422 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14423 into a @code{long long int}:
14426 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14428 (@value{GDBP}) return -1
14429 Make func return now? (y or n) y
14430 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14431 43 printf ("result=%lld\n", func ());
14435 However, if the selected stack frame does not have a debug info, e.g., if the
14436 function was compiled without debug info, @value{GDBN} has to find out the type
14437 to return from user. Specifying a different type by mistake may set the value
14438 in different inferior registers than the caller code expects. For example,
14439 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14440 of a @code{long long int} result for a debug info less function (on 32-bit
14441 architectures). Therefore the user is required to specify the return type by
14442 an appropriate cast explicitly:
14445 Breakpoint 2, 0x0040050b in func ()
14446 (@value{GDBP}) return -1
14447 Return value type not available for selected stack frame.
14448 Please use an explicit cast of the value to return.
14449 (@value{GDBP}) return (long long int) -1
14450 Make selected stack frame return now? (y or n) y
14451 #0 0x00400526 in main ()
14456 @section Calling Program Functions
14459 @cindex calling functions
14460 @cindex inferior functions, calling
14461 @item print @var{expr}
14462 Evaluate the expression @var{expr} and display the resulting value.
14463 @var{expr} may include calls to functions in the program being
14467 @item call @var{expr}
14468 Evaluate the expression @var{expr} without displaying @code{void}
14471 You can use this variant of the @code{print} command if you want to
14472 execute a function from your program that does not return anything
14473 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14474 with @code{void} returned values that @value{GDBN} will otherwise
14475 print. If the result is not void, it is printed and saved in the
14479 It is possible for the function you call via the @code{print} or
14480 @code{call} command to generate a signal (e.g., if there's a bug in
14481 the function, or if you passed it incorrect arguments). What happens
14482 in that case is controlled by the @code{set unwindonsignal} command.
14484 Similarly, with a C@t{++} program it is possible for the function you
14485 call via the @code{print} or @code{call} command to generate an
14486 exception that is not handled due to the constraints of the dummy
14487 frame. In this case, any exception that is raised in the frame, but has
14488 an out-of-frame exception handler will not be found. GDB builds a
14489 dummy-frame for the inferior function call, and the unwinder cannot
14490 seek for exception handlers outside of this dummy-frame. What happens
14491 in that case is controlled by the
14492 @code{set unwind-on-terminating-exception} command.
14495 @item set unwindonsignal
14496 @kindex set unwindonsignal
14497 @cindex unwind stack in called functions
14498 @cindex call dummy stack unwinding
14499 Set unwinding of the stack if a signal is received while in a function
14500 that @value{GDBN} called in the program being debugged. If set to on,
14501 @value{GDBN} unwinds the stack it created for the call and restores
14502 the context to what it was before the call. If set to off (the
14503 default), @value{GDBN} stops in the frame where the signal was
14506 @item show unwindonsignal
14507 @kindex show unwindonsignal
14508 Show the current setting of stack unwinding in the functions called by
14511 @item set unwind-on-terminating-exception
14512 @kindex set unwind-on-terminating-exception
14513 @cindex unwind stack in called functions with unhandled exceptions
14514 @cindex call dummy stack unwinding on unhandled exception.
14515 Set unwinding of the stack if a C@t{++} exception is raised, but left
14516 unhandled while in a function that @value{GDBN} called in the program being
14517 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14518 it created for the call and restores the context to what it was before
14519 the call. If set to off, @value{GDBN} the exception is delivered to
14520 the default C@t{++} exception handler and the inferior terminated.
14522 @item show unwind-on-terminating-exception
14523 @kindex show unwind-on-terminating-exception
14524 Show the current setting of stack unwinding in the functions called by
14529 @cindex weak alias functions
14530 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14531 for another function. In such case, @value{GDBN} might not pick up
14532 the type information, including the types of the function arguments,
14533 which causes @value{GDBN} to call the inferior function incorrectly.
14534 As a result, the called function will function erroneously and may
14535 even crash. A solution to that is to use the name of the aliased
14539 @section Patching Programs
14541 @cindex patching binaries
14542 @cindex writing into executables
14543 @cindex writing into corefiles
14545 By default, @value{GDBN} opens the file containing your program's
14546 executable code (or the corefile) read-only. This prevents accidental
14547 alterations to machine code; but it also prevents you from intentionally
14548 patching your program's binary.
14550 If you'd like to be able to patch the binary, you can specify that
14551 explicitly with the @code{set write} command. For example, you might
14552 want to turn on internal debugging flags, or even to make emergency
14558 @itemx set write off
14559 If you specify @samp{set write on}, @value{GDBN} opens executable and
14560 core files for both reading and writing; if you specify @kbd{set write
14561 off} (the default), @value{GDBN} opens them read-only.
14563 If you have already loaded a file, you must load it again (using the
14564 @code{exec-file} or @code{core-file} command) after changing @code{set
14565 write}, for your new setting to take effect.
14569 Display whether executable files and core files are opened for writing
14570 as well as reading.
14574 @chapter @value{GDBN} Files
14576 @value{GDBN} needs to know the file name of the program to be debugged,
14577 both in order to read its symbol table and in order to start your
14578 program. To debug a core dump of a previous run, you must also tell
14579 @value{GDBN} the name of the core dump file.
14582 * Files:: Commands to specify files
14583 * Separate Debug Files:: Debugging information in separate files
14584 * Index Files:: Index files speed up GDB
14585 * Symbol Errors:: Errors reading symbol files
14586 * Data Files:: GDB data files
14590 @section Commands to Specify Files
14592 @cindex symbol table
14593 @cindex core dump file
14595 You may want to specify executable and core dump file names. The usual
14596 way to do this is at start-up time, using the arguments to
14597 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14598 Out of @value{GDBN}}).
14600 Occasionally it is necessary to change to a different file during a
14601 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14602 specify a file you want to use. Or you are debugging a remote target
14603 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14604 Program}). In these situations the @value{GDBN} commands to specify
14605 new files are useful.
14608 @cindex executable file
14610 @item file @var{filename}
14611 Use @var{filename} as the program to be debugged. It is read for its
14612 symbols and for the contents of pure memory. It is also the program
14613 executed when you use the @code{run} command. If you do not specify a
14614 directory and the file is not found in the @value{GDBN} working directory,
14615 @value{GDBN} uses the environment variable @code{PATH} as a list of
14616 directories to search, just as the shell does when looking for a program
14617 to run. You can change the value of this variable, for both @value{GDBN}
14618 and your program, using the @code{path} command.
14620 @cindex unlinked object files
14621 @cindex patching object files
14622 You can load unlinked object @file{.o} files into @value{GDBN} using
14623 the @code{file} command. You will not be able to ``run'' an object
14624 file, but you can disassemble functions and inspect variables. Also,
14625 if the underlying BFD functionality supports it, you could use
14626 @kbd{gdb -write} to patch object files using this technique. Note
14627 that @value{GDBN} can neither interpret nor modify relocations in this
14628 case, so branches and some initialized variables will appear to go to
14629 the wrong place. But this feature is still handy from time to time.
14632 @code{file} with no argument makes @value{GDBN} discard any information it
14633 has on both executable file and the symbol table.
14636 @item exec-file @r{[} @var{filename} @r{]}
14637 Specify that the program to be run (but not the symbol table) is found
14638 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14639 if necessary to locate your program. Omitting @var{filename} means to
14640 discard information on the executable file.
14642 @kindex symbol-file
14643 @item symbol-file @r{[} @var{filename} @r{]}
14644 Read symbol table information from file @var{filename}. @code{PATH} is
14645 searched when necessary. Use the @code{file} command to get both symbol
14646 table and program to run from the same file.
14648 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14649 program's symbol table.
14651 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14652 some breakpoints and auto-display expressions. This is because they may
14653 contain pointers to the internal data recording symbols and data types,
14654 which are part of the old symbol table data being discarded inside
14657 @code{symbol-file} does not repeat if you press @key{RET} again after
14660 When @value{GDBN} is configured for a particular environment, it
14661 understands debugging information in whatever format is the standard
14662 generated for that environment; you may use either a @sc{gnu} compiler, or
14663 other compilers that adhere to the local conventions.
14664 Best results are usually obtained from @sc{gnu} compilers; for example,
14665 using @code{@value{NGCC}} you can generate debugging information for
14668 For most kinds of object files, with the exception of old SVR3 systems
14669 using COFF, the @code{symbol-file} command does not normally read the
14670 symbol table in full right away. Instead, it scans the symbol table
14671 quickly to find which source files and which symbols are present. The
14672 details are read later, one source file at a time, as they are needed.
14674 The purpose of this two-stage reading strategy is to make @value{GDBN}
14675 start up faster. For the most part, it is invisible except for
14676 occasional pauses while the symbol table details for a particular source
14677 file are being read. (The @code{set verbose} command can turn these
14678 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14679 Warnings and Messages}.)
14681 We have not implemented the two-stage strategy for COFF yet. When the
14682 symbol table is stored in COFF format, @code{symbol-file} reads the
14683 symbol table data in full right away. Note that ``stabs-in-COFF''
14684 still does the two-stage strategy, since the debug info is actually
14688 @cindex reading symbols immediately
14689 @cindex symbols, reading immediately
14690 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14691 @itemx file @r{[} -readnow @r{]} @var{filename}
14692 You can override the @value{GDBN} two-stage strategy for reading symbol
14693 tables by using the @samp{-readnow} option with any of the commands that
14694 load symbol table information, if you want to be sure @value{GDBN} has the
14695 entire symbol table available.
14697 @c FIXME: for now no mention of directories, since this seems to be in
14698 @c flux. 13mar1992 status is that in theory GDB would look either in
14699 @c current dir or in same dir as myprog; but issues like competing
14700 @c GDB's, or clutter in system dirs, mean that in practice right now
14701 @c only current dir is used. FFish says maybe a special GDB hierarchy
14702 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14706 @item core-file @r{[}@var{filename}@r{]}
14708 Specify the whereabouts of a core dump file to be used as the ``contents
14709 of memory''. Traditionally, core files contain only some parts of the
14710 address space of the process that generated them; @value{GDBN} can access the
14711 executable file itself for other parts.
14713 @code{core-file} with no argument specifies that no core file is
14716 Note that the core file is ignored when your program is actually running
14717 under @value{GDBN}. So, if you have been running your program and you
14718 wish to debug a core file instead, you must kill the subprocess in which
14719 the program is running. To do this, use the @code{kill} command
14720 (@pxref{Kill Process, ,Killing the Child Process}).
14722 @kindex add-symbol-file
14723 @cindex dynamic linking
14724 @item add-symbol-file @var{filename} @var{address}
14725 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14726 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14727 The @code{add-symbol-file} command reads additional symbol table
14728 information from the file @var{filename}. You would use this command
14729 when @var{filename} has been dynamically loaded (by some other means)
14730 into the program that is running. @var{address} should be the memory
14731 address at which the file has been loaded; @value{GDBN} cannot figure
14732 this out for itself. You can additionally specify an arbitrary number
14733 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14734 section name and base address for that section. You can specify any
14735 @var{address} as an expression.
14737 The symbol table of the file @var{filename} is added to the symbol table
14738 originally read with the @code{symbol-file} command. You can use the
14739 @code{add-symbol-file} command any number of times; the new symbol data
14740 thus read keeps adding to the old. To discard all old symbol data
14741 instead, use the @code{symbol-file} command without any arguments.
14743 @cindex relocatable object files, reading symbols from
14744 @cindex object files, relocatable, reading symbols from
14745 @cindex reading symbols from relocatable object files
14746 @cindex symbols, reading from relocatable object files
14747 @cindex @file{.o} files, reading symbols from
14748 Although @var{filename} is typically a shared library file, an
14749 executable file, or some other object file which has been fully
14750 relocated for loading into a process, you can also load symbolic
14751 information from relocatable @file{.o} files, as long as:
14755 the file's symbolic information refers only to linker symbols defined in
14756 that file, not to symbols defined by other object files,
14758 every section the file's symbolic information refers to has actually
14759 been loaded into the inferior, as it appears in the file, and
14761 you can determine the address at which every section was loaded, and
14762 provide these to the @code{add-symbol-file} command.
14766 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14767 relocatable files into an already running program; such systems
14768 typically make the requirements above easy to meet. However, it's
14769 important to recognize that many native systems use complex link
14770 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14771 assembly, for example) that make the requirements difficult to meet. In
14772 general, one cannot assume that using @code{add-symbol-file} to read a
14773 relocatable object file's symbolic information will have the same effect
14774 as linking the relocatable object file into the program in the normal
14777 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14779 @kindex add-symbol-file-from-memory
14780 @cindex @code{syscall DSO}
14781 @cindex load symbols from memory
14782 @item add-symbol-file-from-memory @var{address}
14783 Load symbols from the given @var{address} in a dynamically loaded
14784 object file whose image is mapped directly into the inferior's memory.
14785 For example, the Linux kernel maps a @code{syscall DSO} into each
14786 process's address space; this DSO provides kernel-specific code for
14787 some system calls. The argument can be any expression whose
14788 evaluation yields the address of the file's shared object file header.
14789 For this command to work, you must have used @code{symbol-file} or
14790 @code{exec-file} commands in advance.
14792 @kindex add-shared-symbol-files
14794 @item add-shared-symbol-files @var{library-file}
14795 @itemx assf @var{library-file}
14796 The @code{add-shared-symbol-files} command can currently be used only
14797 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14798 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14799 @value{GDBN} automatically looks for shared libraries, however if
14800 @value{GDBN} does not find yours, you can invoke
14801 @code{add-shared-symbol-files}. It takes one argument: the shared
14802 library's file name. @code{assf} is a shorthand alias for
14803 @code{add-shared-symbol-files}.
14806 @item section @var{section} @var{addr}
14807 The @code{section} command changes the base address of the named
14808 @var{section} of the exec file to @var{addr}. This can be used if the
14809 exec file does not contain section addresses, (such as in the
14810 @code{a.out} format), or when the addresses specified in the file
14811 itself are wrong. Each section must be changed separately. The
14812 @code{info files} command, described below, lists all the sections and
14816 @kindex info target
14819 @code{info files} and @code{info target} are synonymous; both print the
14820 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14821 including the names of the executable and core dump files currently in
14822 use by @value{GDBN}, and the files from which symbols were loaded. The
14823 command @code{help target} lists all possible targets rather than
14826 @kindex maint info sections
14827 @item maint info sections
14828 Another command that can give you extra information about program sections
14829 is @code{maint info sections}. In addition to the section information
14830 displayed by @code{info files}, this command displays the flags and file
14831 offset of each section in the executable and core dump files. In addition,
14832 @code{maint info sections} provides the following command options (which
14833 may be arbitrarily combined):
14837 Display sections for all loaded object files, including shared libraries.
14838 @item @var{sections}
14839 Display info only for named @var{sections}.
14840 @item @var{section-flags}
14841 Display info only for sections for which @var{section-flags} are true.
14842 The section flags that @value{GDBN} currently knows about are:
14845 Section will have space allocated in the process when loaded.
14846 Set for all sections except those containing debug information.
14848 Section will be loaded from the file into the child process memory.
14849 Set for pre-initialized code and data, clear for @code{.bss} sections.
14851 Section needs to be relocated before loading.
14853 Section cannot be modified by the child process.
14855 Section contains executable code only.
14857 Section contains data only (no executable code).
14859 Section will reside in ROM.
14861 Section contains data for constructor/destructor lists.
14863 Section is not empty.
14865 An instruction to the linker to not output the section.
14866 @item COFF_SHARED_LIBRARY
14867 A notification to the linker that the section contains
14868 COFF shared library information.
14870 Section contains common symbols.
14873 @kindex set trust-readonly-sections
14874 @cindex read-only sections
14875 @item set trust-readonly-sections on
14876 Tell @value{GDBN} that readonly sections in your object file
14877 really are read-only (i.e.@: that their contents will not change).
14878 In that case, @value{GDBN} can fetch values from these sections
14879 out of the object file, rather than from the target program.
14880 For some targets (notably embedded ones), this can be a significant
14881 enhancement to debugging performance.
14883 The default is off.
14885 @item set trust-readonly-sections off
14886 Tell @value{GDBN} not to trust readonly sections. This means that
14887 the contents of the section might change while the program is running,
14888 and must therefore be fetched from the target when needed.
14890 @item show trust-readonly-sections
14891 Show the current setting of trusting readonly sections.
14894 All file-specifying commands allow both absolute and relative file names
14895 as arguments. @value{GDBN} always converts the file name to an absolute file
14896 name and remembers it that way.
14898 @cindex shared libraries
14899 @anchor{Shared Libraries}
14900 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14901 and IBM RS/6000 AIX shared libraries.
14903 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14904 shared libraries. @xref{Expat}.
14906 @value{GDBN} automatically loads symbol definitions from shared libraries
14907 when you use the @code{run} command, or when you examine a core file.
14908 (Before you issue the @code{run} command, @value{GDBN} does not understand
14909 references to a function in a shared library, however---unless you are
14910 debugging a core file).
14912 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14913 automatically loads the symbols at the time of the @code{shl_load} call.
14915 @c FIXME: some @value{GDBN} release may permit some refs to undef
14916 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14917 @c FIXME...lib; check this from time to time when updating manual
14919 There are times, however, when you may wish to not automatically load
14920 symbol definitions from shared libraries, such as when they are
14921 particularly large or there are many of them.
14923 To control the automatic loading of shared library symbols, use the
14927 @kindex set auto-solib-add
14928 @item set auto-solib-add @var{mode}
14929 If @var{mode} is @code{on}, symbols from all shared object libraries
14930 will be loaded automatically when the inferior begins execution, you
14931 attach to an independently started inferior, or when the dynamic linker
14932 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14933 is @code{off}, symbols must be loaded manually, using the
14934 @code{sharedlibrary} command. The default value is @code{on}.
14936 @cindex memory used for symbol tables
14937 If your program uses lots of shared libraries with debug info that
14938 takes large amounts of memory, you can decrease the @value{GDBN}
14939 memory footprint by preventing it from automatically loading the
14940 symbols from shared libraries. To that end, type @kbd{set
14941 auto-solib-add off} before running the inferior, then load each
14942 library whose debug symbols you do need with @kbd{sharedlibrary
14943 @var{regexp}}, where @var{regexp} is a regular expression that matches
14944 the libraries whose symbols you want to be loaded.
14946 @kindex show auto-solib-add
14947 @item show auto-solib-add
14948 Display the current autoloading mode.
14951 @cindex load shared library
14952 To explicitly load shared library symbols, use the @code{sharedlibrary}
14956 @kindex info sharedlibrary
14958 @item info share @var{regex}
14959 @itemx info sharedlibrary @var{regex}
14960 Print the names of the shared libraries which are currently loaded
14961 that match @var{regex}. If @var{regex} is omitted then print
14962 all shared libraries that are loaded.
14964 @kindex sharedlibrary
14966 @item sharedlibrary @var{regex}
14967 @itemx share @var{regex}
14968 Load shared object library symbols for files matching a
14969 Unix regular expression.
14970 As with files loaded automatically, it only loads shared libraries
14971 required by your program for a core file or after typing @code{run}. If
14972 @var{regex} is omitted all shared libraries required by your program are
14975 @item nosharedlibrary
14976 @kindex nosharedlibrary
14977 @cindex unload symbols from shared libraries
14978 Unload all shared object library symbols. This discards all symbols
14979 that have been loaded from all shared libraries. Symbols from shared
14980 libraries that were loaded by explicit user requests are not
14984 Sometimes you may wish that @value{GDBN} stops and gives you control
14985 when any of shared library events happen. Use the @code{set
14986 stop-on-solib-events} command for this:
14989 @item set stop-on-solib-events
14990 @kindex set stop-on-solib-events
14991 This command controls whether @value{GDBN} should give you control
14992 when the dynamic linker notifies it about some shared library event.
14993 The most common event of interest is loading or unloading of a new
14996 @item show stop-on-solib-events
14997 @kindex show stop-on-solib-events
14998 Show whether @value{GDBN} stops and gives you control when shared
14999 library events happen.
15002 Shared libraries are also supported in many cross or remote debugging
15003 configurations. @value{GDBN} needs to have access to the target's libraries;
15004 this can be accomplished either by providing copies of the libraries
15005 on the host system, or by asking @value{GDBN} to automatically retrieve the
15006 libraries from the target. If copies of the target libraries are
15007 provided, they need to be the same as the target libraries, although the
15008 copies on the target can be stripped as long as the copies on the host are
15011 @cindex where to look for shared libraries
15012 For remote debugging, you need to tell @value{GDBN} where the target
15013 libraries are, so that it can load the correct copies---otherwise, it
15014 may try to load the host's libraries. @value{GDBN} has two variables
15015 to specify the search directories for target libraries.
15018 @cindex prefix for shared library file names
15019 @cindex system root, alternate
15020 @kindex set solib-absolute-prefix
15021 @kindex set sysroot
15022 @item set sysroot @var{path}
15023 Use @var{path} as the system root for the program being debugged. Any
15024 absolute shared library paths will be prefixed with @var{path}; many
15025 runtime loaders store the absolute paths to the shared library in the
15026 target program's memory. If you use @code{set sysroot} to find shared
15027 libraries, they need to be laid out in the same way that they are on
15028 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15031 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15032 retrieve the target libraries from the remote system. This is only
15033 supported when using a remote target that supports the @code{remote get}
15034 command (@pxref{File Transfer,,Sending files to a remote system}).
15035 The part of @var{path} following the initial @file{remote:}
15036 (if present) is used as system root prefix on the remote file system.
15037 @footnote{If you want to specify a local system root using a directory
15038 that happens to be named @file{remote:}, you need to use some equivalent
15039 variant of the name like @file{./remote:}.}
15041 For targets with an MS-DOS based filesystem, such as MS-Windows and
15042 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15043 absolute file name with @var{path}. But first, on Unix hosts,
15044 @value{GDBN} converts all backslash directory separators into forward
15045 slashes, because the backslash is not a directory separator on Unix:
15048 c:\foo\bar.dll @result{} c:/foo/bar.dll
15051 Then, @value{GDBN} attempts prefixing the target file name with
15052 @var{path}, and looks for the resulting file name in the host file
15056 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15059 If that does not find the shared library, @value{GDBN} tries removing
15060 the @samp{:} character from the drive spec, both for convenience, and,
15061 for the case of the host file system not supporting file names with
15065 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15068 This makes it possible to have a system root that mirrors a target
15069 with more than one drive. E.g., you may want to setup your local
15070 copies of the target system shared libraries like so (note @samp{c} vs
15074 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15075 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15076 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15080 and point the system root at @file{/path/to/sysroot}, so that
15081 @value{GDBN} can find the correct copies of both
15082 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15084 If that still does not find the shared library, @value{GDBN} tries
15085 removing the whole drive spec from the target file name:
15088 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15091 This last lookup makes it possible to not care about the drive name,
15092 if you don't want or need to.
15094 The @code{set solib-absolute-prefix} command is an alias for @code{set
15097 @cindex default system root
15098 @cindex @samp{--with-sysroot}
15099 You can set the default system root by using the configure-time
15100 @samp{--with-sysroot} option. If the system root is inside
15101 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15102 @samp{--exec-prefix}), then the default system root will be updated
15103 automatically if the installed @value{GDBN} is moved to a new
15106 @kindex show sysroot
15108 Display the current shared library prefix.
15110 @kindex set solib-search-path
15111 @item set solib-search-path @var{path}
15112 If this variable is set, @var{path} is a colon-separated list of
15113 directories to search for shared libraries. @samp{solib-search-path}
15114 is used after @samp{sysroot} fails to locate the library, or if the
15115 path to the library is relative instead of absolute. If you want to
15116 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15117 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15118 finding your host's libraries. @samp{sysroot} is preferred; setting
15119 it to a nonexistent directory may interfere with automatic loading
15120 of shared library symbols.
15122 @kindex show solib-search-path
15123 @item show solib-search-path
15124 Display the current shared library search path.
15126 @cindex DOS file-name semantics of file names.
15127 @kindex set target-file-system-kind (unix|dos-based|auto)
15128 @kindex show target-file-system-kind
15129 @item set target-file-system-kind @var{kind}
15130 Set assumed file system kind for target reported file names.
15132 Shared library file names as reported by the target system may not
15133 make sense as is on the system @value{GDBN} is running on. For
15134 example, when remote debugging a target that has MS-DOS based file
15135 system semantics, from a Unix host, the target may be reporting to
15136 @value{GDBN} a list of loaded shared libraries with file names such as
15137 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15138 drive letters, so the @samp{c:\} prefix is not normally understood as
15139 indicating an absolute file name, and neither is the backslash
15140 normally considered a directory separator character. In that case,
15141 the native file system would interpret this whole absolute file name
15142 as a relative file name with no directory components. This would make
15143 it impossible to point @value{GDBN} at a copy of the remote target's
15144 shared libraries on the host using @code{set sysroot}, and impractical
15145 with @code{set solib-search-path}. Setting
15146 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15147 to interpret such file names similarly to how the target would, and to
15148 map them to file names valid on @value{GDBN}'s native file system
15149 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15150 to one of the supported file system kinds. In that case, @value{GDBN}
15151 tries to determine the appropriate file system variant based on the
15152 current target's operating system (@pxref{ABI, ,Configuring the
15153 Current ABI}). The supported file system settings are:
15157 Instruct @value{GDBN} to assume the target file system is of Unix
15158 kind. Only file names starting the forward slash (@samp{/}) character
15159 are considered absolute, and the directory separator character is also
15163 Instruct @value{GDBN} to assume the target file system is DOS based.
15164 File names starting with either a forward slash, or a drive letter
15165 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15166 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15167 considered directory separators.
15170 Instruct @value{GDBN} to use the file system kind associated with the
15171 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15172 This is the default.
15177 @node Separate Debug Files
15178 @section Debugging Information in Separate Files
15179 @cindex separate debugging information files
15180 @cindex debugging information in separate files
15181 @cindex @file{.debug} subdirectories
15182 @cindex debugging information directory, global
15183 @cindex global debugging information directory
15184 @cindex build ID, and separate debugging files
15185 @cindex @file{.build-id} directory
15187 @value{GDBN} allows you to put a program's debugging information in a
15188 file separate from the executable itself, in a way that allows
15189 @value{GDBN} to find and load the debugging information automatically.
15190 Since debugging information can be very large---sometimes larger
15191 than the executable code itself---some systems distribute debugging
15192 information for their executables in separate files, which users can
15193 install only when they need to debug a problem.
15195 @value{GDBN} supports two ways of specifying the separate debug info
15200 The executable contains a @dfn{debug link} that specifies the name of
15201 the separate debug info file. The separate debug file's name is
15202 usually @file{@var{executable}.debug}, where @var{executable} is the
15203 name of the corresponding executable file without leading directories
15204 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15205 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15206 checksum for the debug file, which @value{GDBN} uses to validate that
15207 the executable and the debug file came from the same build.
15210 The executable contains a @dfn{build ID}, a unique bit string that is
15211 also present in the corresponding debug info file. (This is supported
15212 only on some operating systems, notably those which use the ELF format
15213 for binary files and the @sc{gnu} Binutils.) For more details about
15214 this feature, see the description of the @option{--build-id}
15215 command-line option in @ref{Options, , Command Line Options, ld.info,
15216 The GNU Linker}. The debug info file's name is not specified
15217 explicitly by the build ID, but can be computed from the build ID, see
15221 Depending on the way the debug info file is specified, @value{GDBN}
15222 uses two different methods of looking for the debug file:
15226 For the ``debug link'' method, @value{GDBN} looks up the named file in
15227 the directory of the executable file, then in a subdirectory of that
15228 directory named @file{.debug}, and finally under the global debug
15229 directory, in a subdirectory whose name is identical to the leading
15230 directories of the executable's absolute file name.
15233 For the ``build ID'' method, @value{GDBN} looks in the
15234 @file{.build-id} subdirectory of the global debug directory for a file
15235 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15236 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15237 are the rest of the bit string. (Real build ID strings are 32 or more
15238 hex characters, not 10.)
15241 So, for example, suppose you ask @value{GDBN} to debug
15242 @file{/usr/bin/ls}, which has a debug link that specifies the
15243 file @file{ls.debug}, and a build ID whose value in hex is
15244 @code{abcdef1234}. If the global debug directory is
15245 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15246 debug information files, in the indicated order:
15250 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15252 @file{/usr/bin/ls.debug}
15254 @file{/usr/bin/.debug/ls.debug}
15256 @file{/usr/lib/debug/usr/bin/ls.debug}.
15259 You can set the global debugging info directory's name, and view the
15260 name @value{GDBN} is currently using.
15264 @kindex set debug-file-directory
15265 @item set debug-file-directory @var{directories}
15266 Set the directories which @value{GDBN} searches for separate debugging
15267 information files to @var{directory}. Multiple directory components can be set
15268 concatenating them by a directory separator.
15270 @kindex show debug-file-directory
15271 @item show debug-file-directory
15272 Show the directories @value{GDBN} searches for separate debugging
15277 @cindex @code{.gnu_debuglink} sections
15278 @cindex debug link sections
15279 A debug link is a special section of the executable file named
15280 @code{.gnu_debuglink}. The section must contain:
15284 A filename, with any leading directory components removed, followed by
15287 zero to three bytes of padding, as needed to reach the next four-byte
15288 boundary within the section, and
15290 a four-byte CRC checksum, stored in the same endianness used for the
15291 executable file itself. The checksum is computed on the debugging
15292 information file's full contents by the function given below, passing
15293 zero as the @var{crc} argument.
15296 Any executable file format can carry a debug link, as long as it can
15297 contain a section named @code{.gnu_debuglink} with the contents
15300 @cindex @code{.note.gnu.build-id} sections
15301 @cindex build ID sections
15302 The build ID is a special section in the executable file (and in other
15303 ELF binary files that @value{GDBN} may consider). This section is
15304 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15305 It contains unique identification for the built files---the ID remains
15306 the same across multiple builds of the same build tree. The default
15307 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15308 content for the build ID string. The same section with an identical
15309 value is present in the original built binary with symbols, in its
15310 stripped variant, and in the separate debugging information file.
15312 The debugging information file itself should be an ordinary
15313 executable, containing a full set of linker symbols, sections, and
15314 debugging information. The sections of the debugging information file
15315 should have the same names, addresses, and sizes as the original file,
15316 but they need not contain any data---much like a @code{.bss} section
15317 in an ordinary executable.
15319 The @sc{gnu} binary utilities (Binutils) package includes the
15320 @samp{objcopy} utility that can produce
15321 the separated executable / debugging information file pairs using the
15322 following commands:
15325 @kbd{objcopy --only-keep-debug foo foo.debug}
15330 These commands remove the debugging
15331 information from the executable file @file{foo} and place it in the file
15332 @file{foo.debug}. You can use the first, second or both methods to link the
15337 The debug link method needs the following additional command to also leave
15338 behind a debug link in @file{foo}:
15341 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15344 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15345 a version of the @code{strip} command such that the command @kbd{strip foo -f
15346 foo.debug} has the same functionality as the two @code{objcopy} commands and
15347 the @code{ln -s} command above, together.
15350 Build ID gets embedded into the main executable using @code{ld --build-id} or
15351 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15352 compatibility fixes for debug files separation are present in @sc{gnu} binary
15353 utilities (Binutils) package since version 2.18.
15358 @cindex CRC algorithm definition
15359 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15360 IEEE 802.3 using the polynomial:
15362 @c TexInfo requires naked braces for multi-digit exponents for Tex
15363 @c output, but this causes HTML output to barf. HTML has to be set using
15364 @c raw commands. So we end up having to specify this equation in 2
15369 <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>
15370 + <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
15376 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15377 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15381 The function is computed byte at a time, taking the least
15382 significant bit of each byte first. The initial pattern
15383 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15384 the final result is inverted to ensure trailing zeros also affect the
15387 @emph{Note:} This is the same CRC polynomial as used in handling the
15388 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15389 , @value{GDBN} Remote Serial Protocol}). However in the
15390 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15391 significant bit first, and the result is not inverted, so trailing
15392 zeros have no effect on the CRC value.
15394 To complete the description, we show below the code of the function
15395 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15396 initially supplied @code{crc} argument means that an initial call to
15397 this function passing in zero will start computing the CRC using
15400 @kindex gnu_debuglink_crc32
15403 gnu_debuglink_crc32 (unsigned long crc,
15404 unsigned char *buf, size_t len)
15406 static const unsigned long crc32_table[256] =
15408 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15409 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15410 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15411 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15412 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15413 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15414 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15415 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15416 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15417 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15418 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15419 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15420 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15421 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15422 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15423 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15424 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15425 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15426 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15427 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15428 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15429 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15430 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15431 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15432 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15433 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15434 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15435 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15436 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15437 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15438 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15439 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15440 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15441 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15442 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15443 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15444 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15445 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15446 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15447 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15448 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15449 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15450 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15451 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15452 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15453 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15454 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15455 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15456 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15457 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15458 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15461 unsigned char *end;
15463 crc = ~crc & 0xffffffff;
15464 for (end = buf + len; buf < end; ++buf)
15465 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15466 return ~crc & 0xffffffff;
15471 This computation does not apply to the ``build ID'' method.
15475 @section Index Files Speed Up @value{GDBN}
15476 @cindex index files
15477 @cindex @samp{.gdb_index} section
15479 When @value{GDBN} finds a symbol file, it scans the symbols in the
15480 file in order to construct an internal symbol table. This lets most
15481 @value{GDBN} operations work quickly---at the cost of a delay early
15482 on. For large programs, this delay can be quite lengthy, so
15483 @value{GDBN} provides a way to build an index, which speeds up
15486 The index is stored as a section in the symbol file. @value{GDBN} can
15487 write the index to a file, then you can put it into the symbol file
15488 using @command{objcopy}.
15490 To create an index file, use the @code{save gdb-index} command:
15493 @item save gdb-index @var{directory}
15494 @kindex save gdb-index
15495 Create an index file for each symbol file currently known by
15496 @value{GDBN}. Each file is named after its corresponding symbol file,
15497 with @samp{.gdb-index} appended, and is written into the given
15501 Once you have created an index file you can merge it into your symbol
15502 file, here named @file{symfile}, using @command{objcopy}:
15505 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15506 --set-section-flags .gdb_index=readonly symfile symfile
15509 There are currently some limitation on indices. They only work when
15510 for DWARF debugging information, not stabs. And, they do not
15511 currently work for programs using Ada.
15513 @node Symbol Errors
15514 @section Errors Reading Symbol Files
15516 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15517 such as symbol types it does not recognize, or known bugs in compiler
15518 output. By default, @value{GDBN} does not notify you of such problems, since
15519 they are relatively common and primarily of interest to people
15520 debugging compilers. If you are interested in seeing information
15521 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15522 only one message about each such type of problem, no matter how many
15523 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15524 to see how many times the problems occur, with the @code{set
15525 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15528 The messages currently printed, and their meanings, include:
15531 @item inner block not inside outer block in @var{symbol}
15533 The symbol information shows where symbol scopes begin and end
15534 (such as at the start of a function or a block of statements). This
15535 error indicates that an inner scope block is not fully contained
15536 in its outer scope blocks.
15538 @value{GDBN} circumvents the problem by treating the inner block as if it had
15539 the same scope as the outer block. In the error message, @var{symbol}
15540 may be shown as ``@code{(don't know)}'' if the outer block is not a
15543 @item block at @var{address} out of order
15545 The symbol information for symbol scope blocks should occur in
15546 order of increasing addresses. This error indicates that it does not
15549 @value{GDBN} does not circumvent this problem, and has trouble
15550 locating symbols in the source file whose symbols it is reading. (You
15551 can often determine what source file is affected by specifying
15552 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15555 @item bad block start address patched
15557 The symbol information for a symbol scope block has a start address
15558 smaller than the address of the preceding source line. This is known
15559 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15561 @value{GDBN} circumvents the problem by treating the symbol scope block as
15562 starting on the previous source line.
15564 @item bad string table offset in symbol @var{n}
15567 Symbol number @var{n} contains a pointer into the string table which is
15568 larger than the size of the string table.
15570 @value{GDBN} circumvents the problem by considering the symbol to have the
15571 name @code{foo}, which may cause other problems if many symbols end up
15574 @item unknown symbol type @code{0x@var{nn}}
15576 The symbol information contains new data types that @value{GDBN} does
15577 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15578 uncomprehended information, in hexadecimal.
15580 @value{GDBN} circumvents the error by ignoring this symbol information.
15581 This usually allows you to debug your program, though certain symbols
15582 are not accessible. If you encounter such a problem and feel like
15583 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15584 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15585 and examine @code{*bufp} to see the symbol.
15587 @item stub type has NULL name
15589 @value{GDBN} could not find the full definition for a struct or class.
15591 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15592 The symbol information for a C@t{++} member function is missing some
15593 information that recent versions of the compiler should have output for
15596 @item info mismatch between compiler and debugger
15598 @value{GDBN} could not parse a type specification output by the compiler.
15603 @section GDB Data Files
15605 @cindex prefix for data files
15606 @value{GDBN} will sometimes read an auxiliary data file. These files
15607 are kept in a directory known as the @dfn{data directory}.
15609 You can set the data directory's name, and view the name @value{GDBN}
15610 is currently using.
15613 @kindex set data-directory
15614 @item set data-directory @var{directory}
15615 Set the directory which @value{GDBN} searches for auxiliary data files
15616 to @var{directory}.
15618 @kindex show data-directory
15619 @item show data-directory
15620 Show the directory @value{GDBN} searches for auxiliary data files.
15623 @cindex default data directory
15624 @cindex @samp{--with-gdb-datadir}
15625 You can set the default data directory by using the configure-time
15626 @samp{--with-gdb-datadir} option. If the data directory is inside
15627 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15628 @samp{--exec-prefix}), then the default data directory will be updated
15629 automatically if the installed @value{GDBN} is moved to a new
15632 The data directory may also be specified with the
15633 @code{--data-directory} command line option.
15634 @xref{Mode Options}.
15637 @chapter Specifying a Debugging Target
15639 @cindex debugging target
15640 A @dfn{target} is the execution environment occupied by your program.
15642 Often, @value{GDBN} runs in the same host environment as your program;
15643 in that case, the debugging target is specified as a side effect when
15644 you use the @code{file} or @code{core} commands. When you need more
15645 flexibility---for example, running @value{GDBN} on a physically separate
15646 host, or controlling a standalone system over a serial port or a
15647 realtime system over a TCP/IP connection---you can use the @code{target}
15648 command to specify one of the target types configured for @value{GDBN}
15649 (@pxref{Target Commands, ,Commands for Managing Targets}).
15651 @cindex target architecture
15652 It is possible to build @value{GDBN} for several different @dfn{target
15653 architectures}. When @value{GDBN} is built like that, you can choose
15654 one of the available architectures with the @kbd{set architecture}
15658 @kindex set architecture
15659 @kindex show architecture
15660 @item set architecture @var{arch}
15661 This command sets the current target architecture to @var{arch}. The
15662 value of @var{arch} can be @code{"auto"}, in addition to one of the
15663 supported architectures.
15665 @item show architecture
15666 Show the current target architecture.
15668 @item set processor
15670 @kindex set processor
15671 @kindex show processor
15672 These are alias commands for, respectively, @code{set architecture}
15673 and @code{show architecture}.
15677 * Active Targets:: Active targets
15678 * Target Commands:: Commands for managing targets
15679 * Byte Order:: Choosing target byte order
15682 @node Active Targets
15683 @section Active Targets
15685 @cindex stacking targets
15686 @cindex active targets
15687 @cindex multiple targets
15689 There are multiple classes of targets such as: processes, executable files or
15690 recording sessions. Core files belong to the process class, making core file
15691 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15692 on multiple active targets, one in each class. This allows you to (for
15693 example) start a process and inspect its activity, while still having access to
15694 the executable file after the process finishes. Or if you start process
15695 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15696 presented a virtual layer of the recording target, while the process target
15697 remains stopped at the chronologically last point of the process execution.
15699 Use the @code{core-file} and @code{exec-file} commands to select a new core
15700 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15701 specify as a target a process that is already running, use the @code{attach}
15702 command (@pxref{Attach, ,Debugging an Already-running Process}).
15704 @node Target Commands
15705 @section Commands for Managing Targets
15708 @item target @var{type} @var{parameters}
15709 Connects the @value{GDBN} host environment to a target machine or
15710 process. A target is typically a protocol for talking to debugging
15711 facilities. You use the argument @var{type} to specify the type or
15712 protocol of the target machine.
15714 Further @var{parameters} are interpreted by the target protocol, but
15715 typically include things like device names or host names to connect
15716 with, process numbers, and baud rates.
15718 The @code{target} command does not repeat if you press @key{RET} again
15719 after executing the command.
15721 @kindex help target
15723 Displays the names of all targets available. To display targets
15724 currently selected, use either @code{info target} or @code{info files}
15725 (@pxref{Files, ,Commands to Specify Files}).
15727 @item help target @var{name}
15728 Describe a particular target, including any parameters necessary to
15731 @kindex set gnutarget
15732 @item set gnutarget @var{args}
15733 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15734 knows whether it is reading an @dfn{executable},
15735 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15736 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15737 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15740 @emph{Warning:} To specify a file format with @code{set gnutarget},
15741 you must know the actual BFD name.
15745 @xref{Files, , Commands to Specify Files}.
15747 @kindex show gnutarget
15748 @item show gnutarget
15749 Use the @code{show gnutarget} command to display what file format
15750 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15751 @value{GDBN} will determine the file format for each file automatically,
15752 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15755 @cindex common targets
15756 Here are some common targets (available, or not, depending on the GDB
15761 @item target exec @var{program}
15762 @cindex executable file target
15763 An executable file. @samp{target exec @var{program}} is the same as
15764 @samp{exec-file @var{program}}.
15766 @item target core @var{filename}
15767 @cindex core dump file target
15768 A core dump file. @samp{target core @var{filename}} is the same as
15769 @samp{core-file @var{filename}}.
15771 @item target remote @var{medium}
15772 @cindex remote target
15773 A remote system connected to @value{GDBN} via a serial line or network
15774 connection. This command tells @value{GDBN} to use its own remote
15775 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15777 For example, if you have a board connected to @file{/dev/ttya} on the
15778 machine running @value{GDBN}, you could say:
15781 target remote /dev/ttya
15784 @code{target remote} supports the @code{load} command. This is only
15785 useful if you have some other way of getting the stub to the target
15786 system, and you can put it somewhere in memory where it won't get
15787 clobbered by the download.
15789 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15790 @cindex built-in simulator target
15791 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15799 works; however, you cannot assume that a specific memory map, device
15800 drivers, or even basic I/O is available, although some simulators do
15801 provide these. For info about any processor-specific simulator details,
15802 see the appropriate section in @ref{Embedded Processors, ,Embedded
15807 Some configurations may include these targets as well:
15811 @item target nrom @var{dev}
15812 @cindex NetROM ROM emulator target
15813 NetROM ROM emulator. This target only supports downloading.
15817 Different targets are available on different configurations of @value{GDBN};
15818 your configuration may have more or fewer targets.
15820 Many remote targets require you to download the executable's code once
15821 you've successfully established a connection. You may wish to control
15822 various aspects of this process.
15827 @kindex set hash@r{, for remote monitors}
15828 @cindex hash mark while downloading
15829 This command controls whether a hash mark @samp{#} is displayed while
15830 downloading a file to the remote monitor. If on, a hash mark is
15831 displayed after each S-record is successfully downloaded to the
15835 @kindex show hash@r{, for remote monitors}
15836 Show the current status of displaying the hash mark.
15838 @item set debug monitor
15839 @kindex set debug monitor
15840 @cindex display remote monitor communications
15841 Enable or disable display of communications messages between
15842 @value{GDBN} and the remote monitor.
15844 @item show debug monitor
15845 @kindex show debug monitor
15846 Show the current status of displaying communications between
15847 @value{GDBN} and the remote monitor.
15852 @kindex load @var{filename}
15853 @item load @var{filename}
15855 Depending on what remote debugging facilities are configured into
15856 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15857 is meant to make @var{filename} (an executable) available for debugging
15858 on the remote system---by downloading, or dynamic linking, for example.
15859 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15860 the @code{add-symbol-file} command.
15862 If your @value{GDBN} does not have a @code{load} command, attempting to
15863 execute it gets the error message ``@code{You can't do that when your
15864 target is @dots{}}''
15866 The file is loaded at whatever address is specified in the executable.
15867 For some object file formats, you can specify the load address when you
15868 link the program; for other formats, like a.out, the object file format
15869 specifies a fixed address.
15870 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15872 Depending on the remote side capabilities, @value{GDBN} may be able to
15873 load programs into flash memory.
15875 @code{load} does not repeat if you press @key{RET} again after using it.
15879 @section Choosing Target Byte Order
15881 @cindex choosing target byte order
15882 @cindex target byte order
15884 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15885 offer the ability to run either big-endian or little-endian byte
15886 orders. Usually the executable or symbol will include a bit to
15887 designate the endian-ness, and you will not need to worry about
15888 which to use. However, you may still find it useful to adjust
15889 @value{GDBN}'s idea of processor endian-ness manually.
15893 @item set endian big
15894 Instruct @value{GDBN} to assume the target is big-endian.
15896 @item set endian little
15897 Instruct @value{GDBN} to assume the target is little-endian.
15899 @item set endian auto
15900 Instruct @value{GDBN} to use the byte order associated with the
15904 Display @value{GDBN}'s current idea of the target byte order.
15908 Note that these commands merely adjust interpretation of symbolic
15909 data on the host, and that they have absolutely no effect on the
15913 @node Remote Debugging
15914 @chapter Debugging Remote Programs
15915 @cindex remote debugging
15917 If you are trying to debug a program running on a machine that cannot run
15918 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15919 For example, you might use remote debugging on an operating system kernel,
15920 or on a small system which does not have a general purpose operating system
15921 powerful enough to run a full-featured debugger.
15923 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15924 to make this work with particular debugging targets. In addition,
15925 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15926 but not specific to any particular target system) which you can use if you
15927 write the remote stubs---the code that runs on the remote system to
15928 communicate with @value{GDBN}.
15930 Other remote targets may be available in your
15931 configuration of @value{GDBN}; use @code{help target} to list them.
15934 * Connecting:: Connecting to a remote target
15935 * File Transfer:: Sending files to a remote system
15936 * Server:: Using the gdbserver program
15937 * Remote Configuration:: Remote configuration
15938 * Remote Stub:: Implementing a remote stub
15942 @section Connecting to a Remote Target
15944 On the @value{GDBN} host machine, you will need an unstripped copy of
15945 your program, since @value{GDBN} needs symbol and debugging information.
15946 Start up @value{GDBN} as usual, using the name of the local copy of your
15947 program as the first argument.
15949 @cindex @code{target remote}
15950 @value{GDBN} can communicate with the target over a serial line, or
15951 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15952 each case, @value{GDBN} uses the same protocol for debugging your
15953 program; only the medium carrying the debugging packets varies. The
15954 @code{target remote} command establishes a connection to the target.
15955 Its arguments indicate which medium to use:
15959 @item target remote @var{serial-device}
15960 @cindex serial line, @code{target remote}
15961 Use @var{serial-device} to communicate with the target. For example,
15962 to use a serial line connected to the device named @file{/dev/ttyb}:
15965 target remote /dev/ttyb
15968 If you're using a serial line, you may want to give @value{GDBN} the
15969 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15970 (@pxref{Remote Configuration, set remotebaud}) before the
15971 @code{target} command.
15973 @item target remote @code{@var{host}:@var{port}}
15974 @itemx target remote @code{tcp:@var{host}:@var{port}}
15975 @cindex @acronym{TCP} port, @code{target remote}
15976 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15977 The @var{host} may be either a host name or a numeric @acronym{IP}
15978 address; @var{port} must be a decimal number. The @var{host} could be
15979 the target machine itself, if it is directly connected to the net, or
15980 it might be a terminal server which in turn has a serial line to the
15983 For example, to connect to port 2828 on a terminal server named
15987 target remote manyfarms:2828
15990 If your remote target is actually running on the same machine as your
15991 debugger session (e.g.@: a simulator for your target running on the
15992 same host), you can omit the hostname. For example, to connect to
15993 port 1234 on your local machine:
15996 target remote :1234
16000 Note that the colon is still required here.
16002 @item target remote @code{udp:@var{host}:@var{port}}
16003 @cindex @acronym{UDP} port, @code{target remote}
16004 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16005 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16008 target remote udp:manyfarms:2828
16011 When using a @acronym{UDP} connection for remote debugging, you should
16012 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16013 can silently drop packets on busy or unreliable networks, which will
16014 cause havoc with your debugging session.
16016 @item target remote | @var{command}
16017 @cindex pipe, @code{target remote} to
16018 Run @var{command} in the background and communicate with it using a
16019 pipe. The @var{command} is a shell command, to be parsed and expanded
16020 by the system's command shell, @code{/bin/sh}; it should expect remote
16021 protocol packets on its standard input, and send replies on its
16022 standard output. You could use this to run a stand-alone simulator
16023 that speaks the remote debugging protocol, to make net connections
16024 using programs like @code{ssh}, or for other similar tricks.
16026 If @var{command} closes its standard output (perhaps by exiting),
16027 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16028 program has already exited, this will have no effect.)
16032 Once the connection has been established, you can use all the usual
16033 commands to examine and change data. The remote program is already
16034 running; you can use @kbd{step} and @kbd{continue}, and you do not
16035 need to use @kbd{run}.
16037 @cindex interrupting remote programs
16038 @cindex remote programs, interrupting
16039 Whenever @value{GDBN} is waiting for the remote program, if you type the
16040 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16041 program. This may or may not succeed, depending in part on the hardware
16042 and the serial drivers the remote system uses. If you type the
16043 interrupt character once again, @value{GDBN} displays this prompt:
16046 Interrupted while waiting for the program.
16047 Give up (and stop debugging it)? (y or n)
16050 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16051 (If you decide you want to try again later, you can use @samp{target
16052 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16053 goes back to waiting.
16056 @kindex detach (remote)
16058 When you have finished debugging the remote program, you can use the
16059 @code{detach} command to release it from @value{GDBN} control.
16060 Detaching from the target normally resumes its execution, but the results
16061 will depend on your particular remote stub. After the @code{detach}
16062 command, @value{GDBN} is free to connect to another target.
16066 The @code{disconnect} command behaves like @code{detach}, except that
16067 the target is generally not resumed. It will wait for @value{GDBN}
16068 (this instance or another one) to connect and continue debugging. After
16069 the @code{disconnect} command, @value{GDBN} is again free to connect to
16072 @cindex send command to remote monitor
16073 @cindex extend @value{GDBN} for remote targets
16074 @cindex add new commands for external monitor
16076 @item monitor @var{cmd}
16077 This command allows you to send arbitrary commands directly to the
16078 remote monitor. Since @value{GDBN} doesn't care about the commands it
16079 sends like this, this command is the way to extend @value{GDBN}---you
16080 can add new commands that only the external monitor will understand
16084 @node File Transfer
16085 @section Sending files to a remote system
16086 @cindex remote target, file transfer
16087 @cindex file transfer
16088 @cindex sending files to remote systems
16090 Some remote targets offer the ability to transfer files over the same
16091 connection used to communicate with @value{GDBN}. This is convenient
16092 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16093 running @code{gdbserver} over a network interface. For other targets,
16094 e.g.@: embedded devices with only a single serial port, this may be
16095 the only way to upload or download files.
16097 Not all remote targets support these commands.
16101 @item remote put @var{hostfile} @var{targetfile}
16102 Copy file @var{hostfile} from the host system (the machine running
16103 @value{GDBN}) to @var{targetfile} on the target system.
16106 @item remote get @var{targetfile} @var{hostfile}
16107 Copy file @var{targetfile} from the target system to @var{hostfile}
16108 on the host system.
16110 @kindex remote delete
16111 @item remote delete @var{targetfile}
16112 Delete @var{targetfile} from the target system.
16117 @section Using the @code{gdbserver} Program
16120 @cindex remote connection without stubs
16121 @code{gdbserver} is a control program for Unix-like systems, which
16122 allows you to connect your program with a remote @value{GDBN} via
16123 @code{target remote}---but without linking in the usual debugging stub.
16125 @code{gdbserver} is not a complete replacement for the debugging stubs,
16126 because it requires essentially the same operating-system facilities
16127 that @value{GDBN} itself does. In fact, a system that can run
16128 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16129 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16130 because it is a much smaller program than @value{GDBN} itself. It is
16131 also easier to port than all of @value{GDBN}, so you may be able to get
16132 started more quickly on a new system by using @code{gdbserver}.
16133 Finally, if you develop code for real-time systems, you may find that
16134 the tradeoffs involved in real-time operation make it more convenient to
16135 do as much development work as possible on another system, for example
16136 by cross-compiling. You can use @code{gdbserver} to make a similar
16137 choice for debugging.
16139 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16140 or a TCP connection, using the standard @value{GDBN} remote serial
16144 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16145 Do not run @code{gdbserver} connected to any public network; a
16146 @value{GDBN} connection to @code{gdbserver} provides access to the
16147 target system with the same privileges as the user running
16151 @subsection Running @code{gdbserver}
16152 @cindex arguments, to @code{gdbserver}
16153 @cindex @code{gdbserver}, command-line arguments
16155 Run @code{gdbserver} on the target system. You need a copy of the
16156 program you want to debug, including any libraries it requires.
16157 @code{gdbserver} does not need your program's symbol table, so you can
16158 strip the program if necessary to save space. @value{GDBN} on the host
16159 system does all the symbol handling.
16161 To use the server, you must tell it how to communicate with @value{GDBN};
16162 the name of your program; and the arguments for your program. The usual
16166 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16169 @var{comm} is either a device name (to use a serial line) or a TCP
16170 hostname and portnumber. For example, to debug Emacs with the argument
16171 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16175 target> gdbserver /dev/com1 emacs foo.txt
16178 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16181 To use a TCP connection instead of a serial line:
16184 target> gdbserver host:2345 emacs foo.txt
16187 The only difference from the previous example is the first argument,
16188 specifying that you are communicating with the host @value{GDBN} via
16189 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16190 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16191 (Currently, the @samp{host} part is ignored.) You can choose any number
16192 you want for the port number as long as it does not conflict with any
16193 TCP ports already in use on the target system (for example, @code{23} is
16194 reserved for @code{telnet}).@footnote{If you choose a port number that
16195 conflicts with another service, @code{gdbserver} prints an error message
16196 and exits.} You must use the same port number with the host @value{GDBN}
16197 @code{target remote} command.
16199 @subsubsection Attaching to a Running Program
16200 @cindex attach to a program, @code{gdbserver}
16201 @cindex @option{--attach}, @code{gdbserver} option
16203 On some targets, @code{gdbserver} can also attach to running programs.
16204 This is accomplished via the @code{--attach} argument. The syntax is:
16207 target> gdbserver --attach @var{comm} @var{pid}
16210 @var{pid} is the process ID of a currently running process. It isn't necessary
16211 to point @code{gdbserver} at a binary for the running process.
16214 You can debug processes by name instead of process ID if your target has the
16215 @code{pidof} utility:
16218 target> gdbserver --attach @var{comm} `pidof @var{program}`
16221 In case more than one copy of @var{program} is running, or @var{program}
16222 has multiple threads, most versions of @code{pidof} support the
16223 @code{-s} option to only return the first process ID.
16225 @subsubsection Multi-Process Mode for @code{gdbserver}
16226 @cindex @code{gdbserver}, multiple processes
16227 @cindex multiple processes with @code{gdbserver}
16229 When you connect to @code{gdbserver} using @code{target remote},
16230 @code{gdbserver} debugs the specified program only once. When the
16231 program exits, or you detach from it, @value{GDBN} closes the connection
16232 and @code{gdbserver} exits.
16234 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16235 enters multi-process mode. When the debugged program exits, or you
16236 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16237 though no program is running. The @code{run} and @code{attach}
16238 commands instruct @code{gdbserver} to run or attach to a new program.
16239 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16240 remote exec-file}) to select the program to run. Command line
16241 arguments are supported, except for wildcard expansion and I/O
16242 redirection (@pxref{Arguments}).
16244 @cindex @option{--multi}, @code{gdbserver} option
16245 To start @code{gdbserver} without supplying an initial command to run
16246 or process ID to attach, use the @option{--multi} command line option.
16247 Then you can connect using @kbd{target extended-remote} and start
16248 the program you want to debug.
16250 In multi-process mode @code{gdbserver} does not automatically exit unless you
16251 use the option @option{--once}. You can terminate it by using
16252 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16253 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16254 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16255 @option{--multi} option to @code{gdbserver} has no influence on that.
16257 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16259 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16261 @code{gdbserver} normally terminates after all of its debugged processes have
16262 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16263 extended-remote}, @code{gdbserver} stays running even with no processes left.
16264 @value{GDBN} normally terminates the spawned debugged process on its exit,
16265 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16266 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16267 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16268 stays running even in the @kbd{target remote} mode.
16270 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16271 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16272 completeness, at most one @value{GDBN} can be connected at a time.
16274 @cindex @option{--once}, @code{gdbserver} option
16275 By default, @code{gdbserver} keeps the listening TCP port open, so that
16276 additional connections are possible. However, if you start @code{gdbserver}
16277 with the @option{--once} option, it will stop listening for any further
16278 connection attempts after connecting to the first @value{GDBN} session. This
16279 means no further connections to @code{gdbserver} will be possible after the
16280 first one. It also means @code{gdbserver} will terminate after the first
16281 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16282 connections and even in the @kbd{target extended-remote} mode. The
16283 @option{--once} option allows reusing the same port number for connecting to
16284 multiple instances of @code{gdbserver} running on the same host, since each
16285 instance closes its port after the first connection.
16287 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16289 @cindex @option{--debug}, @code{gdbserver} option
16290 The @option{--debug} option tells @code{gdbserver} to display extra
16291 status information about the debugging process.
16292 @cindex @option{--remote-debug}, @code{gdbserver} option
16293 The @option{--remote-debug} option tells @code{gdbserver} to display
16294 remote protocol debug output. These options are intended for
16295 @code{gdbserver} development and for bug reports to the developers.
16297 @cindex @option{--wrapper}, @code{gdbserver} option
16298 The @option{--wrapper} option specifies a wrapper to launch programs
16299 for debugging. The option should be followed by the name of the
16300 wrapper, then any command-line arguments to pass to the wrapper, then
16301 @kbd{--} indicating the end of the wrapper arguments.
16303 @code{gdbserver} runs the specified wrapper program with a combined
16304 command line including the wrapper arguments, then the name of the
16305 program to debug, then any arguments to the program. The wrapper
16306 runs until it executes your program, and then @value{GDBN} gains control.
16308 You can use any program that eventually calls @code{execve} with
16309 its arguments as a wrapper. Several standard Unix utilities do
16310 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16311 with @code{exec "$@@"} will also work.
16313 For example, you can use @code{env} to pass an environment variable to
16314 the debugged program, without setting the variable in @code{gdbserver}'s
16318 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16321 @subsection Connecting to @code{gdbserver}
16323 Run @value{GDBN} on the host system.
16325 First make sure you have the necessary symbol files. Load symbols for
16326 your application using the @code{file} command before you connect. Use
16327 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16328 was compiled with the correct sysroot using @code{--with-sysroot}).
16330 The symbol file and target libraries must exactly match the executable
16331 and libraries on the target, with one exception: the files on the host
16332 system should not be stripped, even if the files on the target system
16333 are. Mismatched or missing files will lead to confusing results
16334 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16335 files may also prevent @code{gdbserver} from debugging multi-threaded
16338 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16339 For TCP connections, you must start up @code{gdbserver} prior to using
16340 the @code{target remote} command. Otherwise you may get an error whose
16341 text depends on the host system, but which usually looks something like
16342 @samp{Connection refused}. Don't use the @code{load}
16343 command in @value{GDBN} when using @code{gdbserver}, since the program is
16344 already on the target.
16346 @subsection Monitor Commands for @code{gdbserver}
16347 @cindex monitor commands, for @code{gdbserver}
16348 @anchor{Monitor Commands for gdbserver}
16350 During a @value{GDBN} session using @code{gdbserver}, you can use the
16351 @code{monitor} command to send special requests to @code{gdbserver}.
16352 Here are the available commands.
16356 List the available monitor commands.
16358 @item monitor set debug 0
16359 @itemx monitor set debug 1
16360 Disable or enable general debugging messages.
16362 @item monitor set remote-debug 0
16363 @itemx monitor set remote-debug 1
16364 Disable or enable specific debugging messages associated with the remote
16365 protocol (@pxref{Remote Protocol}).
16367 @item monitor set libthread-db-search-path [PATH]
16368 @cindex gdbserver, search path for @code{libthread_db}
16369 When this command is issued, @var{path} is a colon-separated list of
16370 directories to search for @code{libthread_db} (@pxref{Threads,,set
16371 libthread-db-search-path}). If you omit @var{path},
16372 @samp{libthread-db-search-path} will be reset to an empty list.
16375 Tell gdbserver to exit immediately. This command should be followed by
16376 @code{disconnect} to close the debugging session. @code{gdbserver} will
16377 detach from any attached processes and kill any processes it created.
16378 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16379 of a multi-process mode debug session.
16383 @subsection Tracepoints support in @code{gdbserver}
16384 @cindex tracepoints support in @code{gdbserver}
16386 On some targets, @code{gdbserver} supports tracepoints, fast
16387 tracepoints and static tracepoints.
16389 For fast or static tracepoints to work, a special library called the
16390 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16391 This library is built and distributed as an integral part of
16392 @code{gdbserver}. In addition, support for static tracepoints
16393 requires building the in-process agent library with static tracepoints
16394 support. At present, the UST (LTTng Userspace Tracer,
16395 @url{http://lttng.org/ust}) tracing engine is supported. This support
16396 is automatically available if UST development headers are found in the
16397 standard include path when @code{gdbserver} is built, or if
16398 @code{gdbserver} was explicitly configured using @option{--with-ust}
16399 to point at such headers. You can explicitly disable the support
16400 using @option{--with-ust=no}.
16402 There are several ways to load the in-process agent in your program:
16405 @item Specifying it as dependency at link time
16407 You can link your program dynamically with the in-process agent
16408 library. On most systems, this is accomplished by adding
16409 @code{-linproctrace} to the link command.
16411 @item Using the system's preloading mechanisms
16413 You can force loading the in-process agent at startup time by using
16414 your system's support for preloading shared libraries. Many Unixes
16415 support the concept of preloading user defined libraries. In most
16416 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16417 in the environment. See also the description of @code{gdbserver}'s
16418 @option{--wrapper} command line option.
16420 @item Using @value{GDBN} to force loading the agent at run time
16422 On some systems, you can force the inferior to load a shared library,
16423 by calling a dynamic loader function in the inferior that takes care
16424 of dynamically looking up and loading a shared library. On most Unix
16425 systems, the function is @code{dlopen}. You'll use the @code{call}
16426 command for that. For example:
16429 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16432 Note that on most Unix systems, for the @code{dlopen} function to be
16433 available, the program needs to be linked with @code{-ldl}.
16436 On systems that have a userspace dynamic loader, like most Unix
16437 systems, when you connect to @code{gdbserver} using @code{target
16438 remote}, you'll find that the program is stopped at the dynamic
16439 loader's entry point, and no shared library has been loaded in the
16440 program's address space yet, including the in-process agent. In that
16441 case, before being able to use any of the fast or static tracepoints
16442 features, you need to let the loader run and load the shared
16443 libraries. The simplest way to do that is to run the program to the
16444 main procedure. E.g., if debugging a C or C@t{++} program, start
16445 @code{gdbserver} like so:
16448 $ gdbserver :9999 myprogram
16451 Start GDB and connect to @code{gdbserver} like so, and run to main:
16455 (@value{GDBP}) target remote myhost:9999
16456 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16457 (@value{GDBP}) b main
16458 (@value{GDBP}) continue
16461 The in-process tracing agent library should now be loaded into the
16462 process; you can confirm it with the @code{info sharedlibrary}
16463 command, which will list @file{libinproctrace.so} as loaded in the
16464 process. You are now ready to install fast tracepoints, list static
16465 tracepoint markers, probe static tracepoints markers, and start
16468 @node Remote Configuration
16469 @section Remote Configuration
16472 @kindex show remote
16473 This section documents the configuration options available when
16474 debugging remote programs. For the options related to the File I/O
16475 extensions of the remote protocol, see @ref{system,
16476 system-call-allowed}.
16479 @item set remoteaddresssize @var{bits}
16480 @cindex address size for remote targets
16481 @cindex bits in remote address
16482 Set the maximum size of address in a memory packet to the specified
16483 number of bits. @value{GDBN} will mask off the address bits above
16484 that number, when it passes addresses to the remote target. The
16485 default value is the number of bits in the target's address.
16487 @item show remoteaddresssize
16488 Show the current value of remote address size in bits.
16490 @item set remotebaud @var{n}
16491 @cindex baud rate for remote targets
16492 Set the baud rate for the remote serial I/O to @var{n} baud. The
16493 value is used to set the speed of the serial port used for debugging
16496 @item show remotebaud
16497 Show the current speed of the remote connection.
16499 @item set remotebreak
16500 @cindex interrupt remote programs
16501 @cindex BREAK signal instead of Ctrl-C
16502 @anchor{set remotebreak}
16503 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16504 when you type @kbd{Ctrl-c} to interrupt the program running
16505 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16506 character instead. The default is off, since most remote systems
16507 expect to see @samp{Ctrl-C} as the interrupt signal.
16509 @item show remotebreak
16510 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16511 interrupt the remote program.
16513 @item set remoteflow on
16514 @itemx set remoteflow off
16515 @kindex set remoteflow
16516 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16517 on the serial port used to communicate to the remote target.
16519 @item show remoteflow
16520 @kindex show remoteflow
16521 Show the current setting of hardware flow control.
16523 @item set remotelogbase @var{base}
16524 Set the base (a.k.a.@: radix) of logging serial protocol
16525 communications to @var{base}. Supported values of @var{base} are:
16526 @code{ascii}, @code{octal}, and @code{hex}. The default is
16529 @item show remotelogbase
16530 Show the current setting of the radix for logging remote serial
16533 @item set remotelogfile @var{file}
16534 @cindex record serial communications on file
16535 Record remote serial communications on the named @var{file}. The
16536 default is not to record at all.
16538 @item show remotelogfile.
16539 Show the current setting of the file name on which to record the
16540 serial communications.
16542 @item set remotetimeout @var{num}
16543 @cindex timeout for serial communications
16544 @cindex remote timeout
16545 Set the timeout limit to wait for the remote target to respond to
16546 @var{num} seconds. The default is 2 seconds.
16548 @item show remotetimeout
16549 Show the current number of seconds to wait for the remote target
16552 @cindex limit hardware breakpoints and watchpoints
16553 @cindex remote target, limit break- and watchpoints
16554 @anchor{set remote hardware-watchpoint-limit}
16555 @anchor{set remote hardware-breakpoint-limit}
16556 @item set remote hardware-watchpoint-limit @var{limit}
16557 @itemx set remote hardware-breakpoint-limit @var{limit}
16558 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16559 watchpoints. A limit of -1, the default, is treated as unlimited.
16561 @item set remote exec-file @var{filename}
16562 @itemx show remote exec-file
16563 @anchor{set remote exec-file}
16564 @cindex executable file, for remote target
16565 Select the file used for @code{run} with @code{target
16566 extended-remote}. This should be set to a filename valid on the
16567 target system. If it is not set, the target will use a default
16568 filename (e.g.@: the last program run).
16570 @item set remote interrupt-sequence
16571 @cindex interrupt remote programs
16572 @cindex select Ctrl-C, BREAK or BREAK-g
16573 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16574 @samp{BREAK-g} as the
16575 sequence to the remote target in order to interrupt the execution.
16576 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16577 is high level of serial line for some certain time.
16578 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16579 It is @code{BREAK} signal followed by character @code{g}.
16581 @item show interrupt-sequence
16582 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16583 is sent by @value{GDBN} to interrupt the remote program.
16584 @code{BREAK-g} is BREAK signal followed by @code{g} and
16585 also known as Magic SysRq g.
16587 @item set remote interrupt-on-connect
16588 @cindex send interrupt-sequence on start
16589 Specify whether interrupt-sequence is sent to remote target when
16590 @value{GDBN} connects to it. This is mostly needed when you debug
16591 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16592 which is known as Magic SysRq g in order to connect @value{GDBN}.
16594 @item show interrupt-on-connect
16595 Show whether interrupt-sequence is sent
16596 to remote target when @value{GDBN} connects to it.
16600 @item set tcp auto-retry on
16601 @cindex auto-retry, for remote TCP target
16602 Enable auto-retry for remote TCP connections. This is useful if the remote
16603 debugging agent is launched in parallel with @value{GDBN}; there is a race
16604 condition because the agent may not become ready to accept the connection
16605 before @value{GDBN} attempts to connect. When auto-retry is
16606 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16607 to establish the connection using the timeout specified by
16608 @code{set tcp connect-timeout}.
16610 @item set tcp auto-retry off
16611 Do not auto-retry failed TCP connections.
16613 @item show tcp auto-retry
16614 Show the current auto-retry setting.
16616 @item set tcp connect-timeout @var{seconds}
16617 @cindex connection timeout, for remote TCP target
16618 @cindex timeout, for remote target connection
16619 Set the timeout for establishing a TCP connection to the remote target to
16620 @var{seconds}. The timeout affects both polling to retry failed connections
16621 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16622 that are merely slow to complete, and represents an approximate cumulative
16625 @item show tcp connect-timeout
16626 Show the current connection timeout setting.
16629 @cindex remote packets, enabling and disabling
16630 The @value{GDBN} remote protocol autodetects the packets supported by
16631 your debugging stub. If you need to override the autodetection, you
16632 can use these commands to enable or disable individual packets. Each
16633 packet can be set to @samp{on} (the remote target supports this
16634 packet), @samp{off} (the remote target does not support this packet),
16635 or @samp{auto} (detect remote target support for this packet). They
16636 all default to @samp{auto}. For more information about each packet,
16637 see @ref{Remote Protocol}.
16639 During normal use, you should not have to use any of these commands.
16640 If you do, that may be a bug in your remote debugging stub, or a bug
16641 in @value{GDBN}. You may want to report the problem to the
16642 @value{GDBN} developers.
16644 For each packet @var{name}, the command to enable or disable the
16645 packet is @code{set remote @var{name}-packet}. The available settings
16648 @multitable @columnfractions 0.28 0.32 0.25
16651 @tab Related Features
16653 @item @code{fetch-register}
16655 @tab @code{info registers}
16657 @item @code{set-register}
16661 @item @code{binary-download}
16663 @tab @code{load}, @code{set}
16665 @item @code{read-aux-vector}
16666 @tab @code{qXfer:auxv:read}
16667 @tab @code{info auxv}
16669 @item @code{symbol-lookup}
16670 @tab @code{qSymbol}
16671 @tab Detecting multiple threads
16673 @item @code{attach}
16674 @tab @code{vAttach}
16677 @item @code{verbose-resume}
16679 @tab Stepping or resuming multiple threads
16685 @item @code{software-breakpoint}
16689 @item @code{hardware-breakpoint}
16693 @item @code{write-watchpoint}
16697 @item @code{read-watchpoint}
16701 @item @code{access-watchpoint}
16705 @item @code{target-features}
16706 @tab @code{qXfer:features:read}
16707 @tab @code{set architecture}
16709 @item @code{library-info}
16710 @tab @code{qXfer:libraries:read}
16711 @tab @code{info sharedlibrary}
16713 @item @code{memory-map}
16714 @tab @code{qXfer:memory-map:read}
16715 @tab @code{info mem}
16717 @item @code{read-sdata-object}
16718 @tab @code{qXfer:sdata:read}
16719 @tab @code{print $_sdata}
16721 @item @code{read-spu-object}
16722 @tab @code{qXfer:spu:read}
16723 @tab @code{info spu}
16725 @item @code{write-spu-object}
16726 @tab @code{qXfer:spu:write}
16727 @tab @code{info spu}
16729 @item @code{read-siginfo-object}
16730 @tab @code{qXfer:siginfo:read}
16731 @tab @code{print $_siginfo}
16733 @item @code{write-siginfo-object}
16734 @tab @code{qXfer:siginfo:write}
16735 @tab @code{set $_siginfo}
16737 @item @code{threads}
16738 @tab @code{qXfer:threads:read}
16739 @tab @code{info threads}
16741 @item @code{get-thread-local-@*storage-address}
16742 @tab @code{qGetTLSAddr}
16743 @tab Displaying @code{__thread} variables
16745 @item @code{get-thread-information-block-address}
16746 @tab @code{qGetTIBAddr}
16747 @tab Display MS-Windows Thread Information Block.
16749 @item @code{search-memory}
16750 @tab @code{qSearch:memory}
16753 @item @code{supported-packets}
16754 @tab @code{qSupported}
16755 @tab Remote communications parameters
16757 @item @code{pass-signals}
16758 @tab @code{QPassSignals}
16759 @tab @code{handle @var{signal}}
16761 @item @code{hostio-close-packet}
16762 @tab @code{vFile:close}
16763 @tab @code{remote get}, @code{remote put}
16765 @item @code{hostio-open-packet}
16766 @tab @code{vFile:open}
16767 @tab @code{remote get}, @code{remote put}
16769 @item @code{hostio-pread-packet}
16770 @tab @code{vFile:pread}
16771 @tab @code{remote get}, @code{remote put}
16773 @item @code{hostio-pwrite-packet}
16774 @tab @code{vFile:pwrite}
16775 @tab @code{remote get}, @code{remote put}
16777 @item @code{hostio-unlink-packet}
16778 @tab @code{vFile:unlink}
16779 @tab @code{remote delete}
16781 @item @code{noack-packet}
16782 @tab @code{QStartNoAckMode}
16783 @tab Packet acknowledgment
16785 @item @code{osdata}
16786 @tab @code{qXfer:osdata:read}
16787 @tab @code{info os}
16789 @item @code{query-attached}
16790 @tab @code{qAttached}
16791 @tab Querying remote process attach state.
16793 @item @code{traceframe-info}
16794 @tab @code{qXfer:traceframe-info:read}
16795 @tab Traceframe info
16799 @section Implementing a Remote Stub
16801 @cindex debugging stub, example
16802 @cindex remote stub, example
16803 @cindex stub example, remote debugging
16804 The stub files provided with @value{GDBN} implement the target side of the
16805 communication protocol, and the @value{GDBN} side is implemented in the
16806 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16807 these subroutines to communicate, and ignore the details. (If you're
16808 implementing your own stub file, you can still ignore the details: start
16809 with one of the existing stub files. @file{sparc-stub.c} is the best
16810 organized, and therefore the easiest to read.)
16812 @cindex remote serial debugging, overview
16813 To debug a program running on another machine (the debugging
16814 @dfn{target} machine), you must first arrange for all the usual
16815 prerequisites for the program to run by itself. For example, for a C
16820 A startup routine to set up the C runtime environment; these usually
16821 have a name like @file{crt0}. The startup routine may be supplied by
16822 your hardware supplier, or you may have to write your own.
16825 A C subroutine library to support your program's
16826 subroutine calls, notably managing input and output.
16829 A way of getting your program to the other machine---for example, a
16830 download program. These are often supplied by the hardware
16831 manufacturer, but you may have to write your own from hardware
16835 The next step is to arrange for your program to use a serial port to
16836 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16837 machine). In general terms, the scheme looks like this:
16841 @value{GDBN} already understands how to use this protocol; when everything
16842 else is set up, you can simply use the @samp{target remote} command
16843 (@pxref{Targets,,Specifying a Debugging Target}).
16845 @item On the target,
16846 you must link with your program a few special-purpose subroutines that
16847 implement the @value{GDBN} remote serial protocol. The file containing these
16848 subroutines is called a @dfn{debugging stub}.
16850 On certain remote targets, you can use an auxiliary program
16851 @code{gdbserver} instead of linking a stub into your program.
16852 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16855 The debugging stub is specific to the architecture of the remote
16856 machine; for example, use @file{sparc-stub.c} to debug programs on
16859 @cindex remote serial stub list
16860 These working remote stubs are distributed with @value{GDBN}:
16865 @cindex @file{i386-stub.c}
16868 For Intel 386 and compatible architectures.
16871 @cindex @file{m68k-stub.c}
16872 @cindex Motorola 680x0
16874 For Motorola 680x0 architectures.
16877 @cindex @file{sh-stub.c}
16880 For Renesas SH architectures.
16883 @cindex @file{sparc-stub.c}
16885 For @sc{sparc} architectures.
16887 @item sparcl-stub.c
16888 @cindex @file{sparcl-stub.c}
16891 For Fujitsu @sc{sparclite} architectures.
16895 The @file{README} file in the @value{GDBN} distribution may list other
16896 recently added stubs.
16899 * Stub Contents:: What the stub can do for you
16900 * Bootstrapping:: What you must do for the stub
16901 * Debug Session:: Putting it all together
16904 @node Stub Contents
16905 @subsection What the Stub Can Do for You
16907 @cindex remote serial stub
16908 The debugging stub for your architecture supplies these three
16912 @item set_debug_traps
16913 @findex set_debug_traps
16914 @cindex remote serial stub, initialization
16915 This routine arranges for @code{handle_exception} to run when your
16916 program stops. You must call this subroutine explicitly near the
16917 beginning of your program.
16919 @item handle_exception
16920 @findex handle_exception
16921 @cindex remote serial stub, main routine
16922 This is the central workhorse, but your program never calls it
16923 explicitly---the setup code arranges for @code{handle_exception} to
16924 run when a trap is triggered.
16926 @code{handle_exception} takes control when your program stops during
16927 execution (for example, on a breakpoint), and mediates communications
16928 with @value{GDBN} on the host machine. This is where the communications
16929 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16930 representative on the target machine. It begins by sending summary
16931 information on the state of your program, then continues to execute,
16932 retrieving and transmitting any information @value{GDBN} needs, until you
16933 execute a @value{GDBN} command that makes your program resume; at that point,
16934 @code{handle_exception} returns control to your own code on the target
16938 @cindex @code{breakpoint} subroutine, remote
16939 Use this auxiliary subroutine to make your program contain a
16940 breakpoint. Depending on the particular situation, this may be the only
16941 way for @value{GDBN} to get control. For instance, if your target
16942 machine has some sort of interrupt button, you won't need to call this;
16943 pressing the interrupt button transfers control to
16944 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16945 simply receiving characters on the serial port may also trigger a trap;
16946 again, in that situation, you don't need to call @code{breakpoint} from
16947 your own program---simply running @samp{target remote} from the host
16948 @value{GDBN} session gets control.
16950 Call @code{breakpoint} if none of these is true, or if you simply want
16951 to make certain your program stops at a predetermined point for the
16952 start of your debugging session.
16955 @node Bootstrapping
16956 @subsection What You Must Do for the Stub
16958 @cindex remote stub, support routines
16959 The debugging stubs that come with @value{GDBN} are set up for a particular
16960 chip architecture, but they have no information about the rest of your
16961 debugging target machine.
16963 First of all you need to tell the stub how to communicate with the
16967 @item int getDebugChar()
16968 @findex getDebugChar
16969 Write this subroutine to read a single character from the serial port.
16970 It may be identical to @code{getchar} for your target system; a
16971 different name is used to allow you to distinguish the two if you wish.
16973 @item void putDebugChar(int)
16974 @findex putDebugChar
16975 Write this subroutine to write a single character to the serial port.
16976 It may be identical to @code{putchar} for your target system; a
16977 different name is used to allow you to distinguish the two if you wish.
16980 @cindex control C, and remote debugging
16981 @cindex interrupting remote targets
16982 If you want @value{GDBN} to be able to stop your program while it is
16983 running, you need to use an interrupt-driven serial driver, and arrange
16984 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16985 character). That is the character which @value{GDBN} uses to tell the
16986 remote system to stop.
16988 Getting the debugging target to return the proper status to @value{GDBN}
16989 probably requires changes to the standard stub; one quick and dirty way
16990 is to just execute a breakpoint instruction (the ``dirty'' part is that
16991 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16993 Other routines you need to supply are:
16996 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16997 @findex exceptionHandler
16998 Write this function to install @var{exception_address} in the exception
16999 handling tables. You need to do this because the stub does not have any
17000 way of knowing what the exception handling tables on your target system
17001 are like (for example, the processor's table might be in @sc{rom},
17002 containing entries which point to a table in @sc{ram}).
17003 @var{exception_number} is the exception number which should be changed;
17004 its meaning is architecture-dependent (for example, different numbers
17005 might represent divide by zero, misaligned access, etc). When this
17006 exception occurs, control should be transferred directly to
17007 @var{exception_address}, and the processor state (stack, registers,
17008 and so on) should be just as it is when a processor exception occurs. So if
17009 you want to use a jump instruction to reach @var{exception_address}, it
17010 should be a simple jump, not a jump to subroutine.
17012 For the 386, @var{exception_address} should be installed as an interrupt
17013 gate so that interrupts are masked while the handler runs. The gate
17014 should be at privilege level 0 (the most privileged level). The
17015 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17016 help from @code{exceptionHandler}.
17018 @item void flush_i_cache()
17019 @findex flush_i_cache
17020 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17021 instruction cache, if any, on your target machine. If there is no
17022 instruction cache, this subroutine may be a no-op.
17024 On target machines that have instruction caches, @value{GDBN} requires this
17025 function to make certain that the state of your program is stable.
17029 You must also make sure this library routine is available:
17032 @item void *memset(void *, int, int)
17034 This is the standard library function @code{memset} that sets an area of
17035 memory to a known value. If you have one of the free versions of
17036 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17037 either obtain it from your hardware manufacturer, or write your own.
17040 If you do not use the GNU C compiler, you may need other standard
17041 library subroutines as well; this varies from one stub to another,
17042 but in general the stubs are likely to use any of the common library
17043 subroutines which @code{@value{NGCC}} generates as inline code.
17046 @node Debug Session
17047 @subsection Putting it All Together
17049 @cindex remote serial debugging summary
17050 In summary, when your program is ready to debug, you must follow these
17055 Make sure you have defined the supporting low-level routines
17056 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17058 @code{getDebugChar}, @code{putDebugChar},
17059 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17063 Insert these lines near the top of your program:
17071 For the 680x0 stub only, you need to provide a variable called
17072 @code{exceptionHook}. Normally you just use:
17075 void (*exceptionHook)() = 0;
17079 but if before calling @code{set_debug_traps}, you set it to point to a
17080 function in your program, that function is called when
17081 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17082 error). The function indicated by @code{exceptionHook} is called with
17083 one parameter: an @code{int} which is the exception number.
17086 Compile and link together: your program, the @value{GDBN} debugging stub for
17087 your target architecture, and the supporting subroutines.
17090 Make sure you have a serial connection between your target machine and
17091 the @value{GDBN} host, and identify the serial port on the host.
17094 @c The "remote" target now provides a `load' command, so we should
17095 @c document that. FIXME.
17096 Download your program to your target machine (or get it there by
17097 whatever means the manufacturer provides), and start it.
17100 Start @value{GDBN} on the host, and connect to the target
17101 (@pxref{Connecting,,Connecting to a Remote Target}).
17105 @node Configurations
17106 @chapter Configuration-Specific Information
17108 While nearly all @value{GDBN} commands are available for all native and
17109 cross versions of the debugger, there are some exceptions. This chapter
17110 describes things that are only available in certain configurations.
17112 There are three major categories of configurations: native
17113 configurations, where the host and target are the same, embedded
17114 operating system configurations, which are usually the same for several
17115 different processor architectures, and bare embedded processors, which
17116 are quite different from each other.
17121 * Embedded Processors::
17128 This section describes details specific to particular native
17133 * BSD libkvm Interface:: Debugging BSD kernel memory images
17134 * SVR4 Process Information:: SVR4 process information
17135 * DJGPP Native:: Features specific to the DJGPP port
17136 * Cygwin Native:: Features specific to the Cygwin port
17137 * Hurd Native:: Features specific to @sc{gnu} Hurd
17138 * Neutrino:: Features specific to QNX Neutrino
17139 * Darwin:: Features specific to Darwin
17145 On HP-UX systems, if you refer to a function or variable name that
17146 begins with a dollar sign, @value{GDBN} searches for a user or system
17147 name first, before it searches for a convenience variable.
17150 @node BSD libkvm Interface
17151 @subsection BSD libkvm Interface
17154 @cindex kernel memory image
17155 @cindex kernel crash dump
17157 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17158 interface that provides a uniform interface for accessing kernel virtual
17159 memory images, including live systems and crash dumps. @value{GDBN}
17160 uses this interface to allow you to debug live kernels and kernel crash
17161 dumps on many native BSD configurations. This is implemented as a
17162 special @code{kvm} debugging target. For debugging a live system, load
17163 the currently running kernel into @value{GDBN} and connect to the
17167 (@value{GDBP}) @b{target kvm}
17170 For debugging crash dumps, provide the file name of the crash dump as an
17174 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17177 Once connected to the @code{kvm} target, the following commands are
17183 Set current context from the @dfn{Process Control Block} (PCB) address.
17186 Set current context from proc address. This command isn't available on
17187 modern FreeBSD systems.
17190 @node SVR4 Process Information
17191 @subsection SVR4 Process Information
17193 @cindex examine process image
17194 @cindex process info via @file{/proc}
17196 Many versions of SVR4 and compatible systems provide a facility called
17197 @samp{/proc} that can be used to examine the image of a running
17198 process using file-system subroutines. If @value{GDBN} is configured
17199 for an operating system with this facility, the command @code{info
17200 proc} is available to report information about the process running
17201 your program, or about any process running on your system. @code{info
17202 proc} works only on SVR4 systems that include the @code{procfs} code.
17203 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17204 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17210 @itemx info proc @var{process-id}
17211 Summarize available information about any running process. If a
17212 process ID is specified by @var{process-id}, display information about
17213 that process; otherwise display information about the program being
17214 debugged. The summary includes the debugged process ID, the command
17215 line used to invoke it, its current working directory, and its
17216 executable file's absolute file name.
17218 On some systems, @var{process-id} can be of the form
17219 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17220 within a process. If the optional @var{pid} part is missing, it means
17221 a thread from the process being debugged (the leading @samp{/} still
17222 needs to be present, or else @value{GDBN} will interpret the number as
17223 a process ID rather than a thread ID).
17225 @item info proc mappings
17226 @cindex memory address space mappings
17227 Report the memory address space ranges accessible in the program, with
17228 information on whether the process has read, write, or execute access
17229 rights to each range. On @sc{gnu}/Linux systems, each memory range
17230 includes the object file which is mapped to that range, instead of the
17231 memory access rights to that range.
17233 @item info proc stat
17234 @itemx info proc status
17235 @cindex process detailed status information
17236 These subcommands are specific to @sc{gnu}/Linux systems. They show
17237 the process-related information, including the user ID and group ID;
17238 how many threads are there in the process; its virtual memory usage;
17239 the signals that are pending, blocked, and ignored; its TTY; its
17240 consumption of system and user time; its stack size; its @samp{nice}
17241 value; etc. For more information, see the @samp{proc} man page
17242 (type @kbd{man 5 proc} from your shell prompt).
17244 @item info proc all
17245 Show all the information about the process described under all of the
17246 above @code{info proc} subcommands.
17249 @comment These sub-options of 'info proc' were not included when
17250 @comment procfs.c was re-written. Keep their descriptions around
17251 @comment against the day when someone finds the time to put them back in.
17252 @kindex info proc times
17253 @item info proc times
17254 Starting time, user CPU time, and system CPU time for your program and
17257 @kindex info proc id
17259 Report on the process IDs related to your program: its own process ID,
17260 the ID of its parent, the process group ID, and the session ID.
17263 @item set procfs-trace
17264 @kindex set procfs-trace
17265 @cindex @code{procfs} API calls
17266 This command enables and disables tracing of @code{procfs} API calls.
17268 @item show procfs-trace
17269 @kindex show procfs-trace
17270 Show the current state of @code{procfs} API call tracing.
17272 @item set procfs-file @var{file}
17273 @kindex set procfs-file
17274 Tell @value{GDBN} to write @code{procfs} API trace to the named
17275 @var{file}. @value{GDBN} appends the trace info to the previous
17276 contents of the file. The default is to display the trace on the
17279 @item show procfs-file
17280 @kindex show procfs-file
17281 Show the file to which @code{procfs} API trace is written.
17283 @item proc-trace-entry
17284 @itemx proc-trace-exit
17285 @itemx proc-untrace-entry
17286 @itemx proc-untrace-exit
17287 @kindex proc-trace-entry
17288 @kindex proc-trace-exit
17289 @kindex proc-untrace-entry
17290 @kindex proc-untrace-exit
17291 These commands enable and disable tracing of entries into and exits
17292 from the @code{syscall} interface.
17295 @kindex info pidlist
17296 @cindex process list, QNX Neutrino
17297 For QNX Neutrino only, this command displays the list of all the
17298 processes and all the threads within each process.
17301 @kindex info meminfo
17302 @cindex mapinfo list, QNX Neutrino
17303 For QNX Neutrino only, this command displays the list of all mapinfos.
17307 @subsection Features for Debugging @sc{djgpp} Programs
17308 @cindex @sc{djgpp} debugging
17309 @cindex native @sc{djgpp} debugging
17310 @cindex MS-DOS-specific commands
17313 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17314 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17315 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17316 top of real-mode DOS systems and their emulations.
17318 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17319 defines a few commands specific to the @sc{djgpp} port. This
17320 subsection describes those commands.
17325 This is a prefix of @sc{djgpp}-specific commands which print
17326 information about the target system and important OS structures.
17329 @cindex MS-DOS system info
17330 @cindex free memory information (MS-DOS)
17331 @item info dos sysinfo
17332 This command displays assorted information about the underlying
17333 platform: the CPU type and features, the OS version and flavor, the
17334 DPMI version, and the available conventional and DPMI memory.
17339 @cindex segment descriptor tables
17340 @cindex descriptor tables display
17342 @itemx info dos ldt
17343 @itemx info dos idt
17344 These 3 commands display entries from, respectively, Global, Local,
17345 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17346 tables are data structures which store a descriptor for each segment
17347 that is currently in use. The segment's selector is an index into a
17348 descriptor table; the table entry for that index holds the
17349 descriptor's base address and limit, and its attributes and access
17352 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17353 segment (used for both data and the stack), and a DOS segment (which
17354 allows access to DOS/BIOS data structures and absolute addresses in
17355 conventional memory). However, the DPMI host will usually define
17356 additional segments in order to support the DPMI environment.
17358 @cindex garbled pointers
17359 These commands allow to display entries from the descriptor tables.
17360 Without an argument, all entries from the specified table are
17361 displayed. An argument, which should be an integer expression, means
17362 display a single entry whose index is given by the argument. For
17363 example, here's a convenient way to display information about the
17364 debugged program's data segment:
17367 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17368 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17372 This comes in handy when you want to see whether a pointer is outside
17373 the data segment's limit (i.e.@: @dfn{garbled}).
17375 @cindex page tables display (MS-DOS)
17377 @itemx info dos pte
17378 These two commands display entries from, respectively, the Page
17379 Directory and the Page Tables. Page Directories and Page Tables are
17380 data structures which control how virtual memory addresses are mapped
17381 into physical addresses. A Page Table includes an entry for every
17382 page of memory that is mapped into the program's address space; there
17383 may be several Page Tables, each one holding up to 4096 entries. A
17384 Page Directory has up to 4096 entries, one each for every Page Table
17385 that is currently in use.
17387 Without an argument, @kbd{info dos pde} displays the entire Page
17388 Directory, and @kbd{info dos pte} displays all the entries in all of
17389 the Page Tables. An argument, an integer expression, given to the
17390 @kbd{info dos pde} command means display only that entry from the Page
17391 Directory table. An argument given to the @kbd{info dos pte} command
17392 means display entries from a single Page Table, the one pointed to by
17393 the specified entry in the Page Directory.
17395 @cindex direct memory access (DMA) on MS-DOS
17396 These commands are useful when your program uses @dfn{DMA} (Direct
17397 Memory Access), which needs physical addresses to program the DMA
17400 These commands are supported only with some DPMI servers.
17402 @cindex physical address from linear address
17403 @item info dos address-pte @var{addr}
17404 This command displays the Page Table entry for a specified linear
17405 address. The argument @var{addr} is a linear address which should
17406 already have the appropriate segment's base address added to it,
17407 because this command accepts addresses which may belong to @emph{any}
17408 segment. For example, here's how to display the Page Table entry for
17409 the page where a variable @code{i} is stored:
17412 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17413 @exdent @code{Page Table entry for address 0x11a00d30:}
17414 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17418 This says that @code{i} is stored at offset @code{0xd30} from the page
17419 whose physical base address is @code{0x02698000}, and shows all the
17420 attributes of that page.
17422 Note that you must cast the addresses of variables to a @code{char *},
17423 since otherwise the value of @code{__djgpp_base_address}, the base
17424 address of all variables and functions in a @sc{djgpp} program, will
17425 be added using the rules of C pointer arithmetics: if @code{i} is
17426 declared an @code{int}, @value{GDBN} will add 4 times the value of
17427 @code{__djgpp_base_address} to the address of @code{i}.
17429 Here's another example, it displays the Page Table entry for the
17433 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17434 @exdent @code{Page Table entry for address 0x29110:}
17435 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17439 (The @code{+ 3} offset is because the transfer buffer's address is the
17440 3rd member of the @code{_go32_info_block} structure.) The output
17441 clearly shows that this DPMI server maps the addresses in conventional
17442 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17443 linear (@code{0x29110}) addresses are identical.
17445 This command is supported only with some DPMI servers.
17448 @cindex DOS serial data link, remote debugging
17449 In addition to native debugging, the DJGPP port supports remote
17450 debugging via a serial data link. The following commands are specific
17451 to remote serial debugging in the DJGPP port of @value{GDBN}.
17454 @kindex set com1base
17455 @kindex set com1irq
17456 @kindex set com2base
17457 @kindex set com2irq
17458 @kindex set com3base
17459 @kindex set com3irq
17460 @kindex set com4base
17461 @kindex set com4irq
17462 @item set com1base @var{addr}
17463 This command sets the base I/O port address of the @file{COM1} serial
17466 @item set com1irq @var{irq}
17467 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17468 for the @file{COM1} serial port.
17470 There are similar commands @samp{set com2base}, @samp{set com3irq},
17471 etc.@: for setting the port address and the @code{IRQ} lines for the
17474 @kindex show com1base
17475 @kindex show com1irq
17476 @kindex show com2base
17477 @kindex show com2irq
17478 @kindex show com3base
17479 @kindex show com3irq
17480 @kindex show com4base
17481 @kindex show com4irq
17482 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17483 display the current settings of the base address and the @code{IRQ}
17484 lines used by the COM ports.
17487 @kindex info serial
17488 @cindex DOS serial port status
17489 This command prints the status of the 4 DOS serial ports. For each
17490 port, it prints whether it's active or not, its I/O base address and
17491 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17492 counts of various errors encountered so far.
17496 @node Cygwin Native
17497 @subsection Features for Debugging MS Windows PE Executables
17498 @cindex MS Windows debugging
17499 @cindex native Cygwin debugging
17500 @cindex Cygwin-specific commands
17502 @value{GDBN} supports native debugging of MS Windows programs, including
17503 DLLs with and without symbolic debugging information.
17505 @cindex Ctrl-BREAK, MS-Windows
17506 @cindex interrupt debuggee on MS-Windows
17507 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17508 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17509 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17510 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17511 sequence, which can be used to interrupt the debuggee even if it
17514 There are various additional Cygwin-specific commands, described in
17515 this section. Working with DLLs that have no debugging symbols is
17516 described in @ref{Non-debug DLL Symbols}.
17521 This is a prefix of MS Windows-specific commands which print
17522 information about the target system and important OS structures.
17524 @item info w32 selector
17525 This command displays information returned by
17526 the Win32 API @code{GetThreadSelectorEntry} function.
17527 It takes an optional argument that is evaluated to
17528 a long value to give the information about this given selector.
17529 Without argument, this command displays information
17530 about the six segment registers.
17532 @item info w32 thread-information-block
17533 This command displays thread specific information stored in the
17534 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17535 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17539 This is a Cygwin-specific alias of @code{info shared}.
17541 @kindex dll-symbols
17543 This command loads symbols from a dll similarly to
17544 add-sym command but without the need to specify a base address.
17546 @kindex set cygwin-exceptions
17547 @cindex debugging the Cygwin DLL
17548 @cindex Cygwin DLL, debugging
17549 @item set cygwin-exceptions @var{mode}
17550 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17551 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17552 @value{GDBN} will delay recognition of exceptions, and may ignore some
17553 exceptions which seem to be caused by internal Cygwin DLL
17554 ``bookkeeping''. This option is meant primarily for debugging the
17555 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17556 @value{GDBN} users with false @code{SIGSEGV} signals.
17558 @kindex show cygwin-exceptions
17559 @item show cygwin-exceptions
17560 Displays whether @value{GDBN} will break on exceptions that happen
17561 inside the Cygwin DLL itself.
17563 @kindex set new-console
17564 @item set new-console @var{mode}
17565 If @var{mode} is @code{on} the debuggee will
17566 be started in a new console on next start.
17567 If @var{mode} is @code{off}, the debuggee will
17568 be started in the same console as the debugger.
17570 @kindex show new-console
17571 @item show new-console
17572 Displays whether a new console is used
17573 when the debuggee is started.
17575 @kindex set new-group
17576 @item set new-group @var{mode}
17577 This boolean value controls whether the debuggee should
17578 start a new group or stay in the same group as the debugger.
17579 This affects the way the Windows OS handles
17582 @kindex show new-group
17583 @item show new-group
17584 Displays current value of new-group boolean.
17586 @kindex set debugevents
17587 @item set debugevents
17588 This boolean value adds debug output concerning kernel events related
17589 to the debuggee seen by the debugger. This includes events that
17590 signal thread and process creation and exit, DLL loading and
17591 unloading, console interrupts, and debugging messages produced by the
17592 Windows @code{OutputDebugString} API call.
17594 @kindex set debugexec
17595 @item set debugexec
17596 This boolean value adds debug output concerning execute events
17597 (such as resume thread) seen by the debugger.
17599 @kindex set debugexceptions
17600 @item set debugexceptions
17601 This boolean value adds debug output concerning exceptions in the
17602 debuggee seen by the debugger.
17604 @kindex set debugmemory
17605 @item set debugmemory
17606 This boolean value adds debug output concerning debuggee memory reads
17607 and writes by the debugger.
17611 This boolean values specifies whether the debuggee is called
17612 via a shell or directly (default value is on).
17616 Displays if the debuggee will be started with a shell.
17621 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17624 @node Non-debug DLL Symbols
17625 @subsubsection Support for DLLs without Debugging Symbols
17626 @cindex DLLs with no debugging symbols
17627 @cindex Minimal symbols and DLLs
17629 Very often on windows, some of the DLLs that your program relies on do
17630 not include symbolic debugging information (for example,
17631 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17632 symbols in a DLL, it relies on the minimal amount of symbolic
17633 information contained in the DLL's export table. This section
17634 describes working with such symbols, known internally to @value{GDBN} as
17635 ``minimal symbols''.
17637 Note that before the debugged program has started execution, no DLLs
17638 will have been loaded. The easiest way around this problem is simply to
17639 start the program --- either by setting a breakpoint or letting the
17640 program run once to completion. It is also possible to force
17641 @value{GDBN} to load a particular DLL before starting the executable ---
17642 see the shared library information in @ref{Files}, or the
17643 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17644 explicitly loading symbols from a DLL with no debugging information will
17645 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17646 which may adversely affect symbol lookup performance.
17648 @subsubsection DLL Name Prefixes
17650 In keeping with the naming conventions used by the Microsoft debugging
17651 tools, DLL export symbols are made available with a prefix based on the
17652 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17653 also entered into the symbol table, so @code{CreateFileA} is often
17654 sufficient. In some cases there will be name clashes within a program
17655 (particularly if the executable itself includes full debugging symbols)
17656 necessitating the use of the fully qualified name when referring to the
17657 contents of the DLL. Use single-quotes around the name to avoid the
17658 exclamation mark (``!'') being interpreted as a language operator.
17660 Note that the internal name of the DLL may be all upper-case, even
17661 though the file name of the DLL is lower-case, or vice-versa. Since
17662 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17663 some confusion. If in doubt, try the @code{info functions} and
17664 @code{info variables} commands or even @code{maint print msymbols}
17665 (@pxref{Symbols}). Here's an example:
17668 (@value{GDBP}) info function CreateFileA
17669 All functions matching regular expression "CreateFileA":
17671 Non-debugging symbols:
17672 0x77e885f4 CreateFileA
17673 0x77e885f4 KERNEL32!CreateFileA
17677 (@value{GDBP}) info function !
17678 All functions matching regular expression "!":
17680 Non-debugging symbols:
17681 0x6100114c cygwin1!__assert
17682 0x61004034 cygwin1!_dll_crt0@@0
17683 0x61004240 cygwin1!dll_crt0(per_process *)
17687 @subsubsection Working with Minimal Symbols
17689 Symbols extracted from a DLL's export table do not contain very much
17690 type information. All that @value{GDBN} can do is guess whether a symbol
17691 refers to a function or variable depending on the linker section that
17692 contains the symbol. Also note that the actual contents of the memory
17693 contained in a DLL are not available unless the program is running. This
17694 means that you cannot examine the contents of a variable or disassemble
17695 a function within a DLL without a running program.
17697 Variables are generally treated as pointers and dereferenced
17698 automatically. For this reason, it is often necessary to prefix a
17699 variable name with the address-of operator (``&'') and provide explicit
17700 type information in the command. Here's an example of the type of
17704 (@value{GDBP}) print 'cygwin1!__argv'
17709 (@value{GDBP}) x 'cygwin1!__argv'
17710 0x10021610: "\230y\""
17713 And two possible solutions:
17716 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17717 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17721 (@value{GDBP}) x/2x &'cygwin1!__argv'
17722 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17723 (@value{GDBP}) x/x 0x10021608
17724 0x10021608: 0x0022fd98
17725 (@value{GDBP}) x/s 0x0022fd98
17726 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17729 Setting a break point within a DLL is possible even before the program
17730 starts execution. However, under these circumstances, @value{GDBN} can't
17731 examine the initial instructions of the function in order to skip the
17732 function's frame set-up code. You can work around this by using ``*&''
17733 to set the breakpoint at a raw memory address:
17736 (@value{GDBP}) break *&'python22!PyOS_Readline'
17737 Breakpoint 1 at 0x1e04eff0
17740 The author of these extensions is not entirely convinced that setting a
17741 break point within a shared DLL like @file{kernel32.dll} is completely
17745 @subsection Commands Specific to @sc{gnu} Hurd Systems
17746 @cindex @sc{gnu} Hurd debugging
17748 This subsection describes @value{GDBN} commands specific to the
17749 @sc{gnu} Hurd native debugging.
17754 @kindex set signals@r{, Hurd command}
17755 @kindex set sigs@r{, Hurd command}
17756 This command toggles the state of inferior signal interception by
17757 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17758 affected by this command. @code{sigs} is a shorthand alias for
17763 @kindex show signals@r{, Hurd command}
17764 @kindex show sigs@r{, Hurd command}
17765 Show the current state of intercepting inferior's signals.
17767 @item set signal-thread
17768 @itemx set sigthread
17769 @kindex set signal-thread
17770 @kindex set sigthread
17771 This command tells @value{GDBN} which thread is the @code{libc} signal
17772 thread. That thread is run when a signal is delivered to a running
17773 process. @code{set sigthread} is the shorthand alias of @code{set
17776 @item show signal-thread
17777 @itemx show sigthread
17778 @kindex show signal-thread
17779 @kindex show sigthread
17780 These two commands show which thread will run when the inferior is
17781 delivered a signal.
17784 @kindex set stopped@r{, Hurd command}
17785 This commands tells @value{GDBN} that the inferior process is stopped,
17786 as with the @code{SIGSTOP} signal. The stopped process can be
17787 continued by delivering a signal to it.
17790 @kindex show stopped@r{, Hurd command}
17791 This command shows whether @value{GDBN} thinks the debuggee is
17794 @item set exceptions
17795 @kindex set exceptions@r{, Hurd command}
17796 Use this command to turn off trapping of exceptions in the inferior.
17797 When exception trapping is off, neither breakpoints nor
17798 single-stepping will work. To restore the default, set exception
17801 @item show exceptions
17802 @kindex show exceptions@r{, Hurd command}
17803 Show the current state of trapping exceptions in the inferior.
17805 @item set task pause
17806 @kindex set task@r{, Hurd commands}
17807 @cindex task attributes (@sc{gnu} Hurd)
17808 @cindex pause current task (@sc{gnu} Hurd)
17809 This command toggles task suspension when @value{GDBN} has control.
17810 Setting it to on takes effect immediately, and the task is suspended
17811 whenever @value{GDBN} gets control. Setting it to off will take
17812 effect the next time the inferior is continued. If this option is set
17813 to off, you can use @code{set thread default pause on} or @code{set
17814 thread pause on} (see below) to pause individual threads.
17816 @item show task pause
17817 @kindex show task@r{, Hurd commands}
17818 Show the current state of task suspension.
17820 @item set task detach-suspend-count
17821 @cindex task suspend count
17822 @cindex detach from task, @sc{gnu} Hurd
17823 This command sets the suspend count the task will be left with when
17824 @value{GDBN} detaches from it.
17826 @item show task detach-suspend-count
17827 Show the suspend count the task will be left with when detaching.
17829 @item set task exception-port
17830 @itemx set task excp
17831 @cindex task exception port, @sc{gnu} Hurd
17832 This command sets the task exception port to which @value{GDBN} will
17833 forward exceptions. The argument should be the value of the @dfn{send
17834 rights} of the task. @code{set task excp} is a shorthand alias.
17836 @item set noninvasive
17837 @cindex noninvasive task options
17838 This command switches @value{GDBN} to a mode that is the least
17839 invasive as far as interfering with the inferior is concerned. This
17840 is the same as using @code{set task pause}, @code{set exceptions}, and
17841 @code{set signals} to values opposite to the defaults.
17843 @item info send-rights
17844 @itemx info receive-rights
17845 @itemx info port-rights
17846 @itemx info port-sets
17847 @itemx info dead-names
17850 @cindex send rights, @sc{gnu} Hurd
17851 @cindex receive rights, @sc{gnu} Hurd
17852 @cindex port rights, @sc{gnu} Hurd
17853 @cindex port sets, @sc{gnu} Hurd
17854 @cindex dead names, @sc{gnu} Hurd
17855 These commands display information about, respectively, send rights,
17856 receive rights, port rights, port sets, and dead names of a task.
17857 There are also shorthand aliases: @code{info ports} for @code{info
17858 port-rights} and @code{info psets} for @code{info port-sets}.
17860 @item set thread pause
17861 @kindex set thread@r{, Hurd command}
17862 @cindex thread properties, @sc{gnu} Hurd
17863 @cindex pause current thread (@sc{gnu} Hurd)
17864 This command toggles current thread suspension when @value{GDBN} has
17865 control. Setting it to on takes effect immediately, and the current
17866 thread is suspended whenever @value{GDBN} gets control. Setting it to
17867 off will take effect the next time the inferior is continued.
17868 Normally, this command has no effect, since when @value{GDBN} has
17869 control, the whole task is suspended. However, if you used @code{set
17870 task pause off} (see above), this command comes in handy to suspend
17871 only the current thread.
17873 @item show thread pause
17874 @kindex show thread@r{, Hurd command}
17875 This command shows the state of current thread suspension.
17877 @item set thread run
17878 This command sets whether the current thread is allowed to run.
17880 @item show thread run
17881 Show whether the current thread is allowed to run.
17883 @item set thread detach-suspend-count
17884 @cindex thread suspend count, @sc{gnu} Hurd
17885 @cindex detach from thread, @sc{gnu} Hurd
17886 This command sets the suspend count @value{GDBN} will leave on a
17887 thread when detaching. This number is relative to the suspend count
17888 found by @value{GDBN} when it notices the thread; use @code{set thread
17889 takeover-suspend-count} to force it to an absolute value.
17891 @item show thread detach-suspend-count
17892 Show the suspend count @value{GDBN} will leave on the thread when
17895 @item set thread exception-port
17896 @itemx set thread excp
17897 Set the thread exception port to which to forward exceptions. This
17898 overrides the port set by @code{set task exception-port} (see above).
17899 @code{set thread excp} is the shorthand alias.
17901 @item set thread takeover-suspend-count
17902 Normally, @value{GDBN}'s thread suspend counts are relative to the
17903 value @value{GDBN} finds when it notices each thread. This command
17904 changes the suspend counts to be absolute instead.
17906 @item set thread default
17907 @itemx show thread default
17908 @cindex thread default settings, @sc{gnu} Hurd
17909 Each of the above @code{set thread} commands has a @code{set thread
17910 default} counterpart (e.g., @code{set thread default pause}, @code{set
17911 thread default exception-port}, etc.). The @code{thread default}
17912 variety of commands sets the default thread properties for all
17913 threads; you can then change the properties of individual threads with
17914 the non-default commands.
17919 @subsection QNX Neutrino
17920 @cindex QNX Neutrino
17922 @value{GDBN} provides the following commands specific to the QNX
17926 @item set debug nto-debug
17927 @kindex set debug nto-debug
17928 When set to on, enables debugging messages specific to the QNX
17931 @item show debug nto-debug
17932 @kindex show debug nto-debug
17933 Show the current state of QNX Neutrino messages.
17940 @value{GDBN} provides the following commands specific to the Darwin target:
17943 @item set debug darwin @var{num}
17944 @kindex set debug darwin
17945 When set to a non zero value, enables debugging messages specific to
17946 the Darwin support. Higher values produce more verbose output.
17948 @item show debug darwin
17949 @kindex show debug darwin
17950 Show the current state of Darwin messages.
17952 @item set debug mach-o @var{num}
17953 @kindex set debug mach-o
17954 When set to a non zero value, enables debugging messages while
17955 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17956 file format used on Darwin for object and executable files.) Higher
17957 values produce more verbose output. This is a command to diagnose
17958 problems internal to @value{GDBN} and should not be needed in normal
17961 @item show debug mach-o
17962 @kindex show debug mach-o
17963 Show the current state of Mach-O file messages.
17965 @item set mach-exceptions on
17966 @itemx set mach-exceptions off
17967 @kindex set mach-exceptions
17968 On Darwin, faults are first reported as a Mach exception and are then
17969 mapped to a Posix signal. Use this command to turn on trapping of
17970 Mach exceptions in the inferior. This might be sometimes useful to
17971 better understand the cause of a fault. The default is off.
17973 @item show mach-exceptions
17974 @kindex show mach-exceptions
17975 Show the current state of exceptions trapping.
17980 @section Embedded Operating Systems
17982 This section describes configurations involving the debugging of
17983 embedded operating systems that are available for several different
17987 * VxWorks:: Using @value{GDBN} with VxWorks
17990 @value{GDBN} includes the ability to debug programs running on
17991 various real-time operating systems.
17994 @subsection Using @value{GDBN} with VxWorks
18000 @kindex target vxworks
18001 @item target vxworks @var{machinename}
18002 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18003 is the target system's machine name or IP address.
18007 On VxWorks, @code{load} links @var{filename} dynamically on the
18008 current target system as well as adding its symbols in @value{GDBN}.
18010 @value{GDBN} enables developers to spawn and debug tasks running on networked
18011 VxWorks targets from a Unix host. Already-running tasks spawned from
18012 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18013 both the Unix host and on the VxWorks target. The program
18014 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18015 installed with the name @code{vxgdb}, to distinguish it from a
18016 @value{GDBN} for debugging programs on the host itself.)
18019 @item VxWorks-timeout @var{args}
18020 @kindex vxworks-timeout
18021 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18022 This option is set by the user, and @var{args} represents the number of
18023 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18024 your VxWorks target is a slow software simulator or is on the far side
18025 of a thin network line.
18028 The following information on connecting to VxWorks was current when
18029 this manual was produced; newer releases of VxWorks may use revised
18032 @findex INCLUDE_RDB
18033 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18034 to include the remote debugging interface routines in the VxWorks
18035 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18036 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18037 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18038 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18039 information on configuring and remaking VxWorks, see the manufacturer's
18041 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18043 Once you have included @file{rdb.a} in your VxWorks system image and set
18044 your Unix execution search path to find @value{GDBN}, you are ready to
18045 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18046 @code{vxgdb}, depending on your installation).
18048 @value{GDBN} comes up showing the prompt:
18055 * VxWorks Connection:: Connecting to VxWorks
18056 * VxWorks Download:: VxWorks download
18057 * VxWorks Attach:: Running tasks
18060 @node VxWorks Connection
18061 @subsubsection Connecting to VxWorks
18063 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18064 network. To connect to a target whose host name is ``@code{tt}'', type:
18067 (vxgdb) target vxworks tt
18071 @value{GDBN} displays messages like these:
18074 Attaching remote machine across net...
18079 @value{GDBN} then attempts to read the symbol tables of any object modules
18080 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18081 these files by searching the directories listed in the command search
18082 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18083 to find an object file, it displays a message such as:
18086 prog.o: No such file or directory.
18089 When this happens, add the appropriate directory to the search path with
18090 the @value{GDBN} command @code{path}, and execute the @code{target}
18093 @node VxWorks Download
18094 @subsubsection VxWorks Download
18096 @cindex download to VxWorks
18097 If you have connected to the VxWorks target and you want to debug an
18098 object that has not yet been loaded, you can use the @value{GDBN}
18099 @code{load} command to download a file from Unix to VxWorks
18100 incrementally. The object file given as an argument to the @code{load}
18101 command is actually opened twice: first by the VxWorks target in order
18102 to download the code, then by @value{GDBN} in order to read the symbol
18103 table. This can lead to problems if the current working directories on
18104 the two systems differ. If both systems have NFS mounted the same
18105 filesystems, you can avoid these problems by using absolute paths.
18106 Otherwise, it is simplest to set the working directory on both systems
18107 to the directory in which the object file resides, and then to reference
18108 the file by its name, without any path. For instance, a program
18109 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18110 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18111 program, type this on VxWorks:
18114 -> cd "@var{vxpath}/vw/demo/rdb"
18118 Then, in @value{GDBN}, type:
18121 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18122 (vxgdb) load prog.o
18125 @value{GDBN} displays a response similar to this:
18128 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18131 You can also use the @code{load} command to reload an object module
18132 after editing and recompiling the corresponding source file. Note that
18133 this makes @value{GDBN} delete all currently-defined breakpoints,
18134 auto-displays, and convenience variables, and to clear the value
18135 history. (This is necessary in order to preserve the integrity of
18136 debugger's data structures that reference the target system's symbol
18139 @node VxWorks Attach
18140 @subsubsection Running Tasks
18142 @cindex running VxWorks tasks
18143 You can also attach to an existing task using the @code{attach} command as
18147 (vxgdb) attach @var{task}
18151 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18152 or suspended when you attach to it. Running tasks are suspended at
18153 the time of attachment.
18155 @node Embedded Processors
18156 @section Embedded Processors
18158 This section goes into details specific to particular embedded
18161 @cindex send command to simulator
18162 Whenever a specific embedded processor has a simulator, @value{GDBN}
18163 allows to send an arbitrary command to the simulator.
18166 @item sim @var{command}
18167 @kindex sim@r{, a command}
18168 Send an arbitrary @var{command} string to the simulator. Consult the
18169 documentation for the specific simulator in use for information about
18170 acceptable commands.
18176 * M32R/D:: Renesas M32R/D
18177 * M68K:: Motorola M68K
18178 * MicroBlaze:: Xilinx MicroBlaze
18179 * MIPS Embedded:: MIPS Embedded
18180 * OpenRISC 1000:: OpenRisc 1000
18181 * PA:: HP PA Embedded
18182 * PowerPC Embedded:: PowerPC Embedded
18183 * Sparclet:: Tsqware Sparclet
18184 * Sparclite:: Fujitsu Sparclite
18185 * Z8000:: Zilog Z8000
18188 * Super-H:: Renesas Super-H
18197 @item target rdi @var{dev}
18198 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18199 use this target to communicate with both boards running the Angel
18200 monitor, or with the EmbeddedICE JTAG debug device.
18203 @item target rdp @var{dev}
18208 @value{GDBN} provides the following ARM-specific commands:
18211 @item set arm disassembler
18213 This commands selects from a list of disassembly styles. The
18214 @code{"std"} style is the standard style.
18216 @item show arm disassembler
18218 Show the current disassembly style.
18220 @item set arm apcs32
18221 @cindex ARM 32-bit mode
18222 This command toggles ARM operation mode between 32-bit and 26-bit.
18224 @item show arm apcs32
18225 Display the current usage of the ARM 32-bit mode.
18227 @item set arm fpu @var{fputype}
18228 This command sets the ARM floating-point unit (FPU) type. The
18229 argument @var{fputype} can be one of these:
18233 Determine the FPU type by querying the OS ABI.
18235 Software FPU, with mixed-endian doubles on little-endian ARM
18238 GCC-compiled FPA co-processor.
18240 Software FPU with pure-endian doubles.
18246 Show the current type of the FPU.
18249 This command forces @value{GDBN} to use the specified ABI.
18252 Show the currently used ABI.
18254 @item set arm fallback-mode (arm|thumb|auto)
18255 @value{GDBN} uses the symbol table, when available, to determine
18256 whether instructions are ARM or Thumb. This command controls
18257 @value{GDBN}'s default behavior when the symbol table is not
18258 available. The default is @samp{auto}, which causes @value{GDBN} to
18259 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18262 @item show arm fallback-mode
18263 Show the current fallback instruction mode.
18265 @item set arm force-mode (arm|thumb|auto)
18266 This command overrides use of the symbol table to determine whether
18267 instructions are ARM or Thumb. The default is @samp{auto}, which
18268 causes @value{GDBN} to use the symbol table and then the setting
18269 of @samp{set arm fallback-mode}.
18271 @item show arm force-mode
18272 Show the current forced instruction mode.
18274 @item set debug arm
18275 Toggle whether to display ARM-specific debugging messages from the ARM
18276 target support subsystem.
18278 @item show debug arm
18279 Show whether ARM-specific debugging messages are enabled.
18282 The following commands are available when an ARM target is debugged
18283 using the RDI interface:
18286 @item rdilogfile @r{[}@var{file}@r{]}
18288 @cindex ADP (Angel Debugger Protocol) logging
18289 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18290 With an argument, sets the log file to the specified @var{file}. With
18291 no argument, show the current log file name. The default log file is
18294 @item rdilogenable @r{[}@var{arg}@r{]}
18295 @kindex rdilogenable
18296 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18297 enables logging, with an argument 0 or @code{"no"} disables it. With
18298 no arguments displays the current setting. When logging is enabled,
18299 ADP packets exchanged between @value{GDBN} and the RDI target device
18300 are logged to a file.
18302 @item set rdiromatzero
18303 @kindex set rdiromatzero
18304 @cindex ROM at zero address, RDI
18305 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18306 vector catching is disabled, so that zero address can be used. If off
18307 (the default), vector catching is enabled. For this command to take
18308 effect, it needs to be invoked prior to the @code{target rdi} command.
18310 @item show rdiromatzero
18311 @kindex show rdiromatzero
18312 Show the current setting of ROM at zero address.
18314 @item set rdiheartbeat
18315 @kindex set rdiheartbeat
18316 @cindex RDI heartbeat
18317 Enable or disable RDI heartbeat packets. It is not recommended to
18318 turn on this option, since it confuses ARM and EPI JTAG interface, as
18319 well as the Angel monitor.
18321 @item show rdiheartbeat
18322 @kindex show rdiheartbeat
18323 Show the setting of RDI heartbeat packets.
18327 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18328 The @value{GDBN} ARM simulator accepts the following optional arguments.
18331 @item --swi-support=@var{type}
18332 Tell the simulator which SWI interfaces to support.
18333 @var{type} may be a comma separated list of the following values.
18334 The default value is @code{all}.
18347 @subsection Renesas M32R/D and M32R/SDI
18350 @kindex target m32r
18351 @item target m32r @var{dev}
18352 Renesas M32R/D ROM monitor.
18354 @kindex target m32rsdi
18355 @item target m32rsdi @var{dev}
18356 Renesas M32R SDI server, connected via parallel port to the board.
18359 The following @value{GDBN} commands are specific to the M32R monitor:
18362 @item set download-path @var{path}
18363 @kindex set download-path
18364 @cindex find downloadable @sc{srec} files (M32R)
18365 Set the default path for finding downloadable @sc{srec} files.
18367 @item show download-path
18368 @kindex show download-path
18369 Show the default path for downloadable @sc{srec} files.
18371 @item set board-address @var{addr}
18372 @kindex set board-address
18373 @cindex M32-EVA target board address
18374 Set the IP address for the M32R-EVA target board.
18376 @item show board-address
18377 @kindex show board-address
18378 Show the current IP address of the target board.
18380 @item set server-address @var{addr}
18381 @kindex set server-address
18382 @cindex download server address (M32R)
18383 Set the IP address for the download server, which is the @value{GDBN}'s
18386 @item show server-address
18387 @kindex show server-address
18388 Display the IP address of the download server.
18390 @item upload @r{[}@var{file}@r{]}
18391 @kindex upload@r{, M32R}
18392 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18393 upload capability. If no @var{file} argument is given, the current
18394 executable file is uploaded.
18396 @item tload @r{[}@var{file}@r{]}
18397 @kindex tload@r{, M32R}
18398 Test the @code{upload} command.
18401 The following commands are available for M32R/SDI:
18406 @cindex reset SDI connection, M32R
18407 This command resets the SDI connection.
18411 This command shows the SDI connection status.
18414 @kindex debug_chaos
18415 @cindex M32R/Chaos debugging
18416 Instructs the remote that M32R/Chaos debugging is to be used.
18418 @item use_debug_dma
18419 @kindex use_debug_dma
18420 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18423 @kindex use_mon_code
18424 Instructs the remote to use the MON_CODE method of accessing memory.
18427 @kindex use_ib_break
18428 Instructs the remote to set breakpoints by IB break.
18430 @item use_dbt_break
18431 @kindex use_dbt_break
18432 Instructs the remote to set breakpoints by DBT.
18438 The Motorola m68k configuration includes ColdFire support, and a
18439 target command for the following ROM monitor.
18443 @kindex target dbug
18444 @item target dbug @var{dev}
18445 dBUG ROM monitor for Motorola ColdFire.
18450 @subsection MicroBlaze
18451 @cindex Xilinx MicroBlaze
18452 @cindex XMD, Xilinx Microprocessor Debugger
18454 The MicroBlaze is a soft-core processor supported on various Xilinx
18455 FPGAs, such as Spartan or Virtex series. Boards with these processors
18456 usually have JTAG ports which connect to a host system running the Xilinx
18457 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18458 This host system is used to download the configuration bitstream to
18459 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18460 communicates with the target board using the JTAG interface and
18461 presents a @code{gdbserver} interface to the board. By default
18462 @code{xmd} uses port @code{1234}. (While it is possible to change
18463 this default port, it requires the use of undocumented @code{xmd}
18464 commands. Contact Xilinx support if you need to do this.)
18466 Use these GDB commands to connect to the MicroBlaze target processor.
18469 @item target remote :1234
18470 Use this command to connect to the target if you are running @value{GDBN}
18471 on the same system as @code{xmd}.
18473 @item target remote @var{xmd-host}:1234
18474 Use this command to connect to the target if it is connected to @code{xmd}
18475 running on a different system named @var{xmd-host}.
18478 Use this command to download a program to the MicroBlaze target.
18480 @item set debug microblaze @var{n}
18481 Enable MicroBlaze-specific debugging messages if non-zero.
18483 @item show debug microblaze @var{n}
18484 Show MicroBlaze-specific debugging level.
18487 @node MIPS Embedded
18488 @subsection MIPS Embedded
18490 @cindex MIPS boards
18491 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18492 MIPS board attached to a serial line. This is available when
18493 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18496 Use these @value{GDBN} commands to specify the connection to your target board:
18499 @item target mips @var{port}
18500 @kindex target mips @var{port}
18501 To run a program on the board, start up @code{@value{GDBP}} with the
18502 name of your program as the argument. To connect to the board, use the
18503 command @samp{target mips @var{port}}, where @var{port} is the name of
18504 the serial port connected to the board. If the program has not already
18505 been downloaded to the board, you may use the @code{load} command to
18506 download it. You can then use all the usual @value{GDBN} commands.
18508 For example, this sequence connects to the target board through a serial
18509 port, and loads and runs a program called @var{prog} through the
18513 host$ @value{GDBP} @var{prog}
18514 @value{GDBN} is free software and @dots{}
18515 (@value{GDBP}) target mips /dev/ttyb
18516 (@value{GDBP}) load @var{prog}
18520 @item target mips @var{hostname}:@var{portnumber}
18521 On some @value{GDBN} host configurations, you can specify a TCP
18522 connection (for instance, to a serial line managed by a terminal
18523 concentrator) instead of a serial port, using the syntax
18524 @samp{@var{hostname}:@var{portnumber}}.
18526 @item target pmon @var{port}
18527 @kindex target pmon @var{port}
18530 @item target ddb @var{port}
18531 @kindex target ddb @var{port}
18532 NEC's DDB variant of PMON for Vr4300.
18534 @item target lsi @var{port}
18535 @kindex target lsi @var{port}
18536 LSI variant of PMON.
18538 @kindex target r3900
18539 @item target r3900 @var{dev}
18540 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18542 @kindex target array
18543 @item target array @var{dev}
18544 Array Tech LSI33K RAID controller board.
18550 @value{GDBN} also supports these special commands for MIPS targets:
18553 @item set mipsfpu double
18554 @itemx set mipsfpu single
18555 @itemx set mipsfpu none
18556 @itemx set mipsfpu auto
18557 @itemx show mipsfpu
18558 @kindex set mipsfpu
18559 @kindex show mipsfpu
18560 @cindex MIPS remote floating point
18561 @cindex floating point, MIPS remote
18562 If your target board does not support the MIPS floating point
18563 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18564 need this, you may wish to put the command in your @value{GDBN} init
18565 file). This tells @value{GDBN} how to find the return value of
18566 functions which return floating point values. It also allows
18567 @value{GDBN} to avoid saving the floating point registers when calling
18568 functions on the board. If you are using a floating point coprocessor
18569 with only single precision floating point support, as on the @sc{r4650}
18570 processor, use the command @samp{set mipsfpu single}. The default
18571 double precision floating point coprocessor may be selected using
18572 @samp{set mipsfpu double}.
18574 In previous versions the only choices were double precision or no
18575 floating point, so @samp{set mipsfpu on} will select double precision
18576 and @samp{set mipsfpu off} will select no floating point.
18578 As usual, you can inquire about the @code{mipsfpu} variable with
18579 @samp{show mipsfpu}.
18581 @item set timeout @var{seconds}
18582 @itemx set retransmit-timeout @var{seconds}
18583 @itemx show timeout
18584 @itemx show retransmit-timeout
18585 @cindex @code{timeout}, MIPS protocol
18586 @cindex @code{retransmit-timeout}, MIPS protocol
18587 @kindex set timeout
18588 @kindex show timeout
18589 @kindex set retransmit-timeout
18590 @kindex show retransmit-timeout
18591 You can control the timeout used while waiting for a packet, in the MIPS
18592 remote protocol, with the @code{set timeout @var{seconds}} command. The
18593 default is 5 seconds. Similarly, you can control the timeout used while
18594 waiting for an acknowledgment of a packet with the @code{set
18595 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18596 You can inspect both values with @code{show timeout} and @code{show
18597 retransmit-timeout}. (These commands are @emph{only} available when
18598 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18600 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18601 is waiting for your program to stop. In that case, @value{GDBN} waits
18602 forever because it has no way of knowing how long the program is going
18603 to run before stopping.
18605 @item set syn-garbage-limit @var{num}
18606 @kindex set syn-garbage-limit@r{, MIPS remote}
18607 @cindex synchronize with remote MIPS target
18608 Limit the maximum number of characters @value{GDBN} should ignore when
18609 it tries to synchronize with the remote target. The default is 10
18610 characters. Setting the limit to -1 means there's no limit.
18612 @item show syn-garbage-limit
18613 @kindex show syn-garbage-limit@r{, MIPS remote}
18614 Show the current limit on the number of characters to ignore when
18615 trying to synchronize with the remote system.
18617 @item set monitor-prompt @var{prompt}
18618 @kindex set monitor-prompt@r{, MIPS remote}
18619 @cindex remote monitor prompt
18620 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18621 remote monitor. The default depends on the target:
18631 @item show monitor-prompt
18632 @kindex show monitor-prompt@r{, MIPS remote}
18633 Show the current strings @value{GDBN} expects as the prompt from the
18636 @item set monitor-warnings
18637 @kindex set monitor-warnings@r{, MIPS remote}
18638 Enable or disable monitor warnings about hardware breakpoints. This
18639 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18640 display warning messages whose codes are returned by the @code{lsi}
18641 PMON monitor for breakpoint commands.
18643 @item show monitor-warnings
18644 @kindex show monitor-warnings@r{, MIPS remote}
18645 Show the current setting of printing monitor warnings.
18647 @item pmon @var{command}
18648 @kindex pmon@r{, MIPS remote}
18649 @cindex send PMON command
18650 This command allows sending an arbitrary @var{command} string to the
18651 monitor. The monitor must be in debug mode for this to work.
18654 @node OpenRISC 1000
18655 @subsection OpenRISC 1000
18656 @cindex OpenRISC 1000
18658 @cindex or1k boards
18659 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18660 about platform and commands.
18664 @kindex target jtag
18665 @item target jtag jtag://@var{host}:@var{port}
18667 Connects to remote JTAG server.
18668 JTAG remote server can be either an or1ksim or JTAG server,
18669 connected via parallel port to the board.
18671 Example: @code{target jtag jtag://localhost:9999}
18674 @item or1ksim @var{command}
18675 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18676 Simulator, proprietary commands can be executed.
18678 @kindex info or1k spr
18679 @item info or1k spr
18680 Displays spr groups.
18682 @item info or1k spr @var{group}
18683 @itemx info or1k spr @var{groupno}
18684 Displays register names in selected group.
18686 @item info or1k spr @var{group} @var{register}
18687 @itemx info or1k spr @var{register}
18688 @itemx info or1k spr @var{groupno} @var{registerno}
18689 @itemx info or1k spr @var{registerno}
18690 Shows information about specified spr register.
18693 @item spr @var{group} @var{register} @var{value}
18694 @itemx spr @var{register @var{value}}
18695 @itemx spr @var{groupno} @var{registerno @var{value}}
18696 @itemx spr @var{registerno @var{value}}
18697 Writes @var{value} to specified spr register.
18700 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18701 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18702 program execution and is thus much faster. Hardware breakpoints/watchpoint
18703 triggers can be set using:
18706 Load effective address/data
18708 Store effective address/data
18710 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18715 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18716 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18718 @code{htrace} commands:
18719 @cindex OpenRISC 1000 htrace
18722 @item hwatch @var{conditional}
18723 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18724 or Data. For example:
18726 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18728 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18732 Display information about current HW trace configuration.
18734 @item htrace trigger @var{conditional}
18735 Set starting criteria for HW trace.
18737 @item htrace qualifier @var{conditional}
18738 Set acquisition qualifier for HW trace.
18740 @item htrace stop @var{conditional}
18741 Set HW trace stopping criteria.
18743 @item htrace record [@var{data}]*
18744 Selects the data to be recorded, when qualifier is met and HW trace was
18747 @item htrace enable
18748 @itemx htrace disable
18749 Enables/disables the HW trace.
18751 @item htrace rewind [@var{filename}]
18752 Clears currently recorded trace data.
18754 If filename is specified, new trace file is made and any newly collected data
18755 will be written there.
18757 @item htrace print [@var{start} [@var{len}]]
18758 Prints trace buffer, using current record configuration.
18760 @item htrace mode continuous
18761 Set continuous trace mode.
18763 @item htrace mode suspend
18764 Set suspend trace mode.
18768 @node PowerPC Embedded
18769 @subsection PowerPC Embedded
18771 @cindex DVC register
18772 @value{GDBN} supports using the DVC (Data Value Compare) register to
18773 implement in hardware simple hardware watchpoint conditions of the form:
18776 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18777 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18780 The DVC register will be automatically used when @value{GDBN} detects
18781 such pattern in a condition expression, and the created watchpoint uses one
18782 debug register (either the @code{exact-watchpoints} option is on and the
18783 variable is scalar, or the variable has a length of one byte). This feature
18784 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18787 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18788 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18789 in which case watchpoints using only one debug register are created when
18790 watching variables of scalar types.
18792 You can create an artificial array to watch an arbitrary memory
18793 region using one of the following commands (@pxref{Expressions}):
18796 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18797 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18800 PowerPC embedded processors support masked watchpoints. See the discussion
18801 about the @code{mask} argument in @ref{Set Watchpoints}.
18803 @cindex ranged breakpoint
18804 PowerPC embedded processors support hardware accelerated
18805 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18806 the inferior whenever it executes an instruction at any address within
18807 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18808 use the @code{break-range} command.
18810 @value{GDBN} provides the following PowerPC-specific commands:
18813 @kindex break-range
18814 @item break-range @var{start-location}, @var{end-location}
18815 Set a breakpoint for an address range.
18816 @var{start-location} and @var{end-location} can specify a function name,
18817 a line number, an offset of lines from the current line or from the start
18818 location, or an address of an instruction (see @ref{Specify Location},
18819 for a list of all the possible ways to specify a @var{location}.)
18820 The breakpoint will stop execution of the inferior whenever it
18821 executes an instruction at any address within the specified range,
18822 (including @var{start-location} and @var{end-location}.)
18824 @kindex set powerpc
18825 @item set powerpc soft-float
18826 @itemx show powerpc soft-float
18827 Force @value{GDBN} to use (or not use) a software floating point calling
18828 convention. By default, @value{GDBN} selects the calling convention based
18829 on the selected architecture and the provided executable file.
18831 @item set powerpc vector-abi
18832 @itemx show powerpc vector-abi
18833 Force @value{GDBN} to use the specified calling convention for vector
18834 arguments and return values. The valid options are @samp{auto};
18835 @samp{generic}, to avoid vector registers even if they are present;
18836 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18837 registers. By default, @value{GDBN} selects the calling convention
18838 based on the selected architecture and the provided executable file.
18840 @item set powerpc exact-watchpoints
18841 @itemx show powerpc exact-watchpoints
18842 Allow @value{GDBN} to use only one debug register when watching a variable
18843 of scalar type, thus assuming that the variable is accessed through the
18844 address of its first byte.
18846 @kindex target dink32
18847 @item target dink32 @var{dev}
18848 DINK32 ROM monitor.
18850 @kindex target ppcbug
18851 @item target ppcbug @var{dev}
18852 @kindex target ppcbug1
18853 @item target ppcbug1 @var{dev}
18854 PPCBUG ROM monitor for PowerPC.
18857 @item target sds @var{dev}
18858 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18861 @cindex SDS protocol
18862 The following commands specific to the SDS protocol are supported
18866 @item set sdstimeout @var{nsec}
18867 @kindex set sdstimeout
18868 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18869 default is 2 seconds.
18871 @item show sdstimeout
18872 @kindex show sdstimeout
18873 Show the current value of the SDS timeout.
18875 @item sds @var{command}
18876 @kindex sds@r{, a command}
18877 Send the specified @var{command} string to the SDS monitor.
18882 @subsection HP PA Embedded
18886 @kindex target op50n
18887 @item target op50n @var{dev}
18888 OP50N monitor, running on an OKI HPPA board.
18890 @kindex target w89k
18891 @item target w89k @var{dev}
18892 W89K monitor, running on a Winbond HPPA board.
18897 @subsection Tsqware Sparclet
18901 @value{GDBN} enables developers to debug tasks running on
18902 Sparclet targets from a Unix host.
18903 @value{GDBN} uses code that runs on
18904 both the Unix host and on the Sparclet target. The program
18905 @code{@value{GDBP}} is installed and executed on the Unix host.
18908 @item remotetimeout @var{args}
18909 @kindex remotetimeout
18910 @value{GDBN} supports the option @code{remotetimeout}.
18911 This option is set by the user, and @var{args} represents the number of
18912 seconds @value{GDBN} waits for responses.
18915 @cindex compiling, on Sparclet
18916 When compiling for debugging, include the options @samp{-g} to get debug
18917 information and @samp{-Ttext} to relocate the program to where you wish to
18918 load it on the target. You may also want to add the options @samp{-n} or
18919 @samp{-N} in order to reduce the size of the sections. Example:
18922 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18925 You can use @code{objdump} to verify that the addresses are what you intended:
18928 sparclet-aout-objdump --headers --syms prog
18931 @cindex running, on Sparclet
18933 your Unix execution search path to find @value{GDBN}, you are ready to
18934 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18935 (or @code{sparclet-aout-gdb}, depending on your installation).
18937 @value{GDBN} comes up showing the prompt:
18944 * Sparclet File:: Setting the file to debug
18945 * Sparclet Connection:: Connecting to Sparclet
18946 * Sparclet Download:: Sparclet download
18947 * Sparclet Execution:: Running and debugging
18950 @node Sparclet File
18951 @subsubsection Setting File to Debug
18953 The @value{GDBN} command @code{file} lets you choose with program to debug.
18956 (gdbslet) file prog
18960 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18961 @value{GDBN} locates
18962 the file by searching the directories listed in the command search
18964 If the file was compiled with debug information (option @samp{-g}), source
18965 files will be searched as well.
18966 @value{GDBN} locates
18967 the source files by searching the directories listed in the directory search
18968 path (@pxref{Environment, ,Your Program's Environment}).
18970 to find a file, it displays a message such as:
18973 prog: No such file or directory.
18976 When this happens, add the appropriate directories to the search paths with
18977 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18978 @code{target} command again.
18980 @node Sparclet Connection
18981 @subsubsection Connecting to Sparclet
18983 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18984 To connect to a target on serial port ``@code{ttya}'', type:
18987 (gdbslet) target sparclet /dev/ttya
18988 Remote target sparclet connected to /dev/ttya
18989 main () at ../prog.c:3
18993 @value{GDBN} displays messages like these:
18999 @node Sparclet Download
19000 @subsubsection Sparclet Download
19002 @cindex download to Sparclet
19003 Once connected to the Sparclet target,
19004 you can use the @value{GDBN}
19005 @code{load} command to download the file from the host to the target.
19006 The file name and load offset should be given as arguments to the @code{load}
19008 Since the file format is aout, the program must be loaded to the starting
19009 address. You can use @code{objdump} to find out what this value is. The load
19010 offset is an offset which is added to the VMA (virtual memory address)
19011 of each of the file's sections.
19012 For instance, if the program
19013 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19014 and bss at 0x12010170, in @value{GDBN}, type:
19017 (gdbslet) load prog 0x12010000
19018 Loading section .text, size 0xdb0 vma 0x12010000
19021 If the code is loaded at a different address then what the program was linked
19022 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19023 to tell @value{GDBN} where to map the symbol table.
19025 @node Sparclet Execution
19026 @subsubsection Running and Debugging
19028 @cindex running and debugging Sparclet programs
19029 You can now begin debugging the task using @value{GDBN}'s execution control
19030 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19031 manual for the list of commands.
19035 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19037 Starting program: prog
19038 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19039 3 char *symarg = 0;
19041 4 char *execarg = "hello!";
19046 @subsection Fujitsu Sparclite
19050 @kindex target sparclite
19051 @item target sparclite @var{dev}
19052 Fujitsu sparclite boards, used only for the purpose of loading.
19053 You must use an additional command to debug the program.
19054 For example: target remote @var{dev} using @value{GDBN} standard
19060 @subsection Zilog Z8000
19063 @cindex simulator, Z8000
19064 @cindex Zilog Z8000 simulator
19066 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19069 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19070 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19071 segmented variant). The simulator recognizes which architecture is
19072 appropriate by inspecting the object code.
19075 @item target sim @var{args}
19077 @kindex target sim@r{, with Z8000}
19078 Debug programs on a simulated CPU. If the simulator supports setup
19079 options, specify them via @var{args}.
19083 After specifying this target, you can debug programs for the simulated
19084 CPU in the same style as programs for your host computer; use the
19085 @code{file} command to load a new program image, the @code{run} command
19086 to run your program, and so on.
19088 As well as making available all the usual machine registers
19089 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19090 additional items of information as specially named registers:
19095 Counts clock-ticks in the simulator.
19098 Counts instructions run in the simulator.
19101 Execution time in 60ths of a second.
19105 You can refer to these values in @value{GDBN} expressions with the usual
19106 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19107 conditional breakpoint that suspends only after at least 5000
19108 simulated clock ticks.
19111 @subsection Atmel AVR
19114 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19115 following AVR-specific commands:
19118 @item info io_registers
19119 @kindex info io_registers@r{, AVR}
19120 @cindex I/O registers (Atmel AVR)
19121 This command displays information about the AVR I/O registers. For
19122 each register, @value{GDBN} prints its number and value.
19129 When configured for debugging CRIS, @value{GDBN} provides the
19130 following CRIS-specific commands:
19133 @item set cris-version @var{ver}
19134 @cindex CRIS version
19135 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19136 The CRIS version affects register names and sizes. This command is useful in
19137 case autodetection of the CRIS version fails.
19139 @item show cris-version
19140 Show the current CRIS version.
19142 @item set cris-dwarf2-cfi
19143 @cindex DWARF-2 CFI and CRIS
19144 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19145 Change to @samp{off} when using @code{gcc-cris} whose version is below
19148 @item show cris-dwarf2-cfi
19149 Show the current state of using DWARF-2 CFI.
19151 @item set cris-mode @var{mode}
19153 Set the current CRIS mode to @var{mode}. It should only be changed when
19154 debugging in guru mode, in which case it should be set to
19155 @samp{guru} (the default is @samp{normal}).
19157 @item show cris-mode
19158 Show the current CRIS mode.
19162 @subsection Renesas Super-H
19165 For the Renesas Super-H processor, @value{GDBN} provides these
19170 @kindex regs@r{, Super-H}
19171 Show the values of all Super-H registers.
19173 @item set sh calling-convention @var{convention}
19174 @kindex set sh calling-convention
19175 Set the calling-convention used when calling functions from @value{GDBN}.
19176 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19177 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19178 convention. If the DWARF-2 information of the called function specifies
19179 that the function follows the Renesas calling convention, the function
19180 is called using the Renesas calling convention. If the calling convention
19181 is set to @samp{renesas}, the Renesas calling convention is always used,
19182 regardless of the DWARF-2 information. This can be used to override the
19183 default of @samp{gcc} if debug information is missing, or the compiler
19184 does not emit the DWARF-2 calling convention entry for a function.
19186 @item show sh calling-convention
19187 @kindex show sh calling-convention
19188 Show the current calling convention setting.
19193 @node Architectures
19194 @section Architectures
19196 This section describes characteristics of architectures that affect
19197 all uses of @value{GDBN} with the architecture, both native and cross.
19204 * HPPA:: HP PA architecture
19205 * SPU:: Cell Broadband Engine SPU architecture
19210 @subsection x86 Architecture-specific Issues
19213 @item set struct-convention @var{mode}
19214 @kindex set struct-convention
19215 @cindex struct return convention
19216 @cindex struct/union returned in registers
19217 Set the convention used by the inferior to return @code{struct}s and
19218 @code{union}s from functions to @var{mode}. Possible values of
19219 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19220 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19221 are returned on the stack, while @code{"reg"} means that a
19222 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19223 be returned in a register.
19225 @item show struct-convention
19226 @kindex show struct-convention
19227 Show the current setting of the convention to return @code{struct}s
19236 @kindex set rstack_high_address
19237 @cindex AMD 29K register stack
19238 @cindex register stack, AMD29K
19239 @item set rstack_high_address @var{address}
19240 On AMD 29000 family processors, registers are saved in a separate
19241 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19242 extent of this stack. Normally, @value{GDBN} just assumes that the
19243 stack is ``large enough''. This may result in @value{GDBN} referencing
19244 memory locations that do not exist. If necessary, you can get around
19245 this problem by specifying the ending address of the register stack with
19246 the @code{set rstack_high_address} command. The argument should be an
19247 address, which you probably want to precede with @samp{0x} to specify in
19250 @kindex show rstack_high_address
19251 @item show rstack_high_address
19252 Display the current limit of the register stack, on AMD 29000 family
19260 See the following section.
19265 @cindex stack on Alpha
19266 @cindex stack on MIPS
19267 @cindex Alpha stack
19269 Alpha- and MIPS-based computers use an unusual stack frame, which
19270 sometimes requires @value{GDBN} to search backward in the object code to
19271 find the beginning of a function.
19273 @cindex response time, MIPS debugging
19274 To improve response time (especially for embedded applications, where
19275 @value{GDBN} may be restricted to a slow serial line for this search)
19276 you may want to limit the size of this search, using one of these
19280 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19281 @item set heuristic-fence-post @var{limit}
19282 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19283 search for the beginning of a function. A value of @var{0} (the
19284 default) means there is no limit. However, except for @var{0}, the
19285 larger the limit the more bytes @code{heuristic-fence-post} must search
19286 and therefore the longer it takes to run. You should only need to use
19287 this command when debugging a stripped executable.
19289 @item show heuristic-fence-post
19290 Display the current limit.
19294 These commands are available @emph{only} when @value{GDBN} is configured
19295 for debugging programs on Alpha or MIPS processors.
19297 Several MIPS-specific commands are available when debugging MIPS
19301 @item set mips abi @var{arg}
19302 @kindex set mips abi
19303 @cindex set ABI for MIPS
19304 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19305 values of @var{arg} are:
19309 The default ABI associated with the current binary (this is the
19320 @item show mips abi
19321 @kindex show mips abi
19322 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19325 @itemx show mipsfpu
19326 @xref{MIPS Embedded, set mipsfpu}.
19328 @item set mips mask-address @var{arg}
19329 @kindex set mips mask-address
19330 @cindex MIPS addresses, masking
19331 This command determines whether the most-significant 32 bits of 64-bit
19332 MIPS addresses are masked off. The argument @var{arg} can be
19333 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19334 setting, which lets @value{GDBN} determine the correct value.
19336 @item show mips mask-address
19337 @kindex show mips mask-address
19338 Show whether the upper 32 bits of MIPS addresses are masked off or
19341 @item set remote-mips64-transfers-32bit-regs
19342 @kindex set remote-mips64-transfers-32bit-regs
19343 This command controls compatibility with 64-bit MIPS targets that
19344 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19345 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19346 and 64 bits for other registers, set this option to @samp{on}.
19348 @item show remote-mips64-transfers-32bit-regs
19349 @kindex show remote-mips64-transfers-32bit-regs
19350 Show the current setting of compatibility with older MIPS 64 targets.
19352 @item set debug mips
19353 @kindex set debug mips
19354 This command turns on and off debugging messages for the MIPS-specific
19355 target code in @value{GDBN}.
19357 @item show debug mips
19358 @kindex show debug mips
19359 Show the current setting of MIPS debugging messages.
19365 @cindex HPPA support
19367 When @value{GDBN} is debugging the HP PA architecture, it provides the
19368 following special commands:
19371 @item set debug hppa
19372 @kindex set debug hppa
19373 This command determines whether HPPA architecture-specific debugging
19374 messages are to be displayed.
19376 @item show debug hppa
19377 Show whether HPPA debugging messages are displayed.
19379 @item maint print unwind @var{address}
19380 @kindex maint print unwind@r{, HPPA}
19381 This command displays the contents of the unwind table entry at the
19382 given @var{address}.
19388 @subsection Cell Broadband Engine SPU architecture
19389 @cindex Cell Broadband Engine
19392 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19393 it provides the following special commands:
19396 @item info spu event
19398 Display SPU event facility status. Shows current event mask
19399 and pending event status.
19401 @item info spu signal
19402 Display SPU signal notification facility status. Shows pending
19403 signal-control word and signal notification mode of both signal
19404 notification channels.
19406 @item info spu mailbox
19407 Display SPU mailbox facility status. Shows all pending entries,
19408 in order of processing, in each of the SPU Write Outbound,
19409 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19412 Display MFC DMA status. Shows all pending commands in the MFC
19413 DMA queue. For each entry, opcode, tag, class IDs, effective
19414 and local store addresses and transfer size are shown.
19416 @item info spu proxydma
19417 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19418 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19419 and local store addresses and transfer size are shown.
19423 When @value{GDBN} is debugging a combined PowerPC/SPU application
19424 on the Cell Broadband Engine, it provides in addition the following
19428 @item set spu stop-on-load @var{arg}
19430 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19431 will give control to the user when a new SPE thread enters its @code{main}
19432 function. The default is @code{off}.
19434 @item show spu stop-on-load
19436 Show whether to stop for new SPE threads.
19438 @item set spu auto-flush-cache @var{arg}
19439 Set whether to automatically flush the software-managed cache. When set to
19440 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19441 cache to be flushed whenever SPE execution stops. This provides a consistent
19442 view of PowerPC memory that is accessed via the cache. If an application
19443 does not use the software-managed cache, this option has no effect.
19445 @item show spu auto-flush-cache
19446 Show whether to automatically flush the software-managed cache.
19451 @subsection PowerPC
19452 @cindex PowerPC architecture
19454 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19455 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19456 numbers stored in the floating point registers. These values must be stored
19457 in two consecutive registers, always starting at an even register like
19458 @code{f0} or @code{f2}.
19460 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19461 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19462 @code{f2} and @code{f3} for @code{$dl1} and so on.
19464 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19465 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19468 @node Controlling GDB
19469 @chapter Controlling @value{GDBN}
19471 You can alter the way @value{GDBN} interacts with you by using the
19472 @code{set} command. For commands controlling how @value{GDBN} displays
19473 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19478 * Editing:: Command editing
19479 * Command History:: Command history
19480 * Screen Size:: Screen size
19481 * Numbers:: Numbers
19482 * ABI:: Configuring the current ABI
19483 * Messages/Warnings:: Optional warnings and messages
19484 * Debugging Output:: Optional messages about internal happenings
19485 * Other Misc Settings:: Other Miscellaneous Settings
19493 @value{GDBN} indicates its readiness to read a command by printing a string
19494 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19495 can change the prompt string with the @code{set prompt} command. For
19496 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19497 the prompt in one of the @value{GDBN} sessions so that you can always tell
19498 which one you are talking to.
19500 @emph{Note:} @code{set prompt} does not add a space for you after the
19501 prompt you set. This allows you to set a prompt which ends in a space
19502 or a prompt that does not.
19506 @item set prompt @var{newprompt}
19507 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19509 @kindex show prompt
19511 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19515 @section Command Editing
19517 @cindex command line editing
19519 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19520 @sc{gnu} library provides consistent behavior for programs which provide a
19521 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19522 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19523 substitution, and a storage and recall of command history across
19524 debugging sessions.
19526 You may control the behavior of command line editing in @value{GDBN} with the
19527 command @code{set}.
19530 @kindex set editing
19533 @itemx set editing on
19534 Enable command line editing (enabled by default).
19536 @item set editing off
19537 Disable command line editing.
19539 @kindex show editing
19541 Show whether command line editing is enabled.
19544 @ifset SYSTEM_READLINE
19545 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19547 @ifclear SYSTEM_READLINE
19548 @xref{Command Line Editing},
19550 for more details about the Readline
19551 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19552 encouraged to read that chapter.
19554 @node Command History
19555 @section Command History
19556 @cindex command history
19558 @value{GDBN} can keep track of the commands you type during your
19559 debugging sessions, so that you can be certain of precisely what
19560 happened. Use these commands to manage the @value{GDBN} command
19563 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19564 package, to provide the history facility.
19565 @ifset SYSTEM_READLINE
19566 @xref{Using History Interactively, , , history, GNU History Library},
19568 @ifclear SYSTEM_READLINE
19569 @xref{Using History Interactively},
19571 for the detailed description of the History library.
19573 To issue a command to @value{GDBN} without affecting certain aspects of
19574 the state which is seen by users, prefix it with @samp{server }
19575 (@pxref{Server Prefix}). This
19576 means that this command will not affect the command history, nor will it
19577 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19578 pressed on a line by itself.
19580 @cindex @code{server}, command prefix
19581 The server prefix does not affect the recording of values into the value
19582 history; to print a value without recording it into the value history,
19583 use the @code{output} command instead of the @code{print} command.
19585 Here is the description of @value{GDBN} commands related to command
19589 @cindex history substitution
19590 @cindex history file
19591 @kindex set history filename
19592 @cindex @env{GDBHISTFILE}, environment variable
19593 @item set history filename @var{fname}
19594 Set the name of the @value{GDBN} command history file to @var{fname}.
19595 This is the file where @value{GDBN} reads an initial command history
19596 list, and where it writes the command history from this session when it
19597 exits. You can access this list through history expansion or through
19598 the history command editing characters listed below. This file defaults
19599 to the value of the environment variable @code{GDBHISTFILE}, or to
19600 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19603 @cindex save command history
19604 @kindex set history save
19605 @item set history save
19606 @itemx set history save on
19607 Record command history in a file, whose name may be specified with the
19608 @code{set history filename} command. By default, this option is disabled.
19610 @item set history save off
19611 Stop recording command history in a file.
19613 @cindex history size
19614 @kindex set history size
19615 @cindex @env{HISTSIZE}, environment variable
19616 @item set history size @var{size}
19617 Set the number of commands which @value{GDBN} keeps in its history list.
19618 This defaults to the value of the environment variable
19619 @code{HISTSIZE}, or to 256 if this variable is not set.
19622 History expansion assigns special meaning to the character @kbd{!}.
19623 @ifset SYSTEM_READLINE
19624 @xref{Event Designators, , , history, GNU History Library},
19626 @ifclear SYSTEM_READLINE
19627 @xref{Event Designators},
19631 @cindex history expansion, turn on/off
19632 Since @kbd{!} is also the logical not operator in C, history expansion
19633 is off by default. If you decide to enable history expansion with the
19634 @code{set history expansion on} command, you may sometimes need to
19635 follow @kbd{!} (when it is used as logical not, in an expression) with
19636 a space or a tab to prevent it from being expanded. The readline
19637 history facilities do not attempt substitution on the strings
19638 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19640 The commands to control history expansion are:
19643 @item set history expansion on
19644 @itemx set history expansion
19645 @kindex set history expansion
19646 Enable history expansion. History expansion is off by default.
19648 @item set history expansion off
19649 Disable history expansion.
19652 @kindex show history
19654 @itemx show history filename
19655 @itemx show history save
19656 @itemx show history size
19657 @itemx show history expansion
19658 These commands display the state of the @value{GDBN} history parameters.
19659 @code{show history} by itself displays all four states.
19664 @kindex show commands
19665 @cindex show last commands
19666 @cindex display command history
19667 @item show commands
19668 Display the last ten commands in the command history.
19670 @item show commands @var{n}
19671 Print ten commands centered on command number @var{n}.
19673 @item show commands +
19674 Print ten commands just after the commands last printed.
19678 @section Screen Size
19679 @cindex size of screen
19680 @cindex pauses in output
19682 Certain commands to @value{GDBN} may produce large amounts of
19683 information output to the screen. To help you read all of it,
19684 @value{GDBN} pauses and asks you for input at the end of each page of
19685 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19686 to discard the remaining output. Also, the screen width setting
19687 determines when to wrap lines of output. Depending on what is being
19688 printed, @value{GDBN} tries to break the line at a readable place,
19689 rather than simply letting it overflow onto the following line.
19691 Normally @value{GDBN} knows the size of the screen from the terminal
19692 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19693 together with the value of the @code{TERM} environment variable and the
19694 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19695 you can override it with the @code{set height} and @code{set
19702 @kindex show height
19703 @item set height @var{lpp}
19705 @itemx set width @var{cpl}
19707 These @code{set} commands specify a screen height of @var{lpp} lines and
19708 a screen width of @var{cpl} characters. The associated @code{show}
19709 commands display the current settings.
19711 If you specify a height of zero lines, @value{GDBN} does not pause during
19712 output no matter how long the output is. This is useful if output is to a
19713 file or to an editor buffer.
19715 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19716 from wrapping its output.
19718 @item set pagination on
19719 @itemx set pagination off
19720 @kindex set pagination
19721 Turn the output pagination on or off; the default is on. Turning
19722 pagination off is the alternative to @code{set height 0}. Note that
19723 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19724 Options, -batch}) also automatically disables pagination.
19726 @item show pagination
19727 @kindex show pagination
19728 Show the current pagination mode.
19733 @cindex number representation
19734 @cindex entering numbers
19736 You can always enter numbers in octal, decimal, or hexadecimal in
19737 @value{GDBN} by the usual conventions: octal numbers begin with
19738 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19739 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19740 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19741 10; likewise, the default display for numbers---when no particular
19742 format is specified---is base 10. You can change the default base for
19743 both input and output with the commands described below.
19746 @kindex set input-radix
19747 @item set input-radix @var{base}
19748 Set the default base for numeric input. Supported choices
19749 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19750 specified either unambiguously or using the current input radix; for
19754 set input-radix 012
19755 set input-radix 10.
19756 set input-radix 0xa
19760 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19761 leaves the input radix unchanged, no matter what it was, since
19762 @samp{10}, being without any leading or trailing signs of its base, is
19763 interpreted in the current radix. Thus, if the current radix is 16,
19764 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19767 @kindex set output-radix
19768 @item set output-radix @var{base}
19769 Set the default base for numeric display. Supported choices
19770 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19771 specified either unambiguously or using the current input radix.
19773 @kindex show input-radix
19774 @item show input-radix
19775 Display the current default base for numeric input.
19777 @kindex show output-radix
19778 @item show output-radix
19779 Display the current default base for numeric display.
19781 @item set radix @r{[}@var{base}@r{]}
19785 These commands set and show the default base for both input and output
19786 of numbers. @code{set radix} sets the radix of input and output to
19787 the same base; without an argument, it resets the radix back to its
19788 default value of 10.
19793 @section Configuring the Current ABI
19795 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19796 application automatically. However, sometimes you need to override its
19797 conclusions. Use these commands to manage @value{GDBN}'s view of the
19804 One @value{GDBN} configuration can debug binaries for multiple operating
19805 system targets, either via remote debugging or native emulation.
19806 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19807 but you can override its conclusion using the @code{set osabi} command.
19808 One example where this is useful is in debugging of binaries which use
19809 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19810 not have the same identifying marks that the standard C library for your
19815 Show the OS ABI currently in use.
19818 With no argument, show the list of registered available OS ABI's.
19820 @item set osabi @var{abi}
19821 Set the current OS ABI to @var{abi}.
19824 @cindex float promotion
19826 Generally, the way that an argument of type @code{float} is passed to a
19827 function depends on whether the function is prototyped. For a prototyped
19828 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19829 according to the architecture's convention for @code{float}. For unprototyped
19830 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19831 @code{double} and then passed.
19833 Unfortunately, some forms of debug information do not reliably indicate whether
19834 a function is prototyped. If @value{GDBN} calls a function that is not marked
19835 as prototyped, it consults @kbd{set coerce-float-to-double}.
19838 @kindex set coerce-float-to-double
19839 @item set coerce-float-to-double
19840 @itemx set coerce-float-to-double on
19841 Arguments of type @code{float} will be promoted to @code{double} when passed
19842 to an unprototyped function. This is the default setting.
19844 @item set coerce-float-to-double off
19845 Arguments of type @code{float} will be passed directly to unprototyped
19848 @kindex show coerce-float-to-double
19849 @item show coerce-float-to-double
19850 Show the current setting of promoting @code{float} to @code{double}.
19854 @kindex show cp-abi
19855 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19856 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19857 used to build your application. @value{GDBN} only fully supports
19858 programs with a single C@t{++} ABI; if your program contains code using
19859 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19860 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19861 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19862 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19863 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19864 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19869 Show the C@t{++} ABI currently in use.
19872 With no argument, show the list of supported C@t{++} ABI's.
19874 @item set cp-abi @var{abi}
19875 @itemx set cp-abi auto
19876 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19879 @node Messages/Warnings
19880 @section Optional Warnings and Messages
19882 @cindex verbose operation
19883 @cindex optional warnings
19884 By default, @value{GDBN} is silent about its inner workings. If you are
19885 running on a slow machine, you may want to use the @code{set verbose}
19886 command. This makes @value{GDBN} tell you when it does a lengthy
19887 internal operation, so you will not think it has crashed.
19889 Currently, the messages controlled by @code{set verbose} are those
19890 which announce that the symbol table for a source file is being read;
19891 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19894 @kindex set verbose
19895 @item set verbose on
19896 Enables @value{GDBN} output of certain informational messages.
19898 @item set verbose off
19899 Disables @value{GDBN} output of certain informational messages.
19901 @kindex show verbose
19903 Displays whether @code{set verbose} is on or off.
19906 By default, if @value{GDBN} encounters bugs in the symbol table of an
19907 object file, it is silent; but if you are debugging a compiler, you may
19908 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19913 @kindex set complaints
19914 @item set complaints @var{limit}
19915 Permits @value{GDBN} to output @var{limit} complaints about each type of
19916 unusual symbols before becoming silent about the problem. Set
19917 @var{limit} to zero to suppress all complaints; set it to a large number
19918 to prevent complaints from being suppressed.
19920 @kindex show complaints
19921 @item show complaints
19922 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19926 @anchor{confirmation requests}
19927 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19928 lot of stupid questions to confirm certain commands. For example, if
19929 you try to run a program which is already running:
19933 The program being debugged has been started already.
19934 Start it from the beginning? (y or n)
19937 If you are willing to unflinchingly face the consequences of your own
19938 commands, you can disable this ``feature'':
19942 @kindex set confirm
19944 @cindex confirmation
19945 @cindex stupid questions
19946 @item set confirm off
19947 Disables confirmation requests. Note that running @value{GDBN} with
19948 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19949 automatically disables confirmation requests.
19951 @item set confirm on
19952 Enables confirmation requests (the default).
19954 @kindex show confirm
19956 Displays state of confirmation requests.
19960 @cindex command tracing
19961 If you need to debug user-defined commands or sourced files you may find it
19962 useful to enable @dfn{command tracing}. In this mode each command will be
19963 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19964 quantity denoting the call depth of each command.
19967 @kindex set trace-commands
19968 @cindex command scripts, debugging
19969 @item set trace-commands on
19970 Enable command tracing.
19971 @item set trace-commands off
19972 Disable command tracing.
19973 @item show trace-commands
19974 Display the current state of command tracing.
19977 @node Debugging Output
19978 @section Optional Messages about Internal Happenings
19979 @cindex optional debugging messages
19981 @value{GDBN} has commands that enable optional debugging messages from
19982 various @value{GDBN} subsystems; normally these commands are of
19983 interest to @value{GDBN} maintainers, or when reporting a bug. This
19984 section documents those commands.
19987 @kindex set exec-done-display
19988 @item set exec-done-display
19989 Turns on or off the notification of asynchronous commands'
19990 completion. When on, @value{GDBN} will print a message when an
19991 asynchronous command finishes its execution. The default is off.
19992 @kindex show exec-done-display
19993 @item show exec-done-display
19994 Displays the current setting of asynchronous command completion
19997 @cindex gdbarch debugging info
19998 @cindex architecture debugging info
19999 @item set debug arch
20000 Turns on or off display of gdbarch debugging info. The default is off
20002 @item show debug arch
20003 Displays the current state of displaying gdbarch debugging info.
20004 @item set debug aix-thread
20005 @cindex AIX threads
20006 Display debugging messages about inner workings of the AIX thread
20008 @item show debug aix-thread
20009 Show the current state of AIX thread debugging info display.
20010 @item set debug dwarf2-die
20011 @cindex DWARF2 DIEs
20012 Dump DWARF2 DIEs after they are read in.
20013 The value is the number of nesting levels to print.
20014 A value of zero turns off the display.
20015 @item show debug dwarf2-die
20016 Show the current state of DWARF2 DIE debugging.
20017 @item set debug displaced
20018 @cindex displaced stepping debugging info
20019 Turns on or off display of @value{GDBN} debugging info for the
20020 displaced stepping support. The default is off.
20021 @item show debug displaced
20022 Displays the current state of displaying @value{GDBN} debugging info
20023 related to displaced stepping.
20024 @item set debug event
20025 @cindex event debugging info
20026 Turns on or off display of @value{GDBN} event debugging info. The
20028 @item show debug event
20029 Displays the current state of displaying @value{GDBN} event debugging
20031 @item set debug expression
20032 @cindex expression debugging info
20033 Turns on or off display of debugging info about @value{GDBN}
20034 expression parsing. The default is off.
20035 @item show debug expression
20036 Displays the current state of displaying debugging info about
20037 @value{GDBN} expression parsing.
20038 @item set debug frame
20039 @cindex frame debugging info
20040 Turns on or off display of @value{GDBN} frame debugging info. The
20042 @item show debug frame
20043 Displays the current state of displaying @value{GDBN} frame debugging
20045 @item set debug gnu-nat
20046 @cindex @sc{gnu}/Hurd debug messages
20047 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20048 @item show debug gnu-nat
20049 Show the current state of @sc{gnu}/Hurd debugging messages.
20050 @item set debug infrun
20051 @cindex inferior debugging info
20052 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20053 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20054 for implementing operations such as single-stepping the inferior.
20055 @item show debug infrun
20056 Displays the current state of @value{GDBN} inferior debugging.
20057 @item set debug jit
20058 @cindex just-in-time compilation, debugging messages
20059 Turns on or off debugging messages from JIT debug support.
20060 @item show debug jit
20061 Displays the current state of @value{GDBN} JIT debugging.
20062 @item set debug lin-lwp
20063 @cindex @sc{gnu}/Linux LWP debug messages
20064 @cindex Linux lightweight processes
20065 Turns on or off debugging messages from the Linux LWP debug support.
20066 @item show debug lin-lwp
20067 Show the current state of Linux LWP debugging messages.
20068 @item set debug lin-lwp-async
20069 @cindex @sc{gnu}/Linux LWP async debug messages
20070 @cindex Linux lightweight processes
20071 Turns on or off debugging messages from the Linux LWP async debug support.
20072 @item show debug lin-lwp-async
20073 Show the current state of Linux LWP async debugging messages.
20074 @item set debug observer
20075 @cindex observer debugging info
20076 Turns on or off display of @value{GDBN} observer debugging. This
20077 includes info such as the notification of observable events.
20078 @item show debug observer
20079 Displays the current state of observer debugging.
20080 @item set debug overload
20081 @cindex C@t{++} overload debugging info
20082 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20083 info. This includes info such as ranking of functions, etc. The default
20085 @item show debug overload
20086 Displays the current state of displaying @value{GDBN} C@t{++} overload
20088 @cindex expression parser, debugging info
20089 @cindex debug expression parser
20090 @item set debug parser
20091 Turns on or off the display of expression parser debugging output.
20092 Internally, this sets the @code{yydebug} variable in the expression
20093 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20094 details. The default is off.
20095 @item show debug parser
20096 Show the current state of expression parser debugging.
20097 @cindex packets, reporting on stdout
20098 @cindex serial connections, debugging
20099 @cindex debug remote protocol
20100 @cindex remote protocol debugging
20101 @cindex display remote packets
20102 @item set debug remote
20103 Turns on or off display of reports on all packets sent back and forth across
20104 the serial line to the remote machine. The info is printed on the
20105 @value{GDBN} standard output stream. The default is off.
20106 @item show debug remote
20107 Displays the state of display of remote packets.
20108 @item set debug serial
20109 Turns on or off display of @value{GDBN} serial debugging info. The
20111 @item show debug serial
20112 Displays the current state of displaying @value{GDBN} serial debugging
20114 @item set debug solib-frv
20115 @cindex FR-V shared-library debugging
20116 Turns on or off debugging messages for FR-V shared-library code.
20117 @item show debug solib-frv
20118 Display the current state of FR-V shared-library code debugging
20120 @item set debug target
20121 @cindex target debugging info
20122 Turns on or off display of @value{GDBN} target debugging info. This info
20123 includes what is going on at the target level of GDB, as it happens. The
20124 default is 0. Set it to 1 to track events, and to 2 to also track the
20125 value of large memory transfers. Changes to this flag do not take effect
20126 until the next time you connect to a target or use the @code{run} command.
20127 @item show debug target
20128 Displays the current state of displaying @value{GDBN} target debugging
20130 @item set debug timestamp
20131 @cindex timestampping debugging info
20132 Turns on or off display of timestamps with @value{GDBN} debugging info.
20133 When enabled, seconds and microseconds are displayed before each debugging
20135 @item show debug timestamp
20136 Displays the current state of displaying timestamps with @value{GDBN}
20138 @item set debugvarobj
20139 @cindex variable object debugging info
20140 Turns on or off display of @value{GDBN} variable object debugging
20141 info. The default is off.
20142 @item show debugvarobj
20143 Displays the current state of displaying @value{GDBN} variable object
20145 @item set debug xml
20146 @cindex XML parser debugging
20147 Turns on or off debugging messages for built-in XML parsers.
20148 @item show debug xml
20149 Displays the current state of XML debugging messages.
20152 @node Other Misc Settings
20153 @section Other Miscellaneous Settings
20154 @cindex miscellaneous settings
20157 @kindex set interactive-mode
20158 @item set interactive-mode
20159 If @code{on}, forces @value{GDBN} to assume that GDB was started
20160 in a terminal. In practice, this means that @value{GDBN} should wait
20161 for the user to answer queries generated by commands entered at
20162 the command prompt. If @code{off}, forces @value{GDBN} to operate
20163 in the opposite mode, and it uses the default answers to all queries.
20164 If @code{auto} (the default), @value{GDBN} tries to determine whether
20165 its standard input is a terminal, and works in interactive-mode if it
20166 is, non-interactively otherwise.
20168 In the vast majority of cases, the debugger should be able to guess
20169 correctly which mode should be used. But this setting can be useful
20170 in certain specific cases, such as running a MinGW @value{GDBN}
20171 inside a cygwin window.
20173 @kindex show interactive-mode
20174 @item show interactive-mode
20175 Displays whether the debugger is operating in interactive mode or not.
20178 @node Extending GDB
20179 @chapter Extending @value{GDBN}
20180 @cindex extending GDB
20182 @value{GDBN} provides two mechanisms for extension. The first is based
20183 on composition of @value{GDBN} commands, and the second is based on the
20184 Python scripting language.
20186 To facilitate the use of these extensions, @value{GDBN} is capable
20187 of evaluating the contents of a file. When doing so, @value{GDBN}
20188 can recognize which scripting language is being used by looking at
20189 the filename extension. Files with an unrecognized filename extension
20190 are always treated as a @value{GDBN} Command Files.
20191 @xref{Command Files,, Command files}.
20193 You can control how @value{GDBN} evaluates these files with the following
20197 @kindex set script-extension
20198 @kindex show script-extension
20199 @item set script-extension off
20200 All scripts are always evaluated as @value{GDBN} Command Files.
20202 @item set script-extension soft
20203 The debugger determines the scripting language based on filename
20204 extension. If this scripting language is supported, @value{GDBN}
20205 evaluates the script using that language. Otherwise, it evaluates
20206 the file as a @value{GDBN} Command File.
20208 @item set script-extension strict
20209 The debugger determines the scripting language based on filename
20210 extension, and evaluates the script using that language. If the
20211 language is not supported, then the evaluation fails.
20213 @item show script-extension
20214 Display the current value of the @code{script-extension} option.
20219 * Sequences:: Canned Sequences of Commands
20220 * Python:: Scripting @value{GDBN} using Python
20224 @section Canned Sequences of Commands
20226 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20227 Command Lists}), @value{GDBN} provides two ways to store sequences of
20228 commands for execution as a unit: user-defined commands and command
20232 * Define:: How to define your own commands
20233 * Hooks:: Hooks for user-defined commands
20234 * Command Files:: How to write scripts of commands to be stored in a file
20235 * Output:: Commands for controlled output
20239 @subsection User-defined Commands
20241 @cindex user-defined command
20242 @cindex arguments, to user-defined commands
20243 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20244 which you assign a new name as a command. This is done with the
20245 @code{define} command. User commands may accept up to 10 arguments
20246 separated by whitespace. Arguments are accessed within the user command
20247 via @code{$arg0@dots{}$arg9}. A trivial example:
20251 print $arg0 + $arg1 + $arg2
20256 To execute the command use:
20263 This defines the command @code{adder}, which prints the sum of
20264 its three arguments. Note the arguments are text substitutions, so they may
20265 reference variables, use complex expressions, or even perform inferior
20268 @cindex argument count in user-defined commands
20269 @cindex how many arguments (user-defined commands)
20270 In addition, @code{$argc} may be used to find out how many arguments have
20271 been passed. This expands to a number in the range 0@dots{}10.
20276 print $arg0 + $arg1
20279 print $arg0 + $arg1 + $arg2
20287 @item define @var{commandname}
20288 Define a command named @var{commandname}. If there is already a command
20289 by that name, you are asked to confirm that you want to redefine it.
20290 @var{commandname} may be a bare command name consisting of letters,
20291 numbers, dashes, and underscores. It may also start with any predefined
20292 prefix command. For example, @samp{define target my-target} creates
20293 a user-defined @samp{target my-target} command.
20295 The definition of the command is made up of other @value{GDBN} command lines,
20296 which are given following the @code{define} command. The end of these
20297 commands is marked by a line containing @code{end}.
20300 @kindex end@r{ (user-defined commands)}
20301 @item document @var{commandname}
20302 Document the user-defined command @var{commandname}, so that it can be
20303 accessed by @code{help}. The command @var{commandname} must already be
20304 defined. This command reads lines of documentation just as @code{define}
20305 reads the lines of the command definition, ending with @code{end}.
20306 After the @code{document} command is finished, @code{help} on command
20307 @var{commandname} displays the documentation you have written.
20309 You may use the @code{document} command again to change the
20310 documentation of a command. Redefining the command with @code{define}
20311 does not change the documentation.
20313 @kindex dont-repeat
20314 @cindex don't repeat command
20316 Used inside a user-defined command, this tells @value{GDBN} that this
20317 command should not be repeated when the user hits @key{RET}
20318 (@pxref{Command Syntax, repeat last command}).
20320 @kindex help user-defined
20321 @item help user-defined
20322 List all user-defined commands, with the first line of the documentation
20327 @itemx show user @var{commandname}
20328 Display the @value{GDBN} commands used to define @var{commandname} (but
20329 not its documentation). If no @var{commandname} is given, display the
20330 definitions for all user-defined commands.
20332 @cindex infinite recursion in user-defined commands
20333 @kindex show max-user-call-depth
20334 @kindex set max-user-call-depth
20335 @item show max-user-call-depth
20336 @itemx set max-user-call-depth
20337 The value of @code{max-user-call-depth} controls how many recursion
20338 levels are allowed in user-defined commands before @value{GDBN} suspects an
20339 infinite recursion and aborts the command.
20342 In addition to the above commands, user-defined commands frequently
20343 use control flow commands, described in @ref{Command Files}.
20345 When user-defined commands are executed, the
20346 commands of the definition are not printed. An error in any command
20347 stops execution of the user-defined command.
20349 If used interactively, commands that would ask for confirmation proceed
20350 without asking when used inside a user-defined command. Many @value{GDBN}
20351 commands that normally print messages to say what they are doing omit the
20352 messages when used in a user-defined command.
20355 @subsection User-defined Command Hooks
20356 @cindex command hooks
20357 @cindex hooks, for commands
20358 @cindex hooks, pre-command
20361 You may define @dfn{hooks}, which are a special kind of user-defined
20362 command. Whenever you run the command @samp{foo}, if the user-defined
20363 command @samp{hook-foo} exists, it is executed (with no arguments)
20364 before that command.
20366 @cindex hooks, post-command
20368 A hook may also be defined which is run after the command you executed.
20369 Whenever you run the command @samp{foo}, if the user-defined command
20370 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20371 that command. Post-execution hooks may exist simultaneously with
20372 pre-execution hooks, for the same command.
20374 It is valid for a hook to call the command which it hooks. If this
20375 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20377 @c It would be nice if hookpost could be passed a parameter indicating
20378 @c if the command it hooks executed properly or not. FIXME!
20380 @kindex stop@r{, a pseudo-command}
20381 In addition, a pseudo-command, @samp{stop} exists. Defining
20382 (@samp{hook-stop}) makes the associated commands execute every time
20383 execution stops in your program: before breakpoint commands are run,
20384 displays are printed, or the stack frame is printed.
20386 For example, to ignore @code{SIGALRM} signals while
20387 single-stepping, but treat them normally during normal execution,
20392 handle SIGALRM nopass
20396 handle SIGALRM pass
20399 define hook-continue
20400 handle SIGALRM pass
20404 As a further example, to hook at the beginning and end of the @code{echo}
20405 command, and to add extra text to the beginning and end of the message,
20413 define hookpost-echo
20417 (@value{GDBP}) echo Hello World
20418 <<<---Hello World--->>>
20423 You can define a hook for any single-word command in @value{GDBN}, but
20424 not for command aliases; you should define a hook for the basic command
20425 name, e.g.@: @code{backtrace} rather than @code{bt}.
20426 @c FIXME! So how does Joe User discover whether a command is an alias
20428 You can hook a multi-word command by adding @code{hook-} or
20429 @code{hookpost-} to the last word of the command, e.g.@:
20430 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20432 If an error occurs during the execution of your hook, execution of
20433 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20434 (before the command that you actually typed had a chance to run).
20436 If you try to define a hook which does not match any known command, you
20437 get a warning from the @code{define} command.
20439 @node Command Files
20440 @subsection Command Files
20442 @cindex command files
20443 @cindex scripting commands
20444 A command file for @value{GDBN} is a text file made of lines that are
20445 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20446 also be included. An empty line in a command file does nothing; it
20447 does not mean to repeat the last command, as it would from the
20450 You can request the execution of a command file with the @code{source}
20451 command. Note that the @code{source} command is also used to evaluate
20452 scripts that are not Command Files. The exact behavior can be configured
20453 using the @code{script-extension} setting.
20454 @xref{Extending GDB,, Extending GDB}.
20458 @cindex execute commands from a file
20459 @item source [-s] [-v] @var{filename}
20460 Execute the command file @var{filename}.
20463 The lines in a command file are generally executed sequentially,
20464 unless the order of execution is changed by one of the
20465 @emph{flow-control commands} described below. The commands are not
20466 printed as they are executed. An error in any command terminates
20467 execution of the command file and control is returned to the console.
20469 @value{GDBN} first searches for @var{filename} in the current directory.
20470 If the file is not found there, and @var{filename} does not specify a
20471 directory, then @value{GDBN} also looks for the file on the source search path
20472 (specified with the @samp{directory} command);
20473 except that @file{$cdir} is not searched because the compilation directory
20474 is not relevant to scripts.
20476 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20477 on the search path even if @var{filename} specifies a directory.
20478 The search is done by appending @var{filename} to each element of the
20479 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20480 and the search path contains @file{/home/user} then @value{GDBN} will
20481 look for the script @file{/home/user/mylib/myscript}.
20482 The search is also done if @var{filename} is an absolute path.
20483 For example, if @var{filename} is @file{/tmp/myscript} and
20484 the search path contains @file{/home/user} then @value{GDBN} will
20485 look for the script @file{/home/user/tmp/myscript}.
20486 For DOS-like systems, if @var{filename} contains a drive specification,
20487 it is stripped before concatenation. For example, if @var{filename} is
20488 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20489 will look for the script @file{c:/tmp/myscript}.
20491 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20492 each command as it is executed. The option must be given before
20493 @var{filename}, and is interpreted as part of the filename anywhere else.
20495 Commands that would ask for confirmation if used interactively proceed
20496 without asking when used in a command file. Many @value{GDBN} commands that
20497 normally print messages to say what they are doing omit the messages
20498 when called from command files.
20500 @value{GDBN} also accepts command input from standard input. In this
20501 mode, normal output goes to standard output and error output goes to
20502 standard error. Errors in a command file supplied on standard input do
20503 not terminate execution of the command file---execution continues with
20507 gdb < cmds > log 2>&1
20510 (The syntax above will vary depending on the shell used.) This example
20511 will execute commands from the file @file{cmds}. All output and errors
20512 would be directed to @file{log}.
20514 Since commands stored on command files tend to be more general than
20515 commands typed interactively, they frequently need to deal with
20516 complicated situations, such as different or unexpected values of
20517 variables and symbols, changes in how the program being debugged is
20518 built, etc. @value{GDBN} provides a set of flow-control commands to
20519 deal with these complexities. Using these commands, you can write
20520 complex scripts that loop over data structures, execute commands
20521 conditionally, etc.
20528 This command allows to include in your script conditionally executed
20529 commands. The @code{if} command takes a single argument, which is an
20530 expression to evaluate. It is followed by a series of commands that
20531 are executed only if the expression is true (its value is nonzero).
20532 There can then optionally be an @code{else} line, followed by a series
20533 of commands that are only executed if the expression was false. The
20534 end of the list is marked by a line containing @code{end}.
20538 This command allows to write loops. Its syntax is similar to
20539 @code{if}: the command takes a single argument, which is an expression
20540 to evaluate, and must be followed by the commands to execute, one per
20541 line, terminated by an @code{end}. These commands are called the
20542 @dfn{body} of the loop. The commands in the body of @code{while} are
20543 executed repeatedly as long as the expression evaluates to true.
20547 This command exits the @code{while} loop in whose body it is included.
20548 Execution of the script continues after that @code{while}s @code{end}
20551 @kindex loop_continue
20552 @item loop_continue
20553 This command skips the execution of the rest of the body of commands
20554 in the @code{while} loop in whose body it is included. Execution
20555 branches to the beginning of the @code{while} loop, where it evaluates
20556 the controlling expression.
20558 @kindex end@r{ (if/else/while commands)}
20560 Terminate the block of commands that are the body of @code{if},
20561 @code{else}, or @code{while} flow-control commands.
20566 @subsection Commands for Controlled Output
20568 During the execution of a command file or a user-defined command, normal
20569 @value{GDBN} output is suppressed; the only output that appears is what is
20570 explicitly printed by the commands in the definition. This section
20571 describes three commands useful for generating exactly the output you
20576 @item echo @var{text}
20577 @c I do not consider backslash-space a standard C escape sequence
20578 @c because it is not in ANSI.
20579 Print @var{text}. Nonprinting characters can be included in
20580 @var{text} using C escape sequences, such as @samp{\n} to print a
20581 newline. @strong{No newline is printed unless you specify one.}
20582 In addition to the standard C escape sequences, a backslash followed
20583 by a space stands for a space. This is useful for displaying a
20584 string with spaces at the beginning or the end, since leading and
20585 trailing spaces are otherwise trimmed from all arguments.
20586 To print @samp{@w{ }and foo =@w{ }}, use the command
20587 @samp{echo \@w{ }and foo = \@w{ }}.
20589 A backslash at the end of @var{text} can be used, as in C, to continue
20590 the command onto subsequent lines. For example,
20593 echo This is some text\n\
20594 which is continued\n\
20595 onto several lines.\n
20598 produces the same output as
20601 echo This is some text\n
20602 echo which is continued\n
20603 echo onto several lines.\n
20607 @item output @var{expression}
20608 Print the value of @var{expression} and nothing but that value: no
20609 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20610 value history either. @xref{Expressions, ,Expressions}, for more information
20613 @item output/@var{fmt} @var{expression}
20614 Print the value of @var{expression} in format @var{fmt}. You can use
20615 the same formats as for @code{print}. @xref{Output Formats,,Output
20616 Formats}, for more information.
20619 @item printf @var{template}, @var{expressions}@dots{}
20620 Print the values of one or more @var{expressions} under the control of
20621 the string @var{template}. To print several values, make
20622 @var{expressions} be a comma-separated list of individual expressions,
20623 which may be either numbers or pointers. Their values are printed as
20624 specified by @var{template}, exactly as a C program would do by
20625 executing the code below:
20628 printf (@var{template}, @var{expressions}@dots{});
20631 As in @code{C} @code{printf}, ordinary characters in @var{template}
20632 are printed verbatim, while @dfn{conversion specification} introduced
20633 by the @samp{%} character cause subsequent @var{expressions} to be
20634 evaluated, their values converted and formatted according to type and
20635 style information encoded in the conversion specifications, and then
20638 For example, you can print two values in hex like this:
20641 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20644 @code{printf} supports all the standard @code{C} conversion
20645 specifications, including the flags and modifiers between the @samp{%}
20646 character and the conversion letter, with the following exceptions:
20650 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20653 The modifier @samp{*} is not supported for specifying precision or
20657 The @samp{'} flag (for separation of digits into groups according to
20658 @code{LC_NUMERIC'}) is not supported.
20661 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20665 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20668 The conversion letters @samp{a} and @samp{A} are not supported.
20672 Note that the @samp{ll} type modifier is supported only if the
20673 underlying @code{C} implementation used to build @value{GDBN} supports
20674 the @code{long long int} type, and the @samp{L} type modifier is
20675 supported only if @code{long double} type is available.
20677 As in @code{C}, @code{printf} supports simple backslash-escape
20678 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20679 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20680 single character. Octal and hexadecimal escape sequences are not
20683 Additionally, @code{printf} supports conversion specifications for DFP
20684 (@dfn{Decimal Floating Point}) types using the following length modifiers
20685 together with a floating point specifier.
20690 @samp{H} for printing @code{Decimal32} types.
20693 @samp{D} for printing @code{Decimal64} types.
20696 @samp{DD} for printing @code{Decimal128} types.
20699 If the underlying @code{C} implementation used to build @value{GDBN} has
20700 support for the three length modifiers for DFP types, other modifiers
20701 such as width and precision will also be available for @value{GDBN} to use.
20703 In case there is no such @code{C} support, no additional modifiers will be
20704 available and the value will be printed in the standard way.
20706 Here's an example of printing DFP types using the above conversion letters:
20708 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20712 @item eval @var{template}, @var{expressions}@dots{}
20713 Convert the values of one or more @var{expressions} under the control of
20714 the string @var{template} to a command line, and call it.
20719 @section Scripting @value{GDBN} using Python
20720 @cindex python scripting
20721 @cindex scripting with python
20723 You can script @value{GDBN} using the @uref{http://www.python.org/,
20724 Python programming language}. This feature is available only if
20725 @value{GDBN} was configured using @option{--with-python}.
20727 @cindex python directory
20728 Python scripts used by @value{GDBN} should be installed in
20729 @file{@var{data-directory}/python}, where @var{data-directory} is
20730 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20731 This directory, known as the @dfn{python directory},
20732 is automatically added to the Python Search Path in order to allow
20733 the Python interpreter to locate all scripts installed at this location.
20736 * Python Commands:: Accessing Python from @value{GDBN}.
20737 * Python API:: Accessing @value{GDBN} from Python.
20738 * Auto-loading:: Automatically loading Python code.
20739 * Python modules:: Python modules provided by @value{GDBN}.
20742 @node Python Commands
20743 @subsection Python Commands
20744 @cindex python commands
20745 @cindex commands to access python
20747 @value{GDBN} provides one command for accessing the Python interpreter,
20748 and one related setting:
20752 @item python @r{[}@var{code}@r{]}
20753 The @code{python} command can be used to evaluate Python code.
20755 If given an argument, the @code{python} command will evaluate the
20756 argument as a Python command. For example:
20759 (@value{GDBP}) python print 23
20763 If you do not provide an argument to @code{python}, it will act as a
20764 multi-line command, like @code{define}. In this case, the Python
20765 script is made up of subsequent command lines, given after the
20766 @code{python} command. This command list is terminated using a line
20767 containing @code{end}. For example:
20770 (@value{GDBP}) python
20772 End with a line saying just "end".
20778 @kindex maint set python print-stack
20779 @item maint set python print-stack
20780 By default, @value{GDBN} will print a stack trace when an error occurs
20781 in a Python script. This can be controlled using @code{maint set
20782 python print-stack}: if @code{on}, the default, then Python stack
20783 printing is enabled; if @code{off}, then Python stack printing is
20787 It is also possible to execute a Python script from the @value{GDBN}
20791 @item source @file{script-name}
20792 The script name must end with @samp{.py} and @value{GDBN} must be configured
20793 to recognize the script language based on filename extension using
20794 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20796 @item python execfile ("script-name")
20797 This method is based on the @code{execfile} Python built-in function,
20798 and thus is always available.
20802 @subsection Python API
20804 @cindex programming in python
20806 @cindex python stdout
20807 @cindex python pagination
20808 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20809 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20810 A Python program which outputs to one of these streams may have its
20811 output interrupted by the user (@pxref{Screen Size}). In this
20812 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20815 * Basic Python:: Basic Python Functions.
20816 * Exception Handling:: How Python exceptions are translated.
20817 * Values From Inferior:: Python representation of values.
20818 * Types In Python:: Python representation of types.
20819 * Pretty Printing API:: Pretty-printing values.
20820 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20821 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20822 * Inferiors In Python:: Python representation of inferiors (processes)
20823 * Events In Python:: Listening for events from @value{GDBN}.
20824 * Threads In Python:: Accessing inferior threads from Python.
20825 * Commands In Python:: Implementing new commands in Python.
20826 * Parameters In Python:: Adding new @value{GDBN} parameters.
20827 * Functions In Python:: Writing new convenience functions.
20828 * Progspaces In Python:: Program spaces.
20829 * Objfiles In Python:: Object files.
20830 * Frames In Python:: Accessing inferior stack frames from Python.
20831 * Blocks In Python:: Accessing frame blocks from Python.
20832 * Symbols In Python:: Python representation of symbols.
20833 * Symbol Tables In Python:: Python representation of symbol tables.
20834 * Lazy Strings In Python:: Python representation of lazy strings.
20835 * Breakpoints In Python:: Manipulating breakpoints using Python.
20839 @subsubsection Basic Python
20841 @cindex python functions
20842 @cindex python module
20844 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20845 methods and classes added by @value{GDBN} are placed in this module.
20846 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20847 use in all scripts evaluated by the @code{python} command.
20849 @findex gdb.PYTHONDIR
20851 A string containing the python directory (@pxref{Python}).
20854 @findex gdb.execute
20855 @defun execute command [from_tty] [to_string]
20856 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20857 If a GDB exception happens while @var{command} runs, it is
20858 translated as described in @ref{Exception Handling,,Exception Handling}.
20860 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20861 command as having originated from the user invoking it interactively.
20862 It must be a boolean value. If omitted, it defaults to @code{False}.
20864 By default, any output produced by @var{command} is sent to
20865 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20866 @code{True}, then output will be collected by @code{gdb.execute} and
20867 returned as a string. The default is @code{False}, in which case the
20868 return value is @code{None}. If @var{to_string} is @code{True}, the
20869 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20870 and height, and its pagination will be disabled; @pxref{Screen Size}.
20873 @findex gdb.breakpoints
20875 Return a sequence holding all of @value{GDBN}'s breakpoints.
20876 @xref{Breakpoints In Python}, for more information.
20879 @findex gdb.parameter
20880 @defun parameter parameter
20881 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20882 string naming the parameter to look up; @var{parameter} may contain
20883 spaces if the parameter has a multi-part name. For example,
20884 @samp{print object} is a valid parameter name.
20886 If the named parameter does not exist, this function throws a
20887 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20888 parameter's value is converted to a Python value of the appropriate
20889 type, and returned.
20892 @findex gdb.history
20893 @defun history number
20894 Return a value from @value{GDBN}'s value history (@pxref{Value
20895 History}). @var{number} indicates which history element to return.
20896 If @var{number} is negative, then @value{GDBN} will take its absolute value
20897 and count backward from the last element (i.e., the most recent element) to
20898 find the value to return. If @var{number} is zero, then @value{GDBN} will
20899 return the most recent element. If the element specified by @var{number}
20900 doesn't exist in the value history, a @code{gdb.error} exception will be
20903 If no exception is raised, the return value is always an instance of
20904 @code{gdb.Value} (@pxref{Values From Inferior}).
20907 @findex gdb.parse_and_eval
20908 @defun parse_and_eval expression
20909 Parse @var{expression} as an expression in the current language,
20910 evaluate it, and return the result as a @code{gdb.Value}.
20911 @var{expression} must be a string.
20913 This function can be useful when implementing a new command
20914 (@pxref{Commands In Python}), as it provides a way to parse the
20915 command's argument as an expression. It is also useful simply to
20916 compute values, for example, it is the only way to get the value of a
20917 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20920 @findex gdb.post_event
20921 @defun post_event event
20922 Put @var{event}, a callable object taking no arguments, into
20923 @value{GDBN}'s internal event queue. This callable will be invoked at
20924 some later point, during @value{GDBN}'s event processing. Events
20925 posted using @code{post_event} will be run in the order in which they
20926 were posted; however, there is no way to know when they will be
20927 processed relative to other events inside @value{GDBN}.
20929 @value{GDBN} is not thread-safe. If your Python program uses multiple
20930 threads, you must be careful to only call @value{GDBN}-specific
20931 functions in the main @value{GDBN} thread. @code{post_event} ensures
20935 (@value{GDBP}) python
20939 > def __init__(self, message):
20940 > self.message = message;
20941 > def __call__(self):
20942 > gdb.write(self.message)
20944 >class MyThread1 (threading.Thread):
20946 > gdb.post_event(Writer("Hello "))
20948 >class MyThread2 (threading.Thread):
20950 > gdb.post_event(Writer("World\n"))
20952 >MyThread1().start()
20953 >MyThread2().start()
20955 (@value{GDBP}) Hello World
20960 @defun write string @r{[}stream{]}
20961 Print a string to @value{GDBN}'s paginated output stream. The
20962 optional @var{stream} determines the stream to print to. The default
20963 stream is @value{GDBN}'s standard output stream. Possible stream
20970 @value{GDBN}'s standard output stream.
20975 @value{GDBN}'s standard error stream.
20980 @value{GDBN}'s log stream (@pxref{Logging Output}).
20983 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20984 call this function and will automatically direct the output to the
20990 Flush the buffer of a @value{GDBN} paginated stream so that the
20991 contents are displayed immediately. @value{GDBN} will flush the
20992 contents of a stream automatically when it encounters a newline in the
20993 buffer. The optional @var{stream} determines the stream to flush. The
20994 default stream is @value{GDBN}'s standard output stream. Possible
21001 @value{GDBN}'s standard output stream.
21006 @value{GDBN}'s standard error stream.
21011 @value{GDBN}'s log stream (@pxref{Logging Output}).
21015 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21016 call this function for the relevant stream.
21019 @findex gdb.target_charset
21020 @defun target_charset
21021 Return the name of the current target character set (@pxref{Character
21022 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21023 that @samp{auto} is never returned.
21026 @findex gdb.target_wide_charset
21027 @defun target_wide_charset
21028 Return the name of the current target wide character set
21029 (@pxref{Character Sets}). This differs from
21030 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21034 @findex gdb.solib_name
21035 @defun solib_name address
21036 Return the name of the shared library holding the given @var{address}
21037 as a string, or @code{None}.
21040 @findex gdb.decode_line
21041 @defun decode_line @r{[}expression@r{]}
21042 Return locations of the line specified by @var{expression}, or of the
21043 current line if no argument was given. This function returns a Python
21044 tuple containing two elements. The first element contains a string
21045 holding any unparsed section of @var{expression} (or @code{None} if
21046 the expression has been fully parsed). The second element contains
21047 either @code{None} or another tuple that contains all the locations
21048 that match the expression represented as @code{gdb.Symtab_and_line}
21049 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21050 provided, it is decoded the way that @value{GDBN}'s inbuilt
21051 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21054 @node Exception Handling
21055 @subsubsection Exception Handling
21056 @cindex python exceptions
21057 @cindex exceptions, python
21059 When executing the @code{python} command, Python exceptions
21060 uncaught within the Python code are translated to calls to
21061 @value{GDBN} error-reporting mechanism. If the command that called
21062 @code{python} does not handle the error, @value{GDBN} will
21063 terminate it and print an error message containing the Python
21064 exception name, the associated value, and the Python call stack
21065 backtrace at the point where the exception was raised. Example:
21068 (@value{GDBP}) python print foo
21069 Traceback (most recent call last):
21070 File "<string>", line 1, in <module>
21071 NameError: name 'foo' is not defined
21074 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21075 Python code are converted to Python exceptions. The type of the
21076 Python exception depends on the error.
21080 This is the base class for most exceptions generated by @value{GDBN}.
21081 It is derived from @code{RuntimeError}, for compatibility with earlier
21082 versions of @value{GDBN}.
21084 If an error occurring in @value{GDBN} does not fit into some more
21085 specific category, then the generated exception will have this type.
21087 @item gdb.MemoryError
21088 This is a subclass of @code{gdb.error} which is thrown when an
21089 operation tried to access invalid memory in the inferior.
21091 @item KeyboardInterrupt
21092 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21093 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21096 In all cases, your exception handler will see the @value{GDBN} error
21097 message as its value and the Python call stack backtrace at the Python
21098 statement closest to where the @value{GDBN} error occured as the
21101 @findex gdb.GdbError
21102 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21103 it is useful to be able to throw an exception that doesn't cause a
21104 traceback to be printed. For example, the user may have invoked the
21105 command incorrectly. Use the @code{gdb.GdbError} exception
21106 to handle this case. Example:
21110 >class HelloWorld (gdb.Command):
21111 > """Greet the whole world."""
21112 > def __init__ (self):
21113 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21114 > def invoke (self, args, from_tty):
21115 > argv = gdb.string_to_argv (args)
21116 > if len (argv) != 0:
21117 > raise gdb.GdbError ("hello-world takes no arguments")
21118 > print "Hello, World!"
21121 (gdb) hello-world 42
21122 hello-world takes no arguments
21125 @node Values From Inferior
21126 @subsubsection Values From Inferior
21127 @cindex values from inferior, with Python
21128 @cindex python, working with values from inferior
21130 @cindex @code{gdb.Value}
21131 @value{GDBN} provides values it obtains from the inferior program in
21132 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21133 for its internal bookkeeping of the inferior's values, and for
21134 fetching values when necessary.
21136 Inferior values that are simple scalars can be used directly in
21137 Python expressions that are valid for the value's data type. Here's
21138 an example for an integer or floating-point value @code{some_val}:
21145 As result of this, @code{bar} will also be a @code{gdb.Value} object
21146 whose values are of the same type as those of @code{some_val}.
21148 Inferior values that are structures or instances of some class can
21149 be accessed using the Python @dfn{dictionary syntax}. For example, if
21150 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21151 can access its @code{foo} element with:
21154 bar = some_val['foo']
21157 Again, @code{bar} will also be a @code{gdb.Value} object.
21159 A @code{gdb.Value} that represents a function can be executed via
21160 inferior function call. Any arguments provided to the call must match
21161 the function's prototype, and must be provided in the order specified
21164 For example, @code{some_val} is a @code{gdb.Value} instance
21165 representing a function that takes two integers as arguments. To
21166 execute this function, call it like so:
21169 result = some_val (10,20)
21172 Any values returned from a function call will be stored as a
21175 The following attributes are provided:
21178 @defivar Value address
21179 If this object is addressable, this read-only attribute holds a
21180 @code{gdb.Value} object representing the address. Otherwise,
21181 this attribute holds @code{None}.
21184 @cindex optimized out value in Python
21185 @defivar Value is_optimized_out
21186 This read-only boolean attribute is true if the compiler optimized out
21187 this value, thus it is not available for fetching from the inferior.
21190 @defivar Value type
21191 The type of this @code{gdb.Value}. The value of this attribute is a
21192 @code{gdb.Type} object (@pxref{Types In Python}).
21195 @defivar Value dynamic_type
21196 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21197 type information (@acronym{RTTI}) to determine the dynamic type of the
21198 value. If this value is of class type, it will return the class in
21199 which the value is embedded, if any. If this value is of pointer or
21200 reference to a class type, it will compute the dynamic type of the
21201 referenced object, and return a pointer or reference to that type,
21202 respectively. In all other cases, it will return the value's static
21205 Note that this feature will only work when debugging a C@t{++} program
21206 that includes @acronym{RTTI} for the object in question. Otherwise,
21207 it will just return the static type of the value as in @kbd{ptype foo}
21208 (@pxref{Symbols, ptype}).
21212 The following methods are provided:
21215 @defmethod Value __init__ @var{val}
21216 Many Python values can be converted directly to a @code{gdb.Value} via
21217 this object initializer. Specifically:
21220 @item Python boolean
21221 A Python boolean is converted to the boolean type from the current
21224 @item Python integer
21225 A Python integer is converted to the C @code{long} type for the
21226 current architecture.
21229 A Python long is converted to the C @code{long long} type for the
21230 current architecture.
21233 A Python float is converted to the C @code{double} type for the
21234 current architecture.
21236 @item Python string
21237 A Python string is converted to a target string, using the current
21240 @item @code{gdb.Value}
21241 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21243 @item @code{gdb.LazyString}
21244 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21245 Python}), then the lazy string's @code{value} method is called, and
21246 its result is used.
21250 @defmethod Value cast type
21251 Return a new instance of @code{gdb.Value} that is the result of
21252 casting this instance to the type described by @var{type}, which must
21253 be a @code{gdb.Type} object. If the cast cannot be performed for some
21254 reason, this method throws an exception.
21257 @defmethod Value dereference
21258 For pointer data types, this method returns a new @code{gdb.Value} object
21259 whose contents is the object pointed to by the pointer. For example, if
21260 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21267 then you can use the corresponding @code{gdb.Value} to access what
21268 @code{foo} points to like this:
21271 bar = foo.dereference ()
21274 The result @code{bar} will be a @code{gdb.Value} object holding the
21275 value pointed to by @code{foo}.
21278 @defmethod Value dynamic_cast type
21279 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21280 operator were used. Consult a C@t{++} reference for details.
21283 @defmethod Value reinterpret_cast type
21284 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21285 operator were used. Consult a C@t{++} reference for details.
21288 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21289 If this @code{gdb.Value} represents a string, then this method
21290 converts the contents to a Python string. Otherwise, this method will
21291 throw an exception.
21293 Strings are recognized in a language-specific way; whether a given
21294 @code{gdb.Value} represents a string is determined by the current
21297 For C-like languages, a value is a string if it is a pointer to or an
21298 array of characters or ints. The string is assumed to be terminated
21299 by a zero of the appropriate width. However if the optional length
21300 argument is given, the string will be converted to that given length,
21301 ignoring any embedded zeros that the string may contain.
21303 If the optional @var{encoding} argument is given, it must be a string
21304 naming the encoding of the string in the @code{gdb.Value}, such as
21305 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21306 the same encodings as the corresponding argument to Python's
21307 @code{string.decode} method, and the Python codec machinery will be used
21308 to convert the string. If @var{encoding} is not given, or if
21309 @var{encoding} is the empty string, then either the @code{target-charset}
21310 (@pxref{Character Sets}) will be used, or a language-specific encoding
21311 will be used, if the current language is able to supply one.
21313 The optional @var{errors} argument is the same as the corresponding
21314 argument to Python's @code{string.decode} method.
21316 If the optional @var{length} argument is given, the string will be
21317 fetched and converted to the given length.
21320 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21321 If this @code{gdb.Value} represents a string, then this method
21322 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21323 In Python}). Otherwise, this method will throw an exception.
21325 If the optional @var{encoding} argument is given, it must be a string
21326 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21327 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21328 @var{encoding} argument is an encoding that @value{GDBN} does
21329 recognize, @value{GDBN} will raise an error.
21331 When a lazy string is printed, the @value{GDBN} encoding machinery is
21332 used to convert the string during printing. If the optional
21333 @var{encoding} argument is not provided, or is an empty string,
21334 @value{GDBN} will automatically select the encoding most suitable for
21335 the string type. For further information on encoding in @value{GDBN}
21336 please see @ref{Character Sets}.
21338 If the optional @var{length} argument is given, the string will be
21339 fetched and encoded to the length of characters specified. If
21340 the @var{length} argument is not provided, the string will be fetched
21341 and encoded until a null of appropriate width is found.
21345 @node Types In Python
21346 @subsubsection Types In Python
21347 @cindex types in Python
21348 @cindex Python, working with types
21351 @value{GDBN} represents types from the inferior using the class
21354 The following type-related functions are available in the @code{gdb}
21357 @findex gdb.lookup_type
21358 @defun lookup_type name [block]
21359 This function looks up a type by name. @var{name} is the name of the
21360 type to look up. It must be a string.
21362 If @var{block} is given, then @var{name} is looked up in that scope.
21363 Otherwise, it is searched for globally.
21365 Ordinarily, this function will return an instance of @code{gdb.Type}.
21366 If the named type cannot be found, it will throw an exception.
21369 An instance of @code{Type} has the following attributes:
21373 The type code for this type. The type code will be one of the
21374 @code{TYPE_CODE_} constants defined below.
21377 @defivar Type sizeof
21378 The size of this type, in target @code{char} units. Usually, a
21379 target's @code{char} type will be an 8-bit byte. However, on some
21380 unusual platforms, this type may have a different size.
21384 The tag name for this type. The tag name is the name after
21385 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21386 languages have this concept. If this type has no tag name, then
21387 @code{None} is returned.
21391 The following methods are provided:
21394 @defmethod Type fields
21395 For structure and union types, this method returns the fields. Range
21396 types have two fields, the minimum and maximum values. Enum types
21397 have one field per enum constant. Function and method types have one
21398 field per parameter. The base types of C@t{++} classes are also
21399 represented as fields. If the type has no fields, or does not fit
21400 into one of these categories, an empty sequence will be returned.
21402 Each field is an object, with some pre-defined attributes:
21405 This attribute is not available for @code{static} fields (as in
21406 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21407 position of the field.
21410 The name of the field, or @code{None} for anonymous fields.
21413 This is @code{True} if the field is artificial, usually meaning that
21414 it was provided by the compiler and not the user. This attribute is
21415 always provided, and is @code{False} if the field is not artificial.
21417 @item is_base_class
21418 This is @code{True} if the field represents a base class of a C@t{++}
21419 structure. This attribute is always provided, and is @code{False}
21420 if the field is not a base class of the type that is the argument of
21421 @code{fields}, or if that type was not a C@t{++} class.
21424 If the field is packed, or is a bitfield, then this will have a
21425 non-zero value, which is the size of the field in bits. Otherwise,
21426 this will be zero; in this case the field's size is given by its type.
21429 The type of the field. This is usually an instance of @code{Type},
21430 but it can be @code{None} in some situations.
21434 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21435 Return a new @code{gdb.Type} object which represents an array of this
21436 type. If one argument is given, it is the inclusive upper bound of
21437 the array; in this case the lower bound is zero. If two arguments are
21438 given, the first argument is the lower bound of the array, and the
21439 second argument is the upper bound of the array. An array's length
21440 must not be negative, but the bounds can be.
21443 @defmethod Type const
21444 Return a new @code{gdb.Type} object which represents a
21445 @code{const}-qualified variant of this type.
21448 @defmethod Type volatile
21449 Return a new @code{gdb.Type} object which represents a
21450 @code{volatile}-qualified variant of this type.
21453 @defmethod Type unqualified
21454 Return a new @code{gdb.Type} object which represents an unqualified
21455 variant of this type. That is, the result is neither @code{const} nor
21459 @defmethod Type range
21460 Return a Python @code{Tuple} object that contains two elements: the
21461 low bound of the argument type and the high bound of that type. If
21462 the type does not have a range, @value{GDBN} will raise a
21463 @code{gdb.error} exception (@pxref{Exception Handling}).
21466 @defmethod Type reference
21467 Return a new @code{gdb.Type} object which represents a reference to this
21471 @defmethod Type pointer
21472 Return a new @code{gdb.Type} object which represents a pointer to this
21476 @defmethod Type strip_typedefs
21477 Return a new @code{gdb.Type} that represents the real type,
21478 after removing all layers of typedefs.
21481 @defmethod Type target
21482 Return a new @code{gdb.Type} object which represents the target type
21485 For a pointer type, the target type is the type of the pointed-to
21486 object. For an array type (meaning C-like arrays), the target type is
21487 the type of the elements of the array. For a function or method type,
21488 the target type is the type of the return value. For a complex type,
21489 the target type is the type of the elements. For a typedef, the
21490 target type is the aliased type.
21492 If the type does not have a target, this method will throw an
21496 @defmethod Type template_argument n [block]
21497 If this @code{gdb.Type} is an instantiation of a template, this will
21498 return a new @code{gdb.Type} which represents the type of the
21499 @var{n}th template argument.
21501 If this @code{gdb.Type} is not a template type, this will throw an
21502 exception. Ordinarily, only C@t{++} code will have template types.
21504 If @var{block} is given, then @var{name} is looked up in that scope.
21505 Otherwise, it is searched for globally.
21510 Each type has a code, which indicates what category this type falls
21511 into. The available type categories are represented by constants
21512 defined in the @code{gdb} module:
21515 @findex TYPE_CODE_PTR
21516 @findex gdb.TYPE_CODE_PTR
21517 @item TYPE_CODE_PTR
21518 The type is a pointer.
21520 @findex TYPE_CODE_ARRAY
21521 @findex gdb.TYPE_CODE_ARRAY
21522 @item TYPE_CODE_ARRAY
21523 The type is an array.
21525 @findex TYPE_CODE_STRUCT
21526 @findex gdb.TYPE_CODE_STRUCT
21527 @item TYPE_CODE_STRUCT
21528 The type is a structure.
21530 @findex TYPE_CODE_UNION
21531 @findex gdb.TYPE_CODE_UNION
21532 @item TYPE_CODE_UNION
21533 The type is a union.
21535 @findex TYPE_CODE_ENUM
21536 @findex gdb.TYPE_CODE_ENUM
21537 @item TYPE_CODE_ENUM
21538 The type is an enum.
21540 @findex TYPE_CODE_FLAGS
21541 @findex gdb.TYPE_CODE_FLAGS
21542 @item TYPE_CODE_FLAGS
21543 A bit flags type, used for things such as status registers.
21545 @findex TYPE_CODE_FUNC
21546 @findex gdb.TYPE_CODE_FUNC
21547 @item TYPE_CODE_FUNC
21548 The type is a function.
21550 @findex TYPE_CODE_INT
21551 @findex gdb.TYPE_CODE_INT
21552 @item TYPE_CODE_INT
21553 The type is an integer type.
21555 @findex TYPE_CODE_FLT
21556 @findex gdb.TYPE_CODE_FLT
21557 @item TYPE_CODE_FLT
21558 A floating point type.
21560 @findex TYPE_CODE_VOID
21561 @findex gdb.TYPE_CODE_VOID
21562 @item TYPE_CODE_VOID
21563 The special type @code{void}.
21565 @findex TYPE_CODE_SET
21566 @findex gdb.TYPE_CODE_SET
21567 @item TYPE_CODE_SET
21570 @findex TYPE_CODE_RANGE
21571 @findex gdb.TYPE_CODE_RANGE
21572 @item TYPE_CODE_RANGE
21573 A range type, that is, an integer type with bounds.
21575 @findex TYPE_CODE_STRING
21576 @findex gdb.TYPE_CODE_STRING
21577 @item TYPE_CODE_STRING
21578 A string type. Note that this is only used for certain languages with
21579 language-defined string types; C strings are not represented this way.
21581 @findex TYPE_CODE_BITSTRING
21582 @findex gdb.TYPE_CODE_BITSTRING
21583 @item TYPE_CODE_BITSTRING
21586 @findex TYPE_CODE_ERROR
21587 @findex gdb.TYPE_CODE_ERROR
21588 @item TYPE_CODE_ERROR
21589 An unknown or erroneous type.
21591 @findex TYPE_CODE_METHOD
21592 @findex gdb.TYPE_CODE_METHOD
21593 @item TYPE_CODE_METHOD
21594 A method type, as found in C@t{++} or Java.
21596 @findex TYPE_CODE_METHODPTR
21597 @findex gdb.TYPE_CODE_METHODPTR
21598 @item TYPE_CODE_METHODPTR
21599 A pointer-to-member-function.
21601 @findex TYPE_CODE_MEMBERPTR
21602 @findex gdb.TYPE_CODE_MEMBERPTR
21603 @item TYPE_CODE_MEMBERPTR
21604 A pointer-to-member.
21606 @findex TYPE_CODE_REF
21607 @findex gdb.TYPE_CODE_REF
21608 @item TYPE_CODE_REF
21611 @findex TYPE_CODE_CHAR
21612 @findex gdb.TYPE_CODE_CHAR
21613 @item TYPE_CODE_CHAR
21616 @findex TYPE_CODE_BOOL
21617 @findex gdb.TYPE_CODE_BOOL
21618 @item TYPE_CODE_BOOL
21621 @findex TYPE_CODE_COMPLEX
21622 @findex gdb.TYPE_CODE_COMPLEX
21623 @item TYPE_CODE_COMPLEX
21624 A complex float type.
21626 @findex TYPE_CODE_TYPEDEF
21627 @findex gdb.TYPE_CODE_TYPEDEF
21628 @item TYPE_CODE_TYPEDEF
21629 A typedef to some other type.
21631 @findex TYPE_CODE_NAMESPACE
21632 @findex gdb.TYPE_CODE_NAMESPACE
21633 @item TYPE_CODE_NAMESPACE
21634 A C@t{++} namespace.
21636 @findex TYPE_CODE_DECFLOAT
21637 @findex gdb.TYPE_CODE_DECFLOAT
21638 @item TYPE_CODE_DECFLOAT
21639 A decimal floating point type.
21641 @findex TYPE_CODE_INTERNAL_FUNCTION
21642 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21643 @item TYPE_CODE_INTERNAL_FUNCTION
21644 A function internal to @value{GDBN}. This is the type used to represent
21645 convenience functions.
21648 Further support for types is provided in the @code{gdb.types}
21649 Python module (@pxref{gdb.types}).
21651 @node Pretty Printing API
21652 @subsubsection Pretty Printing API
21654 An example output is provided (@pxref{Pretty Printing}).
21656 A pretty-printer is just an object that holds a value and implements a
21657 specific interface, defined here.
21659 @defop Operation {pretty printer} children (self)
21660 @value{GDBN} will call this method on a pretty-printer to compute the
21661 children of the pretty-printer's value.
21663 This method must return an object conforming to the Python iterator
21664 protocol. Each item returned by the iterator must be a tuple holding
21665 two elements. The first element is the ``name'' of the child; the
21666 second element is the child's value. The value can be any Python
21667 object which is convertible to a @value{GDBN} value.
21669 This method is optional. If it does not exist, @value{GDBN} will act
21670 as though the value has no children.
21673 @defop Operation {pretty printer} display_hint (self)
21674 The CLI may call this method and use its result to change the
21675 formatting of a value. The result will also be supplied to an MI
21676 consumer as a @samp{displayhint} attribute of the variable being
21679 This method is optional. If it does exist, this method must return a
21682 Some display hints are predefined by @value{GDBN}:
21686 Indicate that the object being printed is ``array-like''. The CLI
21687 uses this to respect parameters such as @code{set print elements} and
21688 @code{set print array}.
21691 Indicate that the object being printed is ``map-like'', and that the
21692 children of this value can be assumed to alternate between keys and
21696 Indicate that the object being printed is ``string-like''. If the
21697 printer's @code{to_string} method returns a Python string of some
21698 kind, then @value{GDBN} will call its internal language-specific
21699 string-printing function to format the string. For the CLI this means
21700 adding quotation marks, possibly escaping some characters, respecting
21701 @code{set print elements}, and the like.
21705 @defop Operation {pretty printer} to_string (self)
21706 @value{GDBN} will call this method to display the string
21707 representation of the value passed to the object's constructor.
21709 When printing from the CLI, if the @code{to_string} method exists,
21710 then @value{GDBN} will prepend its result to the values returned by
21711 @code{children}. Exactly how this formatting is done is dependent on
21712 the display hint, and may change as more hints are added. Also,
21713 depending on the print settings (@pxref{Print Settings}), the CLI may
21714 print just the result of @code{to_string} in a stack trace, omitting
21715 the result of @code{children}.
21717 If this method returns a string, it is printed verbatim.
21719 Otherwise, if this method returns an instance of @code{gdb.Value},
21720 then @value{GDBN} prints this value. This may result in a call to
21721 another pretty-printer.
21723 If instead the method returns a Python value which is convertible to a
21724 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21725 the resulting value. Again, this may result in a call to another
21726 pretty-printer. Python scalars (integers, floats, and booleans) and
21727 strings are convertible to @code{gdb.Value}; other types are not.
21729 Finally, if this method returns @code{None} then no further operations
21730 are peformed in this method and nothing is printed.
21732 If the result is not one of these types, an exception is raised.
21735 @value{GDBN} provides a function which can be used to look up the
21736 default pretty-printer for a @code{gdb.Value}:
21738 @findex gdb.default_visualizer
21739 @defun default_visualizer value
21740 This function takes a @code{gdb.Value} object as an argument. If a
21741 pretty-printer for this value exists, then it is returned. If no such
21742 printer exists, then this returns @code{None}.
21745 @node Selecting Pretty-Printers
21746 @subsubsection Selecting Pretty-Printers
21748 The Python list @code{gdb.pretty_printers} contains an array of
21749 functions or callable objects that have been registered via addition
21750 as a pretty-printer. Printers in this list are called @code{global}
21751 printers, they're available when debugging all inferiors.
21752 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21753 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21756 Each function on these lists is passed a single @code{gdb.Value}
21757 argument and should return a pretty-printer object conforming to the
21758 interface definition above (@pxref{Pretty Printing API}). If a function
21759 cannot create a pretty-printer for the value, it should return
21762 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21763 @code{gdb.Objfile} in the current program space and iteratively calls
21764 each enabled lookup routine in the list for that @code{gdb.Objfile}
21765 until it receives a pretty-printer object.
21766 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21767 searches the pretty-printer list of the current program space,
21768 calling each enabled function until an object is returned.
21769 After these lists have been exhausted, it tries the global
21770 @code{gdb.pretty_printers} list, again calling each enabled function until an
21771 object is returned.
21773 The order in which the objfiles are searched is not specified. For a
21774 given list, functions are always invoked from the head of the list,
21775 and iterated over sequentially until the end of the list, or a printer
21776 object is returned.
21778 For various reasons a pretty-printer may not work.
21779 For example, the underlying data structure may have changed and
21780 the pretty-printer is out of date.
21782 The consequences of a broken pretty-printer are severe enough that
21783 @value{GDBN} provides support for enabling and disabling individual
21784 printers. For example, if @code{print frame-arguments} is on,
21785 a backtrace can become highly illegible if any argument is printed
21786 with a broken printer.
21788 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21789 attribute to the registered function or callable object. If this attribute
21790 is present and its value is @code{False}, the printer is disabled, otherwise
21791 the printer is enabled.
21793 @node Writing a Pretty-Printer
21794 @subsubsection Writing a Pretty-Printer
21795 @cindex writing a pretty-printer
21797 A pretty-printer consists of two parts: a lookup function to detect
21798 if the type is supported, and the printer itself.
21800 Here is an example showing how a @code{std::string} printer might be
21801 written. @xref{Pretty Printing API}, for details on the API this class
21805 class StdStringPrinter(object):
21806 "Print a std::string"
21808 def __init__(self, val):
21811 def to_string(self):
21812 return self.val['_M_dataplus']['_M_p']
21814 def display_hint(self):
21818 And here is an example showing how a lookup function for the printer
21819 example above might be written.
21822 def str_lookup_function(val):
21823 lookup_tag = val.type.tag
21824 if lookup_tag == None:
21826 regex = re.compile("^std::basic_string<char,.*>$")
21827 if regex.match(lookup_tag):
21828 return StdStringPrinter(val)
21832 The example lookup function extracts the value's type, and attempts to
21833 match it to a type that it can pretty-print. If it is a type the
21834 printer can pretty-print, it will return a printer object. If not, it
21835 returns @code{None}.
21837 We recommend that you put your core pretty-printers into a Python
21838 package. If your pretty-printers are for use with a library, we
21839 further recommend embedding a version number into the package name.
21840 This practice will enable @value{GDBN} to load multiple versions of
21841 your pretty-printers at the same time, because they will have
21844 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21845 can be evaluated multiple times without changing its meaning. An
21846 ideal auto-load file will consist solely of @code{import}s of your
21847 printer modules, followed by a call to a register pretty-printers with
21848 the current objfile.
21850 Taken as a whole, this approach will scale nicely to multiple
21851 inferiors, each potentially using a different library version.
21852 Embedding a version number in the Python package name will ensure that
21853 @value{GDBN} is able to load both sets of printers simultaneously.
21854 Then, because the search for pretty-printers is done by objfile, and
21855 because your auto-loaded code took care to register your library's
21856 printers with a specific objfile, @value{GDBN} will find the correct
21857 printers for the specific version of the library used by each
21860 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21861 this code might appear in @code{gdb.libstdcxx.v6}:
21864 def register_printers(objfile):
21865 objfile.pretty_printers.add(str_lookup_function)
21869 And then the corresponding contents of the auto-load file would be:
21872 import gdb.libstdcxx.v6
21873 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21876 The previous example illustrates a basic pretty-printer.
21877 There are a few things that can be improved on.
21878 The printer doesn't have a name, making it hard to identify in a
21879 list of installed printers. The lookup function has a name, but
21880 lookup functions can have arbitrary, even identical, names.
21882 Second, the printer only handles one type, whereas a library typically has
21883 several types. One could install a lookup function for each desired type
21884 in the library, but one could also have a single lookup function recognize
21885 several types. The latter is the conventional way this is handled.
21886 If a pretty-printer can handle multiple data types, then its
21887 @dfn{subprinters} are the printers for the individual data types.
21889 The @code{gdb.printing} module provides a formal way of solving these
21890 problems (@pxref{gdb.printing}).
21891 Here is another example that handles multiple types.
21893 These are the types we are going to pretty-print:
21896 struct foo @{ int a, b; @};
21897 struct bar @{ struct foo x, y; @};
21900 Here are the printers:
21904 """Print a foo object."""
21906 def __init__(self, val):
21909 def to_string(self):
21910 return ("a=<" + str(self.val["a"]) +
21911 "> b=<" + str(self.val["b"]) + ">")
21914 """Print a bar object."""
21916 def __init__(self, val):
21919 def to_string(self):
21920 return ("x=<" + str(self.val["x"]) +
21921 "> y=<" + str(self.val["y"]) + ">")
21924 This example doesn't need a lookup function, that is handled by the
21925 @code{gdb.printing} module. Instead a function is provided to build up
21926 the object that handles the lookup.
21929 import gdb.printing
21931 def build_pretty_printer():
21932 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21934 pp.add_printer('foo', '^foo$', fooPrinter)
21935 pp.add_printer('bar', '^bar$', barPrinter)
21939 And here is the autoload support:
21942 import gdb.printing
21944 gdb.printing.register_pretty_printer(
21945 gdb.current_objfile(),
21946 my_library.build_pretty_printer())
21949 Finally, when this printer is loaded into @value{GDBN}, here is the
21950 corresponding output of @samp{info pretty-printer}:
21953 (gdb) info pretty-printer
21960 @node Inferiors In Python
21961 @subsubsection Inferiors In Python
21962 @cindex inferiors in Python
21964 @findex gdb.Inferior
21965 Programs which are being run under @value{GDBN} are called inferiors
21966 (@pxref{Inferiors and Programs}). Python scripts can access
21967 information about and manipulate inferiors controlled by @value{GDBN}
21968 via objects of the @code{gdb.Inferior} class.
21970 The following inferior-related functions are available in the @code{gdb}
21974 Return a tuple containing all inferior objects.
21977 A @code{gdb.Inferior} object has the following attributes:
21980 @defivar Inferior num
21981 ID of inferior, as assigned by GDB.
21984 @defivar Inferior pid
21985 Process ID of the inferior, as assigned by the underlying operating
21989 @defivar Inferior was_attached
21990 Boolean signaling whether the inferior was created using `attach', or
21991 started by @value{GDBN} itself.
21995 A @code{gdb.Inferior} object has the following methods:
21998 @defmethod Inferior is_valid
21999 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22000 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22001 if the inferior no longer exists within @value{GDBN}. All other
22002 @code{gdb.Inferior} methods will throw an exception if it is invalid
22003 at the time the method is called.
22006 @defmethod Inferior threads
22007 This method returns a tuple holding all the threads which are valid
22008 when it is called. If there are no valid threads, the method will
22009 return an empty tuple.
22012 @findex gdb.read_memory
22013 @defmethod Inferior read_memory address length
22014 Read @var{length} bytes of memory from the inferior, starting at
22015 @var{address}. Returns a buffer object, which behaves much like an array
22016 or a string. It can be modified and given to the @code{gdb.write_memory}
22020 @findex gdb.write_memory
22021 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
22022 Write the contents of @var{buffer} to the inferior, starting at
22023 @var{address}. The @var{buffer} parameter must be a Python object
22024 which supports the buffer protocol, i.e., a string, an array or the
22025 object returned from @code{gdb.read_memory}. If given, @var{length}
22026 determines the number of bytes from @var{buffer} to be written.
22029 @findex gdb.search_memory
22030 @defmethod Inferior search_memory address length pattern
22031 Search a region of the inferior memory starting at @var{address} with
22032 the given @var{length} using the search pattern supplied in
22033 @var{pattern}. The @var{pattern} parameter must be a Python object
22034 which supports the buffer protocol, i.e., a string, an array or the
22035 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22036 containing the address where the pattern was found, or @code{None} if
22037 the pattern could not be found.
22041 @node Events In Python
22042 @subsubsection Events In Python
22043 @cindex inferior events in Python
22045 @value{GDBN} provides a general event facility so that Python code can be
22046 notified of various state changes, particularly changes that occur in
22049 An @dfn{event} is just an object that describes some state change. The
22050 type of the object and its attributes will vary depending on the details
22051 of the change. All the existing events are described below.
22053 In order to be notified of an event, you must register an event handler
22054 with an @dfn{event registry}. An event registry is an object in the
22055 @code{gdb.events} module which dispatches particular events. A registry
22056 provides methods to register and unregister event handlers:
22059 @defmethod EventRegistry connect object
22060 Add the given callable @var{object} to the registry. This object will be
22061 called when an event corresponding to this registry occurs.
22064 @defmethod EventRegistry disconnect object
22065 Remove the given @var{object} from the registry. Once removed, the object
22066 will no longer receive notifications of events.
22070 Here is an example:
22073 def exit_handler (event):
22074 print "event type: exit"
22075 print "exit code: %d" % (event.exit_code)
22077 gdb.events.exited.connect (exit_handler)
22080 In the above example we connect our handler @code{exit_handler} to the
22081 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22082 called when the inferior exits. The argument @dfn{event} in this example is
22083 of type @code{gdb.ExitedEvent}. As you can see in the example the
22084 @code{ExitedEvent} object has an attribute which indicates the exit code of
22087 The following is a listing of the event registries that are available and
22088 details of the events they emit:
22093 Emits @code{gdb.ThreadEvent}.
22095 Some events can be thread specific when @value{GDBN} is running in non-stop
22096 mode. When represented in Python, these events all extend
22097 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22098 events which are emitted by this or other modules might extend this event.
22099 Examples of these events are @code{gdb.BreakpointEvent} and
22100 @code{gdb.ContinueEvent}.
22103 @defivar ThreadEvent inferior_thread
22104 In non-stop mode this attribute will be set to the specific thread which was
22105 involved in the emitted event. Otherwise, it will be set to @code{None}.
22109 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22111 This event indicates that the inferior has been continued after a stop. For
22112 inherited attribute refer to @code{gdb.ThreadEvent} above.
22114 @item events.exited
22115 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22116 @code{events.ExitedEvent} has one attribute:
22118 @defivar ExitedEvent exit_code
22119 An integer representing the exit code which the inferior has returned.
22124 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22126 Indicates that the inferior has stopped. All events emitted by this registry
22127 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22128 will indicate the stopped thread when @value{GDBN} is running in non-stop
22129 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22131 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22133 This event indicates that the inferior or one of its threads has received as
22134 signal. @code{gdb.SignalEvent} has the following attributes:
22137 @defivar SignalEvent stop_signal
22138 A string representing the signal received by the inferior. A list of possible
22139 signal values can be obtained by running the command @code{info signals} in
22140 the @value{GDBN} command prompt.
22144 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22146 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22147 has the following attributes:
22150 @defivar BreakpointEvent breakpoint
22151 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22152 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22158 @node Threads In Python
22159 @subsubsection Threads In Python
22160 @cindex threads in python
22162 @findex gdb.InferiorThread
22163 Python scripts can access information about, and manipulate inferior threads
22164 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22166 The following thread-related functions are available in the @code{gdb}
22169 @findex gdb.selected_thread
22170 @defun selected_thread
22171 This function returns the thread object for the selected thread. If there
22172 is no selected thread, this will return @code{None}.
22175 A @code{gdb.InferiorThread} object has the following attributes:
22178 @defivar InferiorThread name
22179 The name of the thread. If the user specified a name using
22180 @code{thread name}, then this returns that name. Otherwise, if an
22181 OS-supplied name is available, then it is returned. Otherwise, this
22182 returns @code{None}.
22184 This attribute can be assigned to. The new value must be a string
22185 object, which sets the new name, or @code{None}, which removes any
22186 user-specified thread name.
22189 @defivar InferiorThread num
22190 ID of the thread, as assigned by GDB.
22193 @defivar InferiorThread ptid
22194 ID of the thread, as assigned by the operating system. This attribute is a
22195 tuple containing three integers. The first is the Process ID (PID); the second
22196 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22197 Either the LWPID or TID may be 0, which indicates that the operating system
22198 does not use that identifier.
22202 A @code{gdb.InferiorThread} object has the following methods:
22205 @defmethod InferiorThread is_valid
22206 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22207 @code{False} if not. A @code{gdb.InferiorThread} object will become
22208 invalid if the thread exits, or the inferior that the thread belongs
22209 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22210 exception if it is invalid at the time the method is called.
22213 @defmethod InferiorThread switch
22214 This changes @value{GDBN}'s currently selected thread to the one represented
22218 @defmethod InferiorThread is_stopped
22219 Return a Boolean indicating whether the thread is stopped.
22222 @defmethod InferiorThread is_running
22223 Return a Boolean indicating whether the thread is running.
22226 @defmethod InferiorThread is_exited
22227 Return a Boolean indicating whether the thread is exited.
22231 @node Commands In Python
22232 @subsubsection Commands In Python
22234 @cindex commands in python
22235 @cindex python commands
22236 You can implement new @value{GDBN} CLI commands in Python. A CLI
22237 command is implemented using an instance of the @code{gdb.Command}
22238 class, most commonly using a subclass.
22240 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22241 The object initializer for @code{Command} registers the new command
22242 with @value{GDBN}. This initializer is normally invoked from the
22243 subclass' own @code{__init__} method.
22245 @var{name} is the name of the command. If @var{name} consists of
22246 multiple words, then the initial words are looked for as prefix
22247 commands. In this case, if one of the prefix commands does not exist,
22248 an exception is raised.
22250 There is no support for multi-line commands.
22252 @var{command_class} should be one of the @samp{COMMAND_} constants
22253 defined below. This argument tells @value{GDBN} how to categorize the
22254 new command in the help system.
22256 @var{completer_class} is an optional argument. If given, it should be
22257 one of the @samp{COMPLETE_} constants defined below. This argument
22258 tells @value{GDBN} how to perform completion for this command. If not
22259 given, @value{GDBN} will attempt to complete using the object's
22260 @code{complete} method (see below); if no such method is found, an
22261 error will occur when completion is attempted.
22263 @var{prefix} is an optional argument. If @code{True}, then the new
22264 command is a prefix command; sub-commands of this command may be
22267 The help text for the new command is taken from the Python
22268 documentation string for the command's class, if there is one. If no
22269 documentation string is provided, the default value ``This command is
22270 not documented.'' is used.
22273 @cindex don't repeat Python command
22274 @defmethod Command dont_repeat
22275 By default, a @value{GDBN} command is repeated when the user enters a
22276 blank line at the command prompt. A command can suppress this
22277 behavior by invoking the @code{dont_repeat} method. This is similar
22278 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22281 @defmethod Command invoke argument from_tty
22282 This method is called by @value{GDBN} when this command is invoked.
22284 @var{argument} is a string. It is the argument to the command, after
22285 leading and trailing whitespace has been stripped.
22287 @var{from_tty} is a boolean argument. When true, this means that the
22288 command was entered by the user at the terminal; when false it means
22289 that the command came from elsewhere.
22291 If this method throws an exception, it is turned into a @value{GDBN}
22292 @code{error} call. Otherwise, the return value is ignored.
22294 @findex gdb.string_to_argv
22295 To break @var{argument} up into an argv-like string use
22296 @code{gdb.string_to_argv}. This function behaves identically to
22297 @value{GDBN}'s internal argument lexer @code{buildargv}.
22298 It is recommended to use this for consistency.
22299 Arguments are separated by spaces and may be quoted.
22303 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22304 ['1', '2 "3', '4 "5', "6 '7"]
22309 @cindex completion of Python commands
22310 @defmethod Command complete text word
22311 This method is called by @value{GDBN} when the user attempts
22312 completion on this command. All forms of completion are handled by
22313 this method, that is, the @key{TAB} and @key{M-?} key bindings
22314 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22317 The arguments @var{text} and @var{word} are both strings. @var{text}
22318 holds the complete command line up to the cursor's location.
22319 @var{word} holds the last word of the command line; this is computed
22320 using a word-breaking heuristic.
22322 The @code{complete} method can return several values:
22325 If the return value is a sequence, the contents of the sequence are
22326 used as the completions. It is up to @code{complete} to ensure that the
22327 contents actually do complete the word. A zero-length sequence is
22328 allowed, it means that there were no completions available. Only
22329 string elements of the sequence are used; other elements in the
22330 sequence are ignored.
22333 If the return value is one of the @samp{COMPLETE_} constants defined
22334 below, then the corresponding @value{GDBN}-internal completion
22335 function is invoked, and its result is used.
22338 All other results are treated as though there were no available
22343 When a new command is registered, it must be declared as a member of
22344 some general class of commands. This is used to classify top-level
22345 commands in the on-line help system; note that prefix commands are not
22346 listed under their own category but rather that of their top-level
22347 command. The available classifications are represented by constants
22348 defined in the @code{gdb} module:
22351 @findex COMMAND_NONE
22352 @findex gdb.COMMAND_NONE
22354 The command does not belong to any particular class. A command in
22355 this category will not be displayed in any of the help categories.
22357 @findex COMMAND_RUNNING
22358 @findex gdb.COMMAND_RUNNING
22359 @item COMMAND_RUNNING
22360 The command is related to running the inferior. For example,
22361 @code{start}, @code{step}, and @code{continue} are in this category.
22362 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22363 commands in this category.
22365 @findex COMMAND_DATA
22366 @findex gdb.COMMAND_DATA
22368 The command is related to data or variables. For example,
22369 @code{call}, @code{find}, and @code{print} are in this category. Type
22370 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22373 @findex COMMAND_STACK
22374 @findex gdb.COMMAND_STACK
22375 @item COMMAND_STACK
22376 The command has to do with manipulation of the stack. For example,
22377 @code{backtrace}, @code{frame}, and @code{return} are in this
22378 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22379 list of commands in this category.
22381 @findex COMMAND_FILES
22382 @findex gdb.COMMAND_FILES
22383 @item COMMAND_FILES
22384 This class is used for file-related commands. For example,
22385 @code{file}, @code{list} and @code{section} are in this category.
22386 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22387 commands in this category.
22389 @findex COMMAND_SUPPORT
22390 @findex gdb.COMMAND_SUPPORT
22391 @item COMMAND_SUPPORT
22392 This should be used for ``support facilities'', generally meaning
22393 things that are useful to the user when interacting with @value{GDBN},
22394 but not related to the state of the inferior. For example,
22395 @code{help}, @code{make}, and @code{shell} are in this category. Type
22396 @kbd{help support} at the @value{GDBN} prompt to see a list of
22397 commands in this category.
22399 @findex COMMAND_STATUS
22400 @findex gdb.COMMAND_STATUS
22401 @item COMMAND_STATUS
22402 The command is an @samp{info}-related command, that is, related to the
22403 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22404 and @code{show} are in this category. Type @kbd{help status} at the
22405 @value{GDBN} prompt to see a list of commands in this category.
22407 @findex COMMAND_BREAKPOINTS
22408 @findex gdb.COMMAND_BREAKPOINTS
22409 @item COMMAND_BREAKPOINTS
22410 The command has to do with breakpoints. For example, @code{break},
22411 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22412 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22415 @findex COMMAND_TRACEPOINTS
22416 @findex gdb.COMMAND_TRACEPOINTS
22417 @item COMMAND_TRACEPOINTS
22418 The command has to do with tracepoints. For example, @code{trace},
22419 @code{actions}, and @code{tfind} are in this category. Type
22420 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22421 commands in this category.
22423 @findex COMMAND_OBSCURE
22424 @findex gdb.COMMAND_OBSCURE
22425 @item COMMAND_OBSCURE
22426 The command is only used in unusual circumstances, or is not of
22427 general interest to users. For example, @code{checkpoint},
22428 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22429 obscure} at the @value{GDBN} prompt to see a list of commands in this
22432 @findex COMMAND_MAINTENANCE
22433 @findex gdb.COMMAND_MAINTENANCE
22434 @item COMMAND_MAINTENANCE
22435 The command is only useful to @value{GDBN} maintainers. The
22436 @code{maintenance} and @code{flushregs} commands are in this category.
22437 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22438 commands in this category.
22441 A new command can use a predefined completion function, either by
22442 specifying it via an argument at initialization, or by returning it
22443 from the @code{complete} method. These predefined completion
22444 constants are all defined in the @code{gdb} module:
22447 @findex COMPLETE_NONE
22448 @findex gdb.COMPLETE_NONE
22449 @item COMPLETE_NONE
22450 This constant means that no completion should be done.
22452 @findex COMPLETE_FILENAME
22453 @findex gdb.COMPLETE_FILENAME
22454 @item COMPLETE_FILENAME
22455 This constant means that filename completion should be performed.
22457 @findex COMPLETE_LOCATION
22458 @findex gdb.COMPLETE_LOCATION
22459 @item COMPLETE_LOCATION
22460 This constant means that location completion should be done.
22461 @xref{Specify Location}.
22463 @findex COMPLETE_COMMAND
22464 @findex gdb.COMPLETE_COMMAND
22465 @item COMPLETE_COMMAND
22466 This constant means that completion should examine @value{GDBN}
22469 @findex COMPLETE_SYMBOL
22470 @findex gdb.COMPLETE_SYMBOL
22471 @item COMPLETE_SYMBOL
22472 This constant means that completion should be done using symbol names
22476 The following code snippet shows how a trivial CLI command can be
22477 implemented in Python:
22480 class HelloWorld (gdb.Command):
22481 """Greet the whole world."""
22483 def __init__ (self):
22484 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22486 def invoke (self, arg, from_tty):
22487 print "Hello, World!"
22492 The last line instantiates the class, and is necessary to trigger the
22493 registration of the command with @value{GDBN}. Depending on how the
22494 Python code is read into @value{GDBN}, you may need to import the
22495 @code{gdb} module explicitly.
22497 @node Parameters In Python
22498 @subsubsection Parameters In Python
22500 @cindex parameters in python
22501 @cindex python parameters
22502 @tindex gdb.Parameter
22504 You can implement new @value{GDBN} parameters using Python. A new
22505 parameter is implemented as an instance of the @code{gdb.Parameter}
22508 Parameters are exposed to the user via the @code{set} and
22509 @code{show} commands. @xref{Help}.
22511 There are many parameters that already exist and can be set in
22512 @value{GDBN}. Two examples are: @code{set follow fork} and
22513 @code{set charset}. Setting these parameters influences certain
22514 behavior in @value{GDBN}. Similarly, you can define parameters that
22515 can be used to influence behavior in custom Python scripts and commands.
22517 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22518 The object initializer for @code{Parameter} registers the new
22519 parameter with @value{GDBN}. This initializer is normally invoked
22520 from the subclass' own @code{__init__} method.
22522 @var{name} is the name of the new parameter. If @var{name} consists
22523 of multiple words, then the initial words are looked for as prefix
22524 parameters. An example of this can be illustrated with the
22525 @code{set print} set of parameters. If @var{name} is
22526 @code{print foo}, then @code{print} will be searched as the prefix
22527 parameter. In this case the parameter can subsequently be accessed in
22528 @value{GDBN} as @code{set print foo}.
22530 If @var{name} consists of multiple words, and no prefix parameter group
22531 can be found, an exception is raised.
22533 @var{command-class} should be one of the @samp{COMMAND_} constants
22534 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22535 categorize the new parameter in the help system.
22537 @var{parameter-class} should be one of the @samp{PARAM_} constants
22538 defined below. This argument tells @value{GDBN} the type of the new
22539 parameter; this information is used for input validation and
22542 If @var{parameter-class} is @code{PARAM_ENUM}, then
22543 @var{enum-sequence} must be a sequence of strings. These strings
22544 represent the possible values for the parameter.
22546 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22547 of a fourth argument will cause an exception to be thrown.
22549 The help text for the new parameter is taken from the Python
22550 documentation string for the parameter's class, if there is one. If
22551 there is no documentation string, a default value is used.
22554 @defivar Parameter set_doc
22555 If this attribute exists, and is a string, then its value is used as
22556 the help text for this parameter's @code{set} command. The value is
22557 examined when @code{Parameter.__init__} is invoked; subsequent changes
22561 @defivar Parameter show_doc
22562 If this attribute exists, and is a string, then its value is used as
22563 the help text for this parameter's @code{show} command. The value is
22564 examined when @code{Parameter.__init__} is invoked; subsequent changes
22568 @defivar Parameter value
22569 The @code{value} attribute holds the underlying value of the
22570 parameter. It can be read and assigned to just as any other
22571 attribute. @value{GDBN} does validation when assignments are made.
22574 There are two methods that should be implemented in any
22575 @code{Parameter} class. These are:
22577 @defop Operation {parameter} get_set_string self
22578 @value{GDBN} will call this method when a @var{parameter}'s value has
22579 been changed via the @code{set} API (for example, @kbd{set foo off}).
22580 The @code{value} attribute has already been populated with the new
22581 value and may be used in output. This method must return a string.
22584 @defop Operation {parameter} get_show_string self svalue
22585 @value{GDBN} will call this method when a @var{parameter}'s
22586 @code{show} API has been invoked (for example, @kbd{show foo}). The
22587 argument @code{svalue} receives the string representation of the
22588 current value. This method must return a string.
22591 When a new parameter is defined, its type must be specified. The
22592 available types are represented by constants defined in the @code{gdb}
22596 @findex PARAM_BOOLEAN
22597 @findex gdb.PARAM_BOOLEAN
22598 @item PARAM_BOOLEAN
22599 The value is a plain boolean. The Python boolean values, @code{True}
22600 and @code{False} are the only valid values.
22602 @findex PARAM_AUTO_BOOLEAN
22603 @findex gdb.PARAM_AUTO_BOOLEAN
22604 @item PARAM_AUTO_BOOLEAN
22605 The value has three possible states: true, false, and @samp{auto}. In
22606 Python, true and false are represented using boolean constants, and
22607 @samp{auto} is represented using @code{None}.
22609 @findex PARAM_UINTEGER
22610 @findex gdb.PARAM_UINTEGER
22611 @item PARAM_UINTEGER
22612 The value is an unsigned integer. The value of 0 should be
22613 interpreted to mean ``unlimited''.
22615 @findex PARAM_INTEGER
22616 @findex gdb.PARAM_INTEGER
22617 @item PARAM_INTEGER
22618 The value is a signed integer. The value of 0 should be interpreted
22619 to mean ``unlimited''.
22621 @findex PARAM_STRING
22622 @findex gdb.PARAM_STRING
22624 The value is a string. When the user modifies the string, any escape
22625 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22626 translated into corresponding characters and encoded into the current
22629 @findex PARAM_STRING_NOESCAPE
22630 @findex gdb.PARAM_STRING_NOESCAPE
22631 @item PARAM_STRING_NOESCAPE
22632 The value is a string. When the user modifies the string, escapes are
22633 passed through untranslated.
22635 @findex PARAM_OPTIONAL_FILENAME
22636 @findex gdb.PARAM_OPTIONAL_FILENAME
22637 @item PARAM_OPTIONAL_FILENAME
22638 The value is a either a filename (a string), or @code{None}.
22640 @findex PARAM_FILENAME
22641 @findex gdb.PARAM_FILENAME
22642 @item PARAM_FILENAME
22643 The value is a filename. This is just like
22644 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22646 @findex PARAM_ZINTEGER
22647 @findex gdb.PARAM_ZINTEGER
22648 @item PARAM_ZINTEGER
22649 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22650 is interpreted as itself.
22653 @findex gdb.PARAM_ENUM
22655 The value is a string, which must be one of a collection string
22656 constants provided when the parameter is created.
22659 @node Functions In Python
22660 @subsubsection Writing new convenience functions
22662 @cindex writing convenience functions
22663 @cindex convenience functions in python
22664 @cindex python convenience functions
22665 @tindex gdb.Function
22667 You can implement new convenience functions (@pxref{Convenience Vars})
22668 in Python. A convenience function is an instance of a subclass of the
22669 class @code{gdb.Function}.
22671 @defmethod Function __init__ name
22672 The initializer for @code{Function} registers the new function with
22673 @value{GDBN}. The argument @var{name} is the name of the function,
22674 a string. The function will be visible to the user as a convenience
22675 variable of type @code{internal function}, whose name is the same as
22676 the given @var{name}.
22678 The documentation for the new function is taken from the documentation
22679 string for the new class.
22682 @defmethod Function invoke @var{*args}
22683 When a convenience function is evaluated, its arguments are converted
22684 to instances of @code{gdb.Value}, and then the function's
22685 @code{invoke} method is called. Note that @value{GDBN} does not
22686 predetermine the arity of convenience functions. Instead, all
22687 available arguments are passed to @code{invoke}, following the
22688 standard Python calling convention. In particular, a convenience
22689 function can have default values for parameters without ill effect.
22691 The return value of this method is used as its value in the enclosing
22692 expression. If an ordinary Python value is returned, it is converted
22693 to a @code{gdb.Value} following the usual rules.
22696 The following code snippet shows how a trivial convenience function can
22697 be implemented in Python:
22700 class Greet (gdb.Function):
22701 """Return string to greet someone.
22702 Takes a name as argument."""
22704 def __init__ (self):
22705 super (Greet, self).__init__ ("greet")
22707 def invoke (self, name):
22708 return "Hello, %s!" % name.string ()
22713 The last line instantiates the class, and is necessary to trigger the
22714 registration of the function with @value{GDBN}. Depending on how the
22715 Python code is read into @value{GDBN}, you may need to import the
22716 @code{gdb} module explicitly.
22718 @node Progspaces In Python
22719 @subsubsection Program Spaces In Python
22721 @cindex progspaces in python
22722 @tindex gdb.Progspace
22724 A program space, or @dfn{progspace}, represents a symbolic view
22725 of an address space.
22726 It consists of all of the objfiles of the program.
22727 @xref{Objfiles In Python}.
22728 @xref{Inferiors and Programs, program spaces}, for more details
22729 about program spaces.
22731 The following progspace-related functions are available in the
22734 @findex gdb.current_progspace
22735 @defun current_progspace
22736 This function returns the program space of the currently selected inferior.
22737 @xref{Inferiors and Programs}.
22740 @findex gdb.progspaces
22742 Return a sequence of all the progspaces currently known to @value{GDBN}.
22745 Each progspace is represented by an instance of the @code{gdb.Progspace}
22748 @defivar Progspace filename
22749 The file name of the progspace as a string.
22752 @defivar Progspace pretty_printers
22753 The @code{pretty_printers} attribute is a list of functions. It is
22754 used to look up pretty-printers. A @code{Value} is passed to each
22755 function in order; if the function returns @code{None}, then the
22756 search continues. Otherwise, the return value should be an object
22757 which is used to format the value. @xref{Pretty Printing API}, for more
22761 @node Objfiles In Python
22762 @subsubsection Objfiles In Python
22764 @cindex objfiles in python
22765 @tindex gdb.Objfile
22767 @value{GDBN} loads symbols for an inferior from various
22768 symbol-containing files (@pxref{Files}). These include the primary
22769 executable file, any shared libraries used by the inferior, and any
22770 separate debug info files (@pxref{Separate Debug Files}).
22771 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22773 The following objfile-related functions are available in the
22776 @findex gdb.current_objfile
22777 @defun current_objfile
22778 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22779 sets the ``current objfile'' to the corresponding objfile. This
22780 function returns the current objfile. If there is no current objfile,
22781 this function returns @code{None}.
22784 @findex gdb.objfiles
22786 Return a sequence of all the objfiles current known to @value{GDBN}.
22787 @xref{Objfiles In Python}.
22790 Each objfile is represented by an instance of the @code{gdb.Objfile}
22793 @defivar Objfile filename
22794 The file name of the objfile as a string.
22797 @defivar Objfile pretty_printers
22798 The @code{pretty_printers} attribute is a list of functions. It is
22799 used to look up pretty-printers. A @code{Value} is passed to each
22800 function in order; if the function returns @code{None}, then the
22801 search continues. Otherwise, the return value should be an object
22802 which is used to format the value. @xref{Pretty Printing API}, for more
22806 A @code{gdb.Objfile} object has the following methods:
22808 @defmethod Objfile is_valid
22809 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22810 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22811 if the object file it refers to is not loaded in @value{GDBN} any
22812 longer. All other @code{gdb.Objfile} methods will throw an exception
22813 if it is invalid at the time the method is called.
22816 @node Frames In Python
22817 @subsubsection Accessing inferior stack frames from Python.
22819 @cindex frames in python
22820 When the debugged program stops, @value{GDBN} is able to analyze its call
22821 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22822 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22823 while its corresponding frame exists in the inferior's stack. If you try
22824 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22825 exception (@pxref{Exception Handling}).
22827 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22831 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22835 The following frame-related functions are available in the @code{gdb} module:
22837 @findex gdb.selected_frame
22838 @defun selected_frame
22839 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22842 @findex gdb.newest_frame
22843 @defun newest_frame
22844 Return the newest frame object for the selected thread.
22847 @defun frame_stop_reason_string reason
22848 Return a string explaining the reason why @value{GDBN} stopped unwinding
22849 frames, as expressed by the given @var{reason} code (an integer, see the
22850 @code{unwind_stop_reason} method further down in this section).
22853 A @code{gdb.Frame} object has the following methods:
22856 @defmethod Frame is_valid
22857 Returns true if the @code{gdb.Frame} object is valid, false if not.
22858 A frame object can become invalid if the frame it refers to doesn't
22859 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22860 an exception if it is invalid at the time the method is called.
22863 @defmethod Frame name
22864 Returns the function name of the frame, or @code{None} if it can't be
22868 @defmethod Frame type
22869 Returns the type of the frame. The value can be one of:
22871 @item gdb.NORMAL_FRAME
22872 An ordinary stack frame.
22874 @item gdb.DUMMY_FRAME
22875 A fake stack frame that was created by @value{GDBN} when performing an
22876 inferior function call.
22878 @item gdb.INLINE_FRAME
22879 A frame representing an inlined function. The function was inlined
22880 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22882 @item gdb.SIGTRAMP_FRAME
22883 A signal trampoline frame. This is the frame created by the OS when
22884 it calls into a signal handler.
22886 @item gdb.ARCH_FRAME
22887 A fake stack frame representing a cross-architecture call.
22889 @item gdb.SENTINEL_FRAME
22890 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22895 @defmethod Frame unwind_stop_reason
22896 Return an integer representing the reason why it's not possible to find
22897 more frames toward the outermost frame. Use
22898 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22899 function to a string.
22902 @defmethod Frame pc
22903 Returns the frame's resume address.
22906 @defmethod Frame block
22907 Return the frame's code block. @xref{Blocks In Python}.
22910 @defmethod Frame function
22911 Return the symbol for the function corresponding to this frame.
22912 @xref{Symbols In Python}.
22915 @defmethod Frame older
22916 Return the frame that called this frame.
22919 @defmethod Frame newer
22920 Return the frame called by this frame.
22923 @defmethod Frame find_sal
22924 Return the frame's symtab and line object.
22925 @xref{Symbol Tables In Python}.
22928 @defmethod Frame read_var variable @r{[}block@r{]}
22929 Return the value of @var{variable} in this frame. If the optional
22930 argument @var{block} is provided, search for the variable from that
22931 block; otherwise start at the frame's current block (which is
22932 determined by the frame's current program counter). @var{variable}
22933 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22934 @code{gdb.Block} object.
22937 @defmethod Frame select
22938 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22943 @node Blocks In Python
22944 @subsubsection Accessing frame blocks from Python.
22946 @cindex blocks in python
22949 Within each frame, @value{GDBN} maintains information on each block
22950 stored in that frame. These blocks are organized hierarchically, and
22951 are represented individually in Python as a @code{gdb.Block}.
22952 Please see @ref{Frames In Python}, for a more in-depth discussion on
22953 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22954 detailed technical information on @value{GDBN}'s book-keeping of the
22957 The following block-related functions are available in the @code{gdb}
22960 @findex gdb.block_for_pc
22961 @defun block_for_pc pc
22962 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22963 block cannot be found for the @var{pc} value specified, the function
22964 will return @code{None}.
22967 A @code{gdb.Block} object has the following methods:
22970 @defmethod Block is_valid
22971 Returns @code{True} if the @code{gdb.Block} object is valid,
22972 @code{False} if not. A block object can become invalid if the block it
22973 refers to doesn't exist anymore in the inferior. All other
22974 @code{gdb.Block} methods will throw an exception if it is invalid at
22975 the time the method is called. This method is also made available to
22976 the Python iterator object that @code{gdb.Block} provides in an iteration
22977 context and via the Python @code{iter} built-in function.
22981 A @code{gdb.Block} object has the following attributes:
22984 @defivar Block start
22985 The start address of the block. This attribute is not writable.
22989 The end address of the block. This attribute is not writable.
22992 @defivar Block function
22993 The name of the block represented as a @code{gdb.Symbol}. If the
22994 block is not named, then this attribute holds @code{None}. This
22995 attribute is not writable.
22998 @defivar Block superblock
22999 The block containing this block. If this parent block does not exist,
23000 this attribute holds @code{None}. This attribute is not writable.
23004 @node Symbols In Python
23005 @subsubsection Python representation of Symbols.
23007 @cindex symbols in python
23010 @value{GDBN} represents every variable, function and type as an
23011 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23012 Similarly, Python represents these symbols in @value{GDBN} with the
23013 @code{gdb.Symbol} object.
23015 The following symbol-related functions are available in the @code{gdb}
23018 @findex gdb.lookup_symbol
23019 @defun lookup_symbol name @r{[}block@r{]} @r{[}domain@r{]}
23020 This function searches for a symbol by name. The search scope can be
23021 restricted to the parameters defined in the optional domain and block
23024 @var{name} is the name of the symbol. It must be a string. The
23025 optional @var{block} argument restricts the search to symbols visible
23026 in that @var{block}. The @var{block} argument must be a
23027 @code{gdb.Block} object. If omitted, the block for the current frame
23028 is used. The optional @var{domain} argument restricts
23029 the search to the domain type. The @var{domain} argument must be a
23030 domain constant defined in the @code{gdb} module and described later
23033 The result is a tuple of two elements.
23034 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23036 If the symbol is found, the second element is @code{True} if the symbol
23037 is a field of a method's object (e.g., @code{this} in C@t{++}),
23038 otherwise it is @code{False}.
23039 If the symbol is not found, the second element is @code{False}.
23042 @findex gdb.lookup_global_symbol
23043 @defun lookup_global_symbol name @r{[}domain@r{]}
23044 This function searches for a global symbol by name.
23045 The search scope can be restricted to by the domain argument.
23047 @var{name} is the name of the symbol. It must be a string.
23048 The optional @var{domain} argument restricts the search to the domain type.
23049 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23050 module and described later in this chapter.
23052 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23056 A @code{gdb.Symbol} object has the following attributes:
23059 @defivar Symbol symtab
23060 The symbol table in which the symbol appears. This attribute is
23061 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23062 Python}. This attribute is not writable.
23065 @defivar Symbol name
23066 The name of the symbol as a string. This attribute is not writable.
23069 @defivar Symbol linkage_name
23070 The name of the symbol, as used by the linker (i.e., may be mangled).
23071 This attribute is not writable.
23074 @defivar Symbol print_name
23075 The name of the symbol in a form suitable for output. This is either
23076 @code{name} or @code{linkage_name}, depending on whether the user
23077 asked @value{GDBN} to display demangled or mangled names.
23080 @defivar Symbol addr_class
23081 The address class of the symbol. This classifies how to find the value
23082 of a symbol. Each address class is a constant defined in the
23083 @code{gdb} module and described later in this chapter.
23086 @defivar Symbol is_argument
23087 @code{True} if the symbol is an argument of a function.
23090 @defivar Symbol is_constant
23091 @code{True} if the symbol is a constant.
23094 @defivar Symbol is_function
23095 @code{True} if the symbol is a function or a method.
23098 @defivar Symbol is_variable
23099 @code{True} if the symbol is a variable.
23103 A @code{gdb.Symbol} object has the following methods:
23106 @defmethod Symbol is_valid
23107 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23108 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23109 the symbol it refers to does not exist in @value{GDBN} any longer.
23110 All other @code{gdb.Symbol} methods will throw an exception if it is
23111 invalid at the time the method is called.
23115 The available domain categories in @code{gdb.Symbol} are represented
23116 as constants in the @code{gdb} module:
23119 @findex SYMBOL_UNDEF_DOMAIN
23120 @findex gdb.SYMBOL_UNDEF_DOMAIN
23121 @item SYMBOL_UNDEF_DOMAIN
23122 This is used when a domain has not been discovered or none of the
23123 following domains apply. This usually indicates an error either
23124 in the symbol information or in @value{GDBN}'s handling of symbols.
23125 @findex SYMBOL_VAR_DOMAIN
23126 @findex gdb.SYMBOL_VAR_DOMAIN
23127 @item SYMBOL_VAR_DOMAIN
23128 This domain contains variables, function names, typedef names and enum
23130 @findex SYMBOL_STRUCT_DOMAIN
23131 @findex gdb.SYMBOL_STRUCT_DOMAIN
23132 @item SYMBOL_STRUCT_DOMAIN
23133 This domain holds struct, union and enum type names.
23134 @findex SYMBOL_LABEL_DOMAIN
23135 @findex gdb.SYMBOL_LABEL_DOMAIN
23136 @item SYMBOL_LABEL_DOMAIN
23137 This domain contains names of labels (for gotos).
23138 @findex SYMBOL_VARIABLES_DOMAIN
23139 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23140 @item SYMBOL_VARIABLES_DOMAIN
23141 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23142 contains everything minus functions and types.
23143 @findex SYMBOL_FUNCTIONS_DOMAIN
23144 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23145 @item SYMBOL_FUNCTION_DOMAIN
23146 This domain contains all functions.
23147 @findex SYMBOL_TYPES_DOMAIN
23148 @findex gdb.SYMBOL_TYPES_DOMAIN
23149 @item SYMBOL_TYPES_DOMAIN
23150 This domain contains all types.
23153 The available address class categories in @code{gdb.Symbol} are represented
23154 as constants in the @code{gdb} module:
23157 @findex SYMBOL_LOC_UNDEF
23158 @findex gdb.SYMBOL_LOC_UNDEF
23159 @item SYMBOL_LOC_UNDEF
23160 If this is returned by address class, it indicates an error either in
23161 the symbol information or in @value{GDBN}'s handling of symbols.
23162 @findex SYMBOL_LOC_CONST
23163 @findex gdb.SYMBOL_LOC_CONST
23164 @item SYMBOL_LOC_CONST
23165 Value is constant int.
23166 @findex SYMBOL_LOC_STATIC
23167 @findex gdb.SYMBOL_LOC_STATIC
23168 @item SYMBOL_LOC_STATIC
23169 Value is at a fixed address.
23170 @findex SYMBOL_LOC_REGISTER
23171 @findex gdb.SYMBOL_LOC_REGISTER
23172 @item SYMBOL_LOC_REGISTER
23173 Value is in a register.
23174 @findex SYMBOL_LOC_ARG
23175 @findex gdb.SYMBOL_LOC_ARG
23176 @item SYMBOL_LOC_ARG
23177 Value is an argument. This value is at the offset stored within the
23178 symbol inside the frame's argument list.
23179 @findex SYMBOL_LOC_REF_ARG
23180 @findex gdb.SYMBOL_LOC_REF_ARG
23181 @item SYMBOL_LOC_REF_ARG
23182 Value address is stored in the frame's argument list. Just like
23183 @code{LOC_ARG} except that the value's address is stored at the
23184 offset, not the value itself.
23185 @findex SYMBOL_LOC_REGPARM_ADDR
23186 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23187 @item SYMBOL_LOC_REGPARM_ADDR
23188 Value is a specified register. Just like @code{LOC_REGISTER} except
23189 the register holds the address of the argument instead of the argument
23191 @findex SYMBOL_LOC_LOCAL
23192 @findex gdb.SYMBOL_LOC_LOCAL
23193 @item SYMBOL_LOC_LOCAL
23194 Value is a local variable.
23195 @findex SYMBOL_LOC_TYPEDEF
23196 @findex gdb.SYMBOL_LOC_TYPEDEF
23197 @item SYMBOL_LOC_TYPEDEF
23198 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23200 @findex SYMBOL_LOC_BLOCK
23201 @findex gdb.SYMBOL_LOC_BLOCK
23202 @item SYMBOL_LOC_BLOCK
23204 @findex SYMBOL_LOC_CONST_BYTES
23205 @findex gdb.SYMBOL_LOC_CONST_BYTES
23206 @item SYMBOL_LOC_CONST_BYTES
23207 Value is a byte-sequence.
23208 @findex SYMBOL_LOC_UNRESOLVED
23209 @findex gdb.SYMBOL_LOC_UNRESOLVED
23210 @item SYMBOL_LOC_UNRESOLVED
23211 Value is at a fixed address, but the address of the variable has to be
23212 determined from the minimal symbol table whenever the variable is
23214 @findex SYMBOL_LOC_OPTIMIZED_OUT
23215 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23216 @item SYMBOL_LOC_OPTIMIZED_OUT
23217 The value does not actually exist in the program.
23218 @findex SYMBOL_LOC_COMPUTED
23219 @findex gdb.SYMBOL_LOC_COMPUTED
23220 @item SYMBOL_LOC_COMPUTED
23221 The value's address is a computed location.
23224 @node Symbol Tables In Python
23225 @subsubsection Symbol table representation in Python.
23227 @cindex symbol tables in python
23229 @tindex gdb.Symtab_and_line
23231 Access to symbol table data maintained by @value{GDBN} on the inferior
23232 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23233 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23234 from the @code{find_sal} method in @code{gdb.Frame} object.
23235 @xref{Frames In Python}.
23237 For more information on @value{GDBN}'s symbol table management, see
23238 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23240 A @code{gdb.Symtab_and_line} object has the following attributes:
23243 @defivar Symtab_and_line symtab
23244 The symbol table object (@code{gdb.Symtab}) for this frame.
23245 This attribute is not writable.
23248 @defivar Symtab_and_line pc
23249 Indicates the current program counter address. This attribute is not
23253 @defivar Symtab_and_line line
23254 Indicates the current line number for this object. This
23255 attribute is not writable.
23259 A @code{gdb.Symtab_and_line} object has the following methods:
23262 @defmethod Symtab_and_line is_valid
23263 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23264 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23265 invalid if the Symbol table and line object it refers to does not
23266 exist in @value{GDBN} any longer. All other
23267 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23268 invalid at the time the method is called.
23272 A @code{gdb.Symtab} object has the following attributes:
23275 @defivar Symtab filename
23276 The symbol table's source filename. This attribute is not writable.
23279 @defivar Symtab objfile
23280 The symbol table's backing object file. @xref{Objfiles In Python}.
23281 This attribute is not writable.
23285 A @code{gdb.Symtab} object has the following methods:
23288 @defmethod Symtab is_valid
23289 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23290 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23291 the symbol table it refers to does not exist in @value{GDBN} any
23292 longer. All other @code{gdb.Symtab} methods will throw an exception
23293 if it is invalid at the time the method is called.
23296 @defmethod Symtab fullname
23297 Return the symbol table's source absolute file name.
23301 @node Breakpoints In Python
23302 @subsubsection Manipulating breakpoints using Python
23304 @cindex breakpoints in python
23305 @tindex gdb.Breakpoint
23307 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23310 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23311 Create a new breakpoint. @var{spec} is a string naming the
23312 location of the breakpoint, or an expression that defines a
23313 watchpoint. The contents can be any location recognized by the
23314 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23315 command. The optional @var{type} denotes the breakpoint to create
23316 from the types defined later in this chapter. This argument can be
23317 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23318 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23319 allows the breakpoint to become invisible to the user. The breakpoint
23320 will neither be reported when created, nor will it be listed in the
23321 output from @code{info breakpoints} (but will be listed with the
23322 @code{maint info breakpoints} command). The optional @var{wp_class}
23323 argument defines the class of watchpoint to create, if @var{type} is
23324 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23325 assumed to be a @var{WP_WRITE} class.
23328 @defop Operation {gdb.Breakpoint} stop (self)
23329 The @code{gdb.Breakpoint} class can be sub-classed and, in
23330 particular, you may choose to implement the @code{stop} method.
23331 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23332 it will be called when the inferior reaches any location of a
23333 breakpoint which instantiates that sub-class. If the method returns
23334 @code{True}, the inferior will be stopped at the location of the
23335 breakpoint, otherwise the inferior will continue.
23337 If there are multiple breakpoints at the same location with a
23338 @code{stop} method, each one will be called regardless of the
23339 return status of the previous. This ensures that all @code{stop}
23340 methods have a chance to execute at that location. In this scenario
23341 if one of the methods returns @code{True} but the others return
23342 @code{False}, the inferior will still be stopped.
23344 Example @code{stop} implementation:
23347 class MyBreakpoint (gdb.Breakpoint):
23349 inf_val = gdb.parse_and_eval("foo")
23356 The available watchpoint types represented by constants are defined in the
23361 @findex gdb.WP_READ
23363 Read only watchpoint.
23366 @findex gdb.WP_WRITE
23368 Write only watchpoint.
23371 @findex gdb.WP_ACCESS
23373 Read/Write watchpoint.
23376 @defmethod Breakpoint is_valid
23377 Return @code{True} if this @code{Breakpoint} object is valid,
23378 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23379 if the user deletes the breakpoint. In this case, the object still
23380 exists, but the underlying breakpoint does not. In the cases of
23381 watchpoint scope, the watchpoint remains valid even if execution of the
23382 inferior leaves the scope of that watchpoint.
23385 @defmethod Breakpoint delete
23386 Permanently deletes the @value{GDBN} breakpoint. This also
23387 invalidates the Python @code{Breakpoint} object. Any further access
23388 to this object's attributes or methods will raise an error.
23391 @defivar Breakpoint enabled
23392 This attribute is @code{True} if the breakpoint is enabled, and
23393 @code{False} otherwise. This attribute is writable.
23396 @defivar Breakpoint silent
23397 This attribute is @code{True} if the breakpoint is silent, and
23398 @code{False} otherwise. This attribute is writable.
23400 Note that a breakpoint can also be silent if it has commands and the
23401 first command is @code{silent}. This is not reported by the
23402 @code{silent} attribute.
23405 @defivar Breakpoint thread
23406 If the breakpoint is thread-specific, this attribute holds the thread
23407 id. If the breakpoint is not thread-specific, this attribute is
23408 @code{None}. This attribute is writable.
23411 @defivar Breakpoint task
23412 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23413 id. If the breakpoint is not task-specific (or the underlying
23414 language is not Ada), this attribute is @code{None}. This attribute
23418 @defivar Breakpoint ignore_count
23419 This attribute holds the ignore count for the breakpoint, an integer.
23420 This attribute is writable.
23423 @defivar Breakpoint number
23424 This attribute holds the breakpoint's number --- the identifier used by
23425 the user to manipulate the breakpoint. This attribute is not writable.
23428 @defivar Breakpoint type
23429 This attribute holds the breakpoint's type --- the identifier used to
23430 determine the actual breakpoint type or use-case. This attribute is not
23434 @defivar Breakpoint visible
23435 This attribute tells whether the breakpoint is visible to the user
23436 when set, or when the @samp{info breakpoints} command is run. This
23437 attribute is not writable.
23440 The available types are represented by constants defined in the @code{gdb}
23444 @findex BP_BREAKPOINT
23445 @findex gdb.BP_BREAKPOINT
23446 @item BP_BREAKPOINT
23447 Normal code breakpoint.
23449 @findex BP_WATCHPOINT
23450 @findex gdb.BP_WATCHPOINT
23451 @item BP_WATCHPOINT
23452 Watchpoint breakpoint.
23454 @findex BP_HARDWARE_WATCHPOINT
23455 @findex gdb.BP_HARDWARE_WATCHPOINT
23456 @item BP_HARDWARE_WATCHPOINT
23457 Hardware assisted watchpoint.
23459 @findex BP_READ_WATCHPOINT
23460 @findex gdb.BP_READ_WATCHPOINT
23461 @item BP_READ_WATCHPOINT
23462 Hardware assisted read watchpoint.
23464 @findex BP_ACCESS_WATCHPOINT
23465 @findex gdb.BP_ACCESS_WATCHPOINT
23466 @item BP_ACCESS_WATCHPOINT
23467 Hardware assisted access watchpoint.
23470 @defivar Breakpoint hit_count
23471 This attribute holds the hit count for the breakpoint, an integer.
23472 This attribute is writable, but currently it can only be set to zero.
23475 @defivar Breakpoint location
23476 This attribute holds the location of the breakpoint, as specified by
23477 the user. It is a string. If the breakpoint does not have a location
23478 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23479 attribute is not writable.
23482 @defivar Breakpoint expression
23483 This attribute holds a breakpoint expression, as specified by
23484 the user. It is a string. If the breakpoint does not have an
23485 expression (the breakpoint is not a watchpoint) the attribute's value
23486 is @code{None}. This attribute is not writable.
23489 @defivar Breakpoint condition
23490 This attribute holds the condition of the breakpoint, as specified by
23491 the user. It is a string. If there is no condition, this attribute's
23492 value is @code{None}. This attribute is writable.
23495 @defivar Breakpoint commands
23496 This attribute holds the commands attached to the breakpoint. If
23497 there are commands, this attribute's value is a string holding all the
23498 commands, separated by newlines. If there are no commands, this
23499 attribute is @code{None}. This attribute is not writable.
23502 @node Lazy Strings In Python
23503 @subsubsection Python representation of lazy strings.
23505 @cindex lazy strings in python
23506 @tindex gdb.LazyString
23508 A @dfn{lazy string} is a string whose contents is not retrieved or
23509 encoded until it is needed.
23511 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23512 @code{address} that points to a region of memory, an @code{encoding}
23513 that will be used to encode that region of memory, and a @code{length}
23514 to delimit the region of memory that represents the string. The
23515 difference between a @code{gdb.LazyString} and a string wrapped within
23516 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23517 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23518 retrieved and encoded during printing, while a @code{gdb.Value}
23519 wrapping a string is immediately retrieved and encoded on creation.
23521 A @code{gdb.LazyString} object has the following functions:
23523 @defmethod LazyString value
23524 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23525 will point to the string in memory, but will lose all the delayed
23526 retrieval, encoding and handling that @value{GDBN} applies to a
23527 @code{gdb.LazyString}.
23530 @defivar LazyString address
23531 This attribute holds the address of the string. This attribute is not
23535 @defivar LazyString length
23536 This attribute holds the length of the string in characters. If the
23537 length is -1, then the string will be fetched and encoded up to the
23538 first null of appropriate width. This attribute is not writable.
23541 @defivar LazyString encoding
23542 This attribute holds the encoding that will be applied to the string
23543 when the string is printed by @value{GDBN}. If the encoding is not
23544 set, or contains an empty string, then @value{GDBN} will select the
23545 most appropriate encoding when the string is printed. This attribute
23549 @defivar LazyString type
23550 This attribute holds the type that is represented by the lazy string's
23551 type. For a lazy string this will always be a pointer type. To
23552 resolve this to the lazy string's character type, use the type's
23553 @code{target} method. @xref{Types In Python}. This attribute is not
23558 @subsection Auto-loading
23559 @cindex auto-loading, Python
23561 When a new object file is read (for example, due to the @code{file}
23562 command, or because the inferior has loaded a shared library),
23563 @value{GDBN} will look for Python support scripts in several ways:
23564 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23567 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23568 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23569 * Which flavor to choose?::
23572 The auto-loading feature is useful for supplying application-specific
23573 debugging commands and scripts.
23575 Auto-loading can be enabled or disabled.
23578 @kindex set auto-load-scripts
23579 @item set auto-load-scripts [yes|no]
23580 Enable or disable the auto-loading of Python scripts.
23582 @kindex show auto-load-scripts
23583 @item show auto-load-scripts
23584 Show whether auto-loading of Python scripts is enabled or disabled.
23587 When reading an auto-loaded file, @value{GDBN} sets the
23588 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23589 function (@pxref{Objfiles In Python}). This can be useful for
23590 registering objfile-specific pretty-printers.
23592 @node objfile-gdb.py file
23593 @subsubsection The @file{@var{objfile}-gdb.py} file
23594 @cindex @file{@var{objfile}-gdb.py}
23596 When a new object file is read, @value{GDBN} looks for
23597 a file named @file{@var{objfile}-gdb.py},
23598 where @var{objfile} is the object file's real name, formed by ensuring
23599 that the file name is absolute, following all symlinks, and resolving
23600 @code{.} and @code{..} components. If this file exists and is
23601 readable, @value{GDBN} will evaluate it as a Python script.
23603 If this file does not exist, and if the parameter
23604 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23605 then @value{GDBN} will look for @var{real-name} in all of the
23606 directories mentioned in the value of @code{debug-file-directory}.
23608 Finally, if this file does not exist, then @value{GDBN} will look for
23609 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23610 @var{data-directory} is @value{GDBN}'s data directory (available via
23611 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23612 is the object file's real name, as described above.
23614 @value{GDBN} does not track which files it has already auto-loaded this way.
23615 @value{GDBN} will load the associated script every time the corresponding
23616 @var{objfile} is opened.
23617 So your @file{-gdb.py} file should be careful to avoid errors if it
23618 is evaluated more than once.
23620 @node .debug_gdb_scripts section
23621 @subsubsection The @code{.debug_gdb_scripts} section
23622 @cindex @code{.debug_gdb_scripts} section
23624 For systems using file formats like ELF and COFF,
23625 when @value{GDBN} loads a new object file
23626 it will look for a special section named @samp{.debug_gdb_scripts}.
23627 If this section exists, its contents is a list of names of scripts to load.
23629 @value{GDBN} will look for each specified script file first in the
23630 current directory and then along the source search path
23631 (@pxref{Source Path, ,Specifying Source Directories}),
23632 except that @file{$cdir} is not searched, since the compilation
23633 directory is not relevant to scripts.
23635 Entries can be placed in section @code{.debug_gdb_scripts} with,
23636 for example, this GCC macro:
23639 /* Note: The "MS" section flags are to remove duplicates. */
23640 #define DEFINE_GDB_SCRIPT(script_name) \
23642 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23644 .asciz \"" script_name "\"\n\
23650 Then one can reference the macro in a header or source file like this:
23653 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23656 The script name may include directories if desired.
23658 If the macro is put in a header, any application or library
23659 using this header will get a reference to the specified script.
23661 @node Which flavor to choose?
23662 @subsubsection Which flavor to choose?
23664 Given the multiple ways of auto-loading Python scripts, it might not always
23665 be clear which one to choose. This section provides some guidance.
23667 Benefits of the @file{-gdb.py} way:
23671 Can be used with file formats that don't support multiple sections.
23674 Ease of finding scripts for public libraries.
23676 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23677 in the source search path.
23678 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23679 isn't a source directory in which to find the script.
23682 Doesn't require source code additions.
23685 Benefits of the @code{.debug_gdb_scripts} way:
23689 Works with static linking.
23691 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23692 trigger their loading. When an application is statically linked the only
23693 objfile available is the executable, and it is cumbersome to attach all the
23694 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23697 Works with classes that are entirely inlined.
23699 Some classes can be entirely inlined, and thus there may not be an associated
23700 shared library to attach a @file{-gdb.py} script to.
23703 Scripts needn't be copied out of the source tree.
23705 In some circumstances, apps can be built out of large collections of internal
23706 libraries, and the build infrastructure necessary to install the
23707 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23708 cumbersome. It may be easier to specify the scripts in the
23709 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23710 top of the source tree to the source search path.
23713 @node Python modules
23714 @subsection Python modules
23715 @cindex python modules
23717 @value{GDBN} comes with a module to assist writing Python code.
23720 * gdb.printing:: Building and registering pretty-printers.
23721 * gdb.types:: Utilities for working with types.
23725 @subsubsection gdb.printing
23726 @cindex gdb.printing
23728 This module provides a collection of utilities for working with
23732 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23733 This class specifies the API that makes @samp{info pretty-printer},
23734 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23735 Pretty-printers should generally inherit from this class.
23737 @item SubPrettyPrinter (@var{name})
23738 For printers that handle multiple types, this class specifies the
23739 corresponding API for the subprinters.
23741 @item RegexpCollectionPrettyPrinter (@var{name})
23742 Utility class for handling multiple printers, all recognized via
23743 regular expressions.
23744 @xref{Writing a Pretty-Printer}, for an example.
23746 @item register_pretty_printer (@var{obj}, @var{printer})
23747 Register @var{printer} with the pretty-printer list of @var{obj}.
23751 @subsubsection gdb.types
23754 This module provides a collection of utilities for working with
23755 @code{gdb.Types} objects.
23758 @item get_basic_type (@var{type})
23759 Return @var{type} with const and volatile qualifiers stripped,
23760 and with typedefs and C@t{++} references converted to the underlying type.
23765 typedef const int const_int;
23767 const_int& foo_ref (foo);
23768 int main () @{ return 0; @}
23775 (gdb) python import gdb.types
23776 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23777 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23781 @item has_field (@var{type}, @var{field})
23782 Return @code{True} if @var{type}, assumed to be a type with fields
23783 (e.g., a structure or union), has field @var{field}.
23785 @item make_enum_dict (@var{enum_type})
23786 Return a Python @code{dictionary} type produced from @var{enum_type}.
23790 @chapter Command Interpreters
23791 @cindex command interpreters
23793 @value{GDBN} supports multiple command interpreters, and some command
23794 infrastructure to allow users or user interface writers to switch
23795 between interpreters or run commands in other interpreters.
23797 @value{GDBN} currently supports two command interpreters, the console
23798 interpreter (sometimes called the command-line interpreter or @sc{cli})
23799 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23800 describes both of these interfaces in great detail.
23802 By default, @value{GDBN} will start with the console interpreter.
23803 However, the user may choose to start @value{GDBN} with another
23804 interpreter by specifying the @option{-i} or @option{--interpreter}
23805 startup options. Defined interpreters include:
23809 @cindex console interpreter
23810 The traditional console or command-line interpreter. This is the most often
23811 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23812 @value{GDBN} will use this interpreter.
23815 @cindex mi interpreter
23816 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23817 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23818 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23822 @cindex mi2 interpreter
23823 The current @sc{gdb/mi} interface.
23826 @cindex mi1 interpreter
23827 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23831 @cindex invoke another interpreter
23832 The interpreter being used by @value{GDBN} may not be dynamically
23833 switched at runtime. Although possible, this could lead to a very
23834 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23835 enters the command "interpreter-set console" in a console view,
23836 @value{GDBN} would switch to using the console interpreter, rendering
23837 the IDE inoperable!
23839 @kindex interpreter-exec
23840 Although you may only choose a single interpreter at startup, you may execute
23841 commands in any interpreter from the current interpreter using the appropriate
23842 command. If you are running the console interpreter, simply use the
23843 @code{interpreter-exec} command:
23846 interpreter-exec mi "-data-list-register-names"
23849 @sc{gdb/mi} has a similar command, although it is only available in versions of
23850 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23853 @chapter @value{GDBN} Text User Interface
23855 @cindex Text User Interface
23858 * TUI Overview:: TUI overview
23859 * TUI Keys:: TUI key bindings
23860 * TUI Single Key Mode:: TUI single key mode
23861 * TUI Commands:: TUI-specific commands
23862 * TUI Configuration:: TUI configuration variables
23865 The @value{GDBN} Text User Interface (TUI) is a terminal
23866 interface which uses the @code{curses} library to show the source
23867 file, the assembly output, the program registers and @value{GDBN}
23868 commands in separate text windows. The TUI mode is supported only
23869 on platforms where a suitable version of the @code{curses} library
23872 @pindex @value{GDBTUI}
23873 The TUI mode is enabled by default when you invoke @value{GDBN} as
23874 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23875 You can also switch in and out of TUI mode while @value{GDBN} runs by
23876 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23877 @xref{TUI Keys, ,TUI Key Bindings}.
23880 @section TUI Overview
23882 In TUI mode, @value{GDBN} can display several text windows:
23886 This window is the @value{GDBN} command window with the @value{GDBN}
23887 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23888 managed using readline.
23891 The source window shows the source file of the program. The current
23892 line and active breakpoints are displayed in this window.
23895 The assembly window shows the disassembly output of the program.
23898 This window shows the processor registers. Registers are highlighted
23899 when their values change.
23902 The source and assembly windows show the current program position
23903 by highlighting the current line and marking it with a @samp{>} marker.
23904 Breakpoints are indicated with two markers. The first marker
23905 indicates the breakpoint type:
23909 Breakpoint which was hit at least once.
23912 Breakpoint which was never hit.
23915 Hardware breakpoint which was hit at least once.
23918 Hardware breakpoint which was never hit.
23921 The second marker indicates whether the breakpoint is enabled or not:
23925 Breakpoint is enabled.
23928 Breakpoint is disabled.
23931 The source, assembly and register windows are updated when the current
23932 thread changes, when the frame changes, or when the program counter
23935 These windows are not all visible at the same time. The command
23936 window is always visible. The others can be arranged in several
23947 source and assembly,
23950 source and registers, or
23953 assembly and registers.
23956 A status line above the command window shows the following information:
23960 Indicates the current @value{GDBN} target.
23961 (@pxref{Targets, ,Specifying a Debugging Target}).
23964 Gives the current process or thread number.
23965 When no process is being debugged, this field is set to @code{No process}.
23968 Gives the current function name for the selected frame.
23969 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23970 When there is no symbol corresponding to the current program counter,
23971 the string @code{??} is displayed.
23974 Indicates the current line number for the selected frame.
23975 When the current line number is not known, the string @code{??} is displayed.
23978 Indicates the current program counter address.
23982 @section TUI Key Bindings
23983 @cindex TUI key bindings
23985 The TUI installs several key bindings in the readline keymaps
23986 @ifset SYSTEM_READLINE
23987 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23989 @ifclear SYSTEM_READLINE
23990 (@pxref{Command Line Editing}).
23992 The following key bindings are installed for both TUI mode and the
23993 @value{GDBN} standard mode.
24002 Enter or leave the TUI mode. When leaving the TUI mode,
24003 the curses window management stops and @value{GDBN} operates using
24004 its standard mode, writing on the terminal directly. When reentering
24005 the TUI mode, control is given back to the curses windows.
24006 The screen is then refreshed.
24010 Use a TUI layout with only one window. The layout will
24011 either be @samp{source} or @samp{assembly}. When the TUI mode
24012 is not active, it will switch to the TUI mode.
24014 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24018 Use a TUI layout with at least two windows. When the current
24019 layout already has two windows, the next layout with two windows is used.
24020 When a new layout is chosen, one window will always be common to the
24021 previous layout and the new one.
24023 Think of it as the Emacs @kbd{C-x 2} binding.
24027 Change the active window. The TUI associates several key bindings
24028 (like scrolling and arrow keys) with the active window. This command
24029 gives the focus to the next TUI window.
24031 Think of it as the Emacs @kbd{C-x o} binding.
24035 Switch in and out of the TUI SingleKey mode that binds single
24036 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24039 The following key bindings only work in the TUI mode:
24044 Scroll the active window one page up.
24048 Scroll the active window one page down.
24052 Scroll the active window one line up.
24056 Scroll the active window one line down.
24060 Scroll the active window one column left.
24064 Scroll the active window one column right.
24068 Refresh the screen.
24071 Because the arrow keys scroll the active window in the TUI mode, they
24072 are not available for their normal use by readline unless the command
24073 window has the focus. When another window is active, you must use
24074 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24075 and @kbd{C-f} to control the command window.
24077 @node TUI Single Key Mode
24078 @section TUI Single Key Mode
24079 @cindex TUI single key mode
24081 The TUI also provides a @dfn{SingleKey} mode, which binds several
24082 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24083 switch into this mode, where the following key bindings are used:
24086 @kindex c @r{(SingleKey TUI key)}
24090 @kindex d @r{(SingleKey TUI key)}
24094 @kindex f @r{(SingleKey TUI key)}
24098 @kindex n @r{(SingleKey TUI key)}
24102 @kindex q @r{(SingleKey TUI key)}
24104 exit the SingleKey mode.
24106 @kindex r @r{(SingleKey TUI key)}
24110 @kindex s @r{(SingleKey TUI key)}
24114 @kindex u @r{(SingleKey TUI key)}
24118 @kindex v @r{(SingleKey TUI key)}
24122 @kindex w @r{(SingleKey TUI key)}
24127 Other keys temporarily switch to the @value{GDBN} command prompt.
24128 The key that was pressed is inserted in the editing buffer so that
24129 it is possible to type most @value{GDBN} commands without interaction
24130 with the TUI SingleKey mode. Once the command is entered the TUI
24131 SingleKey mode is restored. The only way to permanently leave
24132 this mode is by typing @kbd{q} or @kbd{C-x s}.
24136 @section TUI-specific Commands
24137 @cindex TUI commands
24139 The TUI has specific commands to control the text windows.
24140 These commands are always available, even when @value{GDBN} is not in
24141 the TUI mode. When @value{GDBN} is in the standard mode, most
24142 of these commands will automatically switch to the TUI mode.
24144 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24145 terminal, or @value{GDBN} has been started with the machine interface
24146 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24147 these commands will fail with an error, because it would not be
24148 possible or desirable to enable curses window management.
24153 List and give the size of all displayed windows.
24157 Display the next layout.
24160 Display the previous layout.
24163 Display the source window only.
24166 Display the assembly window only.
24169 Display the source and assembly window.
24172 Display the register window together with the source or assembly window.
24176 Make the next window active for scrolling.
24179 Make the previous window active for scrolling.
24182 Make the source window active for scrolling.
24185 Make the assembly window active for scrolling.
24188 Make the register window active for scrolling.
24191 Make the command window active for scrolling.
24195 Refresh the screen. This is similar to typing @kbd{C-L}.
24197 @item tui reg float
24199 Show the floating point registers in the register window.
24201 @item tui reg general
24202 Show the general registers in the register window.
24205 Show the next register group. The list of register groups as well as
24206 their order is target specific. The predefined register groups are the
24207 following: @code{general}, @code{float}, @code{system}, @code{vector},
24208 @code{all}, @code{save}, @code{restore}.
24210 @item tui reg system
24211 Show the system registers in the register window.
24215 Update the source window and the current execution point.
24217 @item winheight @var{name} +@var{count}
24218 @itemx winheight @var{name} -@var{count}
24220 Change the height of the window @var{name} by @var{count}
24221 lines. Positive counts increase the height, while negative counts
24224 @item tabset @var{nchars}
24226 Set the width of tab stops to be @var{nchars} characters.
24229 @node TUI Configuration
24230 @section TUI Configuration Variables
24231 @cindex TUI configuration variables
24233 Several configuration variables control the appearance of TUI windows.
24236 @item set tui border-kind @var{kind}
24237 @kindex set tui border-kind
24238 Select the border appearance for the source, assembly and register windows.
24239 The possible values are the following:
24242 Use a space character to draw the border.
24245 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24248 Use the Alternate Character Set to draw the border. The border is
24249 drawn using character line graphics if the terminal supports them.
24252 @item set tui border-mode @var{mode}
24253 @kindex set tui border-mode
24254 @itemx set tui active-border-mode @var{mode}
24255 @kindex set tui active-border-mode
24256 Select the display attributes for the borders of the inactive windows
24257 or the active window. The @var{mode} can be one of the following:
24260 Use normal attributes to display the border.
24266 Use reverse video mode.
24269 Use half bright mode.
24271 @item half-standout
24272 Use half bright and standout mode.
24275 Use extra bright or bold mode.
24277 @item bold-standout
24278 Use extra bright or bold and standout mode.
24283 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24286 @cindex @sc{gnu} Emacs
24287 A special interface allows you to use @sc{gnu} Emacs to view (and
24288 edit) the source files for the program you are debugging with
24291 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24292 executable file you want to debug as an argument. This command starts
24293 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24294 created Emacs buffer.
24295 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24297 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24302 All ``terminal'' input and output goes through an Emacs buffer, called
24305 This applies both to @value{GDBN} commands and their output, and to the input
24306 and output done by the program you are debugging.
24308 This is useful because it means that you can copy the text of previous
24309 commands and input them again; you can even use parts of the output
24312 All the facilities of Emacs' Shell mode are available for interacting
24313 with your program. In particular, you can send signals the usual
24314 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24318 @value{GDBN} displays source code through Emacs.
24320 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24321 source file for that frame and puts an arrow (@samp{=>}) at the
24322 left margin of the current line. Emacs uses a separate buffer for
24323 source display, and splits the screen to show both your @value{GDBN} session
24326 Explicit @value{GDBN} @code{list} or search commands still produce output as
24327 usual, but you probably have no reason to use them from Emacs.
24330 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24331 a graphical mode, enabled by default, which provides further buffers
24332 that can control the execution and describe the state of your program.
24333 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24335 If you specify an absolute file name when prompted for the @kbd{M-x
24336 gdb} argument, then Emacs sets your current working directory to where
24337 your program resides. If you only specify the file name, then Emacs
24338 sets your current working directory to the directory associated
24339 with the previous buffer. In this case, @value{GDBN} may find your
24340 program by searching your environment's @code{PATH} variable, but on
24341 some operating systems it might not find the source. So, although the
24342 @value{GDBN} input and output session proceeds normally, the auxiliary
24343 buffer does not display the current source and line of execution.
24345 The initial working directory of @value{GDBN} is printed on the top
24346 line of the GUD buffer and this serves as a default for the commands
24347 that specify files for @value{GDBN} to operate on. @xref{Files,
24348 ,Commands to Specify Files}.
24350 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24351 need to call @value{GDBN} by a different name (for example, if you
24352 keep several configurations around, with different names) you can
24353 customize the Emacs variable @code{gud-gdb-command-name} to run the
24356 In the GUD buffer, you can use these special Emacs commands in
24357 addition to the standard Shell mode commands:
24361 Describe the features of Emacs' GUD Mode.
24364 Execute to another source line, like the @value{GDBN} @code{step} command; also
24365 update the display window to show the current file and location.
24368 Execute to next source line in this function, skipping all function
24369 calls, like the @value{GDBN} @code{next} command. Then update the display window
24370 to show the current file and location.
24373 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24374 display window accordingly.
24377 Execute until exit from the selected stack frame, like the @value{GDBN}
24378 @code{finish} command.
24381 Continue execution of your program, like the @value{GDBN} @code{continue}
24385 Go up the number of frames indicated by the numeric argument
24386 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24387 like the @value{GDBN} @code{up} command.
24390 Go down the number of frames indicated by the numeric argument, like the
24391 @value{GDBN} @code{down} command.
24394 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24395 tells @value{GDBN} to set a breakpoint on the source line point is on.
24397 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24398 separate frame which shows a backtrace when the GUD buffer is current.
24399 Move point to any frame in the stack and type @key{RET} to make it
24400 become the current frame and display the associated source in the
24401 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24402 selected frame become the current one. In graphical mode, the
24403 speedbar displays watch expressions.
24405 If you accidentally delete the source-display buffer, an easy way to get
24406 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24407 request a frame display; when you run under Emacs, this recreates
24408 the source buffer if necessary to show you the context of the current
24411 The source files displayed in Emacs are in ordinary Emacs buffers
24412 which are visiting the source files in the usual way. You can edit
24413 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24414 communicates with Emacs in terms of line numbers. If you add or
24415 delete lines from the text, the line numbers that @value{GDBN} knows cease
24416 to correspond properly with the code.
24418 A more detailed description of Emacs' interaction with @value{GDBN} is
24419 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24422 @c The following dropped because Epoch is nonstandard. Reactivate
24423 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24425 @kindex Emacs Epoch environment
24429 Version 18 of @sc{gnu} Emacs has a built-in window system
24430 called the @code{epoch}
24431 environment. Users of this environment can use a new command,
24432 @code{inspect} which performs identically to @code{print} except that
24433 each value is printed in its own window.
24438 @chapter The @sc{gdb/mi} Interface
24440 @unnumberedsec Function and Purpose
24442 @cindex @sc{gdb/mi}, its purpose
24443 @sc{gdb/mi} is a line based machine oriented text interface to
24444 @value{GDBN} and is activated by specifying using the
24445 @option{--interpreter} command line option (@pxref{Mode Options}). It
24446 is specifically intended to support the development of systems which
24447 use the debugger as just one small component of a larger system.
24449 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24450 in the form of a reference manual.
24452 Note that @sc{gdb/mi} is still under construction, so some of the
24453 features described below are incomplete and subject to change
24454 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24456 @unnumberedsec Notation and Terminology
24458 @cindex notational conventions, for @sc{gdb/mi}
24459 This chapter uses the following notation:
24463 @code{|} separates two alternatives.
24466 @code{[ @var{something} ]} indicates that @var{something} is optional:
24467 it may or may not be given.
24470 @code{( @var{group} )*} means that @var{group} inside the parentheses
24471 may repeat zero or more times.
24474 @code{( @var{group} )+} means that @var{group} inside the parentheses
24475 may repeat one or more times.
24478 @code{"@var{string}"} means a literal @var{string}.
24482 @heading Dependencies
24486 * GDB/MI General Design::
24487 * GDB/MI Command Syntax::
24488 * GDB/MI Compatibility with CLI::
24489 * GDB/MI Development and Front Ends::
24490 * GDB/MI Output Records::
24491 * GDB/MI Simple Examples::
24492 * GDB/MI Command Description Format::
24493 * GDB/MI Breakpoint Commands::
24494 * GDB/MI Program Context::
24495 * GDB/MI Thread Commands::
24496 * GDB/MI Program Execution::
24497 * GDB/MI Stack Manipulation::
24498 * GDB/MI Variable Objects::
24499 * GDB/MI Data Manipulation::
24500 * GDB/MI Tracepoint Commands::
24501 * GDB/MI Symbol Query::
24502 * GDB/MI File Commands::
24504 * GDB/MI Kod Commands::
24505 * GDB/MI Memory Overlay Commands::
24506 * GDB/MI Signal Handling Commands::
24508 * GDB/MI Target Manipulation::
24509 * GDB/MI File Transfer Commands::
24510 * GDB/MI Miscellaneous Commands::
24513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24514 @node GDB/MI General Design
24515 @section @sc{gdb/mi} General Design
24516 @cindex GDB/MI General Design
24518 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24519 parts---commands sent to @value{GDBN}, responses to those commands
24520 and notifications. Each command results in exactly one response,
24521 indicating either successful completion of the command, or an error.
24522 For the commands that do not resume the target, the response contains the
24523 requested information. For the commands that resume the target, the
24524 response only indicates whether the target was successfully resumed.
24525 Notifications is the mechanism for reporting changes in the state of the
24526 target, or in @value{GDBN} state, that cannot conveniently be associated with
24527 a command and reported as part of that command response.
24529 The important examples of notifications are:
24533 Exec notifications. These are used to report changes in
24534 target state---when a target is resumed, or stopped. It would not
24535 be feasible to include this information in response of resuming
24536 commands, because one resume commands can result in multiple events in
24537 different threads. Also, quite some time may pass before any event
24538 happens in the target, while a frontend needs to know whether the resuming
24539 command itself was successfully executed.
24542 Console output, and status notifications. Console output
24543 notifications are used to report output of CLI commands, as well as
24544 diagnostics for other commands. Status notifications are used to
24545 report the progress of a long-running operation. Naturally, including
24546 this information in command response would mean no output is produced
24547 until the command is finished, which is undesirable.
24550 General notifications. Commands may have various side effects on
24551 the @value{GDBN} or target state beyond their official purpose. For example,
24552 a command may change the selected thread. Although such changes can
24553 be included in command response, using notification allows for more
24554 orthogonal frontend design.
24558 There's no guarantee that whenever an MI command reports an error,
24559 @value{GDBN} or the target are in any specific state, and especially,
24560 the state is not reverted to the state before the MI command was
24561 processed. Therefore, whenever an MI command results in an error,
24562 we recommend that the frontend refreshes all the information shown in
24563 the user interface.
24567 * Context management::
24568 * Asynchronous and non-stop modes::
24572 @node Context management
24573 @subsection Context management
24575 In most cases when @value{GDBN} accesses the target, this access is
24576 done in context of a specific thread and frame (@pxref{Frames}).
24577 Often, even when accessing global data, the target requires that a thread
24578 be specified. The CLI interface maintains the selected thread and frame,
24579 and supplies them to target on each command. This is convenient,
24580 because a command line user would not want to specify that information
24581 explicitly on each command, and because user interacts with
24582 @value{GDBN} via a single terminal, so no confusion is possible as
24583 to what thread and frame are the current ones.
24585 In the case of MI, the concept of selected thread and frame is less
24586 useful. First, a frontend can easily remember this information
24587 itself. Second, a graphical frontend can have more than one window,
24588 each one used for debugging a different thread, and the frontend might
24589 want to access additional threads for internal purposes. This
24590 increases the risk that by relying on implicitly selected thread, the
24591 frontend may be operating on a wrong one. Therefore, each MI command
24592 should explicitly specify which thread and frame to operate on. To
24593 make it possible, each MI command accepts the @samp{--thread} and
24594 @samp{--frame} options, the value to each is @value{GDBN} identifier
24595 for thread and frame to operate on.
24597 Usually, each top-level window in a frontend allows the user to select
24598 a thread and a frame, and remembers the user selection for further
24599 operations. However, in some cases @value{GDBN} may suggest that the
24600 current thread be changed. For example, when stopping on a breakpoint
24601 it is reasonable to switch to the thread where breakpoint is hit. For
24602 another example, if the user issues the CLI @samp{thread} command via
24603 the frontend, it is desirable to change the frontend's selected thread to the
24604 one specified by user. @value{GDBN} communicates the suggestion to
24605 change current thread using the @samp{=thread-selected} notification.
24606 No such notification is available for the selected frame at the moment.
24608 Note that historically, MI shares the selected thread with CLI, so
24609 frontends used the @code{-thread-select} to execute commands in the
24610 right context. However, getting this to work right is cumbersome. The
24611 simplest way is for frontend to emit @code{-thread-select} command
24612 before every command. This doubles the number of commands that need
24613 to be sent. The alternative approach is to suppress @code{-thread-select}
24614 if the selected thread in @value{GDBN} is supposed to be identical to the
24615 thread the frontend wants to operate on. However, getting this
24616 optimization right can be tricky. In particular, if the frontend
24617 sends several commands to @value{GDBN}, and one of the commands changes the
24618 selected thread, then the behaviour of subsequent commands will
24619 change. So, a frontend should either wait for response from such
24620 problematic commands, or explicitly add @code{-thread-select} for
24621 all subsequent commands. No frontend is known to do this exactly
24622 right, so it is suggested to just always pass the @samp{--thread} and
24623 @samp{--frame} options.
24625 @node Asynchronous and non-stop modes
24626 @subsection Asynchronous command execution and non-stop mode
24628 On some targets, @value{GDBN} is capable of processing MI commands
24629 even while the target is running. This is called @dfn{asynchronous
24630 command execution} (@pxref{Background Execution}). The frontend may
24631 specify a preferrence for asynchronous execution using the
24632 @code{-gdb-set target-async 1} command, which should be emitted before
24633 either running the executable or attaching to the target. After the
24634 frontend has started the executable or attached to the target, it can
24635 find if asynchronous execution is enabled using the
24636 @code{-list-target-features} command.
24638 Even if @value{GDBN} can accept a command while target is running,
24639 many commands that access the target do not work when the target is
24640 running. Therefore, asynchronous command execution is most useful
24641 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24642 it is possible to examine the state of one thread, while other threads
24645 When a given thread is running, MI commands that try to access the
24646 target in the context of that thread may not work, or may work only on
24647 some targets. In particular, commands that try to operate on thread's
24648 stack will not work, on any target. Commands that read memory, or
24649 modify breakpoints, may work or not work, depending on the target. Note
24650 that even commands that operate on global state, such as @code{print},
24651 @code{set}, and breakpoint commands, still access the target in the
24652 context of a specific thread, so frontend should try to find a
24653 stopped thread and perform the operation on that thread (using the
24654 @samp{--thread} option).
24656 Which commands will work in the context of a running thread is
24657 highly target dependent. However, the two commands
24658 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24659 to find the state of a thread, will always work.
24661 @node Thread groups
24662 @subsection Thread groups
24663 @value{GDBN} may be used to debug several processes at the same time.
24664 On some platfroms, @value{GDBN} may support debugging of several
24665 hardware systems, each one having several cores with several different
24666 processes running on each core. This section describes the MI
24667 mechanism to support such debugging scenarios.
24669 The key observation is that regardless of the structure of the
24670 target, MI can have a global list of threads, because most commands that
24671 accept the @samp{--thread} option do not need to know what process that
24672 thread belongs to. Therefore, it is not necessary to introduce
24673 neither additional @samp{--process} option, nor an notion of the
24674 current process in the MI interface. The only strictly new feature
24675 that is required is the ability to find how the threads are grouped
24678 To allow the user to discover such grouping, and to support arbitrary
24679 hierarchy of machines/cores/processes, MI introduces the concept of a
24680 @dfn{thread group}. Thread group is a collection of threads and other
24681 thread groups. A thread group always has a string identifier, a type,
24682 and may have additional attributes specific to the type. A new
24683 command, @code{-list-thread-groups}, returns the list of top-level
24684 thread groups, which correspond to processes that @value{GDBN} is
24685 debugging at the moment. By passing an identifier of a thread group
24686 to the @code{-list-thread-groups} command, it is possible to obtain
24687 the members of specific thread group.
24689 To allow the user to easily discover processes, and other objects, he
24690 wishes to debug, a concept of @dfn{available thread group} is
24691 introduced. Available thread group is an thread group that
24692 @value{GDBN} is not debugging, but that can be attached to, using the
24693 @code{-target-attach} command. The list of available top-level thread
24694 groups can be obtained using @samp{-list-thread-groups --available}.
24695 In general, the content of a thread group may be only retrieved only
24696 after attaching to that thread group.
24698 Thread groups are related to inferiors (@pxref{Inferiors and
24699 Programs}). Each inferior corresponds to a thread group of a special
24700 type @samp{process}, and some additional operations are permitted on
24701 such thread groups.
24703 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24704 @node GDB/MI Command Syntax
24705 @section @sc{gdb/mi} Command Syntax
24708 * GDB/MI Input Syntax::
24709 * GDB/MI Output Syntax::
24712 @node GDB/MI Input Syntax
24713 @subsection @sc{gdb/mi} Input Syntax
24715 @cindex input syntax for @sc{gdb/mi}
24716 @cindex @sc{gdb/mi}, input syntax
24718 @item @var{command} @expansion{}
24719 @code{@var{cli-command} | @var{mi-command}}
24721 @item @var{cli-command} @expansion{}
24722 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24723 @var{cli-command} is any existing @value{GDBN} CLI command.
24725 @item @var{mi-command} @expansion{}
24726 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24727 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24729 @item @var{token} @expansion{}
24730 "any sequence of digits"
24732 @item @var{option} @expansion{}
24733 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24735 @item @var{parameter} @expansion{}
24736 @code{@var{non-blank-sequence} | @var{c-string}}
24738 @item @var{operation} @expansion{}
24739 @emph{any of the operations described in this chapter}
24741 @item @var{non-blank-sequence} @expansion{}
24742 @emph{anything, provided it doesn't contain special characters such as
24743 "-", @var{nl}, """ and of course " "}
24745 @item @var{c-string} @expansion{}
24746 @code{""" @var{seven-bit-iso-c-string-content} """}
24748 @item @var{nl} @expansion{}
24757 The CLI commands are still handled by the @sc{mi} interpreter; their
24758 output is described below.
24761 The @code{@var{token}}, when present, is passed back when the command
24765 Some @sc{mi} commands accept optional arguments as part of the parameter
24766 list. Each option is identified by a leading @samp{-} (dash) and may be
24767 followed by an optional argument parameter. Options occur first in the
24768 parameter list and can be delimited from normal parameters using
24769 @samp{--} (this is useful when some parameters begin with a dash).
24776 We want easy access to the existing CLI syntax (for debugging).
24779 We want it to be easy to spot a @sc{mi} operation.
24782 @node GDB/MI Output Syntax
24783 @subsection @sc{gdb/mi} Output Syntax
24785 @cindex output syntax of @sc{gdb/mi}
24786 @cindex @sc{gdb/mi}, output syntax
24787 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24788 followed, optionally, by a single result record. This result record
24789 is for the most recent command. The sequence of output records is
24790 terminated by @samp{(gdb)}.
24792 If an input command was prefixed with a @code{@var{token}} then the
24793 corresponding output for that command will also be prefixed by that same
24797 @item @var{output} @expansion{}
24798 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24800 @item @var{result-record} @expansion{}
24801 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24803 @item @var{out-of-band-record} @expansion{}
24804 @code{@var{async-record} | @var{stream-record}}
24806 @item @var{async-record} @expansion{}
24807 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24809 @item @var{exec-async-output} @expansion{}
24810 @code{[ @var{token} ] "*" @var{async-output}}
24812 @item @var{status-async-output} @expansion{}
24813 @code{[ @var{token} ] "+" @var{async-output}}
24815 @item @var{notify-async-output} @expansion{}
24816 @code{[ @var{token} ] "=" @var{async-output}}
24818 @item @var{async-output} @expansion{}
24819 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24821 @item @var{result-class} @expansion{}
24822 @code{"done" | "running" | "connected" | "error" | "exit"}
24824 @item @var{async-class} @expansion{}
24825 @code{"stopped" | @var{others}} (where @var{others} will be added
24826 depending on the needs---this is still in development).
24828 @item @var{result} @expansion{}
24829 @code{ @var{variable} "=" @var{value}}
24831 @item @var{variable} @expansion{}
24832 @code{ @var{string} }
24834 @item @var{value} @expansion{}
24835 @code{ @var{const} | @var{tuple} | @var{list} }
24837 @item @var{const} @expansion{}
24838 @code{@var{c-string}}
24840 @item @var{tuple} @expansion{}
24841 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24843 @item @var{list} @expansion{}
24844 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24845 @var{result} ( "," @var{result} )* "]" }
24847 @item @var{stream-record} @expansion{}
24848 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24850 @item @var{console-stream-output} @expansion{}
24851 @code{"~" @var{c-string}}
24853 @item @var{target-stream-output} @expansion{}
24854 @code{"@@" @var{c-string}}
24856 @item @var{log-stream-output} @expansion{}
24857 @code{"&" @var{c-string}}
24859 @item @var{nl} @expansion{}
24862 @item @var{token} @expansion{}
24863 @emph{any sequence of digits}.
24871 All output sequences end in a single line containing a period.
24874 The @code{@var{token}} is from the corresponding request. Note that
24875 for all async output, while the token is allowed by the grammar and
24876 may be output by future versions of @value{GDBN} for select async
24877 output messages, it is generally omitted. Frontends should treat
24878 all async output as reporting general changes in the state of the
24879 target and there should be no need to associate async output to any
24883 @cindex status output in @sc{gdb/mi}
24884 @var{status-async-output} contains on-going status information about the
24885 progress of a slow operation. It can be discarded. All status output is
24886 prefixed by @samp{+}.
24889 @cindex async output in @sc{gdb/mi}
24890 @var{exec-async-output} contains asynchronous state change on the target
24891 (stopped, started, disappeared). All async output is prefixed by
24895 @cindex notify output in @sc{gdb/mi}
24896 @var{notify-async-output} contains supplementary information that the
24897 client should handle (e.g., a new breakpoint information). All notify
24898 output is prefixed by @samp{=}.
24901 @cindex console output in @sc{gdb/mi}
24902 @var{console-stream-output} is output that should be displayed as is in the
24903 console. It is the textual response to a CLI command. All the console
24904 output is prefixed by @samp{~}.
24907 @cindex target output in @sc{gdb/mi}
24908 @var{target-stream-output} is the output produced by the target program.
24909 All the target output is prefixed by @samp{@@}.
24912 @cindex log output in @sc{gdb/mi}
24913 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24914 instance messages that should be displayed as part of an error log. All
24915 the log output is prefixed by @samp{&}.
24918 @cindex list output in @sc{gdb/mi}
24919 New @sc{gdb/mi} commands should only output @var{lists} containing
24925 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24926 details about the various output records.
24928 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24929 @node GDB/MI Compatibility with CLI
24930 @section @sc{gdb/mi} Compatibility with CLI
24932 @cindex compatibility, @sc{gdb/mi} and CLI
24933 @cindex @sc{gdb/mi}, compatibility with CLI
24935 For the developers convenience CLI commands can be entered directly,
24936 but there may be some unexpected behaviour. For example, commands
24937 that query the user will behave as if the user replied yes, breakpoint
24938 command lists are not executed and some CLI commands, such as
24939 @code{if}, @code{when} and @code{define}, prompt for further input with
24940 @samp{>}, which is not valid MI output.
24942 This feature may be removed at some stage in the future and it is
24943 recommended that front ends use the @code{-interpreter-exec} command
24944 (@pxref{-interpreter-exec}).
24946 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24947 @node GDB/MI Development and Front Ends
24948 @section @sc{gdb/mi} Development and Front Ends
24949 @cindex @sc{gdb/mi} development
24951 The application which takes the MI output and presents the state of the
24952 program being debugged to the user is called a @dfn{front end}.
24954 Although @sc{gdb/mi} is still incomplete, it is currently being used
24955 by a variety of front ends to @value{GDBN}. This makes it difficult
24956 to introduce new functionality without breaking existing usage. This
24957 section tries to minimize the problems by describing how the protocol
24960 Some changes in MI need not break a carefully designed front end, and
24961 for these the MI version will remain unchanged. The following is a
24962 list of changes that may occur within one level, so front ends should
24963 parse MI output in a way that can handle them:
24967 New MI commands may be added.
24970 New fields may be added to the output of any MI command.
24973 The range of values for fields with specified values, e.g.,
24974 @code{in_scope} (@pxref{-var-update}) may be extended.
24976 @c The format of field's content e.g type prefix, may change so parse it
24977 @c at your own risk. Yes, in general?
24979 @c The order of fields may change? Shouldn't really matter but it might
24980 @c resolve inconsistencies.
24983 If the changes are likely to break front ends, the MI version level
24984 will be increased by one. This will allow the front end to parse the
24985 output according to the MI version. Apart from mi0, new versions of
24986 @value{GDBN} will not support old versions of MI and it will be the
24987 responsibility of the front end to work with the new one.
24989 @c Starting with mi3, add a new command -mi-version that prints the MI
24992 The best way to avoid unexpected changes in MI that might break your front
24993 end is to make your project known to @value{GDBN} developers and
24994 follow development on @email{gdb@@sourceware.org} and
24995 @email{gdb-patches@@sourceware.org}.
24996 @cindex mailing lists
24998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24999 @node GDB/MI Output Records
25000 @section @sc{gdb/mi} Output Records
25003 * GDB/MI Result Records::
25004 * GDB/MI Stream Records::
25005 * GDB/MI Async Records::
25006 * GDB/MI Frame Information::
25007 * GDB/MI Thread Information::
25008 * GDB/MI Ada Exception Information::
25011 @node GDB/MI Result Records
25012 @subsection @sc{gdb/mi} Result Records
25014 @cindex result records in @sc{gdb/mi}
25015 @cindex @sc{gdb/mi}, result records
25016 In addition to a number of out-of-band notifications, the response to a
25017 @sc{gdb/mi} command includes one of the following result indications:
25021 @item "^done" [ "," @var{results} ]
25022 The synchronous operation was successful, @code{@var{results}} are the return
25027 This result record is equivalent to @samp{^done}. Historically, it
25028 was output instead of @samp{^done} if the command has resumed the
25029 target. This behaviour is maintained for backward compatibility, but
25030 all frontends should treat @samp{^done} and @samp{^running}
25031 identically and rely on the @samp{*running} output record to determine
25032 which threads are resumed.
25036 @value{GDBN} has connected to a remote target.
25038 @item "^error" "," @var{c-string}
25040 The operation failed. The @code{@var{c-string}} contains the corresponding
25045 @value{GDBN} has terminated.
25049 @node GDB/MI Stream Records
25050 @subsection @sc{gdb/mi} Stream Records
25052 @cindex @sc{gdb/mi}, stream records
25053 @cindex stream records in @sc{gdb/mi}
25054 @value{GDBN} internally maintains a number of output streams: the console, the
25055 target, and the log. The output intended for each of these streams is
25056 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25058 Each stream record begins with a unique @dfn{prefix character} which
25059 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25060 Syntax}). In addition to the prefix, each stream record contains a
25061 @code{@var{string-output}}. This is either raw text (with an implicit new
25062 line) or a quoted C string (which does not contain an implicit newline).
25065 @item "~" @var{string-output}
25066 The console output stream contains text that should be displayed in the
25067 CLI console window. It contains the textual responses to CLI commands.
25069 @item "@@" @var{string-output}
25070 The target output stream contains any textual output from the running
25071 target. This is only present when GDB's event loop is truly
25072 asynchronous, which is currently only the case for remote targets.
25074 @item "&" @var{string-output}
25075 The log stream contains debugging messages being produced by @value{GDBN}'s
25079 @node GDB/MI Async Records
25080 @subsection @sc{gdb/mi} Async Records
25082 @cindex async records in @sc{gdb/mi}
25083 @cindex @sc{gdb/mi}, async records
25084 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25085 additional changes that have occurred. Those changes can either be a
25086 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25087 target activity (e.g., target stopped).
25089 The following is the list of possible async records:
25093 @item *running,thread-id="@var{thread}"
25094 The target is now running. The @var{thread} field tells which
25095 specific thread is now running, and can be @samp{all} if all threads
25096 are running. The frontend should assume that no interaction with a
25097 running thread is possible after this notification is produced.
25098 The frontend should not assume that this notification is output
25099 only once for any command. @value{GDBN} may emit this notification
25100 several times, either for different threads, because it cannot resume
25101 all threads together, or even for a single thread, if the thread must
25102 be stepped though some code before letting it run freely.
25104 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25105 The target has stopped. The @var{reason} field can have one of the
25109 @item breakpoint-hit
25110 A breakpoint was reached.
25111 @item watchpoint-trigger
25112 A watchpoint was triggered.
25113 @item read-watchpoint-trigger
25114 A read watchpoint was triggered.
25115 @item access-watchpoint-trigger
25116 An access watchpoint was triggered.
25117 @item function-finished
25118 An -exec-finish or similar CLI command was accomplished.
25119 @item location-reached
25120 An -exec-until or similar CLI command was accomplished.
25121 @item watchpoint-scope
25122 A watchpoint has gone out of scope.
25123 @item end-stepping-range
25124 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25125 similar CLI command was accomplished.
25126 @item exited-signalled
25127 The inferior exited because of a signal.
25129 The inferior exited.
25130 @item exited-normally
25131 The inferior exited normally.
25132 @item signal-received
25133 A signal was received by the inferior.
25136 The @var{id} field identifies the thread that directly caused the stop
25137 -- for example by hitting a breakpoint. Depending on whether all-stop
25138 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25139 stop all threads, or only the thread that directly triggered the stop.
25140 If all threads are stopped, the @var{stopped} field will have the
25141 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25142 field will be a list of thread identifiers. Presently, this list will
25143 always include a single thread, but frontend should be prepared to see
25144 several threads in the list. The @var{core} field reports the
25145 processor core on which the stop event has happened. This field may be absent
25146 if such information is not available.
25148 @item =thread-group-added,id="@var{id}"
25149 @itemx =thread-group-removed,id="@var{id}"
25150 A thread group was either added or removed. The @var{id} field
25151 contains the @value{GDBN} identifier of the thread group. When a thread
25152 group is added, it generally might not be associated with a running
25153 process. When a thread group is removed, its id becomes invalid and
25154 cannot be used in any way.
25156 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25157 A thread group became associated with a running program,
25158 either because the program was just started or the thread group
25159 was attached to a program. The @var{id} field contains the
25160 @value{GDBN} identifier of the thread group. The @var{pid} field
25161 contains process identifier, specific to the operating system.
25163 @itemx =thread-group-exited,id="@var{id}"
25164 A thread group is no longer associated with a running program,
25165 either because the program has exited, or because it was detached
25166 from. The @var{id} field contains the @value{GDBN} identifier of the
25169 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25170 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25171 A thread either was created, or has exited. The @var{id} field
25172 contains the @value{GDBN} identifier of the thread. The @var{gid}
25173 field identifies the thread group this thread belongs to.
25175 @item =thread-selected,id="@var{id}"
25176 Informs that the selected thread was changed as result of the last
25177 command. This notification is not emitted as result of @code{-thread-select}
25178 command but is emitted whenever an MI command that is not documented
25179 to change the selected thread actually changes it. In particular,
25180 invoking, directly or indirectly (via user-defined command), the CLI
25181 @code{thread} command, will generate this notification.
25183 We suggest that in response to this notification, front ends
25184 highlight the selected thread and cause subsequent commands to apply to
25187 @item =library-loaded,...
25188 Reports that a new library file was loaded by the program. This
25189 notification has 4 fields---@var{id}, @var{target-name},
25190 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25191 opaque identifier of the library. For remote debugging case,
25192 @var{target-name} and @var{host-name} fields give the name of the
25193 library file on the target, and on the host respectively. For native
25194 debugging, both those fields have the same value. The
25195 @var{symbols-loaded} field is emitted only for backward compatibility
25196 and should not be relied on to convey any useful information. The
25197 @var{thread-group} field, if present, specifies the id of the thread
25198 group in whose context the library was loaded. If the field is
25199 absent, it means the library was loaded in the context of all present
25202 @item =library-unloaded,...
25203 Reports that a library was unloaded by the program. This notification
25204 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25205 the same meaning as for the @code{=library-loaded} notification.
25206 The @var{thread-group} field, if present, specifies the id of the
25207 thread group in whose context the library was unloaded. If the field is
25208 absent, it means the library was unloaded in the context of all present
25211 @item =breakpoint-created,bkpt=@{...@}
25212 @itemx =breakpoint-modified,bkpt=@{...@}
25213 @itemx =breakpoint-deleted,bkpt=@{...@}
25214 Reports that a breakpoint was created, modified, or deleted,
25215 respectively. Only user-visible breakpoints are reported to the MI
25218 The @var{bkpt} argument is of the same form as returned by the various
25219 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
25221 Note that if a breakpoint is emitted in the result record of a
25222 command, then it will not also be emitted in an async record.
25226 @node GDB/MI Frame Information
25227 @subsection @sc{gdb/mi} Frame Information
25229 Response from many MI commands includes an information about stack
25230 frame. This information is a tuple that may have the following
25235 The level of the stack frame. The innermost frame has the level of
25236 zero. This field is always present.
25239 The name of the function corresponding to the frame. This field may
25240 be absent if @value{GDBN} is unable to determine the function name.
25243 The code address for the frame. This field is always present.
25246 The name of the source files that correspond to the frame's code
25247 address. This field may be absent.
25250 The source line corresponding to the frames' code address. This field
25254 The name of the binary file (either executable or shared library) the
25255 corresponds to the frame's code address. This field may be absent.
25259 @node GDB/MI Thread Information
25260 @subsection @sc{gdb/mi} Thread Information
25262 Whenever @value{GDBN} has to report an information about a thread, it
25263 uses a tuple with the following fields:
25267 The numeric id assigned to the thread by @value{GDBN}. This field is
25271 Target-specific string identifying the thread. This field is always present.
25274 Additional information about the thread provided by the target.
25275 It is supposed to be human-readable and not interpreted by the
25276 frontend. This field is optional.
25279 Either @samp{stopped} or @samp{running}, depending on whether the
25280 thread is presently running. This field is always present.
25283 The value of this field is an integer number of the processor core the
25284 thread was last seen on. This field is optional.
25287 @node GDB/MI Ada Exception Information
25288 @subsection @sc{gdb/mi} Ada Exception Information
25290 Whenever a @code{*stopped} record is emitted because the program
25291 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25292 @value{GDBN} provides the name of the exception that was raised via
25293 the @code{exception-name} field.
25295 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25296 @node GDB/MI Simple Examples
25297 @section Simple Examples of @sc{gdb/mi} Interaction
25298 @cindex @sc{gdb/mi}, simple examples
25300 This subsection presents several simple examples of interaction using
25301 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25302 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25303 the output received from @sc{gdb/mi}.
25305 Note the line breaks shown in the examples are here only for
25306 readability, they don't appear in the real output.
25308 @subheading Setting a Breakpoint
25310 Setting a breakpoint generates synchronous output which contains detailed
25311 information of the breakpoint.
25314 -> -break-insert main
25315 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25316 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25317 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25321 @subheading Program Execution
25323 Program execution generates asynchronous records and MI gives the
25324 reason that execution stopped.
25330 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25331 frame=@{addr="0x08048564",func="main",
25332 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25333 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25338 <- *stopped,reason="exited-normally"
25342 @subheading Quitting @value{GDBN}
25344 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25352 Please note that @samp{^exit} is printed immediately, but it might
25353 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25354 performs necessary cleanups, including killing programs being debugged
25355 or disconnecting from debug hardware, so the frontend should wait till
25356 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25357 fails to exit in reasonable time.
25359 @subheading A Bad Command
25361 Here's what happens if you pass a non-existent command:
25365 <- ^error,msg="Undefined MI command: rubbish"
25370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25371 @node GDB/MI Command Description Format
25372 @section @sc{gdb/mi} Command Description Format
25374 The remaining sections describe blocks of commands. Each block of
25375 commands is laid out in a fashion similar to this section.
25377 @subheading Motivation
25379 The motivation for this collection of commands.
25381 @subheading Introduction
25383 A brief introduction to this collection of commands as a whole.
25385 @subheading Commands
25387 For each command in the block, the following is described:
25389 @subsubheading Synopsis
25392 -command @var{args}@dots{}
25395 @subsubheading Result
25397 @subsubheading @value{GDBN} Command
25399 The corresponding @value{GDBN} CLI command(s), if any.
25401 @subsubheading Example
25403 Example(s) formatted for readability. Some of the described commands have
25404 not been implemented yet and these are labeled N.A.@: (not available).
25407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25408 @node GDB/MI Breakpoint Commands
25409 @section @sc{gdb/mi} Breakpoint Commands
25411 @cindex breakpoint commands for @sc{gdb/mi}
25412 @cindex @sc{gdb/mi}, breakpoint commands
25413 This section documents @sc{gdb/mi} commands for manipulating
25416 @subheading The @code{-break-after} Command
25417 @findex -break-after
25419 @subsubheading Synopsis
25422 -break-after @var{number} @var{count}
25425 The breakpoint number @var{number} is not in effect until it has been
25426 hit @var{count} times. To see how this is reflected in the output of
25427 the @samp{-break-list} command, see the description of the
25428 @samp{-break-list} command below.
25430 @subsubheading @value{GDBN} Command
25432 The corresponding @value{GDBN} command is @samp{ignore}.
25434 @subsubheading Example
25439 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25440 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25441 fullname="/home/foo/hello.c",line="5",times="0"@}
25448 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25449 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25450 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25451 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25452 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25453 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25454 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25455 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25456 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25457 line="5",times="0",ignore="3"@}]@}
25462 @subheading The @code{-break-catch} Command
25463 @findex -break-catch
25466 @subheading The @code{-break-commands} Command
25467 @findex -break-commands
25469 @subsubheading Synopsis
25472 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25475 Specifies the CLI commands that should be executed when breakpoint
25476 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25477 are the commands. If no command is specified, any previously-set
25478 commands are cleared. @xref{Break Commands}. Typical use of this
25479 functionality is tracing a program, that is, printing of values of
25480 some variables whenever breakpoint is hit and then continuing.
25482 @subsubheading @value{GDBN} Command
25484 The corresponding @value{GDBN} command is @samp{commands}.
25486 @subsubheading Example
25491 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25492 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25493 fullname="/home/foo/hello.c",line="5",times="0"@}
25495 -break-commands 1 "print v" "continue"
25500 @subheading The @code{-break-condition} Command
25501 @findex -break-condition
25503 @subsubheading Synopsis
25506 -break-condition @var{number} @var{expr}
25509 Breakpoint @var{number} will stop the program only if the condition in
25510 @var{expr} is true. The condition becomes part of the
25511 @samp{-break-list} output (see the description of the @samp{-break-list}
25514 @subsubheading @value{GDBN} Command
25516 The corresponding @value{GDBN} command is @samp{condition}.
25518 @subsubheading Example
25522 -break-condition 1 1
25526 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25527 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25528 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25529 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25530 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25531 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25532 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25533 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25534 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25535 line="5",cond="1",times="0",ignore="3"@}]@}
25539 @subheading The @code{-break-delete} Command
25540 @findex -break-delete
25542 @subsubheading Synopsis
25545 -break-delete ( @var{breakpoint} )+
25548 Delete the breakpoint(s) whose number(s) are specified in the argument
25549 list. This is obviously reflected in the breakpoint list.
25551 @subsubheading @value{GDBN} Command
25553 The corresponding @value{GDBN} command is @samp{delete}.
25555 @subsubheading Example
25563 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25564 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25565 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25566 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25567 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25568 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25569 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25574 @subheading The @code{-break-disable} Command
25575 @findex -break-disable
25577 @subsubheading Synopsis
25580 -break-disable ( @var{breakpoint} )+
25583 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25584 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25586 @subsubheading @value{GDBN} Command
25588 The corresponding @value{GDBN} command is @samp{disable}.
25590 @subsubheading Example
25598 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25599 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25600 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25601 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25602 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25603 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25604 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25605 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25606 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25607 line="5",times="0"@}]@}
25611 @subheading The @code{-break-enable} Command
25612 @findex -break-enable
25614 @subsubheading Synopsis
25617 -break-enable ( @var{breakpoint} )+
25620 Enable (previously disabled) @var{breakpoint}(s).
25622 @subsubheading @value{GDBN} Command
25624 The corresponding @value{GDBN} command is @samp{enable}.
25626 @subsubheading Example
25634 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25635 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25636 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25637 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25638 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25639 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25640 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25641 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25642 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25643 line="5",times="0"@}]@}
25647 @subheading The @code{-break-info} Command
25648 @findex -break-info
25650 @subsubheading Synopsis
25653 -break-info @var{breakpoint}
25657 Get information about a single breakpoint.
25659 @subsubheading @value{GDBN} Command
25661 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25663 @subsubheading Example
25666 @subheading The @code{-break-insert} Command
25667 @findex -break-insert
25669 @subsubheading Synopsis
25672 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25673 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25674 [ -p @var{thread} ] [ @var{location} ]
25678 If specified, @var{location}, can be one of:
25685 @item filename:linenum
25686 @item filename:function
25690 The possible optional parameters of this command are:
25694 Insert a temporary breakpoint.
25696 Insert a hardware breakpoint.
25697 @item -c @var{condition}
25698 Make the breakpoint conditional on @var{condition}.
25699 @item -i @var{ignore-count}
25700 Initialize the @var{ignore-count}.
25702 If @var{location} cannot be parsed (for example if it
25703 refers to unknown files or functions), create a pending
25704 breakpoint. Without this flag, @value{GDBN} will report
25705 an error, and won't create a breakpoint, if @var{location}
25708 Create a disabled breakpoint.
25710 Create a tracepoint. @xref{Tracepoints}. When this parameter
25711 is used together with @samp{-h}, a fast tracepoint is created.
25714 @subsubheading Result
25716 The result is in the form:
25719 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25720 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25721 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25722 times="@var{times}"@}
25726 where @var{number} is the @value{GDBN} number for this breakpoint,
25727 @var{funcname} is the name of the function where the breakpoint was
25728 inserted, @var{filename} is the name of the source file which contains
25729 this function, @var{lineno} is the source line number within that file
25730 and @var{times} the number of times that the breakpoint has been hit
25731 (always 0 for -break-insert but may be greater for -break-info or -break-list
25732 which use the same output).
25734 Note: this format is open to change.
25735 @c An out-of-band breakpoint instead of part of the result?
25737 @subsubheading @value{GDBN} Command
25739 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25740 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25742 @subsubheading Example
25747 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25748 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25750 -break-insert -t foo
25751 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25752 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25755 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25756 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25757 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25758 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25759 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25760 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25761 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25762 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25763 addr="0x0001072c", func="main",file="recursive2.c",
25764 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25765 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25766 addr="0x00010774",func="foo",file="recursive2.c",
25767 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25769 -break-insert -r foo.*
25770 ~int foo(int, int);
25771 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25772 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25776 @subheading The @code{-break-list} Command
25777 @findex -break-list
25779 @subsubheading Synopsis
25785 Displays the list of inserted breakpoints, showing the following fields:
25789 number of the breakpoint
25791 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25793 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25796 is the breakpoint enabled or no: @samp{y} or @samp{n}
25798 memory location at which the breakpoint is set
25800 logical location of the breakpoint, expressed by function name, file
25803 number of times the breakpoint has been hit
25806 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25807 @code{body} field is an empty list.
25809 @subsubheading @value{GDBN} Command
25811 The corresponding @value{GDBN} command is @samp{info break}.
25813 @subsubheading Example
25818 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25819 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25820 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25821 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25822 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25823 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25824 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25825 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25826 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25827 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25828 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25829 line="13",times="0"@}]@}
25833 Here's an example of the result when there are no breakpoints:
25838 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25839 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25840 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25841 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25842 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25843 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25844 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25849 @subheading The @code{-break-passcount} Command
25850 @findex -break-passcount
25852 @subsubheading Synopsis
25855 -break-passcount @var{tracepoint-number} @var{passcount}
25858 Set the passcount for tracepoint @var{tracepoint-number} to
25859 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25860 is not a tracepoint, error is emitted. This corresponds to CLI
25861 command @samp{passcount}.
25863 @subheading The @code{-break-watch} Command
25864 @findex -break-watch
25866 @subsubheading Synopsis
25869 -break-watch [ -a | -r ]
25872 Create a watchpoint. With the @samp{-a} option it will create an
25873 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25874 read from or on a write to the memory location. With the @samp{-r}
25875 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25876 trigger only when the memory location is accessed for reading. Without
25877 either of the options, the watchpoint created is a regular watchpoint,
25878 i.e., it will trigger when the memory location is accessed for writing.
25879 @xref{Set Watchpoints, , Setting Watchpoints}.
25881 Note that @samp{-break-list} will report a single list of watchpoints and
25882 breakpoints inserted.
25884 @subsubheading @value{GDBN} Command
25886 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25889 @subsubheading Example
25891 Setting a watchpoint on a variable in the @code{main} function:
25896 ^done,wpt=@{number="2",exp="x"@}
25901 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25902 value=@{old="-268439212",new="55"@},
25903 frame=@{func="main",args=[],file="recursive2.c",
25904 fullname="/home/foo/bar/recursive2.c",line="5"@}
25908 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25909 the program execution twice: first for the variable changing value, then
25910 for the watchpoint going out of scope.
25915 ^done,wpt=@{number="5",exp="C"@}
25920 *stopped,reason="watchpoint-trigger",
25921 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25922 frame=@{func="callee4",args=[],
25923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25924 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25929 *stopped,reason="watchpoint-scope",wpnum="5",
25930 frame=@{func="callee3",args=[@{name="strarg",
25931 value="0x11940 \"A string argument.\""@}],
25932 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25933 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25937 Listing breakpoints and watchpoints, at different points in the program
25938 execution. Note that once the watchpoint goes out of scope, it is
25944 ^done,wpt=@{number="2",exp="C"@}
25947 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25948 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25949 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25950 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25951 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25952 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25953 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25954 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25955 addr="0x00010734",func="callee4",
25956 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25957 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25958 bkpt=@{number="2",type="watchpoint",disp="keep",
25959 enabled="y",addr="",what="C",times="0"@}]@}
25964 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25965 value=@{old="-276895068",new="3"@},
25966 frame=@{func="callee4",args=[],
25967 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25968 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25971 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25972 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25973 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25974 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25975 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25976 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25977 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25978 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25979 addr="0x00010734",func="callee4",
25980 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25981 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25982 bkpt=@{number="2",type="watchpoint",disp="keep",
25983 enabled="y",addr="",what="C",times="-5"@}]@}
25987 ^done,reason="watchpoint-scope",wpnum="2",
25988 frame=@{func="callee3",args=[@{name="strarg",
25989 value="0x11940 \"A string argument.\""@}],
25990 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25991 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25994 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25995 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25996 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25997 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25998 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25999 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26000 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26001 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26002 addr="0x00010734",func="callee4",
26003 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26004 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26009 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26010 @node GDB/MI Program Context
26011 @section @sc{gdb/mi} Program Context
26013 @subheading The @code{-exec-arguments} Command
26014 @findex -exec-arguments
26017 @subsubheading Synopsis
26020 -exec-arguments @var{args}
26023 Set the inferior program arguments, to be used in the next
26026 @subsubheading @value{GDBN} Command
26028 The corresponding @value{GDBN} command is @samp{set args}.
26030 @subsubheading Example
26034 -exec-arguments -v word
26041 @subheading The @code{-exec-show-arguments} Command
26042 @findex -exec-show-arguments
26044 @subsubheading Synopsis
26047 -exec-show-arguments
26050 Print the arguments of the program.
26052 @subsubheading @value{GDBN} Command
26054 The corresponding @value{GDBN} command is @samp{show args}.
26056 @subsubheading Example
26061 @subheading The @code{-environment-cd} Command
26062 @findex -environment-cd
26064 @subsubheading Synopsis
26067 -environment-cd @var{pathdir}
26070 Set @value{GDBN}'s working directory.
26072 @subsubheading @value{GDBN} Command
26074 The corresponding @value{GDBN} command is @samp{cd}.
26076 @subsubheading Example
26080 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26086 @subheading The @code{-environment-directory} Command
26087 @findex -environment-directory
26089 @subsubheading Synopsis
26092 -environment-directory [ -r ] [ @var{pathdir} ]+
26095 Add directories @var{pathdir} to beginning of search path for source files.
26096 If the @samp{-r} option is used, the search path is reset to the default
26097 search path. If directories @var{pathdir} are supplied in addition to the
26098 @samp{-r} option, the search path is first reset and then addition
26100 Multiple directories may be specified, separated by blanks. Specifying
26101 multiple directories in a single command
26102 results in the directories added to the beginning of the
26103 search path in the same order they were presented in the command.
26104 If blanks are needed as
26105 part of a directory name, double-quotes should be used around
26106 the name. In the command output, the path will show up separated
26107 by the system directory-separator character. The directory-separator
26108 character must not be used
26109 in any directory name.
26110 If no directories are specified, the current search path is displayed.
26112 @subsubheading @value{GDBN} Command
26114 The corresponding @value{GDBN} command is @samp{dir}.
26116 @subsubheading Example
26120 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26121 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26123 -environment-directory ""
26124 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26126 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26127 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26129 -environment-directory -r
26130 ^done,source-path="$cdir:$cwd"
26135 @subheading The @code{-environment-path} Command
26136 @findex -environment-path
26138 @subsubheading Synopsis
26141 -environment-path [ -r ] [ @var{pathdir} ]+
26144 Add directories @var{pathdir} to beginning of search path for object files.
26145 If the @samp{-r} option is used, the search path is reset to the original
26146 search path that existed at gdb start-up. If directories @var{pathdir} are
26147 supplied in addition to the
26148 @samp{-r} option, the search path is first reset and then addition
26150 Multiple directories may be specified, separated by blanks. Specifying
26151 multiple directories in a single command
26152 results in the directories added to the beginning of the
26153 search path in the same order they were presented in the command.
26154 If blanks are needed as
26155 part of a directory name, double-quotes should be used around
26156 the name. In the command output, the path will show up separated
26157 by the system directory-separator character. The directory-separator
26158 character must not be used
26159 in any directory name.
26160 If no directories are specified, the current path is displayed.
26163 @subsubheading @value{GDBN} Command
26165 The corresponding @value{GDBN} command is @samp{path}.
26167 @subsubheading Example
26172 ^done,path="/usr/bin"
26174 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26175 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26177 -environment-path -r /usr/local/bin
26178 ^done,path="/usr/local/bin:/usr/bin"
26183 @subheading The @code{-environment-pwd} Command
26184 @findex -environment-pwd
26186 @subsubheading Synopsis
26192 Show the current working directory.
26194 @subsubheading @value{GDBN} Command
26196 The corresponding @value{GDBN} command is @samp{pwd}.
26198 @subsubheading Example
26203 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26208 @node GDB/MI Thread Commands
26209 @section @sc{gdb/mi} Thread Commands
26212 @subheading The @code{-thread-info} Command
26213 @findex -thread-info
26215 @subsubheading Synopsis
26218 -thread-info [ @var{thread-id} ]
26221 Reports information about either a specific thread, if
26222 the @var{thread-id} parameter is present, or about all
26223 threads. When printing information about all threads,
26224 also reports the current thread.
26226 @subsubheading @value{GDBN} Command
26228 The @samp{info thread} command prints the same information
26231 @subsubheading Result
26233 The result is a list of threads. The following attributes are
26234 defined for a given thread:
26238 This field exists only for the current thread. It has the value @samp{*}.
26241 The identifier that @value{GDBN} uses to refer to the thread.
26244 The identifier that the target uses to refer to the thread.
26247 Extra information about the thread, in a target-specific format. This
26251 The name of the thread. If the user specified a name using the
26252 @code{thread name} command, then this name is given. Otherwise, if
26253 @value{GDBN} can extract the thread name from the target, then that
26254 name is given. If @value{GDBN} cannot find the thread name, then this
26258 The stack frame currently executing in the thread.
26261 The thread's state. The @samp{state} field may have the following
26266 The thread is stopped. Frame information is available for stopped
26270 The thread is running. There's no frame information for running
26276 If @value{GDBN} can find the CPU core on which this thread is running,
26277 then this field is the core identifier. This field is optional.
26281 @subsubheading Example
26286 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26287 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26288 args=[]@},state="running"@},
26289 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26290 frame=@{level="0",addr="0x0804891f",func="foo",
26291 args=[@{name="i",value="10"@}],
26292 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26293 state="running"@}],
26294 current-thread-id="1"
26298 @subheading The @code{-thread-list-ids} Command
26299 @findex -thread-list-ids
26301 @subsubheading Synopsis
26307 Produces a list of the currently known @value{GDBN} thread ids. At the
26308 end of the list it also prints the total number of such threads.
26310 This command is retained for historical reasons, the
26311 @code{-thread-info} command should be used instead.
26313 @subsubheading @value{GDBN} Command
26315 Part of @samp{info threads} supplies the same information.
26317 @subsubheading Example
26322 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26323 current-thread-id="1",number-of-threads="3"
26328 @subheading The @code{-thread-select} Command
26329 @findex -thread-select
26331 @subsubheading Synopsis
26334 -thread-select @var{threadnum}
26337 Make @var{threadnum} the current thread. It prints the number of the new
26338 current thread, and the topmost frame for that thread.
26340 This command is deprecated in favor of explicitly using the
26341 @samp{--thread} option to each command.
26343 @subsubheading @value{GDBN} Command
26345 The corresponding @value{GDBN} command is @samp{thread}.
26347 @subsubheading Example
26354 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26355 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26359 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26360 number-of-threads="3"
26363 ^done,new-thread-id="3",
26364 frame=@{level="0",func="vprintf",
26365 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26366 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26371 @node GDB/MI Program Execution
26372 @section @sc{gdb/mi} Program Execution
26374 These are the asynchronous commands which generate the out-of-band
26375 record @samp{*stopped}. Currently @value{GDBN} only really executes
26376 asynchronously with remote targets and this interaction is mimicked in
26379 @subheading The @code{-exec-continue} Command
26380 @findex -exec-continue
26382 @subsubheading Synopsis
26385 -exec-continue [--reverse] [--all|--thread-group N]
26388 Resumes the execution of the inferior program, which will continue
26389 to execute until it reaches a debugger stop event. If the
26390 @samp{--reverse} option is specified, execution resumes in reverse until
26391 it reaches a stop event. Stop events may include
26394 breakpoints or watchpoints
26396 signals or exceptions
26398 the end of the process (or its beginning under @samp{--reverse})
26400 the end or beginning of a replay log if one is being used.
26402 In all-stop mode (@pxref{All-Stop
26403 Mode}), may resume only one thread, or all threads, depending on the
26404 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26405 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26406 ignored in all-stop mode. If the @samp{--thread-group} options is
26407 specified, then all threads in that thread group are resumed.
26409 @subsubheading @value{GDBN} Command
26411 The corresponding @value{GDBN} corresponding is @samp{continue}.
26413 @subsubheading Example
26420 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26421 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26427 @subheading The @code{-exec-finish} Command
26428 @findex -exec-finish
26430 @subsubheading Synopsis
26433 -exec-finish [--reverse]
26436 Resumes the execution of the inferior program until the current
26437 function is exited. Displays the results returned by the function.
26438 If the @samp{--reverse} option is specified, resumes the reverse
26439 execution of the inferior program until the point where current
26440 function was called.
26442 @subsubheading @value{GDBN} Command
26444 The corresponding @value{GDBN} command is @samp{finish}.
26446 @subsubheading Example
26448 Function returning @code{void}.
26455 *stopped,reason="function-finished",frame=@{func="main",args=[],
26456 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26460 Function returning other than @code{void}. The name of the internal
26461 @value{GDBN} variable storing the result is printed, together with the
26468 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26469 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26471 gdb-result-var="$1",return-value="0"
26476 @subheading The @code{-exec-interrupt} Command
26477 @findex -exec-interrupt
26479 @subsubheading Synopsis
26482 -exec-interrupt [--all|--thread-group N]
26485 Interrupts the background execution of the target. Note how the token
26486 associated with the stop message is the one for the execution command
26487 that has been interrupted. The token for the interrupt itself only
26488 appears in the @samp{^done} output. If the user is trying to
26489 interrupt a non-running program, an error message will be printed.
26491 Note that when asynchronous execution is enabled, this command is
26492 asynchronous just like other execution commands. That is, first the
26493 @samp{^done} response will be printed, and the target stop will be
26494 reported after that using the @samp{*stopped} notification.
26496 In non-stop mode, only the context thread is interrupted by default.
26497 All threads (in all inferiors) will be interrupted if the
26498 @samp{--all} option is specified. If the @samp{--thread-group}
26499 option is specified, all threads in that group will be interrupted.
26501 @subsubheading @value{GDBN} Command
26503 The corresponding @value{GDBN} command is @samp{interrupt}.
26505 @subsubheading Example
26516 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26517 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26518 fullname="/home/foo/bar/try.c",line="13"@}
26523 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26527 @subheading The @code{-exec-jump} Command
26530 @subsubheading Synopsis
26533 -exec-jump @var{location}
26536 Resumes execution of the inferior program at the location specified by
26537 parameter. @xref{Specify Location}, for a description of the
26538 different forms of @var{location}.
26540 @subsubheading @value{GDBN} Command
26542 The corresponding @value{GDBN} command is @samp{jump}.
26544 @subsubheading Example
26547 -exec-jump foo.c:10
26548 *running,thread-id="all"
26553 @subheading The @code{-exec-next} Command
26556 @subsubheading Synopsis
26559 -exec-next [--reverse]
26562 Resumes execution of the inferior program, stopping when the beginning
26563 of the next source line is reached.
26565 If the @samp{--reverse} option is specified, resumes reverse execution
26566 of the inferior program, stopping at the beginning of the previous
26567 source line. If you issue this command on the first line of a
26568 function, it will take you back to the caller of that function, to the
26569 source line where the function was called.
26572 @subsubheading @value{GDBN} Command
26574 The corresponding @value{GDBN} command is @samp{next}.
26576 @subsubheading Example
26582 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26587 @subheading The @code{-exec-next-instruction} Command
26588 @findex -exec-next-instruction
26590 @subsubheading Synopsis
26593 -exec-next-instruction [--reverse]
26596 Executes one machine instruction. If the instruction is a function
26597 call, continues until the function returns. If the program stops at an
26598 instruction in the middle of a source line, the address will be
26601 If the @samp{--reverse} option is specified, resumes reverse execution
26602 of the inferior program, stopping at the previous instruction. If the
26603 previously executed instruction was a return from another function,
26604 it will continue to execute in reverse until the call to that function
26605 (from the current stack frame) is reached.
26607 @subsubheading @value{GDBN} Command
26609 The corresponding @value{GDBN} command is @samp{nexti}.
26611 @subsubheading Example
26615 -exec-next-instruction
26619 *stopped,reason="end-stepping-range",
26620 addr="0x000100d4",line="5",file="hello.c"
26625 @subheading The @code{-exec-return} Command
26626 @findex -exec-return
26628 @subsubheading Synopsis
26634 Makes current function return immediately. Doesn't execute the inferior.
26635 Displays the new current frame.
26637 @subsubheading @value{GDBN} Command
26639 The corresponding @value{GDBN} command is @samp{return}.
26641 @subsubheading Example
26645 200-break-insert callee4
26646 200^done,bkpt=@{number="1",addr="0x00010734",
26647 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26652 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26653 frame=@{func="callee4",args=[],
26654 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26655 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26661 111^done,frame=@{level="0",func="callee3",
26662 args=[@{name="strarg",
26663 value="0x11940 \"A string argument.\""@}],
26664 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26665 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26670 @subheading The @code{-exec-run} Command
26673 @subsubheading Synopsis
26676 -exec-run [--all | --thread-group N]
26679 Starts execution of the inferior from the beginning. The inferior
26680 executes until either a breakpoint is encountered or the program
26681 exits. In the latter case the output will include an exit code, if
26682 the program has exited exceptionally.
26684 When no option is specified, the current inferior is started. If the
26685 @samp{--thread-group} option is specified, it should refer to a thread
26686 group of type @samp{process}, and that thread group will be started.
26687 If the @samp{--all} option is specified, then all inferiors will be started.
26689 @subsubheading @value{GDBN} Command
26691 The corresponding @value{GDBN} command is @samp{run}.
26693 @subsubheading Examples
26698 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26703 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26704 frame=@{func="main",args=[],file="recursive2.c",
26705 fullname="/home/foo/bar/recursive2.c",line="4"@}
26710 Program exited normally:
26718 *stopped,reason="exited-normally"
26723 Program exited exceptionally:
26731 *stopped,reason="exited",exit-code="01"
26735 Another way the program can terminate is if it receives a signal such as
26736 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26740 *stopped,reason="exited-signalled",signal-name="SIGINT",
26741 signal-meaning="Interrupt"
26745 @c @subheading -exec-signal
26748 @subheading The @code{-exec-step} Command
26751 @subsubheading Synopsis
26754 -exec-step [--reverse]
26757 Resumes execution of the inferior program, stopping when the beginning
26758 of the next source line is reached, if the next source line is not a
26759 function call. If it is, stop at the first instruction of the called
26760 function. If the @samp{--reverse} option is specified, resumes reverse
26761 execution of the inferior program, stopping at the beginning of the
26762 previously executed source line.
26764 @subsubheading @value{GDBN} Command
26766 The corresponding @value{GDBN} command is @samp{step}.
26768 @subsubheading Example
26770 Stepping into a function:
26776 *stopped,reason="end-stepping-range",
26777 frame=@{func="foo",args=[@{name="a",value="10"@},
26778 @{name="b",value="0"@}],file="recursive2.c",
26779 fullname="/home/foo/bar/recursive2.c",line="11"@}
26789 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26794 @subheading The @code{-exec-step-instruction} Command
26795 @findex -exec-step-instruction
26797 @subsubheading Synopsis
26800 -exec-step-instruction [--reverse]
26803 Resumes the inferior which executes one machine instruction. If the
26804 @samp{--reverse} option is specified, resumes reverse execution of the
26805 inferior program, stopping at the previously executed instruction.
26806 The output, once @value{GDBN} has stopped, will vary depending on
26807 whether we have stopped in the middle of a source line or not. In the
26808 former case, the address at which the program stopped will be printed
26811 @subsubheading @value{GDBN} Command
26813 The corresponding @value{GDBN} command is @samp{stepi}.
26815 @subsubheading Example
26819 -exec-step-instruction
26823 *stopped,reason="end-stepping-range",
26824 frame=@{func="foo",args=[],file="try.c",
26825 fullname="/home/foo/bar/try.c",line="10"@}
26827 -exec-step-instruction
26831 *stopped,reason="end-stepping-range",
26832 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26833 fullname="/home/foo/bar/try.c",line="10"@}
26838 @subheading The @code{-exec-until} Command
26839 @findex -exec-until
26841 @subsubheading Synopsis
26844 -exec-until [ @var{location} ]
26847 Executes the inferior until the @var{location} specified in the
26848 argument is reached. If there is no argument, the inferior executes
26849 until a source line greater than the current one is reached. The
26850 reason for stopping in this case will be @samp{location-reached}.
26852 @subsubheading @value{GDBN} Command
26854 The corresponding @value{GDBN} command is @samp{until}.
26856 @subsubheading Example
26860 -exec-until recursive2.c:6
26864 *stopped,reason="location-reached",frame=@{func="main",args=[],
26865 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26870 @subheading -file-clear
26871 Is this going away????
26874 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26875 @node GDB/MI Stack Manipulation
26876 @section @sc{gdb/mi} Stack Manipulation Commands
26879 @subheading The @code{-stack-info-frame} Command
26880 @findex -stack-info-frame
26882 @subsubheading Synopsis
26888 Get info on the selected frame.
26890 @subsubheading @value{GDBN} Command
26892 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26893 (without arguments).
26895 @subsubheading Example
26900 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26901 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26902 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26906 @subheading The @code{-stack-info-depth} Command
26907 @findex -stack-info-depth
26909 @subsubheading Synopsis
26912 -stack-info-depth [ @var{max-depth} ]
26915 Return the depth of the stack. If the integer argument @var{max-depth}
26916 is specified, do not count beyond @var{max-depth} frames.
26918 @subsubheading @value{GDBN} Command
26920 There's no equivalent @value{GDBN} command.
26922 @subsubheading Example
26924 For a stack with frame levels 0 through 11:
26931 -stack-info-depth 4
26934 -stack-info-depth 12
26937 -stack-info-depth 11
26940 -stack-info-depth 13
26945 @subheading The @code{-stack-list-arguments} Command
26946 @findex -stack-list-arguments
26948 @subsubheading Synopsis
26951 -stack-list-arguments @var{print-values}
26952 [ @var{low-frame} @var{high-frame} ]
26955 Display a list of the arguments for the frames between @var{low-frame}
26956 and @var{high-frame} (inclusive). If @var{low-frame} and
26957 @var{high-frame} are not provided, list the arguments for the whole
26958 call stack. If the two arguments are equal, show the single frame
26959 at the corresponding level. It is an error if @var{low-frame} is
26960 larger than the actual number of frames. On the other hand,
26961 @var{high-frame} may be larger than the actual number of frames, in
26962 which case only existing frames will be returned.
26964 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26965 the variables; if it is 1 or @code{--all-values}, print also their
26966 values; and if it is 2 or @code{--simple-values}, print the name,
26967 type and value for simple data types, and the name and type for arrays,
26968 structures and unions.
26970 Use of this command to obtain arguments in a single frame is
26971 deprecated in favor of the @samp{-stack-list-variables} command.
26973 @subsubheading @value{GDBN} Command
26975 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26976 @samp{gdb_get_args} command which partially overlaps with the
26977 functionality of @samp{-stack-list-arguments}.
26979 @subsubheading Example
26986 frame=@{level="0",addr="0x00010734",func="callee4",
26987 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26988 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26989 frame=@{level="1",addr="0x0001076c",func="callee3",
26990 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26991 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26992 frame=@{level="2",addr="0x0001078c",func="callee2",
26993 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26994 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26995 frame=@{level="3",addr="0x000107b4",func="callee1",
26996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26997 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26998 frame=@{level="4",addr="0x000107e0",func="main",
26999 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27000 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27002 -stack-list-arguments 0
27005 frame=@{level="0",args=[]@},
27006 frame=@{level="1",args=[name="strarg"]@},
27007 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27008 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27009 frame=@{level="4",args=[]@}]
27011 -stack-list-arguments 1
27014 frame=@{level="0",args=[]@},
27016 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27017 frame=@{level="2",args=[
27018 @{name="intarg",value="2"@},
27019 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27020 @{frame=@{level="3",args=[
27021 @{name="intarg",value="2"@},
27022 @{name="strarg",value="0x11940 \"A string argument.\""@},
27023 @{name="fltarg",value="3.5"@}]@},
27024 frame=@{level="4",args=[]@}]
27026 -stack-list-arguments 0 2 2
27027 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27029 -stack-list-arguments 1 2 2
27030 ^done,stack-args=[frame=@{level="2",
27031 args=[@{name="intarg",value="2"@},
27032 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27036 @c @subheading -stack-list-exception-handlers
27039 @subheading The @code{-stack-list-frames} Command
27040 @findex -stack-list-frames
27042 @subsubheading Synopsis
27045 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27048 List the frames currently on the stack. For each frame it displays the
27053 The frame number, 0 being the topmost frame, i.e., the innermost function.
27055 The @code{$pc} value for that frame.
27059 File name of the source file where the function lives.
27060 @item @var{fullname}
27061 The full file name of the source file where the function lives.
27063 Line number corresponding to the @code{$pc}.
27065 The shared library where this function is defined. This is only given
27066 if the frame's function is not known.
27069 If invoked without arguments, this command prints a backtrace for the
27070 whole stack. If given two integer arguments, it shows the frames whose
27071 levels are between the two arguments (inclusive). If the two arguments
27072 are equal, it shows the single frame at the corresponding level. It is
27073 an error if @var{low-frame} is larger than the actual number of
27074 frames. On the other hand, @var{high-frame} may be larger than the
27075 actual number of frames, in which case only existing frames will be returned.
27077 @subsubheading @value{GDBN} Command
27079 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27081 @subsubheading Example
27083 Full stack backtrace:
27089 [frame=@{level="0",addr="0x0001076c",func="foo",
27090 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27091 frame=@{level="1",addr="0x000107a4",func="foo",
27092 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27093 frame=@{level="2",addr="0x000107a4",func="foo",
27094 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27095 frame=@{level="3",addr="0x000107a4",func="foo",
27096 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27097 frame=@{level="4",addr="0x000107a4",func="foo",
27098 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27099 frame=@{level="5",addr="0x000107a4",func="foo",
27100 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27101 frame=@{level="6",addr="0x000107a4",func="foo",
27102 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27103 frame=@{level="7",addr="0x000107a4",func="foo",
27104 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27105 frame=@{level="8",addr="0x000107a4",func="foo",
27106 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27107 frame=@{level="9",addr="0x000107a4",func="foo",
27108 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27109 frame=@{level="10",addr="0x000107a4",func="foo",
27110 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27111 frame=@{level="11",addr="0x00010738",func="main",
27112 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27116 Show frames between @var{low_frame} and @var{high_frame}:
27120 -stack-list-frames 3 5
27122 [frame=@{level="3",addr="0x000107a4",func="foo",
27123 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27124 frame=@{level="4",addr="0x000107a4",func="foo",
27125 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27126 frame=@{level="5",addr="0x000107a4",func="foo",
27127 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27131 Show a single frame:
27135 -stack-list-frames 3 3
27137 [frame=@{level="3",addr="0x000107a4",func="foo",
27138 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27143 @subheading The @code{-stack-list-locals} Command
27144 @findex -stack-list-locals
27146 @subsubheading Synopsis
27149 -stack-list-locals @var{print-values}
27152 Display the local variable names for the selected frame. If
27153 @var{print-values} is 0 or @code{--no-values}, print only the names of
27154 the variables; if it is 1 or @code{--all-values}, print also their
27155 values; and if it is 2 or @code{--simple-values}, print the name,
27156 type and value for simple data types, and the name and type for arrays,
27157 structures and unions. In this last case, a frontend can immediately
27158 display the value of simple data types and create variable objects for
27159 other data types when the user wishes to explore their values in
27162 This command is deprecated in favor of the
27163 @samp{-stack-list-variables} command.
27165 @subsubheading @value{GDBN} Command
27167 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27169 @subsubheading Example
27173 -stack-list-locals 0
27174 ^done,locals=[name="A",name="B",name="C"]
27176 -stack-list-locals --all-values
27177 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27178 @{name="C",value="@{1, 2, 3@}"@}]
27179 -stack-list-locals --simple-values
27180 ^done,locals=[@{name="A",type="int",value="1"@},
27181 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27185 @subheading The @code{-stack-list-variables} Command
27186 @findex -stack-list-variables
27188 @subsubheading Synopsis
27191 -stack-list-variables @var{print-values}
27194 Display the names of local variables and function arguments for the selected frame. If
27195 @var{print-values} is 0 or @code{--no-values}, print only the names of
27196 the variables; if it is 1 or @code{--all-values}, print also their
27197 values; and if it is 2 or @code{--simple-values}, print the name,
27198 type and value for simple data types, and the name and type for arrays,
27199 structures and unions.
27201 @subsubheading Example
27205 -stack-list-variables --thread 1 --frame 0 --all-values
27206 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27211 @subheading The @code{-stack-select-frame} Command
27212 @findex -stack-select-frame
27214 @subsubheading Synopsis
27217 -stack-select-frame @var{framenum}
27220 Change the selected frame. Select a different frame @var{framenum} on
27223 This command in deprecated in favor of passing the @samp{--frame}
27224 option to every command.
27226 @subsubheading @value{GDBN} Command
27228 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27229 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27231 @subsubheading Example
27235 -stack-select-frame 2
27240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27241 @node GDB/MI Variable Objects
27242 @section @sc{gdb/mi} Variable Objects
27246 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27248 For the implementation of a variable debugger window (locals, watched
27249 expressions, etc.), we are proposing the adaptation of the existing code
27250 used by @code{Insight}.
27252 The two main reasons for that are:
27256 It has been proven in practice (it is already on its second generation).
27259 It will shorten development time (needless to say how important it is
27263 The original interface was designed to be used by Tcl code, so it was
27264 slightly changed so it could be used through @sc{gdb/mi}. This section
27265 describes the @sc{gdb/mi} operations that will be available and gives some
27266 hints about their use.
27268 @emph{Note}: In addition to the set of operations described here, we
27269 expect the @sc{gui} implementation of a variable window to require, at
27270 least, the following operations:
27273 @item @code{-gdb-show} @code{output-radix}
27274 @item @code{-stack-list-arguments}
27275 @item @code{-stack-list-locals}
27276 @item @code{-stack-select-frame}
27281 @subheading Introduction to Variable Objects
27283 @cindex variable objects in @sc{gdb/mi}
27285 Variable objects are "object-oriented" MI interface for examining and
27286 changing values of expressions. Unlike some other MI interfaces that
27287 work with expressions, variable objects are specifically designed for
27288 simple and efficient presentation in the frontend. A variable object
27289 is identified by string name. When a variable object is created, the
27290 frontend specifies the expression for that variable object. The
27291 expression can be a simple variable, or it can be an arbitrary complex
27292 expression, and can even involve CPU registers. After creating a
27293 variable object, the frontend can invoke other variable object
27294 operations---for example to obtain or change the value of a variable
27295 object, or to change display format.
27297 Variable objects have hierarchical tree structure. Any variable object
27298 that corresponds to a composite type, such as structure in C, has
27299 a number of child variable objects, for example corresponding to each
27300 element of a structure. A child variable object can itself have
27301 children, recursively. Recursion ends when we reach
27302 leaf variable objects, which always have built-in types. Child variable
27303 objects are created only by explicit request, so if a frontend
27304 is not interested in the children of a particular variable object, no
27305 child will be created.
27307 For a leaf variable object it is possible to obtain its value as a
27308 string, or set the value from a string. String value can be also
27309 obtained for a non-leaf variable object, but it's generally a string
27310 that only indicates the type of the object, and does not list its
27311 contents. Assignment to a non-leaf variable object is not allowed.
27313 A frontend does not need to read the values of all variable objects each time
27314 the program stops. Instead, MI provides an update command that lists all
27315 variable objects whose values has changed since the last update
27316 operation. This considerably reduces the amount of data that must
27317 be transferred to the frontend. As noted above, children variable
27318 objects are created on demand, and only leaf variable objects have a
27319 real value. As result, gdb will read target memory only for leaf
27320 variables that frontend has created.
27322 The automatic update is not always desirable. For example, a frontend
27323 might want to keep a value of some expression for future reference,
27324 and never update it. For another example, fetching memory is
27325 relatively slow for embedded targets, so a frontend might want
27326 to disable automatic update for the variables that are either not
27327 visible on the screen, or ``closed''. This is possible using so
27328 called ``frozen variable objects''. Such variable objects are never
27329 implicitly updated.
27331 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27332 fixed variable object, the expression is parsed when the variable
27333 object is created, including associating identifiers to specific
27334 variables. The meaning of expression never changes. For a floating
27335 variable object the values of variables whose names appear in the
27336 expressions are re-evaluated every time in the context of the current
27337 frame. Consider this example:
27342 struct work_state state;
27349 If a fixed variable object for the @code{state} variable is created in
27350 this function, and we enter the recursive call, the variable
27351 object will report the value of @code{state} in the top-level
27352 @code{do_work} invocation. On the other hand, a floating variable
27353 object will report the value of @code{state} in the current frame.
27355 If an expression specified when creating a fixed variable object
27356 refers to a local variable, the variable object becomes bound to the
27357 thread and frame in which the variable object is created. When such
27358 variable object is updated, @value{GDBN} makes sure that the
27359 thread/frame combination the variable object is bound to still exists,
27360 and re-evaluates the variable object in context of that thread/frame.
27362 The following is the complete set of @sc{gdb/mi} operations defined to
27363 access this functionality:
27365 @multitable @columnfractions .4 .6
27366 @item @strong{Operation}
27367 @tab @strong{Description}
27369 @item @code{-enable-pretty-printing}
27370 @tab enable Python-based pretty-printing
27371 @item @code{-var-create}
27372 @tab create a variable object
27373 @item @code{-var-delete}
27374 @tab delete the variable object and/or its children
27375 @item @code{-var-set-format}
27376 @tab set the display format of this variable
27377 @item @code{-var-show-format}
27378 @tab show the display format of this variable
27379 @item @code{-var-info-num-children}
27380 @tab tells how many children this object has
27381 @item @code{-var-list-children}
27382 @tab return a list of the object's children
27383 @item @code{-var-info-type}
27384 @tab show the type of this variable object
27385 @item @code{-var-info-expression}
27386 @tab print parent-relative expression that this variable object represents
27387 @item @code{-var-info-path-expression}
27388 @tab print full expression that this variable object represents
27389 @item @code{-var-show-attributes}
27390 @tab is this variable editable? does it exist here?
27391 @item @code{-var-evaluate-expression}
27392 @tab get the value of this variable
27393 @item @code{-var-assign}
27394 @tab set the value of this variable
27395 @item @code{-var-update}
27396 @tab update the variable and its children
27397 @item @code{-var-set-frozen}
27398 @tab set frozeness attribute
27399 @item @code{-var-set-update-range}
27400 @tab set range of children to display on update
27403 In the next subsection we describe each operation in detail and suggest
27404 how it can be used.
27406 @subheading Description And Use of Operations on Variable Objects
27408 @subheading The @code{-enable-pretty-printing} Command
27409 @findex -enable-pretty-printing
27412 -enable-pretty-printing
27415 @value{GDBN} allows Python-based visualizers to affect the output of the
27416 MI variable object commands. However, because there was no way to
27417 implement this in a fully backward-compatible way, a front end must
27418 request that this functionality be enabled.
27420 Once enabled, this feature cannot be disabled.
27422 Note that if Python support has not been compiled into @value{GDBN},
27423 this command will still succeed (and do nothing).
27425 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27426 may work differently in future versions of @value{GDBN}.
27428 @subheading The @code{-var-create} Command
27429 @findex -var-create
27431 @subsubheading Synopsis
27434 -var-create @{@var{name} | "-"@}
27435 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27438 This operation creates a variable object, which allows the monitoring of
27439 a variable, the result of an expression, a memory cell or a CPU
27442 The @var{name} parameter is the string by which the object can be
27443 referenced. It must be unique. If @samp{-} is specified, the varobj
27444 system will generate a string ``varNNNNNN'' automatically. It will be
27445 unique provided that one does not specify @var{name} of that format.
27446 The command fails if a duplicate name is found.
27448 The frame under which the expression should be evaluated can be
27449 specified by @var{frame-addr}. A @samp{*} indicates that the current
27450 frame should be used. A @samp{@@} indicates that a floating variable
27451 object must be created.
27453 @var{expression} is any expression valid on the current language set (must not
27454 begin with a @samp{*}), or one of the following:
27458 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27461 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27464 @samp{$@var{regname}} --- a CPU register name
27467 @cindex dynamic varobj
27468 A varobj's contents may be provided by a Python-based pretty-printer. In this
27469 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27470 have slightly different semantics in some cases. If the
27471 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27472 will never create a dynamic varobj. This ensures backward
27473 compatibility for existing clients.
27475 @subsubheading Result
27477 This operation returns attributes of the newly-created varobj. These
27482 The name of the varobj.
27485 The number of children of the varobj. This number is not necessarily
27486 reliable for a dynamic varobj. Instead, you must examine the
27487 @samp{has_more} attribute.
27490 The varobj's scalar value. For a varobj whose type is some sort of
27491 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27492 will not be interesting.
27495 The varobj's type. This is a string representation of the type, as
27496 would be printed by the @value{GDBN} CLI.
27499 If a variable object is bound to a specific thread, then this is the
27500 thread's identifier.
27503 For a dynamic varobj, this indicates whether there appear to be any
27504 children available. For a non-dynamic varobj, this will be 0.
27507 This attribute will be present and have the value @samp{1} if the
27508 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27509 then this attribute will not be present.
27512 A dynamic varobj can supply a display hint to the front end. The
27513 value comes directly from the Python pretty-printer object's
27514 @code{display_hint} method. @xref{Pretty Printing API}.
27517 Typical output will look like this:
27520 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27521 has_more="@var{has_more}"
27525 @subheading The @code{-var-delete} Command
27526 @findex -var-delete
27528 @subsubheading Synopsis
27531 -var-delete [ -c ] @var{name}
27534 Deletes a previously created variable object and all of its children.
27535 With the @samp{-c} option, just deletes the children.
27537 Returns an error if the object @var{name} is not found.
27540 @subheading The @code{-var-set-format} Command
27541 @findex -var-set-format
27543 @subsubheading Synopsis
27546 -var-set-format @var{name} @var{format-spec}
27549 Sets the output format for the value of the object @var{name} to be
27552 @anchor{-var-set-format}
27553 The syntax for the @var{format-spec} is as follows:
27556 @var{format-spec} @expansion{}
27557 @{binary | decimal | hexadecimal | octal | natural@}
27560 The natural format is the default format choosen automatically
27561 based on the variable type (like decimal for an @code{int}, hex
27562 for pointers, etc.).
27564 For a variable with children, the format is set only on the
27565 variable itself, and the children are not affected.
27567 @subheading The @code{-var-show-format} Command
27568 @findex -var-show-format
27570 @subsubheading Synopsis
27573 -var-show-format @var{name}
27576 Returns the format used to display the value of the object @var{name}.
27579 @var{format} @expansion{}
27584 @subheading The @code{-var-info-num-children} Command
27585 @findex -var-info-num-children
27587 @subsubheading Synopsis
27590 -var-info-num-children @var{name}
27593 Returns the number of children of a variable object @var{name}:
27599 Note that this number is not completely reliable for a dynamic varobj.
27600 It will return the current number of children, but more children may
27604 @subheading The @code{-var-list-children} Command
27605 @findex -var-list-children
27607 @subsubheading Synopsis
27610 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27612 @anchor{-var-list-children}
27614 Return a list of the children of the specified variable object and
27615 create variable objects for them, if they do not already exist. With
27616 a single argument or if @var{print-values} has a value of 0 or
27617 @code{--no-values}, print only the names of the variables; if
27618 @var{print-values} is 1 or @code{--all-values}, also print their
27619 values; and if it is 2 or @code{--simple-values} print the name and
27620 value for simple data types and just the name for arrays, structures
27623 @var{from} and @var{to}, if specified, indicate the range of children
27624 to report. If @var{from} or @var{to} is less than zero, the range is
27625 reset and all children will be reported. Otherwise, children starting
27626 at @var{from} (zero-based) and up to and excluding @var{to} will be
27629 If a child range is requested, it will only affect the current call to
27630 @code{-var-list-children}, but not future calls to @code{-var-update}.
27631 For this, you must instead use @code{-var-set-update-range}. The
27632 intent of this approach is to enable a front end to implement any
27633 update approach it likes; for example, scrolling a view may cause the
27634 front end to request more children with @code{-var-list-children}, and
27635 then the front end could call @code{-var-set-update-range} with a
27636 different range to ensure that future updates are restricted to just
27639 For each child the following results are returned:
27644 Name of the variable object created for this child.
27647 The expression to be shown to the user by the front end to designate this child.
27648 For example this may be the name of a structure member.
27650 For a dynamic varobj, this value cannot be used to form an
27651 expression. There is no way to do this at all with a dynamic varobj.
27653 For C/C@t{++} structures there are several pseudo children returned to
27654 designate access qualifiers. For these pseudo children @var{exp} is
27655 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27656 type and value are not present.
27658 A dynamic varobj will not report the access qualifying
27659 pseudo-children, regardless of the language. This information is not
27660 available at all with a dynamic varobj.
27663 Number of children this child has. For a dynamic varobj, this will be
27667 The type of the child.
27670 If values were requested, this is the value.
27673 If this variable object is associated with a thread, this is the thread id.
27674 Otherwise this result is not present.
27677 If the variable object is frozen, this variable will be present with a value of 1.
27680 The result may have its own attributes:
27684 A dynamic varobj can supply a display hint to the front end. The
27685 value comes directly from the Python pretty-printer object's
27686 @code{display_hint} method. @xref{Pretty Printing API}.
27689 This is an integer attribute which is nonzero if there are children
27690 remaining after the end of the selected range.
27693 @subsubheading Example
27697 -var-list-children n
27698 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27699 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27701 -var-list-children --all-values n
27702 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27703 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27707 @subheading The @code{-var-info-type} Command
27708 @findex -var-info-type
27710 @subsubheading Synopsis
27713 -var-info-type @var{name}
27716 Returns the type of the specified variable @var{name}. The type is
27717 returned as a string in the same format as it is output by the
27721 type=@var{typename}
27725 @subheading The @code{-var-info-expression} Command
27726 @findex -var-info-expression
27728 @subsubheading Synopsis
27731 -var-info-expression @var{name}
27734 Returns a string that is suitable for presenting this
27735 variable object in user interface. The string is generally
27736 not valid expression in the current language, and cannot be evaluated.
27738 For example, if @code{a} is an array, and variable object
27739 @code{A} was created for @code{a}, then we'll get this output:
27742 (gdb) -var-info-expression A.1
27743 ^done,lang="C",exp="1"
27747 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27749 Note that the output of the @code{-var-list-children} command also
27750 includes those expressions, so the @code{-var-info-expression} command
27753 @subheading The @code{-var-info-path-expression} Command
27754 @findex -var-info-path-expression
27756 @subsubheading Synopsis
27759 -var-info-path-expression @var{name}
27762 Returns an expression that can be evaluated in the current
27763 context and will yield the same value that a variable object has.
27764 Compare this with the @code{-var-info-expression} command, which
27765 result can be used only for UI presentation. Typical use of
27766 the @code{-var-info-path-expression} command is creating a
27767 watchpoint from a variable object.
27769 This command is currently not valid for children of a dynamic varobj,
27770 and will give an error when invoked on one.
27772 For example, suppose @code{C} is a C@t{++} class, derived from class
27773 @code{Base}, and that the @code{Base} class has a member called
27774 @code{m_size}. Assume a variable @code{c} is has the type of
27775 @code{C} and a variable object @code{C} was created for variable
27776 @code{c}. Then, we'll get this output:
27778 (gdb) -var-info-path-expression C.Base.public.m_size
27779 ^done,path_expr=((Base)c).m_size)
27782 @subheading The @code{-var-show-attributes} Command
27783 @findex -var-show-attributes
27785 @subsubheading Synopsis
27788 -var-show-attributes @var{name}
27791 List attributes of the specified variable object @var{name}:
27794 status=@var{attr} [ ( ,@var{attr} )* ]
27798 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27800 @subheading The @code{-var-evaluate-expression} Command
27801 @findex -var-evaluate-expression
27803 @subsubheading Synopsis
27806 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27809 Evaluates the expression that is represented by the specified variable
27810 object and returns its value as a string. The format of the string
27811 can be specified with the @samp{-f} option. The possible values of
27812 this option are the same as for @code{-var-set-format}
27813 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27814 the current display format will be used. The current display format
27815 can be changed using the @code{-var-set-format} command.
27821 Note that one must invoke @code{-var-list-children} for a variable
27822 before the value of a child variable can be evaluated.
27824 @subheading The @code{-var-assign} Command
27825 @findex -var-assign
27827 @subsubheading Synopsis
27830 -var-assign @var{name} @var{expression}
27833 Assigns the value of @var{expression} to the variable object specified
27834 by @var{name}. The object must be @samp{editable}. If the variable's
27835 value is altered by the assign, the variable will show up in any
27836 subsequent @code{-var-update} list.
27838 @subsubheading Example
27846 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27850 @subheading The @code{-var-update} Command
27851 @findex -var-update
27853 @subsubheading Synopsis
27856 -var-update [@var{print-values}] @{@var{name} | "*"@}
27859 Reevaluate the expressions corresponding to the variable object
27860 @var{name} and all its direct and indirect children, and return the
27861 list of variable objects whose values have changed; @var{name} must
27862 be a root variable object. Here, ``changed'' means that the result of
27863 @code{-var-evaluate-expression} before and after the
27864 @code{-var-update} is different. If @samp{*} is used as the variable
27865 object names, all existing variable objects are updated, except
27866 for frozen ones (@pxref{-var-set-frozen}). The option
27867 @var{print-values} determines whether both names and values, or just
27868 names are printed. The possible values of this option are the same
27869 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27870 recommended to use the @samp{--all-values} option, to reduce the
27871 number of MI commands needed on each program stop.
27873 With the @samp{*} parameter, if a variable object is bound to a
27874 currently running thread, it will not be updated, without any
27877 If @code{-var-set-update-range} was previously used on a varobj, then
27878 only the selected range of children will be reported.
27880 @code{-var-update} reports all the changed varobjs in a tuple named
27883 Each item in the change list is itself a tuple holding:
27887 The name of the varobj.
27890 If values were requested for this update, then this field will be
27891 present and will hold the value of the varobj.
27894 @anchor{-var-update}
27895 This field is a string which may take one of three values:
27899 The variable object's current value is valid.
27902 The variable object does not currently hold a valid value but it may
27903 hold one in the future if its associated expression comes back into
27907 The variable object no longer holds a valid value.
27908 This can occur when the executable file being debugged has changed,
27909 either through recompilation or by using the @value{GDBN} @code{file}
27910 command. The front end should normally choose to delete these variable
27914 In the future new values may be added to this list so the front should
27915 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27918 This is only present if the varobj is still valid. If the type
27919 changed, then this will be the string @samp{true}; otherwise it will
27923 If the varobj's type changed, then this field will be present and will
27926 @item new_num_children
27927 For a dynamic varobj, if the number of children changed, or if the
27928 type changed, this will be the new number of children.
27930 The @samp{numchild} field in other varobj responses is generally not
27931 valid for a dynamic varobj -- it will show the number of children that
27932 @value{GDBN} knows about, but because dynamic varobjs lazily
27933 instantiate their children, this will not reflect the number of
27934 children which may be available.
27936 The @samp{new_num_children} attribute only reports changes to the
27937 number of children known by @value{GDBN}. This is the only way to
27938 detect whether an update has removed children (which necessarily can
27939 only happen at the end of the update range).
27942 The display hint, if any.
27945 This is an integer value, which will be 1 if there are more children
27946 available outside the varobj's update range.
27949 This attribute will be present and have the value @samp{1} if the
27950 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27951 then this attribute will not be present.
27954 If new children were added to a dynamic varobj within the selected
27955 update range (as set by @code{-var-set-update-range}), then they will
27956 be listed in this attribute.
27959 @subsubheading Example
27966 -var-update --all-values var1
27967 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27968 type_changed="false"@}]
27972 @subheading The @code{-var-set-frozen} Command
27973 @findex -var-set-frozen
27974 @anchor{-var-set-frozen}
27976 @subsubheading Synopsis
27979 -var-set-frozen @var{name} @var{flag}
27982 Set the frozenness flag on the variable object @var{name}. The
27983 @var{flag} parameter should be either @samp{1} to make the variable
27984 frozen or @samp{0} to make it unfrozen. If a variable object is
27985 frozen, then neither itself, nor any of its children, are
27986 implicitly updated by @code{-var-update} of
27987 a parent variable or by @code{-var-update *}. Only
27988 @code{-var-update} of the variable itself will update its value and
27989 values of its children. After a variable object is unfrozen, it is
27990 implicitly updated by all subsequent @code{-var-update} operations.
27991 Unfreezing a variable does not update it, only subsequent
27992 @code{-var-update} does.
27994 @subsubheading Example
27998 -var-set-frozen V 1
28003 @subheading The @code{-var-set-update-range} command
28004 @findex -var-set-update-range
28005 @anchor{-var-set-update-range}
28007 @subsubheading Synopsis
28010 -var-set-update-range @var{name} @var{from} @var{to}
28013 Set the range of children to be returned by future invocations of
28014 @code{-var-update}.
28016 @var{from} and @var{to} indicate the range of children to report. If
28017 @var{from} or @var{to} is less than zero, the range is reset and all
28018 children will be reported. Otherwise, children starting at @var{from}
28019 (zero-based) and up to and excluding @var{to} will be reported.
28021 @subsubheading Example
28025 -var-set-update-range V 1 2
28029 @subheading The @code{-var-set-visualizer} command
28030 @findex -var-set-visualizer
28031 @anchor{-var-set-visualizer}
28033 @subsubheading Synopsis
28036 -var-set-visualizer @var{name} @var{visualizer}
28039 Set a visualizer for the variable object @var{name}.
28041 @var{visualizer} is the visualizer to use. The special value
28042 @samp{None} means to disable any visualizer in use.
28044 If not @samp{None}, @var{visualizer} must be a Python expression.
28045 This expression must evaluate to a callable object which accepts a
28046 single argument. @value{GDBN} will call this object with the value of
28047 the varobj @var{name} as an argument (this is done so that the same
28048 Python pretty-printing code can be used for both the CLI and MI).
28049 When called, this object must return an object which conforms to the
28050 pretty-printing interface (@pxref{Pretty Printing API}).
28052 The pre-defined function @code{gdb.default_visualizer} may be used to
28053 select a visualizer by following the built-in process
28054 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28055 a varobj is created, and so ordinarily is not needed.
28057 This feature is only available if Python support is enabled. The MI
28058 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28059 can be used to check this.
28061 @subsubheading Example
28063 Resetting the visualizer:
28067 -var-set-visualizer V None
28071 Reselecting the default (type-based) visualizer:
28075 -var-set-visualizer V gdb.default_visualizer
28079 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28080 can be used to instantiate this class for a varobj:
28084 -var-set-visualizer V "lambda val: SomeClass()"
28088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28089 @node GDB/MI Data Manipulation
28090 @section @sc{gdb/mi} Data Manipulation
28092 @cindex data manipulation, in @sc{gdb/mi}
28093 @cindex @sc{gdb/mi}, data manipulation
28094 This section describes the @sc{gdb/mi} commands that manipulate data:
28095 examine memory and registers, evaluate expressions, etc.
28097 @c REMOVED FROM THE INTERFACE.
28098 @c @subheading -data-assign
28099 @c Change the value of a program variable. Plenty of side effects.
28100 @c @subsubheading GDB Command
28102 @c @subsubheading Example
28105 @subheading The @code{-data-disassemble} Command
28106 @findex -data-disassemble
28108 @subsubheading Synopsis
28112 [ -s @var{start-addr} -e @var{end-addr} ]
28113 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28121 @item @var{start-addr}
28122 is the beginning address (or @code{$pc})
28123 @item @var{end-addr}
28125 @item @var{filename}
28126 is the name of the file to disassemble
28127 @item @var{linenum}
28128 is the line number to disassemble around
28130 is the number of disassembly lines to be produced. If it is -1,
28131 the whole function will be disassembled, in case no @var{end-addr} is
28132 specified. If @var{end-addr} is specified as a non-zero value, and
28133 @var{lines} is lower than the number of disassembly lines between
28134 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28135 displayed; if @var{lines} is higher than the number of lines between
28136 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28139 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28140 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28141 mixed source and disassembly with raw opcodes).
28144 @subsubheading Result
28146 The output for each instruction is composed of four fields:
28155 Note that whatever included in the instruction field, is not manipulated
28156 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28158 @subsubheading @value{GDBN} Command
28160 There's no direct mapping from this command to the CLI.
28162 @subsubheading Example
28164 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28168 -data-disassemble -s $pc -e "$pc + 20" -- 0
28171 @{address="0x000107c0",func-name="main",offset="4",
28172 inst="mov 2, %o0"@},
28173 @{address="0x000107c4",func-name="main",offset="8",
28174 inst="sethi %hi(0x11800), %o2"@},
28175 @{address="0x000107c8",func-name="main",offset="12",
28176 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28177 @{address="0x000107cc",func-name="main",offset="16",
28178 inst="sethi %hi(0x11800), %o2"@},
28179 @{address="0x000107d0",func-name="main",offset="20",
28180 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28184 Disassemble the whole @code{main} function. Line 32 is part of
28188 -data-disassemble -f basics.c -l 32 -- 0
28190 @{address="0x000107bc",func-name="main",offset="0",
28191 inst="save %sp, -112, %sp"@},
28192 @{address="0x000107c0",func-name="main",offset="4",
28193 inst="mov 2, %o0"@},
28194 @{address="0x000107c4",func-name="main",offset="8",
28195 inst="sethi %hi(0x11800), %o2"@},
28197 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28198 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28202 Disassemble 3 instructions from the start of @code{main}:
28206 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28208 @{address="0x000107bc",func-name="main",offset="0",
28209 inst="save %sp, -112, %sp"@},
28210 @{address="0x000107c0",func-name="main",offset="4",
28211 inst="mov 2, %o0"@},
28212 @{address="0x000107c4",func-name="main",offset="8",
28213 inst="sethi %hi(0x11800), %o2"@}]
28217 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28221 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28223 src_and_asm_line=@{line="31",
28224 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28225 testsuite/gdb.mi/basics.c",line_asm_insn=[
28226 @{address="0x000107bc",func-name="main",offset="0",
28227 inst="save %sp, -112, %sp"@}]@},
28228 src_and_asm_line=@{line="32",
28229 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28230 testsuite/gdb.mi/basics.c",line_asm_insn=[
28231 @{address="0x000107c0",func-name="main",offset="4",
28232 inst="mov 2, %o0"@},
28233 @{address="0x000107c4",func-name="main",offset="8",
28234 inst="sethi %hi(0x11800), %o2"@}]@}]
28239 @subheading The @code{-data-evaluate-expression} Command
28240 @findex -data-evaluate-expression
28242 @subsubheading Synopsis
28245 -data-evaluate-expression @var{expr}
28248 Evaluate @var{expr} as an expression. The expression could contain an
28249 inferior function call. The function call will execute synchronously.
28250 If the expression contains spaces, it must be enclosed in double quotes.
28252 @subsubheading @value{GDBN} Command
28254 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28255 @samp{call}. In @code{gdbtk} only, there's a corresponding
28256 @samp{gdb_eval} command.
28258 @subsubheading Example
28260 In the following example, the numbers that precede the commands are the
28261 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28262 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28266 211-data-evaluate-expression A
28269 311-data-evaluate-expression &A
28270 311^done,value="0xefffeb7c"
28272 411-data-evaluate-expression A+3
28275 511-data-evaluate-expression "A + 3"
28281 @subheading The @code{-data-list-changed-registers} Command
28282 @findex -data-list-changed-registers
28284 @subsubheading Synopsis
28287 -data-list-changed-registers
28290 Display a list of the registers that have changed.
28292 @subsubheading @value{GDBN} Command
28294 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28295 has the corresponding command @samp{gdb_changed_register_list}.
28297 @subsubheading Example
28299 On a PPC MBX board:
28307 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28308 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28311 -data-list-changed-registers
28312 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28313 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28314 "24","25","26","27","28","30","31","64","65","66","67","69"]
28319 @subheading The @code{-data-list-register-names} Command
28320 @findex -data-list-register-names
28322 @subsubheading Synopsis
28325 -data-list-register-names [ ( @var{regno} )+ ]
28328 Show a list of register names for the current target. If no arguments
28329 are given, it shows a list of the names of all the registers. If
28330 integer numbers are given as arguments, it will print a list of the
28331 names of the registers corresponding to the arguments. To ensure
28332 consistency between a register name and its number, the output list may
28333 include empty register names.
28335 @subsubheading @value{GDBN} Command
28337 @value{GDBN} does not have a command which corresponds to
28338 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28339 corresponding command @samp{gdb_regnames}.
28341 @subsubheading Example
28343 For the PPC MBX board:
28346 -data-list-register-names
28347 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28348 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28349 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28350 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28351 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28352 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28353 "", "pc","ps","cr","lr","ctr","xer"]
28355 -data-list-register-names 1 2 3
28356 ^done,register-names=["r1","r2","r3"]
28360 @subheading The @code{-data-list-register-values} Command
28361 @findex -data-list-register-values
28363 @subsubheading Synopsis
28366 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28369 Display the registers' contents. @var{fmt} is the format according to
28370 which the registers' contents are to be returned, followed by an optional
28371 list of numbers specifying the registers to display. A missing list of
28372 numbers indicates that the contents of all the registers must be returned.
28374 Allowed formats for @var{fmt} are:
28391 @subsubheading @value{GDBN} Command
28393 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28394 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28396 @subsubheading Example
28398 For a PPC MBX board (note: line breaks are for readability only, they
28399 don't appear in the actual output):
28403 -data-list-register-values r 64 65
28404 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28405 @{number="65",value="0x00029002"@}]
28407 -data-list-register-values x
28408 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28409 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28410 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28411 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28412 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28413 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28414 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28415 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28416 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28417 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28418 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28419 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28420 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28421 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28422 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28423 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28424 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28425 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28426 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28427 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28428 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28429 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28430 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28431 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28432 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28433 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28434 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28435 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28436 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28437 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28438 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28439 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28440 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28441 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28442 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28443 @{number="69",value="0x20002b03"@}]
28448 @subheading The @code{-data-read-memory} Command
28449 @findex -data-read-memory
28451 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28453 @subsubheading Synopsis
28456 -data-read-memory [ -o @var{byte-offset} ]
28457 @var{address} @var{word-format} @var{word-size}
28458 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28465 @item @var{address}
28466 An expression specifying the address of the first memory word to be
28467 read. Complex expressions containing embedded white space should be
28468 quoted using the C convention.
28470 @item @var{word-format}
28471 The format to be used to print the memory words. The notation is the
28472 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28475 @item @var{word-size}
28476 The size of each memory word in bytes.
28478 @item @var{nr-rows}
28479 The number of rows in the output table.
28481 @item @var{nr-cols}
28482 The number of columns in the output table.
28485 If present, indicates that each row should include an @sc{ascii} dump. The
28486 value of @var{aschar} is used as a padding character when a byte is not a
28487 member of the printable @sc{ascii} character set (printable @sc{ascii}
28488 characters are those whose code is between 32 and 126, inclusively).
28490 @item @var{byte-offset}
28491 An offset to add to the @var{address} before fetching memory.
28494 This command displays memory contents as a table of @var{nr-rows} by
28495 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28496 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28497 (returned as @samp{total-bytes}). Should less than the requested number
28498 of bytes be returned by the target, the missing words are identified
28499 using @samp{N/A}. The number of bytes read from the target is returned
28500 in @samp{nr-bytes} and the starting address used to read memory in
28503 The address of the next/previous row or page is available in
28504 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28507 @subsubheading @value{GDBN} Command
28509 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28510 @samp{gdb_get_mem} memory read command.
28512 @subsubheading Example
28514 Read six bytes of memory starting at @code{bytes+6} but then offset by
28515 @code{-6} bytes. Format as three rows of two columns. One byte per
28516 word. Display each word in hex.
28520 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28521 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28522 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28523 prev-page="0x0000138a",memory=[
28524 @{addr="0x00001390",data=["0x00","0x01"]@},
28525 @{addr="0x00001392",data=["0x02","0x03"]@},
28526 @{addr="0x00001394",data=["0x04","0x05"]@}]
28530 Read two bytes of memory starting at address @code{shorts + 64} and
28531 display as a single word formatted in decimal.
28535 5-data-read-memory shorts+64 d 2 1 1
28536 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28537 next-row="0x00001512",prev-row="0x0000150e",
28538 next-page="0x00001512",prev-page="0x0000150e",memory=[
28539 @{addr="0x00001510",data=["128"]@}]
28543 Read thirty two bytes of memory starting at @code{bytes+16} and format
28544 as eight rows of four columns. Include a string encoding with @samp{x}
28545 used as the non-printable character.
28549 4-data-read-memory bytes+16 x 1 8 4 x
28550 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28551 next-row="0x000013c0",prev-row="0x0000139c",
28552 next-page="0x000013c0",prev-page="0x00001380",memory=[
28553 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28554 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28555 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28556 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28557 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28558 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28559 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28560 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28564 @subheading The @code{-data-read-memory-bytes} Command
28565 @findex -data-read-memory-bytes
28567 @subsubheading Synopsis
28570 -data-read-memory-bytes [ -o @var{byte-offset} ]
28571 @var{address} @var{count}
28578 @item @var{address}
28579 An expression specifying the address of the first memory word to be
28580 read. Complex expressions containing embedded white space should be
28581 quoted using the C convention.
28584 The number of bytes to read. This should be an integer literal.
28586 @item @var{byte-offset}
28587 The offsets in bytes relative to @var{address} at which to start
28588 reading. This should be an integer literal. This option is provided
28589 so that a frontend is not required to first evaluate address and then
28590 perform address arithmetics itself.
28594 This command attempts to read all accessible memory regions in the
28595 specified range. First, all regions marked as unreadable in the memory
28596 map (if one is defined) will be skipped. @xref{Memory Region
28597 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28598 regions. For each one, if reading full region results in an errors,
28599 @value{GDBN} will try to read a subset of the region.
28601 In general, every single byte in the region may be readable or not,
28602 and the only way to read every readable byte is to try a read at
28603 every address, which is not practical. Therefore, @value{GDBN} will
28604 attempt to read all accessible bytes at either beginning or the end
28605 of the region, using a binary division scheme. This heuristic works
28606 well for reading accross a memory map boundary. Note that if a region
28607 has a readable range that is neither at the beginning or the end,
28608 @value{GDBN} will not read it.
28610 The result record (@pxref{GDB/MI Result Records}) that is output of
28611 the command includes a field named @samp{memory} whose content is a
28612 list of tuples. Each tuple represent a successfully read memory block
28613 and has the following fields:
28617 The start address of the memory block, as hexadecimal literal.
28620 The end address of the memory block, as hexadecimal literal.
28623 The offset of the memory block, as hexadecimal literal, relative to
28624 the start address passed to @code{-data-read-memory-bytes}.
28627 The contents of the memory block, in hex.
28633 @subsubheading @value{GDBN} Command
28635 The corresponding @value{GDBN} command is @samp{x}.
28637 @subsubheading Example
28641 -data-read-memory-bytes &a 10
28642 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28644 contents="01000000020000000300"@}]
28649 @subheading The @code{-data-write-memory-bytes} Command
28650 @findex -data-write-memory-bytes
28652 @subsubheading Synopsis
28655 -data-write-memory-bytes @var{address} @var{contents}
28662 @item @var{address}
28663 An expression specifying the address of the first memory word to be
28664 read. Complex expressions containing embedded white space should be
28665 quoted using the C convention.
28667 @item @var{contents}
28668 The hex-encoded bytes to write.
28672 @subsubheading @value{GDBN} Command
28674 There's no corresponding @value{GDBN} command.
28676 @subsubheading Example
28680 -data-write-memory-bytes &a "aabbccdd"
28686 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28687 @node GDB/MI Tracepoint Commands
28688 @section @sc{gdb/mi} Tracepoint Commands
28690 The commands defined in this section implement MI support for
28691 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28693 @subheading The @code{-trace-find} Command
28694 @findex -trace-find
28696 @subsubheading Synopsis
28699 -trace-find @var{mode} [@var{parameters}@dots{}]
28702 Find a trace frame using criteria defined by @var{mode} and
28703 @var{parameters}. The following table lists permissible
28704 modes and their parameters. For details of operation, see @ref{tfind}.
28709 No parameters are required. Stops examining trace frames.
28712 An integer is required as parameter. Selects tracepoint frame with
28715 @item tracepoint-number
28716 An integer is required as parameter. Finds next
28717 trace frame that corresponds to tracepoint with the specified number.
28720 An address is required as parameter. Finds
28721 next trace frame that corresponds to any tracepoint at the specified
28724 @item pc-inside-range
28725 Two addresses are required as parameters. Finds next trace
28726 frame that corresponds to a tracepoint at an address inside the
28727 specified range. Both bounds are considered to be inside the range.
28729 @item pc-outside-range
28730 Two addresses are required as parameters. Finds
28731 next trace frame that corresponds to a tracepoint at an address outside
28732 the specified range. Both bounds are considered to be inside the range.
28735 Line specification is required as parameter. @xref{Specify Location}.
28736 Finds next trace frame that corresponds to a tracepoint at
28737 the specified location.
28741 If @samp{none} was passed as @var{mode}, the response does not
28742 have fields. Otherwise, the response may have the following fields:
28746 This field has either @samp{0} or @samp{1} as the value, depending
28747 on whether a matching tracepoint was found.
28750 The index of the found traceframe. This field is present iff
28751 the @samp{found} field has value of @samp{1}.
28754 The index of the found tracepoint. This field is present iff
28755 the @samp{found} field has value of @samp{1}.
28758 The information about the frame corresponding to the found trace
28759 frame. This field is present only if a trace frame was found.
28760 @xref{GDB/MI Frame Information}, for description of this field.
28764 @subsubheading @value{GDBN} Command
28766 The corresponding @value{GDBN} command is @samp{tfind}.
28768 @subheading -trace-define-variable
28769 @findex -trace-define-variable
28771 @subsubheading Synopsis
28774 -trace-define-variable @var{name} [ @var{value} ]
28777 Create trace variable @var{name} if it does not exist. If
28778 @var{value} is specified, sets the initial value of the specified
28779 trace variable to that value. Note that the @var{name} should start
28780 with the @samp{$} character.
28782 @subsubheading @value{GDBN} Command
28784 The corresponding @value{GDBN} command is @samp{tvariable}.
28786 @subheading -trace-list-variables
28787 @findex -trace-list-variables
28789 @subsubheading Synopsis
28792 -trace-list-variables
28795 Return a table of all defined trace variables. Each element of the
28796 table has the following fields:
28800 The name of the trace variable. This field is always present.
28803 The initial value. This is a 64-bit signed integer. This
28804 field is always present.
28807 The value the trace variable has at the moment. This is a 64-bit
28808 signed integer. This field is absent iff current value is
28809 not defined, for example if the trace was never run, or is
28814 @subsubheading @value{GDBN} Command
28816 The corresponding @value{GDBN} command is @samp{tvariables}.
28818 @subsubheading Example
28822 -trace-list-variables
28823 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28824 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28825 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28826 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28827 body=[variable=@{name="$trace_timestamp",initial="0"@}
28828 variable=@{name="$foo",initial="10",current="15"@}]@}
28832 @subheading -trace-save
28833 @findex -trace-save
28835 @subsubheading Synopsis
28838 -trace-save [-r ] @var{filename}
28841 Saves the collected trace data to @var{filename}. Without the
28842 @samp{-r} option, the data is downloaded from the target and saved
28843 in a local file. With the @samp{-r} option the target is asked
28844 to perform the save.
28846 @subsubheading @value{GDBN} Command
28848 The corresponding @value{GDBN} command is @samp{tsave}.
28851 @subheading -trace-start
28852 @findex -trace-start
28854 @subsubheading Synopsis
28860 Starts a tracing experiments. The result of this command does not
28863 @subsubheading @value{GDBN} Command
28865 The corresponding @value{GDBN} command is @samp{tstart}.
28867 @subheading -trace-status
28868 @findex -trace-status
28870 @subsubheading Synopsis
28876 Obtains the status of a tracing experiment. The result may include
28877 the following fields:
28882 May have a value of either @samp{0}, when no tracing operations are
28883 supported, @samp{1}, when all tracing operations are supported, or
28884 @samp{file} when examining trace file. In the latter case, examining
28885 of trace frame is possible but new tracing experiement cannot be
28886 started. This field is always present.
28889 May have a value of either @samp{0} or @samp{1} depending on whether
28890 tracing experiement is in progress on target. This field is present
28891 if @samp{supported} field is not @samp{0}.
28894 Report the reason why the tracing was stopped last time. This field
28895 may be absent iff tracing was never stopped on target yet. The
28896 value of @samp{request} means the tracing was stopped as result of
28897 the @code{-trace-stop} command. The value of @samp{overflow} means
28898 the tracing buffer is full. The value of @samp{disconnection} means
28899 tracing was automatically stopped when @value{GDBN} has disconnected.
28900 The value of @samp{passcount} means tracing was stopped when a
28901 tracepoint was passed a maximal number of times for that tracepoint.
28902 This field is present if @samp{supported} field is not @samp{0}.
28904 @item stopping-tracepoint
28905 The number of tracepoint whose passcount as exceeded. This field is
28906 present iff the @samp{stop-reason} field has the value of
28910 @itemx frames-created
28911 The @samp{frames} field is a count of the total number of trace frames
28912 in the trace buffer, while @samp{frames-created} is the total created
28913 during the run, including ones that were discarded, such as when a
28914 circular trace buffer filled up. Both fields are optional.
28918 These fields tell the current size of the tracing buffer and the
28919 remaining space. These fields are optional.
28922 The value of the circular trace buffer flag. @code{1} means that the
28923 trace buffer is circular and old trace frames will be discarded if
28924 necessary to make room, @code{0} means that the trace buffer is linear
28928 The value of the disconnected tracing flag. @code{1} means that
28929 tracing will continue after @value{GDBN} disconnects, @code{0} means
28930 that the trace run will stop.
28934 @subsubheading @value{GDBN} Command
28936 The corresponding @value{GDBN} command is @samp{tstatus}.
28938 @subheading -trace-stop
28939 @findex -trace-stop
28941 @subsubheading Synopsis
28947 Stops a tracing experiment. The result of this command has the same
28948 fields as @code{-trace-status}, except that the @samp{supported} and
28949 @samp{running} fields are not output.
28951 @subsubheading @value{GDBN} Command
28953 The corresponding @value{GDBN} command is @samp{tstop}.
28956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28957 @node GDB/MI Symbol Query
28958 @section @sc{gdb/mi} Symbol Query Commands
28962 @subheading The @code{-symbol-info-address} Command
28963 @findex -symbol-info-address
28965 @subsubheading Synopsis
28968 -symbol-info-address @var{symbol}
28971 Describe where @var{symbol} is stored.
28973 @subsubheading @value{GDBN} Command
28975 The corresponding @value{GDBN} command is @samp{info address}.
28977 @subsubheading Example
28981 @subheading The @code{-symbol-info-file} Command
28982 @findex -symbol-info-file
28984 @subsubheading Synopsis
28990 Show the file for the symbol.
28992 @subsubheading @value{GDBN} Command
28994 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28995 @samp{gdb_find_file}.
28997 @subsubheading Example
29001 @subheading The @code{-symbol-info-function} Command
29002 @findex -symbol-info-function
29004 @subsubheading Synopsis
29007 -symbol-info-function
29010 Show which function the symbol lives in.
29012 @subsubheading @value{GDBN} Command
29014 @samp{gdb_get_function} in @code{gdbtk}.
29016 @subsubheading Example
29020 @subheading The @code{-symbol-info-line} Command
29021 @findex -symbol-info-line
29023 @subsubheading Synopsis
29029 Show the core addresses of the code for a source line.
29031 @subsubheading @value{GDBN} Command
29033 The corresponding @value{GDBN} command is @samp{info line}.
29034 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29036 @subsubheading Example
29040 @subheading The @code{-symbol-info-symbol} Command
29041 @findex -symbol-info-symbol
29043 @subsubheading Synopsis
29046 -symbol-info-symbol @var{addr}
29049 Describe what symbol is at location @var{addr}.
29051 @subsubheading @value{GDBN} Command
29053 The corresponding @value{GDBN} command is @samp{info symbol}.
29055 @subsubheading Example
29059 @subheading The @code{-symbol-list-functions} Command
29060 @findex -symbol-list-functions
29062 @subsubheading Synopsis
29065 -symbol-list-functions
29068 List the functions in the executable.
29070 @subsubheading @value{GDBN} Command
29072 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29073 @samp{gdb_search} in @code{gdbtk}.
29075 @subsubheading Example
29080 @subheading The @code{-symbol-list-lines} Command
29081 @findex -symbol-list-lines
29083 @subsubheading Synopsis
29086 -symbol-list-lines @var{filename}
29089 Print the list of lines that contain code and their associated program
29090 addresses for the given source filename. The entries are sorted in
29091 ascending PC order.
29093 @subsubheading @value{GDBN} Command
29095 There is no corresponding @value{GDBN} command.
29097 @subsubheading Example
29100 -symbol-list-lines basics.c
29101 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29107 @subheading The @code{-symbol-list-types} Command
29108 @findex -symbol-list-types
29110 @subsubheading Synopsis
29116 List all the type names.
29118 @subsubheading @value{GDBN} Command
29120 The corresponding commands are @samp{info types} in @value{GDBN},
29121 @samp{gdb_search} in @code{gdbtk}.
29123 @subsubheading Example
29127 @subheading The @code{-symbol-list-variables} Command
29128 @findex -symbol-list-variables
29130 @subsubheading Synopsis
29133 -symbol-list-variables
29136 List all the global and static variable names.
29138 @subsubheading @value{GDBN} Command
29140 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29142 @subsubheading Example
29146 @subheading The @code{-symbol-locate} Command
29147 @findex -symbol-locate
29149 @subsubheading Synopsis
29155 @subsubheading @value{GDBN} Command
29157 @samp{gdb_loc} in @code{gdbtk}.
29159 @subsubheading Example
29163 @subheading The @code{-symbol-type} Command
29164 @findex -symbol-type
29166 @subsubheading Synopsis
29169 -symbol-type @var{variable}
29172 Show type of @var{variable}.
29174 @subsubheading @value{GDBN} Command
29176 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29177 @samp{gdb_obj_variable}.
29179 @subsubheading Example
29184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29185 @node GDB/MI File Commands
29186 @section @sc{gdb/mi} File Commands
29188 This section describes the GDB/MI commands to specify executable file names
29189 and to read in and obtain symbol table information.
29191 @subheading The @code{-file-exec-and-symbols} Command
29192 @findex -file-exec-and-symbols
29194 @subsubheading Synopsis
29197 -file-exec-and-symbols @var{file}
29200 Specify the executable file to be debugged. This file is the one from
29201 which the symbol table is also read. If no file is specified, the
29202 command clears the executable and symbol information. If breakpoints
29203 are set when using this command with no arguments, @value{GDBN} will produce
29204 error messages. Otherwise, no output is produced, except a completion
29207 @subsubheading @value{GDBN} Command
29209 The corresponding @value{GDBN} command is @samp{file}.
29211 @subsubheading Example
29215 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29221 @subheading The @code{-file-exec-file} Command
29222 @findex -file-exec-file
29224 @subsubheading Synopsis
29227 -file-exec-file @var{file}
29230 Specify the executable file to be debugged. Unlike
29231 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29232 from this file. If used without argument, @value{GDBN} clears the information
29233 about the executable file. No output is produced, except a completion
29236 @subsubheading @value{GDBN} Command
29238 The corresponding @value{GDBN} command is @samp{exec-file}.
29240 @subsubheading Example
29244 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29251 @subheading The @code{-file-list-exec-sections} Command
29252 @findex -file-list-exec-sections
29254 @subsubheading Synopsis
29257 -file-list-exec-sections
29260 List the sections of the current executable file.
29262 @subsubheading @value{GDBN} Command
29264 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29265 information as this command. @code{gdbtk} has a corresponding command
29266 @samp{gdb_load_info}.
29268 @subsubheading Example
29273 @subheading The @code{-file-list-exec-source-file} Command
29274 @findex -file-list-exec-source-file
29276 @subsubheading Synopsis
29279 -file-list-exec-source-file
29282 List the line number, the current source file, and the absolute path
29283 to the current source file for the current executable. The macro
29284 information field has a value of @samp{1} or @samp{0} depending on
29285 whether or not the file includes preprocessor macro information.
29287 @subsubheading @value{GDBN} Command
29289 The @value{GDBN} equivalent is @samp{info source}
29291 @subsubheading Example
29295 123-file-list-exec-source-file
29296 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29301 @subheading The @code{-file-list-exec-source-files} Command
29302 @findex -file-list-exec-source-files
29304 @subsubheading Synopsis
29307 -file-list-exec-source-files
29310 List the source files for the current executable.
29312 It will always output the filename, but only when @value{GDBN} can find
29313 the absolute file name of a source file, will it output the fullname.
29315 @subsubheading @value{GDBN} Command
29317 The @value{GDBN} equivalent is @samp{info sources}.
29318 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29320 @subsubheading Example
29323 -file-list-exec-source-files
29325 @{file=foo.c,fullname=/home/foo.c@},
29326 @{file=/home/bar.c,fullname=/home/bar.c@},
29327 @{file=gdb_could_not_find_fullpath.c@}]
29332 @subheading The @code{-file-list-shared-libraries} Command
29333 @findex -file-list-shared-libraries
29335 @subsubheading Synopsis
29338 -file-list-shared-libraries
29341 List the shared libraries in the program.
29343 @subsubheading @value{GDBN} Command
29345 The corresponding @value{GDBN} command is @samp{info shared}.
29347 @subsubheading Example
29351 @subheading The @code{-file-list-symbol-files} Command
29352 @findex -file-list-symbol-files
29354 @subsubheading Synopsis
29357 -file-list-symbol-files
29362 @subsubheading @value{GDBN} Command
29364 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29366 @subsubheading Example
29371 @subheading The @code{-file-symbol-file} Command
29372 @findex -file-symbol-file
29374 @subsubheading Synopsis
29377 -file-symbol-file @var{file}
29380 Read symbol table info from the specified @var{file} argument. When
29381 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29382 produced, except for a completion notification.
29384 @subsubheading @value{GDBN} Command
29386 The corresponding @value{GDBN} command is @samp{symbol-file}.
29388 @subsubheading Example
29392 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29399 @node GDB/MI Memory Overlay Commands
29400 @section @sc{gdb/mi} Memory Overlay Commands
29402 The memory overlay commands are not implemented.
29404 @c @subheading -overlay-auto
29406 @c @subheading -overlay-list-mapping-state
29408 @c @subheading -overlay-list-overlays
29410 @c @subheading -overlay-map
29412 @c @subheading -overlay-off
29414 @c @subheading -overlay-on
29416 @c @subheading -overlay-unmap
29418 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29419 @node GDB/MI Signal Handling Commands
29420 @section @sc{gdb/mi} Signal Handling Commands
29422 Signal handling commands are not implemented.
29424 @c @subheading -signal-handle
29426 @c @subheading -signal-list-handle-actions
29428 @c @subheading -signal-list-signal-types
29432 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29433 @node GDB/MI Target Manipulation
29434 @section @sc{gdb/mi} Target Manipulation Commands
29437 @subheading The @code{-target-attach} Command
29438 @findex -target-attach
29440 @subsubheading Synopsis
29443 -target-attach @var{pid} | @var{gid} | @var{file}
29446 Attach to a process @var{pid} or a file @var{file} outside of
29447 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29448 group, the id previously returned by
29449 @samp{-list-thread-groups --available} must be used.
29451 @subsubheading @value{GDBN} Command
29453 The corresponding @value{GDBN} command is @samp{attach}.
29455 @subsubheading Example
29459 =thread-created,id="1"
29460 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29466 @subheading The @code{-target-compare-sections} Command
29467 @findex -target-compare-sections
29469 @subsubheading Synopsis
29472 -target-compare-sections [ @var{section} ]
29475 Compare data of section @var{section} on target to the exec file.
29476 Without the argument, all sections are compared.
29478 @subsubheading @value{GDBN} Command
29480 The @value{GDBN} equivalent is @samp{compare-sections}.
29482 @subsubheading Example
29487 @subheading The @code{-target-detach} Command
29488 @findex -target-detach
29490 @subsubheading Synopsis
29493 -target-detach [ @var{pid} | @var{gid} ]
29496 Detach from the remote target which normally resumes its execution.
29497 If either @var{pid} or @var{gid} is specified, detaches from either
29498 the specified process, or specified thread group. There's no output.
29500 @subsubheading @value{GDBN} Command
29502 The corresponding @value{GDBN} command is @samp{detach}.
29504 @subsubheading Example
29514 @subheading The @code{-target-disconnect} Command
29515 @findex -target-disconnect
29517 @subsubheading Synopsis
29523 Disconnect from the remote target. There's no output and the target is
29524 generally not resumed.
29526 @subsubheading @value{GDBN} Command
29528 The corresponding @value{GDBN} command is @samp{disconnect}.
29530 @subsubheading Example
29540 @subheading The @code{-target-download} Command
29541 @findex -target-download
29543 @subsubheading Synopsis
29549 Loads the executable onto the remote target.
29550 It prints out an update message every half second, which includes the fields:
29554 The name of the section.
29556 The size of what has been sent so far for that section.
29558 The size of the section.
29560 The total size of what was sent so far (the current and the previous sections).
29562 The size of the overall executable to download.
29566 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29567 @sc{gdb/mi} Output Syntax}).
29569 In addition, it prints the name and size of the sections, as they are
29570 downloaded. These messages include the following fields:
29574 The name of the section.
29576 The size of the section.
29578 The size of the overall executable to download.
29582 At the end, a summary is printed.
29584 @subsubheading @value{GDBN} Command
29586 The corresponding @value{GDBN} command is @samp{load}.
29588 @subsubheading Example
29590 Note: each status message appears on a single line. Here the messages
29591 have been broken down so that they can fit onto a page.
29596 +download,@{section=".text",section-size="6668",total-size="9880"@}
29597 +download,@{section=".text",section-sent="512",section-size="6668",
29598 total-sent="512",total-size="9880"@}
29599 +download,@{section=".text",section-sent="1024",section-size="6668",
29600 total-sent="1024",total-size="9880"@}
29601 +download,@{section=".text",section-sent="1536",section-size="6668",
29602 total-sent="1536",total-size="9880"@}
29603 +download,@{section=".text",section-sent="2048",section-size="6668",
29604 total-sent="2048",total-size="9880"@}
29605 +download,@{section=".text",section-sent="2560",section-size="6668",
29606 total-sent="2560",total-size="9880"@}
29607 +download,@{section=".text",section-sent="3072",section-size="6668",
29608 total-sent="3072",total-size="9880"@}
29609 +download,@{section=".text",section-sent="3584",section-size="6668",
29610 total-sent="3584",total-size="9880"@}
29611 +download,@{section=".text",section-sent="4096",section-size="6668",
29612 total-sent="4096",total-size="9880"@}
29613 +download,@{section=".text",section-sent="4608",section-size="6668",
29614 total-sent="4608",total-size="9880"@}
29615 +download,@{section=".text",section-sent="5120",section-size="6668",
29616 total-sent="5120",total-size="9880"@}
29617 +download,@{section=".text",section-sent="5632",section-size="6668",
29618 total-sent="5632",total-size="9880"@}
29619 +download,@{section=".text",section-sent="6144",section-size="6668",
29620 total-sent="6144",total-size="9880"@}
29621 +download,@{section=".text",section-sent="6656",section-size="6668",
29622 total-sent="6656",total-size="9880"@}
29623 +download,@{section=".init",section-size="28",total-size="9880"@}
29624 +download,@{section=".fini",section-size="28",total-size="9880"@}
29625 +download,@{section=".data",section-size="3156",total-size="9880"@}
29626 +download,@{section=".data",section-sent="512",section-size="3156",
29627 total-sent="7236",total-size="9880"@}
29628 +download,@{section=".data",section-sent="1024",section-size="3156",
29629 total-sent="7748",total-size="9880"@}
29630 +download,@{section=".data",section-sent="1536",section-size="3156",
29631 total-sent="8260",total-size="9880"@}
29632 +download,@{section=".data",section-sent="2048",section-size="3156",
29633 total-sent="8772",total-size="9880"@}
29634 +download,@{section=".data",section-sent="2560",section-size="3156",
29635 total-sent="9284",total-size="9880"@}
29636 +download,@{section=".data",section-sent="3072",section-size="3156",
29637 total-sent="9796",total-size="9880"@}
29638 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29645 @subheading The @code{-target-exec-status} Command
29646 @findex -target-exec-status
29648 @subsubheading Synopsis
29651 -target-exec-status
29654 Provide information on the state of the target (whether it is running or
29655 not, for instance).
29657 @subsubheading @value{GDBN} Command
29659 There's no equivalent @value{GDBN} command.
29661 @subsubheading Example
29665 @subheading The @code{-target-list-available-targets} Command
29666 @findex -target-list-available-targets
29668 @subsubheading Synopsis
29671 -target-list-available-targets
29674 List the possible targets to connect to.
29676 @subsubheading @value{GDBN} Command
29678 The corresponding @value{GDBN} command is @samp{help target}.
29680 @subsubheading Example
29684 @subheading The @code{-target-list-current-targets} Command
29685 @findex -target-list-current-targets
29687 @subsubheading Synopsis
29690 -target-list-current-targets
29693 Describe the current target.
29695 @subsubheading @value{GDBN} Command
29697 The corresponding information is printed by @samp{info file} (among
29700 @subsubheading Example
29704 @subheading The @code{-target-list-parameters} Command
29705 @findex -target-list-parameters
29707 @subsubheading Synopsis
29710 -target-list-parameters
29716 @subsubheading @value{GDBN} Command
29720 @subsubheading Example
29724 @subheading The @code{-target-select} Command
29725 @findex -target-select
29727 @subsubheading Synopsis
29730 -target-select @var{type} @var{parameters @dots{}}
29733 Connect @value{GDBN} to the remote target. This command takes two args:
29737 The type of target, for instance @samp{remote}, etc.
29738 @item @var{parameters}
29739 Device names, host names and the like. @xref{Target Commands, ,
29740 Commands for Managing Targets}, for more details.
29743 The output is a connection notification, followed by the address at
29744 which the target program is, in the following form:
29747 ^connected,addr="@var{address}",func="@var{function name}",
29748 args=[@var{arg list}]
29751 @subsubheading @value{GDBN} Command
29753 The corresponding @value{GDBN} command is @samp{target}.
29755 @subsubheading Example
29759 -target-select remote /dev/ttya
29760 ^connected,addr="0xfe00a300",func="??",args=[]
29764 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29765 @node GDB/MI File Transfer Commands
29766 @section @sc{gdb/mi} File Transfer Commands
29769 @subheading The @code{-target-file-put} Command
29770 @findex -target-file-put
29772 @subsubheading Synopsis
29775 -target-file-put @var{hostfile} @var{targetfile}
29778 Copy file @var{hostfile} from the host system (the machine running
29779 @value{GDBN}) to @var{targetfile} on the target system.
29781 @subsubheading @value{GDBN} Command
29783 The corresponding @value{GDBN} command is @samp{remote put}.
29785 @subsubheading Example
29789 -target-file-put localfile remotefile
29795 @subheading The @code{-target-file-get} Command
29796 @findex -target-file-get
29798 @subsubheading Synopsis
29801 -target-file-get @var{targetfile} @var{hostfile}
29804 Copy file @var{targetfile} from the target system to @var{hostfile}
29805 on the host system.
29807 @subsubheading @value{GDBN} Command
29809 The corresponding @value{GDBN} command is @samp{remote get}.
29811 @subsubheading Example
29815 -target-file-get remotefile localfile
29821 @subheading The @code{-target-file-delete} Command
29822 @findex -target-file-delete
29824 @subsubheading Synopsis
29827 -target-file-delete @var{targetfile}
29830 Delete @var{targetfile} from the target system.
29832 @subsubheading @value{GDBN} Command
29834 The corresponding @value{GDBN} command is @samp{remote delete}.
29836 @subsubheading Example
29840 -target-file-delete remotefile
29846 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29847 @node GDB/MI Miscellaneous Commands
29848 @section Miscellaneous @sc{gdb/mi} Commands
29850 @c @subheading -gdb-complete
29852 @subheading The @code{-gdb-exit} Command
29855 @subsubheading Synopsis
29861 Exit @value{GDBN} immediately.
29863 @subsubheading @value{GDBN} Command
29865 Approximately corresponds to @samp{quit}.
29867 @subsubheading Example
29877 @subheading The @code{-exec-abort} Command
29878 @findex -exec-abort
29880 @subsubheading Synopsis
29886 Kill the inferior running program.
29888 @subsubheading @value{GDBN} Command
29890 The corresponding @value{GDBN} command is @samp{kill}.
29892 @subsubheading Example
29897 @subheading The @code{-gdb-set} Command
29900 @subsubheading Synopsis
29906 Set an internal @value{GDBN} variable.
29907 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29909 @subsubheading @value{GDBN} Command
29911 The corresponding @value{GDBN} command is @samp{set}.
29913 @subsubheading Example
29923 @subheading The @code{-gdb-show} Command
29926 @subsubheading Synopsis
29932 Show the current value of a @value{GDBN} variable.
29934 @subsubheading @value{GDBN} Command
29936 The corresponding @value{GDBN} command is @samp{show}.
29938 @subsubheading Example
29947 @c @subheading -gdb-source
29950 @subheading The @code{-gdb-version} Command
29951 @findex -gdb-version
29953 @subsubheading Synopsis
29959 Show version information for @value{GDBN}. Used mostly in testing.
29961 @subsubheading @value{GDBN} Command
29963 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29964 default shows this information when you start an interactive session.
29966 @subsubheading Example
29968 @c This example modifies the actual output from GDB to avoid overfull
29974 ~Copyright 2000 Free Software Foundation, Inc.
29975 ~GDB is free software, covered by the GNU General Public License, and
29976 ~you are welcome to change it and/or distribute copies of it under
29977 ~ certain conditions.
29978 ~Type "show copying" to see the conditions.
29979 ~There is absolutely no warranty for GDB. Type "show warranty" for
29981 ~This GDB was configured as
29982 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29987 @subheading The @code{-list-features} Command
29988 @findex -list-features
29990 Returns a list of particular features of the MI protocol that
29991 this version of gdb implements. A feature can be a command,
29992 or a new field in an output of some command, or even an
29993 important bugfix. While a frontend can sometimes detect presence
29994 of a feature at runtime, it is easier to perform detection at debugger
29997 The command returns a list of strings, with each string naming an
29998 available feature. Each returned string is just a name, it does not
29999 have any internal structure. The list of possible feature names
30005 (gdb) -list-features
30006 ^done,result=["feature1","feature2"]
30009 The current list of features is:
30012 @item frozen-varobjs
30013 Indicates presence of the @code{-var-set-frozen} command, as well
30014 as possible presense of the @code{frozen} field in the output
30015 of @code{-varobj-create}.
30016 @item pending-breakpoints
30017 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
30019 Indicates presence of Python scripting support, Python-based
30020 pretty-printing commands, and possible presence of the
30021 @samp{display_hint} field in the output of @code{-var-list-children}
30023 Indicates presence of the @code{-thread-info} command.
30024 @item data-read-memory-bytes
30025 Indicates presense of the @code{-data-read-memory-bytes} and the
30026 @code{-data-write-memory-bytes} commands.
30030 @subheading The @code{-list-target-features} Command
30031 @findex -list-target-features
30033 Returns a list of particular features that are supported by the
30034 target. Those features affect the permitted MI commands, but
30035 unlike the features reported by the @code{-list-features} command, the
30036 features depend on which target GDB is using at the moment. Whenever
30037 a target can change, due to commands such as @code{-target-select},
30038 @code{-target-attach} or @code{-exec-run}, the list of target features
30039 may change, and the frontend should obtain it again.
30043 (gdb) -list-features
30044 ^done,result=["async"]
30047 The current list of features is:
30051 Indicates that the target is capable of asynchronous command
30052 execution, which means that @value{GDBN} will accept further commands
30053 while the target is running.
30056 Indicates that the target is capable of reverse execution.
30057 @xref{Reverse Execution}, for more information.
30061 @subheading The @code{-list-thread-groups} Command
30062 @findex -list-thread-groups
30064 @subheading Synopsis
30067 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30070 Lists thread groups (@pxref{Thread groups}). When a single thread
30071 group is passed as the argument, lists the children of that group.
30072 When several thread group are passed, lists information about those
30073 thread groups. Without any parameters, lists information about all
30074 top-level thread groups.
30076 Normally, thread groups that are being debugged are reported.
30077 With the @samp{--available} option, @value{GDBN} reports thread groups
30078 available on the target.
30080 The output of this command may have either a @samp{threads} result or
30081 a @samp{groups} result. The @samp{thread} result has a list of tuples
30082 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30083 Information}). The @samp{groups} result has a list of tuples as value,
30084 each tuple describing a thread group. If top-level groups are
30085 requested (that is, no parameter is passed), or when several groups
30086 are passed, the output always has a @samp{groups} result. The format
30087 of the @samp{group} result is described below.
30089 To reduce the number of roundtrips it's possible to list thread groups
30090 together with their children, by passing the @samp{--recurse} option
30091 and the recursion depth. Presently, only recursion depth of 1 is
30092 permitted. If this option is present, then every reported thread group
30093 will also include its children, either as @samp{group} or
30094 @samp{threads} field.
30096 In general, any combination of option and parameters is permitted, with
30097 the following caveats:
30101 When a single thread group is passed, the output will typically
30102 be the @samp{threads} result. Because threads may not contain
30103 anything, the @samp{recurse} option will be ignored.
30106 When the @samp{--available} option is passed, limited information may
30107 be available. In particular, the list of threads of a process might
30108 be inaccessible. Further, specifying specific thread groups might
30109 not give any performance advantage over listing all thread groups.
30110 The frontend should assume that @samp{-list-thread-groups --available}
30111 is always an expensive operation and cache the results.
30115 The @samp{groups} result is a list of tuples, where each tuple may
30116 have the following fields:
30120 Identifier of the thread group. This field is always present.
30121 The identifier is an opaque string; frontends should not try to
30122 convert it to an integer, even though it might look like one.
30125 The type of the thread group. At present, only @samp{process} is a
30129 The target-specific process identifier. This field is only present
30130 for thread groups of type @samp{process} and only if the process exists.
30133 The number of children this thread group has. This field may be
30134 absent for an available thread group.
30137 This field has a list of tuples as value, each tuple describing a
30138 thread. It may be present if the @samp{--recurse} option is
30139 specified, and it's actually possible to obtain the threads.
30142 This field is a list of integers, each identifying a core that one
30143 thread of the group is running on. This field may be absent if
30144 such information is not available.
30147 The name of the executable file that corresponds to this thread group.
30148 The field is only present for thread groups of type @samp{process},
30149 and only if there is a corresponding executable file.
30153 @subheading Example
30157 -list-thread-groups
30158 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30159 -list-thread-groups 17
30160 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30161 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30162 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30163 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30164 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30165 -list-thread-groups --available
30166 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30167 -list-thread-groups --available --recurse 1
30168 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30169 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30170 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30171 -list-thread-groups --available --recurse 1 17 18
30172 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30173 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30174 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30178 @subheading The @code{-add-inferior} Command
30179 @findex -add-inferior
30181 @subheading Synopsis
30187 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30188 inferior is not associated with any executable. Such association may
30189 be established with the @samp{-file-exec-and-symbols} command
30190 (@pxref{GDB/MI File Commands}). The command response has a single
30191 field, @samp{thread-group}, whose value is the identifier of the
30192 thread group corresponding to the new inferior.
30194 @subheading Example
30199 ^done,thread-group="i3"
30202 @subheading The @code{-interpreter-exec} Command
30203 @findex -interpreter-exec
30205 @subheading Synopsis
30208 -interpreter-exec @var{interpreter} @var{command}
30210 @anchor{-interpreter-exec}
30212 Execute the specified @var{command} in the given @var{interpreter}.
30214 @subheading @value{GDBN} Command
30216 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30218 @subheading Example
30222 -interpreter-exec console "break main"
30223 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30224 &"During symbol reading, bad structure-type format.\n"
30225 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30230 @subheading The @code{-inferior-tty-set} Command
30231 @findex -inferior-tty-set
30233 @subheading Synopsis
30236 -inferior-tty-set /dev/pts/1
30239 Set terminal for future runs of the program being debugged.
30241 @subheading @value{GDBN} Command
30243 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30245 @subheading Example
30249 -inferior-tty-set /dev/pts/1
30254 @subheading The @code{-inferior-tty-show} Command
30255 @findex -inferior-tty-show
30257 @subheading Synopsis
30263 Show terminal for future runs of program being debugged.
30265 @subheading @value{GDBN} Command
30267 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30269 @subheading Example
30273 -inferior-tty-set /dev/pts/1
30277 ^done,inferior_tty_terminal="/dev/pts/1"
30281 @subheading The @code{-enable-timings} Command
30282 @findex -enable-timings
30284 @subheading Synopsis
30287 -enable-timings [yes | no]
30290 Toggle the printing of the wallclock, user and system times for an MI
30291 command as a field in its output. This command is to help frontend
30292 developers optimize the performance of their code. No argument is
30293 equivalent to @samp{yes}.
30295 @subheading @value{GDBN} Command
30299 @subheading Example
30307 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30308 addr="0x080484ed",func="main",file="myprog.c",
30309 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30310 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30318 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30319 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30320 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30321 fullname="/home/nickrob/myprog.c",line="73"@}
30326 @chapter @value{GDBN} Annotations
30328 This chapter describes annotations in @value{GDBN}. Annotations were
30329 designed to interface @value{GDBN} to graphical user interfaces or other
30330 similar programs which want to interact with @value{GDBN} at a
30331 relatively high level.
30333 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30337 This is Edition @value{EDITION}, @value{DATE}.
30341 * Annotations Overview:: What annotations are; the general syntax.
30342 * Server Prefix:: Issuing a command without affecting user state.
30343 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30344 * Errors:: Annotations for error messages.
30345 * Invalidation:: Some annotations describe things now invalid.
30346 * Annotations for Running::
30347 Whether the program is running, how it stopped, etc.
30348 * Source Annotations:: Annotations describing source code.
30351 @node Annotations Overview
30352 @section What is an Annotation?
30353 @cindex annotations
30355 Annotations start with a newline character, two @samp{control-z}
30356 characters, and the name of the annotation. If there is no additional
30357 information associated with this annotation, the name of the annotation
30358 is followed immediately by a newline. If there is additional
30359 information, the name of the annotation is followed by a space, the
30360 additional information, and a newline. The additional information
30361 cannot contain newline characters.
30363 Any output not beginning with a newline and two @samp{control-z}
30364 characters denotes literal output from @value{GDBN}. Currently there is
30365 no need for @value{GDBN} to output a newline followed by two
30366 @samp{control-z} characters, but if there was such a need, the
30367 annotations could be extended with an @samp{escape} annotation which
30368 means those three characters as output.
30370 The annotation @var{level}, which is specified using the
30371 @option{--annotate} command line option (@pxref{Mode Options}), controls
30372 how much information @value{GDBN} prints together with its prompt,
30373 values of expressions, source lines, and other types of output. Level 0
30374 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30375 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30376 for programs that control @value{GDBN}, and level 2 annotations have
30377 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30378 Interface, annotate, GDB's Obsolete Annotations}).
30381 @kindex set annotate
30382 @item set annotate @var{level}
30383 The @value{GDBN} command @code{set annotate} sets the level of
30384 annotations to the specified @var{level}.
30386 @item show annotate
30387 @kindex show annotate
30388 Show the current annotation level.
30391 This chapter describes level 3 annotations.
30393 A simple example of starting up @value{GDBN} with annotations is:
30396 $ @kbd{gdb --annotate=3}
30398 Copyright 2003 Free Software Foundation, Inc.
30399 GDB is free software, covered by the GNU General Public License,
30400 and you are welcome to change it and/or distribute copies of it
30401 under certain conditions.
30402 Type "show copying" to see the conditions.
30403 There is absolutely no warranty for GDB. Type "show warranty"
30405 This GDB was configured as "i386-pc-linux-gnu"
30416 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30417 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30418 denotes a @samp{control-z} character) are annotations; the rest is
30419 output from @value{GDBN}.
30421 @node Server Prefix
30422 @section The Server Prefix
30423 @cindex server prefix
30425 If you prefix a command with @samp{server } then it will not affect
30426 the command history, nor will it affect @value{GDBN}'s notion of which
30427 command to repeat if @key{RET} is pressed on a line by itself. This
30428 means that commands can be run behind a user's back by a front-end in
30429 a transparent manner.
30431 The @code{server } prefix does not affect the recording of values into
30432 the value history; to print a value without recording it into the
30433 value history, use the @code{output} command instead of the
30434 @code{print} command.
30436 Using this prefix also disables confirmation requests
30437 (@pxref{confirmation requests}).
30440 @section Annotation for @value{GDBN} Input
30442 @cindex annotations for prompts
30443 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30444 to know when to send output, when the output from a given command is
30447 Different kinds of input each have a different @dfn{input type}. Each
30448 input type has three annotations: a @code{pre-} annotation, which
30449 denotes the beginning of any prompt which is being output, a plain
30450 annotation, which denotes the end of the prompt, and then a @code{post-}
30451 annotation which denotes the end of any echo which may (or may not) be
30452 associated with the input. For example, the @code{prompt} input type
30453 features the following annotations:
30461 The input types are
30464 @findex pre-prompt annotation
30465 @findex prompt annotation
30466 @findex post-prompt annotation
30468 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30470 @findex pre-commands annotation
30471 @findex commands annotation
30472 @findex post-commands annotation
30474 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30475 command. The annotations are repeated for each command which is input.
30477 @findex pre-overload-choice annotation
30478 @findex overload-choice annotation
30479 @findex post-overload-choice annotation
30480 @item overload-choice
30481 When @value{GDBN} wants the user to select between various overloaded functions.
30483 @findex pre-query annotation
30484 @findex query annotation
30485 @findex post-query annotation
30487 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30489 @findex pre-prompt-for-continue annotation
30490 @findex prompt-for-continue annotation
30491 @findex post-prompt-for-continue annotation
30492 @item prompt-for-continue
30493 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30494 expect this to work well; instead use @code{set height 0} to disable
30495 prompting. This is because the counting of lines is buggy in the
30496 presence of annotations.
30501 @cindex annotations for errors, warnings and interrupts
30503 @findex quit annotation
30508 This annotation occurs right before @value{GDBN} responds to an interrupt.
30510 @findex error annotation
30515 This annotation occurs right before @value{GDBN} responds to an error.
30517 Quit and error annotations indicate that any annotations which @value{GDBN} was
30518 in the middle of may end abruptly. For example, if a
30519 @code{value-history-begin} annotation is followed by a @code{error}, one
30520 cannot expect to receive the matching @code{value-history-end}. One
30521 cannot expect not to receive it either, however; an error annotation
30522 does not necessarily mean that @value{GDBN} is immediately returning all the way
30525 @findex error-begin annotation
30526 A quit or error annotation may be preceded by
30532 Any output between that and the quit or error annotation is the error
30535 Warning messages are not yet annotated.
30536 @c If we want to change that, need to fix warning(), type_error(),
30537 @c range_error(), and possibly other places.
30540 @section Invalidation Notices
30542 @cindex annotations for invalidation messages
30543 The following annotations say that certain pieces of state may have
30547 @findex frames-invalid annotation
30548 @item ^Z^Zframes-invalid
30550 The frames (for example, output from the @code{backtrace} command) may
30553 @findex breakpoints-invalid annotation
30554 @item ^Z^Zbreakpoints-invalid
30556 The breakpoints may have changed. For example, the user just added or
30557 deleted a breakpoint.
30560 @node Annotations for Running
30561 @section Running the Program
30562 @cindex annotations for running programs
30564 @findex starting annotation
30565 @findex stopping annotation
30566 When the program starts executing due to a @value{GDBN} command such as
30567 @code{step} or @code{continue},
30573 is output. When the program stops,
30579 is output. Before the @code{stopped} annotation, a variety of
30580 annotations describe how the program stopped.
30583 @findex exited annotation
30584 @item ^Z^Zexited @var{exit-status}
30585 The program exited, and @var{exit-status} is the exit status (zero for
30586 successful exit, otherwise nonzero).
30588 @findex signalled annotation
30589 @findex signal-name annotation
30590 @findex signal-name-end annotation
30591 @findex signal-string annotation
30592 @findex signal-string-end annotation
30593 @item ^Z^Zsignalled
30594 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30595 annotation continues:
30601 ^Z^Zsignal-name-end
30605 ^Z^Zsignal-string-end
30610 where @var{name} is the name of the signal, such as @code{SIGILL} or
30611 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30612 as @code{Illegal Instruction} or @code{Segmentation fault}.
30613 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30614 user's benefit and have no particular format.
30616 @findex signal annotation
30618 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30619 just saying that the program received the signal, not that it was
30620 terminated with it.
30622 @findex breakpoint annotation
30623 @item ^Z^Zbreakpoint @var{number}
30624 The program hit breakpoint number @var{number}.
30626 @findex watchpoint annotation
30627 @item ^Z^Zwatchpoint @var{number}
30628 The program hit watchpoint number @var{number}.
30631 @node Source Annotations
30632 @section Displaying Source
30633 @cindex annotations for source display
30635 @findex source annotation
30636 The following annotation is used instead of displaying source code:
30639 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30642 where @var{filename} is an absolute file name indicating which source
30643 file, @var{line} is the line number within that file (where 1 is the
30644 first line in the file), @var{character} is the character position
30645 within the file (where 0 is the first character in the file) (for most
30646 debug formats this will necessarily point to the beginning of a line),
30647 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30648 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30649 @var{addr} is the address in the target program associated with the
30650 source which is being displayed. @var{addr} is in the form @samp{0x}
30651 followed by one or more lowercase hex digits (note that this does not
30652 depend on the language).
30654 @node JIT Interface
30655 @chapter JIT Compilation Interface
30656 @cindex just-in-time compilation
30657 @cindex JIT compilation interface
30659 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30660 interface. A JIT compiler is a program or library that generates native
30661 executable code at runtime and executes it, usually in order to achieve good
30662 performance while maintaining platform independence.
30664 Programs that use JIT compilation are normally difficult to debug because
30665 portions of their code are generated at runtime, instead of being loaded from
30666 object files, which is where @value{GDBN} normally finds the program's symbols
30667 and debug information. In order to debug programs that use JIT compilation,
30668 @value{GDBN} has an interface that allows the program to register in-memory
30669 symbol files with @value{GDBN} at runtime.
30671 If you are using @value{GDBN} to debug a program that uses this interface, then
30672 it should work transparently so long as you have not stripped the binary. If
30673 you are developing a JIT compiler, then the interface is documented in the rest
30674 of this chapter. At this time, the only known client of this interface is the
30677 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30678 JIT compiler communicates with @value{GDBN} by writing data into a global
30679 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30680 attaches, it reads a linked list of symbol files from the global variable to
30681 find existing code, and puts a breakpoint in the function so that it can find
30682 out about additional code.
30685 * Declarations:: Relevant C struct declarations
30686 * Registering Code:: Steps to register code
30687 * Unregistering Code:: Steps to unregister code
30691 @section JIT Declarations
30693 These are the relevant struct declarations that a C program should include to
30694 implement the interface:
30704 struct jit_code_entry
30706 struct jit_code_entry *next_entry;
30707 struct jit_code_entry *prev_entry;
30708 const char *symfile_addr;
30709 uint64_t symfile_size;
30712 struct jit_descriptor
30715 /* This type should be jit_actions_t, but we use uint32_t
30716 to be explicit about the bitwidth. */
30717 uint32_t action_flag;
30718 struct jit_code_entry *relevant_entry;
30719 struct jit_code_entry *first_entry;
30722 /* GDB puts a breakpoint in this function. */
30723 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30725 /* Make sure to specify the version statically, because the
30726 debugger may check the version before we can set it. */
30727 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30730 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30731 modifications to this global data properly, which can easily be done by putting
30732 a global mutex around modifications to these structures.
30734 @node Registering Code
30735 @section Registering Code
30737 To register code with @value{GDBN}, the JIT should follow this protocol:
30741 Generate an object file in memory with symbols and other desired debug
30742 information. The file must include the virtual addresses of the sections.
30745 Create a code entry for the file, which gives the start and size of the symbol
30749 Add it to the linked list in the JIT descriptor.
30752 Point the relevant_entry field of the descriptor at the entry.
30755 Set @code{action_flag} to @code{JIT_REGISTER} and call
30756 @code{__jit_debug_register_code}.
30759 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30760 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30761 new code. However, the linked list must still be maintained in order to allow
30762 @value{GDBN} to attach to a running process and still find the symbol files.
30764 @node Unregistering Code
30765 @section Unregistering Code
30767 If code is freed, then the JIT should use the following protocol:
30771 Remove the code entry corresponding to the code from the linked list.
30774 Point the @code{relevant_entry} field of the descriptor at the code entry.
30777 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30778 @code{__jit_debug_register_code}.
30781 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30782 and the JIT will leak the memory used for the associated symbol files.
30785 @chapter Reporting Bugs in @value{GDBN}
30786 @cindex bugs in @value{GDBN}
30787 @cindex reporting bugs in @value{GDBN}
30789 Your bug reports play an essential role in making @value{GDBN} reliable.
30791 Reporting a bug may help you by bringing a solution to your problem, or it
30792 may not. But in any case the principal function of a bug report is to help
30793 the entire community by making the next version of @value{GDBN} work better. Bug
30794 reports are your contribution to the maintenance of @value{GDBN}.
30796 In order for a bug report to serve its purpose, you must include the
30797 information that enables us to fix the bug.
30800 * Bug Criteria:: Have you found a bug?
30801 * Bug Reporting:: How to report bugs
30805 @section Have You Found a Bug?
30806 @cindex bug criteria
30808 If you are not sure whether you have found a bug, here are some guidelines:
30811 @cindex fatal signal
30812 @cindex debugger crash
30813 @cindex crash of debugger
30815 If the debugger gets a fatal signal, for any input whatever, that is a
30816 @value{GDBN} bug. Reliable debuggers never crash.
30818 @cindex error on valid input
30820 If @value{GDBN} produces an error message for valid input, that is a
30821 bug. (Note that if you're cross debugging, the problem may also be
30822 somewhere in the connection to the target.)
30824 @cindex invalid input
30826 If @value{GDBN} does not produce an error message for invalid input,
30827 that is a bug. However, you should note that your idea of
30828 ``invalid input'' might be our idea of ``an extension'' or ``support
30829 for traditional practice''.
30832 If you are an experienced user of debugging tools, your suggestions
30833 for improvement of @value{GDBN} are welcome in any case.
30836 @node Bug Reporting
30837 @section How to Report Bugs
30838 @cindex bug reports
30839 @cindex @value{GDBN} bugs, reporting
30841 A number of companies and individuals offer support for @sc{gnu} products.
30842 If you obtained @value{GDBN} from a support organization, we recommend you
30843 contact that organization first.
30845 You can find contact information for many support companies and
30846 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30848 @c should add a web page ref...
30851 @ifset BUGURL_DEFAULT
30852 In any event, we also recommend that you submit bug reports for
30853 @value{GDBN}. The preferred method is to submit them directly using
30854 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30855 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30858 @strong{Do not send bug reports to @samp{info-gdb}, or to
30859 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30860 not want to receive bug reports. Those that do have arranged to receive
30863 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30864 serves as a repeater. The mailing list and the newsgroup carry exactly
30865 the same messages. Often people think of posting bug reports to the
30866 newsgroup instead of mailing them. This appears to work, but it has one
30867 problem which can be crucial: a newsgroup posting often lacks a mail
30868 path back to the sender. Thus, if we need to ask for more information,
30869 we may be unable to reach you. For this reason, it is better to send
30870 bug reports to the mailing list.
30872 @ifclear BUGURL_DEFAULT
30873 In any event, we also recommend that you submit bug reports for
30874 @value{GDBN} to @value{BUGURL}.
30878 The fundamental principle of reporting bugs usefully is this:
30879 @strong{report all the facts}. If you are not sure whether to state a
30880 fact or leave it out, state it!
30882 Often people omit facts because they think they know what causes the
30883 problem and assume that some details do not matter. Thus, you might
30884 assume that the name of the variable you use in an example does not matter.
30885 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30886 stray memory reference which happens to fetch from the location where that
30887 name is stored in memory; perhaps, if the name were different, the contents
30888 of that location would fool the debugger into doing the right thing despite
30889 the bug. Play it safe and give a specific, complete example. That is the
30890 easiest thing for you to do, and the most helpful.
30892 Keep in mind that the purpose of a bug report is to enable us to fix the
30893 bug. It may be that the bug has been reported previously, but neither
30894 you nor we can know that unless your bug report is complete and
30897 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30898 bell?'' Those bug reports are useless, and we urge everyone to
30899 @emph{refuse to respond to them} except to chide the sender to report
30902 To enable us to fix the bug, you should include all these things:
30906 The version of @value{GDBN}. @value{GDBN} announces it if you start
30907 with no arguments; you can also print it at any time using @code{show
30910 Without this, we will not know whether there is any point in looking for
30911 the bug in the current version of @value{GDBN}.
30914 The type of machine you are using, and the operating system name and
30918 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30919 ``@value{GCC}--2.8.1''.
30922 What compiler (and its version) was used to compile the program you are
30923 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30924 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30925 to get this information; for other compilers, see the documentation for
30929 The command arguments you gave the compiler to compile your example and
30930 observe the bug. For example, did you use @samp{-O}? To guarantee
30931 you will not omit something important, list them all. A copy of the
30932 Makefile (or the output from make) is sufficient.
30934 If we were to try to guess the arguments, we would probably guess wrong
30935 and then we might not encounter the bug.
30938 A complete input script, and all necessary source files, that will
30942 A description of what behavior you observe that you believe is
30943 incorrect. For example, ``It gets a fatal signal.''
30945 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30946 will certainly notice it. But if the bug is incorrect output, we might
30947 not notice unless it is glaringly wrong. You might as well not give us
30948 a chance to make a mistake.
30950 Even if the problem you experience is a fatal signal, you should still
30951 say so explicitly. Suppose something strange is going on, such as, your
30952 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30953 the C library on your system. (This has happened!) Your copy might
30954 crash and ours would not. If you told us to expect a crash, then when
30955 ours fails to crash, we would know that the bug was not happening for
30956 us. If you had not told us to expect a crash, then we would not be able
30957 to draw any conclusion from our observations.
30960 @cindex recording a session script
30961 To collect all this information, you can use a session recording program
30962 such as @command{script}, which is available on many Unix systems.
30963 Just run your @value{GDBN} session inside @command{script} and then
30964 include the @file{typescript} file with your bug report.
30966 Another way to record a @value{GDBN} session is to run @value{GDBN}
30967 inside Emacs and then save the entire buffer to a file.
30970 If you wish to suggest changes to the @value{GDBN} source, send us context
30971 diffs. If you even discuss something in the @value{GDBN} source, refer to
30972 it by context, not by line number.
30974 The line numbers in our development sources will not match those in your
30975 sources. Your line numbers would convey no useful information to us.
30979 Here are some things that are not necessary:
30983 A description of the envelope of the bug.
30985 Often people who encounter a bug spend a lot of time investigating
30986 which changes to the input file will make the bug go away and which
30987 changes will not affect it.
30989 This is often time consuming and not very useful, because the way we
30990 will find the bug is by running a single example under the debugger
30991 with breakpoints, not by pure deduction from a series of examples.
30992 We recommend that you save your time for something else.
30994 Of course, if you can find a simpler example to report @emph{instead}
30995 of the original one, that is a convenience for us. Errors in the
30996 output will be easier to spot, running under the debugger will take
30997 less time, and so on.
30999 However, simplification is not vital; if you do not want to do this,
31000 report the bug anyway and send us the entire test case you used.
31003 A patch for the bug.
31005 A patch for the bug does help us if it is a good one. But do not omit
31006 the necessary information, such as the test case, on the assumption that
31007 a patch is all we need. We might see problems with your patch and decide
31008 to fix the problem another way, or we might not understand it at all.
31010 Sometimes with a program as complicated as @value{GDBN} it is very hard to
31011 construct an example that will make the program follow a certain path
31012 through the code. If you do not send us the example, we will not be able
31013 to construct one, so we will not be able to verify that the bug is fixed.
31015 And if we cannot understand what bug you are trying to fix, or why your
31016 patch should be an improvement, we will not install it. A test case will
31017 help us to understand.
31020 A guess about what the bug is or what it depends on.
31022 Such guesses are usually wrong. Even we cannot guess right about such
31023 things without first using the debugger to find the facts.
31026 @c The readline documentation is distributed with the readline code
31027 @c and consists of the two following files:
31029 @c inc-hist.texinfo
31030 @c Use -I with makeinfo to point to the appropriate directory,
31031 @c environment var TEXINPUTS with TeX.
31032 @ifclear SYSTEM_READLINE
31033 @include rluser.texi
31034 @include inc-hist.texinfo
31038 @appendix In Memoriam
31040 The @value{GDBN} project mourns the loss of the following long-time
31045 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
31046 to Free Software in general. Outside of @value{GDBN}, he was known in
31047 the Amiga world for his series of Fish Disks, and the GeekGadget project.
31049 @item Michael Snyder
31050 Michael was one of the Global Maintainers of the @value{GDBN} project,
31051 with contributions recorded as early as 1996, until 2011. In addition
31052 to his day to day participation, he was a large driving force behind
31053 adding Reverse Debugging to @value{GDBN}.
31056 Beyond their technical contributions to the project, they were also
31057 enjoyable members of the Free Software Community. We will miss them.
31059 @node Formatting Documentation
31060 @appendix Formatting Documentation
31062 @cindex @value{GDBN} reference card
31063 @cindex reference card
31064 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31065 for printing with PostScript or Ghostscript, in the @file{gdb}
31066 subdirectory of the main source directory@footnote{In
31067 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31068 release.}. If you can use PostScript or Ghostscript with your printer,
31069 you can print the reference card immediately with @file{refcard.ps}.
31071 The release also includes the source for the reference card. You
31072 can format it, using @TeX{}, by typing:
31078 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31079 mode on US ``letter'' size paper;
31080 that is, on a sheet 11 inches wide by 8.5 inches
31081 high. You will need to specify this form of printing as an option to
31082 your @sc{dvi} output program.
31084 @cindex documentation
31086 All the documentation for @value{GDBN} comes as part of the machine-readable
31087 distribution. The documentation is written in Texinfo format, which is
31088 a documentation system that uses a single source file to produce both
31089 on-line information and a printed manual. You can use one of the Info
31090 formatting commands to create the on-line version of the documentation
31091 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31093 @value{GDBN} includes an already formatted copy of the on-line Info
31094 version of this manual in the @file{gdb} subdirectory. The main Info
31095 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31096 subordinate files matching @samp{gdb.info*} in the same directory. If
31097 necessary, you can print out these files, or read them with any editor;
31098 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31099 Emacs or the standalone @code{info} program, available as part of the
31100 @sc{gnu} Texinfo distribution.
31102 If you want to format these Info files yourself, you need one of the
31103 Info formatting programs, such as @code{texinfo-format-buffer} or
31106 If you have @code{makeinfo} installed, and are in the top level
31107 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31108 version @value{GDBVN}), you can make the Info file by typing:
31115 If you want to typeset and print copies of this manual, you need @TeX{},
31116 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31117 Texinfo definitions file.
31119 @TeX{} is a typesetting program; it does not print files directly, but
31120 produces output files called @sc{dvi} files. To print a typeset
31121 document, you need a program to print @sc{dvi} files. If your system
31122 has @TeX{} installed, chances are it has such a program. The precise
31123 command to use depends on your system; @kbd{lpr -d} is common; another
31124 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31125 require a file name without any extension or a @samp{.dvi} extension.
31127 @TeX{} also requires a macro definitions file called
31128 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31129 written in Texinfo format. On its own, @TeX{} cannot either read or
31130 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31131 and is located in the @file{gdb-@var{version-number}/texinfo}
31134 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31135 typeset and print this manual. First switch to the @file{gdb}
31136 subdirectory of the main source directory (for example, to
31137 @file{gdb-@value{GDBVN}/gdb}) and type:
31143 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31145 @node Installing GDB
31146 @appendix Installing @value{GDBN}
31147 @cindex installation
31150 * Requirements:: Requirements for building @value{GDBN}
31151 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31152 * Separate Objdir:: Compiling @value{GDBN} in another directory
31153 * Config Names:: Specifying names for hosts and targets
31154 * Configure Options:: Summary of options for configure
31155 * System-wide configuration:: Having a system-wide init file
31159 @section Requirements for Building @value{GDBN}
31160 @cindex building @value{GDBN}, requirements for
31162 Building @value{GDBN} requires various tools and packages to be available.
31163 Other packages will be used only if they are found.
31165 @heading Tools/Packages Necessary for Building @value{GDBN}
31167 @item ISO C90 compiler
31168 @value{GDBN} is written in ISO C90. It should be buildable with any
31169 working C90 compiler, e.g.@: GCC.
31173 @heading Tools/Packages Optional for Building @value{GDBN}
31177 @value{GDBN} can use the Expat XML parsing library. This library may be
31178 included with your operating system distribution; if it is not, you
31179 can get the latest version from @url{http://expat.sourceforge.net}.
31180 The @file{configure} script will search for this library in several
31181 standard locations; if it is installed in an unusual path, you can
31182 use the @option{--with-libexpat-prefix} option to specify its location.
31188 Remote protocol memory maps (@pxref{Memory Map Format})
31190 Target descriptions (@pxref{Target Descriptions})
31192 Remote shared library lists (@pxref{Library List Format})
31194 MS-Windows shared libraries (@pxref{Shared Libraries})
31196 Traceframe info (@pxref{Traceframe Info Format})
31200 @cindex compressed debug sections
31201 @value{GDBN} will use the @samp{zlib} library, if available, to read
31202 compressed debug sections. Some linkers, such as GNU gold, are capable
31203 of producing binaries with compressed debug sections. If @value{GDBN}
31204 is compiled with @samp{zlib}, it will be able to read the debug
31205 information in such binaries.
31207 The @samp{zlib} library is likely included with your operating system
31208 distribution; if it is not, you can get the latest version from
31209 @url{http://zlib.net}.
31212 @value{GDBN}'s features related to character sets (@pxref{Character
31213 Sets}) require a functioning @code{iconv} implementation. If you are
31214 on a GNU system, then this is provided by the GNU C Library. Some
31215 other systems also provide a working @code{iconv}.
31217 On systems with @code{iconv}, you can install GNU Libiconv. If you
31218 have previously installed Libiconv, you can use the
31219 @option{--with-libiconv-prefix} option to configure.
31221 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31222 arrange to build Libiconv if a directory named @file{libiconv} appears
31223 in the top-most source directory. If Libiconv is built this way, and
31224 if the operating system does not provide a suitable @code{iconv}
31225 implementation, then the just-built library will automatically be used
31226 by @value{GDBN}. One easy way to set this up is to download GNU
31227 Libiconv, unpack it, and then rename the directory holding the
31228 Libiconv source code to @samp{libiconv}.
31231 @node Running Configure
31232 @section Invoking the @value{GDBN} @file{configure} Script
31233 @cindex configuring @value{GDBN}
31234 @value{GDBN} comes with a @file{configure} script that automates the process
31235 of preparing @value{GDBN} for installation; you can then use @code{make} to
31236 build the @code{gdb} program.
31238 @c irrelevant in info file; it's as current as the code it lives with.
31239 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31240 look at the @file{README} file in the sources; we may have improved the
31241 installation procedures since publishing this manual.}
31244 The @value{GDBN} distribution includes all the source code you need for
31245 @value{GDBN} in a single directory, whose name is usually composed by
31246 appending the version number to @samp{gdb}.
31248 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31249 @file{gdb-@value{GDBVN}} directory. That directory contains:
31252 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31253 script for configuring @value{GDBN} and all its supporting libraries
31255 @item gdb-@value{GDBVN}/gdb
31256 the source specific to @value{GDBN} itself
31258 @item gdb-@value{GDBVN}/bfd
31259 source for the Binary File Descriptor library
31261 @item gdb-@value{GDBVN}/include
31262 @sc{gnu} include files
31264 @item gdb-@value{GDBVN}/libiberty
31265 source for the @samp{-liberty} free software library
31267 @item gdb-@value{GDBVN}/opcodes
31268 source for the library of opcode tables and disassemblers
31270 @item gdb-@value{GDBVN}/readline
31271 source for the @sc{gnu} command-line interface
31273 @item gdb-@value{GDBVN}/glob
31274 source for the @sc{gnu} filename pattern-matching subroutine
31276 @item gdb-@value{GDBVN}/mmalloc
31277 source for the @sc{gnu} memory-mapped malloc package
31280 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31281 from the @file{gdb-@var{version-number}} source directory, which in
31282 this example is the @file{gdb-@value{GDBVN}} directory.
31284 First switch to the @file{gdb-@var{version-number}} source directory
31285 if you are not already in it; then run @file{configure}. Pass the
31286 identifier for the platform on which @value{GDBN} will run as an
31292 cd gdb-@value{GDBVN}
31293 ./configure @var{host}
31298 where @var{host} is an identifier such as @samp{sun4} or
31299 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31300 (You can often leave off @var{host}; @file{configure} tries to guess the
31301 correct value by examining your system.)
31303 Running @samp{configure @var{host}} and then running @code{make} builds the
31304 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31305 libraries, then @code{gdb} itself. The configured source files, and the
31306 binaries, are left in the corresponding source directories.
31309 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31310 system does not recognize this automatically when you run a different
31311 shell, you may need to run @code{sh} on it explicitly:
31314 sh configure @var{host}
31317 If you run @file{configure} from a directory that contains source
31318 directories for multiple libraries or programs, such as the
31319 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31321 creates configuration files for every directory level underneath (unless
31322 you tell it not to, with the @samp{--norecursion} option).
31324 You should run the @file{configure} script from the top directory in the
31325 source tree, the @file{gdb-@var{version-number}} directory. If you run
31326 @file{configure} from one of the subdirectories, you will configure only
31327 that subdirectory. That is usually not what you want. In particular,
31328 if you run the first @file{configure} from the @file{gdb} subdirectory
31329 of the @file{gdb-@var{version-number}} directory, you will omit the
31330 configuration of @file{bfd}, @file{readline}, and other sibling
31331 directories of the @file{gdb} subdirectory. This leads to build errors
31332 about missing include files such as @file{bfd/bfd.h}.
31334 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31335 However, you should make sure that the shell on your path (named by
31336 the @samp{SHELL} environment variable) is publicly readable. Remember
31337 that @value{GDBN} uses the shell to start your program---some systems refuse to
31338 let @value{GDBN} debug child processes whose programs are not readable.
31340 @node Separate Objdir
31341 @section Compiling @value{GDBN} in Another Directory
31343 If you want to run @value{GDBN} versions for several host or target machines,
31344 you need a different @code{gdb} compiled for each combination of
31345 host and target. @file{configure} is designed to make this easy by
31346 allowing you to generate each configuration in a separate subdirectory,
31347 rather than in the source directory. If your @code{make} program
31348 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31349 @code{make} in each of these directories builds the @code{gdb}
31350 program specified there.
31352 To build @code{gdb} in a separate directory, run @file{configure}
31353 with the @samp{--srcdir} option to specify where to find the source.
31354 (You also need to specify a path to find @file{configure}
31355 itself from your working directory. If the path to @file{configure}
31356 would be the same as the argument to @samp{--srcdir}, you can leave out
31357 the @samp{--srcdir} option; it is assumed.)
31359 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31360 separate directory for a Sun 4 like this:
31364 cd gdb-@value{GDBVN}
31367 ../gdb-@value{GDBVN}/configure sun4
31372 When @file{configure} builds a configuration using a remote source
31373 directory, it creates a tree for the binaries with the same structure
31374 (and using the same names) as the tree under the source directory. In
31375 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31376 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31377 @file{gdb-sun4/gdb}.
31379 Make sure that your path to the @file{configure} script has just one
31380 instance of @file{gdb} in it. If your path to @file{configure} looks
31381 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31382 one subdirectory of @value{GDBN}, not the whole package. This leads to
31383 build errors about missing include files such as @file{bfd/bfd.h}.
31385 One popular reason to build several @value{GDBN} configurations in separate
31386 directories is to configure @value{GDBN} for cross-compiling (where
31387 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31388 programs that run on another machine---the @dfn{target}).
31389 You specify a cross-debugging target by
31390 giving the @samp{--target=@var{target}} option to @file{configure}.
31392 When you run @code{make} to build a program or library, you must run
31393 it in a configured directory---whatever directory you were in when you
31394 called @file{configure} (or one of its subdirectories).
31396 The @code{Makefile} that @file{configure} generates in each source
31397 directory also runs recursively. If you type @code{make} in a source
31398 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31399 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31400 will build all the required libraries, and then build GDB.
31402 When you have multiple hosts or targets configured in separate
31403 directories, you can run @code{make} on them in parallel (for example,
31404 if they are NFS-mounted on each of the hosts); they will not interfere
31408 @section Specifying Names for Hosts and Targets
31410 The specifications used for hosts and targets in the @file{configure}
31411 script are based on a three-part naming scheme, but some short predefined
31412 aliases are also supported. The full naming scheme encodes three pieces
31413 of information in the following pattern:
31416 @var{architecture}-@var{vendor}-@var{os}
31419 For example, you can use the alias @code{sun4} as a @var{host} argument,
31420 or as the value for @var{target} in a @code{--target=@var{target}}
31421 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31423 The @file{configure} script accompanying @value{GDBN} does not provide
31424 any query facility to list all supported host and target names or
31425 aliases. @file{configure} calls the Bourne shell script
31426 @code{config.sub} to map abbreviations to full names; you can read the
31427 script, if you wish, or you can use it to test your guesses on
31428 abbreviations---for example:
31431 % sh config.sub i386-linux
31433 % sh config.sub alpha-linux
31434 alpha-unknown-linux-gnu
31435 % sh config.sub hp9k700
31437 % sh config.sub sun4
31438 sparc-sun-sunos4.1.1
31439 % sh config.sub sun3
31440 m68k-sun-sunos4.1.1
31441 % sh config.sub i986v
31442 Invalid configuration `i986v': machine `i986v' not recognized
31446 @code{config.sub} is also distributed in the @value{GDBN} source
31447 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31449 @node Configure Options
31450 @section @file{configure} Options
31452 Here is a summary of the @file{configure} options and arguments that
31453 are most often useful for building @value{GDBN}. @file{configure} also has
31454 several other options not listed here. @inforef{What Configure
31455 Does,,configure.info}, for a full explanation of @file{configure}.
31458 configure @r{[}--help@r{]}
31459 @r{[}--prefix=@var{dir}@r{]}
31460 @r{[}--exec-prefix=@var{dir}@r{]}
31461 @r{[}--srcdir=@var{dirname}@r{]}
31462 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31463 @r{[}--target=@var{target}@r{]}
31468 You may introduce options with a single @samp{-} rather than
31469 @samp{--} if you prefer; but you may abbreviate option names if you use
31474 Display a quick summary of how to invoke @file{configure}.
31476 @item --prefix=@var{dir}
31477 Configure the source to install programs and files under directory
31480 @item --exec-prefix=@var{dir}
31481 Configure the source to install programs under directory
31484 @c avoid splitting the warning from the explanation:
31486 @item --srcdir=@var{dirname}
31487 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31488 @code{make} that implements the @code{VPATH} feature.}@*
31489 Use this option to make configurations in directories separate from the
31490 @value{GDBN} source directories. Among other things, you can use this to
31491 build (or maintain) several configurations simultaneously, in separate
31492 directories. @file{configure} writes configuration-specific files in
31493 the current directory, but arranges for them to use the source in the
31494 directory @var{dirname}. @file{configure} creates directories under
31495 the working directory in parallel to the source directories below
31498 @item --norecursion
31499 Configure only the directory level where @file{configure} is executed; do not
31500 propagate configuration to subdirectories.
31502 @item --target=@var{target}
31503 Configure @value{GDBN} for cross-debugging programs running on the specified
31504 @var{target}. Without this option, @value{GDBN} is configured to debug
31505 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31507 There is no convenient way to generate a list of all available targets.
31509 @item @var{host} @dots{}
31510 Configure @value{GDBN} to run on the specified @var{host}.
31512 There is no convenient way to generate a list of all available hosts.
31515 There are many other options available as well, but they are generally
31516 needed for special purposes only.
31518 @node System-wide configuration
31519 @section System-wide configuration and settings
31520 @cindex system-wide init file
31522 @value{GDBN} can be configured to have a system-wide init file;
31523 this file will be read and executed at startup (@pxref{Startup, , What
31524 @value{GDBN} does during startup}).
31526 Here is the corresponding configure option:
31529 @item --with-system-gdbinit=@var{file}
31530 Specify that the default location of the system-wide init file is
31534 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31535 it may be subject to relocation. Two possible cases:
31539 If the default location of this init file contains @file{$prefix},
31540 it will be subject to relocation. Suppose that the configure options
31541 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31542 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31543 init file is looked for as @file{$install/etc/gdbinit} instead of
31544 @file{$prefix/etc/gdbinit}.
31547 By contrast, if the default location does not contain the prefix,
31548 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31549 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31550 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31551 wherever @value{GDBN} is installed.
31554 @node Maintenance Commands
31555 @appendix Maintenance Commands
31556 @cindex maintenance commands
31557 @cindex internal commands
31559 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31560 includes a number of commands intended for @value{GDBN} developers,
31561 that are not documented elsewhere in this manual. These commands are
31562 provided here for reference. (For commands that turn on debugging
31563 messages, see @ref{Debugging Output}.)
31566 @kindex maint agent
31567 @kindex maint agent-eval
31568 @item maint agent @var{expression}
31569 @itemx maint agent-eval @var{expression}
31570 Translate the given @var{expression} into remote agent bytecodes.
31571 This command is useful for debugging the Agent Expression mechanism
31572 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31573 expression useful for data collection, such as by tracepoints, while
31574 @samp{maint agent-eval} produces an expression that evaluates directly
31575 to a result. For instance, a collection expression for @code{globa +
31576 globb} will include bytecodes to record four bytes of memory at each
31577 of the addresses of @code{globa} and @code{globb}, while discarding
31578 the result of the addition, while an evaluation expression will do the
31579 addition and return the sum.
31581 @kindex maint info breakpoints
31582 @item @anchor{maint info breakpoints}maint info breakpoints
31583 Using the same format as @samp{info breakpoints}, display both the
31584 breakpoints you've set explicitly, and those @value{GDBN} is using for
31585 internal purposes. Internal breakpoints are shown with negative
31586 breakpoint numbers. The type column identifies what kind of breakpoint
31591 Normal, explicitly set breakpoint.
31594 Normal, explicitly set watchpoint.
31597 Internal breakpoint, used to handle correctly stepping through
31598 @code{longjmp} calls.
31600 @item longjmp resume
31601 Internal breakpoint at the target of a @code{longjmp}.
31604 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31607 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31610 Shared library events.
31614 @kindex set displaced-stepping
31615 @kindex show displaced-stepping
31616 @cindex displaced stepping support
31617 @cindex out-of-line single-stepping
31618 @item set displaced-stepping
31619 @itemx show displaced-stepping
31620 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31621 if the target supports it. Displaced stepping is a way to single-step
31622 over breakpoints without removing them from the inferior, by executing
31623 an out-of-line copy of the instruction that was originally at the
31624 breakpoint location. It is also known as out-of-line single-stepping.
31627 @item set displaced-stepping on
31628 If the target architecture supports it, @value{GDBN} will use
31629 displaced stepping to step over breakpoints.
31631 @item set displaced-stepping off
31632 @value{GDBN} will not use displaced stepping to step over breakpoints,
31633 even if such is supported by the target architecture.
31635 @cindex non-stop mode, and @samp{set displaced-stepping}
31636 @item set displaced-stepping auto
31637 This is the default mode. @value{GDBN} will use displaced stepping
31638 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31639 architecture supports displaced stepping.
31642 @kindex maint check-symtabs
31643 @item maint check-symtabs
31644 Check the consistency of psymtabs and symtabs.
31646 @kindex maint cplus first_component
31647 @item maint cplus first_component @var{name}
31648 Print the first C@t{++} class/namespace component of @var{name}.
31650 @kindex maint cplus namespace
31651 @item maint cplus namespace
31652 Print the list of possible C@t{++} namespaces.
31654 @kindex maint demangle
31655 @item maint demangle @var{name}
31656 Demangle a C@t{++} or Objective-C mangled @var{name}.
31658 @kindex maint deprecate
31659 @kindex maint undeprecate
31660 @cindex deprecated commands
31661 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31662 @itemx maint undeprecate @var{command}
31663 Deprecate or undeprecate the named @var{command}. Deprecated commands
31664 cause @value{GDBN} to issue a warning when you use them. The optional
31665 argument @var{replacement} says which newer command should be used in
31666 favor of the deprecated one; if it is given, @value{GDBN} will mention
31667 the replacement as part of the warning.
31669 @kindex maint dump-me
31670 @item maint dump-me
31671 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31672 Cause a fatal signal in the debugger and force it to dump its core.
31673 This is supported only on systems which support aborting a program
31674 with the @code{SIGQUIT} signal.
31676 @kindex maint internal-error
31677 @kindex maint internal-warning
31678 @item maint internal-error @r{[}@var{message-text}@r{]}
31679 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31680 Cause @value{GDBN} to call the internal function @code{internal_error}
31681 or @code{internal_warning} and hence behave as though an internal error
31682 or internal warning has been detected. In addition to reporting the
31683 internal problem, these functions give the user the opportunity to
31684 either quit @value{GDBN} or create a core file of the current
31685 @value{GDBN} session.
31687 These commands take an optional parameter @var{message-text} that is
31688 used as the text of the error or warning message.
31690 Here's an example of using @code{internal-error}:
31693 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31694 @dots{}/maint.c:121: internal-error: testing, 1, 2
31695 A problem internal to GDB has been detected. Further
31696 debugging may prove unreliable.
31697 Quit this debugging session? (y or n) @kbd{n}
31698 Create a core file? (y or n) @kbd{n}
31702 @cindex @value{GDBN} internal error
31703 @cindex internal errors, control of @value{GDBN} behavior
31705 @kindex maint set internal-error
31706 @kindex maint show internal-error
31707 @kindex maint set internal-warning
31708 @kindex maint show internal-warning
31709 @item maint set internal-error @var{action} [ask|yes|no]
31710 @itemx maint show internal-error @var{action}
31711 @itemx maint set internal-warning @var{action} [ask|yes|no]
31712 @itemx maint show internal-warning @var{action}
31713 When @value{GDBN} reports an internal problem (error or warning) it
31714 gives the user the opportunity to both quit @value{GDBN} and create a
31715 core file of the current @value{GDBN} session. These commands let you
31716 override the default behaviour for each particular @var{action},
31717 described in the table below.
31721 You can specify that @value{GDBN} should always (yes) or never (no)
31722 quit. The default is to ask the user what to do.
31725 You can specify that @value{GDBN} should always (yes) or never (no)
31726 create a core file. The default is to ask the user what to do.
31729 @kindex maint packet
31730 @item maint packet @var{text}
31731 If @value{GDBN} is talking to an inferior via the serial protocol,
31732 then this command sends the string @var{text} to the inferior, and
31733 displays the response packet. @value{GDBN} supplies the initial
31734 @samp{$} character, the terminating @samp{#} character, and the
31737 @kindex maint print architecture
31738 @item maint print architecture @r{[}@var{file}@r{]}
31739 Print the entire architecture configuration. The optional argument
31740 @var{file} names the file where the output goes.
31742 @kindex maint print c-tdesc
31743 @item maint print c-tdesc
31744 Print the current target description (@pxref{Target Descriptions}) as
31745 a C source file. The created source file can be used in @value{GDBN}
31746 when an XML parser is not available to parse the description.
31748 @kindex maint print dummy-frames
31749 @item maint print dummy-frames
31750 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31753 (@value{GDBP}) @kbd{b add}
31755 (@value{GDBP}) @kbd{print add(2,3)}
31756 Breakpoint 2, add (a=2, b=3) at @dots{}
31758 The program being debugged stopped while in a function called from GDB.
31760 (@value{GDBP}) @kbd{maint print dummy-frames}
31761 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31762 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31763 call_lo=0x01014000 call_hi=0x01014001
31767 Takes an optional file parameter.
31769 @kindex maint print registers
31770 @kindex maint print raw-registers
31771 @kindex maint print cooked-registers
31772 @kindex maint print register-groups
31773 @kindex maint print remote-registers
31774 @item maint print registers @r{[}@var{file}@r{]}
31775 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31776 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31777 @itemx maint print register-groups @r{[}@var{file}@r{]}
31778 @itemx maint print remote-registers @r{[}@var{file}@r{]}
31779 Print @value{GDBN}'s internal register data structures.
31781 The command @code{maint print raw-registers} includes the contents of
31782 the raw register cache; the command @code{maint print
31783 cooked-registers} includes the (cooked) value of all registers,
31784 including registers which aren't available on the target nor visible
31785 to user; the command @code{maint print register-groups} includes the
31786 groups that each register is a member of; and the command @code{maint
31787 print remote-registers} includes the remote target's register numbers
31788 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
31789 @value{GDBN} Internals}.
31791 These commands take an optional parameter, a file name to which to
31792 write the information.
31794 @kindex maint print reggroups
31795 @item maint print reggroups @r{[}@var{file}@r{]}
31796 Print @value{GDBN}'s internal register group data structures. The
31797 optional argument @var{file} tells to what file to write the
31800 The register groups info looks like this:
31803 (@value{GDBP}) @kbd{maint print reggroups}
31816 This command forces @value{GDBN} to flush its internal register cache.
31818 @kindex maint print objfiles
31819 @cindex info for known object files
31820 @item maint print objfiles
31821 Print a dump of all known object files. For each object file, this
31822 command prints its name, address in memory, and all of its psymtabs
31825 @kindex maint print section-scripts
31826 @cindex info for known .debug_gdb_scripts-loaded scripts
31827 @item maint print section-scripts [@var{regexp}]
31828 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31829 If @var{regexp} is specified, only print scripts loaded by object files
31830 matching @var{regexp}.
31831 For each script, this command prints its name as specified in the objfile,
31832 and the full path if known.
31833 @xref{.debug_gdb_scripts section}.
31835 @kindex maint print statistics
31836 @cindex bcache statistics
31837 @item maint print statistics
31838 This command prints, for each object file in the program, various data
31839 about that object file followed by the byte cache (@dfn{bcache})
31840 statistics for the object file. The objfile data includes the number
31841 of minimal, partial, full, and stabs symbols, the number of types
31842 defined by the objfile, the number of as yet unexpanded psym tables,
31843 the number of line tables and string tables, and the amount of memory
31844 used by the various tables. The bcache statistics include the counts,
31845 sizes, and counts of duplicates of all and unique objects, max,
31846 average, and median entry size, total memory used and its overhead and
31847 savings, and various measures of the hash table size and chain
31850 @kindex maint print target-stack
31851 @cindex target stack description
31852 @item maint print target-stack
31853 A @dfn{target} is an interface between the debugger and a particular
31854 kind of file or process. Targets can be stacked in @dfn{strata},
31855 so that more than one target can potentially respond to a request.
31856 In particular, memory accesses will walk down the stack of targets
31857 until they find a target that is interested in handling that particular
31860 This command prints a short description of each layer that was pushed on
31861 the @dfn{target stack}, starting from the top layer down to the bottom one.
31863 @kindex maint print type
31864 @cindex type chain of a data type
31865 @item maint print type @var{expr}
31866 Print the type chain for a type specified by @var{expr}. The argument
31867 can be either a type name or a symbol. If it is a symbol, the type of
31868 that symbol is described. The type chain produced by this command is
31869 a recursive definition of the data type as stored in @value{GDBN}'s
31870 data structures, including its flags and contained types.
31872 @kindex maint set dwarf2 always-disassemble
31873 @kindex maint show dwarf2 always-disassemble
31874 @item maint set dwarf2 always-disassemble
31875 @item maint show dwarf2 always-disassemble
31876 Control the behavior of @code{info address} when using DWARF debugging
31879 The default is @code{off}, which means that @value{GDBN} should try to
31880 describe a variable's location in an easily readable format. When
31881 @code{on}, @value{GDBN} will instead display the DWARF location
31882 expression in an assembly-like format. Note that some locations are
31883 too complex for @value{GDBN} to describe simply; in this case you will
31884 always see the disassembly form.
31886 Here is an example of the resulting disassembly:
31889 (gdb) info addr argc
31890 Symbol "argc" is a complex DWARF expression:
31894 For more information on these expressions, see
31895 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31897 @kindex maint set dwarf2 max-cache-age
31898 @kindex maint show dwarf2 max-cache-age
31899 @item maint set dwarf2 max-cache-age
31900 @itemx maint show dwarf2 max-cache-age
31901 Control the DWARF 2 compilation unit cache.
31903 @cindex DWARF 2 compilation units cache
31904 In object files with inter-compilation-unit references, such as those
31905 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31906 reader needs to frequently refer to previously read compilation units.
31907 This setting controls how long a compilation unit will remain in the
31908 cache if it is not referenced. A higher limit means that cached
31909 compilation units will be stored in memory longer, and more total
31910 memory will be used. Setting it to zero disables caching, which will
31911 slow down @value{GDBN} startup, but reduce memory consumption.
31913 @kindex maint set profile
31914 @kindex maint show profile
31915 @cindex profiling GDB
31916 @item maint set profile
31917 @itemx maint show profile
31918 Control profiling of @value{GDBN}.
31920 Profiling will be disabled until you use the @samp{maint set profile}
31921 command to enable it. When you enable profiling, the system will begin
31922 collecting timing and execution count data; when you disable profiling or
31923 exit @value{GDBN}, the results will be written to a log file. Remember that
31924 if you use profiling, @value{GDBN} will overwrite the profiling log file
31925 (often called @file{gmon.out}). If you have a record of important profiling
31926 data in a @file{gmon.out} file, be sure to move it to a safe location.
31928 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31929 compiled with the @samp{-pg} compiler option.
31931 @kindex maint set show-debug-regs
31932 @kindex maint show show-debug-regs
31933 @cindex hardware debug registers
31934 @item maint set show-debug-regs
31935 @itemx maint show show-debug-regs
31936 Control whether to show variables that mirror the hardware debug
31937 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31938 enabled, the debug registers values are shown when @value{GDBN} inserts or
31939 removes a hardware breakpoint or watchpoint, and when the inferior
31940 triggers a hardware-assisted breakpoint or watchpoint.
31942 @kindex maint set show-all-tib
31943 @kindex maint show show-all-tib
31944 @item maint set show-all-tib
31945 @itemx maint show show-all-tib
31946 Control whether to show all non zero areas within a 1k block starting
31947 at thread local base, when using the @samp{info w32 thread-information-block}
31950 @kindex maint space
31951 @cindex memory used by commands
31953 Control whether to display memory usage for each command. If set to a
31954 nonzero value, @value{GDBN} will display how much memory each command
31955 took, following the command's own output. This can also be requested
31956 by invoking @value{GDBN} with the @option{--statistics} command-line
31957 switch (@pxref{Mode Options}).
31960 @cindex time of command execution
31962 Control whether to display the execution time for each command. If
31963 set to a nonzero value, @value{GDBN} will display how much time it
31964 took to execute each command, following the command's own output.
31965 The time is not printed for the commands that run the target, since
31966 there's no mechanism currently to compute how much time was spend
31967 by @value{GDBN} and how much time was spend by the program been debugged.
31968 it's not possibly currently
31969 This can also be requested by invoking @value{GDBN} with the
31970 @option{--statistics} command-line switch (@pxref{Mode Options}).
31972 @kindex maint translate-address
31973 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31974 Find the symbol stored at the location specified by the address
31975 @var{addr} and an optional section name @var{section}. If found,
31976 @value{GDBN} prints the name of the closest symbol and an offset from
31977 the symbol's location to the specified address. This is similar to
31978 the @code{info address} command (@pxref{Symbols}), except that this
31979 command also allows to find symbols in other sections.
31981 If section was not specified, the section in which the symbol was found
31982 is also printed. For dynamically linked executables, the name of
31983 executable or shared library containing the symbol is printed as well.
31987 The following command is useful for non-interactive invocations of
31988 @value{GDBN}, such as in the test suite.
31991 @item set watchdog @var{nsec}
31992 @kindex set watchdog
31993 @cindex watchdog timer
31994 @cindex timeout for commands
31995 Set the maximum number of seconds @value{GDBN} will wait for the
31996 target operation to finish. If this time expires, @value{GDBN}
31997 reports and error and the command is aborted.
31999 @item show watchdog
32000 Show the current setting of the target wait timeout.
32003 @node Remote Protocol
32004 @appendix @value{GDBN} Remote Serial Protocol
32009 * Stop Reply Packets::
32010 * General Query Packets::
32011 * Architecture-Specific Protocol Details::
32012 * Tracepoint Packets::
32013 * Host I/O Packets::
32015 * Notification Packets::
32016 * Remote Non-Stop::
32017 * Packet Acknowledgment::
32019 * File-I/O Remote Protocol Extension::
32020 * Library List Format::
32021 * Memory Map Format::
32022 * Thread List Format::
32023 * Traceframe Info Format::
32029 There may be occasions when you need to know something about the
32030 protocol---for example, if there is only one serial port to your target
32031 machine, you might want your program to do something special if it
32032 recognizes a packet meant for @value{GDBN}.
32034 In the examples below, @samp{->} and @samp{<-} are used to indicate
32035 transmitted and received data, respectively.
32037 @cindex protocol, @value{GDBN} remote serial
32038 @cindex serial protocol, @value{GDBN} remote
32039 @cindex remote serial protocol
32040 All @value{GDBN} commands and responses (other than acknowledgments
32041 and notifications, see @ref{Notification Packets}) are sent as a
32042 @var{packet}. A @var{packet} is introduced with the character
32043 @samp{$}, the actual @var{packet-data}, and the terminating character
32044 @samp{#} followed by a two-digit @var{checksum}:
32047 @code{$}@var{packet-data}@code{#}@var{checksum}
32051 @cindex checksum, for @value{GDBN} remote
32053 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32054 characters between the leading @samp{$} and the trailing @samp{#} (an
32055 eight bit unsigned checksum).
32057 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32058 specification also included an optional two-digit @var{sequence-id}:
32061 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32064 @cindex sequence-id, for @value{GDBN} remote
32066 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32067 has never output @var{sequence-id}s. Stubs that handle packets added
32068 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32070 When either the host or the target machine receives a packet, the first
32071 response expected is an acknowledgment: either @samp{+} (to indicate
32072 the package was received correctly) or @samp{-} (to request
32076 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32081 The @samp{+}/@samp{-} acknowledgments can be disabled
32082 once a connection is established.
32083 @xref{Packet Acknowledgment}, for details.
32085 The host (@value{GDBN}) sends @var{command}s, and the target (the
32086 debugging stub incorporated in your program) sends a @var{response}. In
32087 the case of step and continue @var{command}s, the response is only sent
32088 when the operation has completed, and the target has again stopped all
32089 threads in all attached processes. This is the default all-stop mode
32090 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32091 execution mode; see @ref{Remote Non-Stop}, for details.
32093 @var{packet-data} consists of a sequence of characters with the
32094 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32097 @cindex remote protocol, field separator
32098 Fields within the packet should be separated using @samp{,} @samp{;} or
32099 @samp{:}. Except where otherwise noted all numbers are represented in
32100 @sc{hex} with leading zeros suppressed.
32102 Implementors should note that prior to @value{GDBN} 5.0, the character
32103 @samp{:} could not appear as the third character in a packet (as it
32104 would potentially conflict with the @var{sequence-id}).
32106 @cindex remote protocol, binary data
32107 @anchor{Binary Data}
32108 Binary data in most packets is encoded either as two hexadecimal
32109 digits per byte of binary data. This allowed the traditional remote
32110 protocol to work over connections which were only seven-bit clean.
32111 Some packets designed more recently assume an eight-bit clean
32112 connection, and use a more efficient encoding to send and receive
32115 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32116 as an escape character. Any escaped byte is transmitted as the escape
32117 character followed by the original character XORed with @code{0x20}.
32118 For example, the byte @code{0x7d} would be transmitted as the two
32119 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32120 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32121 @samp{@}}) must always be escaped. Responses sent by the stub
32122 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32123 is not interpreted as the start of a run-length encoded sequence
32126 Response @var{data} can be run-length encoded to save space.
32127 Run-length encoding replaces runs of identical characters with one
32128 instance of the repeated character, followed by a @samp{*} and a
32129 repeat count. The repeat count is itself sent encoded, to avoid
32130 binary characters in @var{data}: a value of @var{n} is sent as
32131 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32132 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32133 code 32) for a repeat count of 3. (This is because run-length
32134 encoding starts to win for counts 3 or more.) Thus, for example,
32135 @samp{0* } is a run-length encoding of ``0000'': the space character
32136 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32139 The printable characters @samp{#} and @samp{$} or with a numeric value
32140 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32141 seven repeats (@samp{$}) can be expanded using a repeat count of only
32142 five (@samp{"}). For example, @samp{00000000} can be encoded as
32145 The error response returned for some packets includes a two character
32146 error number. That number is not well defined.
32148 @cindex empty response, for unsupported packets
32149 For any @var{command} not supported by the stub, an empty response
32150 (@samp{$#00}) should be returned. That way it is possible to extend the
32151 protocol. A newer @value{GDBN} can tell if a packet is supported based
32154 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
32155 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
32161 The following table provides a complete list of all currently defined
32162 @var{command}s and their corresponding response @var{data}.
32163 @xref{File-I/O Remote Protocol Extension}, for details about the File
32164 I/O extension of the remote protocol.
32166 Each packet's description has a template showing the packet's overall
32167 syntax, followed by an explanation of the packet's meaning. We
32168 include spaces in some of the templates for clarity; these are not
32169 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32170 separate its components. For example, a template like @samp{foo
32171 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32172 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32173 @var{baz}. @value{GDBN} does not transmit a space character between the
32174 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32177 @cindex @var{thread-id}, in remote protocol
32178 @anchor{thread-id syntax}
32179 Several packets and replies include a @var{thread-id} field to identify
32180 a thread. Normally these are positive numbers with a target-specific
32181 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32182 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32185 In addition, the remote protocol supports a multiprocess feature in
32186 which the @var{thread-id} syntax is extended to optionally include both
32187 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32188 The @var{pid} (process) and @var{tid} (thread) components each have the
32189 format described above: a positive number with target-specific
32190 interpretation formatted as a big-endian hex string, literal @samp{-1}
32191 to indicate all processes or threads (respectively), or @samp{0} to
32192 indicate an arbitrary process or thread. Specifying just a process, as
32193 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32194 error to specify all processes but a specific thread, such as
32195 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32196 for those packets and replies explicitly documented to include a process
32197 ID, rather than a @var{thread-id}.
32199 The multiprocess @var{thread-id} syntax extensions are only used if both
32200 @value{GDBN} and the stub report support for the @samp{multiprocess}
32201 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32204 Note that all packet forms beginning with an upper- or lower-case
32205 letter, other than those described here, are reserved for future use.
32207 Here are the packet descriptions.
32212 @cindex @samp{!} packet
32213 @anchor{extended mode}
32214 Enable extended mode. In extended mode, the remote server is made
32215 persistent. The @samp{R} packet is used to restart the program being
32221 The remote target both supports and has enabled extended mode.
32225 @cindex @samp{?} packet
32226 Indicate the reason the target halted. The reply is the same as for
32227 step and continue. This packet has a special interpretation when the
32228 target is in non-stop mode; see @ref{Remote Non-Stop}.
32231 @xref{Stop Reply Packets}, for the reply specifications.
32233 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32234 @cindex @samp{A} packet
32235 Initialized @code{argv[]} array passed into program. @var{arglen}
32236 specifies the number of bytes in the hex encoded byte stream
32237 @var{arg}. See @code{gdbserver} for more details.
32242 The arguments were set.
32248 @cindex @samp{b} packet
32249 (Don't use this packet; its behavior is not well-defined.)
32250 Change the serial line speed to @var{baud}.
32252 JTC: @emph{When does the transport layer state change? When it's
32253 received, or after the ACK is transmitted. In either case, there are
32254 problems if the command or the acknowledgment packet is dropped.}
32256 Stan: @emph{If people really wanted to add something like this, and get
32257 it working for the first time, they ought to modify ser-unix.c to send
32258 some kind of out-of-band message to a specially-setup stub and have the
32259 switch happen "in between" packets, so that from remote protocol's point
32260 of view, nothing actually happened.}
32262 @item B @var{addr},@var{mode}
32263 @cindex @samp{B} packet
32264 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32265 breakpoint at @var{addr}.
32267 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32268 (@pxref{insert breakpoint or watchpoint packet}).
32270 @cindex @samp{bc} packet
32273 Backward continue. Execute the target system in reverse. No parameter.
32274 @xref{Reverse Execution}, for more information.
32277 @xref{Stop Reply Packets}, for the reply specifications.
32279 @cindex @samp{bs} packet
32282 Backward single step. Execute one instruction in reverse. No parameter.
32283 @xref{Reverse Execution}, for more information.
32286 @xref{Stop Reply Packets}, for the reply specifications.
32288 @item c @r{[}@var{addr}@r{]}
32289 @cindex @samp{c} packet
32290 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32291 resume at current address.
32294 @xref{Stop Reply Packets}, for the reply specifications.
32296 @item C @var{sig}@r{[};@var{addr}@r{]}
32297 @cindex @samp{C} packet
32298 Continue with signal @var{sig} (hex signal number). If
32299 @samp{;@var{addr}} is omitted, resume at same address.
32302 @xref{Stop Reply Packets}, for the reply specifications.
32305 @cindex @samp{d} packet
32308 Don't use this packet; instead, define a general set packet
32309 (@pxref{General Query Packets}).
32313 @cindex @samp{D} packet
32314 The first form of the packet is used to detach @value{GDBN} from the
32315 remote system. It is sent to the remote target
32316 before @value{GDBN} disconnects via the @code{detach} command.
32318 The second form, including a process ID, is used when multiprocess
32319 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32320 detach only a specific process. The @var{pid} is specified as a
32321 big-endian hex string.
32331 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32332 @cindex @samp{F} packet
32333 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32334 This is part of the File-I/O protocol extension. @xref{File-I/O
32335 Remote Protocol Extension}, for the specification.
32338 @anchor{read registers packet}
32339 @cindex @samp{g} packet
32340 Read general registers.
32344 @item @var{XX@dots{}}
32345 Each byte of register data is described by two hex digits. The bytes
32346 with the register are transmitted in target byte order. The size of
32347 each register and their position within the @samp{g} packet are
32348 determined by the @value{GDBN} internal gdbarch functions
32349 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32350 specification of several standard @samp{g} packets is specified below.
32352 When reading registers from a trace frame (@pxref{Analyze Collected
32353 Data,,Using the Collected Data}), the stub may also return a string of
32354 literal @samp{x}'s in place of the register data digits, to indicate
32355 that the corresponding register has not been collected, thus its value
32356 is unavailable. For example, for an architecture with 4 registers of
32357 4 bytes each, the following reply indicates to @value{GDBN} that
32358 registers 0 and 2 have not been collected, while registers 1 and 3
32359 have been collected, and both have zero value:
32363 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32370 @item G @var{XX@dots{}}
32371 @cindex @samp{G} packet
32372 Write general registers. @xref{read registers packet}, for a
32373 description of the @var{XX@dots{}} data.
32383 @item H @var{c} @var{thread-id}
32384 @cindex @samp{H} packet
32385 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32386 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
32387 should be @samp{c} for step and continue operations, @samp{g} for other
32388 operations. The thread designator @var{thread-id} has the format and
32389 interpretation described in @ref{thread-id syntax}.
32400 @c 'H': How restrictive (or permissive) is the thread model. If a
32401 @c thread is selected and stopped, are other threads allowed
32402 @c to continue to execute? As I mentioned above, I think the
32403 @c semantics of each command when a thread is selected must be
32404 @c described. For example:
32406 @c 'g': If the stub supports threads and a specific thread is
32407 @c selected, returns the register block from that thread;
32408 @c otherwise returns current registers.
32410 @c 'G' If the stub supports threads and a specific thread is
32411 @c selected, sets the registers of the register block of
32412 @c that thread; otherwise sets current registers.
32414 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32415 @anchor{cycle step packet}
32416 @cindex @samp{i} packet
32417 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32418 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32419 step starting at that address.
32422 @cindex @samp{I} packet
32423 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32427 @cindex @samp{k} packet
32430 FIXME: @emph{There is no description of how to operate when a specific
32431 thread context has been selected (i.e.@: does 'k' kill only that
32434 @item m @var{addr},@var{length}
32435 @cindex @samp{m} packet
32436 Read @var{length} bytes of memory starting at address @var{addr}.
32437 Note that @var{addr} may not be aligned to any particular boundary.
32439 The stub need not use any particular size or alignment when gathering
32440 data from memory for the response; even if @var{addr} is word-aligned
32441 and @var{length} is a multiple of the word size, the stub is free to
32442 use byte accesses, or not. For this reason, this packet may not be
32443 suitable for accessing memory-mapped I/O devices.
32444 @cindex alignment of remote memory accesses
32445 @cindex size of remote memory accesses
32446 @cindex memory, alignment and size of remote accesses
32450 @item @var{XX@dots{}}
32451 Memory contents; each byte is transmitted as a two-digit hexadecimal
32452 number. The reply may contain fewer bytes than requested if the
32453 server was able to read only part of the region of memory.
32458 @item M @var{addr},@var{length}:@var{XX@dots{}}
32459 @cindex @samp{M} packet
32460 Write @var{length} bytes of memory starting at address @var{addr}.
32461 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32462 hexadecimal number.
32469 for an error (this includes the case where only part of the data was
32474 @cindex @samp{p} packet
32475 Read the value of register @var{n}; @var{n} is in hex.
32476 @xref{read registers packet}, for a description of how the returned
32477 register value is encoded.
32481 @item @var{XX@dots{}}
32482 the register's value
32486 Indicating an unrecognized @var{query}.
32489 @item P @var{n@dots{}}=@var{r@dots{}}
32490 @anchor{write register packet}
32491 @cindex @samp{P} packet
32492 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32493 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32494 digits for each byte in the register (target byte order).
32504 @item q @var{name} @var{params}@dots{}
32505 @itemx Q @var{name} @var{params}@dots{}
32506 @cindex @samp{q} packet
32507 @cindex @samp{Q} packet
32508 General query (@samp{q}) and set (@samp{Q}). These packets are
32509 described fully in @ref{General Query Packets}.
32512 @cindex @samp{r} packet
32513 Reset the entire system.
32515 Don't use this packet; use the @samp{R} packet instead.
32518 @cindex @samp{R} packet
32519 Restart the program being debugged. @var{XX}, while needed, is ignored.
32520 This packet is only available in extended mode (@pxref{extended mode}).
32522 The @samp{R} packet has no reply.
32524 @item s @r{[}@var{addr}@r{]}
32525 @cindex @samp{s} packet
32526 Single step. @var{addr} is the address at which to resume. If
32527 @var{addr} is omitted, resume at same address.
32530 @xref{Stop Reply Packets}, for the reply specifications.
32532 @item S @var{sig}@r{[};@var{addr}@r{]}
32533 @anchor{step with signal packet}
32534 @cindex @samp{S} packet
32535 Step with signal. This is analogous to the @samp{C} packet, but
32536 requests a single-step, rather than a normal resumption of execution.
32539 @xref{Stop Reply Packets}, for the reply specifications.
32541 @item t @var{addr}:@var{PP},@var{MM}
32542 @cindex @samp{t} packet
32543 Search backwards starting at address @var{addr} for a match with pattern
32544 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32545 @var{addr} must be at least 3 digits.
32547 @item T @var{thread-id}
32548 @cindex @samp{T} packet
32549 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32554 thread is still alive
32560 Packets starting with @samp{v} are identified by a multi-letter name,
32561 up to the first @samp{;} or @samp{?} (or the end of the packet).
32563 @item vAttach;@var{pid}
32564 @cindex @samp{vAttach} packet
32565 Attach to a new process with the specified process ID @var{pid}.
32566 The process ID is a
32567 hexadecimal integer identifying the process. In all-stop mode, all
32568 threads in the attached process are stopped; in non-stop mode, it may be
32569 attached without being stopped if that is supported by the target.
32571 @c In non-stop mode, on a successful vAttach, the stub should set the
32572 @c current thread to a thread of the newly-attached process. After
32573 @c attaching, GDB queries for the attached process's thread ID with qC.
32574 @c Also note that, from a user perspective, whether or not the
32575 @c target is stopped on attach in non-stop mode depends on whether you
32576 @c use the foreground or background version of the attach command, not
32577 @c on what vAttach does; GDB does the right thing with respect to either
32578 @c stopping or restarting threads.
32580 This packet is only available in extended mode (@pxref{extended mode}).
32586 @item @r{Any stop packet}
32587 for success in all-stop mode (@pxref{Stop Reply Packets})
32589 for success in non-stop mode (@pxref{Remote Non-Stop})
32592 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32593 @cindex @samp{vCont} packet
32594 Resume the inferior, specifying different actions for each thread.
32595 If an action is specified with no @var{thread-id}, then it is applied to any
32596 threads that don't have a specific action specified; if no default action is
32597 specified then other threads should remain stopped in all-stop mode and
32598 in their current state in non-stop mode.
32599 Specifying multiple
32600 default actions is an error; specifying no actions is also an error.
32601 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32603 Currently supported actions are:
32609 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32613 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32618 The optional argument @var{addr} normally associated with the
32619 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32620 not supported in @samp{vCont}.
32622 The @samp{t} action is only relevant in non-stop mode
32623 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32624 A stop reply should be generated for any affected thread not already stopped.
32625 When a thread is stopped by means of a @samp{t} action,
32626 the corresponding stop reply should indicate that the thread has stopped with
32627 signal @samp{0}, regardless of whether the target uses some other signal
32628 as an implementation detail.
32631 @xref{Stop Reply Packets}, for the reply specifications.
32634 @cindex @samp{vCont?} packet
32635 Request a list of actions supported by the @samp{vCont} packet.
32639 @item vCont@r{[};@var{action}@dots{}@r{]}
32640 The @samp{vCont} packet is supported. Each @var{action} is a supported
32641 command in the @samp{vCont} packet.
32643 The @samp{vCont} packet is not supported.
32646 @item vFile:@var{operation}:@var{parameter}@dots{}
32647 @cindex @samp{vFile} packet
32648 Perform a file operation on the target system. For details,
32649 see @ref{Host I/O Packets}.
32651 @item vFlashErase:@var{addr},@var{length}
32652 @cindex @samp{vFlashErase} packet
32653 Direct the stub to erase @var{length} bytes of flash starting at
32654 @var{addr}. The region may enclose any number of flash blocks, but
32655 its start and end must fall on block boundaries, as indicated by the
32656 flash block size appearing in the memory map (@pxref{Memory Map
32657 Format}). @value{GDBN} groups flash memory programming operations
32658 together, and sends a @samp{vFlashDone} request after each group; the
32659 stub is allowed to delay erase operation until the @samp{vFlashDone}
32660 packet is received.
32662 The stub must support @samp{vCont} if it reports support for
32663 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32664 this case @samp{vCont} actions can be specified to apply to all threads
32665 in a process by using the @samp{p@var{pid}.-1} form of the
32676 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32677 @cindex @samp{vFlashWrite} packet
32678 Direct the stub to write data to flash address @var{addr}. The data
32679 is passed in binary form using the same encoding as for the @samp{X}
32680 packet (@pxref{Binary Data}). The memory ranges specified by
32681 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32682 not overlap, and must appear in order of increasing addresses
32683 (although @samp{vFlashErase} packets for higher addresses may already
32684 have been received; the ordering is guaranteed only between
32685 @samp{vFlashWrite} packets). If a packet writes to an address that was
32686 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32687 target-specific method, the results are unpredictable.
32695 for vFlashWrite addressing non-flash memory
32701 @cindex @samp{vFlashDone} packet
32702 Indicate to the stub that flash programming operation is finished.
32703 The stub is permitted to delay or batch the effects of a group of
32704 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32705 @samp{vFlashDone} packet is received. The contents of the affected
32706 regions of flash memory are unpredictable until the @samp{vFlashDone}
32707 request is completed.
32709 @item vKill;@var{pid}
32710 @cindex @samp{vKill} packet
32711 Kill the process with the specified process ID. @var{pid} is a
32712 hexadecimal integer identifying the process. This packet is used in
32713 preference to @samp{k} when multiprocess protocol extensions are
32714 supported; see @ref{multiprocess extensions}.
32724 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32725 @cindex @samp{vRun} packet
32726 Run the program @var{filename}, passing it each @var{argument} on its
32727 command line. The file and arguments are hex-encoded strings. If
32728 @var{filename} is an empty string, the stub may use a default program
32729 (e.g.@: the last program run). The program is created in the stopped
32732 @c FIXME: What about non-stop mode?
32734 This packet is only available in extended mode (@pxref{extended mode}).
32740 @item @r{Any stop packet}
32741 for success (@pxref{Stop Reply Packets})
32745 @anchor{vStopped packet}
32746 @cindex @samp{vStopped} packet
32748 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32749 reply and prompt for the stub to report another one.
32753 @item @r{Any stop packet}
32754 if there is another unreported stop event (@pxref{Stop Reply Packets})
32756 if there are no unreported stop events
32759 @item X @var{addr},@var{length}:@var{XX@dots{}}
32761 @cindex @samp{X} packet
32762 Write data to memory, where the data is transmitted in binary.
32763 @var{addr} is address, @var{length} is number of bytes,
32764 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32774 @item z @var{type},@var{addr},@var{kind}
32775 @itemx Z @var{type},@var{addr},@var{kind}
32776 @anchor{insert breakpoint or watchpoint packet}
32777 @cindex @samp{z} packet
32778 @cindex @samp{Z} packets
32779 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32780 watchpoint starting at address @var{address} of kind @var{kind}.
32782 Each breakpoint and watchpoint packet @var{type} is documented
32785 @emph{Implementation notes: A remote target shall return an empty string
32786 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32787 remote target shall support either both or neither of a given
32788 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32789 avoid potential problems with duplicate packets, the operations should
32790 be implemented in an idempotent way.}
32792 @item z0,@var{addr},@var{kind}
32793 @itemx Z0,@var{addr},@var{kind}
32794 @cindex @samp{z0} packet
32795 @cindex @samp{Z0} packet
32796 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32797 @var{addr} of type @var{kind}.
32799 A memory breakpoint is implemented by replacing the instruction at
32800 @var{addr} with a software breakpoint or trap instruction. The
32801 @var{kind} is target-specific and typically indicates the size of
32802 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32803 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32804 architectures have additional meanings for @var{kind};
32805 see @ref{Architecture-Specific Protocol Details}.
32807 @emph{Implementation note: It is possible for a target to copy or move
32808 code that contains memory breakpoints (e.g., when implementing
32809 overlays). The behavior of this packet, in the presence of such a
32810 target, is not defined.}
32822 @item z1,@var{addr},@var{kind}
32823 @itemx Z1,@var{addr},@var{kind}
32824 @cindex @samp{z1} packet
32825 @cindex @samp{Z1} packet
32826 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32827 address @var{addr}.
32829 A hardware breakpoint is implemented using a mechanism that is not
32830 dependant on being able to modify the target's memory. @var{kind}
32831 has the same meaning as in @samp{Z0} packets.
32833 @emph{Implementation note: A hardware breakpoint is not affected by code
32846 @item z2,@var{addr},@var{kind}
32847 @itemx Z2,@var{addr},@var{kind}
32848 @cindex @samp{z2} packet
32849 @cindex @samp{Z2} packet
32850 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32851 @var{kind} is interpreted as the number of bytes to watch.
32863 @item z3,@var{addr},@var{kind}
32864 @itemx Z3,@var{addr},@var{kind}
32865 @cindex @samp{z3} packet
32866 @cindex @samp{Z3} packet
32867 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32868 @var{kind} is interpreted as the number of bytes to watch.
32880 @item z4,@var{addr},@var{kind}
32881 @itemx Z4,@var{addr},@var{kind}
32882 @cindex @samp{z4} packet
32883 @cindex @samp{Z4} packet
32884 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32885 @var{kind} is interpreted as the number of bytes to watch.
32899 @node Stop Reply Packets
32900 @section Stop Reply Packets
32901 @cindex stop reply packets
32903 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32904 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32905 receive any of the below as a reply. Except for @samp{?}
32906 and @samp{vStopped}, that reply is only returned
32907 when the target halts. In the below the exact meaning of @dfn{signal
32908 number} is defined by the header @file{include/gdb/signals.h} in the
32909 @value{GDBN} source code.
32911 As in the description of request packets, we include spaces in the
32912 reply templates for clarity; these are not part of the reply packet's
32913 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32919 The program received signal number @var{AA} (a two-digit hexadecimal
32920 number). This is equivalent to a @samp{T} response with no
32921 @var{n}:@var{r} pairs.
32923 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32924 @cindex @samp{T} packet reply
32925 The program received signal number @var{AA} (a two-digit hexadecimal
32926 number). This is equivalent to an @samp{S} response, except that the
32927 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32928 and other information directly in the stop reply packet, reducing
32929 round-trip latency. Single-step and breakpoint traps are reported
32930 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32934 If @var{n} is a hexadecimal number, it is a register number, and the
32935 corresponding @var{r} gives that register's value. @var{r} is a
32936 series of bytes in target byte order, with each byte given by a
32937 two-digit hex number.
32940 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32941 the stopped thread, as specified in @ref{thread-id syntax}.
32944 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32945 the core on which the stop event was detected.
32948 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32949 specific event that stopped the target. The currently defined stop
32950 reasons are listed below. @var{aa} should be @samp{05}, the trap
32951 signal. At most one stop reason should be present.
32954 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32955 and go on to the next; this allows us to extend the protocol in the
32959 The currently defined stop reasons are:
32965 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32968 @cindex shared library events, remote reply
32970 The packet indicates that the loaded libraries have changed.
32971 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32972 list of loaded libraries. @var{r} is ignored.
32974 @cindex replay log events, remote reply
32976 The packet indicates that the target cannot continue replaying
32977 logged execution events, because it has reached the end (or the
32978 beginning when executing backward) of the log. The value of @var{r}
32979 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32980 for more information.
32984 @itemx W @var{AA} ; process:@var{pid}
32985 The process exited, and @var{AA} is the exit status. This is only
32986 applicable to certain targets.
32988 The second form of the response, including the process ID of the exited
32989 process, can be used only when @value{GDBN} has reported support for
32990 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32991 The @var{pid} is formatted as a big-endian hex string.
32994 @itemx X @var{AA} ; process:@var{pid}
32995 The process terminated with signal @var{AA}.
32997 The second form of the response, including the process ID of the
32998 terminated process, can be used only when @value{GDBN} has reported
32999 support for multiprocess protocol extensions; see @ref{multiprocess
33000 extensions}. The @var{pid} is formatted as a big-endian hex string.
33002 @item O @var{XX}@dots{}
33003 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
33004 written as the program's console output. This can happen at any time
33005 while the program is running and the debugger should continue to wait
33006 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
33008 @item F @var{call-id},@var{parameter}@dots{}
33009 @var{call-id} is the identifier which says which host system call should
33010 be called. This is just the name of the function. Translation into the
33011 correct system call is only applicable as it's defined in @value{GDBN}.
33012 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
33015 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
33016 this very system call.
33018 The target replies with this packet when it expects @value{GDBN} to
33019 call a host system call on behalf of the target. @value{GDBN} replies
33020 with an appropriate @samp{F} packet and keeps up waiting for the next
33021 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33022 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33023 Protocol Extension}, for more details.
33027 @node General Query Packets
33028 @section General Query Packets
33029 @cindex remote query requests
33031 Packets starting with @samp{q} are @dfn{general query packets};
33032 packets starting with @samp{Q} are @dfn{general set packets}. General
33033 query and set packets are a semi-unified form for retrieving and
33034 sending information to and from the stub.
33036 The initial letter of a query or set packet is followed by a name
33037 indicating what sort of thing the packet applies to. For example,
33038 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33039 definitions with the stub. These packet names follow some
33044 The name must not contain commas, colons or semicolons.
33046 Most @value{GDBN} query and set packets have a leading upper case
33049 The names of custom vendor packets should use a company prefix, in
33050 lower case, followed by a period. For example, packets designed at
33051 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33052 foos) or @samp{Qacme.bar} (for setting bars).
33055 The name of a query or set packet should be separated from any
33056 parameters by a @samp{:}; the parameters themselves should be
33057 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33058 full packet name, and check for a separator or the end of the packet,
33059 in case two packet names share a common prefix. New packets should not begin
33060 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33061 packets predate these conventions, and have arguments without any terminator
33062 for the packet name; we suspect they are in widespread use in places that
33063 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33064 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33067 Like the descriptions of the other packets, each description here
33068 has a template showing the packet's overall syntax, followed by an
33069 explanation of the packet's meaning. We include spaces in some of the
33070 templates for clarity; these are not part of the packet's syntax. No
33071 @value{GDBN} packet uses spaces to separate its components.
33073 Here are the currently defined query and set packets:
33077 @item QAllow:@var{op}:@var{val}@dots{}
33078 @cindex @samp{QAllow} packet
33079 Specify which operations @value{GDBN} expects to request of the
33080 target, as a semicolon-separated list of operation name and value
33081 pairs. Possible values for @var{op} include @samp{WriteReg},
33082 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33083 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33084 indicating that @value{GDBN} will not request the operation, or 1,
33085 indicating that it may. (The target can then use this to set up its
33086 own internals optimally, for instance if the debugger never expects to
33087 insert breakpoints, it may not need to install its own trap handler.)
33090 @cindex current thread, remote request
33091 @cindex @samp{qC} packet
33092 Return the current thread ID.
33096 @item QC @var{thread-id}
33097 Where @var{thread-id} is a thread ID as documented in
33098 @ref{thread-id syntax}.
33099 @item @r{(anything else)}
33100 Any other reply implies the old thread ID.
33103 @item qCRC:@var{addr},@var{length}
33104 @cindex CRC of memory block, remote request
33105 @cindex @samp{qCRC} packet
33106 Compute the CRC checksum of a block of memory using CRC-32 defined in
33107 IEEE 802.3. The CRC is computed byte at a time, taking the most
33108 significant bit of each byte first. The initial pattern code
33109 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33111 @emph{Note:} This is the same CRC used in validating separate debug
33112 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33113 Files}). However the algorithm is slightly different. When validating
33114 separate debug files, the CRC is computed taking the @emph{least}
33115 significant bit of each byte first, and the final result is inverted to
33116 detect trailing zeros.
33121 An error (such as memory fault)
33122 @item C @var{crc32}
33123 The specified memory region's checksum is @var{crc32}.
33127 @itemx qsThreadInfo
33128 @cindex list active threads, remote request
33129 @cindex @samp{qfThreadInfo} packet
33130 @cindex @samp{qsThreadInfo} packet
33131 Obtain a list of all active thread IDs from the target (OS). Since there
33132 may be too many active threads to fit into one reply packet, this query
33133 works iteratively: it may require more than one query/reply sequence to
33134 obtain the entire list of threads. The first query of the sequence will
33135 be the @samp{qfThreadInfo} query; subsequent queries in the
33136 sequence will be the @samp{qsThreadInfo} query.
33138 NOTE: This packet replaces the @samp{qL} query (see below).
33142 @item m @var{thread-id}
33144 @item m @var{thread-id},@var{thread-id}@dots{}
33145 a comma-separated list of thread IDs
33147 (lower case letter @samp{L}) denotes end of list.
33150 In response to each query, the target will reply with a list of one or
33151 more thread IDs, separated by commas.
33152 @value{GDBN} will respond to each reply with a request for more thread
33153 ids (using the @samp{qs} form of the query), until the target responds
33154 with @samp{l} (lower-case ell, for @dfn{last}).
33155 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33158 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33159 @cindex get thread-local storage address, remote request
33160 @cindex @samp{qGetTLSAddr} packet
33161 Fetch the address associated with thread local storage specified
33162 by @var{thread-id}, @var{offset}, and @var{lm}.
33164 @var{thread-id} is the thread ID associated with the
33165 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33167 @var{offset} is the (big endian, hex encoded) offset associated with the
33168 thread local variable. (This offset is obtained from the debug
33169 information associated with the variable.)
33171 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33172 load module associated with the thread local storage. For example,
33173 a @sc{gnu}/Linux system will pass the link map address of the shared
33174 object associated with the thread local storage under consideration.
33175 Other operating environments may choose to represent the load module
33176 differently, so the precise meaning of this parameter will vary.
33180 @item @var{XX}@dots{}
33181 Hex encoded (big endian) bytes representing the address of the thread
33182 local storage requested.
33185 An error occurred. @var{nn} are hex digits.
33188 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33191 @item qGetTIBAddr:@var{thread-id}
33192 @cindex get thread information block address
33193 @cindex @samp{qGetTIBAddr} packet
33194 Fetch address of the Windows OS specific Thread Information Block.
33196 @var{thread-id} is the thread ID associated with the thread.
33200 @item @var{XX}@dots{}
33201 Hex encoded (big endian) bytes representing the linear address of the
33202 thread information block.
33205 An error occured. This means that either the thread was not found, or the
33206 address could not be retrieved.
33209 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33212 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33213 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33214 digit) is one to indicate the first query and zero to indicate a
33215 subsequent query; @var{threadcount} (two hex digits) is the maximum
33216 number of threads the response packet can contain; and @var{nextthread}
33217 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33218 returned in the response as @var{argthread}.
33220 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33224 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33225 Where: @var{count} (two hex digits) is the number of threads being
33226 returned; @var{done} (one hex digit) is zero to indicate more threads
33227 and one indicates no further threads; @var{argthreadid} (eight hex
33228 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33229 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33230 digits). See @code{remote.c:parse_threadlist_response()}.
33234 @cindex section offsets, remote request
33235 @cindex @samp{qOffsets} packet
33236 Get section offsets that the target used when relocating the downloaded
33241 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33242 Relocate the @code{Text} section by @var{xxx} from its original address.
33243 Relocate the @code{Data} section by @var{yyy} from its original address.
33244 If the object file format provides segment information (e.g.@: @sc{elf}
33245 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33246 segments by the supplied offsets.
33248 @emph{Note: while a @code{Bss} offset may be included in the response,
33249 @value{GDBN} ignores this and instead applies the @code{Data} offset
33250 to the @code{Bss} section.}
33252 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33253 Relocate the first segment of the object file, which conventionally
33254 contains program code, to a starting address of @var{xxx}. If
33255 @samp{DataSeg} is specified, relocate the second segment, which
33256 conventionally contains modifiable data, to a starting address of
33257 @var{yyy}. @value{GDBN} will report an error if the object file
33258 does not contain segment information, or does not contain at least
33259 as many segments as mentioned in the reply. Extra segments are
33260 kept at fixed offsets relative to the last relocated segment.
33263 @item qP @var{mode} @var{thread-id}
33264 @cindex thread information, remote request
33265 @cindex @samp{qP} packet
33266 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33267 encoded 32 bit mode; @var{thread-id} is a thread ID
33268 (@pxref{thread-id syntax}).
33270 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33273 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33277 @cindex non-stop mode, remote request
33278 @cindex @samp{QNonStop} packet
33280 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33281 @xref{Remote Non-Stop}, for more information.
33286 The request succeeded.
33289 An error occurred. @var{nn} are hex digits.
33292 An empty reply indicates that @samp{QNonStop} is not supported by
33296 This packet is not probed by default; the remote stub must request it,
33297 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33298 Use of this packet is controlled by the @code{set non-stop} command;
33299 @pxref{Non-Stop Mode}.
33301 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33302 @cindex pass signals to inferior, remote request
33303 @cindex @samp{QPassSignals} packet
33304 @anchor{QPassSignals}
33305 Each listed @var{signal} should be passed directly to the inferior process.
33306 Signals are numbered identically to continue packets and stop replies
33307 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33308 strictly greater than the previous item. These signals do not need to stop
33309 the inferior, or be reported to @value{GDBN}. All other signals should be
33310 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33311 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33312 new list. This packet improves performance when using @samp{handle
33313 @var{signal} nostop noprint pass}.
33318 The request succeeded.
33321 An error occurred. @var{nn} are hex digits.
33324 An empty reply indicates that @samp{QPassSignals} is not supported by
33328 Use of this packet is controlled by the @code{set remote pass-signals}
33329 command (@pxref{Remote Configuration, set remote pass-signals}).
33330 This packet is not probed by default; the remote stub must request it,
33331 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33333 @item qRcmd,@var{command}
33334 @cindex execute remote command, remote request
33335 @cindex @samp{qRcmd} packet
33336 @var{command} (hex encoded) is passed to the local interpreter for
33337 execution. Invalid commands should be reported using the output
33338 string. Before the final result packet, the target may also respond
33339 with a number of intermediate @samp{O@var{output}} console output
33340 packets. @emph{Implementors should note that providing access to a
33341 stubs's interpreter may have security implications}.
33346 A command response with no output.
33348 A command response with the hex encoded output string @var{OUTPUT}.
33350 Indicate a badly formed request.
33352 An empty reply indicates that @samp{qRcmd} is not recognized.
33355 (Note that the @code{qRcmd} packet's name is separated from the
33356 command by a @samp{,}, not a @samp{:}, contrary to the naming
33357 conventions above. Please don't use this packet as a model for new
33360 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33361 @cindex searching memory, in remote debugging
33362 @cindex @samp{qSearch:memory} packet
33363 @anchor{qSearch memory}
33364 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33365 @var{address} and @var{length} are encoded in hex.
33366 @var{search-pattern} is a sequence of bytes, hex encoded.
33371 The pattern was not found.
33373 The pattern was found at @var{address}.
33375 A badly formed request or an error was encountered while searching memory.
33377 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33380 @item QStartNoAckMode
33381 @cindex @samp{QStartNoAckMode} packet
33382 @anchor{QStartNoAckMode}
33383 Request that the remote stub disable the normal @samp{+}/@samp{-}
33384 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33389 The stub has switched to no-acknowledgment mode.
33390 @value{GDBN} acknowledges this reponse,
33391 but neither the stub nor @value{GDBN} shall send or expect further
33392 @samp{+}/@samp{-} acknowledgments in the current connection.
33394 An empty reply indicates that the stub does not support no-acknowledgment mode.
33397 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33398 @cindex supported packets, remote query
33399 @cindex features of the remote protocol
33400 @cindex @samp{qSupported} packet
33401 @anchor{qSupported}
33402 Tell the remote stub about features supported by @value{GDBN}, and
33403 query the stub for features it supports. This packet allows
33404 @value{GDBN} and the remote stub to take advantage of each others'
33405 features. @samp{qSupported} also consolidates multiple feature probes
33406 at startup, to improve @value{GDBN} performance---a single larger
33407 packet performs better than multiple smaller probe packets on
33408 high-latency links. Some features may enable behavior which must not
33409 be on by default, e.g.@: because it would confuse older clients or
33410 stubs. Other features may describe packets which could be
33411 automatically probed for, but are not. These features must be
33412 reported before @value{GDBN} will use them. This ``default
33413 unsupported'' behavior is not appropriate for all packets, but it
33414 helps to keep the initial connection time under control with new
33415 versions of @value{GDBN} which support increasing numbers of packets.
33419 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33420 The stub supports or does not support each returned @var{stubfeature},
33421 depending on the form of each @var{stubfeature} (see below for the
33424 An empty reply indicates that @samp{qSupported} is not recognized,
33425 or that no features needed to be reported to @value{GDBN}.
33428 The allowed forms for each feature (either a @var{gdbfeature} in the
33429 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33433 @item @var{name}=@var{value}
33434 The remote protocol feature @var{name} is supported, and associated
33435 with the specified @var{value}. The format of @var{value} depends
33436 on the feature, but it must not include a semicolon.
33438 The remote protocol feature @var{name} is supported, and does not
33439 need an associated value.
33441 The remote protocol feature @var{name} is not supported.
33443 The remote protocol feature @var{name} may be supported, and
33444 @value{GDBN} should auto-detect support in some other way when it is
33445 needed. This form will not be used for @var{gdbfeature} notifications,
33446 but may be used for @var{stubfeature} responses.
33449 Whenever the stub receives a @samp{qSupported} request, the
33450 supplied set of @value{GDBN} features should override any previous
33451 request. This allows @value{GDBN} to put the stub in a known
33452 state, even if the stub had previously been communicating with
33453 a different version of @value{GDBN}.
33455 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33460 This feature indicates whether @value{GDBN} supports multiprocess
33461 extensions to the remote protocol. @value{GDBN} does not use such
33462 extensions unless the stub also reports that it supports them by
33463 including @samp{multiprocess+} in its @samp{qSupported} reply.
33464 @xref{multiprocess extensions}, for details.
33467 This feature indicates that @value{GDBN} supports the XML target
33468 description. If the stub sees @samp{xmlRegisters=} with target
33469 specific strings separated by a comma, it will report register
33473 This feature indicates whether @value{GDBN} supports the
33474 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33475 instruction reply packet}).
33478 Stubs should ignore any unknown values for
33479 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33480 packet supports receiving packets of unlimited length (earlier
33481 versions of @value{GDBN} may reject overly long responses). Additional values
33482 for @var{gdbfeature} may be defined in the future to let the stub take
33483 advantage of new features in @value{GDBN}, e.g.@: incompatible
33484 improvements in the remote protocol---the @samp{multiprocess} feature is
33485 an example of such a feature. The stub's reply should be independent
33486 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33487 describes all the features it supports, and then the stub replies with
33488 all the features it supports.
33490 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33491 responses, as long as each response uses one of the standard forms.
33493 Some features are flags. A stub which supports a flag feature
33494 should respond with a @samp{+} form response. Other features
33495 require values, and the stub should respond with an @samp{=}
33498 Each feature has a default value, which @value{GDBN} will use if
33499 @samp{qSupported} is not available or if the feature is not mentioned
33500 in the @samp{qSupported} response. The default values are fixed; a
33501 stub is free to omit any feature responses that match the defaults.
33503 Not all features can be probed, but for those which can, the probing
33504 mechanism is useful: in some cases, a stub's internal
33505 architecture may not allow the protocol layer to know some information
33506 about the underlying target in advance. This is especially common in
33507 stubs which may be configured for multiple targets.
33509 These are the currently defined stub features and their properties:
33511 @multitable @columnfractions 0.35 0.2 0.12 0.2
33512 @c NOTE: The first row should be @headitem, but we do not yet require
33513 @c a new enough version of Texinfo (4.7) to use @headitem.
33515 @tab Value Required
33519 @item @samp{PacketSize}
33524 @item @samp{qXfer:auxv:read}
33529 @item @samp{qXfer:features:read}
33534 @item @samp{qXfer:libraries:read}
33539 @item @samp{qXfer:memory-map:read}
33544 @item @samp{qXfer:sdata:read}
33549 @item @samp{qXfer:spu:read}
33554 @item @samp{qXfer:spu:write}
33559 @item @samp{qXfer:siginfo:read}
33564 @item @samp{qXfer:siginfo:write}
33569 @item @samp{qXfer:threads:read}
33574 @item @samp{qXfer:traceframe-info:read}
33580 @item @samp{QNonStop}
33585 @item @samp{QPassSignals}
33590 @item @samp{QStartNoAckMode}
33595 @item @samp{multiprocess}
33600 @item @samp{ConditionalTracepoints}
33605 @item @samp{ReverseContinue}
33610 @item @samp{ReverseStep}
33615 @item @samp{TracepointSource}
33620 @item @samp{QAllow}
33627 These are the currently defined stub features, in more detail:
33630 @cindex packet size, remote protocol
33631 @item PacketSize=@var{bytes}
33632 The remote stub can accept packets up to at least @var{bytes} in
33633 length. @value{GDBN} will send packets up to this size for bulk
33634 transfers, and will never send larger packets. This is a limit on the
33635 data characters in the packet, including the frame and checksum.
33636 There is no trailing NUL byte in a remote protocol packet; if the stub
33637 stores packets in a NUL-terminated format, it should allow an extra
33638 byte in its buffer for the NUL. If this stub feature is not supported,
33639 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33641 @item qXfer:auxv:read
33642 The remote stub understands the @samp{qXfer:auxv:read} packet
33643 (@pxref{qXfer auxiliary vector read}).
33645 @item qXfer:features:read
33646 The remote stub understands the @samp{qXfer:features:read} packet
33647 (@pxref{qXfer target description read}).
33649 @item qXfer:libraries:read
33650 The remote stub understands the @samp{qXfer:libraries:read} packet
33651 (@pxref{qXfer library list read}).
33653 @item qXfer:memory-map:read
33654 The remote stub understands the @samp{qXfer:memory-map:read} packet
33655 (@pxref{qXfer memory map read}).
33657 @item qXfer:sdata:read
33658 The remote stub understands the @samp{qXfer:sdata:read} packet
33659 (@pxref{qXfer sdata read}).
33661 @item qXfer:spu:read
33662 The remote stub understands the @samp{qXfer:spu:read} packet
33663 (@pxref{qXfer spu read}).
33665 @item qXfer:spu:write
33666 The remote stub understands the @samp{qXfer:spu:write} packet
33667 (@pxref{qXfer spu write}).
33669 @item qXfer:siginfo:read
33670 The remote stub understands the @samp{qXfer:siginfo:read} packet
33671 (@pxref{qXfer siginfo read}).
33673 @item qXfer:siginfo:write
33674 The remote stub understands the @samp{qXfer:siginfo:write} packet
33675 (@pxref{qXfer siginfo write}).
33677 @item qXfer:threads:read
33678 The remote stub understands the @samp{qXfer:threads:read} packet
33679 (@pxref{qXfer threads read}).
33681 @item qXfer:traceframe-info:read
33682 The remote stub understands the @samp{qXfer:traceframe-info:read}
33683 packet (@pxref{qXfer traceframe info read}).
33686 The remote stub understands the @samp{QNonStop} packet
33687 (@pxref{QNonStop}).
33690 The remote stub understands the @samp{QPassSignals} packet
33691 (@pxref{QPassSignals}).
33693 @item QStartNoAckMode
33694 The remote stub understands the @samp{QStartNoAckMode} packet and
33695 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33698 @anchor{multiprocess extensions}
33699 @cindex multiprocess extensions, in remote protocol
33700 The remote stub understands the multiprocess extensions to the remote
33701 protocol syntax. The multiprocess extensions affect the syntax of
33702 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33703 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33704 replies. Note that reporting this feature indicates support for the
33705 syntactic extensions only, not that the stub necessarily supports
33706 debugging of more than one process at a time. The stub must not use
33707 multiprocess extensions in packet replies unless @value{GDBN} has also
33708 indicated it supports them in its @samp{qSupported} request.
33710 @item qXfer:osdata:read
33711 The remote stub understands the @samp{qXfer:osdata:read} packet
33712 ((@pxref{qXfer osdata read}).
33714 @item ConditionalTracepoints
33715 The remote stub accepts and implements conditional expressions defined
33716 for tracepoints (@pxref{Tracepoint Conditions}).
33718 @item ReverseContinue
33719 The remote stub accepts and implements the reverse continue packet
33723 The remote stub accepts and implements the reverse step packet
33726 @item TracepointSource
33727 The remote stub understands the @samp{QTDPsrc} packet that supplies
33728 the source form of tracepoint definitions.
33731 The remote stub understands the @samp{QAllow} packet.
33733 @item StaticTracepoint
33734 @cindex static tracepoints, in remote protocol
33735 The remote stub supports static tracepoints.
33740 @cindex symbol lookup, remote request
33741 @cindex @samp{qSymbol} packet
33742 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33743 requests. Accept requests from the target for the values of symbols.
33748 The target does not need to look up any (more) symbols.
33749 @item qSymbol:@var{sym_name}
33750 The target requests the value of symbol @var{sym_name} (hex encoded).
33751 @value{GDBN} may provide the value by using the
33752 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33756 @item qSymbol:@var{sym_value}:@var{sym_name}
33757 Set the value of @var{sym_name} to @var{sym_value}.
33759 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33760 target has previously requested.
33762 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33763 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33769 The target does not need to look up any (more) symbols.
33770 @item qSymbol:@var{sym_name}
33771 The target requests the value of a new symbol @var{sym_name} (hex
33772 encoded). @value{GDBN} will continue to supply the values of symbols
33773 (if available), until the target ceases to request them.
33778 @item QTDisconnected
33785 @xref{Tracepoint Packets}.
33787 @item qThreadExtraInfo,@var{thread-id}
33788 @cindex thread attributes info, remote request
33789 @cindex @samp{qThreadExtraInfo} packet
33790 Obtain a printable string description of a thread's attributes from
33791 the target OS. @var{thread-id} is a thread ID;
33792 see @ref{thread-id syntax}. This
33793 string may contain anything that the target OS thinks is interesting
33794 for @value{GDBN} to tell the user about the thread. The string is
33795 displayed in @value{GDBN}'s @code{info threads} display. Some
33796 examples of possible thread extra info strings are @samp{Runnable}, or
33797 @samp{Blocked on Mutex}.
33801 @item @var{XX}@dots{}
33802 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33803 comprising the printable string containing the extra information about
33804 the thread's attributes.
33807 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33808 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33809 conventions above. Please don't use this packet as a model for new
33824 @xref{Tracepoint Packets}.
33826 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33827 @cindex read special object, remote request
33828 @cindex @samp{qXfer} packet
33829 @anchor{qXfer read}
33830 Read uninterpreted bytes from the target's special data area
33831 identified by the keyword @var{object}. Request @var{length} bytes
33832 starting at @var{offset} bytes into the data. The content and
33833 encoding of @var{annex} is specific to @var{object}; it can supply
33834 additional details about what data to access.
33836 Here are the specific requests of this form defined so far. All
33837 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33838 formats, listed below.
33841 @item qXfer:auxv:read::@var{offset},@var{length}
33842 @anchor{qXfer auxiliary vector read}
33843 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33844 auxiliary vector}. Note @var{annex} must be empty.
33846 This packet is not probed by default; the remote stub must request it,
33847 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33849 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33850 @anchor{qXfer target description read}
33851 Access the @dfn{target description}. @xref{Target Descriptions}. The
33852 annex specifies which XML document to access. The main description is
33853 always loaded from the @samp{target.xml} annex.
33855 This packet is not probed by default; the remote stub must request it,
33856 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33858 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33859 @anchor{qXfer library list read}
33860 Access the target's list of loaded libraries. @xref{Library List Format}.
33861 The annex part of the generic @samp{qXfer} packet must be empty
33862 (@pxref{qXfer read}).
33864 Targets which maintain a list of libraries in the program's memory do
33865 not need to implement this packet; it is designed for platforms where
33866 the operating system manages the list of loaded libraries.
33868 This packet is not probed by default; the remote stub must request it,
33869 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33871 @item qXfer:memory-map:read::@var{offset},@var{length}
33872 @anchor{qXfer memory map read}
33873 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33874 annex part of the generic @samp{qXfer} packet must be empty
33875 (@pxref{qXfer read}).
33877 This packet is not probed by default; the remote stub must request it,
33878 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33880 @item qXfer:sdata:read::@var{offset},@var{length}
33881 @anchor{qXfer sdata read}
33883 Read contents of the extra collected static tracepoint marker
33884 information. The annex part of the generic @samp{qXfer} packet must
33885 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33888 This packet is not probed by default; the remote stub must request it,
33889 by supplying an appropriate @samp{qSupported} response
33890 (@pxref{qSupported}).
33892 @item qXfer:siginfo:read::@var{offset},@var{length}
33893 @anchor{qXfer siginfo read}
33894 Read contents of the extra signal information on the target
33895 system. The annex part of the generic @samp{qXfer} packet must be
33896 empty (@pxref{qXfer read}).
33898 This packet is not probed by default; the remote stub must request it,
33899 by supplying an appropriate @samp{qSupported} response
33900 (@pxref{qSupported}).
33902 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33903 @anchor{qXfer spu read}
33904 Read contents of an @code{spufs} file on the target system. The
33905 annex specifies which file to read; it must be of the form
33906 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33907 in the target process, and @var{name} identifes the @code{spufs} file
33908 in that context to be accessed.
33910 This packet is not probed by default; the remote stub must request it,
33911 by supplying an appropriate @samp{qSupported} response
33912 (@pxref{qSupported}).
33914 @item qXfer:threads:read::@var{offset},@var{length}
33915 @anchor{qXfer threads read}
33916 Access the list of threads on target. @xref{Thread List Format}. The
33917 annex part of the generic @samp{qXfer} packet must be empty
33918 (@pxref{qXfer read}).
33920 This packet is not probed by default; the remote stub must request it,
33921 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33923 @item qXfer:traceframe-info:read::@var{offset},@var{length}
33924 @anchor{qXfer traceframe info read}
33926 Return a description of the current traceframe's contents.
33927 @xref{Traceframe Info Format}. The annex part of the generic
33928 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
33930 This packet is not probed by default; the remote stub must request it,
33931 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33933 @item qXfer:osdata:read::@var{offset},@var{length}
33934 @anchor{qXfer osdata read}
33935 Access the target's @dfn{operating system information}.
33936 @xref{Operating System Information}.
33943 Data @var{data} (@pxref{Binary Data}) has been read from the
33944 target. There may be more data at a higher address (although
33945 it is permitted to return @samp{m} even for the last valid
33946 block of data, as long as at least one byte of data was read).
33947 @var{data} may have fewer bytes than the @var{length} in the
33951 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33952 There is no more data to be read. @var{data} may have fewer bytes
33953 than the @var{length} in the request.
33956 The @var{offset} in the request is at the end of the data.
33957 There is no more data to be read.
33960 The request was malformed, or @var{annex} was invalid.
33963 The offset was invalid, or there was an error encountered reading the data.
33964 @var{nn} is a hex-encoded @code{errno} value.
33967 An empty reply indicates the @var{object} string was not recognized by
33968 the stub, or that the object does not support reading.
33971 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33972 @cindex write data into object, remote request
33973 @anchor{qXfer write}
33974 Write uninterpreted bytes into the target's special data area
33975 identified by the keyword @var{object}, starting at @var{offset} bytes
33976 into the data. @var{data}@dots{} is the binary-encoded data
33977 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33978 is specific to @var{object}; it can supply additional details about what data
33981 Here are the specific requests of this form defined so far. All
33982 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33983 formats, listed below.
33986 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33987 @anchor{qXfer siginfo write}
33988 Write @var{data} to the extra signal information on the target system.
33989 The annex part of the generic @samp{qXfer} packet must be
33990 empty (@pxref{qXfer write}).
33992 This packet is not probed by default; the remote stub must request it,
33993 by supplying an appropriate @samp{qSupported} response
33994 (@pxref{qSupported}).
33996 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33997 @anchor{qXfer spu write}
33998 Write @var{data} to an @code{spufs} file on the target system. The
33999 annex specifies which file to write; it must be of the form
34000 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34001 in the target process, and @var{name} identifes the @code{spufs} file
34002 in that context to be accessed.
34004 This packet is not probed by default; the remote stub must request it,
34005 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34011 @var{nn} (hex encoded) is the number of bytes written.
34012 This may be fewer bytes than supplied in the request.
34015 The request was malformed, or @var{annex} was invalid.
34018 The offset was invalid, or there was an error encountered writing the data.
34019 @var{nn} is a hex-encoded @code{errno} value.
34022 An empty reply indicates the @var{object} string was not
34023 recognized by the stub, or that the object does not support writing.
34026 @item qXfer:@var{object}:@var{operation}:@dots{}
34027 Requests of this form may be added in the future. When a stub does
34028 not recognize the @var{object} keyword, or its support for
34029 @var{object} does not recognize the @var{operation} keyword, the stub
34030 must respond with an empty packet.
34032 @item qAttached:@var{pid}
34033 @cindex query attached, remote request
34034 @cindex @samp{qAttached} packet
34035 Return an indication of whether the remote server attached to an
34036 existing process or created a new process. When the multiprocess
34037 protocol extensions are supported (@pxref{multiprocess extensions}),
34038 @var{pid} is an integer in hexadecimal format identifying the target
34039 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
34040 the query packet will be simplified as @samp{qAttached}.
34042 This query is used, for example, to know whether the remote process
34043 should be detached or killed when a @value{GDBN} session is ended with
34044 the @code{quit} command.
34049 The remote server attached to an existing process.
34051 The remote server created a new process.
34053 A badly formed request or an error was encountered.
34058 @node Architecture-Specific Protocol Details
34059 @section Architecture-Specific Protocol Details
34061 This section describes how the remote protocol is applied to specific
34062 target architectures. Also see @ref{Standard Target Features}, for
34063 details of XML target descriptions for each architecture.
34067 @subsubsection Breakpoint Kinds
34069 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
34074 16-bit Thumb mode breakpoint.
34077 32-bit Thumb mode (Thumb-2) breakpoint.
34080 32-bit ARM mode breakpoint.
34086 @subsubsection Register Packet Format
34088 The following @code{g}/@code{G} packets have previously been defined.
34089 In the below, some thirty-two bit registers are transferred as
34090 sixty-four bits. Those registers should be zero/sign extended (which?)
34091 to fill the space allocated. Register bytes are transferred in target
34092 byte order. The two nibbles within a register byte are transferred
34093 most-significant - least-significant.
34099 All registers are transferred as thirty-two bit quantities in the order:
34100 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34101 registers; fsr; fir; fp.
34105 All registers are transferred as sixty-four bit quantities (including
34106 thirty-two bit registers such as @code{sr}). The ordering is the same
34111 @node Tracepoint Packets
34112 @section Tracepoint Packets
34113 @cindex tracepoint packets
34114 @cindex packets, tracepoint
34116 Here we describe the packets @value{GDBN} uses to implement
34117 tracepoints (@pxref{Tracepoints}).
34121 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34122 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34123 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34124 the tracepoint is disabled. @var{step} is the tracepoint's step
34125 count, and @var{pass} is its pass count. If an @samp{F} is present,
34126 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34127 the number of bytes that the target should copy elsewhere to make room
34128 for the tracepoint. If an @samp{X} is present, it introduces a
34129 tracepoint condition, which consists of a hexadecimal length, followed
34130 by a comma and hex-encoded bytes, in a manner similar to action
34131 encodings as described below. If the trailing @samp{-} is present,
34132 further @samp{QTDP} packets will follow to specify this tracepoint's
34138 The packet was understood and carried out.
34140 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34142 The packet was not recognized.
34145 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34146 Define actions to be taken when a tracepoint is hit. @var{n} and
34147 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34148 this tracepoint. This packet may only be sent immediately after
34149 another @samp{QTDP} packet that ended with a @samp{-}. If the
34150 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34151 specifying more actions for this tracepoint.
34153 In the series of action packets for a given tracepoint, at most one
34154 can have an @samp{S} before its first @var{action}. If such a packet
34155 is sent, it and the following packets define ``while-stepping''
34156 actions. Any prior packets define ordinary actions --- that is, those
34157 taken when the tracepoint is first hit. If no action packet has an
34158 @samp{S}, then all the packets in the series specify ordinary
34159 tracepoint actions.
34161 The @samp{@var{action}@dots{}} portion of the packet is a series of
34162 actions, concatenated without separators. Each action has one of the
34168 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34169 a hexadecimal number whose @var{i}'th bit is set if register number
34170 @var{i} should be collected. (The least significant bit is numbered
34171 zero.) Note that @var{mask} may be any number of digits long; it may
34172 not fit in a 32-bit word.
34174 @item M @var{basereg},@var{offset},@var{len}
34175 Collect @var{len} bytes of memory starting at the address in register
34176 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34177 @samp{-1}, then the range has a fixed address: @var{offset} is the
34178 address of the lowest byte to collect. The @var{basereg},
34179 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34180 values (the @samp{-1} value for @var{basereg} is a special case).
34182 @item X @var{len},@var{expr}
34183 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34184 it directs. @var{expr} is an agent expression, as described in
34185 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34186 two-digit hex number in the packet; @var{len} is the number of bytes
34187 in the expression (and thus one-half the number of hex digits in the
34192 Any number of actions may be packed together in a single @samp{QTDP}
34193 packet, as long as the packet does not exceed the maximum packet
34194 length (400 bytes, for many stubs). There may be only one @samp{R}
34195 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34196 actions. Any registers referred to by @samp{M} and @samp{X} actions
34197 must be collected by a preceding @samp{R} action. (The
34198 ``while-stepping'' actions are treated as if they were attached to a
34199 separate tracepoint, as far as these restrictions are concerned.)
34204 The packet was understood and carried out.
34206 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34208 The packet was not recognized.
34211 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34212 @cindex @samp{QTDPsrc} packet
34213 Specify a source string of tracepoint @var{n} at address @var{addr}.
34214 This is useful to get accurate reproduction of the tracepoints
34215 originally downloaded at the beginning of the trace run. @var{type}
34216 is the name of the tracepoint part, such as @samp{cond} for the
34217 tracepoint's conditional expression (see below for a list of types), while
34218 @var{bytes} is the string, encoded in hexadecimal.
34220 @var{start} is the offset of the @var{bytes} within the overall source
34221 string, while @var{slen} is the total length of the source string.
34222 This is intended for handling source strings that are longer than will
34223 fit in a single packet.
34224 @c Add detailed example when this info is moved into a dedicated
34225 @c tracepoint descriptions section.
34227 The available string types are @samp{at} for the location,
34228 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34229 @value{GDBN} sends a separate packet for each command in the action
34230 list, in the same order in which the commands are stored in the list.
34232 The target does not need to do anything with source strings except
34233 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34236 Although this packet is optional, and @value{GDBN} will only send it
34237 if the target replies with @samp{TracepointSource} @xref{General
34238 Query Packets}, it makes both disconnected tracing and trace files
34239 much easier to use. Otherwise the user must be careful that the
34240 tracepoints in effect while looking at trace frames are identical to
34241 the ones in effect during the trace run; even a small discrepancy
34242 could cause @samp{tdump} not to work, or a particular trace frame not
34245 @item QTDV:@var{n}:@var{value}
34246 @cindex define trace state variable, remote request
34247 @cindex @samp{QTDV} packet
34248 Create a new trace state variable, number @var{n}, with an initial
34249 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34250 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34251 the option of not using this packet for initial values of zero; the
34252 target should simply create the trace state variables as they are
34253 mentioned in expressions.
34255 @item QTFrame:@var{n}
34256 Select the @var{n}'th tracepoint frame from the buffer, and use the
34257 register and memory contents recorded there to answer subsequent
34258 request packets from @value{GDBN}.
34260 A successful reply from the stub indicates that the stub has found the
34261 requested frame. The response is a series of parts, concatenated
34262 without separators, describing the frame we selected. Each part has
34263 one of the following forms:
34267 The selected frame is number @var{n} in the trace frame buffer;
34268 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34269 was no frame matching the criteria in the request packet.
34272 The selected trace frame records a hit of tracepoint number @var{t};
34273 @var{t} is a hexadecimal number.
34277 @item QTFrame:pc:@var{addr}
34278 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34279 currently selected frame whose PC is @var{addr};
34280 @var{addr} is a hexadecimal number.
34282 @item QTFrame:tdp:@var{t}
34283 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34284 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34285 is a hexadecimal number.
34287 @item QTFrame:range:@var{start}:@var{end}
34288 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34289 currently selected frame whose PC is between @var{start} (inclusive)
34290 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34293 @item QTFrame:outside:@var{start}:@var{end}
34294 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34295 frame @emph{outside} the given range of addresses (exclusive).
34298 Begin the tracepoint experiment. Begin collecting data from
34299 tracepoint hits in the trace frame buffer. This packet supports the
34300 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34301 instruction reply packet}).
34304 End the tracepoint experiment. Stop collecting trace frames.
34307 Clear the table of tracepoints, and empty the trace frame buffer.
34309 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34310 Establish the given ranges of memory as ``transparent''. The stub
34311 will answer requests for these ranges from memory's current contents,
34312 if they were not collected as part of the tracepoint hit.
34314 @value{GDBN} uses this to mark read-only regions of memory, like those
34315 containing program code. Since these areas never change, they should
34316 still have the same contents they did when the tracepoint was hit, so
34317 there's no reason for the stub to refuse to provide their contents.
34319 @item QTDisconnected:@var{value}
34320 Set the choice to what to do with the tracing run when @value{GDBN}
34321 disconnects from the target. A @var{value} of 1 directs the target to
34322 continue the tracing run, while 0 tells the target to stop tracing if
34323 @value{GDBN} is no longer in the picture.
34326 Ask the stub if there is a trace experiment running right now.
34328 The reply has the form:
34332 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34333 @var{running} is a single digit @code{1} if the trace is presently
34334 running, or @code{0} if not. It is followed by semicolon-separated
34335 optional fields that an agent may use to report additional status.
34339 If the trace is not running, the agent may report any of several
34340 explanations as one of the optional fields:
34345 No trace has been run yet.
34348 The trace was stopped by a user-originated stop command.
34351 The trace stopped because the trace buffer filled up.
34353 @item tdisconnected:0
34354 The trace stopped because @value{GDBN} disconnected from the target.
34356 @item tpasscount:@var{tpnum}
34357 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34359 @item terror:@var{text}:@var{tpnum}
34360 The trace stopped because tracepoint @var{tpnum} had an error. The
34361 string @var{text} is available to describe the nature of the error
34362 (for instance, a divide by zero in the condition expression).
34363 @var{text} is hex encoded.
34366 The trace stopped for some other reason.
34370 Additional optional fields supply statistical and other information.
34371 Although not required, they are extremely useful for users monitoring
34372 the progress of a trace run. If a trace has stopped, and these
34373 numbers are reported, they must reflect the state of the just-stopped
34378 @item tframes:@var{n}
34379 The number of trace frames in the buffer.
34381 @item tcreated:@var{n}
34382 The total number of trace frames created during the run. This may
34383 be larger than the trace frame count, if the buffer is circular.
34385 @item tsize:@var{n}
34386 The total size of the trace buffer, in bytes.
34388 @item tfree:@var{n}
34389 The number of bytes still unused in the buffer.
34391 @item circular:@var{n}
34392 The value of the circular trace buffer flag. @code{1} means that the
34393 trace buffer is circular and old trace frames will be discarded if
34394 necessary to make room, @code{0} means that the trace buffer is linear
34397 @item disconn:@var{n}
34398 The value of the disconnected tracing flag. @code{1} means that
34399 tracing will continue after @value{GDBN} disconnects, @code{0} means
34400 that the trace run will stop.
34404 @item qTV:@var{var}
34405 @cindex trace state variable value, remote request
34406 @cindex @samp{qTV} packet
34407 Ask the stub for the value of the trace state variable number @var{var}.
34412 The value of the variable is @var{value}. This will be the current
34413 value of the variable if the user is examining a running target, or a
34414 saved value if the variable was collected in the trace frame that the
34415 user is looking at. Note that multiple requests may result in
34416 different reply values, such as when requesting values while the
34417 program is running.
34420 The value of the variable is unknown. This would occur, for example,
34421 if the user is examining a trace frame in which the requested variable
34427 These packets request data about tracepoints that are being used by
34428 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34429 of data, and multiple @code{qTsP} to get additional pieces. Replies
34430 to these packets generally take the form of the @code{QTDP} packets
34431 that define tracepoints. (FIXME add detailed syntax)
34435 These packets request data about trace state variables that are on the
34436 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34437 and multiple @code{qTsV} to get additional variables. Replies to
34438 these packets follow the syntax of the @code{QTDV} packets that define
34439 trace state variables.
34443 These packets request data about static tracepoint markers that exist
34444 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34445 first piece of data, and multiple @code{qTsSTM} to get additional
34446 pieces. Replies to these packets take the following form:
34450 @item m @var{address}:@var{id}:@var{extra}
34452 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34453 a comma-separated list of markers
34455 (lower case letter @samp{L}) denotes end of list.
34457 An error occurred. @var{nn} are hex digits.
34459 An empty reply indicates that the request is not supported by the
34463 @var{address} is encoded in hex.
34464 @var{id} and @var{extra} are strings encoded in hex.
34466 In response to each query, the target will reply with a list of one or
34467 more markers, separated by commas. @value{GDBN} will respond to each
34468 reply with a request for more markers (using the @samp{qs} form of the
34469 query), until the target responds with @samp{l} (lower-case ell, for
34472 @item qTSTMat:@var{address}
34473 This packets requests data about static tracepoint markers in the
34474 target program at @var{address}. Replies to this packet follow the
34475 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34476 tracepoint markers.
34478 @item QTSave:@var{filename}
34479 This packet directs the target to save trace data to the file name
34480 @var{filename} in the target's filesystem. @var{filename} is encoded
34481 as a hex string; the interpretation of the file name (relative vs
34482 absolute, wild cards, etc) is up to the target.
34484 @item qTBuffer:@var{offset},@var{len}
34485 Return up to @var{len} bytes of the current contents of trace buffer,
34486 starting at @var{offset}. The trace buffer is treated as if it were
34487 a contiguous collection of traceframes, as per the trace file format.
34488 The reply consists as many hex-encoded bytes as the target can deliver
34489 in a packet; it is not an error to return fewer than were asked for.
34490 A reply consisting of just @code{l} indicates that no bytes are
34493 @item QTBuffer:circular:@var{value}
34494 This packet directs the target to use a circular trace buffer if
34495 @var{value} is 1, or a linear buffer if the value is 0.
34499 @subsection Relocate instruction reply packet
34500 When installing fast tracepoints in memory, the target may need to
34501 relocate the instruction currently at the tracepoint address to a
34502 different address in memory. For most instructions, a simple copy is
34503 enough, but, for example, call instructions that implicitly push the
34504 return address on the stack, and relative branches or other
34505 PC-relative instructions require offset adjustment, so that the effect
34506 of executing the instruction at a different address is the same as if
34507 it had executed in the original location.
34509 In response to several of the tracepoint packets, the target may also
34510 respond with a number of intermediate @samp{qRelocInsn} request
34511 packets before the final result packet, to have @value{GDBN} handle
34512 this relocation operation. If a packet supports this mechanism, its
34513 documentation will explicitly say so. See for example the above
34514 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34515 format of the request is:
34518 @item qRelocInsn:@var{from};@var{to}
34520 This requests @value{GDBN} to copy instruction at address @var{from}
34521 to address @var{to}, possibly adjusted so that executing the
34522 instruction at @var{to} has the same effect as executing it at
34523 @var{from}. @value{GDBN} writes the adjusted instruction to target
34524 memory starting at @var{to}.
34529 @item qRelocInsn:@var{adjusted_size}
34530 Informs the stub the relocation is complete. @var{adjusted_size} is
34531 the length in bytes of resulting relocated instruction sequence.
34533 A badly formed request was detected, or an error was encountered while
34534 relocating the instruction.
34537 @node Host I/O Packets
34538 @section Host I/O Packets
34539 @cindex Host I/O, remote protocol
34540 @cindex file transfer, remote protocol
34542 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34543 operations on the far side of a remote link. For example, Host I/O is
34544 used to upload and download files to a remote target with its own
34545 filesystem. Host I/O uses the same constant values and data structure
34546 layout as the target-initiated File-I/O protocol. However, the
34547 Host I/O packets are structured differently. The target-initiated
34548 protocol relies on target memory to store parameters and buffers.
34549 Host I/O requests are initiated by @value{GDBN}, and the
34550 target's memory is not involved. @xref{File-I/O Remote Protocol
34551 Extension}, for more details on the target-initiated protocol.
34553 The Host I/O request packets all encode a single operation along with
34554 its arguments. They have this format:
34558 @item vFile:@var{operation}: @var{parameter}@dots{}
34559 @var{operation} is the name of the particular request; the target
34560 should compare the entire packet name up to the second colon when checking
34561 for a supported operation. The format of @var{parameter} depends on
34562 the operation. Numbers are always passed in hexadecimal. Negative
34563 numbers have an explicit minus sign (i.e.@: two's complement is not
34564 used). Strings (e.g.@: filenames) are encoded as a series of
34565 hexadecimal bytes. The last argument to a system call may be a
34566 buffer of escaped binary data (@pxref{Binary Data}).
34570 The valid responses to Host I/O packets are:
34574 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34575 @var{result} is the integer value returned by this operation, usually
34576 non-negative for success and -1 for errors. If an error has occured,
34577 @var{errno} will be included in the result. @var{errno} will have a
34578 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34579 operations which return data, @var{attachment} supplies the data as a
34580 binary buffer. Binary buffers in response packets are escaped in the
34581 normal way (@pxref{Binary Data}). See the individual packet
34582 documentation for the interpretation of @var{result} and
34586 An empty response indicates that this operation is not recognized.
34590 These are the supported Host I/O operations:
34593 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34594 Open a file at @var{pathname} and return a file descriptor for it, or
34595 return -1 if an error occurs. @var{pathname} is a string,
34596 @var{flags} is an integer indicating a mask of open flags
34597 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34598 of mode bits to use if the file is created (@pxref{mode_t Values}).
34599 @xref{open}, for details of the open flags and mode values.
34601 @item vFile:close: @var{fd}
34602 Close the open file corresponding to @var{fd} and return 0, or
34603 -1 if an error occurs.
34605 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34606 Read data from the open file corresponding to @var{fd}. Up to
34607 @var{count} bytes will be read from the file, starting at @var{offset}
34608 relative to the start of the file. The target may read fewer bytes;
34609 common reasons include packet size limits and an end-of-file
34610 condition. The number of bytes read is returned. Zero should only be
34611 returned for a successful read at the end of the file, or if
34612 @var{count} was zero.
34614 The data read should be returned as a binary attachment on success.
34615 If zero bytes were read, the response should include an empty binary
34616 attachment (i.e.@: a trailing semicolon). The return value is the
34617 number of target bytes read; the binary attachment may be longer if
34618 some characters were escaped.
34620 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34621 Write @var{data} (a binary buffer) to the open file corresponding
34622 to @var{fd}. Start the write at @var{offset} from the start of the
34623 file. Unlike many @code{write} system calls, there is no
34624 separate @var{count} argument; the length of @var{data} in the
34625 packet is used. @samp{vFile:write} returns the number of bytes written,
34626 which may be shorter than the length of @var{data}, or -1 if an
34629 @item vFile:unlink: @var{pathname}
34630 Delete the file at @var{pathname} on the target. Return 0,
34631 or -1 if an error occurs. @var{pathname} is a string.
34636 @section Interrupts
34637 @cindex interrupts (remote protocol)
34639 When a program on the remote target is running, @value{GDBN} may
34640 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34641 a @code{BREAK} followed by @code{g},
34642 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34644 The precise meaning of @code{BREAK} is defined by the transport
34645 mechanism and may, in fact, be undefined. @value{GDBN} does not
34646 currently define a @code{BREAK} mechanism for any of the network
34647 interfaces except for TCP, in which case @value{GDBN} sends the
34648 @code{telnet} BREAK sequence.
34650 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34651 transport mechanisms. It is represented by sending the single byte
34652 @code{0x03} without any of the usual packet overhead described in
34653 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34654 transmitted as part of a packet, it is considered to be packet data
34655 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34656 (@pxref{X packet}), used for binary downloads, may include an unescaped
34657 @code{0x03} as part of its packet.
34659 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34660 When Linux kernel receives this sequence from serial port,
34661 it stops execution and connects to gdb.
34663 Stubs are not required to recognize these interrupt mechanisms and the
34664 precise meaning associated with receipt of the interrupt is
34665 implementation defined. If the target supports debugging of multiple
34666 threads and/or processes, it should attempt to interrupt all
34667 currently-executing threads and processes.
34668 If the stub is successful at interrupting the
34669 running program, it should send one of the stop
34670 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34671 of successfully stopping the program in all-stop mode, and a stop reply
34672 for each stopped thread in non-stop mode.
34673 Interrupts received while the
34674 program is stopped are discarded.
34676 @node Notification Packets
34677 @section Notification Packets
34678 @cindex notification packets
34679 @cindex packets, notification
34681 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34682 packets that require no acknowledgment. Both the GDB and the stub
34683 may send notifications (although the only notifications defined at
34684 present are sent by the stub). Notifications carry information
34685 without incurring the round-trip latency of an acknowledgment, and so
34686 are useful for low-impact communications where occasional packet loss
34689 A notification packet has the form @samp{% @var{data} #
34690 @var{checksum}}, where @var{data} is the content of the notification,
34691 and @var{checksum} is a checksum of @var{data}, computed and formatted
34692 as for ordinary @value{GDBN} packets. A notification's @var{data}
34693 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34694 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34695 to acknowledge the notification's receipt or to report its corruption.
34697 Every notification's @var{data} begins with a name, which contains no
34698 colon characters, followed by a colon character.
34700 Recipients should silently ignore corrupted notifications and
34701 notifications they do not understand. Recipients should restart
34702 timeout periods on receipt of a well-formed notification, whether or
34703 not they understand it.
34705 Senders should only send the notifications described here when this
34706 protocol description specifies that they are permitted. In the
34707 future, we may extend the protocol to permit existing notifications in
34708 new contexts; this rule helps older senders avoid confusing newer
34711 (Older versions of @value{GDBN} ignore bytes received until they see
34712 the @samp{$} byte that begins an ordinary packet, so new stubs may
34713 transmit notifications without fear of confusing older clients. There
34714 are no notifications defined for @value{GDBN} to send at the moment, but we
34715 assume that most older stubs would ignore them, as well.)
34717 The following notification packets from the stub to @value{GDBN} are
34721 @item Stop: @var{reply}
34722 Report an asynchronous stop event in non-stop mode.
34723 The @var{reply} has the form of a stop reply, as
34724 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34725 for information on how these notifications are acknowledged by
34729 @node Remote Non-Stop
34730 @section Remote Protocol Support for Non-Stop Mode
34732 @value{GDBN}'s remote protocol supports non-stop debugging of
34733 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34734 supports non-stop mode, it should report that to @value{GDBN} by including
34735 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34737 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34738 establishing a new connection with the stub. Entering non-stop mode
34739 does not alter the state of any currently-running threads, but targets
34740 must stop all threads in any already-attached processes when entering
34741 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34742 probe the target state after a mode change.
34744 In non-stop mode, when an attached process encounters an event that
34745 would otherwise be reported with a stop reply, it uses the
34746 asynchronous notification mechanism (@pxref{Notification Packets}) to
34747 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34748 in all processes are stopped when a stop reply is sent, in non-stop
34749 mode only the thread reporting the stop event is stopped. That is,
34750 when reporting a @samp{S} or @samp{T} response to indicate completion
34751 of a step operation, hitting a breakpoint, or a fault, only the
34752 affected thread is stopped; any other still-running threads continue
34753 to run. When reporting a @samp{W} or @samp{X} response, all running
34754 threads belonging to other attached processes continue to run.
34756 Only one stop reply notification at a time may be pending; if
34757 additional stop events occur before @value{GDBN} has acknowledged the
34758 previous notification, they must be queued by the stub for later
34759 synchronous transmission in response to @samp{vStopped} packets from
34760 @value{GDBN}. Because the notification mechanism is unreliable,
34761 the stub is permitted to resend a stop reply notification
34762 if it believes @value{GDBN} may not have received it. @value{GDBN}
34763 ignores additional stop reply notifications received before it has
34764 finished processing a previous notification and the stub has completed
34765 sending any queued stop events.
34767 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34768 notification at any time. Specifically, they may appear when
34769 @value{GDBN} is not otherwise reading input from the stub, or when
34770 @value{GDBN} is expecting to read a normal synchronous response or a
34771 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34772 Notification packets are distinct from any other communication from
34773 the stub so there is no ambiguity.
34775 After receiving a stop reply notification, @value{GDBN} shall
34776 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34777 as a regular, synchronous request to the stub. Such acknowledgment
34778 is not required to happen immediately, as @value{GDBN} is permitted to
34779 send other, unrelated packets to the stub first, which the stub should
34782 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34783 stop events to report to @value{GDBN}, it shall respond by sending a
34784 normal stop reply response. @value{GDBN} shall then send another
34785 @samp{vStopped} packet to solicit further responses; again, it is
34786 permitted to send other, unrelated packets as well which the stub
34787 should process normally.
34789 If the stub receives a @samp{vStopped} packet and there are no
34790 additional stop events to report, the stub shall return an @samp{OK}
34791 response. At this point, if further stop events occur, the stub shall
34792 send a new stop reply notification, @value{GDBN} shall accept the
34793 notification, and the process shall be repeated.
34795 In non-stop mode, the target shall respond to the @samp{?} packet as
34796 follows. First, any incomplete stop reply notification/@samp{vStopped}
34797 sequence in progress is abandoned. The target must begin a new
34798 sequence reporting stop events for all stopped threads, whether or not
34799 it has previously reported those events to @value{GDBN}. The first
34800 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34801 subsequent stop replies are sent as responses to @samp{vStopped} packets
34802 using the mechanism described above. The target must not send
34803 asynchronous stop reply notifications until the sequence is complete.
34804 If all threads are running when the target receives the @samp{?} packet,
34805 or if the target is not attached to any process, it shall respond
34808 @node Packet Acknowledgment
34809 @section Packet Acknowledgment
34811 @cindex acknowledgment, for @value{GDBN} remote
34812 @cindex packet acknowledgment, for @value{GDBN} remote
34813 By default, when either the host or the target machine receives a packet,
34814 the first response expected is an acknowledgment: either @samp{+} (to indicate
34815 the package was received correctly) or @samp{-} (to request retransmission).
34816 This mechanism allows the @value{GDBN} remote protocol to operate over
34817 unreliable transport mechanisms, such as a serial line.
34819 In cases where the transport mechanism is itself reliable (such as a pipe or
34820 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34821 It may be desirable to disable them in that case to reduce communication
34822 overhead, or for other reasons. This can be accomplished by means of the
34823 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34825 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34826 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34827 and response format still includes the normal checksum, as described in
34828 @ref{Overview}, but the checksum may be ignored by the receiver.
34830 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34831 no-acknowledgment mode, it should report that to @value{GDBN}
34832 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34833 @pxref{qSupported}.
34834 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34835 disabled via the @code{set remote noack-packet off} command
34836 (@pxref{Remote Configuration}),
34837 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34838 Only then may the stub actually turn off packet acknowledgments.
34839 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34840 response, which can be safely ignored by the stub.
34842 Note that @code{set remote noack-packet} command only affects negotiation
34843 between @value{GDBN} and the stub when subsequent connections are made;
34844 it does not affect the protocol acknowledgment state for any current
34846 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34847 new connection is established,
34848 there is also no protocol request to re-enable the acknowledgments
34849 for the current connection, once disabled.
34854 Example sequence of a target being re-started. Notice how the restart
34855 does not get any direct output:
34860 @emph{target restarts}
34863 <- @code{T001:1234123412341234}
34867 Example sequence of a target being stepped by a single instruction:
34870 -> @code{G1445@dots{}}
34875 <- @code{T001:1234123412341234}
34879 <- @code{1455@dots{}}
34883 @node File-I/O Remote Protocol Extension
34884 @section File-I/O Remote Protocol Extension
34885 @cindex File-I/O remote protocol extension
34888 * File-I/O Overview::
34889 * Protocol Basics::
34890 * The F Request Packet::
34891 * The F Reply Packet::
34892 * The Ctrl-C Message::
34894 * List of Supported Calls::
34895 * Protocol-specific Representation of Datatypes::
34897 * File-I/O Examples::
34900 @node File-I/O Overview
34901 @subsection File-I/O Overview
34902 @cindex file-i/o overview
34904 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34905 target to use the host's file system and console I/O to perform various
34906 system calls. System calls on the target system are translated into a
34907 remote protocol packet to the host system, which then performs the needed
34908 actions and returns a response packet to the target system.
34909 This simulates file system operations even on targets that lack file systems.
34911 The protocol is defined to be independent of both the host and target systems.
34912 It uses its own internal representation of datatypes and values. Both
34913 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34914 translating the system-dependent value representations into the internal
34915 protocol representations when data is transmitted.
34917 The communication is synchronous. A system call is possible only when
34918 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34919 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34920 the target is stopped to allow deterministic access to the target's
34921 memory. Therefore File-I/O is not interruptible by target signals. On
34922 the other hand, it is possible to interrupt File-I/O by a user interrupt
34923 (@samp{Ctrl-C}) within @value{GDBN}.
34925 The target's request to perform a host system call does not finish
34926 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34927 after finishing the system call, the target returns to continuing the
34928 previous activity (continue, step). No additional continue or step
34929 request from @value{GDBN} is required.
34932 (@value{GDBP}) continue
34933 <- target requests 'system call X'
34934 target is stopped, @value{GDBN} executes system call
34935 -> @value{GDBN} returns result
34936 ... target continues, @value{GDBN} returns to wait for the target
34937 <- target hits breakpoint and sends a Txx packet
34940 The protocol only supports I/O on the console and to regular files on
34941 the host file system. Character or block special devices, pipes,
34942 named pipes, sockets or any other communication method on the host
34943 system are not supported by this protocol.
34945 File I/O is not supported in non-stop mode.
34947 @node Protocol Basics
34948 @subsection Protocol Basics
34949 @cindex protocol basics, file-i/o
34951 The File-I/O protocol uses the @code{F} packet as the request as well
34952 as reply packet. Since a File-I/O system call can only occur when
34953 @value{GDBN} is waiting for a response from the continuing or stepping target,
34954 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34955 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34956 This @code{F} packet contains all information needed to allow @value{GDBN}
34957 to call the appropriate host system call:
34961 A unique identifier for the requested system call.
34964 All parameters to the system call. Pointers are given as addresses
34965 in the target memory address space. Pointers to strings are given as
34966 pointer/length pair. Numerical values are given as they are.
34967 Numerical control flags are given in a protocol-specific representation.
34971 At this point, @value{GDBN} has to perform the following actions.
34975 If the parameters include pointer values to data needed as input to a
34976 system call, @value{GDBN} requests this data from the target with a
34977 standard @code{m} packet request. This additional communication has to be
34978 expected by the target implementation and is handled as any other @code{m}
34982 @value{GDBN} translates all value from protocol representation to host
34983 representation as needed. Datatypes are coerced into the host types.
34986 @value{GDBN} calls the system call.
34989 It then coerces datatypes back to protocol representation.
34992 If the system call is expected to return data in buffer space specified
34993 by pointer parameters to the call, the data is transmitted to the
34994 target using a @code{M} or @code{X} packet. This packet has to be expected
34995 by the target implementation and is handled as any other @code{M} or @code{X}
35000 Eventually @value{GDBN} replies with another @code{F} packet which contains all
35001 necessary information for the target to continue. This at least contains
35008 @code{errno}, if has been changed by the system call.
35015 After having done the needed type and value coercion, the target continues
35016 the latest continue or step action.
35018 @node The F Request Packet
35019 @subsection The @code{F} Request Packet
35020 @cindex file-i/o request packet
35021 @cindex @code{F} request packet
35023 The @code{F} request packet has the following format:
35026 @item F@var{call-id},@var{parameter@dots{}}
35028 @var{call-id} is the identifier to indicate the host system call to be called.
35029 This is just the name of the function.
35031 @var{parameter@dots{}} are the parameters to the system call.
35032 Parameters are hexadecimal integer values, either the actual values in case
35033 of scalar datatypes, pointers to target buffer space in case of compound
35034 datatypes and unspecified memory areas, or pointer/length pairs in case
35035 of string parameters. These are appended to the @var{call-id} as a
35036 comma-delimited list. All values are transmitted in ASCII
35037 string representation, pointer/length pairs separated by a slash.
35043 @node The F Reply Packet
35044 @subsection The @code{F} Reply Packet
35045 @cindex file-i/o reply packet
35046 @cindex @code{F} reply packet
35048 The @code{F} reply packet has the following format:
35052 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
35054 @var{retcode} is the return code of the system call as hexadecimal value.
35056 @var{errno} is the @code{errno} set by the call, in protocol-specific
35058 This parameter can be omitted if the call was successful.
35060 @var{Ctrl-C flag} is only sent if the user requested a break. In this
35061 case, @var{errno} must be sent as well, even if the call was successful.
35062 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
35069 or, if the call was interrupted before the host call has been performed:
35076 assuming 4 is the protocol-specific representation of @code{EINTR}.
35081 @node The Ctrl-C Message
35082 @subsection The @samp{Ctrl-C} Message
35083 @cindex ctrl-c message, in file-i/o protocol
35085 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35086 reply packet (@pxref{The F Reply Packet}),
35087 the target should behave as if it had
35088 gotten a break message. The meaning for the target is ``system call
35089 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35090 (as with a break message) and return to @value{GDBN} with a @code{T02}
35093 It's important for the target to know in which
35094 state the system call was interrupted. There are two possible cases:
35098 The system call hasn't been performed on the host yet.
35101 The system call on the host has been finished.
35105 These two states can be distinguished by the target by the value of the
35106 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35107 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35108 on POSIX systems. In any other case, the target may presume that the
35109 system call has been finished --- successfully or not --- and should behave
35110 as if the break message arrived right after the system call.
35112 @value{GDBN} must behave reliably. If the system call has not been called
35113 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35114 @code{errno} in the packet. If the system call on the host has been finished
35115 before the user requests a break, the full action must be finished by
35116 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35117 The @code{F} packet may only be sent when either nothing has happened
35118 or the full action has been completed.
35121 @subsection Console I/O
35122 @cindex console i/o as part of file-i/o
35124 By default and if not explicitly closed by the target system, the file
35125 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35126 on the @value{GDBN} console is handled as any other file output operation
35127 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35128 by @value{GDBN} so that after the target read request from file descriptor
35129 0 all following typing is buffered until either one of the following
35134 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35136 system call is treated as finished.
35139 The user presses @key{RET}. This is treated as end of input with a trailing
35143 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35144 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35148 If the user has typed more characters than fit in the buffer given to
35149 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35150 either another @code{read(0, @dots{})} is requested by the target, or debugging
35151 is stopped at the user's request.
35154 @node List of Supported Calls
35155 @subsection List of Supported Calls
35156 @cindex list of supported file-i/o calls
35173 @unnumberedsubsubsec open
35174 @cindex open, file-i/o system call
35179 int open(const char *pathname, int flags);
35180 int open(const char *pathname, int flags, mode_t mode);
35184 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35187 @var{flags} is the bitwise @code{OR} of the following values:
35191 If the file does not exist it will be created. The host
35192 rules apply as far as file ownership and time stamps
35196 When used with @code{O_CREAT}, if the file already exists it is
35197 an error and open() fails.
35200 If the file already exists and the open mode allows
35201 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35202 truncated to zero length.
35205 The file is opened in append mode.
35208 The file is opened for reading only.
35211 The file is opened for writing only.
35214 The file is opened for reading and writing.
35218 Other bits are silently ignored.
35222 @var{mode} is the bitwise @code{OR} of the following values:
35226 User has read permission.
35229 User has write permission.
35232 Group has read permission.
35235 Group has write permission.
35238 Others have read permission.
35241 Others have write permission.
35245 Other bits are silently ignored.
35248 @item Return value:
35249 @code{open} returns the new file descriptor or -1 if an error
35256 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35259 @var{pathname} refers to a directory.
35262 The requested access is not allowed.
35265 @var{pathname} was too long.
35268 A directory component in @var{pathname} does not exist.
35271 @var{pathname} refers to a device, pipe, named pipe or socket.
35274 @var{pathname} refers to a file on a read-only filesystem and
35275 write access was requested.
35278 @var{pathname} is an invalid pointer value.
35281 No space on device to create the file.
35284 The process already has the maximum number of files open.
35287 The limit on the total number of files open on the system
35291 The call was interrupted by the user.
35297 @unnumberedsubsubsec close
35298 @cindex close, file-i/o system call
35307 @samp{Fclose,@var{fd}}
35309 @item Return value:
35310 @code{close} returns zero on success, or -1 if an error occurred.
35316 @var{fd} isn't a valid open file descriptor.
35319 The call was interrupted by the user.
35325 @unnumberedsubsubsec read
35326 @cindex read, file-i/o system call
35331 int read(int fd, void *buf, unsigned int count);
35335 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35337 @item Return value:
35338 On success, the number of bytes read is returned.
35339 Zero indicates end of file. If count is zero, read
35340 returns zero as well. On error, -1 is returned.
35346 @var{fd} is not a valid file descriptor or is not open for
35350 @var{bufptr} is an invalid pointer value.
35353 The call was interrupted by the user.
35359 @unnumberedsubsubsec write
35360 @cindex write, file-i/o system call
35365 int write(int fd, const void *buf, unsigned int count);
35369 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35371 @item Return value:
35372 On success, the number of bytes written are returned.
35373 Zero indicates nothing was written. On error, -1
35380 @var{fd} is not a valid file descriptor or is not open for
35384 @var{bufptr} is an invalid pointer value.
35387 An attempt was made to write a file that exceeds the
35388 host-specific maximum file size allowed.
35391 No space on device to write the data.
35394 The call was interrupted by the user.
35400 @unnumberedsubsubsec lseek
35401 @cindex lseek, file-i/o system call
35406 long lseek (int fd, long offset, int flag);
35410 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35412 @var{flag} is one of:
35416 The offset is set to @var{offset} bytes.
35419 The offset is set to its current location plus @var{offset}
35423 The offset is set to the size of the file plus @var{offset}
35427 @item Return value:
35428 On success, the resulting unsigned offset in bytes from
35429 the beginning of the file is returned. Otherwise, a
35430 value of -1 is returned.
35436 @var{fd} is not a valid open file descriptor.
35439 @var{fd} is associated with the @value{GDBN} console.
35442 @var{flag} is not a proper value.
35445 The call was interrupted by the user.
35451 @unnumberedsubsubsec rename
35452 @cindex rename, file-i/o system call
35457 int rename(const char *oldpath, const char *newpath);
35461 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35463 @item Return value:
35464 On success, zero is returned. On error, -1 is returned.
35470 @var{newpath} is an existing directory, but @var{oldpath} is not a
35474 @var{newpath} is a non-empty directory.
35477 @var{oldpath} or @var{newpath} is a directory that is in use by some
35481 An attempt was made to make a directory a subdirectory
35485 A component used as a directory in @var{oldpath} or new
35486 path is not a directory. Or @var{oldpath} is a directory
35487 and @var{newpath} exists but is not a directory.
35490 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35493 No access to the file or the path of the file.
35497 @var{oldpath} or @var{newpath} was too long.
35500 A directory component in @var{oldpath} or @var{newpath} does not exist.
35503 The file is on a read-only filesystem.
35506 The device containing the file has no room for the new
35510 The call was interrupted by the user.
35516 @unnumberedsubsubsec unlink
35517 @cindex unlink, file-i/o system call
35522 int unlink(const char *pathname);
35526 @samp{Funlink,@var{pathnameptr}/@var{len}}
35528 @item Return value:
35529 On success, zero is returned. On error, -1 is returned.
35535 No access to the file or the path of the file.
35538 The system does not allow unlinking of directories.
35541 The file @var{pathname} cannot be unlinked because it's
35542 being used by another process.
35545 @var{pathnameptr} is an invalid pointer value.
35548 @var{pathname} was too long.
35551 A directory component in @var{pathname} does not exist.
35554 A component of the path is not a directory.
35557 The file is on a read-only filesystem.
35560 The call was interrupted by the user.
35566 @unnumberedsubsubsec stat/fstat
35567 @cindex fstat, file-i/o system call
35568 @cindex stat, file-i/o system call
35573 int stat(const char *pathname, struct stat *buf);
35574 int fstat(int fd, struct stat *buf);
35578 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35579 @samp{Ffstat,@var{fd},@var{bufptr}}
35581 @item Return value:
35582 On success, zero is returned. On error, -1 is returned.
35588 @var{fd} is not a valid open file.
35591 A directory component in @var{pathname} does not exist or the
35592 path is an empty string.
35595 A component of the path is not a directory.
35598 @var{pathnameptr} is an invalid pointer value.
35601 No access to the file or the path of the file.
35604 @var{pathname} was too long.
35607 The call was interrupted by the user.
35613 @unnumberedsubsubsec gettimeofday
35614 @cindex gettimeofday, file-i/o system call
35619 int gettimeofday(struct timeval *tv, void *tz);
35623 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35625 @item Return value:
35626 On success, 0 is returned, -1 otherwise.
35632 @var{tz} is a non-NULL pointer.
35635 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35641 @unnumberedsubsubsec isatty
35642 @cindex isatty, file-i/o system call
35647 int isatty(int fd);
35651 @samp{Fisatty,@var{fd}}
35653 @item Return value:
35654 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35660 The call was interrupted by the user.
35665 Note that the @code{isatty} call is treated as a special case: it returns
35666 1 to the target if the file descriptor is attached
35667 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35668 would require implementing @code{ioctl} and would be more complex than
35673 @unnumberedsubsubsec system
35674 @cindex system, file-i/o system call
35679 int system(const char *command);
35683 @samp{Fsystem,@var{commandptr}/@var{len}}
35685 @item Return value:
35686 If @var{len} is zero, the return value indicates whether a shell is
35687 available. A zero return value indicates a shell is not available.
35688 For non-zero @var{len}, the value returned is -1 on error and the
35689 return status of the command otherwise. Only the exit status of the
35690 command is returned, which is extracted from the host's @code{system}
35691 return value by calling @code{WEXITSTATUS(retval)}. In case
35692 @file{/bin/sh} could not be executed, 127 is returned.
35698 The call was interrupted by the user.
35703 @value{GDBN} takes over the full task of calling the necessary host calls
35704 to perform the @code{system} call. The return value of @code{system} on
35705 the host is simplified before it's returned
35706 to the target. Any termination signal information from the child process
35707 is discarded, and the return value consists
35708 entirely of the exit status of the called command.
35710 Due to security concerns, the @code{system} call is by default refused
35711 by @value{GDBN}. The user has to allow this call explicitly with the
35712 @code{set remote system-call-allowed 1} command.
35715 @item set remote system-call-allowed
35716 @kindex set remote system-call-allowed
35717 Control whether to allow the @code{system} calls in the File I/O
35718 protocol for the remote target. The default is zero (disabled).
35720 @item show remote system-call-allowed
35721 @kindex show remote system-call-allowed
35722 Show whether the @code{system} calls are allowed in the File I/O
35726 @node Protocol-specific Representation of Datatypes
35727 @subsection Protocol-specific Representation of Datatypes
35728 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35731 * Integral Datatypes::
35733 * Memory Transfer::
35738 @node Integral Datatypes
35739 @unnumberedsubsubsec Integral Datatypes
35740 @cindex integral datatypes, in file-i/o protocol
35742 The integral datatypes used in the system calls are @code{int},
35743 @code{unsigned int}, @code{long}, @code{unsigned long},
35744 @code{mode_t}, and @code{time_t}.
35746 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35747 implemented as 32 bit values in this protocol.
35749 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35751 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35752 in @file{limits.h}) to allow range checking on host and target.
35754 @code{time_t} datatypes are defined as seconds since the Epoch.
35756 All integral datatypes transferred as part of a memory read or write of a
35757 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35760 @node Pointer Values
35761 @unnumberedsubsubsec Pointer Values
35762 @cindex pointer values, in file-i/o protocol
35764 Pointers to target data are transmitted as they are. An exception
35765 is made for pointers to buffers for which the length isn't
35766 transmitted as part of the function call, namely strings. Strings
35767 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35774 which is a pointer to data of length 18 bytes at position 0x1aaf.
35775 The length is defined as the full string length in bytes, including
35776 the trailing null byte. For example, the string @code{"hello world"}
35777 at address 0x123456 is transmitted as
35783 @node Memory Transfer
35784 @unnumberedsubsubsec Memory Transfer
35785 @cindex memory transfer, in file-i/o protocol
35787 Structured data which is transferred using a memory read or write (for
35788 example, a @code{struct stat}) is expected to be in a protocol-specific format
35789 with all scalar multibyte datatypes being big endian. Translation to
35790 this representation needs to be done both by the target before the @code{F}
35791 packet is sent, and by @value{GDBN} before
35792 it transfers memory to the target. Transferred pointers to structured
35793 data should point to the already-coerced data at any time.
35797 @unnumberedsubsubsec struct stat
35798 @cindex struct stat, in file-i/o protocol
35800 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35801 is defined as follows:
35805 unsigned int st_dev; /* device */
35806 unsigned int st_ino; /* inode */
35807 mode_t st_mode; /* protection */
35808 unsigned int st_nlink; /* number of hard links */
35809 unsigned int st_uid; /* user ID of owner */
35810 unsigned int st_gid; /* group ID of owner */
35811 unsigned int st_rdev; /* device type (if inode device) */
35812 unsigned long st_size; /* total size, in bytes */
35813 unsigned long st_blksize; /* blocksize for filesystem I/O */
35814 unsigned long st_blocks; /* number of blocks allocated */
35815 time_t st_atime; /* time of last access */
35816 time_t st_mtime; /* time of last modification */
35817 time_t st_ctime; /* time of last change */
35821 The integral datatypes conform to the definitions given in the
35822 appropriate section (see @ref{Integral Datatypes}, for details) so this
35823 structure is of size 64 bytes.
35825 The values of several fields have a restricted meaning and/or
35831 A value of 0 represents a file, 1 the console.
35834 No valid meaning for the target. Transmitted unchanged.
35837 Valid mode bits are described in @ref{Constants}. Any other
35838 bits have currently no meaning for the target.
35843 No valid meaning for the target. Transmitted unchanged.
35848 These values have a host and file system dependent
35849 accuracy. Especially on Windows hosts, the file system may not
35850 support exact timing values.
35853 The target gets a @code{struct stat} of the above representation and is
35854 responsible for coercing it to the target representation before
35857 Note that due to size differences between the host, target, and protocol
35858 representations of @code{struct stat} members, these members could eventually
35859 get truncated on the target.
35861 @node struct timeval
35862 @unnumberedsubsubsec struct timeval
35863 @cindex struct timeval, in file-i/o protocol
35865 The buffer of type @code{struct timeval} used by the File-I/O protocol
35866 is defined as follows:
35870 time_t tv_sec; /* second */
35871 long tv_usec; /* microsecond */
35875 The integral datatypes conform to the definitions given in the
35876 appropriate section (see @ref{Integral Datatypes}, for details) so this
35877 structure is of size 8 bytes.
35880 @subsection Constants
35881 @cindex constants, in file-i/o protocol
35883 The following values are used for the constants inside of the
35884 protocol. @value{GDBN} and target are responsible for translating these
35885 values before and after the call as needed.
35896 @unnumberedsubsubsec Open Flags
35897 @cindex open flags, in file-i/o protocol
35899 All values are given in hexadecimal representation.
35911 @node mode_t Values
35912 @unnumberedsubsubsec mode_t Values
35913 @cindex mode_t values, in file-i/o protocol
35915 All values are given in octal representation.
35932 @unnumberedsubsubsec Errno Values
35933 @cindex errno values, in file-i/o protocol
35935 All values are given in decimal representation.
35960 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35961 any error value not in the list of supported error numbers.
35964 @unnumberedsubsubsec Lseek Flags
35965 @cindex lseek flags, in file-i/o protocol
35974 @unnumberedsubsubsec Limits
35975 @cindex limits, in file-i/o protocol
35977 All values are given in decimal representation.
35980 INT_MIN -2147483648
35982 UINT_MAX 4294967295
35983 LONG_MIN -9223372036854775808
35984 LONG_MAX 9223372036854775807
35985 ULONG_MAX 18446744073709551615
35988 @node File-I/O Examples
35989 @subsection File-I/O Examples
35990 @cindex file-i/o examples
35992 Example sequence of a write call, file descriptor 3, buffer is at target
35993 address 0x1234, 6 bytes should be written:
35996 <- @code{Fwrite,3,1234,6}
35997 @emph{request memory read from target}
36000 @emph{return "6 bytes written"}
36004 Example sequence of a read call, file descriptor 3, buffer is at target
36005 address 0x1234, 6 bytes should be read:
36008 <- @code{Fread,3,1234,6}
36009 @emph{request memory write to target}
36010 -> @code{X1234,6:XXXXXX}
36011 @emph{return "6 bytes read"}
36015 Example sequence of a read call, call fails on the host due to invalid
36016 file descriptor (@code{EBADF}):
36019 <- @code{Fread,3,1234,6}
36023 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
36027 <- @code{Fread,3,1234,6}
36032 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
36036 <- @code{Fread,3,1234,6}
36037 -> @code{X1234,6:XXXXXX}
36041 @node Library List Format
36042 @section Library List Format
36043 @cindex library list format, remote protocol
36045 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
36046 same process as your application to manage libraries. In this case,
36047 @value{GDBN} can use the loader's symbol table and normal memory
36048 operations to maintain a list of shared libraries. On other
36049 platforms, the operating system manages loaded libraries.
36050 @value{GDBN} can not retrieve the list of currently loaded libraries
36051 through memory operations, so it uses the @samp{qXfer:libraries:read}
36052 packet (@pxref{qXfer library list read}) instead. The remote stub
36053 queries the target's operating system and reports which libraries
36056 The @samp{qXfer:libraries:read} packet returns an XML document which
36057 lists loaded libraries and their offsets. Each library has an
36058 associated name and one or more segment or section base addresses,
36059 which report where the library was loaded in memory.
36061 For the common case of libraries that are fully linked binaries, the
36062 library should have a list of segments. If the target supports
36063 dynamic linking of a relocatable object file, its library XML element
36064 should instead include a list of allocated sections. The segment or
36065 section bases are start addresses, not relocation offsets; they do not
36066 depend on the library's link-time base addresses.
36068 @value{GDBN} must be linked with the Expat library to support XML
36069 library lists. @xref{Expat}.
36071 A simple memory map, with one loaded library relocated by a single
36072 offset, looks like this:
36076 <library name="/lib/libc.so.6">
36077 <segment address="0x10000000"/>
36082 Another simple memory map, with one loaded library with three
36083 allocated sections (.text, .data, .bss), looks like this:
36087 <library name="sharedlib.o">
36088 <section address="0x10000000"/>
36089 <section address="0x20000000"/>
36090 <section address="0x30000000"/>
36095 The format of a library list is described by this DTD:
36098 <!-- library-list: Root element with versioning -->
36099 <!ELEMENT library-list (library)*>
36100 <!ATTLIST library-list version CDATA #FIXED "1.0">
36101 <!ELEMENT library (segment*, section*)>
36102 <!ATTLIST library name CDATA #REQUIRED>
36103 <!ELEMENT segment EMPTY>
36104 <!ATTLIST segment address CDATA #REQUIRED>
36105 <!ELEMENT section EMPTY>
36106 <!ATTLIST section address CDATA #REQUIRED>
36109 In addition, segments and section descriptors cannot be mixed within a
36110 single library element, and you must supply at least one segment or
36111 section for each library.
36113 @node Memory Map Format
36114 @section Memory Map Format
36115 @cindex memory map format
36117 To be able to write into flash memory, @value{GDBN} needs to obtain a
36118 memory map from the target. This section describes the format of the
36121 The memory map is obtained using the @samp{qXfer:memory-map:read}
36122 (@pxref{qXfer memory map read}) packet and is an XML document that
36123 lists memory regions.
36125 @value{GDBN} must be linked with the Expat library to support XML
36126 memory maps. @xref{Expat}.
36128 The top-level structure of the document is shown below:
36131 <?xml version="1.0"?>
36132 <!DOCTYPE memory-map
36133 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36134 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36140 Each region can be either:
36145 A region of RAM starting at @var{addr} and extending for @var{length}
36149 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36154 A region of read-only memory:
36157 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36162 A region of flash memory, with erasure blocks @var{blocksize}
36166 <memory type="flash" start="@var{addr}" length="@var{length}">
36167 <property name="blocksize">@var{blocksize}</property>
36173 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36174 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36175 packets to write to addresses in such ranges.
36177 The formal DTD for memory map format is given below:
36180 <!-- ................................................... -->
36181 <!-- Memory Map XML DTD ................................ -->
36182 <!-- File: memory-map.dtd .............................. -->
36183 <!-- .................................... .............. -->
36184 <!-- memory-map.dtd -->
36185 <!-- memory-map: Root element with versioning -->
36186 <!ELEMENT memory-map (memory | property)>
36187 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36188 <!ELEMENT memory (property)>
36189 <!-- memory: Specifies a memory region,
36190 and its type, or device. -->
36191 <!ATTLIST memory type CDATA #REQUIRED
36192 start CDATA #REQUIRED
36193 length CDATA #REQUIRED
36194 device CDATA #IMPLIED>
36195 <!-- property: Generic attribute tag -->
36196 <!ELEMENT property (#PCDATA | property)*>
36197 <!ATTLIST property name CDATA #REQUIRED>
36200 @node Thread List Format
36201 @section Thread List Format
36202 @cindex thread list format
36204 To efficiently update the list of threads and their attributes,
36205 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36206 (@pxref{qXfer threads read}) and obtains the XML document with
36207 the following structure:
36210 <?xml version="1.0"?>
36212 <thread id="id" core="0">
36213 ... description ...
36218 Each @samp{thread} element must have the @samp{id} attribute that
36219 identifies the thread (@pxref{thread-id syntax}). The
36220 @samp{core} attribute, if present, specifies which processor core
36221 the thread was last executing on. The content of the of @samp{thread}
36222 element is interpreted as human-readable auxilliary information.
36224 @node Traceframe Info Format
36225 @section Traceframe Info Format
36226 @cindex traceframe info format
36228 To be able to know which objects in the inferior can be examined when
36229 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36230 memory ranges, registers and trace state variables that have been
36231 collected in a traceframe.
36233 This list is obtained using the @samp{qXfer:traceframe-info:read}
36234 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36236 @value{GDBN} must be linked with the Expat library to support XML
36237 traceframe info discovery. @xref{Expat}.
36239 The top-level structure of the document is shown below:
36242 <?xml version="1.0"?>
36243 <!DOCTYPE traceframe-info
36244 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36245 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36251 Each traceframe block can be either:
36256 A region of collected memory starting at @var{addr} and extending for
36257 @var{length} bytes from there:
36260 <memory start="@var{addr}" length="@var{length}"/>
36265 The formal DTD for the traceframe info format is given below:
36268 <!ELEMENT traceframe-info (memory)* >
36269 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36271 <!ELEMENT memory EMPTY>
36272 <!ATTLIST memory start CDATA #REQUIRED
36273 length CDATA #REQUIRED>
36276 @include agentexpr.texi
36278 @node Target Descriptions
36279 @appendix Target Descriptions
36280 @cindex target descriptions
36282 @strong{Warning:} target descriptions are still under active development,
36283 and the contents and format may change between @value{GDBN} releases.
36284 The format is expected to stabilize in the future.
36286 One of the challenges of using @value{GDBN} to debug embedded systems
36287 is that there are so many minor variants of each processor
36288 architecture in use. It is common practice for vendors to start with
36289 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36290 and then make changes to adapt it to a particular market niche. Some
36291 architectures have hundreds of variants, available from dozens of
36292 vendors. This leads to a number of problems:
36296 With so many different customized processors, it is difficult for
36297 the @value{GDBN} maintainers to keep up with the changes.
36299 Since individual variants may have short lifetimes or limited
36300 audiences, it may not be worthwhile to carry information about every
36301 variant in the @value{GDBN} source tree.
36303 When @value{GDBN} does support the architecture of the embedded system
36304 at hand, the task of finding the correct architecture name to give the
36305 @command{set architecture} command can be error-prone.
36308 To address these problems, the @value{GDBN} remote protocol allows a
36309 target system to not only identify itself to @value{GDBN}, but to
36310 actually describe its own features. This lets @value{GDBN} support
36311 processor variants it has never seen before --- to the extent that the
36312 descriptions are accurate, and that @value{GDBN} understands them.
36314 @value{GDBN} must be linked with the Expat library to support XML
36315 target descriptions. @xref{Expat}.
36318 * Retrieving Descriptions:: How descriptions are fetched from a target.
36319 * Target Description Format:: The contents of a target description.
36320 * Predefined Target Types:: Standard types available for target
36322 * Standard Target Features:: Features @value{GDBN} knows about.
36325 @node Retrieving Descriptions
36326 @section Retrieving Descriptions
36328 Target descriptions can be read from the target automatically, or
36329 specified by the user manually. The default behavior is to read the
36330 description from the target. @value{GDBN} retrieves it via the remote
36331 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36332 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36333 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36334 XML document, of the form described in @ref{Target Description
36337 Alternatively, you can specify a file to read for the target description.
36338 If a file is set, the target will not be queried. The commands to
36339 specify a file are:
36342 @cindex set tdesc filename
36343 @item set tdesc filename @var{path}
36344 Read the target description from @var{path}.
36346 @cindex unset tdesc filename
36347 @item unset tdesc filename
36348 Do not read the XML target description from a file. @value{GDBN}
36349 will use the description supplied by the current target.
36351 @cindex show tdesc filename
36352 @item show tdesc filename
36353 Show the filename to read for a target description, if any.
36357 @node Target Description Format
36358 @section Target Description Format
36359 @cindex target descriptions, XML format
36361 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36362 document which complies with the Document Type Definition provided in
36363 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36364 means you can use generally available tools like @command{xmllint} to
36365 check that your feature descriptions are well-formed and valid.
36366 However, to help people unfamiliar with XML write descriptions for
36367 their targets, we also describe the grammar here.
36369 Target descriptions can identify the architecture of the remote target
36370 and (for some architectures) provide information about custom register
36371 sets. They can also identify the OS ABI of the remote target.
36372 @value{GDBN} can use this information to autoconfigure for your
36373 target, or to warn you if you connect to an unsupported target.
36375 Here is a simple target description:
36378 <target version="1.0">
36379 <architecture>i386:x86-64</architecture>
36384 This minimal description only says that the target uses
36385 the x86-64 architecture.
36387 A target description has the following overall form, with [ ] marking
36388 optional elements and @dots{} marking repeatable elements. The elements
36389 are explained further below.
36392 <?xml version="1.0"?>
36393 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36394 <target version="1.0">
36395 @r{[}@var{architecture}@r{]}
36396 @r{[}@var{osabi}@r{]}
36397 @r{[}@var{compatible}@r{]}
36398 @r{[}@var{feature}@dots{}@r{]}
36403 The description is generally insensitive to whitespace and line
36404 breaks, under the usual common-sense rules. The XML version
36405 declaration and document type declaration can generally be omitted
36406 (@value{GDBN} does not require them), but specifying them may be
36407 useful for XML validation tools. The @samp{version} attribute for
36408 @samp{<target>} may also be omitted, but we recommend
36409 including it; if future versions of @value{GDBN} use an incompatible
36410 revision of @file{gdb-target.dtd}, they will detect and report
36411 the version mismatch.
36413 @subsection Inclusion
36414 @cindex target descriptions, inclusion
36417 @cindex <xi:include>
36420 It can sometimes be valuable to split a target description up into
36421 several different annexes, either for organizational purposes, or to
36422 share files between different possible target descriptions. You can
36423 divide a description into multiple files by replacing any element of
36424 the target description with an inclusion directive of the form:
36427 <xi:include href="@var{document}"/>
36431 When @value{GDBN} encounters an element of this form, it will retrieve
36432 the named XML @var{document}, and replace the inclusion directive with
36433 the contents of that document. If the current description was read
36434 using @samp{qXfer}, then so will be the included document;
36435 @var{document} will be interpreted as the name of an annex. If the
36436 current description was read from a file, @value{GDBN} will look for
36437 @var{document} as a file in the same directory where it found the
36438 original description.
36440 @subsection Architecture
36441 @cindex <architecture>
36443 An @samp{<architecture>} element has this form:
36446 <architecture>@var{arch}</architecture>
36449 @var{arch} is one of the architectures from the set accepted by
36450 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36453 @cindex @code{<osabi>}
36455 This optional field was introduced in @value{GDBN} version 7.0.
36456 Previous versions of @value{GDBN} ignore it.
36458 An @samp{<osabi>} element has this form:
36461 <osabi>@var{abi-name}</osabi>
36464 @var{abi-name} is an OS ABI name from the same selection accepted by
36465 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36467 @subsection Compatible Architecture
36468 @cindex @code{<compatible>}
36470 This optional field was introduced in @value{GDBN} version 7.0.
36471 Previous versions of @value{GDBN} ignore it.
36473 A @samp{<compatible>} element has this form:
36476 <compatible>@var{arch}</compatible>
36479 @var{arch} is one of the architectures from the set accepted by
36480 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36482 A @samp{<compatible>} element is used to specify that the target
36483 is able to run binaries in some other than the main target architecture
36484 given by the @samp{<architecture>} element. For example, on the
36485 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36486 or @code{powerpc:common64}, but the system is able to run binaries
36487 in the @code{spu} architecture as well. The way to describe this
36488 capability with @samp{<compatible>} is as follows:
36491 <architecture>powerpc:common</architecture>
36492 <compatible>spu</compatible>
36495 @subsection Features
36498 Each @samp{<feature>} describes some logical portion of the target
36499 system. Features are currently used to describe available CPU
36500 registers and the types of their contents. A @samp{<feature>} element
36504 <feature name="@var{name}">
36505 @r{[}@var{type}@dots{}@r{]}
36511 Each feature's name should be unique within the description. The name
36512 of a feature does not matter unless @value{GDBN} has some special
36513 knowledge of the contents of that feature; if it does, the feature
36514 should have its standard name. @xref{Standard Target Features}.
36518 Any register's value is a collection of bits which @value{GDBN} must
36519 interpret. The default interpretation is a two's complement integer,
36520 but other types can be requested by name in the register description.
36521 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36522 Target Types}), and the description can define additional composite types.
36524 Each type element must have an @samp{id} attribute, which gives
36525 a unique (within the containing @samp{<feature>}) name to the type.
36526 Types must be defined before they are used.
36529 Some targets offer vector registers, which can be treated as arrays
36530 of scalar elements. These types are written as @samp{<vector>} elements,
36531 specifying the array element type, @var{type}, and the number of elements,
36535 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36539 If a register's value is usefully viewed in multiple ways, define it
36540 with a union type containing the useful representations. The
36541 @samp{<union>} element contains one or more @samp{<field>} elements,
36542 each of which has a @var{name} and a @var{type}:
36545 <union id="@var{id}">
36546 <field name="@var{name}" type="@var{type}"/>
36552 If a register's value is composed from several separate values, define
36553 it with a structure type. There are two forms of the @samp{<struct>}
36554 element; a @samp{<struct>} element must either contain only bitfields
36555 or contain no bitfields. If the structure contains only bitfields,
36556 its total size in bytes must be specified, each bitfield must have an
36557 explicit start and end, and bitfields are automatically assigned an
36558 integer type. The field's @var{start} should be less than or
36559 equal to its @var{end}, and zero represents the least significant bit.
36562 <struct id="@var{id}" size="@var{size}">
36563 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36568 If the structure contains no bitfields, then each field has an
36569 explicit type, and no implicit padding is added.
36572 <struct id="@var{id}">
36573 <field name="@var{name}" type="@var{type}"/>
36579 If a register's value is a series of single-bit flags, define it with
36580 a flags type. The @samp{<flags>} element has an explicit @var{size}
36581 and contains one or more @samp{<field>} elements. Each field has a
36582 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36586 <flags id="@var{id}" size="@var{size}">
36587 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36592 @subsection Registers
36595 Each register is represented as an element with this form:
36598 <reg name="@var{name}"
36599 bitsize="@var{size}"
36600 @r{[}regnum="@var{num}"@r{]}
36601 @r{[}save-restore="@var{save-restore}"@r{]}
36602 @r{[}type="@var{type}"@r{]}
36603 @r{[}group="@var{group}"@r{]}/>
36607 The components are as follows:
36612 The register's name; it must be unique within the target description.
36615 The register's size, in bits.
36618 The register's number. If omitted, a register's number is one greater
36619 than that of the previous register (either in the current feature or in
36620 a preceeding feature); the first register in the target description
36621 defaults to zero. This register number is used to read or write
36622 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36623 packets, and registers appear in the @code{g} and @code{G} packets
36624 in order of increasing register number.
36627 Whether the register should be preserved across inferior function
36628 calls; this must be either @code{yes} or @code{no}. The default is
36629 @code{yes}, which is appropriate for most registers except for
36630 some system control registers; this is not related to the target's
36634 The type of the register. @var{type} may be a predefined type, a type
36635 defined in the current feature, or one of the special types @code{int}
36636 and @code{float}. @code{int} is an integer type of the correct size
36637 for @var{bitsize}, and @code{float} is a floating point type (in the
36638 architecture's normal floating point format) of the correct size for
36639 @var{bitsize}. The default is @code{int}.
36642 The register group to which this register belongs. @var{group} must
36643 be either @code{general}, @code{float}, or @code{vector}. If no
36644 @var{group} is specified, @value{GDBN} will not display the register
36645 in @code{info registers}.
36649 @node Predefined Target Types
36650 @section Predefined Target Types
36651 @cindex target descriptions, predefined types
36653 Type definitions in the self-description can build up composite types
36654 from basic building blocks, but can not define fundamental types. Instead,
36655 standard identifiers are provided by @value{GDBN} for the fundamental
36656 types. The currently supported types are:
36665 Signed integer types holding the specified number of bits.
36672 Unsigned integer types holding the specified number of bits.
36676 Pointers to unspecified code and data. The program counter and
36677 any dedicated return address register may be marked as code
36678 pointers; printing a code pointer converts it into a symbolic
36679 address. The stack pointer and any dedicated address registers
36680 may be marked as data pointers.
36683 Single precision IEEE floating point.
36686 Double precision IEEE floating point.
36689 The 12-byte extended precision format used by ARM FPA registers.
36692 The 10-byte extended precision format used by x87 registers.
36695 32bit @sc{eflags} register used by x86.
36698 32bit @sc{mxcsr} register used by x86.
36702 @node Standard Target Features
36703 @section Standard Target Features
36704 @cindex target descriptions, standard features
36706 A target description must contain either no registers or all the
36707 target's registers. If the description contains no registers, then
36708 @value{GDBN} will assume a default register layout, selected based on
36709 the architecture. If the description contains any registers, the
36710 default layout will not be used; the standard registers must be
36711 described in the target description, in such a way that @value{GDBN}
36712 can recognize them.
36714 This is accomplished by giving specific names to feature elements
36715 which contain standard registers. @value{GDBN} will look for features
36716 with those names and verify that they contain the expected registers;
36717 if any known feature is missing required registers, or if any required
36718 feature is missing, @value{GDBN} will reject the target
36719 description. You can add additional registers to any of the
36720 standard features --- @value{GDBN} will display them just as if
36721 they were added to an unrecognized feature.
36723 This section lists the known features and their expected contents.
36724 Sample XML documents for these features are included in the
36725 @value{GDBN} source tree, in the directory @file{gdb/features}.
36727 Names recognized by @value{GDBN} should include the name of the
36728 company or organization which selected the name, and the overall
36729 architecture to which the feature applies; so e.g.@: the feature
36730 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36732 The names of registers are not case sensitive for the purpose
36733 of recognizing standard features, but @value{GDBN} will only display
36734 registers using the capitalization used in the description.
36741 * PowerPC Features::
36746 @subsection ARM Features
36747 @cindex target descriptions, ARM features
36749 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36751 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36752 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36754 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36755 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36756 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36759 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36760 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36762 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36763 it should contain at least registers @samp{wR0} through @samp{wR15} and
36764 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36765 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36767 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36768 should contain at least registers @samp{d0} through @samp{d15}. If
36769 they are present, @samp{d16} through @samp{d31} should also be included.
36770 @value{GDBN} will synthesize the single-precision registers from
36771 halves of the double-precision registers.
36773 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36774 need to contain registers; it instructs @value{GDBN} to display the
36775 VFP double-precision registers as vectors and to synthesize the
36776 quad-precision registers from pairs of double-precision registers.
36777 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36778 be present and include 32 double-precision registers.
36780 @node i386 Features
36781 @subsection i386 Features
36782 @cindex target descriptions, i386 features
36784 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36785 targets. It should describe the following registers:
36789 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36791 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36793 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36794 @samp{fs}, @samp{gs}
36796 @samp{st0} through @samp{st7}
36798 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36799 @samp{foseg}, @samp{fooff} and @samp{fop}
36802 The register sets may be different, depending on the target.
36804 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36805 describe registers:
36809 @samp{xmm0} through @samp{xmm7} for i386
36811 @samp{xmm0} through @samp{xmm15} for amd64
36816 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36817 @samp{org.gnu.gdb.i386.sse} feature. It should
36818 describe the upper 128 bits of @sc{ymm} registers:
36822 @samp{ymm0h} through @samp{ymm7h} for i386
36824 @samp{ymm0h} through @samp{ymm15h} for amd64
36827 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36828 describe a single register, @samp{orig_eax}.
36830 @node MIPS Features
36831 @subsection MIPS Features
36832 @cindex target descriptions, MIPS features
36834 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36835 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36836 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36839 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36840 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36841 registers. They may be 32-bit or 64-bit depending on the target.
36843 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36844 it may be optional in a future version of @value{GDBN}. It should
36845 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36846 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36848 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36849 contain a single register, @samp{restart}, which is used by the
36850 Linux kernel to control restartable syscalls.
36852 @node M68K Features
36853 @subsection M68K Features
36854 @cindex target descriptions, M68K features
36857 @item @samp{org.gnu.gdb.m68k.core}
36858 @itemx @samp{org.gnu.gdb.coldfire.core}
36859 @itemx @samp{org.gnu.gdb.fido.core}
36860 One of those features must be always present.
36861 The feature that is present determines which flavor of m68k is
36862 used. The feature that is present should contain registers
36863 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36864 @samp{sp}, @samp{ps} and @samp{pc}.
36866 @item @samp{org.gnu.gdb.coldfire.fp}
36867 This feature is optional. If present, it should contain registers
36868 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36872 @node PowerPC Features
36873 @subsection PowerPC Features
36874 @cindex target descriptions, PowerPC features
36876 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36877 targets. It should contain registers @samp{r0} through @samp{r31},
36878 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36879 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36881 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36882 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36884 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36885 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36888 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36889 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36890 will combine these registers with the floating point registers
36891 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36892 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36893 through @samp{vs63}, the set of vector registers for POWER7.
36895 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36896 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36897 @samp{spefscr}. SPE targets should provide 32-bit registers in
36898 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36899 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36900 these to present registers @samp{ev0} through @samp{ev31} to the
36903 @node Operating System Information
36904 @appendix Operating System Information
36905 @cindex operating system information
36911 Users of @value{GDBN} often wish to obtain information about the state of
36912 the operating system running on the target---for example the list of
36913 processes, or the list of open files. This section describes the
36914 mechanism that makes it possible. This mechanism is similar to the
36915 target features mechanism (@pxref{Target Descriptions}), but focuses
36916 on a different aspect of target.
36918 Operating system information is retrived from the target via the
36919 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36920 read}). The object name in the request should be @samp{osdata}, and
36921 the @var{annex} identifies the data to be fetched.
36924 @appendixsection Process list
36925 @cindex operating system information, process list
36927 When requesting the process list, the @var{annex} field in the
36928 @samp{qXfer} request should be @samp{processes}. The returned data is
36929 an XML document. The formal syntax of this document is defined in
36930 @file{gdb/features/osdata.dtd}.
36932 An example document is:
36935 <?xml version="1.0"?>
36936 <!DOCTYPE target SYSTEM "osdata.dtd">
36937 <osdata type="processes">
36939 <column name="pid">1</column>
36940 <column name="user">root</column>
36941 <column name="command">/sbin/init</column>
36942 <column name="cores">1,2,3</column>
36947 Each item should include a column whose name is @samp{pid}. The value
36948 of that column should identify the process on the target. The
36949 @samp{user} and @samp{command} columns are optional, and will be
36950 displayed by @value{GDBN}. The @samp{cores} column, if present,
36951 should contain a comma-separated list of cores that this process
36952 is running on. Target may provide additional columns,
36953 which @value{GDBN} currently ignores.
36955 @node Trace File Format
36956 @appendix Trace File Format
36957 @cindex trace file format
36959 The trace file comes in three parts: a header, a textual description
36960 section, and a trace frame section with binary data.
36962 The header has the form @code{\x7fTRACE0\n}. The first byte is
36963 @code{0x7f} so as to indicate that the file contains binary data,
36964 while the @code{0} is a version number that may have different values
36967 The description section consists of multiple lines of @sc{ascii} text
36968 separated by newline characters (@code{0xa}). The lines may include a
36969 variety of optional descriptive or context-setting information, such
36970 as tracepoint definitions or register set size. @value{GDBN} will
36971 ignore any line that it does not recognize. An empty line marks the end
36974 @c FIXME add some specific types of data
36976 The trace frame section consists of a number of consecutive frames.
36977 Each frame begins with a two-byte tracepoint number, followed by a
36978 four-byte size giving the amount of data in the frame. The data in
36979 the frame consists of a number of blocks, each introduced by a
36980 character indicating its type (at least register, memory, and trace
36981 state variable). The data in this section is raw binary, not a
36982 hexadecimal or other encoding; its endianness matches the target's
36985 @c FIXME bi-arch may require endianness/arch info in description section
36988 @item R @var{bytes}
36989 Register block. The number and ordering of bytes matches that of a
36990 @code{g} packet in the remote protocol. Note that these are the
36991 actual bytes, in target order and @value{GDBN} register order, not a
36992 hexadecimal encoding.
36994 @item M @var{address} @var{length} @var{bytes}...
36995 Memory block. This is a contiguous block of memory, at the 8-byte
36996 address @var{address}, with a 2-byte length @var{length}, followed by
36997 @var{length} bytes.
36999 @item V @var{number} @var{value}
37000 Trace state variable block. This records the 8-byte signed value
37001 @var{value} of trace state variable numbered @var{number}.
37005 Future enhancements of the trace file format may include additional types
37008 @node Index Section Format
37009 @appendix @code{.gdb_index} section format
37010 @cindex .gdb_index section format
37011 @cindex index section format
37013 This section documents the index section that is created by @code{save
37014 gdb-index} (@pxref{Index Files}). The index section is
37015 DWARF-specific; some knowledge of DWARF is assumed in this
37018 The mapped index file format is designed to be directly
37019 @code{mmap}able on any architecture. In most cases, a datum is
37020 represented using a little-endian 32-bit integer value, called an
37021 @code{offset_type}. Big endian machines must byte-swap the values
37022 before using them. Exceptions to this rule are noted. The data is
37023 laid out such that alignment is always respected.
37025 A mapped index consists of several areas, laid out in order.
37029 The file header. This is a sequence of values, of @code{offset_type}
37030 unless otherwise noted:
37034 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
37035 Version 4 differs by its hashing function.
37038 The offset, from the start of the file, of the CU list.
37041 The offset, from the start of the file, of the types CU list. Note
37042 that this area can be empty, in which case this offset will be equal
37043 to the next offset.
37046 The offset, from the start of the file, of the address area.
37049 The offset, from the start of the file, of the symbol table.
37052 The offset, from the start of the file, of the constant pool.
37056 The CU list. This is a sequence of pairs of 64-bit little-endian
37057 values, sorted by the CU offset. The first element in each pair is
37058 the offset of a CU in the @code{.debug_info} section. The second
37059 element in each pair is the length of that CU. References to a CU
37060 elsewhere in the map are done using a CU index, which is just the
37061 0-based index into this table. Note that if there are type CUs, then
37062 conceptually CUs and type CUs form a single list for the purposes of
37066 The types CU list. This is a sequence of triplets of 64-bit
37067 little-endian values. In a triplet, the first value is the CU offset,
37068 the second value is the type offset in the CU, and the third value is
37069 the type signature. The types CU list is not sorted.
37072 The address area. The address area consists of a sequence of address
37073 entries. Each address entry has three elements:
37077 The low address. This is a 64-bit little-endian value.
37080 The high address. This is a 64-bit little-endian value. Like
37081 @code{DW_AT_high_pc}, the value is one byte beyond the end.
37084 The CU index. This is an @code{offset_type} value.
37088 The symbol table. This is an open-addressed hash table. The size of
37089 the hash table is always a power of 2.
37091 Each slot in the hash table consists of a pair of @code{offset_type}
37092 values. The first value is the offset of the symbol's name in the
37093 constant pool. The second value is the offset of the CU vector in the
37096 If both values are 0, then this slot in the hash table is empty. This
37097 is ok because while 0 is a valid constant pool index, it cannot be a
37098 valid index for both a string and a CU vector.
37100 The hash value for a table entry is computed by applying an
37101 iterative hash function to the symbol's name. Starting with an
37102 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37103 the string is incorporated into the hash using the formula depending on the
37108 The formula is @code{r = r * 67 + c - 113}.
37111 The formula is @code{r = r * 67 + tolower (c) - 113}.
37114 The terminating @samp{\0} is not incorporated into the hash.
37116 The step size used in the hash table is computed via
37117 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37118 value, and @samp{size} is the size of the hash table. The step size
37119 is used to find the next candidate slot when handling a hash
37122 The names of C@t{++} symbols in the hash table are canonicalized. We
37123 don't currently have a simple description of the canonicalization
37124 algorithm; if you intend to create new index sections, you must read
37128 The constant pool. This is simply a bunch of bytes. It is organized
37129 so that alignment is correct: CU vectors are stored first, followed by
37132 A CU vector in the constant pool is a sequence of @code{offset_type}
37133 values. The first value is the number of CU indices in the vector.
37134 Each subsequent value is the index of a CU in the CU list. This
37135 element in the hash table is used to indicate which CUs define the
37138 A string in the constant pool is zero-terminated.
37143 @node GNU Free Documentation License
37144 @appendix GNU Free Documentation License
37153 % I think something like @colophon should be in texinfo. In the
37155 \long\def\colophon{\hbox to0pt{}\vfill
37156 \centerline{The body of this manual is set in}
37157 \centerline{\fontname\tenrm,}
37158 \centerline{with headings in {\bf\fontname\tenbf}}
37159 \centerline{and examples in {\tt\fontname\tentt}.}
37160 \centerline{{\it\fontname\tenit\/},}
37161 \centerline{{\bf\fontname\tenbf}, and}
37162 \centerline{{\sl\fontname\tensl\/}}
37163 \centerline{are used for emphasis.}\vfill}
37165 % Blame: doc@cygnus.com, 1991.